- Thong ke va xir ly so lieu thuc nghiem bang eac phan mem Exell va Matlab.
1. Cot trao doi ion chua cationit axit manh hoac
2.3.5. Ky thuat trao dii ion true tiep trong moi truimg nuoc-dung moi huu CÓ
moi huu CÓ
Cot ionit su dung cho eac nghien ciru dugc chuan hi san sang nhu tren muc 2.3.4.1. Sau khi da dugc trang biing hon hop nuoc - axeton 30"o co cung
Dpi 10 ml dung djch Mo(VI) hoac W(VI) dugc chuin bj theo cac yeu cau cua moi nghien ciiu qua cot cationit hoac anionit nrong img vdi tic do pha dgng la 1,0 ml.cmVphut. Khi dung djch chay vira din sat mat nhua thi diing dung djch nude - axeton co ciing dilu kien tir binh chira doi tilp qua cot
dk dly toan bg dung djch luu cua kim loai khong bj hip phu ra khoi cot
(thong thudng thi tich nude - axeton cin diing bang ba thi tich cot nhua). Tit
ca dung djch di ra khoi cot dugc gom lai dk phan tich lugng Mo va W khong
dugc hap thu tren cot. Dung dung djch HCI 2,0 M hoac NaOH 2.0 M de rua giai Mo hoac W bj giir tren nhua ra khoi cot. Moi phan doan bang mot the tich cot nhua (5 ml) dugc thu lai, xir ly va phan tich lugng Mo va W co trong đ bang chiet - trac quang va bang ICP-MS.
CHirONG 3. KET QUA VA THAO L U A N
3.1. NGHIEN c u t ) KHA NANG TAO NQI PHUC (CHELAT) CUA Mo(VI) VA W(VI) TRONG MOI TRUONG NU^OC VA NUOC-DUNG MOI HUU CO 3.1.1. Phuc chelat ciia Mo(VI) va W(VI) trong moi trudng nude
Khao sat pho hdp phu quang cua phuc chelat
Tu nhung ket qua da cdng bo cua nhieu tac gia deu cho thaỵ trong moi trudng axit yeu, ca Mo(VI) va W(VI) d6u co the t6n tai o dang MỐ hay cac dang hydrat cua no - M02(OH)2.2H20 va ca d dang cac anion da nhan kim loaị Chinh vi vay ma khi co mat mot tac nhan tao ngi phuc nao do no sc phan ung vdi dang cation MO:^ va keo can bang phan ung vc phia tao thanh cation M02^'. Phuc cang ben thi phan tram kim loai tham gia tao phuc cang Idn. Trong phan nghien cuu nay, chung toi chon TOAB. mot thuoc thu tao noi
\ t I ' '
phuc truyen thdng doi vdi nhom nguyen to nay de khao sat.
Dung dich phuc mau dugc chuan bi va tien hanh do pho hap thu quang nhu trong muc 2.3.1.1. Ket qua thu dugc trong \ung bucrc song tir 300 den 700 nm dugc the hien tren hinh 3.1.
Qua kCn qua khao sat Urong tac cua Mo(\'I) \a \ \ ( \ ' I ) \oi TOAB trong mdi trudna nude, chunu toi nhan tha\ nhu tren hinh 3.1.. thuoc ihu TOAB co pho hip thu cue dai o 390 nm; phirc Mo(\'l)-TỌ'\B co cue dai hap thu a 490 nm va phirc W(VI)-TOAB co cue dai hap thu o 475 nm lu buoc song 375- 575 nm phan Idn pho hip thu eua phuc \V(VI)-TC)AB \a Mo(\ 11-TOAB trum lln len nhaụ Phirc cua W'(VI) \di TOAB co he so hap thu phan tir gam Ion han phirc eua Mo( VI) vdi TOAB trong cung dicu kicn.
