Study On Transport Behavior And Adsorption Properties Of Micro-nano-scale Biochar

Biochar is a kind of carbon material with high carbon content produced by pyrolysis of biomass raw materials such as waste weeds,sawdust,straw and rice husk in anoxic condition.It can be used for soil and water remediation,carbon sequestration,emission reduction,soil improvement and crop yield growth.In recent years,researchers at home and abroad have paid attention to it.Previous studies have found that different particle sizes have different effects on the migration and adsorption behavior of biochars,but these studies have not gone deep into the micro-nano-scale biochars.However,studies have found that the properties of micro-nano-scale biochars are different from those of ordinary biochars,which will affect their migration and adsorption behavior and lead to potential environmental risks.In this paper,the migration and adsorption behavior of micro-and nano-scale biochars under different environmental conditions will be emphatically studied.At the same time,considering that in the actual water and soil environment,biochar will be subjected to supergene geochemical action,which will lead to changes in its original element content,pore characteristics,CEC,surface functional group composition and other properties,thus affecting the actual use of biochar.Based on this,the effect of aging on the physical and chemical properties of micro-nano biochar was investigated using 5%H₂O₂ as oxidant,and the effect of aging on the adsorption properties of micro-nano biochar was further demonstrated by atrazine adsorption experiments.In this paper,the effects of natural organic matter and different pH environments on the transport behavior of micro-nano-biochar were studied through the quartz sand column transport experiment.The results showed that humic acid?HA,a model NOM?enhanced the mobility of nanobiochar,and neutral or alkaline aqueous medium favored nanobiochar transport.One reason is that the dispersibility of nanobiochar was improved.The other is due to net negative charge of biochar and quartz particles increased in the presence of HA and alkaline environment.So,the Zeta potential of particles increased and electrostatic repulsion force strengthened,which was beneficial to the transport of nanobiochar.Through the isothermal adsorption experiment of atrazine,the difference between ordinary particle size biochar and micro-nano-biochar in the adsorption of atrazine was studied.With the decrease of particle size,the amount of atrazine adsorbed increased.However,micro-nano-scale biochar exhibits abnormal behavior,which may be related to ash content.Further considering the aging effect,it was found that the aging process would change the physical and chemical properties and adsorption properties of micro-and nano-scale biochars.After aging,the oxygen functional groups on the surface of low-temperature biochar increased,and the adsorption of atrazine increased.After aging,the surface hydrophobicity of high-temperature biochar decreased,and the adsorption of atrazine decreased.The results are of great significance for understanding the migration,adsorption behavior and potential risks of micro-nano-scale biochar under long-term environmental effects.