Optimization of chromium(VI) removal by indigenous microalga (<i>Chlamydomonas</i> sp.)‐based biosorbent using response surface methodology

Abstract Phycoremediation of heavy metals has garnered considerable recent research interest. In this study, an indigenous microalga ( Chlamydomonas sp.)‐based biosorbent was employed for biosorption of Cr(VI) dissolved solids (Cr(VI)‐DS), optimized using response surface methodology (RSM). The effects of microalga concentration, pH, and contact time were studied with 250 mg Cr(VI)‐DS L −1 . The biosorption of Cr(VI)‐DS was higher at acidic pH (94.17% at pH 4) than at alkaline conditions (68.53% at pH 10). The interaction of pH and microalga concentration exerted significant ( p  < 0.05) influence on the biosorption. Under the optimized parameters of 1.5 g microalga L −1 , pH 4, and contact time of 30 min, a predicted biosorption of 91.31% and biosorption capacity of 152 mg Cr(VI)‐DS g −1 biomass were documented. FTIR analysis attested the electronegative surface functional groups of the microalgae biomass, bracketed together with its high biosorption potency. The study evinced the potential of the indigenous microalga for remediation of hexavalent chromium. Practitioner points Indigenous Ethiopian microalga ( Chlamydomonas sp.) exhibited 94% Cr(VI) abatement with biosorption capacity of 152 mg Cr(VI) g −1 . FTIR analysis of the biosorbent divulged the presence of electronegative functional groups (amino, carboxyl, hydroxyl, and carbonyl groups). Higher biosorption of Cr(VI)‐DS under acidic pH (94.17% at pH 4) than alkaline pH (68.53% at pH 10). Significant ( p  < 0.05) interaction effect of pH and biomass concentration on the biosorption, evinced in RSM optimization 91% Cr(VI) removal achieved under optimal conditions of 1.5 g biosorbent L −1 , 30 min of contact time, and pH 4.