Cr removal by Chlorella vulgaris as bioremediation: A case study on industrial wastewater

Textile production generates significant amounts of chromium (Cr), posing serious environmental concerns. This study evaluates the ability of Chlorella vulgaris (C. vulgaris) to remove Cr from textile wastewater under varying conditions, including pH (5, 6, 7), C. vulgaris densities (5 × 106, 10 × 106, 15 × 106 cell/mL), and Cr concentrations (50, 60, 70 mg/L). Cr removal was measured at 24-h intervals up to 120 h. Results show that both Cr removal efficiency and surface adsorption on C. vulgaris were significantly affected by these factors (p < 0.05), peaking at 72 h. The optimal conditions for Cr removal were a pH of 6, a microalgae density of 15 × 106 cfu/mL, and a Cr concentration of 70 mg/L, achieving removal rates of 72.98%, 93.58%, and 100%, respectively. Surface adsorption was highest at low algal densities (5 × 106 cfus/mL) but decreased after 72 h across all conditions. Furthermore, the Freundlich isotherm model showed a better fit for Cr adsorption (Kf = 5.65 mg/g, n = 0.7), and suggested a heterogeneous adsorption process. The findings highlight that while C. vulgaris is effective in Cr removal, careful optimization of conditions is necessary to prevent cell stress and maintain efficiency.