Synthesis of Zeolite A from By-Product of Aluminum Etching Process: Effects of Reaction Temperature and Reaction Time on Pore Volume

Abstract

Problem statement: Increasing of the carbon dioxide (CO₂) concentration in the atmosphere creates a global warming. Zeolite is used as CO₂ absorbent. Approach: By-products from aluminum etching process, which carry a large amount of Al₂O₃ content, are useable as raw materials for synthesis zeolites type A using hydrogel process. A pore volume of zeolites is the key to achieve high CO₂ absorption capacity. In this study, two-factor factorial experiments with 3 replicates and α = 0.05 have been conducted to examine the influence of reaction temperature and reaction time on the pore volume and to determine the process conditions for containing the highest pore volume. Three levels of the reaction temperature of 75, 85 and 95°C and three levels of the reaction time of 1, 2 and 3 h (s), while the stirring speed is controlled at 300 rpm, are selected for the experiment. The mole ratios of the starting reactants are fixed at 2 of SiO₂/Al₂O₃, 2 of Na₂O/ Al₂O₃ and 85 of H₂O/Na₂O. Analysis of surface area is performed by the BJH method and the DR method for analysis of gas adsorption-desorption using nitrogen. Results: The results found that there was significant interaction between the reaction temperature and the reaction time and at 95°C of 3 hours gave the highest pore volume, resulting in 0.0205cc g⁻¹ of the BJH method and 0.0065 cc g⁻¹ in the DR method. Besides, the CO₂ absorption test is also performed with the zeolite synthesized at 95°C. Conclusion: Zeolite syntheses of by product from alkaline etching of the aluminum industry have a major analysis agree well with those of reference zeolite A. Adsorption test with CO₂, yield the best result with ZA31, with the capacity of 0.1023 ccg^-1.