Cr(VI) Removal from Water by Fixed-Bed Column Filled with Modified Corn Stalk

Abstract

Fixed-bed columns filled with modified corn stalk (CS-AE) were developed to remove Cr(VI) from aqueous solution and electroplating wastewater. Effects of height–diameter ratio (H/D), flow rate, and Cr(VI) concentration on breakthrough curves were investigated, and different models were adopted to describe the dynamic adsorption performance. Experimental results showed that both breakthrough time and exhaustion time increased with the increase of bed H/D and with the decrease of flow rate and influent Cr(VI) concentration. Thomas model agreed well with experimental data under different conditions, and the rate constant kTh increased with the increase of flow rate and with the decrease of initial Cr(VI) concentration and H/D, whereas the dynamic adsorption capacity q0 showed a reverse trend. At suitable operation conditions (H/D 3.75 and flow rate 15 min/L), q0 could reach 55.4 mg/g and kTh was in range of 8.6–10 × 10−4 mL/[min·mg]. The CS-AE column can be easily regenerated by 1.0 M HCl in about 20 min. It was found that Cr(VI) was partially reduced to Cr(III) in CS-AE column, which also showed ability to retain Cr(III) ions. The breakthrough time of sulfate ion (30 min) was much shorter than that of Cr(VI) (80 min) in experiment with electroplating wastewater, suggesting that CS-AE column has the potential to selectively remove Cr(VI) under real wastewater conditions.