DAI HOC QUOC GIA HA NOI
TRUING DAI HOC KHOA HOC Tl/NHIEN
^ : ) : ;J: ^ ^; ^ Jj: ^' -.'^ -N ^ ^ ^ -1^ ^ ^ ^ :i^ ^ ^
BAO CAO DE TAI
KHAO SAT PHUONG PHAP XlTLI L A M
N A N G HAP T H U CAC
TANG KHA
ION KIM LOAI NANG TRONG
NUdc CUA K H O A N G
BENTONITE
VIET NAM
Ma sd:
Chii tri de tai:
PGS. TS. Ng6 Sy Luang
Can bg phdi hgp:
1. TS. Than Van Lien
2. ThS. Ha Van Van
3. ThS. Pham Van Tien
4. CN Nguyen Thuy Mai
DAI HOC Q U O C GlA HA NOi
TPUNG TAt^ THOr.'G TIN THO VlFN
DT J4 t
Ha Noi 2005
PHAN L BAO CAO TOM TAT DE TAI BANG TIENG VIET
1. Ten detai:
Khdo sdt phuang phdp xir ly ldm tdng khd ndng hdp thu cdc ion kim logi ndng trong
nUdc ciui khodng bentonite Viet Nam.
Ten tieng Anh:
Research of treatment method to improve the ability of absorption for heavy metal
ions on Vietnamese bentonite.
2. Chu tri de tai: PGS. TS. A^^^ Sy Luang
Hgc ham, hgc vi: PGS. TS.
Dan vi cong tac: Khoa Hod hgc
Tel: 8241169
3. Cac can bg tham gia de tai:
1. TS. Than Van Lien
2. Thac sy Ha Van Van
3. Thac sy Pham van Tien
4. CN Nguyen Thuy Mai
4. Muc tieu va ngi dung nghien cuu:
Bentonite la loai khoang set tu nhien, cd cau true Idp, cd dicn tfch be mat Idn nen cd
khci nang hap thu tu m6i trudng nudc nhieu chat v6 ca va huu co. Vl vay bentonite dugc ung
dung trong nhieu ITnh vuc cd lien quan den kha nang hap thu cua no: xu li moi trudng, lam
sach cac chat Idng khoi cac tap chat, che dung dich khoan, lam chat don. ..
Nudc ta cd triT lugng bentonite tuong ddi Idn, gdm mot sd mo nhu: Di linh - Lam
Ddng, Thuan hai - Binh thuan, v.v.. Theo danh gia sa bg ham lugng montmonllonite trong
khoang bentonite cua nudc ta kha thap. Vi vay viec nghien cuu cac phuong phap lam tang
ham lugng montmorillonite, ddng thdi hoat hoa de lam tang kha nang hap thu cua loai vat
lieu nay nluTm muc dich tang kha lulng su dung ngudn tai nguyen nay phuc vu cho cac nganh
kinh te qudc dan la mot van de rat dang dugc quan tam.
Mot trong nhung ung dung quan trgng cua khoang bentonite la sir dung nd lam vat
lieu hap thu ion kim loai nang trong ITnh vuc xu If n^oi trudng nude. Do vay, viec nghien cuu
cac phuong phap hoat hoa lam tang kha nang hap thu eua bentonite ddi vdi cac ion kim loai
nang la mdi quan tam cua nhieu nha khoa hgc trong va ngoai nude.
Bentonite cd mat trong dat, do cd kha nang hap thu nen nd hoat dons nhu cac ludi loc
tu nhien. Khi nudc tham qua cac Idp dat thi bentonite giiTr lai cac ion kim loai \'a cac chat huu
CO. Vi vay, bentonite tu nhien bao gid cung da chi'ra sfin (du ft hoac nhieu) mot lugne nhat
dinh cac chat da bi hap thu va vice loai bd cac chat nay de lam tang kha naiio hap thu cua
bentonite trudc kin sudung la nhiem vu quan trgng.
De lam tang ham lugng ciia montmorillonite trong khoang bentonite, ngirdi ta thudni
sir dung cac phuang phap tuyen khoang va phuang phap thudng dugc sir dung la tuyen trgn^
luc. Hien nay cd mot sd phuang phap mdi dugc ap dung, vf du nhu tuye'n bang xyclon.
De hoat hoa lam tang kha nang hap thu cua bentonite, ngudi ta thudng su dung mot sc
phuong phap sau:
- Phuang hoat hoa bang nhiet: Dicing nhiet do cao de loai nudc hap phu, loai cac cha
huu ca khoi khoang bentonite.
- Phuang phap hoat hoa bang dung dich kiem: Dung dung dich kiem cd ndng do thfcF
hgp de xu If khoang bentonite.
- Plurang phap hoat hoa bang dung dich axit vo ca: Dung dung dich axit v6 co (thudng
la axit sunfuric, axit clohydric) cd nong do thfch hgp di xu If khoang bentonite.
Ccic phuang phap hoat hoa ndi tren dugc su dung mot each thfch hgp tuy theo thanh
phfin, ham lugng montmorillonite trong bentonite va dac biet la tuy thugc vao muc dfch sii
dung. Trong dd phuang phap hoat hoa bang cac dung dich axit sunfuric la dugc su dung
nhieu nhai va cd hieu qua nhat.
4.L Muc tieu nghien cuu
- Ddi tugng nghien cuu la bentonite vung Di Linh - Lam D6ng va vising Tuy Phong Binh thuan. Day la nhung vising co khoang bentonite co tru lugng thugc loai Idn nhat nude ta
hicn nay.
- Tim phuoug phap thfch hgp nang ham lugng montmorillonite trong bentonite.
- Tim dieu kien tdi iru cho qua trinh hoat hoa bang axit nham lam tang kha nang hap
thu ciia bentonite ddi vdi cac ion kim loai nang trong mdi trudng nirdc. Nhu vay san pham
bentonite sau khi hoat hoa nham muc dfch xu If moi trudng: tach loai cac ion kim loai nans
tu moi truoug nuac,
- Khao sat kha nang hap thu cac ion kim loai nang ciia bentonite trong dung dich
nudc.
4.2, Ndi dung nghien cuu.
- Phan tfch thanh phfin khoang va thanh phan hoa hgc cua man bentonite nghien ci'ru.
- Kluio sat phuang phap lam sach va hoat hoa bentonite bang axil H^SOj cd ndng do
va dieu kien thfch hgp de lam tang kha nang hap thu cac ion kim loai nang tromz nude.
- Khao sat kha nang hap thu ciia bentonite sau khi xu ly va so sanh vdi kha nang hap
thu ciia bentonite nguyen khai chua xu ly.
5. Ciic kel qua da dat dugc
g. Anh hudng cua cdc chdt dien li trong moi trudng nudc
Chuang II. Phuang phap nghien cu*u
2.1. Phuang phap hoat hoa quang
2.2. Phuang phap phan tfch thanh phan hoa hgc ciia bentonite
a. Xdc dinh hdm SiO^
b. Xdc dinh hdm FeiO:^
c. Xdc dinh hdm luang AFOj
d^Xdc djnh MgO vd CaO
2.3. Phuo'ngphdp xdc dinh sdt, mangan trong dung dich
a. Phuo'ng phdp trdc r/uang xdc dinh ndng do ion sdt trong dung dich vdi thudc
thir thioxianat.
b. Xdc dinh mangan bdng phuo'ng phdp trdc c/uang
2.4. Phuang phap xac dinh hap dung cua cac ion kim loai tren bentonite
Chuang III - Ket qua va thao luan
3.1. Khao sat cac yeu td anh hirdng den kha nang hap phu cac ion kim loai nang
trong moi Irudng nirdc cua bentonite.
