Study On Catalytic Properties And Iron Dissolution Inhibition Of Iron-based Biochar Catalysts

Due to the complex effect between heavy metal and organic pollutant,the heavy metal-organic complex contaminations are difficult to be removed by chemical precipitation,physical adsorption,memb rane separation and other conventional methods.At present,the most widely studied technologies are advanced oxidation processes(AOPs).Especially,the heterogeneous Fenton-like reaction not only has the strong oxidation to target pollutants,but also can reduce the secondary pollution problems of traditional homogeneous fenton reaction.Carbon materials are one of the most hottest heterogeneous catalysts,but the traditional carbon-based catalysts mainly use petrochemical resources as raw materials.Abundant renewable biomass resource in China is a promising catalyst precursor.In this study,lignin was used as raw material to prepare biochar catalysts for Ni-EDTA containing wastewater treatment,and gelatin was used as nitrogen source to improve the catalytic activity and reduce the dissolution of active components.The nickel removal rate and the dissolution of the active components of the catalyst during the reaction were analyzed.The preparation conditions of iron-based lignin biochar catalyst were optimized.The experimental results showed that under the preparation conditions of heating rate of 3 °C/min,pyrolysis time of 1.0 h,pyrolysis temperature of 600 °C,iron nitrate as iron source with the content of 5%,the catalysts exhibited good performances in the heterogeneous Fenton-like reaction.Among the catalytic oxidation systems,the nickel removal rate was 65.36% and the quantity of iron dissolution was 1.01 mg/L.Then we explored nitrogen-doped modification of iron-based lignin biochar catalyst,and the nitrogen element was derived from another biomass material gelatin.The experimental results showed that the catalysts had the best performances in the heterogeneous Fenton-like reaction when the mass ratio of lignin/gelatin was 6:1,the pyrolysis temperature was 1000 °C,the iron nitrate content was 10%.Among the catalytic oxidation systems,the nickel removal rate was 81.80% and the quantity of iron dissolution was 0.33 mg/L.Finally,the effects of vairous reaction conditions were further studi ed on the N-doped iron-based biochar catalyst in heterogeneous Fenton-like reaction.The optimum reaction conditions obtained were as follows: initial p H of 3.0,catalyst dosage of 0.5 g/L,hydrogen peroxide dosage of 100 mmol/L,reaction temperature of 50 °C.The kinetic analysis of the catalytic oxidation reaction was consistent with the first order reaction kinetic equation.In the process of heavy metal complex degradation,the coexisting substances citric acid,tartaric acid and hypophosphoric acid would hinder the reaction,but the chloride ion had no effect on the final nickel removal rate.