Adsorption Properties Of Typical Hemp Biochar On Cadmium Ions And Its Application

Two typical hemp species were selected:the stem,leaf and skin of ramie and red hemp were processed into biochar,the effect and influencing factors of the adsorption removal of Cd²⁺in the water body were studied using static adsorption batch experiments,the adsorption mechanism was studied using two adsorption equilibrium models（Langmuir,Freundlich）and quasi-primary and quasi-secondary kinetic models,and the adsorption mechanism was analyzed by BET,XPS and other characterization methods.At the same time,dynamic adsorption experiments and potting experiments were designed to simulate the removal and passivation effect of Cd from biochar with the best adsorption potential in practical engineering and agricultural applications.The main experimental results are as follows:（1）Six kinds of ramie and red hemp biochar have shown a good adsorption effect on Cd²⁺in water,the larger the amount of biochar,the higher the adsorption efficiency,the higher the pH of the initial solution,the higher the adsorption efficiency,of which the adsorption performance of ramie leaf biochar is the best,and the theoretical maximum adsorption amount is 133.05mg·g^-1.All six biochars are more in line with the Langmuir isothermal adsorption model,and their adsorption processes all conform to the quasi-secondary kinetic equations.（2）Dynamic experimental results show that when controlling other conditions,the penetration time of ramie leaf biochar,coconut shell charcoal and oblique zeolite is inversely proportional to the initial concentration of the solution and the inlet water flow rate,respectively,and the effluent concentration is inversely proportional to the height of the water outlet of the adsorption column.The adsorption effect of the three materials in the dynamic test is:ramie leaf biochar>coconut shell charcoalt>oblique zeolite.（3）Potting experiment results show that the application of ramie leaf biochar to Cd-contaminated acidic soil can increase soil pH,reduce soil Eh,reduce weak acid soluble Cd,increase residue Cd,reduce rice accumulation of Cd,and increase rice yield.Among them,the applied amount of ramie leaf biochar combined with flooding treatment can make the Cd content in morning and evening rice brown rice lower than the national food safety limit.