Removal Efficiency And Mechanism Of Emerging Contaminants In Water By Modified Biochar Derived From Tropical Plants

Pyrolysis biomass can not only avoid air pollution caused by incineration,but also help achieve“carbon peaking and carbon neutrality”goals.Biochar produced from pyrolysis can be used for the removal of pollutants in the environment.Tetracycline and acesulfame,as two emerging pollutants,have gradually attracted widespread attention due to their environmental hazards.Tetracycline and acesulfame used in production are not fully absorbed by organisms and are finally discharged into the water with metabolites.Tetracycline in environment would induce the production of resistance genes or endanger human health through the food chain,while the continuous accumulation of acesulfame in the environment can potentially harm the ecological environment.Therefore,effective measures should be taken to reduce the content of tetracycline and acesulfame in water,which is of great significance for protecting ecological safety and human health.In this study,biochar obtained from cassava straw,rubber wood and sugarcane bagasse,typical biomass in Hainan region,and further modified biochar was obtained by KOH impregnation or manganese/nitrogen（Mn/N）doping,with a view to investigate:（1）the removal efficiency and mechanism for tetracycline by KOH modified-cassava stalk biochar（MCB）,rubber wood biochar（MRB）and sugarcane bagasse biochar（MSB）;（2）The mechanism and degradation pathway effects of Mn/N-doped biochar（Mn/N-SB）activated potassium monopersulfate triple salt degradation on acesulfame.The main results are as follows:（1）Compared with pristine biochar,the specific surface area of MCB,MRB and MSB increased by 93.6,6.9 and 1.1 times,respectively.The removal efficiency of TC by KOH modified biochar was 3.5 times（MCB）,5.0 times（MRB）and 2.1 times（MSB）higher than that of pristine biochar,respectively.In the TC-Cr（VI）coexisting system,biochar promoted the removal of TC and the reduction of Cr（VI）.The removal mechanism for TC by biochar involved electrostatic adsorption,π-πstacking interaction,hydrogen bonding and pore filling,while the removal mechanism for Cr（VI）included reduction（66.5%）and adsorption（32.9%）.（2）The specific surface area and pore volume of Mn/N-doped biochar（Mn/N-SB）increased by 23.8 and 11.3 times compared with sugarcane bagasse biochar（SB）,respectively.The adsorption efficiency for acesulfame by Mn/N-SB increased by 2.9times than SB,which was primarily attributed to the increased specific surface area and pore volume after Zn Cl₂-induced pore formation.Furthermore,compared with SB,the catalytic degradation efficiency for acesulfame by Mn/N-SB increased by 15.4times,which might be due to the oxidation of singlet oxygen,sulfate radical and hydroxyl radical from the activation of potassium monopersulfate triple salt by the metal manganese and pyrrole nitrogen in Mn/N-SB.