Rapid treatment of atrazine-contaminated water by nickel/iron bimetallic system

Journal of Environmental Sciences Vol. 16.No.6,pp.925- 927 ,2004ISSN 101-0702Article ID: 1001-0742(2004)06-0925-03CLC number: X52 Document code: ARapid treatment of atrazine-contaminated water by nickel/iron bimetallicsystemWEI Hong，TONG Shao-ping"，WANG Hong-yu's，LIU Wei-ping(1. Institute of Environmental Science . Zhejiang Universily ，Hangzhou 310029. China. E- mail: weihong0521 @ sohu . com: 2. Department of AppliedChemistry. Zhejiang Universily of Teechnology. Hangzhou 310032. China; 3. College of Civil Engineering and Architecture, Zhejiang University ofTechnology, Hangzhou 310032, China)Abstract: The utility of nickeliron in the remediation of atrazine- contaminated water was investigated. The experimental results showedthat nickel/iron had effective catalytic activity in dechlorinating atrazine under acidic conditions. The dechlorination reaction approximatelyfollowed the first-order kinetics under the experimental conditions ( nickeliron: 1.0 g/250 ml; Comoma = 20.0 mg/L). the reaction rateincreased with decreasing pH value of the reaction solution and increasing the proportion of Ni: Fe within 2.95% . For cndition with 2.95%nickeliron, the reaction rate constants were 0.07518( R = 0.9927). 0.06212( R= 0.9846) and 0.00131 min'(R=0.9565) at pH=2.0, 3.0and 4.0. respectively. HPLC analysis was used to monitor the decline of atrazine concentration.Keywords: atrazine; nicke/iron bimatllic system; dechlorination reaction; first order kineticslron powder(99%，40- -70 mesh), NiSO, .6H20 wasIntroductionof analysis purity, methanol was HPLC reagent and alrazineThe widespread use of triazine pesticides in agriculturewas purchased from Chemical Service(USA), purity > 99%.applications has resulted in extensive groundwater1.2 Preparation of nickel/iron bimetalliccontamination. The triazine is a group of chemically similarNickel/iron was prepared by weighing 30 g of iron andherbicides including atrazine， cyanazine， propzine andwashing the particles in 0.1 mol/L H2SO。to remove thesimazine primarily used to control broadeaf weeds. Amongsurface oxides and contaminants, the iron was rinsed withthese herbicides, atrazine is one of the most widely useddeoxygenated water to remove the residual acidity， thenagriculture pesticides in the world. Because it can persist inimmersed in certain concentration of 0.1 mol/L NiSO,water and mobile soil, atrazine is among the most frequentlysolution to produce nickel/iron bimetallie system by shakingdetected pesticides in ground and surface water ( Balmer,he mixture violently for appropriate time， different1999).proportions of nickel/iron system were got by controlling theIn order t0 remediate atrazine-contaminated waler,shaking time. The bimetallie system was rinsed withseveral researchers have studied elimination of thisdeoxygenated water， then filtered， dried under nitrogencontaminant using different treatment methods. Among theseprotection at 80C for 10 h.methods ，atrazine dechlorinated by using zero-valent Fe' is a1.3 Reaction conditionspromising remnediation technology ( Dombek, 2001; Chauch,The desired atrazine stock concentration was prepared2000; Monson, 1998).using methanol as the solvent. This stock solution was storedThere is still no report on the dechlorination of atrazinein refrigeralor at about - 5C，250 ml sample containingby using bimetallic system. Recently the high reactivity of20.0 mg/L of atrazine was prepared by pipetting the desiredPd/Fe bimetallic system in treating low- molecule chlorinatedamount of the stock solution and using water as solvent. Thehydrocarbons and chlorophenols has been demonstratedreaction was proceeded in a 250 ml conical flask with 1.0 g(Rosy，1995; Liu, 2001),but the cost of Pd limits thisprefilled nickel/iron; the flask covered with a rubber plugtechnology’s widely application . Nickel/ iron is also proved towas placed on the magnetic stir operating at 20C and stirringe efective in treatment of polychlorinated