The Degradation Of Atrazine By Different Systems Of Peroxymonosulfate Activated By Nanoscale Zero-Valent Iron

Atrazine（ATZ）,an environmental endocrine disruptor,was once a ubiquitous herbicide.Since ATZ accumulates permanently in soil and water,the concentration of ATZ in the environment may exceeds the allowable maximum(3μg L^-1).It finally causes serious harm to human and wildlife health.Therefore,it is essential to develop the remediation processes and the underlying potential mechanism of ATZ in environment.Nanoscale zero-valent iron（nZVI）is extensively concerned and studied due to its ability of quickly removing priority pollutants in the environment.,The advanced oxidation reaction based on persulfate activation is a promising and efficient way for remediation of refractory organic pollutants.In the process of application,nZVI is easy to be oxidized and agglomerate,so the ability of nZVI needs to be improved in different ways.Therefore,the ability is modified by two different treatments,and it is used to activate peroxymonosulfate（PMS）for ATZ degradation in water.Two different treatments are as follows:（1）adding chelating agents in nZVI/PMS reaction system to increase the ability of activated PMS;（2）loading nZVI on biochar and use it activate PMS.The degradation reactions were carried out at slow vibration conditions.The ATZ degradation kinetics in these two different treatments,the influence of different factors on ATZ degradation,the degradation mechanisms and the properties of materials before and after reaction were systematically studied.The results are as follows:Firstly,the effects of adding three kinds of chelating agents（tartaric acid（TA）,tea polyphenols（TP）,ethylenediamine-N,N’-disuccinic acid（EDDS））on the ATZ degradation in the system of nZVI/PMS were investigated.The results show that TA has optimum promotion effects on degradation.In the reaction system of 4 mg L^-1ATZ,0.05 g L^-1nZVI and 0.5 m M PMS,the ATZ degradation rates are 11%without TA（in 30 mins）and 100%with TA(0.025g L^-1)respectively.The chelation of Fe ions and TA can promote the conversion of Fe³⁺/Fe²⁺,and activate PMS to produce more reactive oxygen species(SO₄^·-)for ATZ degradation.The TA dosages,PMS concentrations and different initial p H have great influences on the ATZ degradation in the TA/nZVI/PMS system.Moreover,in Cr（Ⅵ）and ATZ co-contaminated situation,ATZ can also be degraded effectively（the ATZ degradation rate reach 77%within3 h）;and the Cr（Ⅵ）completely reduced into Cr（Ⅲ）in the solution.Secondly,an environmental friendly compound（pBC-nZVI）was synthetized by loading nZVI on biochar prepared from pyrolysis of discarded masson pine trunk.The TEM results show that the morphology of pBC-nZVI are spherical particles with the distribution of chain clusters.Compared with nZVI,the specific surface area of pBC-nZVI increased by 62 m² g^-1.Compared with nZVI/PMS system,the ATZ degradation rates enhanced obviously in pBC-nZVI/PMS system.With the amounts of PMS and pBC-nZVI increasing,the degradation rates rise firstly and then decrease.The best reaction condition is 0.5 m M PMS with 0.1 mg L^-1 pBC-nZVI.With the increase of p H,the ATZ degradation rates decrease gradually;fulvic acid will consume the free radicals in the system and then inhibit the ATZ degradation.pBC-nZVI can slow down the oxidation rate and Fe²⁺release of nZVI,thus it can improve the efficiency of activating PMS.In the pBC-nZVI/PMS system,the main reactive oxygen species are SO₄^·-,HO·and ¹O₂.Seven intermediates are identified by the LC-TOF-MS detection,.The ATZ degradation pathways were mainly through dealkylation and alkylation oxidation.pBC-nZVI can be recycled due to its magnetic properties.Compared with nZVI,it is more stable in water and not easy to agglomerate.The results of toxicity tests show that pBC-nZVI whose toxicity to Escherichia coli is significantly reduced.This study provides two efficient ways for ATZ degradation in the environment and further theoretical basis and technical support for practical application.