Biosorption of cupric and cadmium ions by corncob particles

Abstract

The effects of various parameters, such as initial pH, biomass concentration, temperature, buffer, agitation speed, and particle size, on the biosorption of cupric and cadmium ions by the corncob particles were investigated. A modified Langmuir model, which considers the effect of pH on the isotherm, is appropriate for the experimental equilibrium data. The enthalpy changes calculated from the equilibrium constants at various temperatures indicate that the biosorption processes of copper and cadmium on the corncob particles are exothermic. The smaller comcob particles have a higher adsorption rate and uptake, which suggests that the particle size not only affects adsorption kinetics, but also the equilibrium (isotherm). A novel reversible surface reaction model combined with an effectiveness factor was developed. An experimental procedure was designed to determine four constants (the effectiveness factor, the maximum adsorption capacity, the forward and backward rate constants) in the model. In addition, a preliminary study on competitive biosorption of copper and cadmium ions from their mixture by the corncob particles was conducted. The pH at zero charge point of the corncob particles was measured (pH zcp 4.97) by applying the primary equilibrium method of H+ and OH-. (Abstract shortened by UMI.)