34.FF Anh hudng cua pH dung dich dcdi khd ndng hdp phu Fc'^ vd Mm^ tren
bentonite.
3.1.2. Anh hudng cua thdi gian khuay tdi sUhdp phu Mm^vd Fc'^ tren bentonite
3.1.3. Anh hudng ciia ndng do chdt bi hdp phu
3.F3. Anh hudng ciia ty le the tich ciui dung dich hdp phu vd khdi lugng
be/itonite.
3.2. Mau khoang bentonite sir dung de nghien cuu
3.3. Khao sat qua trinh hoat hoa bentonite
3.3.1. Logi axit
3.3.2. Ndng do axit
3.3.3.
TvleRIL
3.3.4. Nhiet do hogt hod
3.3.5. Tdc do khuay tron
3.3.6. Thai gicm hogt hod
Ke't luan
Tai lieu tham khiio
MOiDAU
Bentonite la loai khocing set tu nhien, cd ca'u tnic Idp, co dien tfch be mat Idn nen
cd kha nang ha'p phu nhieu chat vo ca va hxiu ca [1,51. Vi vay bentonite la loai vat lieu
dugc ii'ng dung trong nhieu ITnh vuc khac nhau.
Nudc ta cd tru lugng bentonite tuang ddi Idn, d mot sd mo nhu: Di linh - Lam
Dong, Thuan hai - Binh thuan, v.v.. Quang bentonite Viet Nam cd ham lugng
montmorillonite kha thap, chat lugng kem, do do viec nghien cuu lam tang chat lugng de
cd the sir dung tdt han ngudn lai nguyen nay de phuc vu cho cac nganh kinh le qudc dan
la mdt va'n de ra't dang quan tam.
De tang cudng cha't lugng cua khoang bentonite, cd hai van de can dugc tien hanh:
- Lam tang ham lugng montmorillonite trong khoang bentonite. Giai doan nay
thudng ditgc tien hanh bang cac phuang phap tuyen khoang th6ng thudng, chu yeu la
phuang phap tuyen trgng luc.
- Hoat hoa khoang bentonite sau khi lam giau de tang kha nang hap phu cua no. De
hoat hoa bentonite, ngirdi ta thudng sir dung cac phuang phap hoat hoa nhict, hoat hoa
bang dung dich kiem, hoat hoa bang dung dich axil, trong dd phirong phap hoat hoa bang
dung dich axit vo ca, nlur H2SO4, HCl dirge sir dung ph6 bie'n nhat.
De danh gia chat lugng bentonite sau khi lam giau va hoat hoa, phuang phap phd
bie'n la danh gia qua kha nang hap phu cua bentonite ddi vdi cac ion kim loai nang trong
dung dich nirdc. Dong tlidi muc dfch sir dung bentonite lam vat lieu hap phu tach loai cac
ion dd khdi m6i tnrdng nudc gdp phfin chdng 6 nhiem m6i trudng cung la mdi quan tam
hang dau ddi vdi cac nha nghien cuu trong nirdc va tren the gidi trong ITnh vuc nay [5-8].
Xuat phat tu y tudng do, chung t6i dat van de khao sat kha nang lam giau va hoat
hoa bentonite bang phuong phap axit, cu the la H2SO4. Muc tieu nghien cuu dirac dat ra
trong de tai nghien cuu nay la tim dugc phuong phap xu If lam tang kha nang hap phu cua
bentonite ddi vdi cac ion kim loai nang trong in6i tnrdng nudc.
Cac ngi dung nghien ci'ru dugc dat ra trong de tai nghien cuu nay la:
- Phan tfch thanh phan khoang va thanh phan hoii hgc ciia mau bentonite nghien
cuu.
- Khao sat phuong phap lam giau dc tang ham lugng montmorillonite trong khoan"
bentonite.
- Khao sat phuang phap xu ly axit H.SO^ cd nong do va d dieu kien thfch hop de
lam tang kha nang hap phu cac ion kim loai nang trong nudc.
- Khao sat kha nang hap phii cua bentonite sau khi xu ly va so sanh vdi kha nang
hap phu cua bentonite nguyen khai chua xu ly.
Cac thf nghiem nghien cu*u ciia de tai nay dugc tien hanh d phong thf nghiem Vat
lieu mdi thugc bg mon Hoa Vo ca - Khoa Hoa hgc - Tnrdng DHKHTN - DHQG HN va
phdng thf nghiem thugc Trung tam Xu If quang - Vien C6ng nghe Xa - Hiem thugc Vien
Nang lugng nguyen tir Viet Nam. Kinh phf cua de tai dagc DHQG HN cap qua de tai cap
DHQG mang ma sd . Chung t6i xin chan thanh cam an DHQG HN da cap kinh phf de
chung toi hoan thanh cac ngi dung nghien cuu cua de tai nay.
4
CHUONG I.
GICJI THIEU VE BENTONITE
I.GI6I THIEU VE BENTONITE
LI Thanh phan hoa hgc cua bentonite.
Bentonite la loai khoang set tu nhien, co thanh phan chfnh la montmorillonite. Vi
vay cd the ggi bentonite theo thanh phfin chinh la montmorilonite. Cong thuc dan gian
CLia montmorillonite ALOv4Si02.nH20 I'mg vdi nua te bao don vi cau tnic. Cong thuc ly
tudng cua montmorillonite la SiyAl402o(OH)4 cho mot dan vi ca'u tnic. Tuy nhien thanh
phfin cLia montmorillonite luon khac vdi thanh phan bieu dien ly thuyet do cd sir thay the
ddng hinh cua cac ion kim locai nhu Fe"*"", Fe^"^, Mn""".... vao vi trf cua Si"*"" trong tu dien
Si04 va ciia Al"^^ trong bat dien AlO^
Nhu vay thanh phfin hoa hgc montmorillonite, ngoai sir co mat cua Si va AI, ta cdn
iha'yeo sir xua't hien ciia cac nguyen td khac nhu: Fe, Zn, Mg, Na, K, v.v.. , trong do ty le
ALQvSiO.tu 1:2 den 1:4.
Ngoai thanh phfin chfnh la montmorillonite, trong bentonite con chua mot sd
khoang set khac nhu liectorit, saponit va mgl sd khoang phi set: canxit, pirit, manhetit, cac
mudi kicm va mot sd cha't huu ca khac.
1.2. Cau tnic cua montmorillonite
Trong c6ng thi'rc ly lirdng cua montmorilonite, cac nguyen tu Si nfim d mang tu
dien, con cac nguyen tu Al nam d tam mang bat dien (trong tnrdng hgp mang nhom
silicat la trung hoa dien) va cong thi'rc khai trien cua nhu sau hinh 1.
