Study On The Efficacy And Mechanism Of Organic Pollutant Removal By Maleic Acid Activated Persulfate

In recent years,advanced oxidation technology based on sulfate radicals has attracted attention in wastewater treatment because of its outstanding advantages of high efficiency and stability.However,the common activation methods of persulfate mostly focus on energy input and catalyst introduction,which have problems such as high application costs and difficulties in catalyst recovery,limiting the application of this technology in practical water treatment processes.It was shown that the activation pathway of persulfate was enriched by using simple organic substances as promoters or metal complexing agents.In order to further expand the related research ideas,this paper finally constructed an oxidation system of maleic acid/persulfate（MA/PS）without the addition of catalysts and the introduction of energy consumption by screening and discriminating different organic substances,and evaluated the effectiveness of the system in combination with the degradation effect of the target pollutants,revealing that the reaction mechanism of maleic acid activated persulfate was evaluated,and its practical application potential was investigated.The main research contents and conclusions of the paper are as follows:（1）By screening different organic activators,a maleic acid/persulfate oxidation system was constructed to investigate the degradation efficiency of rhodamine B,a common organic dye,as the target.The results showed that the degradation rate of rhodamine B was 81.5%and the final decomposition rate of persulfate was 14.6%after4 hours.The degradation rate and the removal rate of total organic carbon were 1.743 h^-1and 61.3%,respectively,which were 9 times and 4.9 times higher than those of single persulfate oxidation system.Meanwhile,the effects of different reaction parameters,such as the initial concentration of maleic acid,the dosing amount of persulfate,the initial p H of the solution and the reaction temperature,on the degradation efficiency of the pollutants were investigated,and the system degraded pollutants best under acidic p H conditions when the amounts of persulfate and maleic acid were 4 mmol/L and 10mmol/L,respectively.（2）The mechanism of pollutant degradation in the oxidation system of maleic acid/persulfate was revealed by combining the quenching experiments of active oxidizing substances,electron spin resonance spectroscopy analysis and organic functional group substitution experiments of maleic acid activator.The results showed that the rhodamine B degradation process involves both radical and nonradical pathways under the peroxynitrite activation of maleic acid.In order to investigate the effective groups of the activated persulfate molecule,the organic N-methylmaleic acid monoamide,cis-2-butene-1,4-diol and butanedioic acid,which replaced the functional groups at different positions,were used as activators to activate the persulfate to degrade rhodamine B.The results showed that the butanedioic acid/persulfate system without C=C inhibited the degradation of rhodamine B.The cis-2-butene-1,4-diol/persulfate system without COOH did not promote the degradation of rhodamine B.C=C and COOH in the maleic acid were the effective groups for activating the persulfate.It is proposed that persulfate acquires electrons to generate SO₄·^-under the nucleophilic attack of maleic acid,and a series of reactive oxidizing substances,mainly·OH,·O₂^-and ¹O₂,supplemented by a small amount of SO₄·^-,are produced during the reaction,and rhodamine B is subjected to Rhodamine B undergoes structure destruction under the continuous action of active oxidation substances,and is finally mineralized to CO₂and H₂O.（3）The anti-interference ability and application potential of the maleic acid/persulfate oxidation system were examined.Firstly,the effects of inorganic anions and natural organic matter in the natural water background were examined,and the results of the study showed that the effects of NO₃^-and Cl^-were negligible;SO₄^2-,humic acid and kaolin were only slightly inhibited.Therefore,the system has good anti-interference ability to the actual water environment factors.In addition,the degradation results of other organic dyes showed that the reaction endpoint eosin Y degradation rate reached 70.9%,and the degradation rate of methyl orange,methylene blue and alizarin green all reached more than 60%,and the system has further research significance for the removal of organic dyes.The practical application potential of the system was investigated by introducing secondary effluent from municipal wastewater plants and campus landscape water.Combined with 3D fluorometric analysis,the reaction effectively degraded aromatic protein,fulvic acid and tryptophan organic pollutants in the actual wastewater in 4 hours.This study provides a method to activate persulfate with simple organic matter,which provides a new idea to improve and develop an efficient and low-consumption technique to activate persulfate.