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Abstract: Bacterial–mineral composites are important in the retention of heavy metals due to their large sorption capacity under a wide range of environmental conditions. This study provides the first quantitative comparison of the metal-binding capacities of P. putida CZ1–goethite composite to its individual components. When the same amount (on a dry weight basis) of living and nonliving cells of P. putida CZ1, goethite or their composites was separately exposed to solutions of 0.5mM Cu(II) and Zn(II) in 0.01M KNO3, the living cells removed the largest quantity of heavy metals. The results of calculated metal retention values indicated that the adsorption of goethite to bacteria has not mask or neutralize chemically reactive adsorption sites normally available to metal ions. Moreover, the nonliving cells–goethite composite retained approximately 82% more Zn than that predicted by their individual behavior. The preferential association of Zn with P. putida CZ1 was observed by TEM and EDS analyses of a mixture consisting of the bacteria and goethite. Desorption of Cu and Zn with 1.0M CH3COOK solution from P. putida CZ1 and goethite indicated the differences in the functional groups able to bind heavy metals. [Copyright &y& Elsevier]

Abstract: The adsorption and desorption processes of Cu(II) and Zn(II) on the biomass of Pseudomonas putida CZ1 as a function of particle concentrations (C p) were studied. In a 0.01M KNO3 solution, the Cu-biomass and Zn-biomass adsorption systems displayed a clear C p effect. The overall adsorption isotherms under three C p conditions could be described as a Freundlich-type C p effect isotherm equation: for Cu-biomass system, for Zn-biomass system. The results of experiments, designed to eliminate several typical sources of experimental artifact, agree with the prediction of the metastable-equilibrium adsorption theory. Results from laboratory equilibration studies also indicate that biomass-adsorbed Cu(II) or Zn(II) fractions may be comprised of both reversibly and strongly bound or resistant components. A computational method has been derived to allow prediction of the magnitude of the reversible and more strongly adsorbed Cu(II) or Zn(II) fractions from conventional isotherm data. This methodology provides an initial quantitative approximation of the strongly bound, resistant, biomass fractions while utilizing relatively simple experimental adsorption–desorption data. [Copyright &y& Elsevier]