Novel humic acid-based carbon materials: adsorption thermodynamics and kinetics for cadmium(II) ions.

Novel humic acid-based carbon materials were prepared by using carbonization and activation in the present paper. The effects of processing and temperatures on the microstructure and the adsorption ability of cadmium ion were investigated. The functional groups, thermal stability, pore structure, and morphology of products were characterized. The results showed that the oxygen functional groups decreased and the pore structure increased with increasing carbonization temperature. The adsorption kinetics of cadmium(II) on humic acid-based carbon materials could be expressed by the pseudo-second-order kinetic model, and the adsorption isotherm of carbonized samples and activated samples was fitted by Langmuir model and Freundlich model respectively. It indicated that the adsorption of cadmium(II) on carbonized humic acid was controlled by the chemical reaction and occurred on the monolayers surface, while the adsorption of cadmium(II) on carbonized humic acid was controlled by the chemical reaction and occurred on the heterogeneous surface. The adsorption quantity increased with pH from 2 to 6 and remained constant up to pH 6. The equilibrium adsorption quantity increased with carbonization temperature from 12.3 mg/g at 400 °C to 17.4 mg/g at 800 °C. After activated at 600 °C, the humic acid-based carbon achieved the maximum adsorption quality (26.3 mg/g). [ABSTRACT FROM AUTHOR]