Nghiên cứu khả năng hấp phụ cadmi và chì trong đất của bentonite và than bùn

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Bi Hi An

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: 60 85 02

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- 2010

i - 20

LI CM N

hon thnh lun vn ny, ti nhn c nhiu s gip nhit tnh

ca cc thy gio, gia nh, bn b v ng nghip. Nhn dp ny, ti xin by t li

cm n chn thnh v lng bit n su sc n PGS.TSKH Nguyn Xun Hi,

ngi thy hng dn tn tnh ch bo ti trong sut qu trnh hc tp v nghin

cu lun vn. Ti cng xin by t lng bit n n cc thy, c gio trong khoa Mi

trng tn tnh truyn t kin thc cho chng ti trong sut hai nm hc qua.

Ti xin gi li cm n su sc nht n cc ng nghip trong b mn Kinh

t s dng t v phn bn, cc ng nghip trong Vin Th nhng - Nng ha

tn tnh gip ti hon thnh lun vn.

Ti xin cm n s gip nhit tnh ca cc bn Nguyn Minh Phng v

Mai Th Thy Chung, b mn Khoa hc t - Khoa Mi trng, trng i hc

Khoa hc t nhin, v cc cn b Trung tm phn tch - Vin Quy hoch v thit k

nng nghip trong qu trnh thc hin ti.

Cui cng, ti xin by t lng bit n gia nh v bn b lun ng vin

v gip ti trong sut qu trnh tham gia kha hc cao hc ti trng i hc

Khoa hc t nhin - i hc Quc gia H Ni.

ii

DANH MC BNG

Trang

1.

.

2. -

).

Bng 3. nhim ch trong t tng mt (ppm).

4: /nm).

Bng 5. Hm lng Pb v Cd trong tng t mt ca mt s loi t.

Bng 6. c tnh lng Cd pht thi vo kh quyn t cc ngun Chu

u nm 1979.

7. .

Bng 8: Hm lng ch v cadmi in hnh trong cc sn phm s dng

trong sn xut nng nghip.

Bng 9. Hm lng Cd trong bn cng thi th.

Bng 10. Cc tnh cht l ha hc ch yu ca t nn.

Bng 11. Cc tnh cht l ha hc ch yu ca bentonite.

Bng 12. Tnh cht c bn ca than bn M c (H Ni).

Bng 13. Kt qu phn tch m, pH v CEC ca vt liu sau x l

14. Gi tr pH v CEC ca mu th nghim.

15. nh Pb2+ .

16. nh Cd2+ .

17. nh Pb2+ .

Bng 18. nh Cd2+ .

5

6

18

19

21

24

25

26

27

46

47

49

50

56

59

65

70

75

iii

DANH MC HNH

Trang

Hnh 1. ng ng nhit hp ph ca Pb2+, Zn2+ v Ni2+ ca Bentonite

hot ha Natri.

32

Hnh 2.

.

54

Hnh 3.

.

54

Hnh 4.

.

55

Hnh 5.

.

55

6. 2+ cc mu c b sung bentonite. 60

7. 2+ nh trong cc mu c b sung bentonite. 60

8. nh Pb2+

1 (Pbts = 130,81 ppm).

61

9. nh Pb2+

2 (Pbts = 211,66 ppm).

61

10. nh Pb2+

3 (Pbts = 599,04 ppm).

62

11. 2+ cc mu c b sung bentonite. 66

12. 2+ nh trong cc mu c b sung bentonite. 66

13. nh Cd2+

= 3,669 ppm).

67

14. nh Cd2+

iv

= 8,235 ppm). 67

15. nh Cd2+

= 14,593 ppm).

68

16. 2+ cc mu c b sung than bn. 71

17. 2+ nh trong cc mu c b sung than bn. 71

18. nh Pb2+

(Pbts = 130,81 ppm).

72

19. nh Pb2+

(Pbts = 211,66 ppm).

72

20. nh Pb2+

(Pbts = 599,04 ppm).

73

21. 2+ cc mu c b sung than bn. 76

22. 2+ nh trong cc mu c b sung than bn. 76

23. nh Cd2+

(Cdts = 3,669 ppm).

77

24. nh Cd2+

(Cdts = 8,235 ppm).

77

25. nh Cd2+

(Cdts = 14,593 ppm).

78

v

Trang

DANH MC BNG ................................................................................................. ii

DANH MC HNH ................................................................................................iii

............................................................................................................... v

M ................................................................................................................. 1

CHNG 1. TNG QUAN TI LIU..................................................................... 3

1.1. ng hc kim loi nng trong t - qu trnh hp ph ................................ 3

1.1.1. Phong ha m ................................................................................. 3

1.1.2. Ha tan kim loi nng t khong vt t ............................................. 4

1.1.3. Trao i ion, hp ph v ha hp th .................................................. 8

1.1.4. Yu t nh hng n hp ph kim loi trong t ............................. 13

1.1.5. Chelate ha v to phc vi cc hp cht hu c .............................. 16

1.2. Ngun gc v hm lng ca Cd v Pb trong t...................................... 17

1.2.1. Ngun t nhin v hm lng nn .................................................... 19

1.2.2. Khai m v luyn kim ....................................................................... 22

1.2.3. Lng ng t kh quyn v sn xut cng nghip .............................. 23

1.2.4. B sung vo t t sn xut nng nghip .......................................... 25

1.3. Tng quan v bentonite ............................................................................. 28

1.3.1. Cc tnh cht l - ha hc c bn ca bentonite ................................. 29

1.3.2. Kh nng hp ph ca bentonite ....................................................... 31

1.3.3. Phn b ca bentonite trn th gii v Vit Nam ............................ 33

1.4. Tng quan v than bn .............................................................................. 34

1.4.1. Cc kiu thnh to ca than bn Vit Nam ..................................... 34

1.4.2. c tnh l ha ca than bn ............................................................. 36

vi

1.4.3. S dng than bn .............................................................................. 37

CHNG II. I TNG, MC TIU, NI DUNG V PHNG PHP

NGHIN CU ...................................................................................................... 39

2.1. i tng v mc tiu nghin cu ............................................................. 39

2.1.1. Mc tiu nghin cu ......................................................................... 39

2.1.2. i tng nghin cu ....................................................................... 39

2.2. Ni dung nghin cu ................................................................................. 40

2.3. Phng php nghin cu ........................................................................... 41

2.3.1. Phng php thu thp ti liu ............................................................ 41

2.3.2. Phng php ly mu ngoi thc a ................................................ 41

2.3.3. Phng php trong phng th nghim. .............................................. 41

2.3.3. Phng php x l s liu. ................................................................ 44

CHNG 3. KT QU NGHIN CU V THO LUN .................................... 46

3.1. Cc tnh cht c bn ca t v vt liu hp ph....................................... 46

3.1.1. Cc tnh cht c bn ca t .............................................................. 46

3.1.2. Cc tnh cht c bn ca bentonite C nh ...................................... 47

3.1.3. Cc tnh cht c bn ca than bn. .................................................... 48

3.2. S thay i ca mt s tnh cht l, ha hc ca vt liu sau khi x l v

ca t khi c b sung bentonite v than bn. .............................................. 49

3.2.1. S thay i ca mt s tnh cht ca vt liu sau x l..49

3.2.2. Thay i tnh cht t sau khi b sung vt liu hp ph.50

3.3. Hiu qu c nh Pb2+ v Cd2+ c ............................. 57

3.3.1. Hiu qu c nh Pb2+ c ................................... 57

c nh Cd2+ .................................. 62

c nh Pb2+ 2+ ............................. 68

c nh Pb2+ .................................... 68

vii

c nh Cd2+ ................................... 73

.................................................................................. 79

........................................................................................................ 79

...................................................................................................... 80

TI LIU THAM KHO ........................................................................................ 81

PH LC

~ 1 ~

M

,

gia

.

ring. Nm 1975, Nikiforova v Smirnova ch ra rng khai m l ngu

lu thng cc cht nhim [dn theo 52]. Nhng chng ta c th xc

nh c t nht nm nhm chnh ca ngun gy nhim nhn to kim loi

nng vo h thng thc vt - t:

- Luyn qung v khai m,

- Sn xut cng nghip,

- Lng ng t khng kh,

- Hot ng nng nghip,

- b ph thi trn t.

Campbell (1983) [dn theo 52] so snh v ch ra lng kim loi nng t

ngun nhn to i vo khng kh ln hn khong 15 ln (vi Cd), 100 ln (vi Pb),

13 ln (vi Cu) v 21 ln (vi Zn) so vi ngun t nhin.

tri

-

.

~ 2 ~

.

-

. Trong cc vt liu c tim nng hp ph kim loi nng

trong t, bentonite v than bn l hai vt liu ng ch .

e Fe

- -

.

.

c nh .

S dng phng php dng vt liu hp ph lm gim nhim kim loi nng

trong t c u im ln v gi thnh v kh nng p dng vo thc tin cao, tuy

nhin cha c ph bin trong nc. Do , chng ti la chn ti Nghin

cu kh nng hp ph cadmi v ch trong t ca bentonite v than bn.

~ 3 ~

CHNG 1. TNG QUAN TI LIU

1.1. NG HC KIM LOI NNG TRONG T QU TRNH HP PH

Mc d ch chim hm lng nh trong t, cc kim loi nng ng vai tr

quan trng i vi ph nhiu ca t. Cc qu trnh bin i, di ng ca cc kim

loi nng trong t n nay vn cha c lm r v v c bn, y l nhng qu

trnh rt phc tp, bin i ty thuc vo nhiu yu t, t bn cht ca t n iu

kin kh hu, a hnh v cc hot ng nhn sinh. Phn ny cp n cc qu

trnh ca kim loi nng, c bit l Cd v Pb, trong t, trong qu trnh quan

trng nht l hp ph/phn hp ph, v cc yu t nh hng n cc qu trnh .

C nng bao gm:

( ,

t cc

khc

,

(iii) Ht thu kim loi nng ,

,

/phn ph -

hydr - ,

(vi) Chelate i ,

tri h e - .

Cc phn di y trnh by nhng ng lc chnh ca kim loi nng trong

t, c bit l vi Cd v Pb.

1.1.1. Phong ha m

trong c ngun gc

ch c hm l cc (

tan, hydrate , xy - )

1984 [46] ( xy )

~ 4 ~

l

(1984) [46] v (1978) [dn theo 52] .

1.1.2. Ha tan kim loi nng t khong vt t

1.1.2.1. -

i tro -

- tri

- cho t tr ln -

ln i khi ch -

1

- (1983) [49]

- , xy

.

Cc nh khoa hc ba phng php chng minh l thuyt cho rng

-

hot tnh

, Cd, Cu,

, 4 - 5 - , 1983)

[35] : Cd > Zn >> Cu > Pb khi pH

-

, nh H2CO3 (1989) [dn

theo 52]

, vn

- . T php

b - .

~ 5 ~

1

.

xy -

K

- - - -

Cao Zn Zn

Cu, Co, Ni,

Hg, Ag, Au

- -

Cu, Co, Ni, Hg,

Ag, Au

Cd Cd -

Pb Pb Pb -

-

Fe, Mn, Al, Sn,

Pt, Cr, Zr

-

Al, Sn, Pt, Cr

-

Al, Sn, Cr

Zn; Cu, Ni,

Hg, Ag, Au

Zn, Co, Cu,

Ni, Hg, Ag,

Au, Cd, Pb

: nswell (1983)[49]

, hydr - , - , sulphate e cadmi

, Lindsay (1979) [42] 3

22+

khi tng mt

> 7,5. Phosphate cadmi

Cd2+

t -

phate , Pb5(PO4)3Cl (chloropyromorphite),

2+ trong dung

, nh silicate, sulphate, carbonate - tan rt mnh (Lindsay,

1979) [42] 1 phn ph lc

Cd2+ 2+

phn ln vt u kh

nng - mnh hn

~ 6 ~

phate.

2

- trong n xy .

2 Cd v Pb -

)

-

Cd

Pb

Cd2+

, CdSO4, CdCl+

Pb2+

, Orga, PbSO4, PbHCO3

+

Cd2+

, CdCl+, CdSO4, CdHCO3

+

PbCO3, Pb(CO3)22+

, Pb(OH)-

N (1990)[29]

, nh humic, fulvic

1.1.2.2. nh hng ca th xy ha -

Mt s tn ti trong t nhiu trng thi xy ha,

trong , quan tr , Mn, Cr, Cu, As, Ag, Hg v Pb. Cn bng xy ha

kh trong t b chi phi bi pe (logarite m ca ho do) trong

dung dch t.

xy ha t thay i, t l ca cc dng xy ha / dng kh

cng thay i. V , nhng

khc nhau v trng thi xy ha xy - (nh

thm in t) th khong xy ha s b ha tan, v khong kh s b kt ta. Nu t

b xy ha th ngc l khi tn ti trong trng thi xy

ha cao t quan trng nht thng gp c nhiu trng

thi xy ha. Kh nng ca - mangan m vi thp hn l -

st, trc tip xy c xc tc cho cc qu trnh xy

i xy, c th ng vai tr quan tr m ha tan ca

nguyn t vi lng (Mc Bride, 1989) [44]. Co v Pb c th b xy y

trn b mt ca - mangan. McBride cng m t xy ha kh

~ 7 ~

lin quan n cc trng thi xy ha khc nhau ca Fe, nh s kh ca - st

s c mt c hu c.