O
o ^ ^o
o
. : Si1ic
o
o
O : O xI
Hinh!. Cong thirc khai trien khong gian ciia montmonllonite li tirdng
Do montmorillonite cd cau tnic 2:1 dang diocta nen cau tnic lap montmorillonite
da dugc hinh thanh tir hai mang tir dien lien ket vdi mot mang bat dien d giua, tao nen mgl
Idp nhdm silicat vdi cac khe trdng d giua. Cac cation co kha nang trao d6i bi hydrat hoa
va nudc bi ha'p thu cd the chie'm cho d cac khe trdng giua cac lap nhom sislicat. Chieu
rdng CLia khe trdng giiJa cac Idp cau tnic ca ban ciia montmorillonite la 9,6 A, chidu rong
dd cd th^ bi thay ddi ft hay nhieu tuy thugc vao sd lugng, ban chfi't cation trao doi va
lugng nude hap thu, thudng c6 the den 15 A. So d6 ca'u tnic khong gian mang lircri ciia
montmorillonite, dugc trinh bay tren hinh 2, la mgl cau tnic trung hoa dicn. Neu Si"^^ ti'r
dien hay AL"^ bat dicn bi thay the dong hinh bdi cac cation duong thap hon thi cac phan
mang dd tfch dien am. Dien am cao hay thap tuy thugc vao sd lugng va ban chat cua cac
cation thay the. Dien tfch am cua mang se dugc bi^i tri^r bang cac cation mang dicn tfch
duang Na"^, K"*^, Ca^"^, Fe""^, Mn""^... d khoang kh6ng gian giua cac Idp. Nhu vay kha nang
trao ddi cation cua montmorillonite la tuang dirang vdi dien tfch ciia cac Idp.
Ci* i i o o
O.Va « SLLLc J h o j c
trs.c
^ i
-f nW^c
nhom
Hinh 2. Sa dd cdu true khong gian nigng ludi cua montmorillonite
1.3. Cac kha nang bien tinh Bentonite
7.3.7 Bien tinh giir nguyen cdu true cda lop aluniinosilicat
Dac trung ca ban cua bentonite la tfnh chat trao ddi. Tfnh chat dd cd dugc la do sir
thay the ddng hinh Si'*'' bang Ah^"*" trong mang ti'r dien va Ah^^ bang Mg""" trong mang ludi
bat dien lam xua't hien dien tich am trong mang ludi cau true. Kha nang thay doi manh
hay yeu phii thugc vao lugng dien tfch am be mat va sd lugng ion trao ddi. Neu sd lugng
dien tfch am be mat cang Idn, sd lugng cation trao ddi cang Idn thi dung lugng trao d6i
cLia bentonite cang Idn.
Kha nang trao ddi ion ciia nhdm silicat con phu thugc vao dien ti'ch va ban kfnh
cation trao doi. Dien tfch cation cang thap thi cang de trao ddi hon cation dien tfch cao
Me^>Me2-^>Me^L
Ddi vdi Ccic cation ciuig dien tfch, ban kfnh cang nho thi kha nang trao d6i cang
Idn cd the xap xe'p theo trat tu sau Li > Na > K > Cu > Fe > Al.
Tuy nhien kha nang trao d6i cua nhom silicat chii yeu van phu thugc vao dien tfch
am be mat va luanc dien tfch am iron" manti ludi. Bentonite ^6m be mat Irons va be mat
ngoai. Kha nang trao doi ion be mat ngoai phan anh kfch thudc tinh the, phu thugc vao
kfch thudc tinh the, phu lhuoc vao su di'rt gay lien ke't va khuyet tat be mat. Kfch thudc hat
cang nhd thi kha nang trao doi cang Idn. Kha nang tiao d6i be mat trong phan anh lugng
dien tfch am trong mang ludi va khii nang hfip phu cua bentonite. No phu thugc vao lugng
cation bu tri^r trong mang ludi. Sd lugng cation cang Idn ihl kha nang trao dcii cang Idn.
Dung lugng cation dao dong lir 80 -^ 150 mgdl/lOOg. Dung lugng trao ddi anion dao dong
tu 15H-40mgdI/100g.
Ngoai ra, sir trao doi ion ciia bentonite con lien quan den sir thay the cac nguyen lir
hydro trong cac nhdm hydroxyl ciia montmorilonite. Theo mot sd nghien ci'ru, dinh ciia
cac tir dien Si04 hirdng ra phfa ngoai ciia Idp cfi'u true. O dinh nay cac nguyen tir ciia oxy
bi thay the bdi cae nhom hydroxyl va cac nhom nay dam nhiem viec duy tri lien ket yeu
giua Ciic Idp va gop phfin vao su can bang dien ti'ch. Trong montmorilonite con co cac
nhdm hydroxyl nfim d dinh ciia cac bat dien AlO^. Trong sau dinh ciia bat dien co hai
dinh la nhom OH cdn bdn dinh kia la oxy( hinh3).
0
OH
.OH
/
0
0
0
I
I
I
I
Al
\
1
0
0
I'
II
H
d
1
1
0
6^-A/
0
1
in
/
\
? f
Hinh 3. Vi ni ciiu ciic nlioni OH c6 rroiii; maii;.^ luai can Hue ciia
l)eiiionlfe
Trong dd nhdm hydroxyl ciia lien ket
Si-OH (1) kh6ng co kha nang trao doi
hydro, nhdm hydroxyl trong lien ket Al - 0H(11) cd tfnh axit yeu nen kha nang trao doi
yeu. Nhdm hydroxyl trong lien le't Si-0-Al(l 11) cd tfnh trao ddi manh nen cd tfnh quyet
dinh den dung tfch trao doi cation H"'.
1.3.2. Bien tinh ldm bien ddi cdu triic Idp aluniinosilicat
Khoang bentonite tu nhien chi'ra nhieu tap chat nhu cac mudi can xii (CaCOO,
dolomit (MgC03), mot sd oxyt: FcjO^ , FeO, Ti02, v.v.. va cac tap chat khac.
Qua trinh hoat hoa bentonite dugc thuc hien bang each dimg kiem hoac axit hoa
tan mot sd oxyt luang tfnh nhu AI2O3, Fe203, de tao tren be mat set nhung 16 xdp va trung
tam hoat dong, Viec sir dung nong do kiem hoac axft cao cd kha nang hoa tan nh6m oxyt
lam thay doi cau true bentonite.
1.4. Dac tinh cau true bentonite va kha nang hap phu
Chfnh V] bentonite co ca'u tnic Idp va do phan tan cao nen no cd cfiu true xdp phuc
tap va be mat rieng Idn. Ca'u tnic xdp anh hudng rat Idn de'n tfnh cha't hap phu ciia cac
cha't, dac iiung ciia nd la tfnh chat chon loc chat bi hfip phu. Chl co phan tir nao cd dudng
kfnh dii nhd so vdi 16 xdp thi mdi chui vao dugc de tham gia va qua trinh ha'p phu. Dua
vao dieu nay ngudi ta cd the tien hanh hoat hoa sao cho co the diing bentonite lam vat lieu
tach chat. Day cung la diem khac nhau giua bentonite va cac chat ha'ji phu khac.
