The Preparation Of Modified Biochar And Its Removal Of Organic Pollutants

With the rapid development of industry and agriculture,the harm of organic pollutants in water to the environment is more and more serious,and there is a great threat to human health.Biochar,as a new environmental functional material,plays an important role in the remediation of soil and water pollution.Nonmetallic modification can improve the adsorption and catalytic degradation of biochar,and improve its own limitations.Therefore,this paper optimized the preparation of nitrogen sulfur co-doped biochar,applied to the removal of organic pollutants in water,and achieved remarkable results.It shows that nitrogen sulfur co-doping modification can provide a green,effective,economic and environmental protection material for the removal of organic pollutants in water.The main research is as follows:1.Biochar was prepared from peanut shell by pyrolysis at high temperature.The biochar was directly calcined by mixing thiourea and biochar.Nitrogen and sulfur atoms were introduced into biochar at the same time to prepare nitrogen sulfur co-doped biochar.BBD model was used to design the experiment,three factors and three levels response surface optimization method was used to optimize the preparation conditions of nitrogen sulfur co-doped biochar with DEP removal efficiency as the response value.The pyrolysis temperature,particle size and the mass ratio of thiourea/biochar were optimized.The results show that the best preparation conditions for DEP removal are:pyrolysis temperature is 375℃,particle size is 300 mesh,thiourea/biochar mass ratio is0.1.The dopant ratio has the most significant effect on DEP removal,followed by pyrolysis temperature.2.The results of DEP removal by nitrogen and sulfur co-doped biochar（NS-B）show that the adsorption kinetics of NS-B is more in line with the second-order adsorption kinetics,and the adsorption process belongs to chemical adsorption.The adsorption of DEP by NS-B is more in accordance with Freundlich model,and the maximum adsorption capacity is 14.34 mg g^-1.Through further study on the adsorption mechanism,it can be seen that after doping nitrogen and sulfur,more adsorption sites will be added,so as to improve the adsorption of DEP.In the adsorption process,the role of nitrogen and sulfur is synergistic,and the main role of the adsorption process is pyridine nitrogen and oxidized sulfur.The results show that the DEP removal efficiency of NS-B is still about 80%,which shows that the modified material has good stability and reusability.Through the preliminary exploration of PS activation,the biochar co-doped with nitrogen and sulfur has the potential of PS activation.3.The porous biochar NS-B_-KOH was prepared by doped with nitrogen and sulfur after KOH treatment.Through BET,SEM,FTIR and XPS characterization analysis,NS-B_-KOH contained a large number of micropores,with a specific surface area of 1214.25 m²g^-1,containing hydroxyl,carboxyl,carbonyl and other functional groups.The content of nitrogen and sulfur in biochar increased significantly after the introduction of nitrogen and sulfur.When the amount of catalyst is 0.1mg L^-1,the degradation efficiency of NS-B_-KOH to sulfamethoxazole（SMX）is up to 30%,which is 15 times of the biochar.After adding PS,the final degradation efficiency is up to 64%,indicating that NS-B_-KOH has a good activation effect on PS.This is due to the functional groups and active sites formed after nitrogen and sulfur doping,the presence of a large number of sp² hybrid carbon and the introduction of nitrogen and sulfur can enhance the electron transfer,so NS-B_-KOH can efficiently and rapidly degrade SMX.The increase of NS-B_-KOH can promote the degradation of SMX.The amount of PS had little effect on the degradation of SMX,and the best value was 0.1 g L^-1.When the initial concentration of SMX is 20mg L^-1,the removal efficiency and removal amount of SMX are relatively high.In addition,NS-B_-KOH has a better degradation effect on SMX in acidic condition.While in neutral and weak alkaline condition,it is beneficial to the activation of PS by NS-B_-KOH.Through the free radical capture experiment and EPR test,it can be further proved that the main active substance is·OH of NS-B_-KOH in degradation of SMX.