nghiên cứu biến tính phụ phẩm từ cây ay làm vật liệu xử lý một số ...
Transcript of nghiên cứu biến tính phụ phẩm từ cây ay làm vật liệu xử lý một số ...
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I HC QUC GIA H NI
I HC KHOA HC T NHIN
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PHM TH DINH
NGHIN CU BIN TNH PH PHM T CY AY
LM VT LIU X L MT S KIM LOI N O C
LUN V HC S KHOA HC
H Ni 2015
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I HC QUC GIA H NI
I HC KHOA HC T NHIN
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Phm Th Dinh
NGHIN CU BIN TNH PH PHM T CY AY
LM VT LIU X L MT S KIM LOI N O C
: K thut mi trng
: 60520320
LUN VN TH S KHOA HC
NGI HNG DN KHOA HC: PGS.TS. QUANG HUY
H NI 2015
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L I CM
Li u tin, vi lng bit n v s knh trng su sc, ti xin chn thnh
cm n PGS.TS. Quang Huy, B mn Cng ngh Mi trng, Khoa Mi trng,
Trng i hc Khoa hc T nhin giao ti v trc tip hng dn, tn tnh
gip ti trong sut qu trnh thc hin lun vn. Cm n thy rt tm huyt
ch dn v gp ti hon thnh lun vn ny.
Ti xin chn thnh cm n cc thy c thuc B mn Cng ngh mi trng,
B mn Th nhng v mi trng t, Khoa Mi trng, Trng i hc Khoa
hc T nhin, i hc Quc gia H Ni to mi iu kin thun li ti c th
hc tp v lm vic trong sut thi gian nghin cu.
Ti xin cm n ti ThS. Bi Trung Thnh, Trung tm Nghin cu cng ngh
x l mi trng, B Quc phng cng tc trong qu trnh thc hin ti.
Ti cng xin gi li cm n ti gia nh, bn b lun quan tm ng vin v
ng gp kin gip ti trong sut qu trnh hon thin lun vn.
Xin chn thnh cm n!
H Ni, thng nm 2015
Hc vin
Phm Th Dinh
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MC LC
LI C N ............................................................................................................. i
DANH MC BNG ................................................................................................. iv
DANH MC HNH NH ........................................................................................ iv
DANH MC CH VIT TT................................................................................ vii
M U ..................................................................................................................... 1
Chng 1 TNG QUAN ....................................................................................... 3
1.1. X l kim loi n tro c bng vt liu c ngun gc thc vt ............... 3
1.1.1. Hin trng nhim kim loi nng trong nc ................................................. 3
1.1.2. X l kim loi nng trong nc bng sinh khi thc vt ................................. 5
1.2. c im sinh hc ca c a ........................................................................ 22
1.3. Tnh hnh sn xut a tr to t gii ......................................................... 23
1.4. Cc mi trng ca c a v sn phm t a ........................... 25
1.5. Tim s dng ph phm c a l m vt liu x l nhim mi trng
.......................................................................................................................... 27
Chng 2 - I V PH PHP HI CU ...................... 30
2.1. i tng nghin cu......................................................................................... 30
2.2. P p p i cu .................................................................................... 30
2.2.1. Phng php bin tnh vt liu ....................................................................... 30
2.2.2. Xc nh c tnh c bn ca vt liu ............................................................. 34
2.2.3. Kho st kh nng hp ph ion kim loi nng ca vt liu bin tnh........ 36
Chng 3 - KT QU NGHIN CU V THO LUN ................................. 37
3.1. c t c bn ca bt t a ....................................................................... 37
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3.1.1. c im hnh thi b mt ca bt thn ay .................................................. 37
3.1.2. c im cu trc ca bt thn ay ............................................................... 38
3.1.3. c im lin kt, nhm chc ......................................................................... 39
3.2. Quy trnh bin tnh to vt liu amidoxime ha t bt t a ....................... 40
3.2.1. X l bng dung dch NaOH ........................................................................... 40
3.2.2. ng trng hp ghp acrylonitrile ln bt thn ay bng h khi mo natri
bisunphit/amoni pesunphat (SB/APS) ............................................................ 45
3.2.3. Phn ng amidoxime ho ................................................................................ 52
3.3. c tnh ca vt li bin tnh ....................................................................... 56
3.4. Kh x l kim loi nng (Cu2+
, Zn2+
, Ni2+
) ca vt li bin tnh ....... 60
3.4.1. Xc nh gi tr pH x l ................................................................................. 60
3.4.2. Xc nh cc h s hp ph ca vt liu bin tnh vi cc ion KLN ......... 60
3.4.3. Xc nh thi gian lu ti u cho qu trnh x l ion KLN (Zn2+
, Ni2+
, Cu2+
)
bng vt liu bin tnh ............................................................................... 65
KT LUN V KHUYN NGH ......................................................................... 67
TI LIU THAM KHO ...................................................................................... 69
PH LC ................................................................................................................. 76
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DA H MC B
Bng 1. N kim loi n tro c thi ca mt s c s sn xut ............... 4
Bng 2. Di tc , s t v s l a t ca tnh Long An ....................... 24
Bng 3. Di tc , s t v s l a c ca tnh Long An ..................... 25
Bng 4. Thnh ph di dng c trong cc b phn ca c a ......................... 26
Bng 5. ng ca cc iu kin phn n kh p AN l bt thn
a ................................................................................................................ 33
B 6. P p p xc nh mt s tnh cht vt l, ha hc ca vt liu .......... 35
Bng 7. Kt qu xc d lng hp ph ca vt liu ..................................... 61
Bng 8. Cc h s hp ph ng nhit ca vt liu vi Zn2+
, Ni2+
v Cu2+
.............. 63
DA H MC H H H
H 1. c ph hy enzym ca kim loi nng ..................................................... 3
Hnh 2. Cu trc vch t bo v mt ct ngang vi si ................................................. 6
Hnh 3. Cu trc ca phn t cellulose ....................................................................... 7
Hnh 4. Cu trc phn cp ca cellulose ..................................................................... 7
Hnh 5. Vng tinh th v v v nh hnh ca cellulose ......................................... 8
Hnh 6. Cu trc ha hc ca cc hp cht chnh ca hemicellulose ......................... 9
Hnh 7. Cu trc ha hc ca lignin .......................................................................... 10
Hnh 8. Phn ng este ha gia cellulose v axit xitric ............................................ 17
H 9. S cc p p p bin tnh polyme .................................................... 18
Hnh 10. Cc nhm chc ghp ni vo cellulose to vt liu c nhi c tnh tt.......21
H 11. a (Hibisc s a abi s) ................................................................. 23
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Hnh 12. T trng sn xut a tr t gii ............................................................ 24
Hnh 13. V tr cc nh nhiu x c tr ca cellulose I (a) v cellulose II (b)
trong ph nhiu x tia X ............................................................................ 31
Hnh 14. nh SEM b mt bt t a ................................................................... 37
Hnh 15. Ph nhiu x tia X ca bt t a ........................................................... 38
Hnh 16. Ph hp th hng ngoi ca bt t a .................................................. 39
Hnh 17. ng ca n NaOH n khi lng cn li v m lng
cellulose trong bt t a ....................................................................... 40
Hnh 18. Ph nhiu x tia X ca bt t a ba u v x l cc n dung
dch NaOH khc nhau ................................................................................ 41
Hnh 19. S bi i ch s tinh th ca cellulose trong bt t a k i x l vi
dung dch NaOH cc n khc nhau ............................................... 42
Hnh 20. Ph hp th hng ngoi ca bt t a ba u v x l cc n
NaOH khc nhau ........................................................................................ 43
Hnh 21. ng ca t l SB/APS n kh p AN l bt t a .... 46
Hnh 22. ng ca tng n h k i m o n kh p ca AN ln
bt t a ................................................................................................ 48
Hnh 23. ng ca t l khi l AN/a n kh p AN ln bt
t a ...................................................................................................... 49
Hnh 24. ng ca thi gian phn n kh p AN l bt thn
a .............................................................................................................. 50
Hnh 25. ng ca nhit n kh p AN l bt t a ............ 51
Hnh 26. ng ca n NH2OH.HCl ....................................................... 52
Hnh 27. ng ca nhit phn ng ............................................................. 53
Hnh 28. ng ca thi gian phn ng ............................................................ 54
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Hnh 29. Quy trnh bin tnh to vt liu amidoxime ha t bt t a ............... 55
H 30. c im hnh thi b mt ca bt t a ba (a), a x l bng
NaOH 15% (b), a p AN (c) v vt li bin tnh (d) .............. 56
Hnh 31. Ph hp th hng ngoi ca bt t a ba u (a), sau x l NaOH
15% (b) v ghp AN (c) ............................................................................. 57
Hnh 32. Ph hp th hng ngoi ca vt liu .......................................................... 58
Hnh 33. Th zeta ca bt t a ba u, sau x l NaOH 15% v vt liu ....... 59
H 34. in tch m b mt ca vt li bin tnh cc pH khc nhau ................. 60
H 35. P tr p ph ng nhit Freundlich (a) v Langmuir (b) ca vt
liu vi Zn2+
, Ni2+
v Cu2+
......................................................................... 62
Hnh 36. Phn ng to phc gia vt liu amidoxime ha v ion Cu2+
................... 64
Hnh 37. Cc phn ng to thnh vt liu amidoxime ha v phn ng to phc gia
vt liu vi cc ion KLN ............................................................................ 64
Hnh 38. Phc cht gia hai nhm chc amidoxime v ion KLN ............................ 65
Hnh 39. Hiu sut x l kim loi (Zn2+
, Ni2+
, Cu2+
) theo thi gian ca vt liu ..... 66
file:///J:/MAST%20DINH/Mast%20-%20Dinh%20-%2012.1.16.%20final%20%20m,.doc%23_Toc440369513
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DA H MC CH VI
AAS : P p p p tch ph hp th nguyn t
AN : Acrylonitrile
FTIR : P p p p tc p hp th hng ngoi
KLN : Kim loi nng
PAN : Polyacrylonitrile
R/L : T l rn/lng
SEM : Knh hi vi in t qut
TCVN : Tiu chun Vit Nam
v/p : Vng/pht
X-ray : P p p iu x tia X
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M U
Qu trnh cng nghip a t a tr thnh nhn t tch cc i vi
pht trin kinh t x hi ca t c. Tuy nhin, bn cnh nhng li ch m n
mang li, s ia t cc ot ng cng nghip cn sn sinh rt nhiu cc cht thi
c c t cao, tc ng tiu cc n sc khe co i v h sinh thi.
Kim loi nng (KLN) v nhng hp cht ca c c bit cc
cht c tn ti l d i tro mi trng v c kh tc l tro c t sinh
vt. dng vt, chng c th l cc nguyn t vi lng rt cn thit c o c t con
i. Tuy nhin, khi n cao, cc ion KLN li c t c, c th gy ri ro
l d i co i v h sinh thi. Nh tc ng cp tnh do KLN t ng biu
hin nhanh khi tip xc v t ng gy t t n h h hp, tim p nhanh,
suy thn v thm ch gy t vong. Khi nhim v o c th, KLN tch t trong cc m
v gy ra nhng bi i.
C nhi p p p x l c thi cha KLN p p p kt ta
ha hc, trao i io , in ha, hp ph sinh hc, c p p p u c
c im v phm vi ng dng khc nhau. Tuy nhin, cc cng ngh ny yu
cu phi b sung ha cht nn gy nhim th cp hoc gi thnh cao. V vy, vic
lm cp thit l tm ra p p p x l hiu qu v kinh t .
Vic nghin cu s dng cc vt liu t i x l KLN tro c rt
c quan tm trn th gii. l ng nghin cu nhm to ra p p p x
l in, thn thin vi mi trng v b sung t ha cht v gi thnh ph hp.
Vit Nam l mt c c t trng sn xut nng nghip cao, lng ph phm d
tha trong qu trnh ch bin cc sn phm nng nghip l rt ln. Cc ph phm
t ng b b li, thm c l t ngay ti rung gy hu qu nghim tr n
mi trng v n cc v nhn sinh x hi khc.
Vit Nam, khng c nhiu nghin cu v ti ch ph phm nng nghip,
tro c p phm t c a to ra vt liu x l KLN tro c.
