Pure zeolite Na-P and Na-X prepared from coal fly ash under the effect of steric hindrance.

BACKGROUND Coal fly ash ( CFA) is a solid waste generated during combustion and transformation of coal that causes serious environmental pollution because of the huge amount of emissions and subsequent accumulation. In this work, coal fly ash was selected as a source of silicon and aluminum components to synthesize zeolites Na-P and Na-X. RESULTS High purity zeolites Na-P and Na-X were synthesized under hydrothermal conditions. The influences of an organic steric agent and different sodium salts on the preparation were investigated and the process parameters of the hydrothermal system optimized. The synthesized product was further characterized by XRD, SEM, ICP, FTIR, and BET surface area measurements. Adsorption tests of Na-P and Na-X zeolite for Ni²⁺ were performed and flame atomic absorption spectrometry ( FAAS) was used for the detailed analysis. CONCLUSION Pretreatment and purification of CFA favors the preparation of pure Na-P and Na-X zeolite. The organic steric agent and different sodium salts were used to decrease the grain size of the product and control the purity and yield, respectively. Zeolite Na-P synthesized with the addition of TEA (triethanolamine) had the best Ni²⁺ adsorption performance and a hypothesis for Ni²⁺ adsorption is proposed. Preliminary analysis proved that Van der Waals absorption is the main type of adsorption for the porous zeolite but ion exchange could also occur with the effect of metal ion exchange contributing a maximum of 13.56% to the total adsorption capacity. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]