Study On The Solidification Mechanism Of Biochar On Acetochlor In Soil Environment

Acetochlor is an amide pre-emergent herbicide,which has been widely used in agricultural production.However,due to its difficult-to-degrade and easy-to-enrich characteristics,it has caused great pollution to the soil environment.There are several ways to remove acetochlor remaining in the soil: hydrolysis,photodegradation,microbial degradation and adsorption.Among them,the adsorption method has received more attention due to its simple operation and better removal effect.Among the many adsorption materials,biochar has the advantages of wide sources,low price and good adsorption effect,etc.It is widely used in the related research of solidifying soil pollutants.Therefore,this study used cow dung,corn cobs,and ash wood chips as raw materials for the preparation of biochar,and further explored its solidification properties for acetochlor in the soil.(1)This article conducts related research based on acetochlor as a representative pollutant.First,the adsorption performance of three soils(Harbin Northeast Agricultural University campus soil,Zhaodong soil and Bei’an soil)were studied.Secondly,the adsorption performance of cow dung biochar(BC-CD),corn cob biochar(BC-CC)and Fraxinus mandshurica biochar(BC-FM)were studied in acetochlor solution.Finally,the biochar with the best adsorption performance(BC-CD)was added to the Bei’an soil with better adsorption performance to explore the solidification performance of the biochar soil to acetochlor under various factors.(2)In this study,the relevant physical and chemical properties of the soil were analyzed,including:p H,organic matter and clay content.At the same time,the biochar used in the experiment was analyzed by scanning electron microscopy,Fourier infrared spectroscopy,aperture and specific surface area,X-ray diffraction,and surface functional group titration.The results show that the pyrolysis method used in this study will make the surface of biochar have abundant spherical,spheroidal and honeycomb structures,and at the same time have a larger specific surface area.(3)The influencing factors selected in the adsorption experiment mainly include: the amount of biochar added,the reaction time,the temperature of the adsorption process,p H,the concentration of salt ions in the adsorption environment,and the addition of different concentrations of citric acid and yellow Humic acid and so on.The results show that the optimum addition amount of BC-CD in the soil of Beian is 2.0%,and its contribution rate is 63.75%.The time for the three soils and the soil with biochar to reach adsorption equilibrium was 24 h,while the adsorption equilibrium time of biochar in the acetochlor solution was 6 h.(4)p H,ionic strength and citric acid have little effect on the adsorption process,and low temperature is more conducive to the adsorption.With the increase of fulvic acid concentration,the solidification rate decreased by 17.92%,which has a greater impact on the solidification of acetochlor in biochar soil.(5)The kinetic model analysis of three soils,three kinds of biochar and biochar soil with an addition amount of 2.0% shows that the fitting results are all pseudo-first-order kinetics in a good fitting state.Simultaneously,the Langmuir and Freundlich isotherm models were fitted,and the maximum adsorption capacities of the three soils were calculated to be 1.32 mg/g(Harbin),1.67 mg/g(Zhaodong)and 1.98 mg/g(Beian).,The maximum adsorption capacity of the three kinds of biochar is 175.44 mg/g(BC-CD),129.87 mg/g(BC-CC)and 116.28 mg/g(BC-FM),and the addition amount is 2.0% of the biochar soil The maximum curing amount is 4.18 mg/g.(6)The main adsorption mechanism of biochar for acetochlor adsorption is hydrophobicity,and hydrogen bonds and π-π interactions also play a certain role in it.In this study,cow dung was used as biomass to pyrolyze and prepare biochar with better adsorption performance.And the solidification performance of acetochlor in the soil was studied.The results show that it has the characteristics of simple preparation,wide sources,fast adsorption rate,and good curing effect.It has great practical application value in the mitigation and restoration of soil pollution problems.