Combined Effect of Sunflower Stem Carbon–Calcium Alginate Beads for the Removal and Recovery of Chromium from Contaminated Water in Column Mode

Abstract

Adsorptive removal of Cr(VI) was investigated in a downflow fixed bed column using sunflower stem carbon–calcium alginate beads (SSC-CAB) at various bed heights (28.0, 38.0, and 52.0 cm), initial Cr(VI) concentrations (10–20 mg/L), and flow rates (1.0–3.0 mL) at preoptimized pH = 2.0 for achieving the breakthrough curves. The adsorption capacity was calculated using the Bohart-Adams (BA) model which is widely used for column adsorption. The highest adsorption capacity of 4.09 mg/L was recorded at a bed height of 52.0 cm, flow rate of 1.0 mL/min, and an initial Cr(VI) concentration of 10.0 mg/L. The breakthrough time increased with a decrease in flow rate and Cr(VI) concentration and an increase in bed height. The adsorption capacity (N0) at 50% breakthrough time was 20 mg/L. Cr(VI) loaded SSC-CAB adsorbent was washed with 0.5 M HCl solution at a flow rate of 2.0 mL/min, and the efficiency of the adsorbent regenerated by the desorbing agent was examined in three sorption/desorption cycles. Regeneration eff...