Biosorption of heavy metals and cephalexin from secondary effluents by tolerant bacteria

The biosorption of heavy metal ions and the antibiotic cephalexin from secondary effluents by the cell biomass of tolerant bacterial strains was investigated in this article. A total of 67 bacterial strains were isolated from a secondary effluents generated by sewage treatment plants. These strains were adapted to tolerate 6 mM nickel ions (Ni²⁺) and 10 g L⁻¹ cephalexin. Bacterial cell biomass that has more than 150 mg g⁻¹ biosorptive capacity was used for the biosorption under optimal conditions. The biosorption process was efficient in removing heavy metals: 87.63 % of cadmium, 74.61 % of copper, 58.32 % of nickel, 61.9 % of lead, and 94.26 % of zinc, respectively. The maximum biosorptive capacity of the bacterial cell biomass for cephalexin was 60 mg g⁻¹. The efficiency of cephalexin biosorption was reduced by more than 40.83 and 82.88 % (living and dead cells, respectively) in the presence of 1 mg L⁻¹ Ni²⁺ ions compared with the control, whereas no biosorption by dead cell biomass was recorded in aqueous solutions contaminated with cadmium, zinc, copper, and lead ions. In conclusion, biosorption which efficiently removes metal ions, but not cephalexin, from secondary effluents is explained.