Kinetics of mercury adsorption from wastewater using activated carbon derived from fertilizer waste

The waste slurry generated in a fertilizer plant was converted into a carbonaceous material and used as an adsorbent for the uptake of Hg (II) from wastewater. The kinetics of adsorption depends on the adsorbate concentration, and the physical and chemical characteristics of the adsorbent. Studies were conducted to delineate the effect of pH, temperature, initial absorbate concentration, particle size of the adsorbent and solid to liquid ratio. The adsorption of Hg (II) increased with the decrease in pH and the process was exothermic. On the basis of these studies, various parameters such as mass transfer coefficient, effective diffusion coefficient, activation energy and entropy of activation were evaluated to establish the mechanisms. It was concluded that the adsorption occurs through a film diffusion mechanism at low concentrations, and particle diffusion at higher concentrations.