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p v o ng nghin cu tim , ti c n v thc hi ti Nghin cu
bin tnh ph phm t cy ay lm vt liu x l mt s kim loi nng trong nc.
ti c tin hnh vi cc mc c bin tnh ph phm t c a x
l mt s ion KLN (Cu2+
, Ni2+
, Zn2+
) tro c. Ni dung nghin cu tp trung
vo mt s v sau:
- Kho st cc yu t nh hng n qu trnh bin tnh bt g thn cy
ay theo phng php amidoxime ha,
- Kho st cc c tnh c bn ca bt thn ay v vt liu bin tnh,
- nh gi kh nng x l KLN (Cu2+, Ni2+, Zn2+) trong nc ca vt liu
bin tnh.
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Chng 1 QUA
1.1. X l kim loi nng trong nc bng vt liu c ngun gc thc vt
1.1.1. Hin trng nhim kim loi nng trong nc
Thut ng kim loi nng ch nhng nguyn t kim loi c t trng l 5
g/cm3. Kim loinng tn ti tro c c ngun gc t nhin v nhn to. Theo
ngun gc t nhin, kim loi n i v o tro c do qu trnh phong ha. Bn
cnh qu trnh t nhin, hot ng ca co i p mt ph k gy
nn nhim kim loi n . Tro , c thi t cc k d c, l , s
dng phn bn ha hc, thuc bo v thc vt trong nng nghip, hot ng khai
k o , c thi cng nghip l nhng ngun gy nhim c . c bit, tnh
trng nhim KLN do c thi cc ngnh cng nghip a l mt v mi
trng trn th gii. Cc kim loi ng (Cu), niken (Ni), ch (Pb), thy ngn
(Hg), crom (Cr) v km (Zn) l nhng kim loi t c c tro c thi.
Kim loi nng khng phn hy sinh hc, k c khi dng nguyn t t do
im cho sinh vt sng khi dng cation do kh n kt vi
cc chui cacbon ngn. Mt s kim loi n c tm th tro c t v thit
yu vi sc khe ca co i st, km, ma a , ng, ... Tuy nhin, mc
tha cc nguyn t thit yu ny c th nguy hi i sng sinh vt. Cc kim loi
n t ng tch t tro c, t, trm tch v sinh vt; gy nhim mi trng,
i sng ca cc loi sinh vt v sc khe co i.
V mt sinh ha, cc kim loi nng c i lc vi cc nhm -SH- v nhm -
SCH3- ca cc e z m tro c t (Hnh 1). V th cc enzym b mt hot tnh v
lm cn tr qu trnh tng hp protein ca c t .
Hnh 1. C ch ph hy enzym ca kim loi nng
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Bng 1. Nng kim loi nng trong nc thi ca mt s c s sn xut [4]
TT K hiu mu Ni
(mg/L)
Zn
(mg/L)
Cu
(mg/L)
Cr(III)
(mg/L)
Cr(VI)
(mg/L)
Pb
(mg/L)
Fe
(mg/L)
1 N1 5,9 7,2 61,2 68,1 71,5 109,5 - 2282,4 24300,0 0,8 1,9 121,1 159,1
3 N2 - 38,5 - - - - -
4 N4 16,9 - 1,89 - - 0,3 0,75
5 N5 73,4 75,5 - - - - - -
6 N6 - 131 - - 2,24 9,8 1,5
7 N7 21,23 12,54 - 116,2 42,4 12,5 -
8 N8 2,29 64,64 - 18,7 - 3,2 -
9 N9 8,17 10,52 - - - - -
10 N10 - 76,5 - - 15,98 - 40,21
QCVN 40:2011/BTNMT ct B 0,5 3 2 1 0,1 0,5 5
Ghi ch:
N1: Cng ty TNHH KYB Vit Nam, c thi b m (12/10/2009)
N2: Cng ty TNHH sn xut ph t t xe m VAP H Y , c
thi trc h thng x l (7/12/2004)
N3: Cng ty OMIC Hi D , c thi c a x l (22/11/2006)
N4: Khu cng nghip Ni B i, c thi ti cng chung (9/11/2005)
N5: Cng ty TNHH Khi H , c thi cng chung (27/9/2003)
N6: s m T Q a x T a T , H T , H Ni (28/10/2003)
N7: s m Tr V Hng x Thanh Thy, H Ty, H Ni (28/10/2003)
N8: Lng St, Hi D , c thi sau cng on ra m (11/11/2003)
N9: Cng ty m i S T , c thi m km (24/3/2003)
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Cc lng ngh ia c c k , c, m, ti ch v ch tc kim loi c lng
c thi khng l , li cha nhiu kim loi n Z , Fe, r, Ni,...
N cc kim loi n 2+
, Pb2+,
As2+
, Cd2+
, Hg2+
tro c h Thanh
Nhn v h Trc Bch, H Ni vt TCVN 6774:2000 v Cht l c - Cht
l c ngt bo v i sng thy sinh [5].
ng v cc hp cht ca c c c coi l cht c i vi ng vt,
c bit l vi c. i vi thc vt, c coi l nguyn t c bn cn thit cho
s pht trin ca cy tr tro mt s trng hp n li l nhn t c
khi n tro c kho 0,1 m /L. i vi c t i, n ng trong
c ung kho 3 m /L c t vi m v s ng thc qun, nn ma,
thn kinh co git, mch yu, [6].
Km tn ti tro c dng ha tan s rt nguy him n sc khe con
i. Khi ng c km s b a bng, mch chm, co git. i vi cc loi thy
sinh, n Zn2+
bng 0,3 mg/L s gy cht mt s lo i c c ngt [4].
N Ni2+
cao t p i, mi v x . N im c Ni2+
cp tnh
a u, chng mt, bu v a c, kh th, tiu chy, ph thn, vim
da, [4]
c p g php ph bi x l kim loi n l p p p i ma,
trao i io , in phn, kt ta, sinh hc, hp ph bng than hot tnh, Hu ht
cc p p p c c i p cao v t ng c hiu qu khi n ion kim
loi thp. P p p p ph loi b cc ion kim loi tro c c xem l
p p p iu qu cao v chi ph thp [36]. Cc cht hp ph c th l khong
cht, cht h c oc c ngun gc sinh hc.
1.1.2. X l kim loi nng trong nc bng sinh khi thc vt
1.1.2.1. c im ca nguyn liu sinh khi thc vt
Sinh khi thc vt (vt liu lignocellulose) l polyme cacbo irat phc tp,
c thnh phn chnh l cellulose, lignin v hemicellulose [23]. Vt liu
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lignocellulose c th tm thy trong cht thi nng nghip, nng nghip v cng
nghip m ca, b ma, giy vn, c, thn v l cy, v tru, ng, ...
Lignocellulose l phn chnh hnh thnh nn vch t bo thc vt. Lin kt gia
cellulose, hemicellulose v lignin qua lin kt este v ete lm cho sinh khi c tnh
bn vng [31]. Cc vi si cellulose c bao quanh bi hemicellulose to thnh
mt m li m, m khong khng gian tr c lp y bng lignin (Hnh 2).
Hnh 2. Cu trc vch t bo v mt ct ngang vi si
Cc thnh phn ca sinh khi khc nhau ty thuc v o cc lo i v iu kin
mi trng sng. Thnh phn trung bnh tnh theo tr lng ca ba polyme sinh
hc sa : cellulose (30-50%), hemicellulose (19-45%) v lignin (15-35%) [31].
Cellulose l hp cht h c c c t c cu to (C6H10O5)n v l mt
polyme mch thng ng nht gm cc phn t glucose lin kt vi
nhau bi lin kt -1,4-glicozit v lin kt hydro ni phn t v gia cc phn t
[34]. Mi v lp li trong cellulose cha hai phn t anhydroglucose (AGU).
Mi v lp li c mt nhm hydroxyl (OH) chnh cc v tr cacbon 6 (C6) v
hai nhm hydroxyl th cp ti v tr 2 v 3. v lp li th hai xoay 180o
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trong mt phng (Hnh 3). Cellulose c nhi m a c hydrox l t ta
tro c do lin kt ni phn t v lin phn t mnh.
Hnh 3. Cu trc ca phn t cellulose
trng hp ca cellulose l 300 - 1700 vi si g; 800 - 10000 vi cotton,
si thc vt v cn ph thuc vo cellulose gc a q a x l [23].
Hnh 4. Cu trc phn cp ca cellulose
Cc si cellulose nm thnh t bo thc vt v c to nn bi cc vi si
(Hnh 4). Cc b vi si cha 30 - 40 mch cellulose t eo cc ng khc nhau v
c hnh thnh bi cc i phn t cellulose dng tm [33]. Cc mch cellulose
c lin kt vi nhau nh lin kt hydro v lin kt Van Der Waals. Do thiu
chui bn hoc chui nhnh, cellulose l mt polyme bn tinh th, cha c pha tinh
th v p a v nh hnh [28] (Hnh 5). Lin kt hydro gia cc chui cellulose v
lc Van Der Waals gia cc phn t glucose d n s hnh thnh vng tinh th.
Trong vng tinh th, cc phn t cellulose lin kt cht ch vi nhau, vng ny kh
b tn cng bi enzym c a c t. Ch c cc mch cellulose trn b mt cc
vi si l d dng tip xc vi ha cht. Do , p n ng thy phn ca cellulose l
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rt thp [31]. N c li, tro v v nh hnh, cellulose lin kt khng cht vi
nhau nn d b tn cng [14]. t k p n ng ca cellulose, cc vng
tinh th ca cellulose c c chuyn sang d v nh hnh. Vi mc c ,
mt s qu trnh thy phn b p p p a c c nghin cu.
Vng v nh hnh
Vng tinh th
Hnh 5. Vng tinh th v vng v nh hnh ca cellulose
Cellulose c hai dng tinh th l cellulose I v cellulose II [28]. Cellulose I
c cc chui cellulose sp xp song song vi nhau, trong khi cc chui cellulose II
i song vi nhau. Cc d v nh hnh ca cellulose l dng III v dng IV.
Cellulose I t ng c trong cellulose t nhin. Trong cellulose I c hai loi lin kt
hydro: lin kt hydro ni phn t v gia cc phn t [28]. Lin kt hydro ni phn
t gm hai loi: O-2-HO-6 c di lin kt l 2,707 v O-3-HO-5 c di
lin kt l 2,802 . Lin kt hydro lin phn t gia C6-OH v C3 (O6 - HO3) c
di lin kt 2,874 [49]. Cu trc ny rt bn nhit v c th c chuyn sang
cc dng cellulose khc [28, 14]. Cu trc tinh th ca cellulose I c th chuyn
sang dng cellulose II thng qua qu trnh x l bng kim.
Hemicellulose l mt polysaccarit c tnh cht ha hc khc nhau gia cc
loi thc vt, c hnh thnh bi pentose (xylose, rhamnose v arabinose), hexose
(glucose, manose v glactose) v cc axit uronic (4-Omethyl-glucuronic, v
galacturonic) [34]. Xylan polyme l loi polyme ph bin nht trong hemicellulose.
Hemicellulose bao hm cc lin kt (1-4) khng phn nhnh ca xylan hoc
mannan, chui xon c li kt (1-3), chui p li kt (1-4)
galactoglucomannan (Hnh 6). Kt qu hnh thnh chui polyme phn nhnh m
ch yu gm cc mo ome m cacbo (x lose) v ng su cacbon
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(glucose). Hemicellulose khng c cu trc tinh th, cu trc phn nhnh cao v c
cc nhm axetyl kt ni cc chui polyme vi nhau [23].
a) Xylan
b) Glucomannan
Hnh 6. Cu trc ha hc ca cc hp cht chnh ca hemicellulose
Hemicellulose k a ta tro c nhit thp. Tuy nhin, qu
trnh thy phn ca cao so vi cellulose [23]. Hemicellulose tan nhi
trong dung dch axit. H m lng hemicellulose trong g mm v g cng khc nhau
k. Hemicellulose lm gim kh tip cn cellulose, do , cn phi tch
ti thiu 50% hemicellulose t k ca cellulose [34]. So vi cellulose,
hemicellulose d dng b thy phn trong axit long, kim hoc e z m. Do nhy
nhit cao, qu trnh thy phn hemicellulose to ra cc sn phm ph khng mong
mu f furan v hydroxymetyl fufuran.
Lignin l mt hp cht c cu trc phn t phc tp cha polyme lin kt
ngang ca cc p p e olic, c bit l p-coumaryl ancol, coniferyl ancol,
sinapyl ancol (Hnh 7).
