- Thong ke va xir ly so lieu thuc nghiem bang eac phan mem Exell va Matlab.
390 W{VI)-TOAB
1. Cot trao doi ion chua cationit axit manh hoac
390 W{VI)-TOAB
W{VI)-TOAB MoÔTOAB 440 490 ^ 0 Wavelength (nm) 5 9 0 0 w
Ihnh 3.5. Pho cua Mo(\'l) va Úd'l) vói TOAB tron^nwi tnrcrni^ nuoc -axeion
\loÔ TỌAB
20 DL 0'- f-i
Nong do axeton i=/c)
f/inh .v6. , Inh lunnn.: ciui nom: Jo axcion ilcn Alls cua f>hirc Úl > \!<HI h-'IOAB
Rieng axeton the hien nhir mot imoiig hop dac bici Khi nong do axeton tronii nirac tang tir 0% tra len thi do hap thu quariL! cua phirc \\oi\'\)
vdi TOAB tang nhanh va dat gia tri cue dai d ndng do axeton xung quanh 30%; sau đ giam khi ndng do axeton Idn hem 30% va giam tir tir khi ndng do tren 60%). So sanh anh hudng ciia axeton doi vdi do hip thu quang ciia phirc Mo(VI) va W(VI) vdi TOAB, cd thi nhan thiy day la tac nhan tao ra su khac biet Idn nhit va khi ndng do axeton trong khoang 30% thi su khac biet nay la cue dai (hinh 3.6). Dieu nay cd nghTa la ben canh kha nang lam tang do chgn loc cua phan irng mau ciia Mo(VI) vdi TOAB, cd le trong dilu kicn nhu vay axeton da trd thanh mot tac nhan tao ra su polime hda manh ion W(VI) trong dung djch de chuyen thanh dang ehii ylu la cac anion poliaxit. Phd hip thu cua dung dich W(V1) vdi TOAB cho thiy trong dilu kien nay phirc chelat WO2-TOAB khdng dugc hinh thanh (hinh 3.5 va 3.6). Trong dung mdi nude chira khoang 30% axeton (V/V), Mo van o dang cation MoO:" nen tao phirc chelat tdt vdi TOAB va do hap thu quang Idn hon nhieu dung dich nude - axeton 30% (V/V) cua W(VI) vdi TOAB.
Tir cac ket qua nghien ciru nay chiing tdi chgn axeton lam dung mdi tao mdi trudng hdn hgp nude - dung mdi hiru co de nghien ciru sir tao chelat cua Mo (VI) va W(VI) vdi eac thudc thu tao ngi phirc.
3.1.3. Nghien cuu kha nang tao noi phuc ciia Mo(\ I) va \V(\ I) voi TOAB trong moi trudng nude - axeton
Dung dieh Mo(VI) va W(VI) vdi TỌ^B dugc chuan bi nhu trong muc 2.3.2.1. Kit qua do phd hip thu quang cua phirc sau khi duoc chiet \ao toluen the hien tren hinh 3.7.
Nhin vao phd cua phirc TOAB vdi Mo(Vl) \a W (\ 11 tren hinh 3.7. chiing ta cd the thiy trong mdi tnrcmg nude - axeton L^^0"o) co pll 3. dang phd ciia phirc chelat Mo(Vl) - TOAB hau nhu khong iha\ doi ^o \oi phd cua no trong mdi trudng nude cd cimg gia tr; pH. Nhung phd cua phirc W ( \ l ) \ 01
TOAB thi hoan toan khdng xuit hien. Phd cua dung djch W(VI) vdi TOAB gan nhu triing kbit vdi phd cua thudc thir TOAB va ehi thip hon chut it. Dilu nay chirng to rang trong dieu kien nghien cim, phirc cua W(VI) vdi TOAB hau nhu khdng dugc tao thanh. Cd thi cd mot phin rit nhd ciia W(V1) tdn tai dudi dang cation do can bang chuyin dieh cac dang tdn tai eiia W(V1) sinh ra da tao ngi phirc vdi TOAB, cho nen trong tit ca cac lin khao sat, phd cua dung djch W(V1) - TOAB ludn ludn thip hon phd cua thude thu chut it.
