TAP CHI KHOA HQC & CONG NGHE CAC TRI ONG DAI HOC KY I HUAT • SO 92 - 2013
CfflET PHA RAN, PHAN TICH Cr(ni) VA Cr(Vl) TRONG MAU NUOC CAP VA NU'6C THAI BANG PHUONG PHAP F-AAS
SOLID PHASE EXTRACTION. ANALYSIS OF Cr(lll) AND Cr(VI) IN WATER SUPPLY AND WASTE WATER SAMPLES BY F-AAS
Nguyin Thi Ngoc Anh Nguyin Xuan Tru&ng, Trdn Thi Thuy Phdn lich Mdi trumig bien Hdi Qudn Tru&ng Dgi hoc Bdch khoa Hd Ndi
D^n Tda soan 17-10-2012. chSp nhan dang 20-12-2012
Crom tin tai trang nud^ d him lw(?ng vit chu yiu dw6i dang Cr(lll) vi Cr(VI), trong do Cr(VI) idc va kho xir ly Bi nghien ciru muc dp tich luy va nguy co tie dong cua crom trong nwac cip vi iirdc thai din sue khde con ngw&i. qui tnnh chiit pha rin da dwac nghien ewu thwc hien tren nhwa XAD-7 di tich va lim giiu cie dang tdn tat cua crom Cac yeu td inh hwang din hieu suit thu hdi
<]hwpH, luung phdt tu: Iwang vit liiu hip phu. tdc do nap mau qua cdt. thi tich vi Iwang dung moi Tia giat, thi tieh miu. vi cic ton la da dwac nghien ciru chi tiit Cic diiu kien tdi wu hda cung da luvc dwa ra Qui tnnh phin tieh dinh Iwang crom duac thwc hien bing phuang phap phi hip thu iguyen tw ngon /t/a,
Tir khoa crom, hap phu, XAD-7, F- AAS
ABSTRACT
The existance of chrommium in water at trace levels is mainly in the forms of Cr(lll) and Cr(VI).
V which Cr(VI) is toxic and difficult to do the treatment To study the cumulative impact and risk of :hromium in water and waste v^tater to human health, the solid phase extraction process has been studied on XAD-7 resin to separate and enrich the existing forms of chromium. Factors affecting the yield such as pH, ligand amount, the amount of adsorbent sample loading rate through the column, solvent volume and elution volume, sample volume, and the strange ions have been investigated Optimum conditions have also been addressed The process of chromium quantitative analysis is ione by means of flame atomic absorption spectroscopy
1. GIOI THIEU CHUNG qua cao va vin cd kha nang gay ung thu [3]. Do
^ . , , ; ^ ,,,,. ,. - , ~ dd, viec phat trien dd nhay ciia phuong phap.
Cac hop chat Cr(lll) la mot trong nhung , i ^ L- ' • j - i • j ., , : ! ", ; '^ . r cuna nhu phuonc phap xac dmh cac dang CFom itvi lugng thiet yeu trong ca the con ngudi
a ddng mdt vai trd quan trong nhat dinh trong trong mau mdi trudng la \d ciing can thiet.
iir chuyen hda glucose va mdt sd chat beo. Ham lugng ciia cac dang crom trong mau rong khi cac hgp chdt ctia Cr(VI) lai la cac nudc ty nhien ndi chung cd gia trj ca yg/l va tin :hal doc va la tac nhan gay ung thu. Do dd can hieu nen ciia mau la Idn. Do dd, ngoai trir cac ky ihai kiem soat dugc muc dd xudt hien ciia thuat phan tich hien dai cd do nhay cao nhung :roiTi trong nudc thai, nudc tu nhien va nirdc ddi hdi chi phi Idn nhu ICP-MS, GF-AAS... thi long khong phai chi d dang tong ciia nd ma viec xac dinh true tiep cac dang crom la rat khd
;an CO nhu'ng quy djnh rieng doi vdi tii'iig khan va thudng ddi hdi mau phai dugc lang cho phii hgp. tach/lam giau trudc khi phan tich. Da cd nhieu T , . , i , i , , . . V, phuong phap tach/lam giau mau khac nhau Irong he thong quy chuan Viet Nam , • , u . u • /- /\M\
J. f ,",. , , , . . ;• , . duoc ap dung nhu tao phue Cr(VI) vai ammonium pyrrolidiiiedithiocarbamate la quy djnh gidi han cho phep ciia tdng ham
iicmg crom trong nuac uong la 0,05 mt;/l ,,r.r-,r^\ • .i, u-- i--.?- n - J u.Zi- ,. , , .. . ° , ., . . . (APDC) va thuc hien chiet long-long su dung ijj doi VOI nuoc thai cong nghiep quy dmh , .. ' , • r ^ , , . ,l,.Tr.,r^•r7^
.: „••• , , , . , . , ,^ /,,,.: ,. dunii moi metyl isobutyl ketone (M BK) 141 ogioi han cho phep ham luang Cr(V!) la . =^ u - • i,- i • -. i - i.- \.
