Research On The Adsorption Properties Of New Type Chitosan-biochar Microsphere Environmental Protection Materials To Dyes And Heavy Metals

In this study,a new type of adsorption material（CSB）was prepared by compounding biochar and chitosan,which applied to adsorb Cr（Ⅵ）and Acid Red 18 form wastewater.The surface characteristics and morphology,change of functional groups,molecular or atomic structure and specific surface area of CSB were investigated by SEM,XRD,FTIR and nitrogen desorption experiment.At the same time,the influence of five factors,namely the dosage of adsorbents,the initial concentration of solution（C₀）,pH value,time（T）and temperature（K）,on the adsorption effect was also studied.Kinetic model（Pseudo-first order equation,Pseudo-second order equation,Particle diffusion equation）,thermodynamic models and adsorption isotherms models（Langmuir,Freundlich,Dubinin-Radushkevich model）were used explore the adsorption mechanism of CSB.The main conclusions obtained through the above analysis were as follows:（1）The adsorption efficiency of CSB to Cr（Ⅵ）was compared with chitosan microspheres and biochar,indicating that CSB has the best removal efficiency for Cr（Ⅵ）.The surface characteristics of CSB were investigated by SEM,XRD,FTIR and nitrogen desorption experiment,indicate that The pore structure of CSB was not smooth and very rough,and the pore diameter was complex and irregular.The specific surface area of CSB was 38.053 m²/g.Compared with the chitosan microsphere,the specific surface area of the CSB increased significantly,the average pore diameter of CSB was 9.997nm.CSB has the largest pore diameter.The pore diameter of CSB was mostly in the range of 2-20nm.Most of them were mesoporous,and a few of them were micropore and macropore,which constitute a typical hybrid structure.In conclusion,these structures were very beneficial to improve the adsorption performance of CSB.（2）CSB was used to study the adsorption effect of Cr（Ⅵ）ions and Acid Red 18.In the weakly acidic environment,CSB adsorption was more favorable.When the pH value was 3,the equilibrium removal rate of CSB on Cr（Ⅵ）ions and Acid Red 18 was 93.41%and 98.72%,respectively.Considering the two aspects of saving and removal efficiency of CSB,When the initial concentrations of Cr（Ⅵ）ions and Acid Red 18 were 30mg/L and 80mg/L respectively,the optimal dosage of CSB was 2g and 1g respectively,and the removal rate was 94.47%and 97.83%respectively.（3）The adsorption mechanism of CSB was studied by kinetic model,thermodynamic models and adsorption isotherms model.Langmuir equation and pseudo second-order kinetic equation can well describe the adsorption process of CSB on Cr（Ⅵ）ion and Acid Red 18,which indicates that the main factors affecting the adsorption process was chemical adsorption mechanism,rather than particle internal mass transfer,and the two adsorption processes mainly focus on monolayer adsorption.Thermodynamic study indicated that the adsorption course of CSB on Cr（Ⅵ）ion was spontaneous,endothermic and irreversible.