Search

Heavy metal water pollution is a global concern in recent years. Copper is a toxic metal at higher concentrations (> 20 μg /g) and needs to be removed using ion exchanger systems. This study investigates the removal efficiencies of copper by the non-metallic fraction (NMF) waste printed circuit boards (PCBs). The high maximum adsorption capacity of copper by the PCB-derived material after activation with KOH was 2.65 mmol/g, and the experimental isotherm was best correlated by the Temkin model. Finally, this study presents a novel dual site adsorption/ion exchange mechanism, wherein the potassium (from the activation) and calcium (present in the structure) served as ion exchange sites for the copper in the solution. Therefore, this recycling study, focusing on cyclic environmental management, converts a major waste material to an activated ion exchange resin (high capacity) for the removal of copper from wastewater solutions and successfully regenerates the resin for re-use while producing an acidic copper solution for recovery by electrolysius or chemical salt precipitation. [ABSTRACT FROM AUTHOR]

An ion exchange resin, based on the sodium diimidoacetate structure, has been tested for the removal of zinc ions from effluents. After employing three isotherm models, namely, Langmuir, Freundlich and Langmuir-Freundlich to measure and analyse equilibrium isotherms, a series of agitated batch experiments have been carried out to optimise the removal of zinc ions in a two-stage batch system. The first optimisation model involves minimising the total amount of resin required to achieve a specific percentage zinc removal. The second optimisation study involves minimising the total batch contact time to achieve a certain percentage zinc removal. [ABSTRACT FROM AUTHOR]

The sorption of acid dyes from aqueous effluents onto activated carbon has been studied. The effects of initial dye concentration and activated carbon mass on the rate of Acid Blue 80, Acid Red 114 and Acid Yellow 117 removal have been investigated. A three-resistance mass transport model based on film, pore and surface diffusion control has been applied to model the concentration decay curves. The model incorporates an effective diffusion coefficient Deff, which is dependant on the equilibrium solid phase concentration or fractional surface coverage. The results of the film-pore-surface diffusion model are compared with the data obtained from the basic film-pore diffusion model. It has been found that the film-pore-surface diffusion model provides a major improvement over the data correlated by the film-pore diffusion model. Also, the relationship between surface diffusion and fractional surface coverage has been investigated for the adsorption of acid dyes on activated carbon. [ABSTRACT FROM AUTHOR]

A homogeneous solid phase diffusion model (HSDM) has been developed using a computer to predict the performance of a batch adsorber. The computer program utilises a semi-analytical solution for a two resistance model based on external mass transfer and homogeneous solid phase diffusion. The model has been successfully applied to four adsorption systems, namely, the adsorption of AB25, AR114, BB69 and BR22 onto pith. The method produces excellent correlations between experimental and theoretical concentration decay curves in batch adsorbers. The model developed presents a solution using a single solid diffusion coefficient and a single external mass transfer coefficient which are sufficient to characterise the system within a range of initial dye concentration, 25–300 mg · dm3 and solid/liquid ratios (w/v) 0.25–2. [ABSTRACT FROM AUTHOR]