removal and recovery of nickel ions from aqueous solutions using bacillus sphaericus biomass

this paper discusses the biosorption of ni(ii) ions from aqueous solutions by bacillus sphaericus biomass. the biosorption process was affected by the solution ph, biomass concentration, contact time, temperature and initial ni(ii) concentration respectively. the sorption kinetics and equilibrium data were described well with the pseudo-second order kinetic model and the freundlich isotherm model. the maximum monolayer biosorption capacity value of bacillus sphaericus biomass for ni(ii) ions was calculated at 55.55 mg/g using the langmuir isotherm model. the thermodynamic study shows the ni(ii) biosorption was spontaneous and exothermic in nature. the change in heat of sorption (δho) and the isosteric heat of sorption (δhr) values indicate the physical sorption as the predominant mechanism for ni(ii) biosorption. the ni(ii) ions were recovered effectively from bacillus sphaericus biomass using 0.1 m hno3 and can be recycled. ftir results showed that carboxylic and amine groups of bacillus sphaericus cells were responsible for ni(ii) binding.