Study On Thermodynamic Adsorption Of Oxytetracycline On Biochar And Soil Water-holding Capacity Under Biochar Amendment

Biochar is an attractive material derived from biomass under pyrolysis in limited oxygen atmosphere.As an alternative way,pyrolysis of wastes instead of combustion could decrease CO2 emissions inhalable particles and organic compounds.With large specific surface area and surface functional groups,biochar is now used as economic adsorbent to remediate polluted soil and water.The abuse of antibiotics led to the residues were widely distributed in soil and water,resulting in environmental issues.Therefore,researchers focus on the adsorption of antibiotics on biochar.Meanwhile,biochar is also regarded as an effective and low-cost soil amendment,which can increase the yield of crops.The experiments were conducted to explore antibiotics adsorption on biochar and the effect of biochar amendment on soil water-holding capacity.The following three aspects were included in this study.(1)The effect of pyrolysis temperatures on biochar adsorption performance was evaluated by sorption thermodynamics of oxytetracycline(OTC)on maize straw derived biochar.(2)The effect of biochar and clay minerals interaction on OTC adsorption was investigated by isothermal sorption of OTC on biochar-clay mixtures under 90 days incubation.(3)The effect of added biochar on the water-holding capacity of soil was determined in bench scale laboratory.The effect of biochar feedstock and dosage on crop yield was assessed in an agricultural site located in Hebei Province.The results showed as follows.(1)The adsorption of OTC on biochar prepared at different pyrolysis temperatures was a spontaneous and endothermic process.Biochar pyrolyzed at 600 ?performed better adsorption,due to surface functional groups change under higher temperature.(2)The adsorption capacity of biochar-clay mixture increased with the incubation time,and biochar addition improved the adsorption capacity compared with the pure clay mineral.Different ions presented various effects on OTC adsorpltion to biochar-clay mixture.Ca2+ had little impact on the adsorption while Fe3+ decreased the amount of adsorbed OTC.(3)Biochar enhanced the water-holding capacity of soil.The biochar amendment showed a positive effect on crops yield which depend on biochar types and dosages and crop species.Further experiments conducted in lab suggested that biochar addition did not impact the characteristics of soil such as CEC,elements concentration and so on.Therefore,we suggested the crop yield is increased by enhancing the soil water-holding capacity through biochar addition.