Batch isotherm and kinetic of cadmium ions biosorption by immobilised Bacillus circulans and Saccharomyces cerevisiae from aqueous solution

Abstract

Heavy metals are very harmful to the environment and living organisms if the maximum permissible limit is exceeded.  Cadmium is one of the known heavy metals that have effect on the environment and living organism. There is the need for an environmentally friendly and cost-effective technique such as biosorption for removal or controlling the excess of cadmium ions in aqueous solution. The isotherm and kinetic of lyophilised immobilised Bacillus circulans and Saccharomyces cerevisiae were investigated as biosorbents for biosorption of cadmium ions from aqueous solution in a batch process system. The biosorbents developed were characterised using Scanning electron microscope and Fourier transform infrared spectroscopy. The effects of environmental parameters on biosorption of cadmium ions onto immobilised biosorbents of Bacillus circulans and Saccharomyces cerevisiae in a batch process system were also compared and investigated. The optimum parametric values such as pH, contact time, biosorbent dosage and initial concentration for: Cadmium ions onto Bacillus circulans were obtained as 7, 100 min, 1.0 g and 100 mg/l, respectively; Cadmium ions onto Saccharomyces cerevisiae were recorded as 6, 80 min, 1.0 g and 100 mg/l, respectively. The biosorption mechanism shows better fitness of Freundlich isotherm model and the kinetics follows Pseudo second order for both immobilised Bacillus circulans and Saccharomyces cerevisiae for cadmium ions contacting. The results show that immobilised Bacillus circulans and Saccharomyces cerevisiae are highly efficient in the removal of cadmium ions from aqueous solution. The percentage removal for cadmium ions onto Bacillus circulans gives better optimum performance to Saccharomyces Cerevisiae contacting.