Capacity of locally isolated bacterial species for sequestration of Cd, Cu and Fe from aqueous Solutions

Removal of heavy metals from wastewater is a major issue. In this study, gram-negative PAB (Pseudomonas Agar Base) and EMB (Eosin Methylene Blue) derived bacterial isolates were prepared from the effluent waters from a refinery in Al-Dora and from the electrical and electronic industry in Al-Waziriya. These bacteria were evaluated for their potential and ability to sequester Cd, Fe, and Cu from aqueous solutions at pH 5, with initial concentrations of heavy metals ranging from 10 to 200 mg/L. Batch experiments were conducted to investigate the equilibrium isotherm and kinetic studies carried out at a dose 2 g biomass /L. The results indicated that both PAB and EMB derived bacteria were effective in removing heavy metals from aqueous solutions. The removal efficiency and equilibrium loading capacity followed the order Fe > Cu > Cd for both live and dead cells of these bacteria, suggesting a higher affinity for Fe compared to Cu and Cd. The maximum loading capacity was found to be 76.2, 67.3 and 62.6 mg.g−1 for Fe, Cu and Cd, respectively. The adsorption kinetics appeared to follow the pseudo-second order slightly better than the pseudo-first order. Based on the biosorption isotherm experiment data, it was observed that both the Langmuir and Redlich-Peterson isotherm models provided a good fit with R2 values of 99 %. Additionally, it was found that PAB-derived bacteria showed slightly higher percentages of heavy metals removal compare to those derived from EMB. This work also showed that PAB-derived bacteria, exhibited more resistance towards heavy metals such as Fe, Cu and Cd compared to EMB-derived bacteria and there is no significant difference in biosorption capacity among four modes of bacteria as evidence by P-value and F critical value based on an ANOVA analysis.