ADSORPTION OF METAL-IONS BY RHIZOPUS-ARRHIZUS BIOMASS - CHARACTERIZATION STUDIES

Freeze-dried, oven-dried, and nonmetabolizing live Rhizopus arrhizus b iomass were tested for their capacity to adsorb the test ions, Sr2+, C d2+, and Cu2+, over the pH range 4-6. Metal uptake values for each bio mass type were found to increase in the order Cu2+ > Cd2+ > Sr2+. Free ze-dried biomass proved to be the most efficient biomass type for meta l adsorption, followed in order by oven-dried and five biomass for Sr2 + systems, and live and oven-dried biomass for Cd2+ and Cu2+ systems. Each test ion displaced constant levels of Ca2+ and Mg2+ ions from the three biomass types, indicating that biomass pretreatment had no appa rent effect on the ion-exchange capacity of Rhizopus arrhizus. Similar ly, the levels of H+ displacement resulting from test ion adsorption w ere unaffected by pretreatment but were found to increase in the order Cu2+ > Cd2+ > Sr2+. Linear reciprocal Langmuir and Scatchard transfor mation plots reflected the predominantly ion-exchange mechanism of Sr2 + and Cd2+ adsorption, and a curved Scatchard transformation plot refl ected the more covalent nature of Cu2+ adsorption.