Adsorption Properties And Mechanisms Of Corn Stover Biochar On Three Different PPCPs

Pharmaceuticals and personal care products(PPCPs)are continuously detected in a variety of environmental media,which has a great potential harm to the ecological environment and human health.Also,the biggest number of burned or discarded straw in China leads to severe air pollution.Therefore,avoiding pollution and the utilization of waste materials are the key to solve these problems.In this study,biochar prepared from com straw in Guanzhong Area of Shaanxi Province,was used as the adsorbents.Three different PPCPs,clofibric acid(CA),sulfamerazine(SMZ)and paracetamol(PRCT)were selected as adsorbates.In order to solve the problem of PPCPs pollution in the aquatic environment,we designed experiments on material preparation,characterization,isothermal adsorption and competitive adsorption to explore the adsorption mechanism of different PPCPs on corn straw biochar prepared at different temperatures,and provide a certain theoretical basis for the practical application of straw biochar to remove PPCPs from the polluted water.Previous studies showed that charge-assisted hydrogen bond(CAHB)played a key role in adsorption of ionizable organic pollutants on carbon based materials.Therefore,this study mainly focused on the important role of CAHB in biochar removal of different PPCPs pollutants from water environment,and the main research results are as follows:1.The physical and chemical properties of the biochars were measured and analyzed:the BET specific surface area of BCs-300 and BCs-600 was 25.55 m2/g and 98.94 m2/g,respectively.There were more micropores and mesopores for BCs-600.Elemental composition and FTIR spectra showed that there were some oxygen-containing functional groups on BCs-300 and BCs-600 surface,such as-OH,-COOH,and C=O.The buffering range of BCs-300 and BCs-600 was pH 4.0?11.0 and pH 4.0?10.0,respectively.The PZC of BCs-300 and BCs-600 was about 7.2 and 9.8.2.The kinetic curve accorded with the quasi-second-order kinetic model,indicating that the adsorption rate was controlled by the chemical adsorption process.Freundlich,Langmuir,and Dubinin-Radushkevich models were all fitted well with isothermal adsorption data(r2>0.9600).However,the fitting results of the Freundlich model(r2=0.9869?0.9994)was better than the Langmuir model(r2=0.9685?0.9983),indicating that the adsorption of the three PPCPs on two BCs was non-monolayer adsorption,the adsorption free energy was calculated through Dubinin-Radushkevich model,and it was found that the adsorption was the result of both physical adsorption and chemical adsorption.3.After normalization of the specific surface area,the order of the adsorption amount of the three PPCPs on BCs-300 was SMZ>PRCT>CA,and on BCs-600 was PRCT>SMZ?CA.The results showed that the stronger CAHB resulted in the better adsorption.The FTIR spectra of before and after the adsorption of three PPCPs on two BCs revealed the CAHB formation mechanism.And desorption hysteresis phenomenon further confirmed that CAHB was the main reason for the difference of adsorption of three PPCPs on two BCs.The results of specific surface area normalization showed that the adsorption amount of CA?SMZ and PRCT on BCs-300 was all higher than that on BCs-600,which was mainly caused by the presence of more oxygen-containing functional groups on the surface of BCs-300.4.Coadsorption experiments were also conducted and the results showed that:1)When BCs-300 was used as the adsorbent,the coexistence of SMZ increased the adsorption of CA,while the coexisting PRCT decreased the adsorption of CA;the co-existing CA or PRCT presented synergistic effect on SMZ adsorption;the coexistence of CA increased the adsorption of PRCT,but the coexistence of SMZ did not significantly affect the adsorption of PRCT.2)When BCs-600 was used as the adsorbent,the coexistence of SMZ inhibited the adsorption of CA,while the coexistence of PRCT had no obvious influence on the adsorption of CA;the co-existing CA and PRCT showed synergistic effect on SMZ adsorption;the coexistence of CA and SMZ did not affect the adsorption of PRCT.These results emphasize that the environmental behaviors of a certain pollutant should be assessed carefully by considering the presence of other different types of pollutants.