Nhd du dicn tfch tren cac nguyen tir ciia cac nut mang tinh the eho nen bentonite la
mot chat hfi'p phu phan cue va vl vay no se uu tien hfip phu cac chat phan cue. Tuy nhien,
bentonite van cd the hap phu cac chat khong phan cue do lire van der Walls va tuang tac
hfip phu chii ye'u la tuang tac cam ung. Be mat bentonite eo dien tfch tuong ddi Idn bao
gdm be mat ngoai va be mat trong. Be mat trong bao g6in be mat ciia cac lap nhom silicat
chdng len nhau va dugc ngan each bang cac cation kim loai den bu dien tfch tren be mat
Idp bentonite. Be mat ngoai dugc xac dinh bdi be mat ciia cac mao quan chuyen tiep. Cac
mao quan nay dugc lao nen do su tiep xiic ciia cac hat bentonite va cd kfch thudc khoang
40 A -^ 90 A. Dien tfch ciia be mat ngoai phu thugc vao kfch thudc cac hat bentonite, hat
cang nhd thi dien tfch be mat ngoai cang Idn. Kha nang trao ddi ion Idn cung vdi kha
nang hfip phu tdt ma ta cd mgl loai vat lieu xir ly kim loai nang ra't hieu qua tir bentonite.
II. NHUNG UNG DUNG CHU YEU CUA BENTONITE
Do cd kha lulng hfip phu lot nhieu cha't v6 co va hiru co, nen bentonite cd nhieu Uim
dung kha da dang va phong phii trong sir phat trien ciia xa hgi.
2.1. Sudung bentonite lam chfit hap phu
Bentonite dugc dung rong rai trong nhieu nghanh cdng nghiep vdi vai trd la chat
hap phu:
Trong cong nghiep lgc dau, lugng bentonite dugc sir dung rat Idn, bao gom
bentonite tu nhien va bentonite da hoat hoa. Lugng bentonite tu nhien lieu tdn cho qua
trinh lgc dau la 25% lugng dau phai lgc ciing vdi mgl lugng bentonite da hoat hoa bang
10% khdi lugng dfiu.
Trong cong nghiep tinh che dfiu thuc vat de xan xua't dau an, md, bo, xa phong,
viec SIX dung bentonite lam chfit hfip phu la uu viet han han phuang phap cu la phirong
phiip ririi kiem. Lugng bentonite mfit di trong qua trinh tinh che chi bang 0,57t: lugng dfiu
dugc tinh che'. Ngoai ra phuong phap dimg bentonite con co muc hao phf dfiu thfip do
tranh dugc phiin ung thuy phan
Trong cong ngiep dieu che' than cdc phuc vu cho cong nghiep luyen kim, bentonite
dugc sir dung de tinh che benzen tho vfi ciic ban sfin phfim khac.
Nhd CO dac diem hfip phu dac biet tdt, bentonite con dugc sir dung rong riii de si'ui
xufit nhien lieu long t6ng hgp, xiin xufil cfic chfit mau, xiin xufit ciic vitamin...
2.2. Sii dung bentonite de che dung dich khoan
Benlonite co the' liio ra ciic dung dich khoan vdi chfit lugng dac biet ciio va chi phf
nguyen lieu thfip. Vl the, cimg vdi vice phi'it trien ciui ngiinh tham do va khai thiic dfiu,
lugng benlonite sir dung cho viec che tiio dung dich khoan ngiiy cang lang. Ngiiy nay d
My, lugng bentonite sir dung cho vice che tiio dung dich khoan chicTn tdi 40% t6ng siin
lugng bentonite ciia nudc nay.
2.3. Sii dung bentonite lam chat dgn, chat mau
Trong cdng nghiep siin xufit Ci'ic vat lieu t6ng hgp. Vlgt lugng Idn ciia bentonite
dimg cho cdng nghiep xa phong, c6ng nghiep xiin xuat viii sgi. Vice sir dung bentonite
trong Viii thap ky gfin day cung da liim thay doi dang ke nganh c6ng nghiep gifiy. Trudc
kia gifiy thudng chua sfip xi 55% xenlulo vfi ham lugng ciiolin nguyen chfit cd trong giay
khong the" vugt quii 45%. Neu iron them 10% benlonite kiem (cation trao ddi la kim loai
kiem, chii yeu la Na"") viio caolin thi co the nang ham lugng chfit don nixy len tdi 60%;
Neu tron them 207o bentonite kiem thi ham lugng chfit dgn co the' nang len diin 64% va
neu dimg 100% bentonite thi chfit dgn len tdi 84%, nghTa la giiim lugng xenluno cfin co
trong giiVy di ba \i\n.
2.4. Sir dung bentonite trong cong nghiep ruou bia
Viec sir dung bentonite hoiit hoii liun chfit hfip phu da lam giam 3(}9( den 40% chi
phf cong nghiep che bieii rugu vang vii ciic che pham ur rugu \ ang. Bentonite co kha nang
hap thu khong chi cac axft hiru ca, ciic cha't beo, cac san phu khong mong mudn trong qua
trinh len men ma cdn cii ion sat va ddng lii nhij*ng tac nhan gfiy ra benh ha rugu. dac bietm
trong qua trinh xir If vdi chat ha'p phu la bentonite thi huong vi rieng ciia rugu khong bi
mat di.
2.5. Sir dung bentonite trong cong nghiep tinh che nudc
O nhieu viing chua cd nha may nudc tren the gidi viec sir dung bentonite de lam
sach Ciic ngudn nudc mat, nhu nudc song ngdi, kenh muang va ciic ngudn gieng khoan cd
y nghTa thuc tien quan irgng. Bentonite ddng thdi liim kel tiia cac \'an due, ihiiy cho viec
dimg phen dat hon nhieu, ma nd cdn cd kha nang hfip phu mgl loiU cac ion gfiy dgc va
mdt luan" Idn cac vi khufin, chfit huu co cd trong nudc. Bentonite U\ mdt chat trao doi cd
trong tu nhien, nd cd kha nfmg khir tfnh cung ciia nude vdi giii thiinh tuo'ng ddi re. Kha
nang lang cdn \a lirng trong nudc, ddng thdi vdi tiic dung trao doi ion va hfip phu chfit huu
ca, trong dd cd cac vi khuan gay benh tiio ra gia tri dac biet ciia bentonite trong cong nghe
sir ly nude.
2.6. Mot sd ling dung khac cua bentonite
Cung lir Ciic di)c tfnh ciia bentonite iii tfnh tnrang nd manh, tfnh deo ngirdi ta cdn sir
dun" bentonite tronc Ciic coniz trinh thuy loi nhu de dieu iniroim mi'uie va nlu~rng cong
trinh phdng thii bfmg dfit. Vdi khi\ nang chiu dugc nhiet do cao, benlonite dugc diing liim
tiic nhan lien ke'l trong siin xufit dan va liim khu6n diic. Dac biet bentonite cdn dugc diing
lam phu giii trong thiic an lieu hoii cho dong vat, vdi vai trd tang thdi gian luu Irir thu'c an
trong ca quan tieu hoa giiip tieu hoii thi'rc an vfi giiip dieu tie't axit. Bentonite cdn dugc sir
dung liim chfit chdng fim bang ciich sfiy kh6 vii do dac tfnh hiil am trd lai mil co irng dung
nfiy (bentonite cd khii nang hfip phu lugng nude gfip khoang 10 Ifin khdi lugng ciia
chiing).
