TAP CHi HOA HOC T. 49(6) 769-773 THANG 12NAM20il
NGHIEN CLFU DONG HOC Cd, Pb TRONG D A T VA T R A M TICH B A N G PHUONG PHAP CHII^T VOI EDTA
Nguyen Thj Minh Ldi', Le Lan Anh^*, Nastaran Manouchehn', Alain Bcrmond', Stephane Besanpon' Phong Hoa Phdn tich. AgroParisTech, Cpng hda Phdp
^Phong Hoa Phdn lich. Vi^n Hda hpc - Vi^n Khoa hpc vd Cdng ngh? Vi^i Nam Den Tda sogn 9-5-2011
Abstract
This research aims at optimization of extraction procedure using EDTA to soil and sediment samples taken at paddy fields, outskirts of Hanoi, Vietnam. Extraction yield of Cd from samples was found highly dependent on pH. On the other hand. pH did not strongly influence on the extraction of Pb. Cadmium was easily extracted in acidic medium with an efficLenc\ of up to 95% (in soil 8T4 - sandy soil). Tliis study also shows a potential contamination of Pb at some points where Pb was concentrated up lo 393 ppm. Kinetic extractions of Cd and Pb by using EDTA show that Cd was more mobile than Pb.
l.DATVANDE
Tic gii Z. Li vi cdng su quan niem rang de hieu dugc dung ve sir phin bd ciia cic dgng kim logi trong mdi trudng thi cin phii nghien ciru dpng hpc qui trinh chiet vdi mdt thudc thu [1]. Sau do, nhiing ling dung ciia cic md hinh dpng hpc dua den cic ket qua thi nghiem da cho phep thiet lap cic dgng kim logi vdi cic dp linh dpng khic nhau [2, 3]. Mpt vai thudc thu hda hgc, die biet li cic thudc thu tgo phirc vong cang da dugc sir dung trong nginh khoa hpc dit vdi muc dich phin tich kim logi vet trong dit.
Trong sd nhirng thudc thir tao phirc niy, EDTA (axit Etylen Diamin Tetra Axetic) li mdt trong nhiing tic nhin tgo phirc vdng cing hiru hieu da vi dang dugc quan tim trong nginh ndng nghiep nhu: danh gii kha ning linh dgng ciia kim logi [10-12] vi tich luy sinh hoc cua kim logi [8, 13], cic qua trinh cai tgo dit [14], nghien ciiu dang kim loai vet [15].
EDTA da dugc su dung chiet phan dogn trong phuang phip chi6t lien tuc cung nhu trong chiet rieng re. Die biet, da cd mot sd nhi nghien ciiu quan tam d6n viec sir dung EDTA trong cac phan dogn dpng hpc, sir dung EDTA nhu dung cy quan trie ti'ch IQy sinh hpc. Da cd nhu'ng nghien ciiu ve dpng hpc, vi du nghien ciru de tim nhiing dieu kipn th\rc nghipm toi uu [4] hogc dinh gii do linh dpng ciia kim loai vk trong dit [5] v i trim tich [6].
Nghien cdu ddng hpc ciia vipe chiet cac cation kim logi trong dat v i tram tich cho phep tien doin dp linh dgng va khi nang tich liiy sinh hgc. EDTA dugc sir dung nhu mot thudc thu chon lgc vi nd dugc
diing de chiet kim logi v8t trong cic thinh phin dit [8] va quang [9] khic nhau.
Trong nghien ciru niy, chiing tdi irng dung qui trinh chiet vdi EDTA de xic djnh ham lugng Cd va Pb trong dit vi trim tich d ngogi d Hi Npi. Ap dung nhiing phuang trinh tinh toin nham dinh gia tinh linh ddng ciia kim loai nang trong dat va tram tich.
Chiing tdi diing dung djch EDTA nhu mdt chat chiet. Phuang trinh tuong irng vdi ndng dp kim logi vet trong dung dich theo thdi gian nhu sau:
Q(t) = Q , ( l - e " - ' ) - l - Q 3 , ( l - e - ' - ' ) (1) trong dd: Q(t) (pg g"') la ndng dp ciia kim logi vet dugc chi8t bdi chit chiet trong thdi gian t; QL yi QSL (pg g'') tuong ung li lugng kim loai vet ban dau lien k^t vdi hai dgng ggi li dgng khdng ben (L) vi ben (SL); kL vi ksL (phiit"') la hing sd dgng hgc phii hgp vdi nhu'ng dang niy [8].