0 8 ^ 0 7 ^ 0 7 0.6 0 5 0 4 0 3 0 2 0.1 0 3; y ^ " X ^ TO A a '5 425 475 \ WO: TOAB V \ MoO: TOAB 525 575 - - 625 675 (nm)
Hinh 3.1. Phd hdp thu quang cua phirc Mo(VI) vd W(VI) v&i TOAB trong mdi trudng nu&c (Crotn =1-10' M: CuoH n = Cut,,, ^ 2.10' M: pi I 3)
Qua ket qua tren, chiing ta eo the khang dinh rang trong dung dich nude CO mdi trudng axit yeu, ca Mo(VI) va W(VI) deu tao noi phirc \di lỌAB. Dieu do cung cd nghia la chiing deu eo dang ton tai la cation MOj" trong dung dieh. Dong thdi do pho eiia phirc eiia chiing chong Ian nhau phan Idn. nen khong the phan tich true tiep timg nguyen to rieng re dugc. Dieu na\ cung duge khang dinh trong nhieu cong trinh da cong bọ
Trong phan tu ciia TOAB cac nhan thtmi lien ket \di nhau qua nhom azo (-N = N-). Do eo hai nhom OH o vi tri octo \a octo" so \oi nhom mang mau azo nen thudc thu TOAB co kha nang tuong tac vdi eac ion kim loaị Khi ion kim loai tao phirc vdi TỌ'XB o \i tri ma phirc hinh thanh co \ong 5 hoac vong 6 canh thi phirc se bcMi hon. Nhom OH dong \ ai tro phoi tn o \ i tri octo so vdi nhdm azo nen se tao dugc lien ket cho giira kim loai \a nhom azo [150]. Nhu vay, hai nhdm OH o vi tri octo va octo" \ ua dong \ai tro chat trg
mau vira đng vai Xrb lam tac nhan nhudng dicn tú trong lien ket \ oi ion kim
loaị Vi the TOAB cung eo kha nang tao phuc voi rat iiliicu cac kini loai nhu
va cau
mot so ion kim loai [159]. Da cd nhi^u cong trinh chung minh co ch^ va tao ciia phuc hinh thanh giua ion kim loai vdi TOAB [4, 11, 159], Phan ung
giua cation M02^^ vdi TOAB co th^ minh hoa nhu tren hinh 3.2.
.OH HO MO MO 0 / 0 fOH,) / V«=M. \ / •OH + M()^'' ^ / \ • N — N I H :0 + 2H
Hinh 3.2. Phdn UTig cua Mo vd Wvdi TOAB
Trong cac phan ung tao phuc, ion kim loai thay the cac ion H* trong cac phan tu phoi tu dan den lam thay doi nong do [11] cua dung dich khi phuc dugc hinh thanh. Vi vay, qua trinh nghien cuu co che phan ung maụ
can phai nghien cuu anh hudng cua pH den can bang tao phuc. den thanh
phan va do ben cua phuc. Nghien cuu sir tao phuc mau cua Moi VI) va W(V1) vdi TOAB trong moi tnrdng nude, chung toi da tien hanh khao sat anh huong ciia pH.
Khao sdt anh hudng cua pH len do hdp thu quang cua phuc
Khao sat anh huong cua pH dugc tien hanh nhu trong muc 2.3.1.2. Ket qua do do hSp thu quang d cac budc song cue dai cua phuc chelat Mo(\T)- TOAB (490 nm) va W(Vl)-TOAB (475 nm) thu dugc bieu dien tren bang 3.1. va hinh 3.3.
Tu ket qua nghien cuu cho thc4y pH anh huong manh den kha nang tao phuc cua molypden va vonfram. Doi \ai Mot\'l). kha nang tao phuc co the xay ra o mdi trudng co pM thap hon so voi W(\'l). Nhung nhin chung ca hai
ion d6u tao phuc t5t nhk a pll xung quanh bạ Dicu na> clurug to rang, ngoai
xung quanh 3 ty le ciia dang cation MoOj^" cd thi la cao nhit va dang cation WO2 CO the la cao nhat d pH Idn han mot chut (pH 3 din 4).
Bdng 3.1. Suphu thuoc cua do hdp thu quang vdo pH dung dieh
A B S ^ ^ ^ ^ pH dung djch phiic^^ Mo(VI)-TOAB W(Vl)-TOAB 1 0,210 0,287 2 0,213 0,301 3 0,217 0,314 4 0,201 0.311 5 0.162 0.296 6 0,159 0,257
Hinh 3.3. Anh hmwg cua pH den do hdp fhu quang eua phirc
Trong nhii-ng nghien ciru tiep theo chung toi se su dung gia tri pH 3 nhu
la pH t6i uu cho qua trinh tao phirc eua ca hai ngu\en id.