in<;™ /T • t-- 1 ,- /lii-, I- n\ /I chiet pha ran vai nhieu loai vat lieu hap phu '.U5 mg/1 va ham lucmg Cr(lll) la 0,2 mg/1 ,, . , ^ , ; , , r, • • •' • •' 2] Tuy nhien, Td chirc Y te the gidi (WHO)
iho i5ng gia tri ham lugng Cr(VI) la 0.05mg/I la
khac nhau. Chang han nhu Pei Liang va cac cdng sy [5] da su dung cgt nhdi cd chira TiO:
TAP CHi KHOA HQC & CONG NGH$ CAC TRlT^WG DAI HQC KV T H U ^ T • s6 9 2 - 2 0 1 3 de tach rieng Cr(III) va Cr(VI) rdi xac dinh
Iirng dang bang phep do ICP-AliS, Nhdm tac gia khac [6] da nghien ciiu kha nang sir dung chitosan bien tinh de tach ioai Cr(lll) va Cr(VI) khdi ngudn nudc thai va sir dyng dung djch IICI 3M rua giai de lai sir dyng vat lieu hap phu.
Trong bai bao nay, cluing tdi sir dung . APDC dc tao phiic chgn lgc vdi Cr(Vl) d dieu kicn pH ihich hgp, sau dd dang phiic Cr-APDC sc duoc cho qua cgt chira Ambcrlitc XAD-7.
Nhua XAD-7 la polymctaacrylal, cd kha nang hap phu cao dugc ung dgng dc lach va lam giau cac kim loai ngng trong mau nudc vii mau mdi Irudng, Sau khi chiet tach va Iam giau, cac dang Idn Iai ciia crom dugc xac dinh bang phuong phap quang pho bap phu nguyen tu che dg nggn lira. Ham Iugng crom long sd dugc xac dinh luang tu sau khi oxi hda Cr(lll) thimh Cr(Vl), Ndng dd Cr(lII) thu dugc dya tren sy khac biet ciia hai gia tri nay.
2. N O I D U N G NGHIEN CUtJ 2.1. Hda chat, thiet hi
Thiet bi quang phd hap thu nguyen tu ciia Perkin Elmer AA-300 dugc trang bj den catot rong dan nguyen Id va hdn hgp khi chay khdng khi/axetylen dugc sir dung trong phuang phap xac dinh crom. Budc sdng lya chon ia 357,9 nm pH dugc do tren may do pH Presica 900. Su dung cdt chiet pha ran va nhua XAD-7 de tach va lam giau mau kim loai.
Tat ca cac dung dich dugc chuan bj tir cac hda chat tinh khiet phan lich cua Merck, Fluca va Prolabo. Sii' dung nudc cat dat chat lugng 18,2 MQ, TOC < 10 pg/ml.
Dung dich chuan Cr(VI) dugc chuan bi til K^CriOi cd ndng do 1000 mg/L. Cac dung dichmau gia va dung djch chuan dugc chuin bj bang each pha loang dung djch goc theo ty Ie tuang irng H^SO, va NaOH dugc dimg d^
dieu chinh pH cua dung dich. Nhya Ambcrliie XAD-7 (kich co hat la 20-60 mesh va dien tich be mat la 500 mVg) va APDC dugc dat mua tir Sigma Chem,Co.St.Louis. Dung dich APDC 0,l%Jw/v) tron^ etanol dugc sir dung lam tac nhan tao hgp chat ndi phirc.
2.2. Chuan bi cot
Cdt thiiy tinh chua khoang 0,5 g nhua Amberlite XAD-7 (chi^u c a o j d p day - 1,5 cm) dugc dimg d6 co dac mau crom. Nhya XAD-7 dugc rira sach Ian lugt vdi NaOH 1 M, nudc, HNOj IM, nudc, axeton va nudc. Sau dd nhua dugc siy khd d 60°C trong 2 gid trudc khi nap vao cdt Chat hap thu dugc rtta vdi etanol va HNOi IM va dugc nia tri?t de bang nudc den khi nudc nia la trung tinh. Sau moi lan sir dyng, nhira trong cgt dugc nia lai vdi nudc va axit sunfuric 0,05M, sau dd bao quan nhya trong nudc.