Trong hu ht nhng chuyn ha khong xy ha kh, c phn ng xy ha

kh v pH ng vai tr quan trng trong ha tan c t. iu

c ngha rng c e v p . S ha tan/ phn ly

ca galena (PbS) trong kim sot bi pe + pH. , galena (PbS)

khng th hnh thnh ti pe + pH > 4,59 trong t - , v di gi tr xy -

ha tan ca Pb2+ s chu s kim sot ca phi ca

SO42-

hay bt k dng sul hu c trong t ng vai tr

quan trng trong nh - i nhm chc trong

cc phn t hu c c th lm cn bng nhng trng thi xy ha nht nh c

- y ra nhanh (McBride, 1989)

[44]. Nhiu chuy - .

din ra n

c ng c cht hu c d b , m cc c cht ny

khng n cc sinh vt .

Hai dng chnh ca chuyn ha ha hc c th lin quan ti s gim linh

ng v s sn c ca cc nguyn t vt d p n

trong t:

i, S hnh thnh sulfite

ii, S hnh thnh ca carbonate , - - vi

tan thp.

cy trng trong t ngp nc, ngi ta quan st c s thiu ht v

gim hp th c t ng s (1976);

Patrick (1977) [dn theo 52] cng c s gim ha tan v mc hp th

thp ca Cd trong t.

~ 8 ~

1.1.3. Trao i ion, hp ph v ha hp th

m t y ha tan c ch t, chng ta

phi hi phn tch c a pha rn v pha l ,

trao i lin quan ti th

hp ph trn b mt cc ht. C ch chuyn ri cc ion t dung dch bao gm trao

i ion b hu c hoc ha hp

th khng trao i cc b mt khong nh - , hydr - v Al - silicate v

a khong

u c gi cc cation kim loi bi l

(c l

trao i vo cc tng silicate.

2+, Cu

2+ 2+ phi c

i v . t khi tn ti lc ht tnh in mnh c

ng trao , cn nhiu c ch hp ph

, cc nghin cu v tnh linh ng c

t tch.

hu ht cc nghin cu v s

. McBride

(1989) [44] a ra ba dng chnh th hin s hnh thnh lin kt b m

- khong:

(i) c cao, c trng l - cho cc kim lo

cng s, 1976).

(ii) S a 2 ion H+ on M2+ p ph cng

s

(iii) S thay n tch b mt ca - a hp

ph , 1981).

~ 9 ~

K thut quang ph, c bit l ESR (cng hng i

m (UV) hp ph

trao i v hp ph ng nguyn t, g

: Cu2+

, Cd2+

, Zn2+, nhng ch cc cp ion hoc cc phc nh CuCl+, CuOH+,

ZnOH+ v ZnCl

+, dng thy phn nh Cu(OH)2 m ch cc ph

3 (Mattigod et al, 1979, 1981 [42]; McBride, 1989 [44]

mt hp ph, gm silica, Aluminosilicate v nh hnh

v Al hydr - b mt hp ph quan tr - Fe v Mn.

- v nh hnh ca Si, Al v Silicate ng hn so vi -

mt hp ph kim loi. Jenne (1977) [dn theo 52] nu gi

thit rng vai tr c bn c t cho - Fe v Mn v

nh hnh kt ta. Robert v Terce (1989) [dn theo 52] ng gel

hoc lp ph bn ngoi ca hp cht Fe, Al trn b m p ph

cation kim loi quan tr p ph t

l do s lng l , b mt hp ph v c ch lin kt.

McBride (1989) [44] c ch hp ph

- (1989) [dn theo 52] cp n

khi n gin ha c p ph.

1.1.3.1. Th t i lc c p ph.

xy

. Brummer (1986) [34]

:

xy dng ring

hnh vi.

~ 10 ~

cng s (1976) [dn theo 52] a ra

-

-

ng s

thp

cht ch

- -

-

.

(1989) [44] a ra nh trong ph lc7

lc 8. C ,

hai, nh hng n mc

ha tan cao .

1.1.3.2.

- -

(McBride, 1989) [44]

chng minh cho thc t l 2+ 2+

( Pb2+

( Cd2+

, Mg2+

).

3 [ 52].

~ 11 ~

. Christensen

(1984) [dn theo 51]

, din ra 95

-

cng s, 1981)

[43].

.

C sau

, vn tng mc

trong nghin cu v ht thu:

,

, v

.

.

- - ). Sposito (1983) [53]

:

, :

;

~ 12 ~

:

.

- glutamic2+

-

, 1978) [dn theo 52]

. (1986) [dn theo 52]

ca

- humic. phate e

- , 1982) [dn theo 52]

sulphate sphate

.

(1983)

[dn theo 34]

0,49 Ao

cho

-

(Gerth, 1985) [dn theo 52].

1.1.3.3.

Mt vn quan trng

~ 13 ~

h -

- (McBride, 1989) [44]

+. (1983) [34] gia tng

(1984) [dn theo 44] 2+ 2+

2+, nhng Pb2+

Cu2+

. McBride (1989) [44] a r

:

- ,

- ,

- ,

- ,

- e ha,

- - .

b trnh

bc qu trnh . Barrow (1989) [dn theo 52]

.

1.1.4. Yu t nh hng n hp ph kim loi trong t

C nhiu yu t nh hng n s hp ph kim loi. Ngoi tr cc yu t v

d t (khong st, - t, cht hu c), cc yu t chnh nh

hng n s hp ph kim loi l pH, nng a cc

~ 14 ~

cation kim lo , s c mt c

h .

Nhn chung, s a cc kim loi gi i pH gim. t ct

pha tht c thnh phn c gii nh hn t tht pha ct, cng cho thy s

thp hn tt c cc gi tr ca pH. S cnh tranh ca cc ion Co, Ni v Zn hn ch

hiu qu u hn Cr, Cu v Pb. Trong khi Christensen (1987) khng

gii thch c kt qu hin tng

trong loi t ny ch yu l do trao

- . Cn lu rng s cn

bng hp ph c thc hi

g dch t. Trong th nghim ca

Christensen (1984) [dn theo 52], thay i nng mui CaCl2 t 10-3M n 10-2M

dn n gim kh 5 n 6 ln do Ca cnh tranh v tr. Theo Shuman

(1979) [dn theo 52], nh hng ln c

dch m s .

- 3

. Farrah v Pickering (1977) [dn theo

52] cho rng s hp ph cnh tranh ca cc khong st l yu t chnh nh hng

n kh nng lin kt ca Cd. Tiller v Soon (1981) [dn theo 51] cng cho rng

hp ph c nh hng ln hn qu trnh kt ta i vi hm lng Cd trong dung

dch t trong khong pH thch hp. Khi pH vt gi tr 7,5, yu t kim sot

linh ng ca Cd trong t l ha tan ca CdCO3 v c th l c ca Cd3(PO4)2.

Ngoi pH, cc yu t khc cng c nh hng quan trng n dng tn ti ca Cd

trong t l cc b mt hp ph v gc hu c. John (1972) [dn theo 47] cho bit

h s nng lng hp ph Cd ca cht hu c cao hn so vi cc khong st. Mt

khc, Abd Elfattah v Wada [dn theo 47] ch ra rng - Fe, allophane v

~ 15 ~

imogolite c i lc hp ph chn lc vi Cd mnh nht. Hydr - ch chim vai tr

th yu trong t khi pH thp (< 5,5). S ht thu Cd trong t - chu nh hng

ln t cc hp cht trong pha lng.

ph lc 2 trong t

cng s (1990) [dn theo 52] :

2 -

.

xy 4 -

xy

-

.

Ca2+

2+, Zn

2+ 2+

. ng s (1988) [29

,

Sposito (1986) [dn theo 52]

.

+

-

- nu

~ 16 ~

-

.

1.1.5. Chelate ha v to phc vi cc hp cht hu c

)

-

. Senesi (1992)

[dn theo 29] :

- aliphatic , - amin, polyphenol.

.

-

.

chelate

tri e

c - kim

ca . Fran cng s

(1992) [dn theo 52] nh hng ny

~ 17 ~

- citrate

.

, chelate

, Piccolo (1989) [dn theo 52]

sung -

t

c -

-

: Pb > Cu

:

Cu > Pb >>> Cd , 1978) [dn theo 52].

;

.

1.2. NGUN GC V HM LNG CA CADMI V CH TRONG T

v Pb

im loi nng

, Cd 70 -

80 %. Theo Yost (1979) v Tjell (1981) [dn theo 47], trong

cc ngun b sung Cd nhn to vo t, c tnh 54 - 58 % t phn ln, 39 - 41 %

t lng ng t kh quyn v 2 - 5 % t ngun bn thi cng rnh.

Trong mi trng lc a, ch tn ti di hai dng: nguyn sinh v th sinh.

Ch nguyn sinh tham gia vo cu trc khong vt ngay t khi khong vt c

hnh thnh, ch th sinh l sn phm phn r ca cc nguyn t Uranium v

Thoranium. Ch tn ti kh lu trong t. Theo Tyler [dn theo 47], khong thi

gian cn thit gim 10 % hm lng ch tng s bng con ng ra tri l

~ 18 ~

khong 200 nm i vi t nhim v 90 nm i vi t c qun l. Kitagishi

v Yamane [dn theo 47] c tnh khong thi gian lng ch trong t gim i

mt na (thi gian bn phn hy) l vo khong 740 - 5.900 nm, ph thuc vo

loi t, lng nc vo t v s c mt ca cc cht hu c.

Bng 3. nhim ch trong t tng mt (ppm)

V tr v ngun nhim Dao ng hoc trung

bnh hm lng

Quc gia

Khu vc khai m c 51 - 21.546 Vng quc Anh

Khu khai m kim loi (khng st) 170 - 4.563

> 300

Vng quc Anh

c

Cng nghip luyn kim 500 - 6.500

53 - 2.100

3.074

1.612 - 3.640

M

Nht

c

Nga

Sn xut pin v khu ti ch 135.000

93 - 3.800

M

Ba Lan

Bn thi nng nghip 175 - 3.916

> 800

Vng quc Anh

c

t ven ng giao thng 960 - 7.000

132 - 397

114 - 885

M

Nht Bn

c

S dng vi 2.400 Ba Lan

Ngun: Kabata - Pendias (1991)[ 47]

Nm 1990, C quan Bo v mi trng M (EPA) thng k cc ngun

pht thi Pb ra mi trng, kt qu cho thy, cc hot ng cng nghip, s dng

xng pha ch, ngun thi t bi rc thi ra mi trng 2.200 tn ch/ nm, than

cung cp 778 tn v du m pht thi 50 tn/ nm (Wilber v cng s, 1992) [dn

theo 3]. Cc ngun gy nhim ch trong t tng mt nhiu quc gia c thng

k trong bng 3.

~ 19 ~

Trong bng 4 l thng k ca Nriagu v Pacyna (1988) [45] v ngun a Cd

vo t. Nriagu v Pacyna (1988) cng tnh ton rng nu tng lng Cd c pht

tn lin tc vo mt din tch t canh tc rng 16x1012 m2 th t l kim loi xm

nhp vo t hng nm s mc 1g Cd/ 1ha.

4 /nm)

Cd

) 0,23 - 4,45 (11,7)

0 - 2,2 (5,8)

0,9 - 7,8 (20,5)

1,5 - 13 (34,2)

2.2 - 8,4 (22,1)

0,77 - 2,15 (5,4)

5,6 - 38

).

Ngun: Nriagu v Pacyna (1988)[45]

1.2.1. Ngun t nhin v hm lng nn

Ngun b sung cc kim loi nng ni chung, Pb v Cd ni ring vo

mi trng t, nh trnh by trong phn m u, ch chim t l nh trong tng

lng kim loi nng trong t. Cc qu trnh chnh ca t nhin b sung kim loi

nng vo t bao gm: phong ha ti ch m, lng ng t tro bi ni la, v

phong ha di chuyn v lng ng theo dng chy.

1.2.1.1. Hm lng kim loi nng trong cc khong.

v thng c pht

thi trong qu trnh khai m km

0,3 ppm. nh sau:

trong siu baz nh serpentine: 0,12 ppm, trong cc baz nh basalt: 0,13 - 0,2

ppm, trong granite: 0,09 - 0,2 ppm, trong vi: 0,028 - 0,1 ppm, trong ct:

0,05 ppm, trong phin st: 0,2 ppm [2].

~ 20 ~

Khc vi Cadmi, ch l kim loi tng i ph bin trong t nhin vi

khong 84 khong vt cha Pb, trong quan trng nht l galena (PbS). Hm

lng trung bnh ca Pb trong lp v Tri t c tnh khong 15 ppm.

Trong cc magma, Pb ch yu tp trung trong khong vt felspat, tip

l nhng khong vt to sm mu m c bit l biotite. Pb c xu th tng dn

hm lng trong cc loi magma theo - ca , t siu baz n siu -

. Hm lng trung bnh ca Pb trong cc loi magma - v cc trm tch st

dao ng trong khong 10 - 40 ppm. Trong cc loi siu baz v cc trm tch

vi, con s ny nm trong khong 0,1 - 10 ppm.

1.2.1.2. Hm lng nn ca ch v cadmi trong t

Vi kho 0,06 - 1,1 ppm, h

. Mc d dng nh khng

c tng quan gia hm lng Cd v loi t, vn c th a ra hm lng t nhin

ca Cd trong mt s loi t nh trong bng 8. Trn bnh din th gii, hm lng

trung bnh ca Cd cao nht trong t Histosols (0,78 ppm) v thp nht trong t

podzols (0,37 ppm) [47]. iu ny c gii thch bng mi tng quan lng gia

hm lng Cd trong t vi t l cp ht st trong t.

Nhn chung, trong hu ht cc loi t, Cd u c hm lng chim di 1

ppm, ngoi tr nhng ni chu nh hng t cc ngun nhim hoc t pht trin

trn nhng loi cha hm lng Cd cao bt thng nh en. Theo Page

(1987) [dn theo 3], t hnh thnh trn phin st ti mt s vng California v

Monterey cha hm lng Cd ln n 22 ppm. Theo Marples v Thornson (1990)

[dn theo 3] th t pht trin trn phin thch st en c cha than Derbyshire

(Anh) cha hm lng Cd < 22 ppm.