hydrocarbonsat 300 r/min. The pH value of the solution was regulated by(Que, 1998)，but the catalytic reactivity of bimetallice systemadding 1 .0 mol/L H2SO4 , and controlled by pHs-29A aciditydepends on organic compounds ’properties ( Que，1998 ;meter . The duration of the reaction was approximately 90 minKim, 2000). Considering the reasons above- mentioned andduring which 3.00 ml aliquots of the atrazine samplethe cost of Pd, we chose nickel/iron as a reducing agent loperiodicaly were removed for HPLC analysis.study is catalytic activity on the dechlorination of atrazine, 1.4中国煤化工the reaction kinetics was also discussed.oduct were analyzed byHighYH. CNMH Gapy(HPLc). HPLC1 Materials and methodssystem consisted of a SPD- 10Avp photodiode array detector1.1 Chemicalsturned to 222 nm， a SIL- 10Advp automatic injector, twoFoundation ilem: The National Nalural Science Foundation of China( No. 30270767); ”Correponding author926WEI Hong et al.Val.16HPLC pumps, a CTO-I0Avp oven and Class-vp data system .。70The seperation column was YWG Cig250 mmx4.6 mm i.d,6010 μm). The mobile phase was degassed solution of 65/35methanol/ water( ubuffered). flow rate was 0. 80 m/min.Weighed nickel/iron sample 0.1 g，dissolved in theCo=20.0 mgLsolution of2: 1(HCI: HNO3) and diluted to an appropriatepHu3.0写20Reaction time, 30 minconcentration，then the amount of nickel and iron powdercould been determined by alom absorption analysis ( Analytiko4Jena GmbH, Germnany) .Loading of Ni on the surface ofFe'2 Results and discussionFig.2 Eleet of nickel/iron proportion on the declorination eficiency of2.1 Evolution of HPLC and UV absorption spectraatrazineFig.1 shows the variation of HPLC chromatogram and10UV spectra of altrazine during the reaction. In Fig.1a, theretention time of atrazine is 10.039 min, and that of its0Fdechlorination by-product is 3.025 min; in Fig. lb, thespecific atrazine band at 222 nm disappears gradually with theband appearance of is dechlorination by-product. These40-- Co=20.0 mg/Lresults are in accord with the references ( Dombek, 2001;Co=15.0 mg/L.+ C=10.0 mg/LChauch，1999; 2000; Monson， 1998). At the end ofreaction the opalescence produced when a few drops ofHNO,-AgNO, agent was added into the solution， whichReaction time, %confirmed that atrazine was dechlorinated by nickel/ironFig.3 Dechlorination eficiencies of atrazine ut different initial concentrationssystem .by using 2.95% nickel/ironBy-product40dechlorination process in 90 min(rom 5.74 to 6.74), which can beaAtrazineexplained by the fllowing reactions(Eq (1)一(3)):R-Cl+ Ni/nFe' + H'→Fe2°+ R-H+Cl+Ni/(n - 1)Fe.(1)2H20+2e-→+20H+H，(2)oL200 220240 260 280Ore+2H20+4e→40H(3)Wavelength, nnEq.(1) shows the direct dechlorination of atrazine byNi/nFe'，waler and dissolved oxygen may compete for theFig.1 HPLC chrmatogam(a); UV spetra of atrazine soluion 20 mg/L(b)electrons provided by Fe' according to Eq. (2)--(3)，withwith nickeliron 1.0g. reaction lime=45 min, pH= 3.0the production of OH~，pH value of the solution increases2.2 Increase of atrazine dechlorination efficiency withwith reaction time as shown in Fig .4.the loading of nickel6.:The presence of nickel on iron powder speeds up thedechlorination eficiency of atrazine greatly, which is due to6.the larger surface of nickel/iron than that of iron and thes 6.2presence of nickel makes H2 be a strong reducing agent( Wei,6.1告602004). Fig. 2 shows that the dechlorination efficiency of5.atrazine increases with the loading of nickel when its5.:proportion is within 2. 95 %，then decreases slowly when theS1 1530456075 9amount of nickel is larger than 2.95%。