Visible-light Photocatalytic Degradation Of Aquatic Microcystin-LR With Diatomite Loaded Nano-materials Of N-TiO₂

The outbreak of cyanobacteria bloom releases secondary metabolites microcystins(MCs).Among them,Microcystin-LR has the strongest chronic toxicity and is the most common type of liver toxin,which makes it a serious threat to the safety of potable water.Therefore,it is great significance to study its efficient degradation and mineralization methods.This study utilized diatomite as carrier to prepare for N-TiO2/D photocatalysts by sol-gel method.Firstly,the N-TiO2/D was characterized by SEM,XRD,UV-vis,XPS,FT-IR and BET.And then taking Humic acid(HA)as the degradation object,the visible light photocatalytic performance of the prepared material N-TiO2/D was investigated through the experiments which focus on the influencing factors experiments,and the best photocatalyst was screened out.On this basis,the performance of removal efficiency and oxidation mineralization degree of MC-LR degraded by N-TiO2/D materials of optimum visible light photocatalytic was further investigated,and the influencing factors,degradation kinetics and reaction mechanism had been analyzed.The results showed that:The particle size of nano material of N-TiO2/D photocatalyst prepared by sol-gel method was 10-20 nm with small particle size and good dispersibility,crystal agglomeration was obviously reduced.The load of diatomite significantly increased the absorption threshold value of the visible light region.N-TiO2/D calcined at 350℃,with 8%doping amount of N and loaded by diatomite exhibited the maximum photocatalytic activity.It was used for visible light photocatalysis reaction of HA with initial concentration of 5 mg/L,after 180min the degradation rate got 93.0%.Using aforementioned 8%N-TiO2/D(350℃)as photocatalysis to degrade MC-LR under visible light,the results indicated that when using the optimum dosage of 1 g/L,the degradation rate of MC-LR reached 95.0%.With initial concentration of 1 mg/L and the oxidation mineralization rate was 83.9%after 6h visible light irradiation.The reaction conformed with the pseudo first order kinetic equation,and the degradation rate constant was 0.4533 h-1.It demonstrated that 8%N-TiO2/D(350℃)was a new method for high efficiency degradation of mineralized MC-LR under visible light,which can provide technical support for the treatment of raw water contaminated by MC-LR.