Do nhung irng dung phong phii ciia bentonite ma tren the gidi ngudi ta ed nhu cau
khai thac va sir dung bentonite rfit Idn. Nam 1995 lugng sfm phfim tir bentonite dugc udc
lugng tuoug ddi chfnh xiic Iii 9,8 trieu tfin, trong do My la nirdc sir dung bentonite thuan
Na nhieu nhfit. Ciic nudc khiic nhu Hy Liip , Thd NhT Ky. Due cimg vdi My tieu thu
khoiing 84% t6ng siin lugng bentonite tren loiin the gidi, trong do Australia dong gdp mot
nirii sd niiy. Nam 1985, t6ng siin lugng bentonite va set dugc udc iinh viio khoiing 1452
trieu tfin set dimg de ho viii. Gia thimh ciia bentonite vao nam 1997^1998 la vao khoang
98 USD/tfm, sau do, do nlui cfiu thay d6i himg nam ma giii beionit dao dong tir 50 -^
250USD/tfm.
0
Viet Nam c6 Ciic md cd tiu lugng Idn nhu: Tam Bd - Di Linh - Lam D6ng; Thuan
Hai - Binh Thuan; Gia Quy - Long Dfit - D6ng Nai. Trong dd mo Tam Bd - Di Linh Lam Ddng dugc udc tfnh cd tru lugng len tdi 24.10^' m-^ va da dugc lien himh tham dd ty
my, bat dfiu khai thac quy mo cong nghiep nen chung t6i chgn mau bentonite co nguon
gdc Di Linh - Lam D6ng de nghien ci'ru.
III. CAC PHUONG PHAP HOAT HOA BENTONITE
Bentonite tu nhien da lii mgl chfit hfip phu trao doi nhung dc nang cao tfnh hfip phu,
tfiy trfing vii hoiU tfnh xiic Uic ngirdi ta cfin tim Ciich lam tang be mat ciia no. Tfil Cii cac
Ciich lam vdi muc dfch nhu vay dugc ggi la sir hoiil hoa benlonite. Cd nhieu phirong phiip
hoiit hoii bentonite ap dung cho tirng loiii bentonft vii muc dfch hoiit hoii, nhung co ba
phuong phiip chfnh la: hoiU hoil biuig kiem, hoiit hoa bang nhiet vii hoiit hoii bi-ing axit v6
ca.
3.1. Hoat hoa bang nhiet
Nguyen tiic ciia phuong phiip nay lii dimg nhict de tach nudc lien ket ra khoi miing
ludi tinh the ciia dfit set va ddt chiiy Ciic chfit bfin, chfit miin Irong do, ddng thdi liim riin
mil mgl phiin cac tinh the dc tao thiinh trong niiing ludi dfit set nhung khe lanh liim ti'mg
be mat va tang do xdp.
Nirdc lien ket bat dau hi tiich la d ngiiy nhiet do thfip (^1 10" C) va den khoiing
200"C till CO the tiich ra hoiin toim.
Tuy vay, khi hoiit hoii bentonite bang nhict, kh6ng dugc nung den nhiet do qiui cao
vl d Ciic nhiet do cao bentonite sc bi giiim kh;i nang hfip phu vii la}' trang. Ddi vdi moi loiii
dfit set thf ed khoimg nhiet do thfch hgp rieng thudng tir khoiing 110-150'^C.
3.2 Hoat hoii bang axit vo co
Day la phuong phiip hoiit hoii bentonite hieu qua nhfit nen thudng dugc sir dung
mot Ciich rgng rai trong thuc le. Trong quii Irlnh hoat hoii bentonite bang axit, ngudi ta co
the dimg Ciic axit vo ca thong dung nhu: HCl, HNO3, H2SO4.
Trong nhung axit do Ihl tac dung ciia HCl la miinh nhat, vl ngoai khii nang hoa tan
Ciic oxit kim loiii no con khii nang hoii tan mot phfin SiOi d nhiet do cao. Tuy vfiy. HCl de
bay hoi nen gfiy kho khan cho thao tac hay dieu chinh nhiet do. Tuy vay, lgi dung chfnh
die'm ye'u niiy mil nguoi ta sang che mot day chuyen hoiU hoii bentonite bang HCl. trong
do cho phep thu hoi va tai sir dung HCl de liim giiim chi phf, tang hieu quii kinh te. Khii
nang hfip phu, ti"iy trfmg va ho;it ti'nh xiic tiic ciia bentonite da hoiU hoa phu thugc rfit nhieu
vao dieu kien hoat hcxi nhu: bim chfit axit hoat hoa, nong do iixit dimg cho hoat hoii, thdi
cian hoat hoii, tv le bentonite tren axit, nhict do hoat hoii, do phan tan cua bentonite, v.v..
Mdi yeu td deu cd anh hudng nhat dinh den chfit lugng cua bentonite hoiit hoii. De nghien
CUU
' iinh hirdng cua mot ye'u td nao dd ngudi ta thudng dung phuong phiip c6 lap, nghTa lii
cd dinh cac yeu td cdn lai. Ddi vdi moi loai bentonite va vdi mdi muc dfch ngirdi ta se tim
thay mot dieu kien thfch hgp nhat de hoiit hoa bentonite mot ciich tdi uu nhfit de cho nd cd
kha nang hap phu tdt nhfit.
3.3. Hoat hoa bang kiem
Diing kiem hoa tan mot sd oxit ludng tfnh nhu: ALO3, FC2O3 de tiio tren be milt
nhung 16 xdp vii trung lain hoat dong. Tuy nhien mgl sd lien ket nh6m silicat bi dirt tiio
ca'u tnic khac va mot sd chfit khiic kh6ng bi hoii Um bi loiii do sa lang. Miit khac khi hiim
lugng kim loiii kiem Idn thi hoiU tfnh xiic tiic ciia nh6m siliciit gii\m do ion Na dfiu doc
cac tam axil. Do vay phuang phiip hoiit hoii bang kiem ft dirge dimg, chi trong nhung
trudng hgp dac biet nao do ngudi ta mdi sir dung phuang phiip niiy.
3.4 . Phuong phap khac
Hoiit hoii bang chfit huu co: tii biet rang ditt set thong thudng d dieu kien tu nhien
hay hoiit hoii bang chat vo ca, thudng hfip phu chii yeu chiit 6 nhiem v6 cc^, nha vao khii
nang bien ddi ciia no vdi chi'it v6 co'. Nhung ngiiy nay chfit 6 nhiem huu co ngiiy cimg
nhieu chfit 6 nhiem huu co do sir phiit tricn ciui khoa hoc ky thuat, nhieu ngimh cong
nghiep, giao thong van tiii,... VI vay, de hi'ip phu Ciic chfit huu co tii phiii lien hanh hoiit
hoa da't set vdi chfit huu co. Chfit huu co d day thudng dimg lii chfil hoiit dong be mat. Khi
da't set dugc hoiit hoii bang chfit huu co' no tiio tren be mat ciiii dfit mot Idp bao phii tdi uu
cua chfit huu ca tren be mat dfit set. VI vay, nd co khii nang bien doi vdi ciic chfit huu ca.
