PHAN III KET QUA VA THAO LUAN
4.1. Khiio sat ciic yeu td anh hudng den kha nang hap phu cae ion kim loai nilng trong moi trudng nudc ciia bentonite
Chiing loi da sir dung bentonite Iii loiii khoiing bentonile Dilinh Lam Ddng da dugc chfit hoii nhu sau: bentonite sau khi dugc liim giau bang thiet bi xyclon, dugc hoiit hoa bang H2SO4 15% (d nong do nay benlonite dugc hoiit hoa tdt nhfii, cho dung lugng hfip phu tdt nhii't) vdi thdi gian hoiit hoii lii 2h, ty lc R/L = 1 :3, nhiet do hoat hoii la 85-95*^0.
Hiim lugng montmorillonite trong khoang bentonite niiy Iii > 70%.
Dc khao sat khii nang hfip phu, chiing toi sir dung hai ion kim lo.ai nilng lii Mn~" va 4.1 .F Anh hudng cua pH dung dich den khd ndng hdp phu Fe~^ vd Mn~^ tren bentonite.
Pha Ciic dung dich Mir" va Fe"" nong do Iii 3g/l vii 0,9 g/1 co cac gia tri pH xac dinh la 2,0; 2,5; 3,0; 3,5; 4,0; 4,5 va 5. Lfiy biiy binh non dung tfch 250inl, theo viio mdi binh 2g bentonite, 50 ml ciia mot trong ciic dung dich co pH khiic nhau tren. Day kfn mieng binh va lien hanh hic vdi tdc do 140 vong/phiit, ddieu kien nhiet do phdng, trong thdi gian 3 h. Sau khi hlc, Igc dung dich bang gifiy Igc bang xanh va tien hanh xac dinh n6ng do ciui ciic ion Mir" vii Fe'" trong dich lgc, hiip dung eiia bentonite dugc xac dinh theo cong thirc: a = ( CQ - C).V/m. Ket quil thuc nghien dugc dua ra nen bang 1.
Bdng /• Sir phu thugc hdp dung bentonite ddi vdi Fc^ vd Mn~^ vdo pH cua dung dich.
pH 2,0 2,5 3,0 3,5 4,0 4,5 5,0 Hfipdung ddi vdi 8,7 10.5 12,6 13,8 14,3 14,2 13,7
Fe'^ mg/g
Hfipdung ddi vdi 10.2 15,4 19,7 23,5 26,7 23,1 19,4 Mir"*", nm/ii
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TiJ* ke't quii da trinh bay tren bang 1 co the thfiy rang, khi pH dung dich thay d6i tir 2,0 den 5,0 hap dung ciia bentinit ddi vdi Fe"^ va Mn"" deu cd dang bien ddi nhu nhau.
Hap dung ciia bentinit ddi vdi Fe^"^ va Mn^"^ tang len khi pH tang tir 2,0 den 4,0, diit cue dai tai pH nay, sau dd giam xudng khi tang pH tiep. Ket qua niiy cung phii hgp vdi ke't qua cira cac tac gia cong trinh [6]. Nhu vay pH tdi uu cho qua trinh hfip phu hai ion Fe"^"
va Mn^''"tren bentonite tir moi tnrdng nudc lii 4,0.
4.7.2. Anh hudng cua thdi gian khuay tdi sir hdp phu Mtr^vd Fc'^ tren bentonite Tien hanh thf nghiem nhu sau: pha ndng do ciia Mir" va Fe'^" vdi nong do la 3g/l va 0,9 g/1, tien hanh thf nghiem: ddi vdi mdi thf nghiem lay 9 binh non, can vao m6i binh 2g bentonite da hoiU hoii, dd viio mdi binh 50ml dung dich Mn'" hoac Fe'" vdi n6ng do nen, chinh ve pH = 4, day kfn cho vao nuiy Ific vdi tdc do 140 vdng/ phiit trong thdi gian khuay khac nhau: 0,5 ; 1 ; 1,5; 2; 2,5; 3; 3,5; 4 h sau nhQ-ng khoimg thdi gian iren, lay dung dich ra lgc vdi gifiy lgc bang xanh va lien hanh Xiic dinh nong do ciui dich lgc, hfip dung ciia bentonite dirge xiic dinh theo cong thiic: a = (CQ - C).V/m
Trong dd, a la hfip dung (mg/g); CQ - nong do ciia dung dich ban dfiu trirdc khi lac;
C - ndng do ciui dung dich sau khi lac; in- khdi lugng ciia bentonite. Ket quii khiio siit sir phu thugc giua hfip dung ciui Mn'^ vii Fe"" vdi thdi gian Lie khiic nhau dugc dua ra trong bang 2 va ciic hinh 4 va 5.
