Biosorption of Cr(VI) by immobilized waste biomass from polyglutamic acid production.

Waste biomass from γ-polyglutamic acid production was used as an adsorbent to remove Cr(VI) from wastewater. Waste biomass was entrapped in sodium alginate to enhance performance. Orthogonal array design was used to optimize biosorption of Cr(VI) by immobilized waste biomass. The optimal adsorption conditions for immobilized waste biomass were as follows: pH 7.0, initial Cr(VI) concentration of 200 mg/L, 35 °C, waste biomass of 2 g/L, 60 min. Under these conditions, the absorption efficiency of Cr(VI) was 96.38 ± 0.45%. When the waste biomass was treated with 1 mol/L HCl for 1 h, the desorption rate could reach 94.42 ± 0.87%. It was shown that the adsorption kinetics followed the Freundlich adsorption model, indicating that the adsorption of Cr(VI) by bacteria was mainly based on multi-molecular layer adsorption. The absorption conditions of waste biomass were mild (pH 6.0-7.5, 20-35 °C) and easily operated. These investigations lay a foundation for reducing the pollution of γ-polyglutamic acid production, turning the biomass waste into a useful adsorbent for wastewater treatment.