Study On The Degradation Mechanism Of 4-Chlorophenol In The Peroxymonosulfate/Fe²⁺/Molybdenum Sulfide System

In recent years,a large number of chlorophenols have been used as raw materials or intermediates in various human production activities.Advanced oxidation process based on sulfate radicals(SO₄^?-)is efficient in treating refractory organic pollutants like chlorophenols.In this study,the p-chlorophenol which is a typical chlorophenol compound is taken as the target pollutant.Molybdenum sulfide is added as the co-catalyst in PMS/Fe²⁺system.This study mainly investigated the degradation efficiency of p-chlorophenol and factors influencing efficiency of PMS/Fe²⁺/MoS₂ system,and the characters of co-catalyst was also investigated,and explored the reaction mechanism and degradation path of the system.Main research contents and results are as follows:?1?The efficiency of PMS/Fe²⁺/MoS₂ system was obviously synergistically enhanced on the degradation of 4-CP,and the removal rate can reach 93.2%within 10min.Experiments examines several influencing factors on degradation efficiency of the system,We found the system effct is better in acidic conditions,the optimum dosing concentration of PMS,Fe²⁺and MoS₂ is respectively 160 microns,140 microns and 0.03 g,higher temperature significantly improved the system performance,Cl^-of low concentration restrains the system effect,Cl^-of high concentration promotes the system effect,NO^3-has no obvious effect on the degradation efficiency and NH⁴⁺,HA and substrate of high concentration inhibited system effect,the PMS/Fe²⁺/MoS₂ system can treat different organic micropollutants well which proved it was good for application.?2?A series of characterization analysis were carried out on the co-catalyst MoS₂,and it was found that the crystallinity of MoS₂ was better and the particle size was uniform.After the reaction,MoS₂ produced more crystal structures and agglomerated stacked morphology.The microstructure and chemical state of element composition of?3?MoS₂ were not changed after the reaction.The catalytic activity of MoS₂ is related to the particle size,the smaller the particle size,the stronger the catalytic activity.MoS₂ has good catalytic activity and stability as a co-catalyst.?4?The reaction mechanism and degradation pathway were studied.According to the free radical capture test and EPR results,SO₄^?-is the main active free radical of the system.The reaction mechanism of PMS/Fe²⁺/MoS₂ system is as follows:unsaturated S atom on the surface of MoS₂ captures H⁺in water to form H₂S.After the removal of S atom,Mo⁴⁺on the surface of MoS₂ particles becomes very active,and reacts with Fe³⁺in solution to generate Mo⁶⁺and Fe²⁺,which greatly promotes the circulation of Fe²⁺and Fe³⁺in solution.In the process of reaction,p-chlorophenol is firstly oxidized into aromatic compounds?p-benzoquinone,hydroquinone,and chloro-catechol?,followed by epoxidation to aliphatic compounds,and finally oxidized into small molecular compounds such as acetic acid,CO₂,and H₂O.