2. THLTC NGHIEM
2.1. Thiet bi
Miy quang phd hip thu nguyen tir model 2 5000 - Nhit Bin.
May lie Heildolph Reax 2 Shaker vi may ly tam EBA Hettich - Dure.
Miy do pH, pHmeter 99621- Bioblock.Sciencetific-Dan mgch.
Cin phan tich Toledo AG 135 - Phip.
He cat nudc Milli-Q plus - Millipore.
769
TCHH, T. 49(6), 2011 2.2. Chat chiet
Pha dung dich 2x10'^ mol/l muoi Na - Ethylene Diamine Tetra Acetic (EDTA) nhu sau: cho 0,744 g EDTA (khdng axit) vao 1 lit nudc cat vi khuiy bing miy khuiy tir cho den khi tan hoin toan. Dung djch EDTA dugc chinh den pH 6.5±0,05 bing NaOH.
2.3. Dicu Idcn thuc nghipm
Trong nghien ciru nay, chiing ldi ip dyng phuang phip quang pho hip thy nguyen tir vdi 2 ky thugt nguyen tu hda:
- Nguyen tu hda bang ngpn lira - FAAS khi axet>'len-khdng khi; ldc dg axctylen 2,5 1/phut, toe dg khdng khi 8.0 l/phiit.
- Nguyen tu hda khdng nggn lua (Id graphit) ETAAS, sir dyng chit modifcr Nll,ll2P04 khi do chit chuan va Cd, Pb trong d|ch chiet.
Pha dung djch chuan va modifcr: Pha dung djch chuin lir dung djch goc (1000 mg 1^ Ca, Fe, Pb, Cd, Merck. Due). Dung dich chuan de phin tich HTNT dugc pha trong HNO, 4% (v/v). NH4H2PO4 (0,2 mg) dugc diing lam modifcr dc xic dinh Cd, Pb bing HTNT Id graphit (ETAAS).
2.4. Dia diem lay man
Mau dugc liy tir 3 di6m trdng rau d ngogi d Hi Ngi: Ddng Anh, Ciu Dien vi Thanh Lipt.
Tgi 3 diem niy chiing tdi da thu khi nhieu miu, nhung trong bio cio nay chi chgn 4 miu dit vi 3 miu trim tich dgi dien.
Cau Dien: dat va trim tich dugc liy tgi dia diem gin chg Canh, noi cd nhieu khi nang bi d nhiem bdi rac thii va nudc thii din cu xung quanh.
Ddng Anh: dat vi trim tich dugc liy tgi dja diem ben cgnh muong nudc thii ciia nhi miy tam Igp fibro-ciment vi Ca khi Ddng Anh.
Thanh Lipt: dit vi trim tich dugc liy tai rugng trdng rau dimg nudc sdng Td Ljch cgnh nha may Son Tdng hgp Ha npi de lam nudc tudi.
Gia cong mdu. Mau thu vc dugc phai khd d nhiet dp phdng neu trdi ndm thi phai cho vao tu say d nhipt dp 65°C cho dSn khd hoin toin; nghien bing coi ma nao vi riy qua riy cd 0,25 mm, sau dd ddng gdi bio quin de chd phin ti'ch.
2.5. Phvung p h i p thirc nghipm 2.5.1. Chiit vai EDTA
Can 1,0 g miu phan tich cho vio cic binh, them 10 ml dung dich EDTA 2x10'' M (pH = 6,5 dugc chinh vdi NaOH), lie mau tron^ 24 gid bing miy lie Heildolph Reax 2. Ly tam bang may ly tam by EBA Hettich, lgc de liy dung djch va loai bd cin.
Le Lan Anh va cgngstf Sau dd dung djch dugc phin ti'ch bing phuong phap quang pho hip thy nguyen tu (AAS).
2.5.2. Phdn lich dat
Xic djnh cic thdng so hda ly ciia miu nhu pH, Ca va i"c.
pH t\r nhien ciia mau dugc do trong dung djch huyen phii ty Ip mau:nudc = 1:10. Dung djch phai dugc dc cin bing trong 20 phiit sau khuay rdi mcrj
^om. . . .
