Abstract: Biochar produced via pyrolysis of housedhold biowaste was used as an adsorbent in an experiment to study kinetics and thermodynamics of its adsorption of Cd²⁺ in solution and to explore effects of incubation time,initial Cd²⁺ cocentration,adsorbent dosage,solution pH as well as particle size of biochar on its Cd²⁺ adsorption rate with the equilibrium adsorption method.Results show that the adsorption basically reached equilibrium after 2 h and the process could be well described with the pseudo second order dynamic equation.The adsorption curves followed an isothermic adsorption model,which could be weel described with the Langmuir model.The Cd²⁺ adsorption peaked at 25℃,reaching 6.22 mg·g^-1 as simulated with the Langmuir model.Cd²⁺ removal rate increased with increasing dosage of biochar and decreasing particle size of bilchar.The effect of pH on Cd²⁺ adsorption capacity was not obvious when initial pH of the solution was 4.0-7.5.When biochar is used to remove Cd²⁺ from wastewater,it is advisable to control the initial Cd²⁺ concentration at 30mg·g^-1,particle size of the biochar at <0.25mm,dosage of the biochar at 8g·L^-1,reaction temperature at 25℃,and duration of the reaction at 1-2 h.In this case,the Cd²⁺ removal rate can be as high as 80%.This indicates that biochar made from household biowaste can be as adsorbent to remove Cd²⁺ in polluted water.

Key words: cadmium, household biowaste, biochar, sorption kinetics, isotherm