Synthesis of Linde type A zeolite-goethite nanocomposite as an adsorbent for cationic and anionic pollutants

Linde type A zeolite (LTA)-goethite nanocomposite was synthesized by adding sodium orthosilicate solution to goethite, followed by addition of sodium aluminate and NaOH solutions at 100 °C. Optimum condition at the Si addition step required for nanocomposite formation was pH 10.0 and Si/Fe = 2.7. The final product composed mainly of LTA and goethite crystals. Formation of LTA-goethite nanocomposites in the final product was suggested by differences in IR spectra and SEM images between the final product and a mixture of LTA and goethite. The mixture separated into LTA and goethite components after washing with water, but the final product did not show such separation. Precipitation of silica on the surface of goethite and subsequent formation of Si-O-Fe bonds at the Si addition step contributed to formation of the LTA-goethite nanocomposite. The amount of adsorption of phosphate on the final product was more than 1.6 times the amount adsorbed on the mixture, indicating generation of synergistic effect in the LTA-goethite nanocomposite.