Phi miu bing hdn hgp cudng thiiy de xic djnh Ca Vii I c vi nong dp tong ciia Cd, Pb.
2.5 3 C 'hiei dpng hpc vdi EBTA
Dpng hgc ciia qui trinh giai hip kim loai khoi dill dugc thyc hipn trong mpt chu ky 24 gid. Chiing tdi chgn thdi gian nghien ciru nhu sau: 4, 8, 12, 15, 20, 30, 45, 60, 90, 120, 150, 200, 250, 300 va 1440 phiit.
Qui trinh Ihi nghidm: Cho vao Ig nhya PE co dung tich 100 ml, 9 gam dit da nghien mjn va 90 ml dung djch EDTA 2 lO'^M didu chinh d^n pH 6,5 vdi dung djch NaOH. Rdt dung djch EDTA cing nhanh cang tot, sau dd cho ngay Ig chiet vio miy khuay va tinh thdi gian tuong irng dgng hgc Ii 0 phut.
3. KET QUA VA T H A O LUAN
3.L Chiet vdi EDTA
Di dung dung djch EDTA 2^ 10"' M d^ chiet Cd, Pb trong 4 mau dat va 3 miu tram tich. Ndng dp Cd, Pb dugc xic djnh bdi phucmg phip quang phd hap thy nguyen tir khdng ngpn lira ETAAS. Ddi vdi moi mau chiing tdi tien hanh thi nghipm vdi hai miu lap lgi, ket qua trong phin niy li gia tri trung binh ciia hai sd lipu do dugc.
Trong bing 1. ty lp phin tram ciia Cd di dirpc chiet bdi dung djch EDTA 2x10"^ M trong miu d^t 8T4 li cao nhit, chiem 94,81% (xip xi 100%). Tiep t h e o l a m i u d a t d T l . c h i e m 80,70%. DiSu niy co the giii thich do pH ciia cic miu dit niy thap, ndi each khac nhu'ng mau dat niy cd tinh axit (pH = 5,52 va 5,94), cadimi de linh dgng.
Ngugc lgi, nhiing miu dat cd pH cao, dat c6 tinh chat kiem, ty lp phan tram Cd dugc chifit rat thip. Vi dy: 30,15% trong mlu 4T3 (pH = 8,75) va 47,45%
trong miu tram tich 1T2 (pH = 7,84).
Cd khic so vdi Cd, ham lugng Pb dugc chiet bdi EDTA phu thupc it han vao pH, dgt gii trj cao nhat li 57,62% trong mlu dat 8T4 vdi pH thip nh§t.
Nhung d cic gii trj pH khic nd hiu nhu khdng thay doi theo dung qui lu§t. Tiep theo la 35,36% va 30,05% trong mlu 5T1 v i 5T3, tuang img. Va 6 miu dat cd pH cao nhat tuc li dit cd mdi trudng
TCHH, T. 49(6), 2011 kiem (pH = 8,75), do
trong EDTA thip nhjt (9,17%). Dieu nay co nghi
Nghien ciru dong hoc Cd, Pd...
mlu 4T3, thi ty le chiet moi tirong quan ddi vcri Pb khong dugc ro net nhir Cd, hay noi each khac Cd linh dgng han Pb.
Bdng T. KSt qua Cd .jnj va chiet EDTA trong dSt, tram tich, ty le % chiet, pH, Ca, Fe
Mau Dat Dat Dat Dat Tram tich Tram tich Tram tich
Ten mau 2T4 4T3 6T1 8T4 1T2 5TI 5T3
CdEDTA (ppm) 0,435 0,041 1,049 0,073 0,177 0,640 0,483
CdiSns (ppm) 0,783 0,136 1,300 0,077 0,373 0,917 0,730
%Cd (CdEDTA/Cdiing)
55,56 30,15 80,70 94,81 47,45 69,79 66,16
pH 7,57 8,75 5,94 5,52 7,84 7,15 7,11
Ca (ppm) 6,07 3,27 2,075
0,65 13,6 2,825 2,96
Fe (ppm) 49,61 40,141 55,888 4,803 45,761 52,23 51,19 Bdng 2: Ket qua Pb i„„^ va chi^t EDTA trong dat, trim tich, ty le % chiet, pH, Ca, Fe
Mau Bat Dat Dat Dat Tram tich Tram tich Tram tich
Ten mau 2T4 4T3 6T1 8T4 1T2 5T1 5T3
PbEDTA (ppm) 13,817 3,039 12.818 9,623 5,792 138,83 39,89
Pbi6,j (ppm) 47,72 33,132 51,242 16,70 36,917 392,57 132,727
%Pb (PbEDTA/Pb,s.B)
28,95 9,17 25,01 57,62 15,69 35,36 30,05
pH 7,57 8,75 5,94 5,52 7,84 7,15 7,11
Ca(ppm) 6,07 3,27 2,075
0,65 2,96 13,6 2,825
Fe (ppm) 49,61 40,141 55,888 4,803 51,19 45,761 52,23
3.2. Chiet dpng hoc danh gia kha nang linh dong thay ddi rit nhanh trong thai gian diu vi sau do se ciia Cd, Pb trong mau dit chim din. K6t qui dugc th6 hien rd trong cac dd thi
Dudng cong giii hip (dudng cong chiet) cd su hinh 1 va 2.
