Adsorption-degradation mechanism of tris(2-chloroethyl)phosphate by a composite adsorbent of zero-valent iron sulfide and microorganism
Chlorinated organophosphate flame retardants(Cl-OPFRs),a new type of pollutant,are widely detected in environment and has resistant to degradation,easy-migratory and biological toxicity.Tris(2-chloroethyl)phosphate(TCEP)with the highest detection rate in environment was chosen as the target pollutant in this study,and a composition adsorbent(named S/ZVI-N1)that prepared by zero-valent iron sulfide and Novosphingobium tardaugens was used as research material,to explore the removal performance and degrading pathway of TCEP by the S/ZVI-N1.The results showed that the removal of TCEP by S/ZVI-N1 fitted to the quasi-first-order kinetic equation and Langmuir model,which indicated this process was a physical adsorption of monolayer primarily and the R2 of quasi-second-order kinetic equation also proved the chemical adsorption.The removal rate of TCEP by S/ZVI-N1 was 58.9%after 12h,which was higher significantly than that by Novosphingobium tardaugens or S/ZVI only(biodegradation rate was 32.95%and S/ZVI removal rate was 31.2%).The analysis of degradation products indicated that the decomposition of TCEP by S/ZVI-N1 was more thorough than that by ZVI alone.This proved there was synergistic reaction between the S/ZVI and Novosphingobium tardaugens to remove TCEP,and the optimal conditions of TCEP removal was pH 5-7 and 30-35℃.The intermediates analysis could deduce two degradation pathways of TCEP by S/ZVI-N1,that one was the C—Cl bond broken down by S/ZVI and another was O—P bond broken down by Novosphingobium tardaugens,and the final products were triethyl phosphate(TEP)and H3PO4,which meant the completely degradation of TCEP.
chlorinated organophosphate flame retardantscomposited adsorbentbio-degradationzero-valent iron sulfidedegradation pathwaytris(2-chloroethyl)phosphate
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