Degradation Efficiency And Mechanism Of Orange Ⅱ With Inorganic Alkaline Buffer Solutions-activated Peroxymonosulfate

In recent years,advanced oxidation technology based on peroxymonosulfate（PMS）activation has attracted much attention result from it can generate active species with highly oxidizing ability.Base-activated PMS is a new type of activation method.This method can use the alkalinity of alkaline wastewater itself to activate PMS to degrade organic pollutant in wastewater.Therefore,it is necessary to establish a method that can improve base-activated PMS to degrade organic pollutants under medium-alkaline conditions.The common dyes Orange II（AO7）was used as a model pollutant.Several new green persulfate activation methods with several inorganic anions（carbonate ion,borate ion,and phosphate ion）as activators were proposed.The kinetics of the degradation of these pollutants,influence factors and preliminary reaction mechanism were also investigated.Firstly,the effectiveness and mechanism of carbonate buffer solution activated PMS system to degrade AO7 were investigated.The research results indicated that the carbonate buffer solution activated PMS to degrade 91.2%of AO7 in 30 min.Meanwhile,the degradation of AO7 in carbonate buffer solution activated PMS system was fitted for the pseudo-first-order kinetic model.The radical quenching experiments demonstrated that both singlet oxygen（¹O₂）and superoxide anion radical(O₂^·-)would coexist at pH 9.0.Secondly,this study found that borate buffer solution could enhance the activation performance of base/PMS system.The removal of AO7 was more 80%in 30 min in borate buffer solution activated PMS when pH>9.0.The degradation of AO7 increased with increasing of PMS concentration(0-2 mmol·L^-1)and temperature（15-35⁰C）.Besides ¹O₂ and O₂^·-,sulfate radicals(SO₄^·-)also coexist in borate buffer solution activated PMS system.UV-Vis scan analysis showed that AO7 was not only bleached but also mineralized by the destroying of functional groups in ultraviolet and visible ranges.Finally,the effectiveness and mechanism of phosphate buffer solution activated PMS degradation of AO7 were investigated.A complete degradation of AO7 was observed within 3 min in 0.1 M phosphate buffer solution.And the corresponding pseudo-first-order rate constants(k_obs)was 0.03895 s^-1.The radical quenching experiments demonstrated that under weak alkaline conditions（pH<9.0）,the active species were SO4^·-,and under strong alkaline conditions（pH>9.0）,the active species were hydroxyl radicals（·OH）,¹O₂ and O₂^·-.In order to evaluate the ability of phosphate buffer solution activated PMS in degrading refractory contaminants,chlorophenols were selected for degradation.These facts suggested that the phosphate buffer solution activated PMS system had an extensive degradation ability.In addition,the removal rate of total organic carbon（TOC）was measured,and it was found that AO7 was oxidized while being mineralized.Phosphorus,which is a harmful pollutant that is harmful to water,could be precipitated and removed by adding calcium chloride.