Synergistic arsenic removal using chitosan-based nanocomposite beads and cross-flow ultrafiltration: A significant reduction of membrane fouling

Abstract

Hybrid adsorption-membrane processes provide a suitable alternative for treating large volumes of arsenic-contaminated water by combining the specificity of adsorption with the membrane process’s flexibility in terms of scale-up. The performance of such processes, with respect to removal efficiency and effluent flow rate, largely depends on the characteristics of the adsorbent used. In the present study, we have evaluated the use of in-situ precipitated iron oxyhydroxide chitosan beads (IICB) in combination with cross-flow Ultrafiltration (UF) for the treatment of arsenic-contaminated water. The performance of the combined adsorption-UF process was assessed at three different TMP (0.2–0.6 MPa). Combined Hermia’s model modified for cross-flow UF was found to be a good fit for permeate flux profiles of contaminated groundwater treated using the IICB-UF process. The effect of adding IICB on membrane fouling was evaluated using the resistance-in-series model and XDLVO theory (through contact angle measurements). For arsenic-spiked groundwater, at a dose of 2 g/L IICB, the combined UF process could bring down arsenic to permissible limits (<10 µg/L) and reduce irreversible fouling by up to 32 ± 2%. The reduction of free energy of adhesion and UV254 absorbance values indicated an overall decrease in fouling potential of contaminated feed. Thus, arsenic adsorption using bionanocomposite beads followed by UF (without separation of adsorbent beads prior to UF step) has operational advantages over either of the standalone treatment processes. A similar hybrid technology by varying suitable adsorbents can be successfully applied to remove other toxic pollutants as well.