NaY zeolite synthesis from rice husk ash for Chromium(VI) ion adsorption

Abstract

NaY zeolite in this study is novelly synthesized from rice husk ash with a one-stage process instead of passing the solid silica recovery process as usual. NaY zeolite applies to assess adsorption ability of chromium(VI) ions in water with varying key factors. The as-synthesized zeolite is characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscope, specific surface area analysis and inductively coupled plasma mass spectrometry with optical emission spectroscopy. As a result, the optimal conditions for silica extraction are at 90oC with a NaOH concentration of 4 M for 4 h with recovery efficiency 87.5%. NaY zeolite is successfully synthesized with Si/Al ratio of 10, aging time of 24 h and crystallization time of 24 h with synthesis yield of 31.25% and crystallinity of 96%. The optimal conditions for the chromium(VI) adsorption in aqueous solution are at pH 2.0, adsorption time of 120 min, initial concentration of 20 mg/L with an adsorbent mass of 0.1 g. The kinetics and adsorption isotherms show a good agreement with pseudo-second order and Freundlich adsorption isotherm model. NaY zeolite is synthesized via environmentally friendly approach with time and energy savings and shows its high adsorb-ability of chromium(VI) in water.