2.95% nickel/ironReaction time, minis proved to be optimum under these experimental conditions●And the experimental results showed that the dechlorination中国煤化工h rectionon limeeficiencies of atrazine decrease with the increasing of theMHCN M. H God that nie/im(≤initial concentration of atrazine( Fig.3) .2.3 Effect of pH on the dechlorination eficiency of1.22% ) almost have no catalytic dechlorination efct whenpH≥4.0(Wei, 2003). Now the 2.95% nickel/iron waschosen to study the dependence of its catalytic activity on pHFig.4 shows the changes of pH of uncontolledl solution duringvalue because of its sufficient dechlorination efficiency asNo.6Rapid treatment of atrazine- contaminated water by nickel/iron bimetallic system927shown in Fig. 2，addition of catalyst was 1.0 g in each .enhanced corrosion of iron at low acidity(Eq. (1)); theexperiment, and the catalytic activity of nickel/iron is shownsecond one was due to atrazine' s protonation, approximatelyin Fig.5, atrazine was entirely dechlorinated in 60 min at pH33% of the atrazine was protonated at pH of 2.0, and only= 2.0，but no more than 6.0% al pH= 4.0 and ir1% at pH=4.0; in addition, the amount of H2 absorbed onuncontrolled system. These results indicated that the reactionnickel/iron surface also contributed a lot to this reactionwas greatly affected by pH value of the solution under our(Wei, 2003). The variation of the reaction rate constantsexperimental conditions. The degree of iron' s corrosion anobtained here can presumably verify this.alrazine' s prolonation at different pH values are probably the3 Conclusionsreasons for this .00 FNickel/iron had great catalytic activity on the treatmentof atrazine contaminated water, the dechlorination efficiency80 tis dependent on both the nickel loading and pH values of thesolution. 2. 95 % nickel/iron was proved 10 be optimum andpH value of the solution must be less than 4.0. The reaction40 tPH-4.0Uncotolld systomapproximately followed first-order kinetics under hexperimental conditions, the rate constants at pH=2.0, 3.0and 4.0 were 0.07518， 0.06212 and 0.00131 min~,01020304050607080 90respectively .Reaction time, minReferences :Fig.5 Dechlorination eficiencny of atrazine at diferent pH valueBalmer M E. Sulzberger B. 1999. Atrazine degradation in iradiaed iron/oxalate2.4 The reaction constantssysem: efet of pH and oxalae[ J}. Environ Sci Technol, 33(14): 2418-Rearranging the data shown in Fig. 5 with a linear2424.decrease of ln( C1C。) over time was obtained as shown inatrazine by zero- valent iron under acidie conditions[J]. Environ Pllution.Fig.6. This linear relationship revealed a pseudo-first order11: 21-27.reduction regarding the atrazine concentration. The reactionGhauch A. Rimu J et al. 1999. Rapid lreatment of water contaminated withrate conslants ( K ) can be determined from Fig. 6 asarazine and parathion with zero-vaient iron [J]. Chemosphere, 39: 1309-1315.0.07518，0.06212 and 0.00131 min~' for pH= 2.0, 3.0Ghauch A, Suptil J.2000. Remediation of s- rizine contaminated wate in aand 4.0, respectively. The correlation coffcients( R) forlaboratory scale apratus using zerovalent iron powder[J}. Chemxphere,the determined rate constants were 0.9927， 0.9846,41: 1835 1843.0.9565, respectively .Kim Y,Carraway E R.2000. Dechlorination of pentachlorophenol by zeru valentiron and modifed zero valent iroms[J]. Emvion Sei Technol .34: 2014 2017.LiuY H, YangF L e al.. 2001. Catalytic dechlorination of chlorophenols in: H-3.0water by plldium/iron[J]. Wat Res. 35: 1887-1890.: pH=4.0MonsonS J, Ma L et al., 1998. Confirmation and method development fordechorinated atrazine from reductive dehalogenation of alrazine wih Fe[JI.Analytiea Chimica Aeta, 373: 153-160.Quan x，LIU H J，YANG F L et al.， 1998. Dechioriation of threeplylorinated hyroearbons in waler using bimtlli system[J]. ChinaEnironmental Science, 18(4): 333366Roy M. Quintus F. Nie K, 1995. A method for the rapid dechorination of low0102030405060708090molecular weight chlorinated hydrocarbons in water[J]. Waler Res, 29:Rcaction time, min2434-2439.Wei H, Li K B, TongSP et al.. 2004. Reductive dechlorination of arnaine byFig.6 Dechlorination efciencyg of atrazine at diferent pH valueNi/Fe bimetallie particles[J]. Environmnental Science. 25(1): 154- 157.The dependence of reaetion rate constant on pH value(Received for review Jauary 4, 2004. Acepted February 23. 2004)was affected by several factors: the first one was the中国煤化工MYHCNMHG