Enhanced arsenic removal from drinking water by iron-enriched aluminosilicate adsorbent prepared from fly ash

The study deals with an efficient approach for the utilization of fly ash and mitigating one of the most severe drinking water problems caused due to arsenate. Iron enriched aluminosilicate adsorbent (IEASA) was synthesized using a novel method of alkali fusion of fly ash followed by ageing and hydrothermal curing. The raw material, intermediates, and final products were thoroughly characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and particle size analysis. The characterization results suggested that the prepared adsorbent is highly crystalline with particle size of <500nm. The IEASA was evaluated as an adsorbent for the removal of arsenate at initial concentration of 1mgL(-1) by batch adsorption studies, which shows excellent removal efficiency for arsenate (above 99%) in wide pH range of 4-10 and in the presence of various interfering ions. The efficiency was also compared with synthetic zeolite, which shows negligible arsenate removal. Adsorption isotherms were plotted using the Langmuir and Freundlich models to compute the adsorption capacities. The adsorption capacity obtained from Langmuir isotherm was 0.592mgg(-1) as compared to the adsorption capacity of 0.455mgg(-1) calculated from kinetics data. Detailed kinetics studies were also carried which confirms that the adsorption kinetics follows pseudo-second-order and particle diffusion is the rate determining step. Water quality was evaluated before and after adsorption, which suggests the suitability of the adsorbent for the decontamination of arsenate from drinking water and other parameters also confirms that treated water is potable.