Comparative Investigation on Two Synthesizing Methods of Zeolites for Removal of Methylene Blue from Aqueous Solution

Abstract

Organic dyes discharged from industries have significant effect on ecosystem and health of human being because of their toxicity and appearing colour in the wastewater. Absorption method is a more preferable method than other wastewater treatment methods due to its characteristics of being eco-friendly, simple, and efficient. Zeolites are among the porous materials often used as absorbent of organic dye from wastewater. However, wide use of zeolite has been limited due to its expensive precursors and synthesized methods (i.e., hydrothermal method which needs expensive autoclave). In this work, cheap and widely available precursors aluminum from waste food packaging aluminum foil and low cost silica from sugar cane bagasse ash were used to synthesized zeolite without hydrothermal method (Z-B), where hydrothermally synthesized zeolite (Z-A) was used as a reference. The XRD patterns revealed that Z-B was sodalite octahydrate zeolite and Z-A was zeolite Linde Type A (LTA). The morphology and type of bond in both zeolites were investigated by SEM and FTIR. The synthesized zeolites were used as absorbents for absorbing methylene blue (MB) from aqueous solutions. The MB removal efficiency of the synthesized zeolites was evaluated by using UV-Visible spectroscopy. The results indicate that the absorption capacities of Z-B and Z-A were 3.5 mg/g and 3.9 mg/g at 40 mg/L, respectively. Optimum removal efficiencies of both zeolites were observed at PH of 7 and adsorbent dosage of 0.005 mg/L. The stabilities of both zeolites were tested three times. The absorption isotherms of sodalite octahydrate zeolite and zeolite LTA were effectively fitted with the Freundlich and Langmuir modes. Moreover, the absorption kinetics of both zeolites follow pseudo-second-order kinetics. Therefore, nonhydrothermally synthesized zeolite is alternative absorbent for dye removal due to its safety, cheap cost, using low cost and widely available precursors, and using easy and safe synthesizing method.