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Hnh 7. Cu trc ha hc ca lignin
Li i c vai tr mt mng bo v tnh thm ca t bo v c n s
xm nhp ca vi khun. V c bn, cc loi thc vt g mm cha m lng lignin
cao so vi cc loi sinh khi thc vt k c, do q tr tc cellulose t
thc vt g mm t k k so vi cc sinh khi k c. Do , loi b
lignin cn phi thc hin cellulose v hemicellulose c tip xc vi dung
dch x l [31].
Vt liu lignocellulose l ngun ti nguyn ti to, c th s dng trc tip
hoc gin tip sn xut cc kh sinh hc hoc cht ha hc, vt liu x l [3].
Mt cht hp ph c coi l c chi ph thp nu n phong ph trong t nhin v l
ph phm nng nghip, cng nghip [47]. Ngun cht thi t sinh khi thc vt c
gi tr kinh t thp. Tuy nhin, cc ng dng ca ngun ti nguyn ny b hn ch
bi lin kt cht ch gia ba thnh phn chnh ca thnh t bo l cellulose,
hemicellulose, lignin.
-
11
1.1.2.2. s ca p p p
Ph phm nng nghip t ng gm cc thnh phn cellulose, hemicellulose,
lignin, lipid, protein, cc loi , ti bt, c, hidrocacbon, tro. Nhng
vt liu ny c kh p ph kim loi nng nh cu trc nhiu l xp v thnh
phn gm cc nhm chc hot ng [3]. Cc nhm chc trong sinh khi bao gm
nhm axetamido, cacbonyl, phenolic, khung polysaccarit, amin, sunphua hydryl,
cacboxyl, ru v este [19]. Cc nhm ny to i lc v to phc vi ion KLN. Mt
s vt liu hp ph lin kt khng chn lc, c th lin kt vi nhiu ion KLN.
Trong khi, cc vt liu khc lin kt chn lc ion KLN ph thuc vo thnh phn
ha hc ca chng. Cc ph phm x da, tru, b ma, l c c , c d
x, t c , thn cy chui, v tr , t c ,... c nghin cu
nhm pht hin kh tc kim loi n tro c.
Trao i io l c c quan tr i vi qu trnh x l ion KLN bng thn
c o c tm thy trong nghin c c b [25]. Sau khi hp ph Cu2+
,
Ni2+
, Pb2+
v Cd2+
, kt qu phn tch cho thy cation Ca2+
, Mg2+
, K+
v H+
c
tch ra khi vt liu c t l g t vi ion kim loi c x l. iu
ny chng t cc ion KLN t a t v tr ca cc cation khc trong vt liu.
P tr p n trao i io sa :
S M2/n + Me2+
S Me + (2/n) Mn+
(1)
Tro , S l v tr lin kt, Mn+
i din cho ion K+, Mg
2+, Ca
2+ v Me
2+
i din cho cc ion KLN.
C d x cha phn h c c yu l lignin, cellulose v mt s nhm
chc phn cc [52]. Nhng nhm chc ny c kh trao i cation hoc to
lin kt ha hc. Phn ng hp ph trao i gia Cu v sinh khi d x c th
biu di t eo p tr sa :
2(TF)- + Cu
2+ Cu(TF)2 (2)
2H(TF) + Cu2+
Cu(TF)2 + 2H+ (3)
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12
Tro , (TF)- v (TF) l nhng v tr phn cc c th t tc vi cc ion
kim loi trn b mt vt liu t sinh khi d x.
Ion KLN tn ti mt s dng trong dung dc e2+
, MeOH+,
Me(OH)2, Cc ion kim loi tn ti trong dung dch axit cc dng cation.
Trng hp , c c ch y l trao i ion. Ti pH cao, cc ion kim loi s kt
ta, do , iai o , c c hp ph b mt chim t . c c c ny
c th hin qua cc p tr sa [10]:
2(R-COH) + Me2+
(R-CO)2Me + 2H+ (4)
R-COH + MeOH+ R-COMeOH + H
+ (5)
2R-COH + Me(OH)2 (R-COH)2Me(OH)2 (6)
Tro , R l cc gc trong vt liu.
N c , c c hp ph ion KLN bng ph phm nng nghip da trn
phn ng ha hc gia cc nhm chc trn b mt cht hp ph v ion kim loi.
Phn trao i cation v phn ng to phc vi ion kim loi l ch yu. Bn
cnh , cc c c xy ra km theo bao gm hp ph b mt, khuch tn, kt ta.
im ca vic s dng ph phm nng nghip x l c thi bao
gm k thut in, kh p ph tt, hp ph chn lc ion kim loi nng,
chi ph thp, tnh sn c v d dng ti sinh. Tuy nhin, vic p dng cc cht thi
t sinh khi thc vt c a c x l c th mang li mt s v l m t
OD, BOD c TO tro c do s ha tan ca cc cht h c d ha tan
trong thc vt [47]. S ia t OD, BOD v TOC ca c c th gy ra s suy
gim oxi tro c, d e da i sng th si . Do , vt liu c
ngun gc thc vt c c x l trc khi hp ph kim loi nng.
1.1.2.3. Mt s p p p iu ch vt liu t sinh khi thc vt
Trong nh m , vic s dng ph phm nng nghip c c
bit quan tm, nhiu nghin c c tin hnh nhm tm ra p p p c n
cc ph phm ny thnh vt liu c ch. Tro , ng nghin cu s dng ph
-
13
phm nng nghip lm vt liu x l KLN tro c l mt trong nh ng c
tim ng dng nht.
Sinh khi thc vt c cellulose c a bin tnh c kh p ph
kim loi nng thp v tnh cht vt l khng nh. khc phc nh im hn
ch ca sinh khi t , cc p p p bi t c p d nng cao hiu
qu x l KLN. Mt s nhm p p p c s dng nhiu nht c phn loi
sa : p p p vt l (xay v nghin, nhit); p p p a c (bin tnh
bng kim, axit, tc nhn oxi ha, dung mi h c); p p p si c; t hp
ca p p p vt l v p p p a c (qu trnh t thy phn, oxi ha
t).
P p p si c c p d phn hy mt phn vt liu
lignocellulose bng cch s dng cc vi sinh vt phn hy lignin v hemicellulose
m v vi khun. im ca p p p l tin hnh d dng v tn t
lng. Tuy nhin, qu trnh phn hy sinh hc din ra chm v cn p dng
t m cc p p p vt l, ha hc k c p p p i c c. Cc
p php vt l in, chiu x, nhit c c p d bi i
tnh cht ca sinh khi thc vt. P p p i l m t din tch b mt v
gim tinh th ca cellulose. P p p c iu x nhm ph v cc lin kt
hidro trong cu trc tinh th ca cellulose b lng bc x. Tuy nhin,
p p p cu phi cung cp lng l . c p p p a c
s dng cc cht ha hc bin tnh vt liu. Mc c ca p p p l
th p emicell lose, li i ng thi t m lng cellulose trong sinh khi
thc vt. P p p bin tnh kt hp p p p vt l v p p p a
hc t c p d v c coi l p p p tt nht.
Hai p p p bin tnh sinh khi thc vt thnh vt liu t c p
dng v nghin c l p p p c to than hot t v p p p bin tnh
b mt.
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14
a) Ch to than hot tnh
Than hot t c s dng rng ri trong x l cc cht nhim h c v
cc ion kim loi n thp. Cacbon trong thc vt c chuyn ha thnh
cacbon hot ha nhit cao. Than hot tnh c thnh phn ch yu l cacbon
(85-90%), cn li l cc hp cht v c dng tro (5-15%). Than hot tnh c cu
trc l xp. Din tch b mt trong cc l xp chim phn ln tng din tch b mt
ca cacbon [12].
Cht thi nng nghip l ngun nguyn li p o p sn xut than hot
t do c m lng tro thp v cng ph hp [24]. Do , bin tnh cc cht
thi nng nghip thnh than hot tnh l mt gii php gii quyt v mi trng
v gim chi ph ch to than hot tnh. Than hot t c ch to t cht thi rn
nng nghip m ca, c t thi cao l , li ng, b ma, tr , x da,
c s d loi b KLN v x l cht thi dt nhum tro c [12]. Than
hot tnh ch to t ph ph phm nng nghip c hiu qu kinh t cao trong x l
c thi do ngun nguyn liu di do, gi thnh r.
b) Bin tnh ha hc
Mc tiu quan trng ca bin tnh bng cc cht ha hc l to ra b mt m
in hoc i tc d trn b mt ca vt liu [44]. iu ny lm cho
kh p t keo tt v iu ch c tnh b mt ca vt liu.
Cc chui cellulose cha mt nhm hydroxyl chnh v hai nhm hydroxyl
th cp. Cc nhm chc hot c gn vo cc nhm hydroxyl bng cc cht
ha hc [18]. c p p p bin tnh ha hc chnh bao gm: este ha bng axit
h c, oxi a bng cc tc nhn oxi ha, thy phn bng dung dch kim v ghp
cc monome ln sinh khi thc vt. c p p p bin tnh sinh khi thc vt
c th tc c cc hp cht h c a ta v cao iu qu to phc vi
KLN [36]. Lignin c cha nhiu nhm chc drox l t do, nhm metoxyl,
nhm cacbonyl v ni i, do , c t tham gia cc phn oxi a l m t
mch cacbon to thnh axit bo v v t m. c d lignin c kh bn nhit
-
15
tt, nng chy nhit 140 - 160 , d b s im b do tia t oi.
V t m trc k i c to vt li c p i x l si loi b li i .
Hemicellulose c c trc c v , o i ra c mt t t ti v
ti t ca cellulose. V v , d b t p tro d dc axit, d b trc l
k i si tro d dc kim lo , d p p m, c k t p di
tc d ca vi k v l m s im b it ca vt li , t c t c c
km, k b . Bin tnh ha hc khng nhng loi b lignin, hemicellulose m
cn lm gim m lng tinh cellulose tinh th v t xp ca b mt vt liu.
c iu nghin cu v p p p bin tnh vt liu bng cch s dng cc
tc nhn bin tnh k c a cc d dch kim (NaOH, Ca(OH)2, Na2CO3),
cc axit v c (H l, H2SO4, HNO3), cc axit h c (axit tartaric, axit xitric) hay
cc hp cht h c (meta ol, focmalde t), cc tc nhn oxi ha (H2O2, phn ng
Fe to ) x l cc cht h c a ta , mu v hp ph kim loi nng trong
c. Tc nhn bin tnh l m t t ot ng ca b mt vt liu do gn thm
cc nhm chc c kh kt hp vi kim loi nng, loi b cc cht h c d
ha tan c sn trong vt liu.
Bin tnh bng dung dch axit v c
Bin tnh bng dung dch axit l qu trnh ph v cu trc bn vng ca vt
liu lignocellulose. Ion H+ ph v lin kt ni phn t v lin kt gia cc phn t
vi nhau gia cellulose, hemicellulose, lignin trong sinh khi [31]. c axit c
H2SO4, HCl, H3PO4 v HNO3 c p d thy phn sinh khi. Cc nhm
hydroxyl trn cellulose vai tr q a trng v kh trao i ion ca vt liu
lignocellulose. Bn thn nhm ny ny c kh trao i yu v lin kt OH
phn cc khng mnh. Nhiu bin php bi t c cng b oxi a cc
nhm hydroxyl thnh cc nhm chc axit hoc sunfo ha bng axit sunfuric [3].
Tuy nhin, cht thi t qu trnh bin tnh bng axit c c x l do c t c
hi, m . Hu ht cc p p p bin tnh sinh khi thc vt b axit v c
u s dng dung dc axit lo axit H2SO4, HCl v HNO3. Cc axit long c
hiu qu v mt c i p v mi trng. Nhn chung, axit long (H2SO4 < 4%)
-
16
c th ha tan hu ht hemicellulose [31]. Dung dch axit H2SO4 lo l m t tc
phn ng thy phn cellulose. Axit m c l tc nhn oxi ha mnh cho qu
trnh thy phn cellulose c t m v p i thu hi. M ca c x
l bng HCl loi b c 92,4% Cu2+
pH 5, tro k i m ca c loi b c
47% [36]. Tuy nhin, trong mt s trng hp, x l v tru bng HCl li lm gim
kh p ph Cd2+
so vi v tru khng x l b axit. hp ph cc
KLN, b mt cc vt liu hp ph phi ma in tch m. Mc d bin tnh bng
axit lm gim m lng cht h c ca vt liu hp ph v t xp b
mt tc i d vi cc ion H+ c l m cn tr qu trnh hp ph. Khi v tru
c x l bng HCl, cc v tr hp ph trn b mt vt li c proton ha.