Hinh I: Dudng cong chi^t Cd ciia 3 miu dat nghien ciru
Hinh 2: Dudng cong chiet Pb ciia 3 miu dat nghien ciru
771
TCHH, T. 49(6), 2011
Khi xir ly ket qui trong phan chiet dgng hgc, chiing tdi sir dung phin mem xii ly so lipu SigmaPIot 11.0 de tinh toan cac thdng so thong kc khic nhau nhu: ndng dp khdng ben Qi. vi cac hing so dgng hgc nhu kt. kLs-
Li Lan Anh va cgngsyt Nong dg Cd, Pb khdng bdn da dugc tinh theo phuong trinh (1) d tren cho 3 miu da dugc trinh bay trong bing 3 v i 4, Cic ket qua chiet don vdi EDTA cung nhu ty lp phan trim ciia ndng dg khdng ben so vdi nong dg chiet bdi EDTA cung dugc trinh bay trong bing.
Bdng 3: Nong dp Qi.ciia Cd trong mau, ty lp % chiet ciia Cd/EDTA Ten m l u
214 6T1 8T4
k, 0,396 0,594 0.726
ksl 0,0045
0,006 0,0131
Ql (Cd - ppm) 0,337 0,974 0,054
E D T A (Cd - ppm) 0,435 1,049 0,073
% Cd QI/EDTA 77,47 92,85 73,97
Ten mau 2T4 6T1 8T4
Bdng 4: Nong dg Qi,
kl.
0,212 0.257 0,325
k.s, 0,002 0,007 0,0066
ziia Pb trong mau, Iy I? % chiet cua Pb/EDT/^
Ql (Pb - ppm) 3,7952 5,3311 4,6306
E D T A ( P b - p p m ) 13,817 12,818 9,623
% Pb QI/EDTA 27,47 41,59 48,12
Chimg tdi thay trong bing 3 vi 4, cic hing sd dgng hpc kt trong phuang trinh chiet Cd ciia tat ci cic miu deu cao hon cua Pb. Hang sd ddng hpc kL cua Cd tir 0,396-0,726 min'', cic gii tri niy Idn hon cic gii trj cua chi (tir 0,212-0,325 min"'). Dieu niy cho thiy Cd linh ddng hon Pb, hay ndi cich khac Cd de ding chiet vdi EDTA hon so vdi Pb. KSt qui thu dugc trong nghien ciru niy ciing tuong thich vdi cic ket qui da cdng bd ciia A. Bermond vi cgng sy [ 16].
4. KET LUAN
Hien nay, nghien ciru dgng hgc dugc ip dung nhu mdt phuang phip xac dinh dgng ciia vet kim logi nang trong dit vi tram tich. Trong bii bio nay, chiing tdi di dimg tic nhan tgo phirc vdng cing EDTA trong qui trinh chiet vdi ndng dp dung djch 0,002 M, pH ^ 6,5, thdi gian chiet Men tyc tir 4 phiit dan 24 gid. Xic dinh him lugng Cd va Pb trong djch chilt thu dugc bing phuong phip quang pho hap thy nguyen tir khdng nggn Ida (ETAAS). Diy li quy trinh dugc ip dyng de nghien ciiu dgng hgc khdng chi cho Cd vi Pb mi c i ddi vdi cac kim logi nang khic trong dat vi tram ti'ch.
