Adsorption Of Atrazine And Lead In Aqueous Solution Onto Biochars Of Different Particle Sizes

With the discharge of factory wastewater in the process of industrialization in China and the irrational application of pesticides in the process of agricultural development,the pollution of organic pollution and heavy metals in water and soil environments is becoming more and more serious,so the handling and disposal of organic pollutants and heavy metal pollutants cannot be ignored.However,there are few studies on the separation of biochar particle size.In this study,five kinds of biochars?200?,400?,500?,600? and 700??were prepared from agricultural waste corn stover as precursors and calculate the sedimentation time according to Stokes' s law,use the sedimentation method to separate the particle size of biochar.To obtain small particle size biochar particles with particle size <2 ?m and large particle size biochar particles of 2-154 ?m,analysis of its structural properties.With atrazine as the representative of organic pollutantsand lead as a representative of heavy metal pollutants,the effects of reaction time and initial concentration of pollutants on the adsorption amount were systematically studied by batch test.The adsorption characteristics of atrazine and Pb²⁺ by different particle sizes of biochar were investigated.The adsorption mechanism of adsorption of atrazine and Pb²⁺on different biochars by scanning electron microscopy,specific surface area and pore size,X-ray diffraction,X-ray photoelectron spectroscopy,infrared spectroscopy and Raman spectroscopy of different particle size biochar materials Briefly explain.The main conclusions are as follows:?1?With the increase of pyrolysis temperature,the yield of small-diameter biochar decreased by 7.07%,and the yield of large-diameter biochar decreased by 21.81%.The yield of bio-charcoal of both sizes decreased.Small particle size biochar has a larger specific surface area?34-35 times that of large particle size biochar?and a more developed microporous structure?7-8 times larger than large particle size biochar?.XPS analysis showed O/C?0.287?and?O + N?/C?0.186?of small particle size biochar materials compared to O/C?0.311?and?O +N?/C?0.210?of large particle size biochar.Large,indicating that the small-diameter biochar samples have enhanced aromatization,hydrophobicity and weak polarity.FTIR analysis of functional groups revealed that small-sized biochar has more oxygen-containing functional groups and has better adsorption properties for pollutants.?2?The adsorption kinetics test results of atrazine on two particle sizes biochar components prepared by diffrent pyrolysis temperatures show that,When the initial concentration of atrazine is 100 mg·L^-1,the adsorption amount of small-sized biochar pyrolysisat 700? materials(139.33 mg·g^-1)is larger than that of large-sized biochar materials(133.44mg·g^-1).The kinetics of atrazine adsorption by various particle size biochars is more consistent with the quasi-secondary kinetic model?R2=0.958-0.998?compared to the first-order kinetic model?R2=0.844-0.991?.The adsorption test of atrazine showed that the Langmuir model?R2>0.848?and the Freundlich model?R2>0.840?both can better fit atrazine in the organism.The Langmuir model has a better fit to the adsorption process on different particle size components of biochar.And the reaction temperature has less influence on the adsorption amount of atrazine,and the application range is wider.At different reaction temperature,the coefficients of adsorption capacity and adsorption strength of small-diameter biochar materials are KF?6.643,9.506,5.242?,which are larger than the big-diameter biochar materials?5.026,9.790,7.082?,indicating that the combination of small particle size biochar and atrazine is higher and the adsorption effect on atrazine is better.?3?The adsorption kinetics test results of Pb²⁺ on two particle sizes biochar components prepared by differen pyrolysis temperatures show that,When the initial concentration of Pb²⁺ is100mg·L^-1,the maximum adsorption capacity of small-diameter biochar materials prepared by pyrolysis at 700?(122.57 mg·g^-1)is greater than the maximum adsorption capacity of large-diameter biochar materials?105.66 mg?.The isothermal adsorptiont data of Pb²⁺ with different particle size biochar showed that the Freundlich model?R2=0.688-0.961?and the Langmuir model?R2=0.865-0.992?can better fit the adsorption data and the Langmuir isotherm adsorption model is proposed.The degree of integration is higher.Chemical adsorption plays a major role.The thermodynamics adsorption of Pb²⁺ showed that the Freundlich model?R2=0.688-0.961?and the Langmuir model?R2=0.865-0.992?can better fit the adsorption data,and the Langmuir isotherm adsorption model is proposed.The degree of integration is higher.It indicates that the adsorption process is dominated by monolayer adsorption,and there is also a multi-molecular adsorption of partial interlayer adsorption.Thermodynamic studies show that the adsorption amount of atrazine on small-sized biochar decreases with the increase of reaction temperature,which is an exothermic reaction.?4?The adsorption mechanism of different sizes of biochar on atrazine in aqueous solution is mainly pore filling.In chemical adsorption,H bond,ion exchange and intermolecular adsorption mainly occur.For Pb²⁺,it is mainly a coordination complex reaction with hydroxyl,carboxyl,H⁺ and other cations on the surface of biochar.