Characterization Of Different Intercalation Modified Biochars And Their Adsorption Characteristics To Atrazine In Water

The accumulation of pesticides in the environment continues to increase as people grow their crops.In order to effectively remove or reduce the pollution of pesticides on soil and water,biochar and modified biochar have gradually become research hotspots.Biochar material is a clean adsorbent with high specific surface area and strong adsorption properties.Layered double hydroxide?LDH?is an anionic clay material that also has a large specific surface area and strong adjustability.This study uses different LDH modified biochar.The three bimetallic LDHs of modified biochar are: Zn/Al-LDH,Ni/Fe-LDH and Mg/Al-LDH.The LDH modified biochar material was prepared by combining biochar and bimetallic/trimetallic LDH by different preparation methods.One method is to first combine the biochar prepared in a nitrogen atmosphere at 600? with the pretreatment liquid of LDH to form a precipitate,and then dry and grind the modified material bimetallic BCL/trimetal BC-LDH.The other method is to use biomass?corn straw powder?/ biochar mixed with LDH pretreatment liquid to form a precipitate,which is dried and then pyrolyzed in a nitrogen atmosphere at 600? to obtain a modified material bimetallic BMLP or trimetallic BC-LDH-P.They were then characterized and studied for their adsorption properties for atrazine.The purpose of this paper is to understand the adsorption properties of intercalated modified biochar for organic pollutants and to find the modified biochar materials with high adsorption properties.The research results are as follows:?1?Biochar,bimetallic layered hydroxide and trimetallic layered hydroxide modified biochar were characterized during the study.The material was characterized by SEM,FT-IR,XRD,XPS,?-potential.The results show that the pore diameter of the modified materials is mainly distributed in the mesoporous region,and the pores are mesopores.The surface particle size of the LDH modified biochar material is significantly smaller than that of the original biochar.And the surface functional groups are significantly changed,CO₃^2-group and the OH-group are increased.The LDH material is well combined with biochar,and the stability of the modified material is improved.?2?The adsorption capacity of bimetal LDH modified biochar to atrazine in water is significantly different between different modified materials.The modified biochar prepared by BMLP pathway has higher adsorption capacity of atrazine than BCL.The order of saturation adsorption of atrazine in path BMLP was BMLP-Z?257.34 mg/g?> BMLP-N?98.42 mg/g?> BMLP-M?92.12 mg/g?> BC?54.05 mg?/g).The p H has little effect on adsorption performance.The adsorption kinetics of the original biochar BC and Mg/Al-LDH accorded with quasi-first-order reaction kinetics model.The Zn/Al-LDH modified biochar and Ni/Fe-LDH modified biochar met the quasi-secondary reaction kinetics model.The adsorption behavior of the original biochar and BCL-M in Mg/Al-LDH modified materials conforms to the Langmuir adsorption isotherm,while the other bimetallic LDH modified biochar conforms to the Freundlich adsorption isotherm.?3?In the study of trimetallic LDH modified biochar materials,trimetallic LDH modified biochar was prepared at a ratio of Ni:Fe:Zn = 2:1:0.5.The Ni/Fe/Zn-LDH modified biochar prepared by the above two methods obtained BC-LDH,BC-LDH-P.The adsorption effect of the atrazine material in the water was compared.The results showed that the order of adsorption capacity was BC-LDH-P>BC-LDH>BC,and the maximum equilibrium adsorption amounts were 123.35 mg/g,105.54 mg/g and 54.05 mg/g,respectively.The adsorption kinetics of Ni/Fe/Zn-LDH modified biochar on atrazine in water accords with quasi-secondary reaction kinetics.The adsorption behavior is consistent with the Freundlich adsorption isotherm.In the mechanism study,CO₃^2-plays an important role in the adsorption process,and the ?-? bond interaction participates in the process of adsorbing atrazine.?4?Ni-Fe and Zn were added to investigate the trimetallic LDH modified biochar.Ni-Fe and Zn were added to investigate the trimetallic LDH modified biochar.Although the results show that the adsorption capacity of tri-metal Ni/Fe/Zn-LDH modified biochar is not as good as that of Zn/AI-LDH modified biochar,it has better adsorption performance than Ni/Fe-LDH modified biochar.It was proved that the addition of Zn has the effect of enhancing the adsorption of atrazine on the material.Therefore,the successful modification of the three-metal Ni/Fe/Zn-LDH modified biochar has certain theoretical significance.