Adsorption of copper and zinc on Pseudomonas putida CZ1: particle concentration effect and adsorption reversibility

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 0.01 M 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: gamma = 2.553C(p)(-0.7106) C(eq)(0.8971) for Cu-biomass system, gamma = 2.412C(p)(-0.8305) C(eq)(0.6504) 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.