Cc s liu thng k hm lng ch trong cc loi t nhiu quc gia trong

bng 5 cho thy con s ny dao ng t 3 - 189 ppm, gi tr trung bnh dao ng t

10 - 67 ppm. Hm lng Pb cao nht c tm thy an Mch, Nht Bn, Anh v

Ireland phn nh mc nhim ca nhng nc ny. Alloway v Davies (1994)

~ 21 ~

[dn theo 2] cho bit, lng ch trong t ph sa sng Ystwyth (x Wales, lin hip

vng quc Anh v Bc Ailen) t mc trung bnh 1.419 ppm, trong khi t khu

vc bn cnh cha hm lng ch khng vt qu 26 ppm.

Gough v cng s (1988) [dn theo 2] xc nhn hm lng ch trong cc

loi t Alaska thp, dao ng t 4 - 349 ppm nhng c n 90 % s mu c hm

lng khng vt qu 20 ppm, hm lng trung bnh l 12 ppm. Gi tr ny khu

vc khng c nhiu tc ng ca con ngi phn nh gi tr nn ca Pb trong a

phn cc loi t trn th gii c th khng vt qu 20 ppm. Do , hm lng Pb

trung bnh trong t tng mt mc th gii c th c tnh t 25 ppm.

Bng 5. Hm lng Pb v Cd trong tng t mt ca mt s loi t

Loi t Quc gia Hm lng Cd (ppm) Hm lng Pb (ppm)

Dao ng Trung bnh Dao ng Trung bnh

t podzols

v t ct

Rumani 0,2 - 2,7 0,9 5 - 41 19

M 0,08 - 0,47 0,21 10 - 70 17

Hong th

v t tht

Ba Lan 0,18 - 0,25 0,20 14 - 32 26

M - - 10 30 19

t tht pha

st

Rumani 0,5 - 1,6 0,9 14 - 33 21

M 0,13 - 0,55 0,27 10 - 70 22

t ph sa o 0,21 - 0,52 0,37 16 - 22 19

Anh 0,41 - 2 1,10 24 - 96 63

Ba Lan 0,24 - 0,36 0,30 12,5 - 48,5 39

t Gly Ba Lan 0,14 - 0,96 0,50 19,5 - 48,5 30

t rng M 0.5 - 1,5 0,73 10 - 50 20

Ngun: Kabata - Pendias (1991)[ 47]

Ti Vit Nam, nhm tc gi Quang H nh gi hm lng Pb, Cd, Cu

v Zn trong t nng nghip Vit Nam giai on 2002 - 2007 [16]. Kt qu cho

thy, t mn cha hm lng ch cao nht (44,7 ppm), tip l t phn (37,2

ppm), t ph sa v t (u mc 33,8 ppm), t xm (15,2 ppm) v t ct

~ 22 ~

bin (10,9 ppm). Nh vy, hm lng Pb trong t Vit Nam nhn chung cha t

n mc gy nhim (70 ppm theo QCVN 03:2008 [4]). i vi Cd,

2,72 ppm , vt tiu chun cho php (2 ppm theo

QCVN 03: 2008), [21]. Cc nhm t khc c

hm lng Cd nm trong ngng cho php. C th: t mn c hm lng Cd trung

bnh mc 1,18 ppm, t phn l 0,98 ppm, t ph sa l 0,79 ppm, t xm l 0,39

ppm v t ct bin l 0,27 ppm. Tt nhin, y l nhng con s trung bnh, cha

phn nh ht mc nhim cc b ch v cadmi trong t Vit Nam.

1.2.2. Khai m v luyn kim

Cng nghip khai m v luyn qung ch pht thi mt lng ln ch vo

khng kh v mi trng t (lng ng t kh quyn hoc theo ngun nc thi).

Colbourn v Thornton (1995) [dn theo 3] kho st vng t nm trong phm vi

100m quanh mt nh my luyn kim c min nam Peak (Derbyshire - Vng

quc Anh); kt qu cho thy hm lng ch trung bnh trong t l 30.090 ppm v

trong vng 100m mt thm t ra qung c, hm lng ch trung bnh l 19.400

ppm. Cuc kho st qun Madison, Missouri (USA), ni cng nghip khai m

xut hin t cui th k 18 v ko di hn 150 nm cho thy hm lng ch ln

nht trong t l 2.200 ppm nhng khong 95 % mu cha < 355 ppm [3].

Cadmi phide, ZnS,

sphalente, wientzite, ZnCO3. Cc m sielfhide c th cha ti 5 % Cd. Theo Kabata

- Pendias [47] 20.800

1997. C quan bo v mi trng M (EPA, 1979)

[dn theo 2] cho bit, ti cc vng t chu nh hng ca m Pb - Zn, hm lng

Cd ln n 450 ppm. Cairney (1987) [dn theo 2] nghin cu cc mu t trng c

chu nh hng ca cc m Pb - Zn nc Anh, kt qu cho thy hm lng Cd

trong t dao ng t 2 - 336 ppm.

~ 23 ~

1.2.3. Lng ng t kh quyn v sn xut cng nghip

Cc hot ng sn xut cng nghip pht thi ch c th k n nh: luyn

kim, sn xut c quy, h thng ng dn, sn xut sn, chi tr em, gm gia

dng v c bit l vic s dng xng pha ch trc y. Theo d on ca

Nriagu (1984) [dn theo 45], tng lng ch c s dng v khai thc trn ton th

gii l 240 triu tn/ nm. Padmanabhan P. Nair (2000) [dn theo 3] cho bit, tng

lng ch pht thi ra mi trng khng kh t cc l luyn qung trong sut thi

ch La M vo khong 5.000 - 10.000 tn; con s ny trong khong thi gian t

nm 500 - 1.500 sau Cng nguyn, vo khong 500 - 1.500 tn / nm. Cc l luyn

qung pht thi ch di dng ch yu l khong ch nh PbS, PbO, PbSO4 v

PbO.SO4.

Cng gn ng giao thng, tn d ch trong t cng cao v ch yu nm

trong lp t mt. Theo thi gian ch s lng ng vo t nhiu dng song lng

ln l theo ma. Theo Zimmema (1996) [dn theo 2] pH ca nc ma l yu t

nh hng ln n dng v hm lng ch lng ng. Theo c tnh ca cc nh

khoa hc Chu u, vo thi k cao im s dng xng pha ch, khong t nm

1970 - 1980, lng ch pht thi ra mi trng khng kh ln ti mc cao nht l

400.000 tn/nm. u th k 21, nh chng trnh thay th tetraethyl ch trong

xng, lng pht thi ch trong khng kh gim xung cn 100.000 tn/nm

(Padmanabhan P. Nair, 2000) [dn theo 3]. Ch pht thi t ngun xng xe ch yu

di dng cc mui halide ch (nh PbBr, Pb(OH)Br, PbBrCl, v (PbO)2PbBr2).

Cc phn t ch khng bn vng v d dng chuyn sang dng - , carbonate, v

sulfate.

Nghin cu v mi tng quan gia Pb tng s v mt s tnh cht l ha

ca t ph sa sng Hng, Phm Quang H v Thu H [6] kt lun, theo TCN

10 796: 2006 (quy nh gii hn cho php hm lng Pb trong t ph sa phc v

sn xut nng nghip l 60 ppm) th c 13,64 % s mu nghin cu (trong tng s

44 mu 8 tnh) b nhim ch. ng thi cc tc gi cng a ra cnh bo v

s nhim bn ca t ph sa sng Hng, c bit l nhng ni c nguy c cao nh

~ 24 ~

gn lng ngh ti ch kim loi lin quan n ch, s dng nhiu phn bn, nc thi,

thuc bo v thc vt c cha Pb.

Cadmi c s dng trong nhiu ngnh cng nghip. Theo Aylett (1979)

[dn theo 3], cadmi c dng vo cc cng vic sau: lm lp xi m bo v cho

km, trong cc hp kim khc nhau, trong cht mu (cho cc cht nha, men,

gm), to cht lm chc cho cht do PVC, trong t bo pin kh Ni - Cd, trong v

kh qun dng, trong cc hp cht khc nh cht bn dn, b phn kim sot l

phn ng ht nhn. Cadmi c s dng nhiu trong vt liu cm quang ca cc t

bo quang in, trong mn hnh mu, mn hnh Plasma.... Cadmi

nhim kh quyn t nhng khu cng nghip v luyn kim, do

.... Mi

tn than c t cng thi vo kh quyn mt lng Cadmi l 2g, tng ng

vi 0,5 g/m3 khng kh.

Bng 6. c tnh lng Cd pht thi vo kh quyn t cc ngun Chu u

nm 1979.

Ngun Cd (T/ha)

S ch kim loi (khng st) 1631,4

t than 143,7

t du 108,2

Thiu hy cht thi 83,6

Ch to st thp 5,9

ng dng kim loi trong sn xut cng nghip 19,7

Ngun: Pacyna (1987) [dn theo 45].

5.

1 - 6 mg/m3

3,6 - 20 mg/m3

16,5 - 54 mg/m3

.

Sposito v Page (1984) [dn theo 3] c tnh s gia tng tch ly Cd trong tng t

~ 25 ~

mt M do lng ng kh quyn l < 0,089 ppm / nm vng nng thn, 0,029

ppm / nm khu cng nghip v 0,98 ppm / nm trung tm th. Nriagu [dn

theo 44] 5.

2. . Shacklett v cc ng s

(1973) nghin cu t ven ng cao tc M ghi nhn hm lng Cd t t 1 -

10 ppm [dn theo 3].

[28]

- - - - -

7).

7

(ppm)

LN-Al LN-Fe, Al, Cu LN-Pb LN-Cu, Zn

0,48 0,56 1,39 1,52 1,85

1,11 0,81 1,62 1,89 2,11

0,82 0,72 1,51 1,72 1,94

Ngun: Nguyn Cng Vinh v cng s [28]

[1]

(Vn Lm -

200 m quanh khu l 0,3 - 1 ppm

2 ppm

3,85 ppm.

1.2.4. B sung vo t t sn xut nng nghip

v Pb . Hot ng sn xut nng nghip nh s

dng phn bn, bn thi, trm tch sng h v cc ngun nc thi nhim ch lm

nc ti l ngun gy nhim ng k.

~ 26 ~

Phn bn gp phn ng k trong vic tch ly ch trong t v nh hng

trn din rng. Trong cc loi phn bn c a vo t th phn phosphate

thng c nhiu ch nht. Theo nh gi hm lng ch trong phn ha hc

Valencia (Ty Ban Nha), sulfate ng v sulfate st c hm lng ch cao, c tnh

khong 225 ppm (Alloway v cng s, 1998) [29].

Nriag 7

. Theo Cng ng chu u,

gi tr ny l khong 300 tn.

3 - 8 ppm 2

.

i vi khu vc nng tri, hm lng cho php ca Cd trong phn chung

theo Kabata - Pendias [46] v McGrath (1984) [dn theo 3] l 0,3 - 1,8 ppm. Trong

bng 8 l hm lng ch v cadmi in hnh trong mt s ch phm s dng trong

nng nghip trn th gii.

Bng 8: Hm lng ch v cadmi in hnh trong cc sn phm s dng

trong sn xut nng nghip

STT Sn phm Ch (ppm) Cadmi (ppm)

1 Thuc 11 - 16

2 Nc ti < 20 < 0,05

3 Nc thi 2 - 7.000 2 - 1.500 b

4 Vi 20 - 1.250 0,04 - 0,1

5 Phn phosphate 4 - 1.000 0,1 - 190 (0,1-170 b

)

6 Phn nitrate 2 - 120 0,05 - 8,5

7 Bn thi 2 - 7.000 < 1 - 3.410

8 Ph thi compost 1.3 - 2.240 0,01 - 100

9 Phn chung 0.4 - 16 0,1 - 0,8 (0,03 - 0,8 b)

(1990) [29], b: Nguyn Xun Hi (1996)[9]

~ 27 ~

Bn c nhiu nc trn th gii s dng nh mt loi phn bn hu ch b

sung cho t nng nghip. Tuy nhin, trong bn thi, nht l cc bn thi xut pht

t ngun sinh hot th v sn xut cng nghip, c cha mt lng kim loi nng

ng k. Do , y cng l ngun gy nhim ln cho t, nht l cc nc

cng nghip pht trin. Ty thuc vo ngun pht sinh, thnh phn v tnh cht ca

bn thi c s khc bit rt ln gia cc nc, cc khu vc. Nhng c th nh gi

chung, trong mt, hai thp k qua, lng Cd tch ly trong bn thi gim ng

k. y l kt qu ca qu trnh ci thin vic x l cht thi c v mt k thut v

qun l trn th gii. c nhiu nghin cu nh gi tnh cht ca bn thi v

mc gy nhim ca n cho t nng nghip.

, Cd t bonate (49 %).

Theo Sommers, 16 ppm

17 - 23 ppm

21 g/ha. Trn

3 g/ha. Baker (1974) v ORiordan

(1986) cho bit, Cd c tch ly trong bn thi vi hm lng dao ng rt ln, t

< 1 - 3.650 ppm [dn theo 5].

