Synthesis of Zeolite from Aluminium Etching By-Product: the Effect of Reaction Temperature on Crystallinity and Its CO₂ Adsorption Property

Abstract

The synthesis of zeolite from the by-product of aluminium etching process was investigated. The starting by-product reactant had high aluminium content, 92.17% wt. as Al₂O₃. Si and Na compositions were adjusted by the addition of sodium metasilicate, in the hydrogel process.The reaction time was fixed at 1 h., while the stirring speed was controlled at 200 rpm. and the temperature varied in the range of 60-90°C. The mole ratio of the starting reactants were also fixed at 2 (SiO₂/Al₂O₃ = 2, Na₂O/ Al₂O₃ = 2). The product properties were found to depend on reaction temperature. The better zeolite product in the range of these experiments was found at 90°C, containing 75% crystallinity as referred to the commercial zeolite A. The percentage crystallinity of the synthesized zeolite was found to increase with increasing reaction temperature. Analysis of the XRay diffraction (XRF) and FT-IR spectra confirmed that the synthetic zeolite was of type A. The CO₂ (99.5% purity) absorption test was performed with the zeolite sample synthesized at 90°C, using N₂ (99.9% purity) as carrier at total flow rate of 15 cc min^-1, resulting in 0.00386 mole of CO₂ adsorption g^-1. The study showed the potential of developing the by-product of aluminium etching process into a higher value added product of zeolite A. Further economic study of the process was suggested.