Removal of methylene blue using zeolite NaX with silica derived from rice husk ash

Abstract

This work investigates some parameters affecting the adsorption of methylene blue (MB) in synthesised wastewater using NaX. Zeolite has been synthesised from rice husk ash (RHA) without pretreatment to make use of cheap and readily available by-products in Vietnam. The parameters affecting the adsorption process such as pH, the concentration of MB, adsorbent dose, and contact time were specifically investigated. In addition, the adsorption isotherm models such as Langmuir, Freundlich, Dubinin - Radushkevich, pseudo-first-order kinetic, and pseudo-second-order kinetic were performed. The results showed that the maximum adsorption capacity and efficiency of NaX on MB were 16.67 mg/g and 87.03%, respectively, at pH 8, MB concentration of 15 mg/l, adsorbent dose of 0.05 g, and contact time of 30 min. The adsorption of MB by NaX has followed the Freundlich model and was physical adsorption fitted to pseudo-second-order kinetic. Zeolite NaX was reused four times with a decrease of adsorption yield by 24.03%. This study reveals the potential application of NaX on the removal of organic dyes and future researches on the removal of heavy metals or gases.