Bin tnh bng dung dch kim
Trong thnh phn si thc vt v g c cellulose, hemicellulose, lignin l cc
thnh phn ng l n tnh cht ca si. c c c ca q tr bi
tnh b kim l p v c trc li i tro si k i, l m t mc p
ca cellulose v hemicellulose c o cc bc x l tip t eo. Q tr t p
b d dc kim d d x ra ( it di 140 ) so vi cc p p p
bi t k c [31]. xp ca vt li t l sa k i d dc kim p v cc
li kt c o, to t m i ca axit cacbox lic v r . Vt li c bi t
b d dc kim c b mt m i do cc io H+ trong cc nhm hydroxyl,
cacboxyl, ... c s tr b mt vt li c tc ra tr a io OH- trong
d dc . i l im ca p p p bi t vt li b d dc
kim so vi cc p p p k c. Nhn chung, cc d dc NaOH v a(OH)2,
NH4OH t c s d c o q tr t p b kim.
Bin tnh bng axit hu c
Cc axit h c c tc dng este ha cellulose, g c d l r v v
c hot ha bng axit xitric u c mt s ia t k kh
loi b cc ion kim loi tro c [3]. Axit xitric u tin s chuyn thnh dng
anhydric, tip theo l phn ng este ha xy ra gia axit anhydric v cc nhm
-
17
hydroxyl ca cellulose. Ti v tr phn v x t hin hai nhm chc axit
(t axit xitric) c kh trao i ion. N t it hoc ko di thi gian
phn ng, qu trnh este ha c th tip tc x ra i vi cc nhm axit cn li ca
axit xitric lm gim kh trao i ion.
Hnh 8. Phn ng este ha gia cellulose v axit xitric
Nghin cu v qu trnh este ha bt li ng bng axit xitric cho thy, sau
khi este ha, din tch b mt ca cht hp ph t k [3]. Lng oxi c
tm thy trong vt li t cao do iu nhm oxi a c gn trn b mt vt
li , in hnh l nhm cacboxyl, phenolic v lactonic.
Bin tnh bng dung mi hu c
Bin tnh bng dung mi h c loi b lignin, hemicellulose ra khi vt liu
bng cch solvat ha, ha tan cc mnh v ca lignin, hemicellulose. Cc polyme
lignin d dng tan trong dung mi h c. Qu trnh solvat a c thc hin bi
cc lc gia cc phn t li kt hydro, lc ion-lng cc, lc lng cc, lc
lng cc-lng cc gy ra [36]. c d mi c s d bin tnh vt liu
-
18
c ngun gc thc vt t ng c nhit si thp meta ol, eta ol, axeton,
etylen glycol, etyl axetat. Ion OH- trong ancol s ph v lin kt axit-este trong
lignin, hemicellulose. H a, bin tnh bng dung mi h c c l m cellulose
tr l , do im lng cellulose tinh th. T i , p p p k
kh thi v mt kinh t v i i phi thu hi dung mi h c.
Bin tnh bng tc nhn oxi ha
Mt s tc nhn oxi a t c d bin tnh sinh khi thc vt
thnh vt liu hp ph bao gm ozon, hydropeoxit (H2O2), clo, H l, H lO, Cc
tc nhn oxi ha tham gia vo qu trnh ha tan lignin bng cch ph v cu trc
vng ca lignin. T t ng, tc nhn oxi a c s d h tr cho bin
tnh bng kim. Tro iu kin pH > 12, gc ( O2*) hnh thnh v m v t m
[31]. Lignin, hemicellulose b ha tan thnh axit cacboxylic (axit formic, axit
oxalic, axit axetic); tro k i , cellulose h k b phn hy.
Bin tnh sinh khi thc vt bng phn ng ng trng hp ghp
Hnh 9. S cc phng php bin tnh polyme
-
19
Mt s p p p bi i cc thuc tnh ca polyme bao gm pha
trn (blending), ghp (graft) v che ph (curing) [13]. Hn hp ca hai hay nhiu
monome c pha trn vt l vi a c c cc tnh cht cn thit l qu
trnh pha trn. Ghp l mt p p p tro monome c lin kt cng ha
tr vo chui polyme. Che ph l qu trnh bao ph ca mt lp p t ln mt
chui polyme bng cc lc vt l.
Q tr ng trng hp l qu trnh trng hp hai hay nhiu monome m
sn phm polyme sinh ra c cc mt xch monome sp xp ngu nhin (copolyme
ngu nhin), sp xp l p i n hoc cc mt xch monome khc nhau to
t cc on mch khc nhau trn polyme (copolyme khi) hoc polyme c
nhnh to ra t monome khc loi vi mch chnh (copolyme ghp). Khi trng hp
mt loi mo ome to nn mc v o mt loi polyme c sn, qu
trnh ny gi l ng trng hp ghp, sn phm ca qu trnh l copolyme ghp.
ng trng hp p l p p p t c s dng rng r i bin tnh
ha hc cc polyme t nhin v polyme tng hp. Phn ng trng hp ghp l
mt p p p t c s d bin tnh b mt pol me v t a i cc
thuc tnh vt l hoc ha hc ca polyme. Cc chui b c lin kt cng ha tr
vi trc pol me c hnh mt cht ng trng hp (copolyme). C hai loi
chnh ca p p p p ni l ghp ni vi mt mo ome v p ni vi
mt hn hp ca hai hay nhiu monome. Ghp ni vi mt mo ome t ng xy ra
trong mt bc duy nht, trong khi ghp ni vi hn hp monome c th xy ra
vic ghp ni tun t hoc ng thi hai monome.
P p p ng trng hp ghp cc monome khc nhau ln cellulose hoc
vt liu lignocellulose c p d x l c nhim mu, kim loi nng.
Bin tnh vt liu lignocellulose t nhin bng phn ng trng hp ghp cc
monome c cha nhm vinyl ci thi c mt s c im ca vt liu th
m v ca vt liu, tnh khng thm c, nh nhit, i, trao
i ion, hn ch s xm nhp ca cc vi sinh vt [29]. Qu trnh ghp cc monome
vinyl ln cellulose hoc vt liu lignocellulose t ng bao gm ba bc, (1) cc v
-
20
tr hot ng trn b mt pol me c si ra, (2) cc mo ome c thm vo phn
ng, (3) mo ome c ghp vo vt liu. Cc v tr hot ng trn mch cellulose
c to ra bi phn k i m o bng ha cht hoc bc x.
Phn ng trng hp ln cellulose ch y c thc hin trong mi
tr c v mi tr k ng nht. Tro c, cc vn v nh hnh
ca cellulose tr l , mch cellulose tr nn d tip cn, cc monome khuch
tn vo cc vng ny v ghp ln mch. Do , t iu qu ghp, vt li c
l m tr trc khi ghp hoc thc hin phn p tro mi trng c kh
l m cellulose tr l . K i tr p p l cellulose trong mi
tr k t, k tip c cc c t do tr cellulose v nhm
vi l l mt t am s q a tr xc i q p. c d, cellulose l mt
pol me t , t i , s i di ca cc v ti t v cc li kt dro
ia cc p t l m im k tip c [28]. Tro c, s tr ia
cc ti t ca cellulose x ra c l v v , v l m t
i q p. P tr p p x ra tt tr v v
ca cellulose do k tip c d d ca v . t i q p c
t t t l cellulose/mo ome, l m tr cellulose trc k i p , oc
ti p p tro mi tr l m tr cellulose. c p
php zn ha, oxi ha, bin tnh vi dung dch kim, c, ami c p d
ci thin kh tip cn ca cellulose. t , k tip c a k
p ca cellulose t k i m l ti t im, m l v
t . Tro q tr x l kim, cellulose c tr v trt t c trc b p
v. trc ti t ca cc c i cellulose so so ba c sp xp li
t cc c i i so so , do t cellulose II [48]. t i, m
l cellulose v t , li i , hemicellulose c c tc ra k i vt
li .
Ty thuc v o cc mo ome c ghp ln vt liu, cc thuc tnh ca sn
phm ghp s khc nhau. Nhn chung, cc nhm chc ph bi c s dng trong
p mo ome c th hin trn hnh 10 [44].
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21
Hnh 10. Cc nhm chc ghp ni vo cellulose to vt liu c nhiu c tnh tt [44]
B cc ng trng hp ghp ni cc monome, cc nhm chc mi c
to ra trn b mt vt liu. Tro , acrylonitrile l m mo ome c s dng
ph bin. Vt liu cellulose c ghp vi acrylonitrile v cc monome khc c
d x l cc ion kim loi nng Cd2+
, Cu2+
, Zn2+
, Cr2+
tro c [44]. Kt qu
cho thy, sn phm ghp nng cao kh li kt vi cc ion kim loi n
cellulose ba u, kh li kt ph thuc vo ion kim loi v c tnh ca vt
liu ghp.
Qu trnh ghp c th c thc hi tro mi tr ng nht hoc
k ng nht. K i ng trng hp ghp din ra tro mi tr k ng
nht, phn c tin hnh bi tc k i m o p hp [44].
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22
tng hp copolyme ghp ta c th d cc p p p: ng trng hp
gc t do, ng trng hp ion v mt s p p p k c. Cc k thut k i m o
cho qu trnh ghp bao gm ha cht, tia x, quang ha, plasma v ghp enzym.
Tro , k thut k i m o bng ha cht l p p p t c p dng
do chi ph thp v t c hi. Vai tr ca cht k i m o l rt quan trng v n quyt
nh cch thc ghp. Tro trng hp p t eo c c gc t do, cc h khi
mo khc a eri (IV) amo i itrat ( AN), m i pesunphat, tc nhn oxi
ha Fenton (Fe(II)-H2O2), KMnO4-axit oxalic, natri bisunphit/pesunphat l nhng
cht k i m o c s dng v nghin cu. So vi cc q tr k i m o k c,
k i m o t eo c c gc t do c im l c th tin hnh nhit phng v
t c hi.
1.2. c im sinh hc ca cy ay [7, 8]
a c tn khoa hc l Hibiscus cannabinus, thuc chi Hibiscus, h
Malvaceae (h Cm Qu), c khong 40 - 50 loi phn b khp vng nhit i v
cn nhit i. S a l loi si c sn xut v s dng nhiu th hai sau si
cotton. a p t trin tt trn t bi bi, t laterite, t vi vi cp ht t
ct tht n st tht, t kh vi pH t 5,5 - 6,5. a c t pht trin t 1,5 - 4,5
m, t c ng knh khong 1 - 2 cm. l loi cy ngn ngy, cho hoa ti 4
t trc khi ra ht vo cui t i ma. a p t trin kh hu nng v m
t vi khong nhit t 24 n 37C hoc c th cao . l loi cy kh
nhy vi nhit v nh sng nn n cn mt thi im thch hp gieo ht v
thu hoch. iu ki l tng th c th thu hoch sau 100 - 120 ngy k t ngy
gieo ht.
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23
Hnh 11. Cy ay (Hibiscus Cannabinus)
T c a bao m 2 dng si: si o i c gi l lp v libe v chim
khong 40% tr lng cht kh ca thn; si bn trong c mu tr c gi l
si t v c im khong 60% tr lng kh ca thn. Si t a rt chc, t
vi si g loi chc c s d sn xut cc loi giy khc nhau. Phn
th c a c o bt c x si ng , ng knh ln, t l di/r t x
si bt g cng. Thnh phn ha hc chnh ca c a bao m: cellulose (43 -
46%), pentozan (11 - 16%), lignin (21 - 29%) v tro (1,6 - 2,6%).
1.3. Tnh hnh sn xut ay trn ton th gii [7, 8]
i trng ngy cng nhim ch yu do s khai thc qu mc ti nguyn
thin nhin cng s bng n ca th trng sn phm tng hp, nguyn vt liu ti
sinh d c ch nhi cc quc gia pht tri v a p t trin. Si ay
tr nn quan trng bi cc c tnh ha hc vt l c t t i mi trng.
v Bangladesh l cc quc gia c s l a chim n trn 85%
ca ton th gii. Trung Quc, Myanmar v Nepal c trng v sn xut a . c
quc gia sn xut vi din tch nh l Vit Nam, Thi Lan, Indonexia v
Campuchia (Hnh 12).
