Study On The Efficiency Of Iron Sulfide-based Nanomaterials In Enhancing The Degradation Of Organic Pollutants In Reduction And Oxidation Reaction Systems

As we all know,the groundwater environment on which we depend to survive has deteriorated sharply in the process of advancing the rapid development of industry.Trichloroethylene（TCE）and Sulfamethazine（SMT）are widely used in the fields of organic synthesis,fuel manufacturing,pesticide production and aquaculture.They are two typical pollutants that are difficult to degrade,have a high detection rate and strong toxicity in the environment.At the same time,long-term exposure to this environment may cause great harm to human body.Therefore,In response to the pollution of TCE and SMT,the development of new heterogeneous catalysts with stable catalytic activity to prevent secondary pollution plays a vital role in large-scale actual wastewater treatment.In recent years,more and more scientists are keen to explore efficient and green water pollution control technologies.At the same time,sulfurized iron-based nanomaterials have attracted widespread attention due to their excellent properties（iron is a relatively abundant transition metal element in nature）,providing new ideas for the current environmental remediation field.Therefore,this article uses environmentally friendly sulfurized iron-based nanomaterials for the reduction/oxidation reaction system to remove persistent organic pollutants in water.In addition,according to the characteristics of these two typical nanoparticles,the influence of various influencing factors of the reaction process,the pathway of catalytic oxidant,the contribution of different free radicals to degrade pollutants,and the mechanism of pollutant degradation are deeply studied.The specific content of this paper is divided into the following two parts:Part one:This study surveyed the practicability and mechanism of sulfide-modified nanoscale zero-valent iron supported on biochar（S-n ZVI@BC）for the removal of TCE in the scenario of groundwater remediation.The effects of some critical factors,including pyrolysis temperature of biochar,the mass ratio of S-n ZVI to BC,initial p H,typical groundwater compositions,co-contaminants,and particle aging time,on the TCE removal were examined.The results revealed that the different pyrolysis temperatures could change the physicochemical properties of BC,which influenced the TCE adsorption and degradation by S-n ZVI@BC.In addition,S-n ZVI@BC with a mass ratio of 3:1 showed better pollutant removal performance than S-n ZVI@BC with a mass ratio of 1:1 and 1:3.The total removal of TCE was not significantly influenced by the initial p H（3.0–9.0）,but the degradation of TCE was enhanced at higher p H.Notably,the typical anions(SO₄^2-,HCO₃^-,and HPO₄^2-),humic acid,and co-contaminants（Cr（VI）and NO₃^-）in groundwater all slightly influenced the total removal of TCE,but markedly inhibited its degradation.Additionally,after exposure to air over different times（5 days,10 days,20 days,and 30 days）,the reactivity of S-n ZVI@BC composites was apparently decreased due to surface passivation.Nevertheless,the aged S-n ZVI@BC composites still maintained relatively high removal and degradation of TCE when the reaction time prolonged.Overall,the results showed that the S-n ZVI@BC,combining the high adsorption capacity of BC and the high reductive capacity of S-n ZVI,had a much better performance than the single S-n ZVI or BC,suggesting that S-n ZVI@BC is one promising material for the remediation of TCE-contaminated groundwater.Part two:The second part:In addition to artificial vulcanized nanomaterials,there are many vulcanized iron-based nanomaterials in nature,which have an important impact on the migration and transformation of pollutants in water.Therefore,we developed a simple solvothermal method to synthesize pure phase Fe₃S₄ nanoparticles（NPs）with a 3D flower-like structure,and studied its effect as a heterogeneous catalyst to activate persulfate to degrade SMT.The structure and composition changes of Fe₃S₄ NPs were also studied by scanning electron microscope and X-ray photoelectron spectroscopy.The results show that Fe₃S₄ nanospheres have the best catalytic activity,and the application range of p H is also wider.Under different p H conditions,the leaching rate of metal ions is lower.At the same time,the combination of ESR,chemical molecular probes and ROS quenching experiments further clarified the potential mechanism of Fe₃S₄ NPs degrading pollutants.SO₄·^-、·OH、O₂·^-和¹O₂were determined to be produced in the catalytic process,Among them,SO₄·^-and ¹O₂are proven to be the main reactive oxygen species（ROSs）for the degradation of organic matter.In addition,the reduced sulfur species on the surface of the nanoparticles can enhance the Fe（III）/Fe（II）redox cycle in the process of activating PS by metal sulfides,thereby promoting the decomposition of oxidants to generate more ROSs to improve the degradation efficiency of SMT.The above findings indicate that the excellent catalytic performance of Fe₃S₄ nanoparticles will help to enhance the practical application of sulfurized iron-based nanomaterials in Fenton-like wastewater.