SYNTHESIS OF LINDE TYPE A ZEOLITE–GOETHITE NANOCOMPOSITE AS AN ADSORBENT FOR CATIONIC AND ANIONIC POLLUTANTS

Abstract

LindetypeAzeolite(LTA)–goethitenanocompositewassynthesizedbyaddingsodiumorthosilicatesolution 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 inthefinalproductwassuggestedbydifferencesinIRspectraandSEMimagesbetweenthefinalproduct andamixtureofLTAandgoethite.ThemixtureseparatedintoLTAandgoethitecomponentsafterwashing 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.