Characterization of metal removal of immobilized Bacillus strain CR-7 biomass from aqueous solutions

Bacillus strain CR-7 of multiple metal and antibiotic resistances was isolated. Its metal adsorption under different pretreatments and immobilizations from aqueous solution was characterized. Pretreatment with NaOH (0.1 mol L−1) significantly improved Cu2+ adsorption capacity of the bacterial biomass. Sodium alginate (2%) was the ideal immobilization matrix. The immobilized and pretreated biomass had an obvious “orderliness”, following the order of Cu2+ > Zn2+ in the solution containing these two metals, and following the order of Pb2+ > Al3+ > Cr6+ > Cu2+ > Fe3+ > Zn2+ = Ni2+ > Cd2+ = Co2+ > Mn2+ in the solution containing these 10 metals. ΔH° and ΔS° of Cu2+ adsorption were +7.68 J/mol and +16.628 J/mol K, respectively. The infrared peak of -N-H shifted greatly after Cu2+ adsorption. After adsorption treatment, some molecular groups disappeared in un-immobilized biomass but were still present in the immobilized biomass. Cu2+ adsorption fit both Langmuir and Freundlich isotherm models. It was concluded (1) that the Cu2+ adsorption process was endothermic, (2) that -N-H is a most important Cu2+-binding group, (3) that immobilization prevents loss or damage of the Cu2+-binding molecular groups, and (4) that Cu2+ adsorption of pretreated and immobilized biomass is homogeneous.