Activated Carbon Microsphere from Sodium Lignosulfonate for Cr(VI) Adsorption Evaluation in Wastewater Treatment

In this study, activated carbon microsphere (SLACM) was prepared from powdered sodium lignosulfonate (SL) and polystyrene by the Mannich reaction and ZnCl₂ activation, which can be used to remove Cr(VI) from the aqueous solution without adding any binder. The SLACM was characterized and the batch experiments were conducted under different initial pH values, initial concentrations, contact time durations and temperatures to investigate the adsorption performance of Cr(VI) onto SLACM. The results indicated that the SLACM surface area and average pore size were 769.37 m²/g and 2.46 nm (the mesoporous material), respectively. It was found that the reduced initial pH value, the increased temperature and initial Cr(VI) concentration were beneficial to Cr(VI) adsorption. The maximum adsorption capacity of Cr(VI) on SLACM was 227.7 mg/g at an initial pH value of 2 and the temperature of 40 °C. The adsorption of SLACM for Cr(VI) mainly occurred during the initial stages of the adsorption process. The adsorption kinetic and isotherm experimental data were thoroughly described by Elovich and Langmuir models, respectively. SL could be considered as a potential raw material for the production of activated carbon, which had a considerable potential for the Cr(VI) removal from wastewater.