The Adsorption Characteristics Of Biochar And Its Composite Materials To Antibiotics In Water

Antibiotics are widely used in disease prevention and control of poultry and livestock in the breeding process,aquaculture and clinical application,and so on.Poultry and livestock have a bit absorption of antibiotics,and about 60%of the antibiotics will be released to the nature with the excrement of livestock and may have a certain impact on the ecological environment.The treatment methods of antibiotics in the environment include advanced oxidation and adsorption.In this paper,rice straw and cow dung are used as raw materials to prepare for biochar.At the same time,graphene oxide-biochar composite materials are prepared by co-precipitation.Four common antibiotics in water were selected,and the adsorption effect of various types of biochar on antibiotics in water was analyzed and compared through kinetic and thermodynamic experiments.Through the experiments of straw and cow dung biochar,it is concluded that the adsorption performance of rice straw biochar is better than that of cow dung biochar.The adsorption kinetics of rice straw biochar for four antibiotics conforms to the quasi-second-order kinetic equation,and the adsorption process is chemical adsorption.In general,the adsorption capacity of straw biochar for tetracycline antibiotics is higher than the adsorption capacity for sulfonamide antibiotics.The adsorption isotherms of four antibiotics by rice straw biochar conformed to the Freundlich model,which is a heterogeneous multi-layer chemical adsorption;the adsorption isotherms of four antibiotics by the cow dung biochar conformed to the Langmuir model.The calculation results of thermodynamic parameters show that the adsorption process of tetracycline antibiotics on straw biochar and cow dung biochar is a spontaneous process with endothermic and entropy increase;the adsorption process of sulfonamide antibiotics on these two kinds of biochar is exothermic and entropy The process of reduction.The adsorption capacity of the two graphene oxide-biochar composites for the four antibiotics is similar to that before the composite,and the adsorption kinetics conforms to the quasi-second-order kinetic equation,which belongs to chemical adsorption;the adsorption performance of the composite material based on cow dung biochar It is better than the composite material based on rice straw biochar,and the use of graphene oxide to prepare the composite material improves the adsorption performance of rice straw biochar to sulfonamide antibiotics,and the adsorption performance of tetracycline antibiotics has little change;from the overall perspective It improves the adsorption capacity of cow dung biochar.The adsorption of antibiotics on the two graphene oxide composite materials conforms to the Langmuir model.The calculation results of thermodynamic parameters show that the four antibiotics are exothermic and entropy reduction process on graphene oxide-straw biochar;the adsorption process on graphene oxide-cow dung biochar is a spontaneous process of endothermic and entropy increase,The absolute value ofΔG~odecreases as the amount of antibiotic adsorbed increases.Scanning electron microscopy and XRD analysis results show that,compared with biochar prepared from cow dung,biochar prepared from straw has a smoother surface,relatively smaller pores,high content of C element,and stronger surface hydrophilicity.The surface of the composite material is rougher,after the composite,the specific surface area is increased,the number of pores and the content of organic carbon are reduced,and the surface hydrophilicity is also reduced.The crystal grains of the composite material are smaller,and the crystallization effect is relatively better.