Competitive Metal Ion Binding to a Silicate-ImmobilizedDatura innoxiaBiomaterial

Metal ion binding with a flowing system to a biosorbent comprised of cultured cell-wall fragment within a polysilicate matrix has been investigated. Solutions containing 0.10 mM Pb2+, Cu2+, Ni2+, Cd2+, and Zn2+ were exposed to the material in combinations of two, three, and five metals while simultaneously monitoring the concentration of all metals in the effluent stream. A relative affinity order of Pb2+ > Cu2+ >> Zn2+ ≈ Cd2+ > Ni2+ was determined when all five metal ions were exposed to the material. Lower-affinity metal ions were exposed to the material sequentially. Both metal-specific and common binding sites were observed for each metal ion. The presence of both binding sites that are common to all metal ions investigated and sites that appear to be unique for each metal ion could significantly impact the utility of single-metal ion studies on the application of such biosorbents for the selective removal of metal ions from natural water.