Study On The Degradation Of Acetaminophen In The Fe~0/Persulfate/Sulfite System

In recent years,the environmental safety problems of organic pollutants such as organic medicines,personal care products and industrial dyes have become the research focus in water treatment field.In this study,a novel heterogeneous Fe⁰/PS/S（Ⅳ）combined system was developed and investigated for the degradation efficiency of acetaminophen.The mechanism of Fe⁰/PS/S（Ⅳ）system and the pathway of ACT degradation was also studied in the dissertation.Furthermore,the effect of inorganic anions,chelating agents and NOM on the degradation of ACT was investigated,which provide a theoretical support for the practical applicant of Fe⁰/PS/S（Ⅳ）system in water treatment.The main contents and results are as follow:（1）The effects of pH,dosage,temperature and dissolved oxygen on the degradation of ACT was examined in single factor experiments.The results showed the Fe⁰/PS/S（Ⅳ）system could achieve a significant synergy in the degradation efficiency of ACT.The degradation of ACT in the Fe⁰/PS/S（Ⅳ）system could accord with the pseudo-first-order kinetic.ACT could be effectively degraded at a broad pH range of 3-8,and the synergistic degradation of ACT under neutral conditions was the most obvious.The optiaml dosage of Fe⁰,PS and S（Ⅳ）was 1:1:1（molar ratio）.The degradation efficiency of ACT was significantly improved with increasing the reaction temperature,and the activation energy required for ACT degradation was 47.64kJ/mol.Dissolved oxygen had great impact on the degradation of ACT,which could react with SO₃^·-to generate SO₅^·-.（2）To study the mechanism of Fe⁰/PS/S（Ⅳ）system and the degradation pathway of ACT,the concentrations of soluble iron,PS and S（Ⅳ）in different systems during the reaction was observed,and the degradation products was identified by GC-MS and IC.The results showed the synergistic enhancement of Fe⁰/PS/S（Ⅳ）system was mainly attributed to the improvement of the oxidant utilization rate and the promotion of the Fe（Ⅱ）/Fe（Ⅲ）cycle rate.Quenching tests confirmed SO₄^·-（62.1%）was the main reactive oxygen species,SO₅^·- and HO^· accounted for as much as 26.9%and 11.0%individually.Direct cleavage of C-N bond on the benzene ring attacked by SO₄^·- and HO^lwas the main pathway of ACT degradation.（3）Under the optimal conditions for the degradation of ACT in the Fe⁰/PS/S（Ⅳ）system,the effect of inorganic anions,chelating agents and NOM on the degradation of ACT was investigated.The results showed the degradation of ACT could be inhibited by inorganic anions to different extents following the sequence of Cl^-<NO₃^-<HCO₃^-,Cl^- would lead to a positive effect with a low dosage,but a negative impact with a high dosage.The quenching effect of inorganic anions was the main reason for the inhibition of ACT degradation.As for the effect of chelating agents and NOM,the inhibitory effect of chelating agents and HA on the degradation of ACT was mainly due to complexation with Fe²⁺,depending on the complexing ability with Fe²⁺,and excessive chelating agents and HA would play as competitive pollutants.