Synthesis of zeolite L using rice husk ash silica for adsorption of methylene blue: kinetic and adsorption isotherm

¹ UIN Sunan Gunung Djati Bandung, Department of Chemistry Education, Bandung, Indonesia
² UIN Sunan Gunung Djati Bandung, Department of Chemistry, Faculty of Science and Technology, Bandung, Indonesia
³ Institut Teknologi Bandung, Master Program in Computational Science, Faculty of Mathematic and Natural Science, Bandung, Indonesia

^a Corresponding author: citra@uinsgd.ac.id

Abstract

Rice husk has a high silica content, so it can be utilized as silica source for zeolite synthesis. In this research, synthesis of zeolite L has been done using silica from rice husk ash without organic template. The synthesized zeolite L is then used as an adsorbent to adsorb methylene blue dye. The steps of zeolite L synthesis include: silica extraction from rice husk ash using NaOH and zeolite L synthesis using hydrothermal method with molar ratio 10 SiO₂: Al₂O₃: 4 K₂O: 100 H₂O at 170°C for 24 hours. The resulting Zeolite L was then characterized by XRD and SEM. The absorption capacity of methylene blue solution by zeolite L was observed experimentally through the effect of pH of the solution, contact time, and initial concentration of the solution, then determining the isotherm and its absorption kinetics. From XRD and SEM results of zeolite L sample, it is shown that zeolite L has been formed and its particle morphology is a hollow cylinder with cylinder diameter of 0.049 - 0.123 μm. The adsorption process refers to the Freundlich isotherm model which provides the highest correlation coefficient. The methylene blue adsorption process by zeolite L follows pseudo second-order kinetics.