Vdi sir hoiit hoii vdi chfit huu co thfch hgp, no co the tao ra mot cha'l hfip phu dong thdi cii
chfit huu CO vii vo ca mii kh6ng cd sir ciinh tranh, bdi vl chiing hfip phu ddng thdi len Idp
be iriiAt. Kim loiii khong nhung di viio miing ludi ciia dfit nhd nhung khoang trdng chua bi
che Ifip bdi nhung chfit huu co', ma cluing con Uio lien ket vai nhung nhdm chuc cua chat
huu CO. Til)' nhien hiin che' la chat hoiit dong be miit kh6ng cd nhieu trong c6ng nghiep.
4. SLT HAP PHU CAC ION KIM LOAI N A N G TL/ MOI TRU(:)NG NUOC COA BENTONITE
4.1. Co che hap phu
Quii Irlnh hiT'p phu tren bentonite dugc thuc hien theo hiii each khac nhau |9,10|:
a. Hfip phu cation vao khe giuii ciic Idp: Do bentonite co cfiu tnic lap, hii cd the co
su thay the cac ion AI^^ va Si'"'' trong mang ludi ciia bentonite bang cac ion cd dien ti'ch
duong be hou lam cho niiing ludi mang dicn ti'ch am. d6ng thdi tren be mat ciia cac lap eo
the cd t6n tai Ciic nhom OH co khii nfmg trao d6i ion H^ ddi vdi ciic cation cd mat trong
12
dung dich nudc. Viec hfip phu cac cation vao trong viio trong ciic khe giua cac lap phu
thugc vao kfch thudc ciJa khe trdng, kfch thudc ciia ciic cation, ban chat cua cation.
b. Ha'p phu cac ion len tren be mat ciia cac hiit bentonite: trong trudng hgp nay, cac
cation cd tham gia hinh thimh cac phirc chat cfiu ngi thdng qua nhom Si-O" va Al-O' Uii
be mat cua bentonite. Trong trudng hgp nay cd the co cii sir su tnio ddi ion vii hfip phu
bang luc van der Walls. Vi vay dung htgng hfip phu trong Inrdng hgp nay phu thugc nhieu
vao dien tfch be mat cua hiit bentonite.
Ca hai kieu hap phu tren deu dugc thuc hien trong dieu kien m6i tnrdng axit yeu
(pH<4).
Bdi vl quii trinh hfip phu lii toil nhiet nen quii trinh hfip phu xiiy ra tdl khi nhiet do
tha'p. Do ion kim loai dugc sonvat hoii tdt vl vay de cho ion kim loiii dugc hfip phu chiing
phiii mfit mot phan Idp vd hydrat hoa ciia chiing. Qua trinh de hydrat hoa niiy ddi hoi nang
lugng. Nang lugng ciui quii Irlnh de hydrat hoii dugc cung cfip bdi su hi'ip phu toil nhiet. Su
loiii bo nudc khoi ion la qua trinh thu nhiet, dudng nhu sir thu nhiet ciui (.|iia trinh de
sonvat vircrt qua nhiet do do su hfip phu phiit ra nen gia tri ui'mg lugng tu do AG'* am, qua
trinh hfip phu lii tudien bien.
4.2. Khii nang hfip phu.
Khii nang hfip phu ciui bentonite phu thugc vao thimli phfm vii ciT'u tnic ciia
benlonite, vao dien tfch vii biin kfnh ciia ion kim loiii.
Ion cd hoii tri thfip de trao doi han cac ion hoii tri ciio. Ion cimg hoii tri, biin kfnh
Ciing nhd thi khii nang trao ddi cang Idn.
Do bentonite lii vat lieu xdp co cfiu tnic Idp, chung eo ciic dien tfch bii trir trong
mang ludi nen co khii nang hfip phu Ciic ion im loiii. Kha nang hfip phu ciia benlonite phu
thugc viio dien tfch am L~>e mfit vii lugng cation bii trir trong miing ludi. Bentonite cd the
hap phu tdt cac ion kim loiii nang, khii nang hfip phu ddi vdi Ciic ion la khac nhau. No phu
thuoc vao dicn tfch va biin kfnh ion. Ion cd hoii tri thiYp de trao doi hon ciic ion hoii tri cao.
Ion ciing hoii tri, ban kfnh cang nhd thi kha nang trao d6i cang Idn.
4.3. Cac yeu td linh hudng den kha nang hiVp phu ciic ion kim ioiii nang.
a. pH
pH ciia dung dich nudc lii mot yeu id quan trgng iinh hudng den su hfip phu ciia
kim loai tren benlonite. Su hfip phu ciia kim loiii giiim khi pH giiim thap bdi vl nhom Al-O
va Si-O dugc nhan nhieu hon mot proton, vl vay chiing luu giu kim loiii kem hon. Tac
dong niiy manh ddi vdi Cu, Pb, Cd vii kem ro ret ddi vai nhung kim loai khac. Nhung neu
pH cao quii no se lam giam be mi)t lich dicn am tren dat set. mii su hfip phu xay ra chii
13
yeu do sir thu hut ion kim loiii ciia Ciic be mill dien tfch am nay nhd lire culong. Khi pH
tiing cao quci (pH > 5) dung lugng tfch dien tfch am tren be mat ciia benlonite giiim di,
dan d€n khii nang hfip phu kem di. Theo kliiio sat pH thfch hgp de hfip plui tdt nhfit la 4.
[51
b. Nhiet do
Vi qua trinh hfip phu la toii nhiet nen khi nhiet do tang thi kh6ng ed lgi cho qua
trinh hfip phu, su hap phu thuan lgi khi nhiet do thfip, nhung cac ion kim loiii trong dung
dich nudc bi bao phii bdi ciic lap sonvat, vl vay de hfip phu lap somiit niiy phiii bi pha va,
qua trinh pha va nay thuan lgi khi nhiet do lang. Nhu vay trong qiui irlnh hfip phu nhiet do
cd anh hirdng trai ngugc nhau, tfing nhiet do thi thuan lgi cho sir phii vd lap sonvat bao
bgc ion, liim de dang hon liim cho sir hfip phu ion, nhung kii khong thuan lgi ve mat nhiet
dong hgc ciui qua trinh hfip phu. Con neu nhiet do mil thfip Ihl qufi trinh hfip phu thuan lgi
ve mat dong hoc nhung neu mil nhiet do thfip qiui thi lap sonvat biio bgc kim loiii kh6ng
bi phii bd nen sir hfip phu khd sfiy ra. Cho nen trong quii trinh hfip phu nhiet do cfin phiii
cd giii tri thfch hgp de cho su hfip phu xiiy ra tdt nhfit
c. Th&i gian
Thdi gian cd imh hirdng miinh den dung lugng hfip phu ciui bentonite. vdi n6ng do
vii the tfch eiia ion kim loiii, khdi lugng ciui bentonite xiic dinh den khoiing iha'i gian niio
dd dung lugng ciia benlonite kh6ng thay doi. Khi dd ta co hfip dung cue diii, thdi gian dd
goi lii thai gian bang hfip phu dugc ihiel lap, no phu thuoc viio cac ye'u td nhu nhiet do,
pH, ndng do chfit dien ly, khdi lugng chfit hfip phu ,the tfch dung dich hfip phu.
d. Kich thudc hat bentonitCj dieu kien khiiciy tron
Sir hfip phu tang vdi sir tang dien tfch be niilt, tire la dicn tich tiep xiic gifui ion kim
loiii va chfit hfip phu. VI v(iy de cho sir hfip phu diit ket quii tdt kfch thudc hiit phiii that
nho, min. Mat khiic ta biet rang bentonite la khoang set no co dac diem la dco vii dfnh nen
trong dung dich no thuong biim ket vdi nhau, liim giiim khii nang hfip phu, vl vfty phiii tien
hiinh lac de chiing phan tiin liim cho su tiep xiic giua ion vii bentonite tdt han.
e. Ty le bentoniteldung dich (R/L)
Ty le khdi lugng ciui chfit hfip phu vii the tfch ciui dung dich hap phu imh hudng
den khii nang hfip phu ciui ion kim loiii tren bentinit vdi m6i kim loiii co mot ty le xac
dinh lii tdi uu, phu lhuoc viio ndng do ciia ion kim loiii, bim chfit cua chfil hfip phu, nhiet
do, nong do ciic chfit dien ly vii thai gian hi'ip phu.
