Facile Synthesis of Zeolite NaX from Natural Attapulgite Clay for Pb2+ Adsorption

The synthesis of zeolites from natural aluminosilicate minerals has drawn extensive attention due to its significant utility in greening the zeolite manufacturing process. In this study, pure-phase NaX zeolite was synthesized via a low-temperature hydrothermal method, utilizing natural, low-quality attapulgite clay as the raw material. Acidified clay was fully activated through alkali fusion at 200 °C, and the impact of alkali fusion temperature, H2O/Na2O ratio, aging temperature, and crystallization time on the resulting crystalline NaX zeolite was investigated. The optimal conditions for obtaining pure NaX zeolite were determined to be alkali melting at 200 °C for 4 h, an H2O/Na2O ratio of 50, aging at 40 °C, and a crystallization period of 11 h at 90 °C. With a large BET surface area of 328.43 m2/g, the obtained NaX zeolite was used to adsorb Pb2+ from wastewater with a removal rate of 95%. This research provides a valuable method for the extensive and efficient utilization of low-grade natural attapulgite clay. Moreover, this is the first report on the synthesis of pure-phase NaX zeolite using only low-quality natural attapulgite clay as raw material through an atmospheric pressure water bath method.