The Performance And Mechanism Of Fe(Ⅲ)-induced UV Simultaneous Photocatalytic Oxidation Of Organophosphate Esters And Removal Of Cr(Ⅵ)

Improper dismantling of e-waste brings serious pollution of persistent organic compounds and heavy metals.Chromium and organophosphate are widely detected in e-waste dismantling sites.Chromium and organophosphate are widely detected in e-waste dismantling sites.In addition,studies have shown that chromium and organophosphate have the characteristics of"carcinogenic,teratogenic and environmental persistence",which are easy to migrate and transform into the nearby soil and surface water,and then bring health risks to the surrounding residents.At present,the research on e-waste dismantling sites mainly focused on pollution investigation,exposure level and risk assessment,while the research on the remediation of contaminated sites is lacking.General methods such as ion exchange,adsorption and chemical precipitation are mostly limited to the removal of these two kinds of pollutants seperately.Photocatalytic technology can convert light energy into chemical energy by absorbing the energy of ultraviolet light,and has the ability of oxidation-reduction.It can oxidize refractory organic pollutants and simultaneously reduce heavy metals to achieve the purpose of collaborative removal of pollutants.It has the advantages of high efficiency,low energy consumption and low cost.In this study,we selected tris（2-chloroethyl）phosphate（TCEP）,of which preserve high water solubility,high detected concentration in the environment and severe environmental risk,as the research object.The degradation process of TCEP by UV/Fe（Ⅲ）photocatalysis technology was studied through degradation kinetics,single factor optimization,intermediate product identification and Escherichia coli test.On this basis,the remediation of TCEP and Cr（Ⅵ）by UV/Fe（Ⅲ）photocatalysis was studied.The main results and conclusions are as follows:The degradation of TCEP by UV/Fe（Ⅲ）photocatalysis was significant.The conditions of[Fe（Ⅲ）]₀=100μmol/L,p H=3,UV=2.2 m W cm^-2 and[TCEP]₀=100 mg/L cause 99%removal of TCEP after 120 min.Electron paramagnetic resonance（EPR）and tert butyl alcohol（TBA）quenching experiments confirmed that·OH was the main active species for TCEP degradation under UV/Fe（Ⅲ）.Under this condition,the TOC removal rate was 70%,which indicated that TCEP was not completely mineralized into CO₂ and H₂O,and some intermediate products were formed.We detected the degradation products of TCEP by ultra performance liquid chromatography-mass quadrupole time of flight-mass spectrometry（UPLC-QTOF-MS）,and found that there were three kinds of products:C₄H₉Cl₂O₄P（product A,m/z 222.9690）,C₆H₁₃Cl₂O₅P（product B,m/z 266.9954）and C₂H₆Cl O₄P（product C,m/z 160.9762）.Taking Escherichia coli as indicator bacteria,the inhibition rate of TCEP solution on the growth of Escherichia coli at different illumination time was studied.It was found that the solution after30 min illumination could promote the growth of Escherichia coli,which indicated that UV/Fe（Ⅲ）photocatalytic technology reduced the environmental risk of TCEP.UV/Fe（Ⅲ）photocatalysis technology can degrade TCEP and reduce Cr（Ⅵ）.The presence of TCEP promoted the reduction of Cr（Ⅵ）,but the concentration of Cr（Ⅵ）had little effect on the degradation of TCEP.In order to evaluate the redox cycle regeneration of Fe（Ⅲ）/Fe（II）,TCEP and Cr（Ⅵ）were injected after every 90-minute run in UV/Fe（Ⅲ）.The results showed that TCEP and Cr（Ⅵ）can be completely converted in five cycles.In the presence of Cr（Ⅵ）,the oxidation rates of chlorinated organophosphates（TCPP and TDCPP）and nonchlorinated organophosphates（TBP and TBOEP）,and the reduction rates of Cr（Ⅵ）were studied.The results showed that UV/Fe（Ⅲ）can treat the combined pollution of other OPEs and Cr（Ⅵ）.Therefore,Fe（Ⅲ）can be used as homogeneous photocatalyst to treat the compound pollution containing OPEs and Cr（Ⅵ）.