Adsorption-catalytic Ozonation Of Sulfamerazine With Mn-Fe₃O₄/AC In Water

Sulfamerazine（SMZ）is a typical representative of sulfonamide antibiotics.It exists in the water environment for a long time and will cause potential harm to human health and ecosystem.Adsorption technology is considered to be one of the most promising processes for removing SMZ due to its high processing efficiency,low cost and simple operation.However,a single adsorption technology has the disadvantage of frequent analysis.The adsorption-catalytic ozonation process can overcome the above shortcoming,showing great potential in emerging pollutant removal.In this study,the adsorption-catalytic ozonation process was proposed to remove SMZ in water,and magnetic recyclable Mn-Fe₃O₄/AC was selected as the adsorbent/catalyst in the adsorption-catalytic ozonation process.The effects of process parameters on the adsorption-catalytic ozonation of SMZ were investigated,and the mechanism of adsorption-catalytic ozonation was revealed.This research can provide theoretical basis and technical guidance for the research of antibiotic-containing wastewater treatment process.The main research contents and conclusions are as follows:（1）Adsorption-catalytic ozonation removal process and parameter optimization of SMZ.At p H=6.1,the initial concentration of SMZ was 10mg/L,and the material dosage was 0.05 g/L,Mn-Fe₃O₄/AC-10 with Fe:Mn molar ratio of 10:1 prepared by coprecipitation-annealing method had the highest adsorption capacity for SMZ（146.43 mg/g）;In the adsorption-ozone catalytic oxidation process,adsorption and catalytic ozonation increased the removal rate of SMZ to 90.5%,which was 39.7%higher than that of ozonation,of which adsorption may contributed 19.3%of the removal rate.In this process,increasing the dosage of ozone,reducing the p H of the solution and increasing the dosage of materials are beneficial to the removal of SMZ.Ions such as CO₃^2-、PO₄^3-、SO₄^2-and Cl^-and humic acid substances in the water environment can inhibit the removal of SMZ by this process.（2）Study on the mechanism and toxicity level assessment of Mn-Fe₃O₄/AC-10 adsorption-catalytic ozonation of SMZ.SMZ is adsorbed on Mn-Fe₃O₄/AC-10 through electrostatic interaction,π⁺-πdonor-acceptor interaction and hydrogen bond interaction.The adsorption process is spontaneously exothermic,which can be described by the pseudo-second-order adsorption kinetic model and the Langmuir isotherm adsorption model.SMZ is mainly adsorbed on the surface of Mn-Fe₃O₄/AC-10 as a monolayer In the adsorption-catalytic ozonation system,M-OH（M=Fe/Mn）on the surface of the material reacts with ozone molecules to generate various oxygen-containing radicals,such as M-O₂^-·and HO₃·,and HO₃·finally decomposes to generate·OH with stronger oxidizing ability,·OH attacked the aniline amino group,sulfonamide group and pyrimidine heterocycle of SMZ,and finally generated H₂O、CO₂、SO₄^2-and NO₃^-et al.The ECOSAR software model predicted different levels of toxicity of SMZ and degradation products to fish,Daphnia and green algae,with green algae being the most sensitive to the SMZ and degradation products.Among them,substance 2 was the most toxic to fish,daphnia and green algae,with concentrations of 659,000,161,000 and 146,000 mg/L,respectively;substance 4 was the least toxic,with concentrations of 668.75,294.48,and 271.60 mg/L,respectively.Considering the enhanced toxicity of degrading intermediates,it is necessary to eliminate this potential hazard by extending the total mineralization time.