Ni(II) removal from aqueous solution by biosorption and flocculation using microbial flocculant GA1

Generally, most biomaterials present high biosorption capacity for heavy-metal ions. In this study, alkaline reagents and microbial flocculant GA1 (MBFGA1) were combined to remove Ni(II) from aqueous solution. Response surface methodology was employed to optimize the flocculation and biosorption conditions with the Ni(II) removal rate as the response, as well as to analyze the biosorption capacity. At initial Ni(II) concentration of 100 mg L-1, the optimal conditions were predicted to be 1.3 x 10(-2)% (w/w) CaO, 6.59 x 10(-3)% (w/w) MBFGA1, and stirring time of 61.97 min, at which the Ni(II) removal rate and biosorption capacity of MBFGA1 could reach 99.35% and 225.16 mg g(-1), respectively. The biosorption behavior, Fourier-transform infrared spectra, and environmental scanning electron microscopy analysis demonstrated that adsorption bridging with precipitation enmeshment was the most likely mechanism. Analysis of the mechanism and procedure indicated that synergistic flocculation and biosorption by MBFGA1 resulted in the significant Ni(II) removal.