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Abstract In order to reduce the cost and increase the feasibility of real application in removal of heavy metals by bacteria, the discharged soybean wastewater was used as cheap culture for bacterial cultivation, and the cultured bacteria were applied to remove heavy metals from electroplating wastewater. It was found that Bacillus cereus and Ochrobactrum anthropi could be well grown in dilute soybean wastewater, means that the soybean wastewater could ensure the necessary nutrition for bacterial growth. In addition, soybean wastewater with adding sucrose residue leach solution (pH 7.5) was the optimum condition for bacterial growth. Further studies revealed that when the initial concentrations of chromium and nickel in electroplating wastewater were 214 mg/L and 367 mg/L respectively, the cultured bacteria in optimum medium had a strong capacity of Cr(Ⅵ) and Ni(Ⅱ) removal. Meanwhile, the biomass of B. cereus and O. anthropi could be greatly affected the removal efficiency, the more bacterial biomass, the better removal ability, and the removal efficiency could be higher than 80%. Moreover, microscopic investigation (such as atomic force microscopy, scanning electron microscopy and transmission electron microscopy) showed that the morphology of B. cereus was destroyed severely after reacted with chromium and nickel in electroplating wastewater, and the energy dispersive X-ray spectroscopy (EDS) analysis indicated both extracellular immobilization and intracellular accumulation involved in the bioremoval of Cr(Ⅵ) and Ni(Ⅱ). Additionally, Fourier transform infrared (FT-IR) analysis suggested that N-H and C=O functional groups from bacteria might play an important role in heavy metals immobilization process. This study provides a new idea for application of bacteria in remediation Cr(Ⅵ) and Ni(Ⅱ) containing wastewater by cheap cultivation with discharged soybean wastewater.
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Received: 05 April 2014
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