Bng 9. Hm lng Cd trong bn cng thi th

Cd (ppm) Ngun bn cng rnh S liu tham kho

6,8 - 444 16 thnh ph (M) 41

2,0 - 1100 57 vng Michigan 43

0,3 - 168 6 khu ph H Lan 44

< 1 - 180 200 mu bn Anh 46

0,3 - 236 7 thnh ph (Ontario, Canada) 51

1,9 - 35 TP H Ch Minh (Vit Nam) 6

10 - 12 Helsinky (Phn Lan) 49

Ngun: L Huy B (2000)[3]

~ 28 ~

Ch trong bn thi cng rt cao, khong 13 - 26.000 ppm cht kh v trung

bnh l 500 ppm cht kh (Logan, 1990) [dn theo 47]. Trong bn thi, ch c th

tn ti di nhiu dng khc nhau: ion t do, carbonate v c dng phc hu c tan

v khng tan. Theo Stover v cng s (1996) [dn theo 2], dng tn ti ch yu ca

ch trong bn thi l hp cht carbonate (xp x 61 %), dng di ng v d tiu vi

thc vt ch chim mt lng nh (< 17 %). Hu ht cc tc gi u cho rng lp

t mt c bn bn thi c s tch ly ch ng k, trong khi cy trng ch hp

thu c khong 0,06 % lng ch (McGrath, 1987) [dn theo 5]. Berrow v

Webber (1993) [dn theo 47] phn tch 42 mu bn t cc thnh ph cng nghip

Anh v Wales cho thy, hm lng ch trong khong 120 - 3.000 ppm (trung bnh

820 ppm) khi lng kh. Sommers (1990) [dn theo 3] cho bit, trong bn cng

Indiana (M), hm lng ch khong 547 - 7.431 ppm.

1.3. TNG QUAN V BENTONITE

Trn quan im a cht hc, bentonite l khong vt c hnh thnh ch

yu t s kt hp ca cc khong dng keo v nha vi thnh phn ch yu l

montmorillonite, khong st thuc nhm smectite. Bentonite hnh thnh t qu trnh

phn thy tinh ha ti ch ca tro bi ni la (Parker, 1988) [ dn theo 55]. S

chuyn ha ny din ra trong mi trng nc (thng l nc bin, hoc h nc

mn; i khi trong cc thy vc nc ngt khc). Ngoi montmorillonite, bentonite

cn c th cha feldspar, biotite, kaolinite, illite, cristobalite, pyroxene, km, v cc

ht quartz tinh th (Parkes, 1982) [dn theo 55].

Bentonite c khai thc v s dng nhiu trong nhiu lnh vc. Trong cng

nghip du kh, bentonite c dng trong hn hp dung dch khoan nhm mc

ch bi trn trc khoan v gi cho du v kh khi tht thot. Trong sn xut cng

nghip, ngi ta phn bit hai dng bentonite: Ca-bentonite v Na-bentonite. Do

tnh cht trng n rt tt ca n, Na-bentonite thng c s dng trong hn hp

khoan trong cng nghip du kh. Trong khi , Ca-bentonite thng c dng

nh mt cht hp th kim loi nng trong dung dch.

~ 29 ~

1.3.1. Cc tnh cht l - ha hc c bn ca bentonite

Bentonite l mt t hp cc khong nn khng th a ra mt cng thc

phn t no biu din thnh phn ha hc ca n. Phn di l cu trc ha hc

ca khong vt chnh trong bentonite: monmorillonite.

1.3.1.1. Cu trc ha hc ca monmorillonite

Montmorillonite l khong st thuc lp smectite. Cu trc tinh th c bn

ca smectite l mt lp bt din alumina nm gia hai lp t din silica [22]. Mi

lp cu trc ny c chiu dy 9,6 Ao. Trong cu trc ny, cc phn t xy trong hai

lp ln cn c xp lin nhau. Cch sp xp ny to ra mt lin kt yu, cho php

nc v cc phn t phn cc khc i vo khong khng gia cc lp, gy ra hin

tng trng n ca cu trc khong vt, khi tnh c lp nc hp ph v lp cation

trao i chiu dy ca khong c th ln n 15 Ao.

Di knh hin vi in t s quan st c montmorillonite di dng cc

kt tp khng u ca cc phn t nh hoc cc m lc gic, hoc him hn l cc

thanh mng (Grim, 1968) [dn theo 55]. S khc nhau trong cc nguyn t thay th

ng hnh nh hng, v trong vi trng hp, kim sot hnh thi ca

montmorillonite.

Trong lin kt ca th t din, silic c th b thay th bng nhm hoc pht-

pho. Trong th bt din, nhm c th b thay th bi magie, st, lithi, chrom, km

hoc niken. iu ny to ra hng lot cc dng khong montmorillonite ph nh

nontronite, saponite, hectorite, sauconite, beidellite, volkhonskoite, pomelite v

griffithite. Cng thc phn t ca monmorillonite thng c a ra di dng:

(M+

x.nH2O)(Al2 - yMgx)Si4O10(OH)2, trong M+ c th l Na+, K+, Mg2+ hoc Ca2+

(Brindley v Brown, 1980) [dn theo 55]. Mt cch l tng, x = 0,33.

1.3.1.2. Kh nng trao i cation

Silic trong tinh th montmorillonite c thay th bi cc cation dn n s

d tha in tch m trong mng li, vn cn bng in tch, do cc cation Na+,

K+, Mg

2+, Ca

2+ trong phn khng gian gia cc lp. Cc cation ny c th trao i

~ 30 ~

do lin kt lng lo ca chng v do cc lin kt b t gy (l do ny chim khong

20 % kh nng trao i cation); do montmorillonite c kh nng trao i cation

kh cao (khong 100 meq/100 g). Kh nng trao i cation ny cho php

montmorillonite lin kt vi c cc cation v c nh caesium ln cc cation hu c

nh thuc dit c di nc, cc loi thuc dit c mnh (Weber v cng s, 1965),

v triazine (Weber, 1970), v thm ch l c cc phn t hu c sinh hc nh rheo-

virus (Lipson v Stotzky, 1983), v protein (Potter v Stollerman, 1961)[33].

Breen v cng s (1999) [33] nghin cu kh nng trao i ca cc cp

Na/Pb, Na/Cd v Pb/Cd trong bentonite c lng kim loi thp vi s c mt ca

cc ion H+ cnh tranh. Kt qu cho thy s hp ph Cd2+ v Pb2+ ca bentonite - Na

gim khi nng ion H+ trong dung dch tng vi cc gi tr CEC tng ng.

Cd2+

khng b cnh tranh mnh vi H+ so vi Pb2+

1.3.1.3. Kh nng trng n v cc tnh cht vt l khc

Nc nm trong cu trc mng li khong vt l mt nhn t chnh kim

sot cc tnh cht ca cc khong thuc nhm montmorillonite nh tnh do, lin

kt, cht, th vn v cc tnh cht khc. Cc tnh cht vt l ca bentonite chu

nh hng ca vic liu montmorillonite trong thnh phn ca n cha cc lp

nc vi dy khng i hoc n l mt hn hp cc hydrate vi cc lp nc

thay i v dy.

Nc hp ph nm gia cc lp silicate bay hi nhit tng i thp

(100 - 200oC), nc cu to (nh hydroxyl) bt u bay hi nhit t 450 -

500oC v bay hi hon ton nhit t 600 - 750oC. nhit 800 - 900oC,

mng li tinh th b ph v, to ra hng lot dng khong th sinh nh mullite,

cristobale, v cordierite, ty thuc vo cu trc v thnh phn ca khong ban u.

Kh nng ht nc v trng n ca montmorillonite gim mnh khi nhit tng

cao, trong khong t 105 - 390oC, ty thuc vo lng cation trao i trong thnh

phn khong. Kh nng ht nc ca montmorillonite quyt nh gi tr s dng v

thng mi ca bentonite (Grim, 1968; Parker, 1988) [dn theo 55].

~ 31 ~

1.3.2. Kh nng hp ph ca Bentonite

Kh nng hp ph ca bentonite ni bt so vi cc khong khc. Bentonite

hp ph cc cht khng ch trong khong khng gian gia hai lp t din v bt

din trong cu trc tinh th ca montmorillonite m c b mt ngoi v cc cnh

ca cu trc ny. Montmorillonite (khong vt chnh trong thnh phn bentonite)

hp ph cc ion kim loi theo hai c ch ring bit: i) phn ng trao i ion ti cc

v tr tch in vnh vin v ii) to phc vi b mt cc nhm hydroxyl.

c nhiu nghin cu v s hp ph Pb2+ v Cd2+ trong dung dch ca

bentonite. Cc cng trnh nghin cu ny s dng m hnh ng nhit Langmuir v

cc phng trnh ng nhit khc tnh lng hp ph kim loi nng ca bentonite

v cc hp cht thuc dng bentonite qua x l. E.Eren v cng s (2009) [36]

tnh c kh nng hp ph Pb2+ ca bentonite th (ngun t Th Nh K) trong

dung dch 0,1M KNO3 l 16,70 mg/g, bentonite hot ha bng - l 8,92 v

bentonite c lp ph MgO l 58,88 (mg/g). Khng s dng dung dch KNO3, cc s

liu tng ng l 64,29; 40,14 v 123,64 (mg/g). Eren cng a ra kt lun rng s

hp ph Pb2+ ca bentonite chu tc ng ca pH, cng ion ha v s c mt

ca Cl- v ph thuc vo bn cht ca b mt hp ph v dng ca Pb2+ trong dung

dch (vn ph thuc vo pH ca h).

F.Ayari v cc cng s (2005) [32] nghin cu tnh cht v kh nng hp ph

Pb2+

, Zn2+

v Ni2+

trong cc dung dch nng ln lt l 10-3, 5x10-3 v 10-2 M ca

bentonite th v bentonite c hot ha Na vi bentonite khai thc vng

Zaghouan (Tunisia); kt qu cho thy bentonite hot ha c kh nng hp ph cao

hn bentonite th v lng hp ph Pb2+ l ln nht. ng ng nhit hp ph

c th hin hnh 1. Trong , Qeds l dung tch hp ph ca bentonite v Ceq l

nng cn bng ca dung dch.

Pradas v cng s [dn theo 32] nghin cu s hp ph Pb2+ v Cd2+ trn

bentonite trong iu kin c un trong dung dch H2SO4 0,5 M hoc 2,5 M trong

1 gi. Kt qu cho thy trong iu kin , hm lng cc ion trong th bt din

gim mnh, ko theo CEC v kh nng ra tri kim loi ca - cng gim theo.

~ 32 ~

Tuy nhin, Pradas bo co rng hm lng Cd2+ b hp ph gim t 15 mg/g pH =

7,9 xung 3 mg/g pH = 3,5; trong khi lng ht thu Pb2+ gim t 4 xung 2 mg/g

cng iu kin pH. Cc tc gi ny khng gii thch l do lng Cd2+ hp ph ti

pH = 7,9 cao hn rt nhiu so vi Pb2+.

Hnh 1. ng ng nhit hp ph ca Pb2+, Zn2+ v Ni2+ ca Bentonite

hot ha Na [32]

Ti Vit Nam, nghin cu kh nng hp ph kim loi ca bentonite mi ch

bc u. Nguyn Th i Tr (2004) [23] nghin cu s gim hm lng di ng

ca kim loi nng trong t v hm lng kim loi nng c cy hp ph sau khi

bn bentonite. Kt qu cho thy hm lng As, Pb, Cd d tiu trong t c x l

bentonite gim r rt. C th, mc bn bentonite 4,5 g/kg t hm lng kim loi

nng theo tnh ton gim so vi i chng theo th t As, Cd, Pb l 15,2 %; 8,8 %

v 31,3 % v mc bn bentonite 6,75 g/kg t l As, Cd v Pb ln lt l 43,5 %;

24,0 % v 38,9 %.

~ 33 ~

1.3.3. Phn b ca bentonite trn th gii v Vit Nam

Bentonite l khong cht phn b rng ri trn ton th gii. Ti nhiu a

im, chng to thnh m khong v c khai thc phc v cho sn xut cng

nghip v cc mc ch dn sinh khc.

Vit Nam l nc c tr lng bentonite kh ln, t mc khong 70 triu

tn, trong tr lng a cht cp 1 v 2 l 7,961 triu tn [25]. Vin a cht v

khong sn Vit Nam nh gi tr lng bentonite c th khai thc cng nghip vi

sn lng 20.000 - 24.000 tn / nm trong khong thi gian 15 nm (Nguyn Vit

Lc, 1998). Bentonite nc ta tp trung ch yu ti cc m C nh (Thanh

Ha), Tam B, L (Lm ng), Nha M (Bnh Thun) v B Ra - Vng Tu.

Vic ng dng bentonite Vit Nam cng mi ch dng li mt s lnh vc cng

nghip nh lm dung dch khoan, khun c, ty, lc, m phm Trong thc t

mi ch c hai m c khai thc cha lu v s lng cha ln. l m Tam B

(Di Linh - Lm ng) v C nh (Triu Sn - Thanh Ha)

M st Di Linh c tr lng khong 4,2 triu tn, trn mt din tch khong

2,4 km2 trn cao nguyn Di Linh (Lm ng). Bentonite Di Linh thuc nhm Ca-

bentonite c hm lng Ca khong 35 - 40 %, h s trng n thp. M st ny

c cng ty c phn Hip Thnh khai thc vi sn lng khong 15.000 - 18.000

m3 / nm bn cho cng ty dung dch khoan du kh (DMC) sn xut dung dch

khoan my.

M bentonite C nh l mt bi thi st phi kim bentonite sau qu trnh

khai thc, tuyn ra v lm giu qung kim loi Chromite, nm di chn ni Na

trn mt din tch khong 10 km2. Tr lng bentonite y khong 1,7 triu tn

nhng hng nm khai thc khng n nh bng phng php th cng, nm cao

nht ch c sn lng khong vi trm tn. Ngun bentonite ny ch yu cung cp

cho ngnh luyn kim, gm s, khoan my [11].

~ 34 ~

1.4. TNG QUAN V THAN BN

Than bn c hnh thnh do s tch t v phn hu khng hon ton tn d

thc vt trong iu kin ym kh xy ra lin tc.

