Study On Photocatalytic Degradation Of Sulfamethazine In Water By Magnetic ZnO

Sulfamethazine?SM₂?is structurally stable,which easily accumulates in the environment.It is ubiquitous in sewage and poses a serious threat to human health.Traditional sewage treatment technology is difficult to completely remove antibiotics,photo-degradation is an effective way to remove antibiotics from water.Not all catalysts have a significant catalytic effect on the degradation of certain pollutant,so the choice of photocatalysts is crucial.Nano-catalysts have catalytic properties but are difficult to reuse,which increases the cost of sewage treatment and causes environmental pollution.Therefore,it is of great significance to prepare photo-catalysts that can be both highly efficient and recyclable.In this paper,ZnO was selected as the best photocatalyst by experiment and magnetic ZnO was prepared by chemical precipitation method,and the effect of magnetic ZnO on the degradation of sulfamethazine in pure water was investigated.The effect of light source,pH,catalyst concentrations and other factors on the degradation were investigated,optimum conditions of using magnetic ZnO and the properties of magnetic ZnO were studied as well.The conclusions of the study were as follows:1.In this experiment,the best catalysts for photocatalytic degradation of SM₂ were selected from the four photo-catalysts,nano-TiO2,TiO2,ZnO,and CdS.The experimental results show that these four kinds of catalysts can all promote the photocatalytic degradation of SM₂.ZnO works best,followed by CdS,and finally nano-TiO₂.The addition of powdered TiO₂ has little photocatalytic effect on the degradation of SM₂.2.Catalyst which had best photocatalytic degradation of SM₂,was selected from the 9different ratios of magnetic ZnO that prepared for use in the following experiments.The experimental results show that the photocatalytic degradation rate of SM₂ was the highest when magnetic ZnO prepared with Fe³⁺:Fe²⁺was 2:1 and Fe₃O₄:ZnO was 1:2.The photocatalytic degradation rate of SM₂ with magnetic ZnO rising when the increase of ZnO in the magnetic catalyst.3.Without adding catalyst,under the conditions of ZnO,Fe3O4 and magnetic ZnO,the photolysis of SM₂ under the UV lamp conforms the first-order kinetics.Fe₃O₄ inhibits the photolysis of SM₂.With the catalyst ZnO added,the photolysis rate was 2.85 times than it without catalyst.The photolysis rate of the magnetic ZnO catalyst added is 2.50 times than it without catalyst,which indicated that the magnetic ZnO has a good catalytic effect on the photolysis reaction of SM2.4.The photocatalytic degradation reaction of SM₂ conforms to the first-order kinetics under the three light sources of UV lamp,high-pressure mercury lamp,and xenon lamp,and there is a significant difference in photolysis rate.The photolysis rate of SM₂ under the UV lamp is the fastest,followed by high-pressure mercury lamps,and finally xenon lamps is slowest.Under the UV lamp,The photocatalytic degradation rate of magnetic ZnO to SM2 was slightly slower than that of control ZnO.the photolysis rate of ZnO added was slightly faster than that of magnetic ZnO,which was much higher than that without catalyst.5.With the increase of initial concentration,SM₂ degrades rapidly under UV light,regardless of whether or not the catalyst is added.The photolysis rate is affected by the initial concentration,showed a decreasing trend.The larger the initial concentration is,the more obvious difference between magnetic ZnO and ZnO on the degradation efficiency.This shows that magnetic ZnO is suitable for treating low concentrations of antibiotic wastewater.6.With the increase of the catalyst concentration,the photocatalytic degradation of SM₂ of magnetic ZnO and ZnO both showed a trend of increasing first and then decreasing.The highest degradation rate of SM₂ was 90.17%when 5 mg/L ZnO was added,and the SM₂degradation rate was 86.91%,when 5 mg/L ZnO was added,which was 3.26%lower than that of ZnO.Considering the input cost and catalytic effect,the optimal dosage of magnetic ZnO is 5 mg/L.7.The degradation rate of SM₂ was most affected by pH in conditions of UV lamp.The photolysis rate of SM₂ at different pH conditions was pH10>pH9>pH7>pH3>pH5.Considering comprehensively,the optimum pH of the photocatalytic degradation of SM₂with magnetic ZnO is 7.8.Magnetic ZnO recovery and reuse experiments showed that:after 5 times cycles of magnetic ZnO,the catalytic effect of magnetic catalyst on the degradation of SM₂ has a slight decrease.The loss of quality for each recovery is small.9.The saturation magnetization of magnetic ZnO is at 32.62 emu/g.There is no magnetic particle agglomeration during the experiment,and magnetic ZnO has Superparamagnetism,so it is easily separated under the action of an external magnetic field.