Use of zeolite for cadmium removal from wastewater

Abstract

Kinetics and thermodynamics of uptake of Cd²⁺ (in concentration of 10 and 50 mg/dm³) by natural and modified zeolite have been investigated. Kinetic data obtained are best described by the kinetic equation for the second order irreversible reactions and the equilibrium data obtained best fit to Freundlich adsorption isotherm. It has been found that (a) the ratio of wastewater to zeolite equal to 0.1 dm³: 1 g was the optimum, (b) use of zeolite with particles’ size <0.09 μm increased Cd²⁺ uptake, (c) Cd²⁺ removal due to zeolite's uptake was the highest if the pH value of water to be treated was in the range of pH 5–7, (d) uptake of Cd²⁺ was considerably decreased in presence of Ca²⁺ and Mg²⁺ in concentrations 2 folds the concentration of Cd²⁺, (e) zeolite treated with NaCl and CH₃COONa showed the highest uptake ability, (f) concentrations lower than 0.5 and 8–10 mg/dm³ can be achieved by one stage treatment of soft water when the initial Cd²⁺ concentrations are 10 and 50 mg/dm³ correspondingly, and (g) contacting with 2 mol/dm³ NaCl solution can easily regenerate loaded zeolite.

Key words:

• Cadmium ions
• removal
• wastewater
• zeolite