2.3. Quy trinh tach, co dac va xac dinh crom 2 3 1 Xdc dinh Cr(VI)
Phuang phap dugc thir vdi dung dich mau gia trudc khi ap dung cho cac mau moi trudng De tdi iru hda viec chuan bj cgt va phuang phap cd dac mau, su dung 100 ml dung dich mau cd ham lugng Cr(Vl) la 0,Img/L va Cr([II) la D,05mg/L. Dung dich nay dugc dieu chinh pH den 2,0 va sau do them 5 ml dung djch APDC 0,1% w/v. Dung djch Cr-APDC dugc cho qua cgt vdi toe do ddng la 5 ml/phut. Dang Cr-APDC gifl lai tren cdt se dugc nia giai vdl 10 ml dung djch H2SO4 0,05M trong axeton. Dung djch nia giai sau do dugc cho bay hai tdi gan khd. Phan can cdn lai dugc pha loang vdi HNO3 1 M cd chiia cac chat phu gia can thiet den 5ml. Lugng Crom trong dung dich riia giai dugc xac dinh bang FAAS
2.3 2 Xdc dinh crom tdng
Tdng Crom dugc xac djnh gidng nhu Cr(VI) bang phuang phap mo ta d tren sau khi oxy hda Cr(in) thanh Cr(VI) bSng each them KMnOj trong mdi trudng axit. De tien hanh oxy hda, them 4 hoac 5 gigt dung djch KMn04 0.02M va 0,5 m! H2SO4 dac vao 100 ml dung dich cd ham lugng Cr(VI) la 0,lmg/L va Cr(III) la 0,05mg/L. Cdc dugc day bang nkp kinh ddng hd va dugc dun ndng nhung khdng de sdi (-45"C) trong khoang 15 phut de oxy hda hoan toan. Dung djch thu dugc dugc lam lanh va them vao tirng gigt dung dich natri azit (2,5%. w/v) de khu lugng du KMnO^ Sau do, dung djch dugc chuyen sang binh djnh miic 100 ml. Them 5 ml dung dich 0,1% APDC va pha loang bang nudc den vach roi lie deu.
Dieu chinh pH cua dung dich bang may do pH
T^P CHi KHOA HQC & CONG NGHE CAC TRUOiNG DAI HOC KY THUAT • SO 92 -2013 va diSu chinh den pH=2,0. Sau khi oxy hda
Cr(III) thanh Cr(VI) bang ICMn04 trong moi tnrcmg axit, phuang phap dugc ap dyng de xac dinh tong crom. Lugng Cr(ni) dugc tinh bang hieu so ciia lugng crom tdng cho lugng Cr(VI) da duDC xac djnh d tren.
Do thu hoi dugc tinh theo cdng thiic:
^ x 100 3. KET QUA VA THAO LUAN 3.L Cac yeu to anh hirdng den hicu suat thu hoiciJaCr(III)vaCr(VI)
i, /. I. Anh hudng cua pH
Hieu suat thu hoi ciia Cr(III) va Cr(VI) da dirge nghien ciiu trong pham vi pH tir 1,0- 6,0. Nhu thiy d hinh 1, lucmg thu hoi >94%
dirge tim thay tai pH 1,5-2,5 vdi Cr(VI), K^
qua cho thay gia tri pH tdi uu la 2,0.
Hinh 1. Anh hudng ciia pH din sir thu hoi cdc dang ciia crom tren XAD- 7
3.1.2. Anh hu&ng cua luang phdi tir Khi khdng them APDC vao dung dich thi do thu hdi cua Cr(VI) < 8%. Gia trj do thu hoi tang khi them APDC vao dung dich trudc idii cho qua cgt. Han nua, do thu luang ddi on dinh -95% sau khi them >3,0 mg APDC (0,1 % w/v trong 3 ml etanol). Trong tat ca cac nghien cihi va sau, 5 mg phdi tu APDC (0,1% w/v trong 5 ml etanol) da dugc sii dung.
^mh 2. Anh hu&ng cua lugmg APDC den su thu hdi dgng CrfVI) tren XAD- 7
3.1.3. Anh hu&ng cita luang vdl lieu hdp phu (chieu cao l&p hap phif)
Gia tri dp thu hdi cho crom khdng djnh lugng dugc neu dimg it ban 0,25g XAD-7 Mat khac, hieu suat thu hdi >95% dat dugc vdi 0,25-0,5g XAD-7, Tit ca cac thi nghiem dugc thyc hien vdi 0,4mg XAD-7.