/ . Anh hudng ciia cdc chid dien li trong moi trudng nude
14
Anh hudng chfit dien ly ddi vai su hfip phu ciia bentonite vdi cac ion khiic nhau la
khac nhau. Nhung, ndi chung ndng do ciic cha't dien ly trong dung dich tang khii nang hfip
phu bi giam di. Do su tiio phirc ciia cac chfit dien ly vdi citc ion kim loiii, sir thuy phan,
anh hudng den su khuech tan ctja cac ion kim loai.
Trong ban Bao cao ke't qua nghien ciru niiy chung tdi dua rii ciic ket qiui khiio siit
mgl sd ngi dung sau:
- Ddi tugng khiio sat lii mau quang bentonite dugc Trung tam Cong nghe xir ly
quang, Vien cong nghe Xa - Hiem, Vien Nang lugng Nguyen tir Viet Niim Ifiy tir md
bentonite kiem tho Di Linh - Lam D6ng vii mo bentonite kiem Tuy Phong - Binh Thuan.
Quiing d dang cue, cd do fim 10 ^ 15%.
- Quang dugc phoi kh6, dap, nghien nhd, loi hoii viio nudc, khufiy lien tuc trong
hai gid, de yen r6i lang giin hty huyen phii ben tren, loiii bo ciil, soi, ti.ip chfit ca hgc d
dudi. Huyen phii thu dugc dugc lgc, sau do phoi khd, nghien nhd, sfiy kh6. Cd hiit quang
sau khi nghien cd kfch thudc lii < 150 pm.
- Hoiil hoii bentonite bi"ing dung dich H2SO4 co nong do xiic dinh, d Ciic dieu kien
T, thdi giiin, kluuT'y tron, ty le R/L thfch hop.
- Khiio sal cac yen td imh hirdng den den khii nang hi'ip phu cac ion kim loiii nilng
Fe", Mir"^ ciia benlonite da dugc hoiit hoii.
Trong quii tinh ticn hanh thf nghiem, chiing toi da sir Ciic loiii thiet bi siiu day. Cac
thie'l bi nay mgl sd d Khoa Hoa hgc - Tnrdng DHKHTN vii mot sd d Vien Xii Hiem Vien Nang lugng nguyen tir Viet Nam. Miiy do pH vii the oxy hoii - khir microprocessor
pH meter cua Diic. Kfnh hien vi dicn tir SANYO ciia Nhat. May dap nghien sang phan
cfip hat ciui Nguyen lir nang qudc te. Miiy do ph6 hfi'p lhu electron spectrophotometler
Hitiichi U200I
Cac hoa chat su dung la: axit sunphuric H2SO4 loiii PA; Tinh the mangan (II)
clorua MnCl2-4H20 loiii PA; Tinh the mudi sfil (11) sun Lit ngam nudc: FeS04.7 H^O loai
PA; Axit clohydric HCl loai
PA; Tinh the biic nitrat AgNO^ loai PA; Tinh the kali
persunphat K2S20^s 10\>i P^^ ^^'^ sufoxalixilic loiii thudc thir; H2O2.
Mau quang siV dung de nghien ci'ru: Quang bentonite duoc Trung tiim c6ng nghe
sir ly qiuTng, Vien c6ng nghe Xii - Hiem, Vien Nang lugng Nguyen tu Vet Nam Ifiy lir md
bentonite Di Linh - Lam Dong ve d diing cue co do am 10 ^ 159i.
Quang dugc phoT kho, dap, nghien nho, roi hoii vao nudc, khufiy lien tuc trong hai
"id, de yen rdi lang gan la\' huyen phii ben tren, loiii bd ciil, soi, tiip chfit co' hoc.
15
Huyen phii thu dugc dugc lgc qua tfmi vai min, siiu do phoi kh6. cho viio may
nghien bi sir de nghien trong khoang Ih. Bgt nghien lay ra dem viio sfiy, cd hat quang sau
khi nghien cd kich thudc la < 150 pm.
Thanh phfin khoang ciia miUi quang dugc xac dinh bfing phuong phap nhieu xa
Ranghen. Thanh phan hoa hgc ciia mau quang dugc xiic dinh bfmg cac phuang phap phan
tfch hoii hgc nhu da trinh biiy trong ciic muc 2.2.
Mau bentonite siiu khi dugc lam giiiu va lam siich dugc diinh gia chfit lugng qua
khii nang hfip phu Ciic ion kim loiii nang tir moi tnrdng nudc. Ciic ion kim loiii nang dugc
s u d u n g de lam ddi tugng khiio siit lii ciic ion kim loiii chuyen tie'p dily I vii L'02"''.
II . PHUONG PHAP NGHIEN CUU
2.1 Phuong pluip hoat hoii quang
De khiio sat khii nang hoiit hoii, ciic dung dich iixit sunphuric co ndng do thay ddi:
20%, 15%, 10%. Khi nong do hUSO^ < 10%, theo Ciic tiic giii ciui ciic c6ng trinh | 1 ^ 5 | ,
khii nang hoiil hoa la khong diing ke. Khi nong do iixit simLiiic > 20%, clo tac dong ciia
axit qiui niiinh de xay ni hien lirgng phii huy cfiu triic ciui bentonite (hien tugng sap
khung).
Thdi gian hoiit hoii tir 1-^6 gid; Nhiet do 9 0 - H 9 5 ° C ; Ty lc bentonite / iixit ve khdi
lugng lii 1:3. Qiui trinh hoiit hoii dirge ticn himh tren thiet hi hoiil hoii ciui Trung tam Xir If
quang, Vien Xii Hiem, biio gom ciic bo phfin siiu: Bg phau dun ciich thuy eo dieu nhiet;
thiet bi khufiy vdi canh khufiy thuy linh; nhiet ke; binh phim I'rng bang cdc thuy tinh 1,5lfl.
Qua trinh hoiit hoii bentonite dugc tien hanh nhu sau: Lfi)' 200g quang bentonite
cho Viio binh thuy tinh co dung tfch lii 1500ml, them viio do 200ml nudc cfit. Binh phan
irng dugc cho viio thiet bi dieu nhict. Hon hgp bentonite vii nudc dugc khufiy bang miiy
khiuT'y CO ciinh liim bilng thuy linh. Dun nong dung dich den nhiet do 90'^C, cho tir tir dung
dich axit viio binh giu ngii\cn nhiet do ciui he, chii y ty le gifui plui long \'a phii ran lu6n
g i u d 1:3.