Qu trnh ny din ra ti cc vng trng ngp nc. Cc vng t ngp nc

l nhng vng c nng sut sinh hc cao, iu kin pht trin ca thc vt rt thun

li. Tuy nhin, lp th nhng ti cc vng ny lun trong iu kin ym kh; do

, mc d sinh khi cc loi c sng trn mt nc tng nhanh, nhng qu trnh

phn gii xc thc vt li xy ra chm v khng t ti giai on v c ho dn n

tch lu hu c. Tip theo c l lau, lch, cy bi, cy thn g thay th, kt hp vi

qu trnh kin to a cht, qu trnh bi t, lng ng ph sa chn vi k c cy

thn g, lm cho hu c tch t thnh cc lp v to thnh than bn.

Tng din tch than bn th gii khong 400 - 500 triu ha vi tr lng

khong 400 - 800 t tn. Than bn tp trung nhiu vng n i, trong Lin

X(c) chim 60 %, Phn Lan 12 %, Canada 9 %, M 5 %.... Ngoi ra than bn cn

xut hin ri rc vng nhit i, thng phn b dc cc khu vc ngp mn, ven

bin [26].

n nay theo cc ti liu a cht , nc ta c 179 m v im

c nghin cu. Tng tr lng a cht trong phm vi ton quc l 738.337.775

m3. Trong c 2 m ln c tr lng mi m > 50 triu m3, u min Nam; 4

m va c tr lng mi m 10 - 50 triu m3 cng ch c min Nam; 162 m nh,

tr lng mi m 20.000 -10 triu m3, trong min Nam c 128 m, min Bc c

34 m. Ngoi ra trong phm vi c nc c 11 im qung, mi im qung c tr

lng < 20.000 m3, trong min Bc c 6 im v min Nam c 5 im.

1.4.1. Cc kiu thnh to ca than bn Vit Nam

Than bn Vit Nam c cc kiu thnh to sau [19]:

1.4.1.1. Thnh to m ly

Thnh to m ly c nhiu kiu:

~ 35 ~

- Kiu m ly gia ni: Cc m ly c thnh to do qu trnh ly ha

cc ngn sng, hnh thnh cc min c lng sng phng, rng. Cc m ny

thng c din tch phn b hp, quy m nh, chiu dy nh thng 0,5 - 3,0 m.

Lt ct dc a cht ca kiu m ly ny thng phn thnh hai lp. Lp trn l

than bn, y thng c thn, cnh, l mc nt phn hy trung bnh. Lp di l

st bt cha mn thc vt mu xm nht.

- Kiu m ly ven sng h (m ly mng nga): Cc m ly c hnh

thnh trong cc m ly ven sng do cc sng qua qu trnh xm thc bc mn,

cc h mng nga c tch t u b m ly ha, pht trin thc vt b bi lp m

thnh. Loi ny c quy m nh.

- Kiu lng sng c: Than bn c thnh to trn cc m ly do cc

on sng b b dng, lng sng ch cn nhn c cc vt liu mn. Qu trnh m

ly ha to iu kin pht trin thc vt: cc loi sen, sng, lau, sy, choai. Khi

cht, chng vi lp ht lp ny n lp khc . Kiu thnh

to ny rt tr, mc phn hy cha cao, tro thp. Qa trnh m ly ha cc

dng sng c gn b bin lin quan n mc nc bin dng cao hn ngy nay 1,5 -

2,0 m vo khong 1.500 - 2.000 nm trc.

1.4.1.2. Thnh to m ly ven b bin c

L cc m than bn hnh thnh trong iu kin m ly ven bin phn b ven

ngoi ng b bin ca t bin tin Holoxen gia (6.000 - 7.000 nm trc) v

hin nm su trong vng ng bng ven bin. Ti cc m than bn ny thng c 3

lp than bn:

- di l lp tn tch thc vt ca giai on lc a trc bin tin, thng

c cc thn cy to, gc cy cao thng ng, cht ng khi bin tin vo b;

- gia l lp trm tch thc vt m ly vi l, thn, cnh b cong queo;

- trn cng cn mt lp mng xc thc vt m ly hin ang pht trin

ti y m phn nhiu l thc vt thn c. Ti nhiu ni trong s cc im than bn

ny trng thi m ly ang tn ti, qu trnh hnh thnh than bn vn din ra.

~ 36 ~

1.4.1.3. Thnh to m ly ven bin

Thnh to m ly ven bin gm nhng m ly nc ngt b nh hng

thy triu khng thng xuyn v cc m ly ven bin hin i. c trng ca

thnh to ny l phn y l lp st nhuyn, b nho, mu xm nht, cha mn thc

vt v cc mnh v s.

Mi trng thnh to t ngt, l n mn.

Cc m ly pht trin cc loi thc vt t nc ngt, l n mn.

1.4.2. c tnh l ha ca than bn

V mt bn cht th sn phm to thnh do s phn gii xc thc vt ch yu

l CH4, H2S, CO... ng thi xut hin nhiu - hu c v tch lu nhiu cht sp,

m. Xc hu c t b thay i hnh dng v bin thnh cht mu en v nh hnh

gi l than bn. Qu trnh phn gii ny khng hon ton, trong mt phn xc

hu c chuyn thnh cc lp cht hu c mi gi l mn. Tuy nhin qu trnh hnh

thnh than bn vng nhit i ni chung, nc ta ni ring cha c nghin

cu y v ton din. Tu theo iu kin hnh thnh nh: lp thc vt, tnh cht

t xung quanh, iu kin kh hu... c lin quan n qu trnh phn gii hu c m

c im, thnh phn, tnh cht ca cc m than bn cc vng cng rt khc nhau.

Kh nng hp ph ni chung v hp ph kim loi nng ni ring ca than

bn c c l do thnh phn cht hu c ca chng. Nhn chung, cht hu c c

kh nng hp ph kim loi nng cao (xem mc 1.1.5). Tuy nhin, trong than bn

cng cha nhiu kim loi nng c hi, do , nu s dng khng hp l, than bn

hon ton c kh nng tr thnh ngun cung cp kim loi nng c hi cho t.

Nm 2004, Vin Th nhng nng ha tin hnh xc nh thnh phn ha

hc ca than bn mt s im trn ton quc [26]. Kt qu trnh by trong phn

ph lc cho thy, than bn vng nhit i c pH thp (trung bnh 3,97), m cao

(trung bnh 42,1 %), mc phn gii (mc mn ha) tng i cao (trung bnh

35,3 %), thch hp cho sn xut phn bn, cc ch tiu dinh dng kh cao (N tng

s trung bnh 1,12 % N, OC trung bnh 22,55 %, P2O5 tng s trung bnh 0,141 %

~ 37 ~

v K2O tng s trung bnh 1,191 %) ; hm lng Fe2+

v Al3+

dao ng ln gia cc

m, t trung bnh 15,55 mg Al3+/100g than bn v 53,43 mg Fe2+/100g than bn.

Cc nguyn t kim loi nng c hm lng nm trong khong cho php, c th nh

hm lng Pb2+ dao ng t 11,6 - 71,1 ppm v Cd2+ dao ng t 0,17 - 10,18 ppm.

Trong than bn c cha cc mui ho tan ca - humic, c tc dng iu

ho sinh trng. Cc nhm quinoid hydr - phenolic ca - humic c tc dng

chng cc bnh ng rut. Vin Nghin cu onhiep Petrosky (Lin X c)

a cht kch thch sinh trng ny vo sn xut nng nghip Ucraina. Nm 1991

xy dng xng pilot sn xut Nitrohumate do Phn vin Kalinin thuc Vin

Nghin cu Than bn ton Lin bang nghin cu.

1.4.3. S dng than bn

Nhng nc c than bn trn th gii u s dng vo cc mc ch chnh

nh: lm nhin liu, sn xut phn bn, dng trong vn m cy, trng cy trong

nh knh, sn xut cht kch thch sinh trng, men gia sc...

M l nc c nhu cu phn bn t than bn rt ln. ng thi, din tch c

than bn nc M cng kh ln, khong 6 triu ha vi tr lng 15 t tn. Hin

nay, M khai thc hng nm 600-800 ngn tn, ch yu l dng cho cng nghip.

Tuy vy, M vn phi nhp thm t c, Ba Lan, an Mch, Na Uy v Phn Lan

khong 500-600 nghn tn. Trong nng nghip, than bn M thng c x l

theo cc phng php nh vi phn hoc cc ph phm khc; phi trn cc phn

khong; hot ho than bn bng amoniac kt hp nhit cao, m cao; hoc

em trn vi t trng lm vn trong nh knh.

Phn Lan c din tch m than khong 10 triu ha (chim 31,9 % din tch c

nc) vi tr lng khong 30 t tn, than bn y thng c s dng b sung

vo t trng cy trong nh m v lm nhin liu (khong 30.000 tn) hoc dng

sn xut phn cho nng nghip (thng vi phn hoc cc ph phm khc).

Thu in c din tch than bn chim 10 % din tch c nc, n nm

2000 khai thc khong 25 triu tn/nm dng lm nhin liu v phn khong-hu

~ 38 ~

c, hng nm khai thc 1 triu m3 dng cho lm vn. Ngoi ra, cn 30 - 35% dng

cho xut khu.

Tip Khc (c) - nay gm 2 nc: Cng ho Sc v Slvakia c din tch

than bn khong 26.000 ha, hng nm sn xut 1,2 triu tn phn t than bn

(thng s dng 10 - 12 % than bn trong phn ). Nm 1991 c khong 14 nh

my sn xut phn t than bn. c bit, t nm 1990, nc ny c Lut cm s

dng than bn lm nhin liu.

Than bn nm ri rc trn a bn 8 nc cng ho Lin X (c). Phn

Chu u ca Lin X (c) c 15 t tn, phn Chu c 66 t tn. Than bn Lin

X (c) phn ln lm nhin liu cho nh my in, l hi, sn xut than ng bnh,

phn bn. Nm 1991 Lin X (c) mi s dng c 1 % lng than bn khai

thc c ch bin ho hc.

Lin X (c) sn xut c phn vin khong-hu c t than bn bng

cc phng php sau: vi phn hoc cc ph phm khc; phi trn cc phn

khong; hot ho than bn bng amoniac kt hp nhit cao, m cao. Phn

khong-hu c cho nng sut cy ly ht tng 12 - 17 %, khoai ty 5 %. Loi phn

bn ny c tc dng di n 2-3 nm. Tiu tn than bn sn xut phn bn dng

vin so vi phn gim 20 - 25 %. V vy Lin X (c) khuyn khch sn xut

dng phn vin. Beloruxia (hin nay l mt quc gia ring) nm 1991 c hai phn

xng dng pilot sn xut phn dng vin. n nay m rng sn xut n

100.000 tn/nm.

Trung Quc c din tch than bn khong 2,3 triu ha. Phn ln than

dng lm phn bn v thng s dng phng php vi phn hoc

cc ph phm khc. Indonesia

.

~ 39 ~

CHNG II. I TNG, MC TIU, NI DUNG V PHNG

PHP NGHIN CU

2.1. I TNG V MC TIU NGHIN CU

2.1.1. Mc tiu nghin cu

Nghin cu c thc hin nhm mc tiu nh gi kh nng hp ph Pb2+

v Cd2+

linh ng ca t bc mu b nhim ch v cadmi cc mc nhim khc

nhau v nh gi kh nng ci thin mc hp ph cc kim loi c hi trn sau

khi b sung lng nht nh cht hp ph c la chn l bentonite lm giu

Na v than bn . ti nhm mc tiu nh gi kh nng lm gim mt

cch n nh lng Pb2+ v Cd2+ linh ng d b thc vt ht thu ca bentonite v

than bn trong t. Do , cc nh gi sau y s s dng khi nim c nh kim

loi nng vi nh ngha l lng kim loi nng khng chit rt c bng

CH3COONH4 1M.

2.1.2. i tng nghin cu

a, t xm bc mu

t s dng trong nghin cu l t tng mt (ly su 0 - 20 cm) trong

rung trng rau mu trn a bn x Vn Tr, huyn ng Anh, thnh ph H Ni.

V mt phn loi hc, t c xp vo nhm t xm bc mu trn nn ph sa c.

b, Bentonite hot ha Na

Vt liu bentonite s dng trong th nghim c ly t m bentonite C

nh (Thanh Ha) v c hot ha Na theo phng php thng dng sau:

bentonite th c sy kh nhit 60oC, sau c lc trong dung dch NaCl

1M theo t l 20g bentonite / 25 ml NaCl trong iu kin nhit phng trong vng

mt tun. Sau , ra ion Cl- bng nc ct hai ln. Cui cng, mu c sy kh

nhit 100oC trong 24 gi v ry qua ry 50 m.

c, Than bn

Do than bn Vit Nam c c tnh l pH thp nn chng phi c x l

trc khi s dng trnh lm gim pH t. Than bn dng trong nghin cu c

~ 40 ~

khai thc ti m than bn x ng Tm, huyn M c, thnh ph H Ni. Than

bn sau khi khai thc c phi kh t nhin trong khong 8 n 10 ngy nhm lm

gim hm lng nc; trong qu trnh ny, than bn lin tc c trn u. Sau ,

than bn phi kh c nghin nh. Mc ch ca vic lm ny l nhm to mi

trng ho kh cho cc vi sinh vt phn hy ho kh hot ng. Cc vi sinh vt ny

phn hy cc a-xt hu c trong than bn, nng gi tr pH ca thnh phm; ng

thi chng hot ha cc cht mn, l ngun dinh dng cao cho cy trng nhng

thc vt khng th s dng cc dng cht ny nu mn khng c hot ha. Qu

trnh hot ha than bn ny cng ph hy cc bitum, l cht chim hm lng tng

i ln trong than bn nhng c tc dng c ch cy trng.

