Enhanced Removal of As(V) and Pb(II) from Drinking and Irrigating Water Effluents Using Hydrothermally Synthesized Zeolite 5A

Abstract

Zeolites 5A were obtained by ion exchange of a zeolite 4A, previously synthesized by the hydrothermal method from precursor kaolin, with the aim of removal As(V) from drinking water and Pb(II) from irrigation surface water. Zeolite 5A was characterized before and after adsorption by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. To find the adsorption mechanisms of both As and Pb in real waters, experiments on adsorption kinetics, optimum pH, adsorbent dose, and adsorption isotherms were developed. Adsorption kinetics and adsorption isotherm models were evaluated, and the selection criterion for the appropriate model was made using the residual sum of squares (RSS) and Bayesian information criterion (BIC). As a result, removal adsorption of As(V) and Pb(II) was higher than 95% in 9 and 12 h, respectively. The estimated maximum adsorption capacities for As and Pb were 36.35 mg g−1 and 46.67 mg g−1, respectively. Zeolite 5A is a low-cost adsorbent, through which a concentration of less than 0.01 mg L−1 of As and Pb was obtained in drinking and irrigation water, which is below the permissible limit established by the World Health Organization (WHO).

Keywords

• adsorption mechanism
• zeolite adsorbents
• water treatment
• heavy metals pollution and management
• after adsorption characterization