Bdng 2: Sd lieu hdp dung cua Mn''' vd Fe''' vdi thdi gian lac khdc nhcui
Tlidi gi Mn-^
1 1 1
Fe^^
1
an khiiay(h) nong do can bring (g/1) hap dung (mg/g)
nong do can bring (g/1) hap dung (mg/g)
0,5 2.53
15.98 0.696 5.1
1 2,31
18.53 0.58 7.99
1.5 2.1395 21.5 0.492
10,2
2 2.046 23.85 0.417 12.07
2,5 1.98 25.85 0.3628
13.43 3
1.925 26.87 0.324 14.4
3,5 1.914 26.9 0.3244
14,39 4
1.92 26.91 0.324 14.4
20
"5.
E 22 -J
• lico [(t:i(J7~l
0 0 0 5 1 0 1 5 2 0 2 5 3 0 3 5 ' : 0 4 5 T h o i j ; i . i n h
Hinh 4: Dd thi hieu dien sir phu thugc hdp dung ciia Mm^ tren bentonite vdo then gian lac.
0 0 0 5 S 2 0 2 i 3 0 3 S 4 0 i b
T h o i g 1,1II h
Hinh 5: Sir phu thugc cua hdp dung Fe~^ tren bentonite vdo thai gian lac.
Nhan xet: Tir d6 thi hinh 4 vii hinh 5 co the thfiy rang: Khi thdi gian thay d6i tir 0 -=- 3h, lugng Mn^"; Fe'" bi hfip phu tang theo thdi gian. Sau 3h, dung lugng hap phu khong ddi, dill gia tri cue diii. Qua trinh hfip phu niiy la phan i'mg can bang trao ddi ion:
H^(bentonite) + Mu"" (Fc'"),^, o H".,, + Mn-"(Fe-")(bentonite) (I)
Su chenh lech hoii the ciia Ciic ion ngoai dung dich va trong cac khe xdp tron"
bentonite la dong luc thiic dfiy quii trinh trao doi ion xiiy ra. Liic dfiu, khi n6ng do ion kim loai trone dung dich cao, can bfing chuyen dich sang phiii. Den mot thdi gian nao dd (3h),
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khi hoa the'cua cac ion (H", Mn^", Fe"^) trong vii ngoiii bentonite bang nhau, phim I'rng diit den giii tri can bfmg, khi dd lugng ion kim loiii bi hfip phu lii cue dai d nhiet do va ndng do khao sat.
Ngoai ra, cac ion kim loai cdn bi hap phu vat ly trong nhung khe xdp trung hoa dien tren be mat bentonite. Qua trinh nay dan gian la su khuech tiin ion lir dung dich vao trong 16 xdp chu'a nudc, lugng ion kim loiii eo the khuech tan viio nhung 16 xdp nay la mot hang sd d dieu kien ndng do, nhiet do khiio siit.
Vay thdi gian 3h !a thdi gian ldi uu cho sir ha'p phu ciui Mn va Fe tren bentonite.
4. J .3. Anh hudng cua ndng do chdt bi hdp phu
Pha dung dich M i r " va Fe^" cd n6ng do khiic nhau, tien hanh hfip phu tren bentonite trong khoiing thdi gian 3h sau do Xiic dinh dung lugng hfip phu, Ket quii khao Siit sir phu thugc giua hfip dung ciia Mn (11) trong dung dich tren bentonite viio nong do Mn^" dugc dua ra trong biing 3 vii hinh 6.
Ket quii khao siil su phu thugc giua hfip dung ciia Fe (11) trong dung dich tren bentonite vao n6ng do Fc"" dugc dua rii trong biing 4 va hinh 7.
Bdng 3: Sir phu thuoc cua hdp dung A vdo ndng do Mif^.
M i r "
Q, g/1 Q,, g/1 A
5 3,86 28.56
4 2.88 28.04
3 1.94 26.61
2 1.03 24.32
1 0.29 17.74
0.5 0.04
11.4
0.25 O.OI 6
ihco 11611" do M i i d l J
0 0 3 5 • 15 ;
N , ) i i i : d .
2 5 3 0 3 5 .111:, ^l\
Hinh 6: Sir phu thugc ciia dung lugng hdp phu vdo ndng do cdn bdng trong dung dich ddi vdi Mm^.
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Bdng 4: Sifphu thugc cua hdp dung A vdo ndng do Fc
+ U
Co (g/1) Q„ (g/1)
A
0.54 0.13 10.85
0.63 0.17 11,45
0.72 0.23 12.25
0.9 0.33 19.62
1.56 0,65 20.05
3.31 1.64 25.64
3.68 2.78 26.04
4.73 3.58 26,64
5.1 4.2 26.8
I • A I h e o F e a 11
— 20
< 15
1 2 3 N(MIL; clo T L - d h c m b . l i i - ( g / L i
Hinh 7: Sir phu thugc cua hdp dung vdo ndng do cdn bdng trong trudng hgp Fe'''.
Nhan xel: Tir ciic biing 9,10 vii ciic hinh 9, 10 co the' thity rfmg, dudng dfmg nhict trao doi hfip phu co diing dirdng Langnuiir:
i i . b . C
A +b.C n
Trong dd: A lii hfip dung; a: lugng chfit bi phu cue diii hiiy hap dung cue dai phu thugc vao bim chfit chfit hfip phu, chfit bi hfip phu vii nhiet do; b: hiuig sd; C: ndng do can bang.