T O A B
\ l o O - . I O \ B
Hinh 3. 7. Phd hdp thu quang cua phirc MoO: - TỌAB. thude fhu TOAB vd dung dich W(VI) vdi TỌAB trong nudc-axeton 30% cd pH 3
sau khi duoc chief vdo toluen
Trong mdi tnrdng nude - axeton, do hap thu quang eua dung dich W(VI) vdi TOAB va phirc MoO-TOAB da cd sir khac biet rat Idn (hinh 3.5. 3.6). Nhung khi ehilt len dung mdi hCru co nhu toluen ha> clorofooc. benzen thi su khac bict nay cang rd hon nhilu (nhu tren hinh 3.5 va hinh 3.7). Mo(Vl) tao phirc rit tdt vcVi TOAB trong khoang ndng đ axeton tu 25-35%: trong khi đ W(VI) tao phirc vdi TOAB kem diin khi timg ham lugng axeton va tir 25% axeton tro len thi su tao phuc giira W \ a TOAR la khdng dang kc.
Sir cd mat ciia axeton trong nude da lam chuyin djch cue dai hip thu ciia thudc thu ve phia budc sdng dai hon ( 390 nm vl 430 nm, hinh 3.1 va hinh 3.7).
Khao sat anh hudng ciia ndng do axeton din do hip thu quang eua phirc Mo(VI) va W(VI) vdi TOAB sau khi duoc ehilt vao toluen. chime tdi tiln hanh nhu trong muc 2.3.2.1. va thu dugc kit qua nhu tren hinh 3.8.
50 60 %Aceton %Aceton
Hinh 3.8. Anh hudng ciia ndng do axeton den do hdp fhu quang cua phirc MoO: - TOAB vd W(V1) - TOAB sau chief len loliien
Tir nhung kit qua nghien ciru thu dugc o tren cho tha\ trong mdi tnrong pH bing 3 va ty le ndng do nude - ạxeton la 70% va 30% theo the tich. W (\1) gin nhu chu ylu tdn tai dudi cac dang anion poliaxit. Trong ciing dieu kicn thi dang tdn tai can bing eua Mo( VI) la MoO:" khdng he hi tac dgng \a phuc chelat M0O2-TOAB hoan toan dugc ehilt vao dung mdi it phan cue nhu toluen, benzen hay clorofooc - la cac dung mdi khdng dura o \ \ . Irong khi trong mdi truimg nude, phirc chelat MoO:-rOAB chict tot Nao cac dung mdi huu CO CO oxy nhu butvlaxetat. etx laxetat. isoam> I aneol ancc^i hutylic...
nhung khong dugc ehilt bing cac dung mdi khdng chua oxy [4, 159]. Dilu nay cd the giai thich la do khi phuc chelat M0O2-TOAB dugc hinh thanh trong mdi trudng nude - axeton, cac phan tir axeton da thay thi mot phin Idp vd hydrat ciia phirc nay (trong hinh 2.1) tao nen Idp vd solvat bdi cac phan ni axeton va nhd the ma da ehilt dugc de dang vao dung mdi hu-u eo khdng chira oxy; cdn trong mdi trudng chi cd nude, nang lugng hydrat hda da tro thanh hire tudng can khdng the ehilt dugc vao dung mdi khdng chira oxỵ
Nhu vay trong dieu kien nhu trinh bay d tren, cd thi phan tich true tilp dugc Mo ben canh W va cung cd the tach duge Mo ra khoi W bing phuong phap chiet dung mdị Trong thuc te phan tich Mo bang phuong phap naỵ de tang do chgn lgc va do nhay eiia phep phan tich, phirc Mo-TOAB da dugc chiet vao dung mdi hiiu eọ Trong pha hiru eọ do hap thu quang tang len dang ke nhung dang phd va cue dai hap thu hau nhu khdng tha\ đị Trong khi đ W hoan toan khdng duge chiet. Day la mot diem thuan Igi cho vice xac dinh rieng re Mo va W bang phuong phap chiet - trac quang.