Htnh 3. Anh hu&ng ciia lucmg nhua doi v&i do hdp phli ciia Cr(Vl)
3.1.4. Anh huong cua loc do nap mdu qua col Toe dp ciia ddng chay qua cdt Hen quan true tiep den lugng phue Cr(VI)-APDC dugc giu lai trong nhya. Do dd, 100 mi mau gia da duoc cho qua cac cdt vdi cac tdc do khac nhau trong khoang 1-10 ml/phiit Thuc nghiem thay rang hieu suat thu hdi dat dinh lugng vdi toe do ddng chay khoang 1-5 ml/phut Do vay, Idc do ddng chay 5,0 ml/phiit da dugc lya chgn cho tat ca cac thi nghiem tiep theo.
Hinh 4. Anh hu&ng cua tdc do nap mdu qua cot dot v&i do hdp phu cita Cr(Vl) 3.1.5 The tich vd logi dung moi rira gidi
De rira giai phirc Cr(VI), da sir dung cac dung dich axit sulfuric, axit nhric, axeton va ket hgp cac dung mdi nay vdi nhau de lam chat rira giai. Ket qua thuc nghiem (Bang I) cho thay loai dung mdi rira giai tdt nhat (hieu suat thu hoi dat 97%) la dung dich H2SO4 0,05M trong axeton. The tich dung mdi thich hgp la lOml. Do dd, trong cac nghien cuu ve sau, 10 ml dung dich HiS0,i 0,05 mol/L trong axeton dugc dimg lam dung dich rua giai.
TAP CHi KHOA HOC & CONG NGHf CAC TRlTCfNG DAI HQC KY THUAT • SO 92 - 2013 Bang I. Anh hudng cita loai dung mdi rua gldi
va the tich dung mdi nia gidi ddnh gid qua hiC'u sudt thu hdi cita phiic C 'r( VIJ -A PDC
Loai dung djch riia giai HNO,
HNOi trotii; axeton HNOi Irorii; axclon Axeton Axeton ll,SOi H,SOi trong axeton ii'SO) trone axeton H2SO, Irong axeton
C (M)
1 1 1
0,05 O.O.'i 0,05 0,1
V (ml)
10 5 10 5 10 10 5 10 10
H, % ( C r V I ) 5,7 65,7 94,5 33,4 54,1 5,3 87.9 97,2 93,8 3 1.6. Anh huo'iig cua the tich mdu
Khi ndng do cua crom trong cac mau Ihyc la qua thap ddi hdi phai lam giau lugng crom. Viec tdi uu hda lugng mau phan tich dugc thuc hicn bang each nghien ciru do thu hdi ciia Iugng \c\ kim loai (10 (ig Cr(Vl), 5 fig Cr(lII)) trong cac the tich mau khac nhau trong pham vi tir 50-500 ml. Ket qua (Hinh 5) cho tha>', dd thu hdi dn dinh cho den the tich la 250 ml. Tren 250 inL, do phue hdi giam khi tang the lich mau. Trong nghien ciru nay, bdi vi the tich cudi ciing de dua vao do bang AAS la 5 mL nen ve mat ly thuyel he sd lam giau mau cao nhat la 50 cho tha tich mau la 250 ml.
ITinh 5. Anh humig cuu the lich mdu (lot v&i khd ndng giir lgi Cr(Vl) Iren nhua
3.1.7. Anh hirdng cita cdc ion
Cac ion Ca'*. Mg"', B a ' \ Cir*, Cd"', Pb-*, Zn-", Fe'*. Mn" , PO,'" va SO4'" vdi cac ndng do khac nhau dugc them vao mau nghien cii'u de xac dinh tac ddng ciia cac ion nay ddi vdi kha nang thu hoi lugng vet crom, Ket qua thuc nghiem (Bang 2) cho thay, hieu suit thu hoi crom it bi anh hudng ciia cac ion khac cimg cd mat trong dung dich.
