Study On Removal Of Imidacloprid By Tobacco Stalk Based Biochar

Imidacloprid（IMI）,a typical neonicotinoid insecticide,is widely used in the control of plant diseases and insect pests.However,in the process of large-scale use,it enters the water environmental,causing toxicity to non-target organisms,and endangering human health.Therefore,effective removal of IMI from water has become the focus of attention.Adsorption is an effective method for removing organic pollutants from water.Biochar has a large specific surface area and porosity,making it an ideal adsorption material.The raw materials used to prepare biochar affect its adsorption performance.Guizhou Province is one of the main production areas for flue-cured tobacco cultivation in China,generating a large number of waste tobacco stalks every year.Based on this,this paper mainly prepared tobacco stalk biochar and manganese modified tobacco stem biochar using local waste tobacco stalks as raw materials,and carried out research on the adsorption and removal of IMI.Characterization of tobacco stalk based biochar using SEM,BET,FTIR,XRD,and XPS.The effects of the dosage of tobacco stalk based biochar,the initial concentration of IMI,the initial p H value of the solution,and coexisting anions on the adsorption of IMI were investigated.Combining the characterization results and adsorption experiments such as kinetics,isotherms,and thermodynamics,the adsorption mechanism of IMI on tobacco stalk based biochar was analyzed.The main research results obtained are as follows:1.Study on the performance and mechanism of IMI adsorption by tobacco stalk biochar:With the increase of pyrolysis temperature,the degree of aromatization of tobacco straw biochar increased,the pore structure became richer,and the specific surface area significantly increased.Tobacco stalk biochar（BC900）prepared at 900℃has the best adsorption performance,with a removal rate of 92.1%for IMI and a balanced adsorption capacity of 46.01 mg/g for BC900.According to the characterization results of FTIR and XPS,BC900 contains oxygen containing functional groups such as-OH,C-O,and C=O,providing sites for the adsorption of IMI.The adsorption of IMI by BC900 conforms to a pseudo second order kinetic model,and the adsorption isotherm conforms to the Freundlich model.It is a multi-layer chemical adsorption that occurs on a uniform surface.HCO₃^-has the most significant inhibitory effect on adsorption,followed by SO₄^2-,and Cl^-and NO₃^-have a smaller impact on adsorption.The adsorption of IMI by BC900 is a spontaneous and endothermic process.2.Study on adsorption of IMI by modified tobacco stalk biochar:Compared with BC900,manganese modified tobacco straw biochar（MBC900）has a reduced specific surface area and pore volume,but an increase in the types of functional groups and the presence of C≡C and Mn-O bonds.Under the same experimental conditions,the IMI removal rate of MBC900 is 100%,and the equilibrium adsorption capacity is1.08 times that of BC900.Like BC900,the adsorption of IMI by MBC900 conforms to the Freundlich model,but its adsorption kinetics conform to the Elovich model,which is a multi-layer chemical adsorption that occurs on uneven surfaces.The adsorption is a spontaneous and endothermic process.HCO₃^-has the most significant inhibitory effect on adsorption,followed by SO₄^2-,and Cl^-and NO₃^-have a smaller impact on adsorption.Although the law is the same as that of water anions affecting BC900’s adsorption of IMI,overall,MBC900 has a stronger resistance to water substrates.In addition to surface adsorption,pore filling,π-πelectron donor interaction,and hydrogen bonding,the complexation between Mn-O bonds and IMI is also an important mechanism for MBC900 to adsorb IMI in solution.MBC900 also has high stability in adsorbing IMI.