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24
Hnh 12. T trng sn xut ay trn th gii
Vit Nam, din tch tr a ln nht l v o m 1987 vi quy m
31.956 ha v s lng 57.576 tn si t. N c , din tch v s l a c
x ng gim trong 3 thp k qua. Hi a , c a c trng ch yu ti Long
An. Di tc , s t v s l a t v a c Lo A c th hin
trong bng 2 v 3.
Bng 2. Din tch, nng sut v sn lng ay t ca tnh Long An
m Din tch
(ha)
ng sut ay t
(tn/ha)
Sn lng ay t
(tn)
2007 8.616 1,70 14,647
2008 1.708 2,01 3,433
2009 1.188 2,16 2,566
2010 2.799,4 1,91 5,347
2011 3.330 1,87 6,227
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25
Bng 3. Din tch, nng sut v sn lng ay cy ca tnh Long An
m Din tch
(ha)
ng sut ay cy
(tn/ha)
Sn lng ay cy
(tn)
2007 185,0 24,8 4.588
2010 127,5 40,0 5.100
2011 106,4 35,0 3.724
1.4. Cc nh hng mi trng ca cy ay v sn phm t ay [8]
a c k ng ha kh CO2, loi kh nh knh chnh gy nn bi i
kh hu. Ging cc loi c k c, a c s dng CO2 to ng. Trong 120
ngy ca k a a p t trin, mt ha cy tr a c t hp th khong 15 tn
CO2 t kh quyn v gii phng khong 11 tn oxi v cc cht khc. Cc nghin cu
c c o t y rng t l ng ho CO2 a l cao so vi cc loi cy khc
nhiu ln.
c tc mi trng ca sn xut a l t i so vi vic sn xut
si tng hp. N i tr a s dng s lng t cc loi phn bn ha hc v
thuc dit c. N s t a khong 5 - 10 tn cht kh mi m t. Khong 1 tn
cht kh t l c a tr li t v khong 3 tn r v c tro t. Cy a
ip t cng cht h c tro t do l rng tro ma si trng v ci thin
l di d tro t. a t c trng lun canh vi c l t c
k c o v cc loi cc, rau qu, ht c du, tt c s p thuc va
phi hoc nhiu vo cht di d c tro t, t ng khng tr li cho
t, ngoi tr tro trng hp cc cy h , a . P p p l ca
khng ch l m t sn xut nng nghip, m cn duy tr mc ph nhiu ca t
ch yu l thng qua phn hy ca l rng v cht thi h c t a .
a l mt cy tr m t och t nht mi m mt l . a l
mt loi cy l x, pht trin nhanh khi mt kho 4 t tr t . iu
-
26
c a l iu sut sinh hc ca si a l cao iu so vi cc cy ly
g, v do vic s dng si a t a c o d sn xut bt giy s lm
gim chi ph sn xut n mt mc l . N c s lm gim nhu cu cht cy
ph rng.
Trong nng nghip tr a , vic s dng phn bn, thuc tr su v thuc
dit c/thuc dit nm l hn ch. Mc dng phn ha hc cho tr c a l
t 7 - 53 kg cht di dng cho mi ha. S lng phn bn s dng nh ti mc
ng c th c coi l k k. C l r a rng khong 5 - 6
tn l cy trn mt hecta. Mi cy a c k ong 100 - 120 l, do ip im bc
i c t t. R a d i c k m x do ip di c n dinh
dng v lun canh cy tr k ai t c s t cao . L c rng sau khi thu
hoch rt i di dng, l ngun phn bn cho v ma tip theo.
Bng 4. Thnh phn dinh dng c trong cc b phn ca cy ay
B phn it (%) Pht pho (%) Kali (%)
L 2,85 3,60 0,85 1,20 2,50 3,10
Thn 0,17 0,25 0,21 0,28 0,50 0,82
R 0,35 0,46 0,35 0,46 1,50 1,80
Ni chung phn h c l ngun phn bn ch yu trong qu trnh gieo trng
a s lng nh cc loi phn bn ha hc c t c s dng. Tuy
nhin, hu ht cc thuc tr su, n c s d , c loi b trong qu
ngm, sn xut si a . Thuc tr su s dng trong nng nghip a c c tnh
l 0,5 kg/ a, t vi 0,25 kg ca thuc tr su trn tn sn phm.
Q tr m a v cht thi: a c ngm trong c 2 - 3 tun, qu
trnh tn ti vi sinh vt phn h a . Nc thi t qu trnh ny rt giu cht
di dng thc vt c t h c, it, p t pho, kali, st v canxi. Khi lng
ln cht thi t a c th c ti ch tr li lm phn h c.
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27
T c a l p n cn li sau khi tch si, trong khi si a c i tr
t mi ln th ph t a c coi l mt cht thi nng nghip. T l khi
lng ca g t a so vi si l 2,5:1. G t a c im khong 40% ca tng
khi l c a . c tnh mi m lng cht thi th a ca khong
4 triu tn v Bangladesh l khong 3 triu tn.
T a c a m lng cellulose, hemicellulose v lignin cao l lt l
40, 35 v 23%. V vy, n l mt ngun nguyn liu tim sn xut bt giy.
T a l mt trong nhng nguyn liu lignocellulose thay th cc nguyn liu
truyn thng trong sn xut bt giy Ba lades . c cc i cu tn dng
t a l m t a ci cho nhiu ngnh cng nghip, sn xut cc ha cht v cc
nhin liu lng. Tuy nhin, phn ln th a c s dng lm nhiu liu v lm
hng ro nng thn. Kho 80% t a c s dng lm nhin li
nu ti cc h ia nng thn, ch yu v Bangladesh. Vit Nam,
t a sa k i tc si t ng b thi b, s t c dng lm cht t, hng ro.
1.5. Tim nng s dng ph phm cy ay lm vt liu x l nhim mi
trng
Trong nh m , vic s dng vt liu l cht thi nng nghip
hoc nhng vt thc vt t c gi tr kinh t c c bit quan tm. Nhiu nghin
c c tin hnh nhm bi i cc cht thi nng nghip thnh vt liu x l
mi trng.
Si c a l si cellulose t nhin ph bin trn th gii; c bit, do tnh
cht vt l, ha hc v cu trc tt. c rt nhiu nghin cu bin tnh si c a
thnh vt liu x l c nhim mu, kim loi nng. Tuy nhin, ph ph phm
ca qu trnh tr a v sn xut si a li l mt v mi tr . c tnh,
mi m t tr a to ra 5 - 10 tn tr lng kh bao gm c si v thn cy.
Khong 1 tn cht k c tr li t dng l, khong 3 tn r v c tro t
[46]. Lng cht thi rn t qu trnh sn xut a l k, bao gm cc si a
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28
h , l v t c a . Do , p t trin mt chi lc qun l hiu qu cc cht
thi p t si l iu cn thit.
T c a l mt vt liu lignocellulose, do , c t ti ch thnh vt
liu trong x l c thi, loi b kim loi nng, mu v cc cht h c. Tuy
nhin, nghin cu v s dng cht thi t a mt cht hp ph cn hn ch,
c bit l ng d t a x l kim loi n tro c.
Kh hp ph thuc nhum ca t a c c nghin cu [46].
Than hot t c iu ch t t a c k p ph mu tt. T a
loi b c ti a 81,7% xanh methylen so vi 61% khi s dng than hot tnh
dng bt v 40% khi s dng than hot tnh dng vin. Tuy nhin, hiu qu loi b
BOD (33,3%) v COD (13,8%) l thp so vi x l bng than hot tnh dng
vin.
Bt t a c chng minh l mt vt liu c c kh x l phm
mu c v Rhodamin B tro c [21]. Qu trnh hp ph xy ra khi pH
khong 7 v nhit khng ng nhi n kh p ph. D lng
hp ph ti a ca bt t a i vi c l 35,7 m / v i vi
Rhodamine B l 87,7 mg/g. Hp ph x ra a v t trng thi cn bng ban
u trong vng 60 pht. Bt t a c c nghin c x l phenol trong
c [9]. Vi n p e ol ba u l 40 ppm trong 100 mL, pH dung dch bng
10; 3 a x l c 68% phenol.
nng cao kh p ph, bt t a c nghin cu ch to thnh
than hot tnh [37]. Ch to than hot tnh t t a bng cch s dng hai
p p p vt l v ha hc. T a c hot ha bng ZnCl2 t eo p
php ha hc v i c t eo p p p vt l loi b thuc nhum Brilliant
Gree tro c. Din tch b mt ca than hot t iu ch b p p p
ha hc l 2.304 m2/ v p p p vt l l 730 m
2/ . D lng hp ph cc
i ca than hot t iu ch b p p p a c l 480 m / v p
php vt l l 182 mg/g. Than hot tnh t t a c hot ha bng axit H3PO4
-
29
x l As (III) v As (IV) tro c [26]. Din tch b mt ca than hot tnh l
1.910 m2/ v d lng hp ph cc i l 399 mg/g.
P p p bi t ng trng hp ghp nhm amidoxime c chng
mi l p p p ph hp bin tnh vt li c m lng cellulose ln v
hiu qu x l kim loi n tro c cao. Tuy nhin, hin nay, cc cng trnh
nghin cu bi t t a b p p p ng trng hp p x l kim
loi nng cn rt t.
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30
Chng 2 - I V PH PHP HI CU
2.1. i tng nghin cu
T c a sa k i tch si c thu thp ti x Nam Thng, huyn Tin
Hi, tnh Thi Bnh. Thn cy a c ra sch vi c ct, sy kh 105C v
nghin thnh dng bt kc t c < 0,5 mm, c bo qun trong hp plastic.
Cc m c nhn to cha c lp cc ion kim loi nng (Zn2+
, Ni2+
, Cu2+
)
cc n k c a c pha long t dung dch gc chun c n 1000
mg/L.
2.2. Phng php nghin cu
2.2.1. Phng php bin tnh vt liu
2.2.1.1. X l b d dc NaOH
T a c ra ba ln vi c ct, s k n khi l k i
sau c nghin thnh dng bt kc t c < 0,5 mm. Sn phm t c
c bo qun trong hp plastic. Bt a c x l bng dung dch NaOH (5-
25%) vi t l bt a /d dch l 1/50 (g/mL), trong 60 pht 25C, lc vi tc
150 vng/pht. Sau khi x l bng dung dch NaOH, m c lc loi b
NaOH d v ra vi c ct n pH trung tnh. Phn cht r t c tip tc
c sy 60C k i l k i. N NaOH x l tt t c
i t q a m l v c s ti t ca cellulose tro bt t a
sa x l.
c i x c tr ca cellulose I l (101), (101-), (002) cc v tr
14,6 , 16,1 v 22,5 (2); xelulozo II l (101), (101-), (002) cc v tr 12 , 20 ,
22 (2) [16] (Hnh 13). V tr cc i x c t dao k i
q a i tr c 2.
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31
Hnh 13. V tr cc nh nhiu x c trng ca cellulose I (a) v cellulose II (b)
trong ph nhiu x tia X
T eo p p p Se al [45], c s ti t ( rI) c t t eo c t c
1 (vi cellulose I) v c t c 2 (khi cellulose I c sa d cellulose II).
CrI = ((I002 Iam)/I002) x 100 (1)
CrI = ((I101- - Iam)/I101-) x 100 (2)
Tro , I002 l c ti a ca ti t i x (002) i vi
cellulose I, I101- l c ti a i x (101
-) i vi cellulose II. Iam l
c t p t m ia 2 i x (002) v (101-) i vi cellulose I;
ia 2 i x (101-) v (101) i vi cellulose II. Iam l c v tr 2
= 18.0 vi cellulose I v 2 = 16.0 i vi cellulose II.
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32
2.2.1.2. tr p ghp acrylonitrile ln bt thn a
Bt t a sa k i bi t b NaOH c tr p p
acrylonitrile (AN) ln cellulose. Ly 1 g bt a x l NaOH vo bnh c
trn lp si i l . Tip t eo, 100 mL c t k i m o NaHSO3/(NH4)2S2O8
c b sung vo bnh, sc kh N2 v k tro 30 p t. P c i
c it 40 - 70C b m k t ia it. Sa t m AN, k
vi tc 300 v/p trong t i ia 120 - 210 pht. P tr p c
kt t c b cc c o k k v o b p v l m l b . Thm vo
bnh 100 mL d dc eta ol loi b AN d, t i kt ta s p m, loi
b cc m i; p c t r c lc q a i lc, sa ra li b etanol v
c ct (3 l ). S p m c s k 60C k i l k i. S
p m bao m polyme ca AN (polyacrylonitrile) v bt t a p AN.