Tir can bang iiuo ddi ion: H"(bentonite)+Mn-"(Fe""),^j <=> H",^+Mn-"
(Fe*^^)(bentonite)
Sir triio d6i ion niiy plui thugc viio bim chfit bentonite, nhiet do, sir khuech tiin ion kim loiii, vii kfch thudc lo xdp tren be mat vat lieu, d nhung dieu kien khiio siit chi co nong do ion kim loiii tluiy doi, tiro"ng ling vdi nong do cfin bang hfip phu thay ddi. Do dd:
+ Vdi nhung nong do ion kim loiii nho (C nho) bC ô 1 , hfip dung lang tuyen ti'nh theo C theo mot do thi dui^ng thfmg, bdi khi do sir khuech Uin ciia ion kim loiii hfiu nhu khong bi bien doi.
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4- Khi bC dang ke vdi 1, nong do imh hudng Idn den sir khuech tan ion kim loi;ii A tang theo C dang dudng cong.
+ C Idn, ion Idp sonviit hoa kim loiii Idn, su* khuech Uin ion kim loiii viio trong 16 xdp bi hiin che. Han nu'ii tdng lugng ion cd the trao ddi khdng vugi qiui tdng lugng ion bii trir trong cfiu triic mang bentonite. Nhu vay khi C tang den mgl giii tri niio do A se dat den mot gia tri cue dai, dd thi nfim ngang. Tir d6 thi ta co hfip dung cue diii cua Mu""^ (5g/l) la 28,56mg/g, va 26.8mg/g ddi vdi Fe"".
4.F3 Anh huong cua ty le the tich cua dung dich hdp phu vd khdi lugng bentonite.
Tien hanh thf nghiem hfip phu tuong tu nhu tren, vdi ndng do ciui Mir" l(g/l)va Fe~" la 0,443(g/l), cac budc lien himh tuong tu nhung vdi the tfch ciia dung dich hap phu thay ddi liim cho ty le V|/ni, ihiiy ddi, ket quii thuc nhiem dugc duii ra tren bimg 5 va hinh 8,9.
Bdng 5: Sir thay dot hdp dung A ddi vdi Mm^ vd Fe~^ vdi cdc ty le V,/m, khdc nhau.
+
+
C
V, (ml)
Q „ (g/L)
A (ing/g) V, (ml)
Q„ (g/L)
A (mg/g)
10
0.44 6.19
10
0.99 4.37
20
0.442 9.98
18
0.99 7.24
30
0.417 12.9
30
0.99 11.8
40
0.442 15.5
35
0.99 13,2
50
0.442 17.9
40
0.99 14.5
60
0.442 19.9
50
0.99 17.2
70
0.442 20.9
80
0.99 22.8
80
0,442 21.8
120
0.99 26.1
9
0.443 21,8
150
0,99 27.2
170
0.99 27.2
A I h e o V / m C u a M n
t 1 5
<
8 0 100 V / „ i
Hinh 8: Sifphu thugc cua dung luo'ng hdp phu mg/g tren bentonite vdo ty lc V/m^ doi vdi Mm
24
— " - A I h e o v / m c u a F e 2* - ,
2 2 2 0 18
16
§
< 1 2 10
•iO 6 0 V /m
Hinh 9: Su phu thugc cua hd'p dung mg/g tren bentonite vd ty le Vl/mr ddi vdi Fc''.
Nhan xet: Tir hinh 8 vii 9 cd the thfiy rang, su hfi'p phu tang theo su tang the tich dung dich hfip phu, sau do timg cham vii khong thay ddi khi d6 lii hap phu diit can bang.
Bdi vl, khi the ti'ch dung dich nho lugng ion trong dung dich ft, su hfip phu co xu hudng tang ciing vdi sir tang ciui the tfch dung dich, nhung den mot the ti'ch nao do lugng ion trong dung dich cao hon nhieu so vdi lugng ion bi hfip phu. Khi do neu tang the tfch ciui dung dich thi dung lugng ciing kh6ng lluiy doi iiCra, dung lugng hfip phu diil gia tri cue dai. Tir do thi cd the thfiy luiig, vdi khdi luo'ng ciui bentonite Iii 2g, vii ndng do ciui Mn^"
va Fe-" la l(g/I) ; 0,443(g/l) ihi ty le V|/m, lot nhfit cho su hfip phu Ifin lugt la 75 vii 40.
Tdm liii: dieu kien tdi iru cho qiui trinh hfip phu ciic ion Mir" \'a Fe"" tir dung dich nudc la:
- pH dung dich tdi uu la 4,0 - Thdi gian lac: 3h
- Ty le the tfch dung dich (ml)/ khdi lugng benlonite (g) (V|/m,,) de hfip dung dat cue diii (vdi khdi lugng ciia bentonite Iii 2g, ndng do ciui .Mn"" vii Fc"" la Ig/I ; 0,443g/l) hui lugl la 75 vii 40.