Han nira, vipe sir dyng EDTA de chiet cic kim loai lugng vet trong dit la phucmg phap rat kha thi de phan bipt dgng khdng b6n (chiet nhanh hay dd chik) va ben (chiet cham hay khd chiet) ciia cic cation kim logi.
T A I LIEU THAM KHAO
1. Z. Li, L. M. Shuman, Exlractability of Zinc, Cadmium, and Nickel in Soils amended with EDTA.
Soil Sci, 161(4), 226(1996).
A. Bermond, [. Yousfi, J. P. Ghestem, Kinetic approach to the chemical speciation of trace metals m soils. Analyst 123, 785 (1998).
J. Yu, D. Klarup. Extraction kinetics of copper, zinc.
iron and manganese from contaminated sediment usingdisodium ethylenediaminetetra acetate. Water Air Soil Pollut., 75. 205 (1994).
David Fangueiro, Alain Bermond, Eduarda Satos, Helena Carapupa, Armando Duarte, Heavy metal mobility assessment in sediments based on a kinetic approach of the EDTA extraction: search for opiimal experimental conditions. Analytica Chimica Acta, 459.245-256(2002).
J6r6me Labanowski, Fabrice Monna, Alain Bermond, Philippe Cambier, Christelle Fernandez, Isabelle Lamy, Folkert van Oort, Kinetic extraction lo assess mobilization of Zn. Pb. Cu and Cd in a metal - contaminated soil: EDTA vs citrate. Environmental Pollution \x 1-9(2007).
David Fangueiro, Alain Bermond, Eduarda Santos, Helna Carapupa, Armando Duarte. Kinetic approacii to hecny metal mobilization assessment in sedimenl:
choose of kinetic equations and models to achieve maximum information, Talanta, 66, 844-857 (2005).
Dott.ssa Chiara Galas Thesis: Assessment of race metal bioavailability in soil and river waters using different analytical techniques to predict metals uptake by biota. University study of Roma (2008).
A. Bermond, G. Varrault, V. Sappin-Didier, M.
Mench. A kinetic approache to predict soil trace metal bioavailability: preliminary results, Plant and Soil, 275,21-29(2005).
D. Fangueiro, A. Bermond, Eduarda Santos, Helena Carapu9a, Armando Duarte. Heavy metal mobility
T C H H , T. 4 9 ( 6 ) . 2011
assessment in sediments based on a kinetic approach of the EDTA extraction- search for optimal experimental conditions. Analytica Chimica Acta, 459, 245-256 (2002).
10 T. Sterckerman, A Gomez, H Ciesielski, Sod and waste analysis for environmental risk assessment in France. Science of the Toral environmental, 178, 63- 69(1996),
11 J. M. Alvarez, L. M. Lopez-Valdivia. J. Novillo, A.
Obrador. Ml Rico. Compan.wn of EDTA and sequential extraction lest for phytoavailability prediction of maganeses and zinc in argicultural alkaline soils, Geoderma, 132.450-463 (2006).
12. N. Manouchehri, A. Bennond. Study of trace metal partitioning between soil - EDTA extracts and Chelexs - 100 resin, Analytica Chimica Acta, 557, 337-343 (2006).
Nghien cim ddng hpc Cd, Pd...
3. N. W. Menzies, M. J. Donn, P M. Kopinke.
Evaluation of extraciani for estimation of phytoavailable trace metal in soils. Environmental Pollulion, 145, 121-130(2007).
4 Q. R. Zeng, S. Sauv^, H. E Allen, W. H, Hendershot.
Recycling EDTA solutions used to remediate metal - polluted soils. Environmental Polulion 133, 225-231 (2004).
5. P. Ii Quevauviller, M. Lachica, E. Barahona, G Rauret, A. Ure, A. Gomez, H. Munlau.
Inlerlahoratory comparison of EDTA and DTPA procedures prior to certification of extraclahle trace element in calcareous soil. Science of the Total Environment, 178, 127-132(1996),
16. A, Bcrmond, G, Varrault, V. Sappin-Didier, M, Mcnch. A kinetic approach lo predict soil trace metal bioavailability preliminary results. Plant and Soil, 275.21-29(2005).
Lien h?' Le L a n A n h Vien Hda hpc
Vien K h o a hpc va C d n g nghp Vipt N a m 18 H o i n g Q u d c Vipt, C i u G i i y , H i N p i .