Effective removal of Cd2+, Zn2+ by immobilizing the non-absorbent active catalyst by packed bed column reactor for industrial wastewater treatment

Abstract

Cadmium and zinc are leading heavy metal pollutants causing serious health problems when discharged into the aquatic environments. The present investigation focused on the bioaccumulation of Cd2+ and Zn2+depending on the sorption process by Bacillus amyloliquefaciens HM28. The selected bacterium was multi-metal (Zn2+, Pb2+, Cd2+, Cu2+ and Li+) and antibiotic (cefotaxime, ampicilin, nalidixic acid, ceftazidime, penicillin and kanamycin) resistance was resolved. The identified strain showed maximum resistance onCd2+ (2575 ppm) and Zn2+ (1300 ppm). The sorption of Cd2+ and Zn2+ by a dried bacterium was investigated. Biosorption of Cd2+ was maximum (98.4 ± 5.2%) at 100 mg/L concentration and maximum Zn2+ (98.3 ± 1.5%) was detected in the medium containing 150 mg/L metal ion. Bioremoval was maximum after 30 min contact time with dried biomass and the absorption rate improved. The optimum Cd2+ and Zn2+ bioremoval yield of 93 ± 4.4% and 89.8 ± 4.3% were observed, at pH 7.0 and 7.5, respectively. Despite the significant reduction in growth rate, heavy metals increased nitro-blue tetrazolium reduction from 11 ± 1.3 to 67 ± 3.3%. Dehydrogenase activity elevated due to heavy metal stress. Bacterial biomass was immobilized in a glass column (20 cm × 2 cm). Biosorption of Cd2+ and Zn2+ ions were performed in a packed bed column. The breakthrough time of Cd2+ was 210 min at 1 mL/min flow rate and it decreased 94 min at 5 mL/min flow rate, whereas 240 min at 1 mL/min, and 90 min at 5 mL/min, respectively. The absorption capacity was 4.87 ± 0.8 to 5.43 ± 0.5 mg/g for Cd2+ and 3.85 ± 0.3 to 4.53 ± 0.4 mg/g for Zn2+. The present findings revealed the potential of B. amyloliquefaciens HM28 biomass in Cd2+ and Zn2+ biosorption, with feasibility in the bioremediation of Cd2+ and Zn2+ contaminated water.