Synthesis of zeolite X from low-grade bauxite

BACKGROUND Zeolite X is one of the most important synthetic zeolites and has been used extensively. Therefore, to satisfy its high demand the synthesis of zeolite X from inexpensive sources is very desirable. Low-grade bauxite, an inexpensive aluminium and silicon source has been used to synthesize zeolite A. In the present paper, the production of zeolite X from this inexpensive low-grade bauxite is attempted for the first time. RESULTS The combination of alkali fusion activation and hydrothermal reaction synthesis provides a successful method to synthesize zeolite X from this low-grade bauxite. The molar ratios of SiO2/Al2O3, Na2O/SiO2andH2O/Na2O are the most crucial parameters, which determine the phase composition and crystallinity of products. Using sodium silicate solution to adjust SiO2/Al2O3 molar ratio, highly crystallized zeolite X is achieved under the optimized experimental conditions of 2Na2O: 0.2Al2O3: 1SiO2: 76H2O at 95 degrees C for 24 h. The synthesized zeolite X was further characterized by SEM, BET, FT-IR, and thermal stability. CONCLUSION The results indicate that the inexpensive raw material can be utilized to synthesize highly-crystallized zeolite X under optimized experimental conditions.