S p m p c ra v i l vi N,N-dimetylfocmamit loi b
polyacrylonitrile. t r t c sa k i lc c l m k k i l k
i v i li k i l s p m.
Cc yu t n phn ng trng hp ghp AN ln bt a
c kho st bao gm: n cht k i m o, t l khi l AN/t a , it
v thi gian phn ng. ng ca cc iu ki c i t q a t
l ghp v hiu sut ghp, t tm ra iu kin ti c o mi yu t.
T l ghp (%G), hiu sut p (%E) c tnh theo cc cng thc 3 v 4
[15].
T l ghp (%G) = [(W1 W0)/W0] x 100% (3)
Hiu sut ghp (%E) = [(W1 W0)/W2] x 100% (4)
Tro , W0, W1 l lt l khi lng ca bt a c a p v sa k i
ghp AN. W2 l khi l AN ba u.
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33
Cc th nghim kho st cc yu t n kh p
acrylonitrile ln bt t a c ti c lp, c tnh k tha (kt qu ca
th nghim trc l iu ki thc hin th nghim sau) v th hin trong bng 5.
Bng 5. nh hng ca cc iu kin phn ng n kh nng ghp AN ln bt thn ay
TT Th nghim B tr th nghim
1
ng t l
[SB/APS]
(CM/CM)
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
2h, 60C, VAN = 5 mL (99,9%),
[SB] = 0; 0,05; 0,1; 0,15 hoc 0,2 mol/L
2
ng ca nng
h k i m o [I],
[I] = [SB] + [APS]
mbt t a = 1 g, Vt = 100 mL, 2h, 60C, VAN = 5 mL
[I] = 0,035; 0,0875; 0,175; 0,35; 0,525 hoc 0,7
mol/L
3 ng ca t l
AN/a
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
[SB] = 0,15 mol/L, 2h, 60C,
A /ay (g/g) = 1,62; 3,24; 4,05; 4,86; 6,48 hoc 8,1
4 ng ca thi
gian phn ng
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
[SB] = 0,15 mol/L, 60 , AN/a = 4,86 (t
vi 6 ml AN);
hi gian = 2; 2,5; 3 hoc 3,5 gi
5 ng ca nhit
phn ng
mbt t a = 1 g, Vt = 100 mL, [APS] = 0,2 mol/L,
[SB] = 0,15 mol/L, 2,5 i; VAN = 6 mL;
AN/a = 4,86;
T = 40, 50, 60 hoc 70C
Ch thch: SB l natri bisunphit, APS l amoni pesunphat, Vt l tng th tch
(mL), AN l acrylonitrile, VAN l th tch acrylonitrile (mL), I l h k i m o
SB/APS.
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34
2.2.1.3. Amidoxime a s p m p acr lonitrile
1 g c t r t c sau khi ghp acrylonitrile c amidoxime a b
NH2OH.HCl (2,5 - 15%) trong p dung dc met a ol : c (v : v = 1 : 1)
sao c o t t tc d dc b 50 ml. pH ca d dc c i c
k o t 9 10 b m i Na2CO3. P it 25 - 80C trong t i
gian 30 - 360 pht, k vi tc 300 v/p. Sa p , lc q a i lc loi
b p d dc v ra s p m t c 3 l vi c ct pH tr t ,
s k k i l k i.
Cc yu t n phn ng amidoxime ha sn phm ghp PAN
bao gm: n NH2OH.HCl, nhit phn ng, thi gian phn ng. Da vo
m lng t it i iu qu ca qu trnh amidoxime [11]. S bin
thin ca m lng t it biu th cho s t a i ca nhm amidoxime trong
vt liu.
nh hng ca nng NH2OH.HCl: 1 g sn phm p c phn ng
vi dung dch NH2OH.HCl cc n khc nhau (2,5; 5; 7,5; 10; 12,5 hoc 15
%) 25C trong 120 pht. Sa p , li tm tc p c t r , ra li b
c ct pH tr t , s k k i l k i v xc m
l ito.
nh hng ca nhit phn ng: 1 s p m p c p vi
d dc NH2OH.HCl n ti xc nh th nghim trc, trong khong
thi gian 120 pht. Nhit phn t a i 25, 30, 40, 50, 60, 70 hoc 80C.
nh hng ca thi gian phn ng: 1 s p m p c tip xc vi
d dc NH2OH.HCl n ti v nhit ti hai th nghim trc.
Thi gian phn t a i t 30, 60, 120, 180, 240, 300 hoc 360 pht.
2.2.2. Xc nh c tnh c bn ca vt liu
Vt liu hp ph c xc c im vt l v ha hc c bn, chi tit
cc p p p c trnh by trong bng 6.
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35
Bng 6. Phng php xc nh mt s tnh cht vt l, ha hc ca vt liu
Tnh cht Phng php phn tch Thit b phn tch
c im hnh thi Knh hi vi in t qut JSM 5410LV, hng Joel
c im cu trc Nhiu x tia X Bruker-AXS D5005,
Sieme s, c
in tch b mt P tc in di Mtek PCD 05, hng
BTG, c
c im lin kt,
nhm chc
Quang ph hp th hng
ngoi (FTIR)
Nicolet iS5 FTIR
Spectrometer, hng
Thermo Scientific, M
- Phng php nh lng cellulose [1]
P p p lng cellulose da trn tnh cht bn ca cellulose i
vi tc dng ca axit mnh v kim mnh, khng b phn h di tc dng ca
axit yu. Cc cht khc c trong vt liu ligniocellulose hemicellulose, lignin,
tinh bt, amin, cc axit bo,... t bn trong dung dch axit v kim nn b oxi ha v
phn gii, sa ta v o d dch sau khi x l nguyn liu.
P p p lng cellulose c ti sa : c xc 1-
2 am t a k c o v o b tam ic 500 mL, b sung vo bnh 200 mL dung
dch NaOH 0,5%. Lp si o l tro 30 p t k t lc si. Lc
cht rn qua giy lc hoc ly tm. Ra cht r t c vi dung dch NaOH 0,5%
nng. Tip tc cho cn tc dng vi 10 mL H l 10%. T m v o 10 mL d
dch natri hypoclorit tng git mt, va cho va khu . yn trong 5 pht ri
lc qua giy lc thu cht rn. Cho cht rn tip tc tc dng vi NaOH 0,5%
nhit 40o . yn vi pht v lc cht rn. Lm lp li 2 ln na t c
cellulose trng. Sau cng, ra sch cellulose t c b c si. Sy kh v
cn tr lng cellulose.
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36
H m lng cellulose trong t a c tnh theo cng thc:
X (%) = (a.100)/m (5)
Tro : a l tr lng cellulose (g)
m l tr lng m t a ( )
2.2.3. Kho st kh nng hp ph ion kim loi nng ca vt liu bin tnh
- nh hng ca pH: xc thng qua bi i m i b mt ca vt
li sa k i bi t ti cc i tr pH k c a . Gi tr pH t c p p i t p
i tr pH kt ta cc cc io kim loi v t im axit t si tro
c sa k i x l.
- Xc nh cc h s hp ph ca vt liu bin tnh vi cc ion KLN
Ti t im p p cc io kim loi Cu2+
, Zn2+
hoc Ni2+
b 100 m vt li bi t trong 100 mL dun dc c a cc io kim loi vi
ba l 0, 20, 40, 60, 80 oc 100 m /L. T im c ti
25C, pH d dc b 6 (pH k o st c tro t im trc), lc vi tc
100 v /p t tro v 1 i v m 24 i. c lc xc
io kim loi c li tro d dc sa c b p p b m q ang
p p t t AAS (S imadz , N t B ).
- Xc nh thi gian lu ti u cho qu trnh x l ion KLN (Zn2+, Ni2+,
Cu2+
) vi vt liu bin tnh
Cn 250 mg vt liu vo 250 mL dung dch cha Zn2+
, Ni2+
hoc Cu2+
c
n (Qimax x 250mg) / 250mL = Q
imax (mg/L) vi Q
imax (m / ) l d lng
hp ph cc i ca vt liu vi Zn2+
, Ni2+
hoc Cu2+
. M c lc tc 100
v/p theo thi gian. Sau mi khong thi gian cch nhau 1 gi, dung dch cha vt
li c lc u v ly ra 25 mL sao cho mt vt liu tromg dung dch cn li
v ly ra l bng nhau. Dung dch l ra c lc v phn tch KLN bng my
quang ph hp th nguyn t AAS (S imadz , N t B ).
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37
Chng 3 - K QU HI CU V HO LU
3.1. c tnh c bn ca bt thn ay
Bt t a l vt liu lignocellulose, cha mt m lng cellulose
k. Cellulose trong bt t a l c i polyme chnh, nhm (-OH) trn phn t
cellulose vai tr q a trng trong lin kt vi nhm nitrile ca monome
acrylonitrile ln bt t a . Do , cc c t c bn ca t a bao m c
im hnh thi b mt, cu trc cellulose, cc nhm chc b mt trn bt t a
c c kho st trc khi tin hnh bin tnh ha hc.
3.1.1. c im hnh thi b mt ca bt thn ay
Bt t a c d v kc t c k ng nht. Kt qu phn tch
trn knh hi vi in t qut (SEM) cho thy dy cc mnh bt t a khong
5 m. B mt ca bt t a ba u c cc mng bm nh dng vy (Hnh 14).
i t t khi quan st thy trong bt g ca cc sinh khi khc [32].
(a) nh chp p i 1000 ln (b) nh chp p i 2500 ln
Hnh 14. nh SEM b mt bt thn ay
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38
3.1.2. c im cu trc ca bt thn ay
Thnh phn ca bt t a bao m c vng v nh hnh v vng tinh
th. Tro lignin, hemicellulose, pectin l nhng hp cht v nh hnh ch yu;
tro k i cellulose ng thi tn ti c hai d v nh hnh v tinh th. Dng
v nh hnh trong cellulose khi dng sinh khi ba u l dng tinh th cellulose
I [48, 50]. Kt qu nhiu x tia X (Hnh 15) cho thy kt qu t ng vi cc
nghin cu v cc sinh khi thc vt khc. c nh nhiu x c tr ca dng
cellulose I xut hin v tr c 2 l 22,52o
(002); 16,01 (101-) v 15,11 (101). Ch
s tinh th ca cellulose trong bt t a c i tr l 55,76 %. N v , mt
na lng cellulose tro t a tn ti dng tinh th. Tro k i , p
php bin tnh ha hc c hiu qu i vi v v nh hnh v d tip c
so vi vng tinh th. Do , bt t a cn phi x l ph v cu trc tinh th,
t t l v v nh hnh.
Hnh 15. Ph nhiu x tia X ca bt thn ay
-
39
3.1.3. c im lin kt, nhm chc
Kt qu phn tch ph hp th hng ngoi i vi bt t a cho thy, b
mt ca bt t a cho thy bao gm cc nhm v lin kt ch yu l (OH),
C=O, C=C, CC, CH. Cc nh hp th s sng 3.350 cm-1
biu th dao ng
ca nhm (OH). Nhm ny c th tn ti trong lin kt (OH) lin phn t, ni
phn t ca cellulose, hemicellulose, lignin; lin kt hydro trong nhm cacboxyl.
Tro k i , nh hp th s sng 1.739 cm-1
th hin s tn ti ca lin kt C=O
trong nhm cacboxyl. Lin kt CO ti v tr v t m ca lignin xut hin s
sng 1.250 cm-1
. Vch ph s sng xut hin s sng 1.598 cm-1
th hin dao
ng dn ca lin kt C=C trong cc axit bo.
Hnh 16. Ph hp th hng ngoi ca bt thn ay
Nhn chung, qua ph hp th hng ngoi c th thy, b mt ca bt t a
cha cc nhm chc in hnh l nhm hydroxyl, nhm cacboxyl. Cc nhm chc
ny c vai tr quan tr tro p p p bi t ng trng hp ghp, trong
c bit quan trng l nhm hydroxyl trong polyme cellulose.