2.2. NI DUNG NGHIN CU

ti thc hin cc ni dung sau:

- Phn tch cc tnh cht l - ha hc ch yu ca t v cc vt liu hp

ph: pH, CEC, thnh phn c gii, Cd v Pb tng s. Ni dung ny nhm nh gi

bc u cc tnh cht ca t v vt liu hp ph, to c s cho vic tin hnh cc

bc tip theo v nh gi nh hng ca cc tnh cht l ha hc n kh nng c

nh Pb v Cd ca t v vt liu hp ph.

- Gy nhim nhn to t nn bng dung dch ch v cadmi nitrate vi

mc ch to ngun t nhim mc mong mun cho th nghim tip sau.

- B sung vt liu hp ph vo t hm lng xc nh.

- Phn tch cc mu t sau khi c b sung vt liu hp ph nh gi

mc tng lng c nh Pb v Cd linh ng so vi mu i chng.

- nh gi cc kt qu thu c bng cc phng php thng k ton hc

xy dng mi tng quan gia lng vt liu b sung vo t v kh nng c

nh ca t c b sung vt liu.

~ 41 ~

2.3. PHNG PHP NGHIN CU

2.3.1. Phng php thu thp ti liu

Thu thp, k tha cc kt qu nghin cu c v hp ph, v kim loi nng

ni chung v Cd, Pb ni ring, v bentonite v than bn v kh nng s dng ca

cc vt liu ny trong nng nghip, trong x l mi trng ni chung v trong vai

tr l vt liu hp ph kim loi nng trong t ni ring.

2.3.2. Phng php ly mu ngoi thc a

Mu t ngoi ng rung c ly theo phng php ly mu nng ha

tng mt ca Vin Th nhng nng ha [27]. -

.

Mu t sau khi ly ngoi ng rung v c hong kh ngoi khng kh

di mi che, sau c nghin nh, nht sch xc thc vt. Mu dng phn tch

trong phng th nghim c bo qun trong ti nha P.E.

2.3.3. Phng php trong phng th nghim.

2.3.3.1. Cc phng php phn tch

Phn tch cc ch tiu l ha hc ca t nn v vt liu hp ph theo cc

phng php ghi trong [27] v [14]. t c phn tch ti B mn Khoa hc t

(Khoa mi trng, trng i hc Khoa hc t nhin H Ni) v Trung tm phn

tch, Vin Quy hoch v thit k nng nghip. Bentonite v than bn c phn tch

ti Phng phn tch trung tm, Vin Th nhng nng ha. Cc ch tiu phn tch

c th nh sau:

- pHKCl : lc u dung

dch khi cho 50 ml KCl 1N vo 10g t trong 15 ph

ri o pH bng my o pH meter Metrohm 744 (Thy S).

- Cht hu c trong t (OC): xc nh bng phng php Walkley -

20 ml H2SO4 + 10 ml K2Cr2O7

; thm 200 ml 10 ml H3PO4

~ 42 ~

4 .

Thc hin tng t vi mu trng (khng c t).

Kt qu c tnh theo cng thc:

x 4 (%) [2.1].

Trong , OC l hm lng cht hu c (%), Vo v V1 l th tch mui

FeSO4 dng chun mu trng v mu phn tch theo th t (ml).

- Thnh phn c gii (TPCG): -

1l, thm 25 ml pyrophosphate 5 %

50

105o

.

- Dung tch trao i cation (CEC): Xc nh theo phng php

amoniacetate: 100 ml CH3COONH4

4+

250 ml

t (25 ml x 10 ln)

. Kt qu c tnh theo cng thc rt gn:

E = V x 5 [2.2]. Trong E l dung tch trao i cation (meq / 100g t) v V l th

tch NaOH dng chun (ml).

- Pb v Cd tng s: cn 0,5g t ( ry qua ry 1mm) vo bnh tam gic,

cho 5 - 10ml nc cng toan (hn hp HNO3 + HCl t l 1:3); ph mu 150oC

trong vng 2h (c y phu) n khi mu trng; sau nh mc ln ti 50ml bng

nc ct ri lc. Dung dch chit thu c c phn tch bng phng php quang

~ 43 ~

ph hp th nguyn t (AAS) trn my VARIAN AA280FS (phng php t bng

ngn la).

- Pb v Cd trong t: Chit Pb, Cd di ng bng dung dch

CH3COONH4 1M (pH = 4,8) vi t l 5g t/ 50ml dung dch chit rt. Lc trong 1h

ri em lc, sau nh lng bng phng php quang ph hp th nguyn t

(AAS) trn my VARIAN AA280FS (phng php t bng ngn la).

2.3.3.2. B tr th nghim.

Bc 1: Chun b mu dung dch chun ch v Cadmi:

Pha dung dch chun PbNO3 2.000mg/l v dung dch chun CdNO3 100mg/l.

Bc 2: Chun b mu: gy nhim kim loi nng cho t:

t sau khi c phi kh, gi nh v loi b r cy v cc tn d khc, c

trn u v cn u vo cc chu th nghim vi khi lng 1kg/chu chun b

th nghim. T dung dch chun PbNO3 2.000 mg/l ln lt ly ra:

+ 70 ml dung dch, tng ng vi vic b sung 140 mg Pb2+;......(D1).

+ 120 ml dung dch, tng ng vi vic b sung 240 mg Pb2+, ...(D2).

+ 300 ml dung dch, tng ng vi vic b sung 600 mg Pb2+, ...(D3).

- T dung dch chun CdNO3 100 mg/l, ly ra ln lt:

+ 40 ml dung dch, tng ng vi vic b sung 4 mg Cd2+, .....(D4),

+ 100 ml dung dch, tng ng vi vic b sung 10 mg Cd2+,......(D5),

+ 200 ml dung dch, tng ng vi vic b sung 20 mg Cd2+,......(D6).

Ln lt cho cc dung dch D1, D2, D3, D4, D5, D6 vo chu th nghim ng

t gy nhim. K hiu cc mu t theo ln lt l Pb1, 2, 3 v Cd1, 2, 3

tng ng vi cc dung dch t D1 n D6 nu trn c s dng gy nhim

t. Dng nc ct a m trong cc chu n mc bo ha, sau t trong

iu kin kh khng kh trong khong 2 n 3 ngy.

Bc 3: B sung than bn v bentonite vo t nhim:

~ 44 ~

Tip theo, b sung cc t l khc nhau vo cc

mu t gy nhim :

- 0 g/kg t (tng ng 0 tn/ha) DC

).

- 2,5g /kg t (tng ng 5 tn/ha) ..BENT1 v TB1

1 CT1).

- 5 g/kg t (tng ng 10 tn/ha)... BENT2 v TB2

2 CT2).

- 7,5g/kg t (tng ng 15 tn/ha)..... BENT3 v TB3

3 CT3).

- Trong , BENT v TB l k hiu ln lt ca cc mu c b sung

bentonite v than bn theo cc mc khc nhau.

Tip tc s dng nc ct a t trong cc mu n mc bo ha v

m. mu trong iu kin kh khng kh trong khong 2-3 ngy ri xc nh hm

lng kim loi nng linh ng trong t.

Nh vy, tng cng trong th nghim c 42 mu t, trong c 6 mu i

chng (3 mu gy nhim Pb 3 mc nhim v 3 mu gy nhim Cd 3 mc

nhim) c k hiu ln lt l DC-Pb1, 2, 3 v DC-Cd1, 2, 3; 9 mu t c

gy nhim Pb ba mc v b sung bentonite ba mc c k hiu ln lt l

BENT1-Pb1, 2, 3, BENT2-Pb1, 2, 3 v BENT3-Pb1, 2, 3; 9 mu t gy nhim

Pb 3 mc v c b sung than bn ba mc c k hiu ln lt l TB1-Pb1,

2, 3, TB2-Pb1, 2, 3 v TB3-Pb1, 2, 3; 9 mu t c gy nhim Cd ba mc v

b sung bentonite ba mc c k hiu ln lt l BENT1-Cd1, 2, 3, BENT2-

Cd1, 2, 3 v BENT3-Cd1, 2, 3; 9 mu t c gy nhim Cd ba mc v b

sung than bn ba mc c k hiu ln lt l TB1-Cd1, 2, 3, TB2-Cd1, 2, 3 v

TB3-Cd1, 2, 3.

.Cc mu th nghim sau khi kh khng kh, em nghin nh v ry qua

ry 1mm. cn 5g t lc vi dung dch NH4NO3 1M nh trnh by trn

(phng php phn tch hm lng kim loi nng linh ng).

~ 45 ~

Cc mu i chng (khng dng vt liu x l) c phn tch hm lng kim

loi nng tng s.

2.3.4. Phng php x l s liu

Xc nh hm lng kim loi linh ng trc v sau qu trnh thc nghim,

ta tnh c hiu qu c nh kim loi theo cng thc:

[2.3]

Trong :

a: hiu qu c nh (%)

I: hm lng kim loi b c nh trong mu i chng DC (ppm)

Ci: hm lng kim loi c nh trong cc mu BENT v TB1, 2, 3 (ppm).

Ci c tnh theo cng thc [2.4] di y:

Ci = T P [2.4]

Trong :

Ci: hm lng kim loi nh trong cc mu BENT v TB1, 2, 3 (ppm).

T: hm lng kim loi tng s trong mu i chng DC (ppm)

P:hm lng kim loi linh ng trong cc mu BENT v TB1, 2, 3 (ppm).

Cc kt qu thu c c x l bng chng trnh thng k v x l s liu

thng dng Microsoft Excel. Mc tiu ca cc bin php x l s liu l tm kim

mi tng quan gia lng vt liu b sung vo t v hiu qu cng nh hm

lng ch v cadmi b c nh nh phng php b sung vt liu nu trn, qua

nh gi kh nng ng dng trong thc tin ca cc vt liu ny trong vai tr l vt

liu c nh kim loi nng trong t b nhim.

~ 46 ~

CHNG 3. KT QU NGHIN CU V THO LUN

3.1. CC TNH CHT C BN CA T V VT LIU HP PH

3.1.1. Cc tnh cht c bn ca t

Cc kt qu phn tch tnh cht l ha hc ca t s dng trong th nghim

trnh by trong bng 10 cho thy: t xm bc mu trn nn ph sa c ng Anh

(H Ni) c thnh phn cp ht tht pha ct (tht nh)

(gm c ct th v ct mn) 36,62 %, 10,08

%; pH hi chua, pHKCl 5,3; ngho dinh dng (cht hu c trong t mc

thp 0,89 %); dung tch trao i cation ) thp

, lng Cadmi v ch tng s ngng an ton

Pb (thp xa so vi quy nh trong quy chun k thut quc

gia v gii hn cho php ca kim loi nng trong t, QCVN 03: 2008/ BTNMT l

2 ppm cho Cd v 70 ppm cho Pb [4]).

Bng 10. Cc tnh cht l ha hc ch yu ca t nn

TT Ch tiu Gi tr n v tnh

1 pHKCl 5,3

2 Cht hu c trong t (OC) 0,89 %

3

Thnh phn c gii

Cp ht ct (2 - 0,02 mm) 36,62 %

Cp ht limon (0,02 - 0,002 mm) 53,30 %

Cp ht st (< 0,002 mm) 10,08 %

4 Dung tch cation trao i (CEC) 8,89 meq/100g

5 Hm lng cadmi tng s (Cdts) 0,10 ppm

6 Hm lng ch tng s (Pbts) 7,77 ppm

~ 47 ~

3.1.2. Cc tnh cht c bn ca bentonite C nh

Kt qu phn tch trnh by trong bng 11 cho thy bentonite C nh

thuc loi bentonite kim th, c phn ng gn trung tnh, pHKCl 6,2; dung tch

hp thu (CEC) kh cao, 46,55 meq/100 g, tuy nhin vn thp hn so

vi mt s loi bentonite khc (xem ph lc 9), hm lng kim loi nng thp

13,25 ppm.

.

Bng 11. Cc tnh cht l ha hc ch yu ca bentonite.


1 m 12,60 %

2 pHKCl 6,2

3

Thnh phn c gii

Cp ht ct (2 - 0,02 mm) 8,60 %

Cp ht limon (0,02 - 0,002 mm) 17,40 %

Cp ht st (< 0,002 mm) 74,00 %




Chu Vn Lam v Phm Vn He (1999) [dn theo 11] phn tch 4 mu

bentonite vng C nh bng phng php nhiu x Rnghen (XRD) v phng

php nhit vi sai (DTA), kt qu cho thy thnh phn khong vt ca bentonite C

nh gm ch yu l montmorillonite (35 - 44 % theo XRD v 38 - 42 % theo

DTA), hydromica chim t l 8 - 15 % theo XRD v 10 - 13 % theo DTA, chlorite

~ 48 ~

chim t l 10 - 20 % theo XRD v 12 - 17 % theo DTA, kaolinite chim t l 10 -

14 % theo XRD v 8 % theo DTA, thch anh chim t l 7 - 15 % (XRD), felspartz

chim t l 5 - 8 % (XRD), hydrogertite chim t l 7 - 10 % theo XRD v 5 - 8 %

theo DTA, cn li l cc khong vt khc nh Ca, amphibol. i chiu vi s

liu thu c t phn tch nhit vi sai ti Vin Th nhng nng ha, cc kt qu

trn khng sai khc, tr trng hp montmorillonite c kt qu chnh vi Vin Th

nhng nng ha khong 10 % (kt qu ca Vin Th nhng nng ha l 52 %).

