The Efficiency And Mechanism Study On Sulfite Activation By Modified Zero-Valent Iron In Removal Of Metronidazole In Water

Metronidazole（MNZ）are widely present in water,and even their trace amounts can negatively impact the ecosystem and human health.Advanced oxidation processes（AOPS）based on persulfate has garnered significant attention from scientific researchers for its capacity to effectively remove a broad spectrum of organic compounds from water.However,the high biological toxicity and cost associated with persulphates have constrained their application in practical settings.Therefore,new attempts to find greener and more cost-effective alternatives are imperative.Recently,sulfite（S（IV））has been widely followed by researchers for its crucial role in eliminating antibiotics from wastewater due to its green,low biological toxicity and low economic cost as a potential alternative to persulfate,but it is limited by low activation efficiency and complex reaction mechanism and there are few related studies.Therefore,in this paper,two modified zero-valent iron（ZVI）materials were synthesized to activate S（IV）to degrade MNZ in water.The system’s reaction parameters conditions and its reaction efficacy were optimized and mechanism were systematically investigated.The main studies are as follows:To enhance the efficiency and recoverability of nano ZVI（nZVI）while addressing issues with its passivation,the nZVI/agar-membrane（nZVI/AM）was constructed through in situ liquid-phase reduction using agar as the substrate.The impact of nZVI loading on its activation for MNZ removal was successfully resolved.A comprehensive set of characterization techniques were employed to meticulously analyze its surface morphology,elemental composition,crystal structure,pore size distribution,and reusability.It also focuses on revealing the mechanism and detoxification effect of MNZ removal by nZVI/AM/S（IV）system from the perspective of active species generation,quantitative analysis and toxicity change pattern.The results showed that the nZVI/AM composite membrane with an area of2.25 cm²（1.5 cm×1.5 cm）was easy to recycle,and the introduction of agar membrane reduced the agglomeration of nZVI,which had good corrosion resistance and stability.nZVI loading of 4 mg/cm²,sodium sulfite dosing of 0.1 g/L and membrane dosage of3 pieces resulted in the highest MNZ degradation efficiency of more than 99%.The nZVI/AM/S（IV）system degraded MNZ with both free radical and non-free radical pathways,and SO₄^·-and ¹O₂ were the main active species leading to MNZ degradation.The nZVI/AM composite membrane has higher storage cost because of the stringent preparation and storage conditions.In contrast,micronZVI（mZVI）is a technically mature and easily stored,albeit with suboptimal reactivity.This paper seeks to present a detailed description of the preparation of micron-scale zero-valent iron-carbon composites（mZVI@C-T）through calcination,with the express purpose of enhancing the reactivity of mZVI.X-ray diffraction,scanning electron microscope and X-ray photoelectron spectroscopy were used to describe and investigate the crystal structure,surface morphology,and elemental composition of mZVI@C-T.Electrochemical studies were also used to examine how carbon affected the corrosion characteristics and catalytic performance of mZVI.It was shown that 81.5%of MNZ could be removed under acidic to neutral conditions with a sodium sulfite dosage of0.1 g/L and a catalyst dosage of 0.2 g/L.Combined with EIS test and Tafel analysis,it was shown that carbon formed microelectrolysis with mZVI,thus promoting the corrosion of mZVI and enhancing the MNZ removal by mZVI activation S（IV）.The mineralization pathway and toxicity changes of MNZ were systematically investigated by the High-performanceance liquid chromatography mass spectrometry and toxicity calculations.In addition,combined with bursting experiments and EPR,it was shown that SO₄·-and·OH were the main active species during the MNZ degradation.Meanwhile,the material has good stabilityThis study created 2 modified ZVI materials with S（IV）activation capabilities.These materials successfully enhanced the catalytic performance of ZVI and removed MNZ from water,offering ideas for the development of environmental functional materials and providing references for the elimination of organic micropollutants.