Modeling and evaluation on removal of hexavalent chromium from aqueous systems using fixed bed column

Removal of hexavalent chromium by xanthated chitosan was investigated in a packed bed up-flow column. The experiments were conducted to study the effect of important design parameters such as bed height and flow rate. At a bed height of 20 cm and flow rate of 5 mL min−1, the metal-uptake capacity of xanthated chitosan and plain chitosan flakes for hexavalent chromium was found to be 202.5 and 130.12 mg g−1 respectively. The bed depth service time (BDST) model was used to analyze the experimental data. The computed sorption capacity per unit bed volume (N0) was 4.6 ± 0.3 and 78.3 ± 2.9 g L−1 for plain and xanthated flakes respectively at 10% breakthrough concentration. The rate constant (Ka) was recorded as 0.0507 and 0.0194 L mg−1 h−1 for plain and xanthated chitosan respectively. In flow rate experiments, the results confirmed that the metal uptake capacity and the metal removal efficiency of plain and xanthated chitosan decreased with increasing flow rate. The Thomas model was used to fit the column sorption data at different flow rates and model constants were evaluated. The column was successfully applied for the removal of hexavalent chromium from electroplating wastewater. Five hundred bed volumes of electroplating wastewater were treated in column experiments using this adsorbent, reducing the concentrations of hexavalent chromium from 10 mg L−1 to 0.1 mg L−1.