Improved removal of Cr(VI) from aqueous solution using zeolite synthesized from coal fly ash via mechano-chemical treatment

This contribution reports an alternative method for synthesizing zeolite from coal fly ash via mechano-chemical treatment. The raw fly ash was size reduced to <75m and then mechanically grounded via a wet ball milling system for 6h in the presence of a 2.0M sodium hydroxide (NaOH) solution to synthesize zeolite. The synthesized zeolite and the raw fly ash were then used to remove Cr(VI) from aqueous solutions. The results show that, under equilibrium conditions, the maximum removal of Cr(VI) increases from 0.803mg/g of the raw fly ash to 1.549mg/g of the synthesized zeolite. The improved Cr(VI) removal capacity of the synthesized zeolite can be attributed to the formation of zeolite X, and to a lesser extent, the improved physical adsorption capacity. Low-valence iron (e.g. Fe3O4) in the raw fly ash and the synthesized zeolite plays a significant role in reducing and removing Cr(VI) from aqueous solutions. (c) 2017 Curtin University of Technology and John Wiley & Sons, Ltd.