Ngoi ra, Vin Th nhng nng ha cng phn tch thnh phn ha hc ca

bentonite C nh. Kt qu phn tch cho php rt ra kt lun l khc bit ln gia

bentonite C nh vi cc loi bentonite khc l hm lng Na2O v K2O trong

bentonite C nh thp hn rt nhiu loi bentonite khc, nht l bentonite

Wyoming (M), trong khi t l Fe2O3 v MgO li cao hn ng k. Kt qu phn

tch ny c trnh by trong phn ph lc.

3.1.3. Cc tnh cht c bn ca than bn.

Kt qu phn tch mt s tnh cht c bn ca mu than bn c trnh by

trong bng 12 cho thy than bn vng H Ty (c) c phn ng chua n rt chua,

pHKCl 3,75. y l khc bit ln nht ca than bn nc ta so vi than bn cc

nc khc, c bit l cc nc vng n i, ni than bn thng c phn ng kim

n kim nh. Than bn M c c hm lng cht hu c (OC) kh,

(xem 11). Dung tch trao i cation (CEC)

, 31,8 meq/100 g,

. Hm lng kim loi nng tng s tng i thp

. Sau khi c

phi kh t nhin v , phn bn bin tnh, th hin ch s pH tng cao hn

(pHH2O sau khi phi kh t gi tr 6,1).

~ 49 ~

Bng 12. Tnh cht c bn ca than bn M c (H Ni)


1 m 31,20 %

2 pHKCl 3,75

3 Cht hu c (OC) 15,13 %




3.2. S THAY I MT S TNH CHT L, HA HC CA VT

LIU SAU X L V CA T SAU KHI C B SUNG BENTONITE

V THAN BN.

3.2.1. S thay i ca mt s tnh cht ca vt liu sau khi x l

Sau khi x l vt liu hp ph bng cc phng php nu chng 2,

chng ti tip tc phn tch li cc tnh cht ha hc c bn ca vt liu c lin quan

mt thit n kh nng hp ph ca chng, l cc ch tiu: m, pHKCl, v

CEC. Mc ch ca vic phn tch li cc tnh cht ny l nhm nh gi kh nng

tng hiu qu hp ph ca vt liu thng qua s thay i cc tnh cht ha hc trn

sau cc bin php x l nu.

Kt qu phn tch cho thy cc ch tiu ha hc nu trn u c thay i theo

hng tng ln. C th, pHKCl ca than bn sau khi x l tng 0,3 n v; t 3,7 ln

4,0; CEC ca than bn cng tng khong 25 %; t 31,80 ln n 44,04 meq/ 100 g.

i vi bentonite c khc bit i cht; pHKCl ca bentonite gim t 6,2 xung cn

5,7 nhng CEC li tng gn 50 % t 46,55 ln 63,78 meq/100 g.

~ 50 ~

Kt qu cng cho thy m (sc cha m) ca than bn gim i r rt sau khi

x l, t khong 30 % xung ch cn 9 %. Trong khi , m ca bentonite hu

nh khng thay i (12,60 so vi 10,64 %).

Bng 13. Kt qu phn tch m, pH v CEC ca vt liu sau x l

STT Vt liu

Ch tiu

Than bn Bentonite

1 pHKCl 4,0 5,7

2 CEC (meq/100 g) 44,04 63,78

3 m (%) 9,18 10,64

Nhn chung, cc kt qu ny u cho thy s ci thin ng k kh nng hp ph

kim loi nng ca vt liu v khi CEC v pH tng th kh nng c nh kim loi

nng ca vt liu cng tng theo (xem chng 1).

3.1.2. Thay i tnh cht t sau khi b sung vt liu hp ph

Vic gy nhim t bng hai dung dch mui nitrate ch v cadmi ko theo

s thay i ng k hai tnh cht ha hc c b kh nng c nh

kim loi nng ca t l pHKCl v dung tch trao i cation (CEC ).

C th, kt qu phn tch cho thy pHKCl ca mu i chng (t sau khi gy

nhim v khng b sung vt liu hp ph) t

(4 ppm -Cd1), 10 ppm -Cd2)

(20 ppm -Cd3), tng kho

0,8 n v so vi t t nhin (pHKCl = 5,3).

140 ppm Pb -Pb1

240 ppm Pb -Pb2)

600 ppm Pb -Pb3); cao hn pHKCl

. CEC ca cc mu i chng t khong 12,50 meq/100g t, tng khong 50 %

so vi t t nhin. -

-

~ 51 ~

-

( -

- -

.

Ngoi ra, mt im ng lu l lng Pb v Cd tng s ca mu i chng

c s khc bit so vi tng ca lng Pb v Cd c b sung vo t v lng Pb

v Cd tng s sn c trong t.

C th, lng Pb tng s c trong t l 7,77 ppm, lng b sung ln lt l

140, 240 v 600 ppm, nhng lng Pb tng s ca mu i chng thu c ln lt

ch cn 130,81; 211,66 v 599,04 ppm, tc l lng Pb b hao ht so vi tnh ton

ln lt l 16,96; 29,11 v 8,73 ppm. Tng t, lng Cd b hao ht ln lt l

0,431 (= 4,1 3,669), tng ng 10,51 %; 1,465 (10,1 8,235), tng ng

14,51 % v 5,507 (20,1 14,593) ppm, tng ng 26,1 %.

C th gii thch hin tng ny do s ra tri hoc bay hi dung dch Pb v

Cd sau khi c b sung vo t do iu kin t nhin.

Tuy nhin, khi b sung bentonite v than bn vo t gy nhim,

khng tip tc thay i m gn nh gi nguyn gi tr. Nguyn nhn c th

l do lng bentonite v than bn b sung vo cn thp. S liu trnh by trong

bng 15 cng cho thy k c khi tng thm lng Cd v Pb vo t, pH t vn ch

gi mc xung quanh gi tr 6,2 v CEC dao ng xung quanh khong 11 - 14

meq/100g t

- .

-

-

- 12,8

~ 52 ~

- 13,03

bentonite /ha 2-Cd2 13,30

3-Cd3 13,79

. /ha

BENT1-Cd3 12,74

bentonite /ha 2-Cd3 13,1

3-Cd3 13,14

.

BENT1-Pb1), pH

-

-

-

-

/ha ( -

.

-

-

-

.

-

12,60 m

-

- 13,2

5 - 6

12,52 -

13,07

- 5,9 t 13,18 .

/ha - 12,63

~ 53 ~

-

12,92 ; khi -

13,53

- 12,35

- 6 12,5

-

11,98

- 12,64

2-Pb2), p 6,1 13,11

- 12,02

. -

12,23

- 12,85

3-P 5, 13,87 .

Nguyn nhn c th l gii l do s bo ha ca cc phn

ng trao i gia cc hp phn t v cc ion ni trn. Kh

.

Mc d vy, vn c th nu mt s nhn xt:

- Khi b sung than bn vo t, pH tng thp hn cht t so vi khi b sung

bentonite, ng thi CEC li tng nhiu hn.

- CEC t t l thun vi lng bentonite v than bn

bn vo t.

- Tng lng Pb v Cd gy nhim cho t, pH ca t c xu hng gim.

Tuy nhin, iu ny khng l gii c hin tng gia tng pH ca t mc tng

i ln khi bt u gy nhim t.

Cc hnh 2, 3, 4, v 5 di y minh ha r hn nhn xt trn:

~ 54 ~

Hnh 2. pH v CEC

.

, cc im trn ng theo hng i

ca th tnh t pha tri

.

Hnh 3.

.

5.75

5.8

5.85

5.9

5.95

6

6.05

6.1

6.15

12 12.5 13 13.5 14

Cdts = 3,669 ppm

Cdts =8,235 ppm

Cdts = 14,593 ppm

CEC

5.9

5.95

6

6.05

6.1

6.15

6.2

6.25

11.5 12 12.5 13 13.5 14 14.5 15

Pbts = 130,81 ppm

Pbts = 211,66 ppm

Pbts = 599,04 ppm

pH

CEC

pH

~ 55 ~

Hnh 4.

.

Hnh 5.

.

5.85

5.9

5.95

6

6.05

6.1

6.15

12.2 12.4 12.6 12.8 13 13.2 13.4 13.6

Cdts = 3,669 ppm

Cdts = 8,235 ppm

Cdts = 14,593 ppm

CEC

pH

5.85

5.9

5.95

6

6.05

6.1

6.15

6.2

6.25

11.5 12 12.5 13 13.5 14

Pbts = 130,81 ppm

Pbts = 211,66 ppm

Pbts = 599,04 ppm

pH

CEC

~ 56 ~

Bng 14. Gi tr pH v CEC ca mu th nghim

K hiu

mu

pHKCl CEC (meq/100g t)

nhim Pb nhim Cd nhim Pb nhim Cd

1 2 3 1 2 3 1 2 3 1 2 3

DC 6,18 6,19 6,12 6,05 6,12 6,03 12,48 12,55 12,39 12,82 12,36 12,54

BENT1 6,02 6,12 5,94 6,03 5,96 5,92 11,71 12,91 12,73 12,86 13,03 12,74

BENT2 5,96 5,96 6,07 6,00 5,91 5,86 12,20 12,20 14,56 12,91 13,30 13,11

BENT3 6,14 6,12 6,00 6,02 5,9 5,80 12,77 12,75 13,20 13,81 13,79 13,14

TB1 5,93 5,95 5,87 5,99 6,10 6,08 12,35 12,64 12,23 12,60 12,52 12,63

TB2 6,04 6,13 5,97 5,92 6,01 5,97 12,51 13,11 12,85 12,87 13,07 12,92

TB3 6,00 6,02 5,98 5,90 5,92 5,98 11,98 12,02 13,87 13,21 13,18 12,53

Ch thch: Cc ct nh s 1, 2, 3: cc mc gy nhim ch v cadmi nh nu trong phn phng php nghin cu.

~ 57 ~

3.3. HIU QU C NH Pb2+ v Cd2+ CA BENTONITE TRONG T

3.3.1. Hiu qu c nh Pb2+ ca bentonite

Kt qu phn tch hm lng Pb2+ linh ng trong mu th nghim

2+ c trnh by trong bng

15 v hnh 6, 7, 8, 9, 10. 2+

c nh iu

qu c nh c tnh theo cng thc nu trong phn phng php nghin cu. T

kt qu thu c, c th rt ra mt s nhn xt nh sau:

- c nh 46 - 2+ .

nh sunphate, chlore, hydratecarbonate , Pb2+

-

- 1.1).

70 ppm Pbts

. (Pbts

- (Pbts

-

(Pbts -Pb3).

- Hiu qu c nh ca bentonite t c mc cao nht khi mc

nhim ch thp. 140 ppm Pb2+), % tng lng c

nh (5 T/ha 1-Pb1

(10 T/ha 2-Pb1

(15 T/ha 3-Pb1

,

1 - 2 % ).

- Hiu qu c nh ca bentonite cng mc nhim ch t c

cao nht khi lng bentonite b sung vo t cao. , % tng

~ 58 ~

lng c nh

240 ppm Pb2+), % tng lng c nh

2,24 % 3-Pb2) 10

T/ha bentonite 2-Pb2) 5 T/ha bentonite

BENT1-Pb2) 600 ppm Pb2+

), % tng

nh 15 T/ha bentonite 3-

Pb3) 1,48 % 2-Pb3) 0,31 % 1-Pb3)

.

- c nh

c nh kim loi nng .

-

(Pbts = 310,81 ppm)

:

Y = 0,477X + 2,08. (1)

: X l (t /ha)

c nh Pb2+ (%)

xc nh 2 = 0,619.

2 (Pbts = 211,66 ppm)

:

Y = 0,142X + 0,21. (2)

xc nh 2 = 0,942.

(Pbts = 599,04 ppm)

:

Y = 0,146X + 0,139. (3)

~ 59 ~

xc nh 2 = 0,956.

2+

(Pbts = 310,81 ppm)

(1)2+

:

2 (Pbts = 211,66 ppm)

Pb2+

(Pbts = 599,04 ppm) /ha.

15 c nh Pb2+

2+

c

nh (ppm)

2+

(ppm)

% tng lng c nh

DC-Pb1 62,93 67,88 0,00

BENT1-Pb1 73,347 57,463 7,96

BENT2-Pb1 70,922 59,888 6,11

BENT3-Pb1 74,156 56,654 8,58

DC-Pb2 99,31 112,35 0,00

BENT1-Pb2 101,93 109,73 1,24

BENT2-Pb2 102,776 108,884 1,64

BENT3-Pb2 104,057 107,603 2,24

DC-Pb3 282,02 317,02 0,00

BENT1-Pb3 283,883 315,157 0,31

BENT2-Pb3 290,885 308,155 1,48

BENT3-Pb3 294,353 304,687 2,06

~ 60 ~

2+ t cc mu c b sung bentonite.

-

-

- 4

3-Pb1, 2, 3.

72+

c nh trong cc mu c b sung bentonite

0

50

100

150

200

250

300

350

1 2 3 4

Pbts = 130,81 ppm

Pbts = 211,66 ppm

Pbts = 599,04 ppm

Pb2+

(ppm)

0

50

100

150

200

250

300

350

1 2 3 4

Pbts = 130,81 ppm

Pbts = 211,66 ppm

Pbts = 599,04 ppm

Pb2+

(ppm)

~ 61 ~

c nh -

c nh -

c nh - 4 c

nh 3-Pb1, 2, 3.

c nh Pb2+

1 (Pbts = 130,81 ppm)

9. c nh Pb2+

2 (Pbts = 211,66 ppm)

y = 0.477x + 2.08

R = 0.619

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

0 2 4 6 8 10 12 14 16Bentonite (T/ha)

%

y = 0.142x + 0.210

R = 0.942

0.00

0.50

1.00

1.50

2.00

2.50

0 5 10 15 20

Bentonite (T/ha)

%

~ 62 ~

10. c nh Pb2+

3 (Pbts = 599,04 ppm).

c nh Cd2+

2+

nng c nh 16

2+c nh c nh

:

- c nh Cd2+ 33 - 40 %. C

(Cdts c nh

40,17 % -Cd1) (Cdts = 8,235

ppm c nh 36,42 % -Cd2)

(Cdts c nh

33,10 % -Cd3) t l Pb b c nh, t l Cd

b c nh bi

-

1.1).

c nh

y = 0.146x - 0.139

R = 0.956

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

0 5 10 15 20 Bentonite (T/ha)

%

~ 63 ~

.

