Copper removal from aqueous systems: Biosorption by Pseudomonas syringae

The potential of two strains of Pseudomonas syringae (Blue and Brown) to re move copper from aqueous solutions has been investigated and assessed again st the synthetic Linde LZ-52Y aluminosilicate zeolite. The two bacterial st rains were tolerant to copper and were able to grow in media doped with con centrations of up to 1000 ppm. The biosorptive capacity and the mechanism o f copper uptake were investigated using "active" and "inactive" species gro wn in nutrient-rich and complex media. The degree of copper removal by ion exchange with the Y zeolite is reported and compared with that achieved whe n using the biosorbents under the same treatment conditions. The bacteria w ere harvested, freeze-dried, and used to adsorb copper under starved and gl ucose activated conditions. The need to distinguish between "bio-uptake" an d the action of complexing agents that may be present are highlighted. The experimental data are fitted to standard Freundlich, BET, and Langmuir adso rption models where the latter yielded both meaningful theoretical maximum adsorption capacities and adsorption affinity coefficients. These values ar e discussed in terms of the sorbate/sorbent interactions, which are shown t o involve a passive mechanism where the majority of the copper attaches to the outer cell wall.