Bdng 2. Anh hudng cua mpt so ion doi vdi dg thu hoi cua Cr(Vl) tren nhuaXAD7
Ion M g " , B a " , C a "
C d "
Pb"
M n "
Z n "
C u "
F e "
SO/", PC,'"
Hon li(7p eae ion*
C, me/I 500
10 10 10 10 10 5 200
H , % 94,48 93,12 94,56 93,21 92,34 95,23 95,1 94,53 91,23
* Hon hap cdc ion nghien cuu tai nong do toi da 3.2. Xac djnh crom tdng, Cr(VI) va Cr(III) Irong mau nirdc may, nurd'c thai
Trudc tien mau gia cd chiia mgt Iuong khac nhau ciia Cr(Vl) va Cr(III) da dugc chuan bj. Sau dd, cac ion Cr(III) trong cac dung dich mau gia dugc oxy hda thanh Cr(VI) bang each sii dung KMn04 trong mdi trudng axit. pH cua cac dung dich dugc dieu chinh den 2,0 bang each them can than 0,05M H2SO4. Sau do, ap dung quy trinh da dugc trinh bay d tren cho cac dung dich nay. Ket qua (Bang 3) cho thay phucmg phap de nghj cd the dugc ap dung cho viec xac djnh crom tdng.
Being 3. Xdc dinh long crom irong cdc dung dich
Mau so
1 2 3 4 5
Lirong C r o m dira vao (HS/L) C r (VI)
0 50 75 100 150
C r (III) 150 100 75 50 0
C r t o n g 150 150 150 150 150
Lirong Crdm xac • dinh du^c C r tong
(HB/L) 141,7 147,8 142,3 145,7 146,2
H , % 94,46 98,53 94,86 97,13 97,46 Mau nudc cap va nudc thai phan tich theo phuang phap de xuat cd mgt vai thong so dau vao dugc chi ra d Bang 4.
Bdng 4. Thong sd ve chdt hrang mdu phdn lich
Ten man
Nuoc cap Ntroc thai KCN otnura
Hat Phong
Th&ncsS Nhiet do
°C 28,6 26,8
pH 7,35 7,04
BOD mg/L 5,23 85
COD mg/L 17 288
TAP CHi KHOA HQC & CONG NGHf CAC TRtj6T<G OAI HOC KY THUAT * SO 92 - 2013 irg J. Xdc dinh Cr(IIl). Cr(Vl) m long crom
Irong cac man iiir&c may va nuac song
Ten mau
Nuoc cap Nirm Ihai KCN Nomura
Hai Phong
II I
cnvi) 0 5 10 0 10 20
Crlllll 0 10 5 0 20 50
Lugng Crom tim duyc
(ni^/L) c n v t i KPH 5.2 10,2 12,2 23,1 31.8
Crlllll KPH 9.4 4.6 86.1 104.5 135,1
Hi|u sual
(%)
i n v i
104 102
109 98
Crlllll 9.) 92
92 98 j
Ket qua thuc nghiem (Bang 5) cho thdy, phuong phap nay ap dung dk xac dinh luong vet cua tung dang crom trong mau nudc cd dp chi'nh xac cao (hieu suat thu hdi dat tir 92- 109%).
4. KET LUAN
Da nghien cuu qua trinh tach, lam giau Ci(III) va Cr(VI) hkn^ nhua XAD-7. He sd lam giau thu dugc la 50 lan. Chung minh dugc quy trinh phan tich Cr(lll) va Cr(VI) bang phuang phap F-AAS sau khi chiet pha ran vdi nhua XAD-7 cd do chinh xac, dd chon loc cao va quy Uinh thyc hien la kha don gian, kinh te.
TAI LIEU THAM KHAO
1. QCVN 01:2009/BYT, Quy chuSn ky thuat qudc gia ve chat lugng nudc an uong.
2. QCVN 24:2009/BTNMT, Quy chuan ky thuat qudc gia ve nudc thai cdng nghiep, cdt A
3. Chromium in Drinking-water, Guidelines for drinking-water quality. 2nd ed Vol, 2, Health criteria and other supporting infonnation World Health Organization. Geneva, 1996,
4. EPA 218.4, Chromium, Hexavalent (AA, Chelation Extraction)
5. Pei Liang, Taqing Shi, Hanbing Lu, Zucbeng Jiang, Bin Hu, Speciation of Cr(I[l) and Cr(Vl) by nanometer titanium dioxide micro-column and inductively coupled plasma atomic emission spectrometry, Spectrochimica Acta Part B 58, 1709-1714 (2003).
6. Nguyen Xuan Trung, Pham Hdng Quan, Vu Thi Trang. Nghien ciiu kha nang hap phu Cr(lll) \a Cr(VI) tren vat lieu chitosan bien tinh, Tap chi phan tich hoa ly va sinh hpc T2, sd 1, tr63-67 (2007)
Tran Thj Thiiy - Tel: 0977.120,602, Email [email protected],vn Trudng Dai hoc Bach khoa Ha Ngi
Sd 1 - Dai Cd Viet - Hai Ba Trung- Ha Ngi