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40
3.2. Quy trnh bin tnh to vt liu amidoxime ha t bt thn ay
3.2.1. X l bng dung dch NaOH
3.2.1.1. Lm giu cellulose trong bt t a
X l bt t ay bng dung dch NaOH nhm loi b cc cht h c d b
thy phn, c th to thnh cc cht h c tro c l lignin, hemicellulose,
amin, axit h c. Bt t a sa x l c m lng cellulose-polyme mch
chnh t , ip c o phn ng trng hp ghp vi AN c thun li.
ng ca n dung dch NaOH x l n khi lng bt t a
a c li v s bi i m lng cellulose trong bt t a c th hin trn
hnh 17.
Hnh 17. nh hng ca nng NaOH n khi lng cn li v hm lng
cellulose trong bt thn ay
K i t NaOH, qu trnh thy phn cc cht lignin, hemicellulose,
axit bo,... din ra cng mnh nn khi l a c li gim. iu ny d n
m lng cellulose trong bt t a c t k i t NaOH. Khi
lng bt t a c li gim nhanh khi n NaOH t n 5 v 10% so vi
bt t a ba u do qu trnh ha tan ph v nh hnh din ra mnh. Tuy
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41
nhin, khi tip tc t NaOH th khi lng bt t a im khng
nhiu v g do m lng ph v nh hnh trong bt t a l
gii hn.
Qu trnh x l bng NaOH thc cht l qu trnh lm giu cellulose lm
nguyn liu cho cc bc nghin cu bin tnh tip theo. khong n NaOH
t 10% tr ln, m lng cellulose t mc cao v g nh.
3.2.1.2. Xc nh ch s tinh th ca cellulose trong bt t a bng ph nhiu x
tia X
Qu trnh x l b NaOH ng thi l m t a i cu trc ca cellulose
trong bt th a . P nhiu x tia X ca bt t a t v bt t a x l
bng dung dch NaOH cc n k c a c th hin trn hnh 18.
Hnh 18. Ph nhiu x tia X ca bt thn ay ban u v x l cc nng dung
dch NaOH khc nhau
C th thy rng, bt t a ba u C0 v bt t a c x l vi
dung dch NaOH cc n 5% v 10% l C5 v C10 dng cellulose I vi cc
nh nhiu x v tr c 2 l kho 22,5 n 22,7 v cc nh nhiu x v tr
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42
14 n 16. Khi n NaOH t n 15%, xut hi ai nh nh nhiu x
v tr c 2 l 20,1 v 12,2. l cc nh nh nhiu x c tr ca cellulose
II. iu ny chng t rng qu trnh x l bng dung dch NaOH lm chuyn dang
cu trc ca cellulose I sang cellulose II. Cc nh nhiu x c tr ca cellulose
II c x t hin cc m a x l vi dung dch NaOH 20 v 25% (C20 v
C25).
Ch s tinh th c tnh ton theo cng thc v 1 v 2 (mc 2.2.1.1), s ph
thuc ca ch s tinh th vo n NaOH c th hin trn hnh 19.
Hnh 19. S bin i ch s tinh th ca cellulose trong bt thn ay khi x l vi
dung dch NaOH cc nng khc nhau
Ch s tinh th ca bt t a t l 16,72% so vi th a ba u sau
khi x l vi NaOH 5%. Tuy nhin, khi n NaOH t l t c s tinh th
li gim d v t gi tr ti thiu 45,45% ti n NaOH l 15%. Sa , c
s tinh th t khi n NaOH t l 20% v t gi tr nh. iu
ny c th gii thch do ba qu trnh xy ra khi x l bng kim: bt t a tr
n, ph v vng tinh th v hnh thnh mng tinh th mi. n NaOH thp,
lng NaOH v mt NaOH nh, k ph v mng tinh th cellulose vi
cu trc c bao bc bi hemicellulose v lignin. Ch c v v nh hnh v
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43
vng tinh th b mt trong cu trc cellulose c th phn ng vi kim. N vy,
vng khng gian gia cc mch polyme cellulose khng ln nn cc si c kh
sp xp li cu trc [48]. Do , c s tinh th ca t a t k i
NaOH nh. K i t NaOH ln 15%, cu trc cellulose t trng thi
tr nhiu nht, iu ny lm cho NaOH d dng tip xc vi cc vng tinh
th ca cellulose v ph v cu trc tinh th d n CrI gim k. Tuy nhin,
kh tip xc vi cellulose ca NaOH gim do t nht ca dung dch
NaOH n cao [48], do , c s tinh th vn ln.
T cc kt qu thc nghim nu trn, c th thy rng n NaOH 15% l
n thch hp nht lm gim cc vng kt tinh trn cellulose c l m
t m lng cellulose trong bt t a .
3.2.1.3. c im lin kt v nhm chc b mt
Ph hp th hng ngoi ca bt t a t v sa k i x l bng NaOH
cc n khc a c th hin trn hnh 20.
Hnh 20. Ph hp th hng ngoi ca bt thn ay ban u v x l cc nng
NaOH khc nhau
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44
Kt qu cho thy, lin kt hydro trong nhm hydroxyl (OH) dao ng xut
hin di ph t 3.000 - 3.600 cm-1. nh hp th ca nhm (OH) gim dn khi
n NaOH t l do m OH p n ng vi Na+. S suy gim nhm (OH)
c th do qu trnh thy phn cc cht km b axit bo, emicell lose, li i
trn b mt bt t a . c li kt hydro ni phn t O2-H---O6, O3-H---O5 v
lin kt hydro lin phn t O6-H---O3 tro cell lose I t ng xut hin di ph
t ng l 3.455 - 3.410, 3.375 - 3.340 v 3.310 - 3.230 cm-1
. Ph hp th hng
ngoi ca bt t a ba u v x l cc n dung dch NaOH thp (5, 10
%), nhm (OH) xut hin s sng 3.350 cm-1
; tuy nhin, khi x l cc n
NaOH cao (15, 20, 25%), nhm OH xut hin s sng 3.447 cm-1 c tr c o
lin kt O2-H---O6 tro cell lose II. iu ny chng t rng, cu trc tinh th ca
cell lose I c n sang dng cellulose II sau khi x l bng NaOH.
nh hp th s sng 1.739 cm-1
quan st thy trong bt t a ba u
v mt i sa k i x l bng kim tt c cc n NaOH trong nghin cu.
iu ny l do nhm cacboxyl b thy phn sau khi x l bng kim, qu trnh ny
c gi l este ha [32]. S suy gim c ca nhm C=O s sng 1.655
cm-1
khi x l bng kim ch ra rng hemicellulose b loi b sau khi x l kim.
nh hp th v tr s sng 1.250 cm-1
hin th cho lin kt C-O ti v tr
v t m ca lignin trong bt t a c im i k sau khi x l bng
kim. nh hp th v tr 897 cm-1
chuyn sang v tr 894 cm-1
. S sng 897 cm-1
trong lin kt -glucozit trong cu trc cellulose I v s sng 894 cm-1
trong cu
trc cellulose II [50]. S t a i ny l do glucose quay quanh lin kt glucosidic
lm cho cu trc cellulose I chuyn sang dng II.
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45
3.2.2. ng trng hp ghp acrylonitrile ln bt thn ay bng h khi mo natri
bisunphit/amoni pesunphat (SB/APS)
3.2.2.1. c ca p tr p p acr lonitrile b k i m o
natri bisunphit/amoni pesunphat
Phn ng trng hp ghp AN bng h k i m o oxi a k SB/APS
da tr c c gc t do. Gc t do c to thnh t phn ng ca h k i m o,
sa cc gc ny tip tc phn ng vi nhm OH trn mch cellulose hnh
thnh cc gc cao phn t. Cc gc cao phn t ny tip tc khi xng phn ng
ng trng hp ghp AN ln mch cellulose. Phn ng trng hp polyacrylonitrile
(PAN) c di ra ng thi vi phn ng trng hp ghp.
Gc t do SO4-*
c to ra t phn ng gia natri bisunphat v amoni
pesunphat t eo p tr 7 [43].
H2O + HSO3- + 2S2O8
2- 3HSO4
- + 2SO4
-* (7)
SO4-*
+ H2O HSO4- + HO
* (8)
Gc SO4-*
s tip tc phn ng vi cc nhm hydroxyl trn mch cellulose
[40] hnh thnh cc gc cao phn t trn cellulose (Cell OH) (p tr 9)
v gc t do M* (p tr 10).
SO4-*
+ Cell OH HSO4- + Cell O
* (9)
M + SO4-*
M* + SO4
2- (10)
Cc gc cao phn t ny tip tc khi xng phn ng ng trng hp ghp
monome ln mch cellulose v phn t PAN t eo c c sau:
Cell O* + M Cell OM
* (11)
Cell OM* + M Cell OMM
* (12)
Cell OM*n-1 + M Cell OMn
* (13)
Cell OM*n + Cell OM
*n sn phm ghp (14)
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46
Phn ng trng hp PAN din ra song song vi phn ng trng hp
p, c c phn ng trng hp AN sa :
M* + M MM
* (15)
Mn-1* + M Mn
* (16)
Mn* + Cell-OH Cell-O
* + MnH (17)
Mn* + Mm
* Mn+m (18)
P p p ng trng hp ghp c k i m o bng h oxi ha kh, cc
gc t do phn c to ra t phn ng ha hc. Do , cc u t n
cht k i m o, monome, thi gian, nhit l nhng yu t ng
trc tip n hiu sut qu trnh ghp.
3.2.2.2. ng ca t l cc cht k i m o
Hnh 21 th hin ng ca t l cc cht k i m o SB/APS (CM/CM)
n t l ghp v hiu sut ghp. N SB t a i t 0 n 0,2 mol/L, n
APS c nh n 0,2 mol/L. Kt qu cho thy, t l ghp (G%) t cao nht l
13,13% v hiu sut p t 3,24% khi t l SB/APS l 0,75.
Hnh 21. nh hng ca t l SB/APS n kh nng ghp AN ln bt thn ay
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47
t l thp , SB k phn ng vi APS to thnh gc
t do d n t l ghp v hiu sut ghp thp. T l ghp t l k iu
k i t SB. T l ghp t 2,51% khi h k i m o ch c APS v t l
t 2,55% khi t l SB/APS l 0,25. iu ny chng t rng; khi n SB thp,
phn k i m o c y do APS vai tr c . K i c cung cp nhit
, ion pesunphat trong APS c th to thnh gc t do t eo p tr sa :
S2O82-
2SO4-*
(19)
SO4-*
+ H2O HSO4- + HO
* (20)
Khi t l SB/APS t l 0,5 p n k i m o to thnh nhiu gc t do
d n t l ghp t l 3,83% v t gi tr cao nht l 13,13% khi t l ny
l 0,75. T eo p tr 7, t l cn bng ha hc ca phn ng to gc t do
gia SB v APS l 0,5.
T l SB/APS tip tc t l 1 t G (%) v E (%) im do cc gc t do
to thnh t phn ng k i m o to ra ln d n phn ng trng hp PAN cnh
tranh vi phn ng trng hp ghp, cc gc t do M* ca AN phn ng vi
nhau lm gim hiu qu phn ng ghp. Trong phn ng ghp nhm vinyl ln
g/cellulose, HO* c kh p n i SO4
-*. Tuy nhin, khi t l SB/APS
cao, gc t do b trit ti t eo cc p tr (21) (23) [43].
SO4-*
+ H2O HSO4- + HO
* (21)
2SO4-*
+ HSO3- 2HSO4
- + SO4
2- + H
+ (22)
2HO* + HSO3
- SO4
2- + H2O + H
+ (23)
3.2.2.3. ca k i m o SB/APS
T l SB/APS = 0,75 c la ch nghin cu ng ca tng nng
h k i m o n kh p. Tng n h k i m o [I] = [SB] + [APS].
Hnh 22 th hin s ph thuc ca t l ghp v hiu sut ghp vo n h k i
mo I. iu ny ph hp vi l thuyt Smith-Ewart d o rng tc ca phn
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48
ng trng hp ph thuc vo hai bin, n k i m o v cht c hot
b mt.
Hnh 22. nh hng ca tng nng h khi mo n kh nng ghp ca AN ln
bt thn ay
Ba , k i t h k i m o, t l ghp v hiu sut p t ,
sa im dn. Kh p tt nht t c khi tng n k i m o l
0,35 mol/L vi t l ghp l 13,13% v hiu sut ghp l 3,24%. S ia t ca t
l ghp v hiu sut ghp l cc gc t do c to t t k i h k i
m o t v cc c ny c s phn ng vi mch cellulose. Khi n h
k i m o t 0,35 mol/L, cc gc t do pesunphat t l ; do ,
khi xng phn ng trng hp AN, phn ng ny cnh tranh vi phn ng
trng hp ghp do cng tiu th AN v gc pesunphat.
