Equilibrium biosorption studies in single and multi-metal systems

Different models were used in order to describe equilibrium data obtained b y heavy metal biosorption tests. Arthrobacter sp. biomass was suspended in aqueous solution and tested as biosorbent material for copper and cadmium i ons. The effects of pH on biosorption in single metal systems (copper and c admium) and on the selectivity of biomass in two metal systems (copper-cadm ium) was studied. Biosorption trials performed for each single metal (in th e range 0-2 mmol/l) at different equilibrium pHs (3-6 units) showed a gener al positive effect of pH increase on metal specific uptake. Experimental da ta obtained for each metal were fitted using adsorption models including La ngmuir, Freundlich and Redlich-Peterson isotherms. Biosorption tests were a lso carried out using binary solutions of copper and cadmium at different e quilibrium pH to evaluate biomass selectivity. Modified Langmuir and Freund lich models were used to fit these equilibrium data. The biomass tested was more selective for copper ions and this selectivity changes with equilibri um PH. In both single and two metal systems, a simple procedure of model di scrimination was performed to establish which of the tested models better r epresents the experimental behaviour. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.