Khi da dii thdi gian hoat hoii, Ifiy ciinh khufiy ra, do ngay hon hgp trong cdc viio
phlu lgc hut chiTn khong, rira phcu bang nirdc cfit de'n khi het SOj"" (thir bfmg Ba'"") va pH
nu'Oe Siiu khi nVii biing 4-5. Sau do siT'y kho, nghien nho siing qua cd simg 150 pm.
2.2. Phuong phap phan tich thimh phiin hoa hgc ciia bentonite.
Nhilm muc dfch xem xet sir thiiy doi thiinh phfin ciic cau tir ciui benlonite khi hoiit
hoii vii liic chu'a hoiit hoa vit irong ciic dii^u kien khiic nhau, chiing toi tien himh xiic dinh
thimh phi'in ciui mgl sd cfiu tu chinh nlur Si02, AUO;, Fc20t, CiiO, MgO.
a. Xdc dinh hdm 3102.' Ham lugng Si02 dugc xac dinh bang phuong phiip khdi
lugng. Qua trinh pha tfch dugc tien hiinh nhu sau: nung mot phan bentonite vdi nam phfin
hdn hgp chay (4 K2CO3 + 5 Na2C03) trong chen sir platin d 900"C khoang 30 phiit, Ifiy ra
de nguoi, sau dd dung HCl dac ket tiia Si04'" ve diuig Si02.H20. C6 dac dung dich lam
dong tu keo. Lgc rira ket tiia bang HCl loang va nudc cat trong dieu kien nong, nung ket
tiia trong Id nung d 850"C trong Ih, de nguoi can nhanh ket tiia.
b. Xdc dinh hdm Fe20j
Dc Xiic dinh ham Fe20i chiing tdi da dimg phuang phiip the ti'ch: dimg H2O1 oxi
hoii sat (II) len sat (III), dun soi de loai H2O2 du, them axit sufoxiilixilic, dieu chinh pH
den 1,5 hoac 2, dung dich cd mau do xfim ciia phi'rc sfit sunfoslixilic. Fe"^"^ -\- Sul = FeSul-"".
Chuan do vdi complexon 111 cho den khi mfit miiu dd sam vii xufit hien mini vang nhiit, vl
EDTA tiio vdi Fe"''^ phirc ben hon la axit sunfosalixilic.
c. Xric dinh hdm lugng AI2OJ
Diing phirong phiip the tfch chuan do ngugc bang EDTA.
Al^^ tao phi'rc vdi EDTA tiii pH -7 hoac 8 con Fe"*"^ tiio phuc vdi EDTA trong
khoang pH tir 1-9 . VI vay chiing toi tieTi hanh chuan do d pH = 7 .
Ciich lieTi himh: Lfiy dung dich sau khi da chufin do Fe^"*", cho du EDTA co nong do
Xiic dinh, dieu ehinh ve pH = 7, dun ndng den 70"C, liic ky cho Al"'"^ tao plu'rc het. Sau dd
chuan do lugng EDl'A dir vai chi ihi xylen cki ciim bang dung ilich Zu(CH,C00j> . Tir the
tfch EDTA lieu tdn cho du chi'nh xiic la co the tfnh dugc nong do Al"*' tong dung dich va
tirdd tfnh dugc hiim lugng ALO^
d. Xdc dinh MgO vd CaO
Dimg nuac loc rira trong tjiiii trinh xiic dinh Si02 tiich Fe Na Al ra khoi bang dung
dich NH4OH. Dung dich phim ung dugc dun soi den 70^'C, lgc rira ket tiia bang dung dich
NH4N0, loang. Lfiy dung dich nudc lgc de xac dinh Ca""", Mg'".
VI Ca-"" tiio phi'rc vdi EDTA d pH lir 2- 11 cdn Mg'" Uio phirc d pH == 10 nen trirdc
het ta chufin rieng Ca'" d pH = 2 chi thi nuircxit dd.
Cung lfiy mot lugng bang V2 tir Vi dem chui'in tdng Mg~" vii Cir" biing EDTA vdi
chi thi ETOO trong m6i truong dem NH4OH + NH4CI. Trudc het diing dung dich NaOH
20% dieu chinh pH ve 10 roi dimg dem ehinh ve 10,6.
2.3. Phuong phdp xdc dinh sdt, mangan trong dung dich
Dimg phuong phap trfic qiumg de Xiic dinh vl phuang phiip niiy cho kei qiui [uang
ddi chinh xac va nhanh chong.
OAI H'JC
QU'.'-^C GiA HA NOi
TRUNG TAr/ THONG TIN THU VIEN
PT I yU9
a . Phuong phdp trdc quang xdc dinh ndng do ion sdt trong dung dich voi thudc
thu thioxianat. Do ion Fe"^" de tiio vdi ion SCN theo phiin ung
Fe-'" +
6 SCN' - Fe(SCN)--,
Phirc tao thanh cd mi\u dd mau cd cue diii hfip thu d budc song X = 500 nm, do hfip
thu quang ty le vdi ndng do ion Fe "; Cd mfit amoni tioxianat 20%,
b .Xdc dinh mangan bdng phuong phdp triic quang
Dua viio phiin irng oxy hoit Mir" thimh Mn04" iheo phim irng sau:
2 Mn-" + 5/2 S2O,- + 8 H.O = 2 Mn04 + 5S04-- -H 16 H"
Phim irng xiiy ra trong m6i trudng axit H2SO4, HNO3 vdi sU xiic tac ciui Ag". Ion
Mn04' dugc Uio thanh trong dung dich co mau dam, co the do ABS de xiic dinh ndng do
cua nd duii viio dudng chufin d budc sdng X - 523nm.
2.4. Phuong phiip xac dinh hfip dung ciia cac ion kim lo;ii tren bentonite
Dung dich ciui ciic ion kim loai co n6ng do khiic nhau dugc chufin bi bi'mg each
hoii tan mudi d diing linh the viio uirdc cfit r6i axit hoii bang axit sunfuric de'n pH = 4.
Bentonile dugc can vdi khoimg 2g cho vao ciic binh non chi'ra 50 ml dung dich. Sau khi
can nuUi cfin xac dinh do fim ciui mfui de tinh chfnh Xiic lugng benlonite cho viio. Ciic
binh dugc day kfn cho \ao nuiy klc vdi tdc do 140 \ong/phut trong thc^i gian 3h. Siiu do
lfiy ra lgc tren pheu thuy tinh \'di giiiy loc bfmg Xiinh .Ciic dung ciich dfiu \'ii ciic dich loc
tuong irng dugc deni plu'm u'ch trac c|Uiing theo phuong phiip neu lien. Thf nghiem ticn
himh d nhiet do phdng.
Lugng ion kim loiii dugc hfip phu bdi bentonite, dugc xiic dinh tir sir chenh lech
nong do trudc va sau hfip plui. Dung lugng hfip phu dirge tinh theo cong thirc siiii
a=||Co-CLV|/m
Trong dd: a lii dung lugng hfip phu ciia bentonite; CQ la n6ng do ciia ion kim loai
trong dung dich dfiu; C la n6ng do ciia ion kim loiii khi can bfmg dugc thiet lap; m la khdi
iirgim benlonite dimg de hfip phu; V Iii the tfch dung dich kim loiii .
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