Kinetic and Thermodynamic Analyses of Cu2+ Adsorption by Vermicompost

The study investigated the effects of the initial Cu2+ concentrations, temperature, pH and time on the adsorption of Cu2+ by vermicompost. The isothermal characterization, kinetics and thermodynamics of the adsorption process were also analyzed. The results show that the vermicompost has excellent adsorption performance to Cu2+ in water solution. Under the adsorption conditions of 25oC, initial Cu2+ concentrations of 87.925 to 574.95 mg/L, vermicompost dosage of 0.25 g/10 mL, oscillation rate of 200 rpm, and adsorption time of 12 h, the adsorption efficiency reached 95.27% to 98.07%. pH has little influence on the adsorption. The adsorption behaviors of Cu2+ on vermicompost conformed to pseudo second order kinetics equation. At different temperature, the adsorption process presents nonlinear adsorption isotherm, and fitted very well by Freundlich model. Gibbs free energy (?G) of the adsorption was smaller than 0, indicating a spontaneous endothermic reaction of Cu2+ on vermicompost.