3.2.2.4. ca t l acrylonitrile/a
T l khi l AN/a l yu t quan trng quyt nh hiu qu qu trnh
ghp. ng ca t l AN/a c th hin trn hnh 23.
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49
Hnh 23. nh hng ca t l khi lng AN/ay n kh nng ghp AN ln bt
thn ay
K i t t l khi lng AN/a t 1,62 (t ng vi 2 mL c) ln 4,05
(t ng vi 5 mL AN c) th t l ghp t t 3,59 n 13,13%. Hiu sut
ghp c s t a i k k. Khi t l AN/a t l n 4,86 (t ng
vi 6 mL AN c) th kh p t l rt nhanh, t l ghp t cao nht l
88,63% v hiu sut ghp l 18,24%. iu ny l do lng AN t l m t kh
tip xc ca AN vo mch cellulose tr t a , d t k p
AN vo cc gc t do trn mch cellulose. H a, n AN cao cn lm cho
bt t a tr , to iu kin cho s khuc t cc mo ome AN do l m
t iu qu ghp [17]. Tuy nhin, t l ghp v hiu sut ghp li c x ng
gim nhanh khi tip tc t t l AN/a q 4,86. i c gii thch l do
s cnh tranh gia phn ng trng hp AN v phn ng trng hp ghp. Khi
n AN trong dung dch phn ng cao th phn ng trng hp AN chim t
[30].
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50
3.2.2.5. ca t i ia p
Kt qu ng ca thi ia n kh p c th hin trn hnh
24. C th thy, kh p t a k i t i gian phn t t 2 n
2,5h; t gi tr t l ghp v hiu sut ghp ti a l lt l 131,36% v 27,03%
2,5h. Tuy nhin, sau 2,5h th kh p c x im c th l do s ha
tan mt phn sn phm ghp khi tip xc trong thi gian di nhit cao 60C [17].
Do , t i gian phn hiu qu ghp ti l 2,5 .
Hnh 24. nh hng ca thi gian phn ng n kh nng ghp AN ln bt thn ay
3.2.2.6. ca it p
Nhit l mt trong nhng thng s quan trng quyt ng hc ca
qu trnh ghp. Kt qu cho thy, t l ghp v hiu sut p t k i t it
t 40 60 , sa im dn khi nhit t l n 70C. T l ghp v hiu
sut ghp cao nht t c khi nhit phn ng 60C l lt bng 131,36% v
27,03%. N vy, nhit ti c o p n p AN l t a l 60 .
Nhit cao l m t k va c m ca cc phn t v cellulose d n s
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51
gia t cc c t do tr cell lose v do t cng kh p AN l
cellulose. Mt khc, hiu sut ca phn k i m o t l k i t it .
Hnh 25. nh hng ca nhit n kh nng ghp AN ln bt thn ay
Tuy nhin, t l ghp v hiu sut ghp li gim nu tip tc t it
ln 70C c th do phn k i m o si ra mt lng ln cc gc t do trong
mt v thi gian. Kt qu l, cc gc t do trn b mt cellulose d tip xc vi
nhau lm mt cc gc t do theo cc phn ng ngt mch. Mt khc, khi nhit
t , li ng ca cc gc t do s t v d dng tip xc vi nhau [40]. Xu
c c quan st thy trong cc nghin c t t [17,29]. Mt
nghin cu c cng b [43] tin hnh kho st ng thi t l ghp v hiu
sut hnh thnh PAN, kt qu ch ra rng, nhit 40-60C, phn ng trng
hp ghp chim t . Tuy nhin, nhit cao (70 ) t p n ng trng
hp AN li chim t . Do , it ti ca phn ng trng hp ghp
AN ln bt t a l 60 .
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52
N vy, hiu qu ca phn ng trng hp p AN l t a cao
nht khi: n natri bisunphit, 0,15 mol/L; n amoni pesunphat, 0,2 mol/L;
t l khi lng AN/bt t a , 4,86:1 g/g; thi gian, 2,5h; nhit , 60C.
3.2.3. Phn ng amidoxime ho
3.2.3.1. ca NH2OH.HCl
Sau phn ng trng hp ghp AN ln bt t a , m l it (%)
t t 0,18% trong bt t a c a bi t l n 3,18%. Sn phm ng
trng hp p c tip tc phn ng amidoxime vi hydroxylamin
hydroclorid cc n khc nhau. Khi n NH2OH.H l t trong khong
t 2,5 n 10%, m l it tro vt li t l k chng t m lng
nhm amidoxime trong vt li t l . iu ny l do cc nhm nitrile (CN)
trn b mt vt liu c s phn ng vi NH2OH tro mi trng kim to
thnh nhm amidoxime (C(NH2)=NOH).
Hnh 26. nh hng ca nng NH2OH.HCl
K i t n NH2OH.H l t l t 10 15% t m l it
t k k; t 8,35% 10%, 8,43% 12,5% v 8,54% 15%. N vy,
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53
n NH2OH.HCl 10% l n m phn ng to thnh nhm amidoxime t
trng thi . Do , c chn thc hin cc th nghim tip
theo.
3.2.3.2. ca it p
Hnh 27. nh hng ca nhit phn ng
ng ca nhit n kh amidoxime a c th hin trn
hnh 27. Kt qu cho th , m lng nit t a k i it phn t
trong khong t 25 l 60 v t ti a l 10,47% 60C, chng t m lng
nhm amidoxime trong vt li t a k i it t . T i , k i
nhit l cao l 60 t m l it li gim. iu ny c th do nhit
cao lm phn ly cc nhm nitrile trn b mt bt t a , d n lm gim v
tr hot ng ca phn ng chuy i. X t t c c quan st thy
trong nghin cu ca c cng b [20].
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54
3.2.3.3. ca t i ia p
Thi gian phn ng amidoxime c t a i t 30 n 360 pht v gi cc
thng s nhit c nh 60C v n NH2OH.HCl l 10% i nh
ng ca thi ia n phn ng chuyn ha nhm nitrile thnh nhm amidoxime.
Hnh 28. nh hng ca thi gian phn ng
Kt qu nghin cu cho th , m l it c m lng nhm
amidoxime trong vt li t a k i t i gian phn t n 120 pht. Khi
tip tc t t i gian ln 180 v 240 pht t m l it t c m v t n
nh khi thi gian phn l 240 p t. Lng amidoxime c to thnh ln
tro iai o u ca phn ng l do s lng nhm nitrile c sn trn b mt
t a c o c chuyn ha thnh amidoxime. N k i t g thi gian phn
ng, s lng cc nhm nitrile im rt nhiu d n hiu sut phn ng thay
i khng nhi . N vy, thi gian bo ha ca phn ng amidoxime l 240 pht.
T cc kt qu ti a cc bc tro p p p bin tnh to vt liu
amidoxime ha t bt t a , s quy trnh bin tnh vt li c th hin trn
hnh 29.
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55
R/L = 1: 50 (g/mL)
- R/L = 1:50 (g/mL)
- pH = 9 10
T l AN/a = 4,86
(g/g)
R/L = 1: 100
(g/mL)
Bt t a
NaOH 15% - Thi gian: 1 gi
- Tc lc: 150 v/p
- Lc, ra sc n pH = 7
Bt t a x l NaOH Hn hp
NaHSO3/(NH4)2S2O8
[NaHSO3] = 0,15 mol/L
[(NH4)2S2O8] = 0,2 mol/L
- Sc kh N2
- Nhit 60C
- Thi gian: 30 pht
- Gdyhuieg dsuds
ncmcssd
-
Hn hp 1
- Sc kh N2
- Nhit : 60C
- Thi gian: 2,5 gi
- Vn tc khuy: 300 v/p
Hn hp 2
Etanol,
N,N -dimethylfocmamit - Ra, lc
- Sy kh 60C
Sn phm ghp
Vt li bin tnh
NH2OH.HCl 10% - Nhit : 60C
- Thi gian: 240 pht
- Vn tc khuy: 300 v/p
- Lc v sy kh 60C
Acrylonitrile 99,9%
Hnh 29. Quy trnh bin tnh to vt liu amidoxime ha t bt thn ay
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56
3.3. c tnh ca vt liu bin tnh
a. b.
c. d.
Hnh 30. c im hnh thi b mt ca bt thn ay ban u (a), ay x l bng
NaOH 15% (b), ay ghp AN (c) v vt liu bin tnh (d)
c im hnh thi b mt ca bt t a ba u, sau khi x l vi NaOH
15%, ghp AN v vt li bin tnh c th hin trn hnh 30.
M a sa x l b NaOH c c loi b cc cht h c l m c o
b mt tr nn nh v c cc r . Sa k i amoxime ha, b mt bt t a tr
nn dy v xp so vi bt thn a ba u v x l bng dung dch NaOH.
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57
Ph FTIR ca t a ba u, sau khi x l bng dung dch NaOH 15%,
ghp AN v vt liu bin tnh c th hin trn hnh 31, 32.
Hnh 31. Ph hp th hng ngoi ca bt thn ay ban u (a), sau x l NaOH
15% (b) v ghp AN (c)
Cc lin kt v nhm chc trong bt t a ba u, x l bng dung dch
NaOH, ng trng hp ghp AN v vt li bin tnh c xc nh bng ph
hp th hng ngoi. So snh ph bt t a sa k i x l NaOH (Hnh 31b), ph
bt t a sa k i p AN x t hi nh hp th v tr 2.260 cm-1
, biu th
cho s ko c ca lin kt N. Sa k i amidoxime a, ba nh hp th xut
hin v tr 2.260, 1.660 v 910 cm-1
t ng vi cc lin kt N, =N v N
OH do phn ng ca hydroxylamin vi nhm nitrile c th hi di p
trnh sau [38]:
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58
(24)
ng thi, s suy gim c hp th ti v tr s sng 2.260 cm-1
trong
ph ca vt liu (Hnh 32) so vi ph bt t a sa k i p AN (H 31c)
chng t mt phn nhm nitrile t am ia v o p n ng amidoxime ha. Ph
hng ngoi ca vt liu xut hi nh hp th khong s sng 3.423 cm-1
v c
c ln th hin lin kt hydro trong nhm hydroxyl (OH) hoc lin kt NH
trong nhm (NH2).
Hnh 32. Ph hp th hng ngoi ca vt liu
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59
c im in tch b mt ca bt t a ba u, sau khi x l bng
dung dch NaOH 15% v vt li c th hin trn hnh 33 v hnh 34. Kt qu
cho thy, qu trnh x l bng kim lm cho b mt t a m i so vi
t a ba . iu ny l cn thit nng cao hiu qu phn ng trng
hp ghp AN [44]. S lng nhm (OH) c kh tip c t l sa p n
ng v lm cho b mt m i . K i pH c t t m (OH) trn b mt
vt liu gii phng ra ion H+ trung ha kim, d n b mt vt li m in
k i pH t l [41].
Hnh 33. Th zeta ca bt thn ay ban u, sau x l NaOH 15% v vt liu
Vt li bin tnh c b mt m i so vi bt thn a x l NaOH
v bt thn a ba u. Chng t rng, vt li bin tnh c ghp vo cc
nhm (OH) l m t m in. Th zeta ca vt liu gim a k i pH t a i
t 2 n 6; khi pH > 6, th zeta gim chm v g k im k i t pH t
10 11. T t t zeta, s l in tch m b mt (cmole(-)
/kg) cng
ln khi gi tr pH cng cao (Hnh 34).
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60
Hnh 34. in tch m b mt ca vt liu bin tnh cc pH khc nhau
3.4. Kh nng x l kim loi nng (Cu2+
, Zn2+
, Ni2+) ca vt liu bin tnh
3.4.1. Xc nh gi tr pH x l
N trnh by ph c tnh ca vt li bin tnh, vt liu c b mt
m in, gi tr pH c cao t pH c m in. Ti pH 6, m in ca b
mt kh l v k i t pH t m in b mt gim khng nhi . T i ,
loi b ng ca qu trnh kt ta cc ion kim loi, pH 6 l gi tr pH ph hp
i k p ph KLN ca vt liu. Do , i tr pH 6 c ch
thc hin cc th nghim i k x l ion kim loi