- c nh

c nh

c

nh . ,

(Cdts c nh

4,69 % 1-Cd1), 8,20 % 2-Cd1) 2,75 % 3-

Cd1) ts 0,53 % 1-

Cd2), 6,22 % 2-Cd2) 4,04 % 3-Cd2)

(Cdts 2,87 % 1-Cd3),

3,68 % 2-Cd3) 2,60 % 3-Cd3)

c

nh c nh

.

- c nh

hi bentonite / ha. (Cdts

c nh

.

- c nh

(Cdts c nh

/ha 1-Cd1), /ha

~ 64 ~

2-Cd1) /ha 3-Cd1)

(Cdts 0,53 %

1-Cd2); 6,22 % 2-Cd2) 4,04 % 3-Cd2)

(Cdts 2,87 % 1-Cd3);

3,68 % 2-Cd3) 2,60 % 3-Cd3).

- c nh

:

(Cdts :

Y = - 0,101X2 + 1,756X 0,389

(T/ha)

c nh Cd (%)

xc nh R2 = 0,914

(Cdts :

Y = - 0,027X2 + 0,762X 0,650

xc nh R2 = 0,676

(Cdts :

Y = - 0,039X2 + 0,765X + 0,008

xc nh R2 = 0,999

c nh

c nh

c

nh 3,75 %.

~ 65 ~

162+

c nh

.

.

16 c nh Cd2+

Cd2+

c

nh (ppm)

Cd2+

(ppm)

% tng lng c nh

DC-Cd1 1,474 2,195 0,00

BENT1-Cd1 1,646 2,023 4,69

BENT2-Cd1 1,775 1,894 8,20

BENT3-Cd1 1,575 2,094 2,75

DC-Cd2 2,999 5,236 0,00

BENT1-Cd2 3,043 5,192 0,53

BENT2-Cd2 3,511 4,724 6,22

BENT3-Cd2 3,332 4,903 4,04

DC-Cd3 4,83 9,763 0,00

BENT1-Cd3 5,249 9,344 2,87

BENT2-Cd3 5,367 9,226 3,68

BENT3-Cd3 5,209 9,384 2,60

~ 66 ~

11 Cd2+

t cc mu c b sung bentonite.

-

1-Cd1,

-

3-Cd1, 2, 3.

12 Cd2+

c nh trong cc mu c b sung bentonite

0

2

4

6

8

10

12

1 2 3 4

Cdts = 3,669 ppm

Cdts = 8,235 ppm

Cdts = 14,593 ppm

Cd2+

(ppm)

0

1

2

3

4

5

6

1 2 3 4

Cdts = 3,669 ppm

Cdts = 8,235 ppm

Cdts = 14,593 ppm

Cd2+

(ppm)

~ 67 ~

c nh -

c nh -

c nh - 4 c

nh 3-Cd1, 2, 3.

13 c nh Cd2+

1 = 3,669 ppm)

14 c nh Cd2+

= 8,235 ppm).

y = -0.101x2 + 1.756x - 0.389

R = 0.914

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

0 5 10 15 20

%

Bentonite (T/ha)

y = -0.027x2 + 0.762x - 0.650

R = 0.676

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0 5 10 15 20

%

Bentonite (T/ha)

~ 68 ~

15 c nh Cd2+

= 14,593 ppm).

3.4. HIU QU C NH Pb2+ 2+ CA THAN BN TRONG T.

c nh Pb2+

2+

nng c nh Pb2+ 17

c nh Pb2+

. :

- c nh kim loi nng

(Pbts

c nh /ha (

- -

-

hai (Pbts c nh

- -

-

y = -0.039x2 + 0.765x + 0.008

R = 0.999

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 5 10 15 20

%

Bentonite (T/ha)

~ 69 ~

(Pbts = 599,04 ppm) c nh

- -

3-Pb3).

- c nh 2+

(Pbts

c nh

- - 4,30 %

- -

3 %.

-

c nh Pb2+

:

(Pbts :

Y = -0,123X2 + 2,198X 0,901

R2 = 0,765

c nh (%)

(T/ha)

R2 xc nh.

(Pbts

: Y = -0,019X2 + 0,443X 0,174

R2 = 0,864.

(Pbts

: Y = -0,031X2 + 0,620X + 0,036

R2 = 0,994.

(Pbts = 130,81

c nh (Pbts

~ 70 ~

c nh

(Pbts

c nh 3,13 % (trn ).

17 c nh Pb2+

2+

c

nh (ppm)

2+

(ppm)

% tng lng c nh

DC-Pb1 62,930 67,880 0,00

TB1-Pb1 68,556 62,254 4,30

TB2-Pb1 77,889 52,921 11,44

TB3-Pb1 67,355 63,455 3,38

DC-Pb2 99,310 112,350 0,00

TB1-Pb2 101,502 110,158 1,04

TB2-Pb2 105,345 106,315 2,85

TB3-Pb2 103,453 108,207 1,96

DC-Pb3 282,020 317,020 0,00

TB1-Pb3 296,742 302,298 2,46

TB2-Pb3 299,763 299,277 2,96

TB3-Pb3 295,475 303,565 2,25

~ 71 ~

2+ t cc mu c b sung than bn.

-

-

-

3-Pb1, 2, 3.

17 Pb2+

c nh trong cc mu c b sung than bn

0

50

100

150

200

250

300

350

1 2 3 4

Pbts = 130,81 ppm

Pbts = 211,66 ppm

Pbts = 599,04 ppm

Pb2+

(ppm)

0

50

100

150

200

250

300

350

1 2 3 4

Pbts = 130,81 ppm

Pbts = 211,66 ppm

Pbts = 599,04 ppm

Pb2+

(ppm)

~ 72 ~

c nh -

c nh -

c nh - c nh

3-Pb1, 2, 3.

c nh Pb2+

(Pbts = 130,81 ppm)

19. c nh Pb2+

(Pbts = 211,66 ppm)

y = -0.123x2 + 2.198x - 0.901

R = 0.765

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 5 10 15 20

%

Peat (T/ha)

y = -0.019x2 + 0.443x - 0.174

R = 0.864

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 5 10 15 20

%

Peat (T/ha)

~ 73 ~

20. c nh Pb2+

(Pbts = 599,04 ppm)

c nh Cd2+

2+

c nh Cd2+ 18

:

- c nh Cd2+

(Cdts c nh

- -

-

(Cdts c nh

- -

-

c nh -

-

3-Cd3).

y = -0.031x2 + 0.620x + 0.036

R = 0.994

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 5 10 15 20

%

Peat (T/ha)

~ 74 ~

- c nh Cd2+

2+

c nh

c nh

c nh

8,20 %.

- c nh Cd2+

(Cdts = 3,66 c nh -

(Cdts c nh

- (Cdts

c nh 2-Cd3).

c nh Cd2+

:

(Cdts

: Y = -0,012X2 + 0,465X 0,482

R2 = 0,681.

c nh (%)

(T/ha)

R2 xc nh ca phng trnh.

(Cdts

:

Y = -0,20X2 + 0,481X 0,129

R2 = 0,937.

(Cdts

: Y = -0,008X2 + 0,971X 0,106

R2 = 0,78.

~ 75 ~

ts

c nh ts = 8,2

c nh

ts

c nh 1,11 %.

18 c nh Cd2+

Cd2+

c

nh (ppm)

Cd2+

(ppm)

% tng lng c nh

DC-Cd1 1,474 2,195 0,00

TB1-Cd1 1,477 2,192 0,08

TB2-Cd1 1,634 2,035 4,36

TB3-Cd1 1,591 2,078 3,19

DC-Cd2 2,999 5,236 0,00

TB1-Cd2 3,113 5,122 1,38

TB2-Cd2 3,251 4,984 3,06

TB3-Cd2 3,199 5,036 2,43

DC-Cd3 4,830 9,763 0,00

TB1-Cd3 4,881 9,712 0,35

TB2-Cd3 5,026 9,567 1,34

TB3-Cd3 4,954 9,639 0,85

~ 76 ~

2 Cd2+

t cc mu c b sung than bn.

-

- 3

-

3-Cd1, 2, 3.

22 Cd2+

c nh trong cc mu c b sung than bn.

0

2

4

6

8

10

12

1 2 3 4

Cdts = 3,669 ppm

Cdts = 8,235 ppm

Cdts = 14,593 ppm

Cd2+

(ppm)

0

1

2

3

4

5

6

1 2 3 4

Cdts = 3,669 ppm

Cdts = 8,235 ppm

Cdts = 14,593 ppm

Cd2+

(ppm)

~ 77 ~

c nh -

c nh -

c nh - c nh

3-Cd1, 2, 3.

23. c nh Cd2+

(Cdts = 3,669 ppm)

24. c nh Cd2+

(Cdts = 8,235 ppm)

y = -0.012x2 + 0.465x - 0.482

R = 0.681

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

0 5 10 15 20

%

Peat (T/ha)

y = -0.020x2 + 0.481x - 0.129

R = 0.937

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 5 10 15 20

%

Peat (T/ha)

~ 78 ~

25 c nh Cd2+

(Cdts = 14,593 ppm).

y = -0.008x2 + 0.197x - 0.106

R = 0.78

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 5 10 15 20

%

Peat (T/ha)

~ 79 ~

1. KT LUN

1. Bentonite C nh c t l cp ht st t 74 %, mc trung bnh so vi

cc loi bentonite khc; phn ng gn trung tnh (pHKCl = 6,2), CEC thp so vi

cc loi bentonite khc (CEC t 46,55 meq/100 g); hm lng ch v cadmi thp.

Than bn M c c phn ng chua (pHKCl = 3,75), CEC kh cao ( t 31,80

meq/100 g), cht hu c tng s cao (OC t 15,13 %OC), hm lng ch v cadmi

thp. Sau khi x l, pHKCl v CEC ca than bn u tng (pHKCl t 4,0 v CEC

t 44,04 meq/100 g t); CEC ca bentonite sau x l cng tng ng k ( t

63,78 meq/100 g t) nhng pHKCl li gim xung cn 5,7.

2.

(8,89 meq/100 g (pHKCl

, pHKCl t

12 meq/100 g KCl

6,1). ) t

b c nh 33 - 40 % Cd2+ 46 - 48 % Pb2+

.

3. c nh Cd2+ 2+

xung 4 %.

4. , benton c nh Cd2+ 2+

.

(Cdts c nh

- c nh

0,35 - 1,34 %.

5. c nh Cd2+ 2+

.

~ 80 ~

c nh

(Pbts = 130,81 ppm) c nh

-

(Pbts 1,24 - 2,24 %.

6. c nh Cd2+ 2+

c nh

, c nh

. H xc nh ca mi tng qu ln

R2

R2 = 0,999.

trn.

2. KIN NGH

1. N

c nh

c nh

.

2 c nh

cc

kim loi nng vi c nh khc nhau trong .

3. N

.

4. N c nh

.

~ 81 ~

TI LIU THAM KHO

Ting Vit

1. , Nguyn Phng Hnh, Nguyn c Thnh (2008),

,

, (29), tr. 59 - 61.

2. ) (2008), ,

.

3. (2006), ( ),

.

4. (2010),

2010 .

5. (2004), - , Trng i

hc Khoa hc t nhin, i hc Quc gia H Ni.

6. Thu H, Phm Quang H (2008), Ch tng s v mi quan h vi mt s

tnh cht l ha hc ca t ph sa sng Hng, Tp ch Khoa hc t, (30),

tr. 16 - 19.

7. (2006),

, , (26), tr. 124 - 128.

8. Nguyn Xun Hi. (1996), Ci to t nh knh bng cht hp ph, Lun n

tin s khoa hc Th nhng, Matxcva.

9. Nguyn Th c Hnh, (2002), Mt s loi Bentonite Vit Nam v ng

dng trong ci to t, Lun vn thc s khoa hc mi trng, Trng i

hc Khoa hc t nhin, i hc Quc gia H Ni.

10. , (2007),

, , (27), tr. 110 - 114.

~ 82 ~

11. Hi Khoa hc t Vit Nam (2004), Bo co ti pht trin cng ngh ng

dng bentonite ci to t v nng cao hiu qu s dng phn bn, H

Ni.

12. (2006),

, , (26), tr. 129 - 131.

13. L Vn Khoa (1994), , , .

14. L Vn Khoa, L c v nnk (2000), Phng php phn tch t - nc -

phn bn- cy trng, NXB Gio dc, H Ni.

15.

,

, , H Ni, tr. 466 - 476.

16. , Phm Quang H, Nguyn Th Lan v nnk (2009),

,

, 5,

, H Ni, tr. 430 - 438.

17. Mai Trng Nhun (2001), a ho mi trng, NXB i hc Quc gia H

Ni.

18. Nguyn Hu On, Ng Ngc Hng (2004), Cadmium trong t la

v s cnh bo nhim, Tp ch Khoa hc t, (20),

tr. 137 - 140.

19. Nguyn c Tm, Cnh Dng (1999), nh gi ti nguyn than bn

Vit Nam - Bo co chuyn thuc ti: nh gi li

Nghiên cứu khả năng hấp phụ cadmi và chì trong đất của bentonite và than bùn

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