Static and dynamic adsorption of arsenate from water by Fe3+ complexed with 3-aminopropyltriethoxysilane-modified carboxymethyl chitosan

Abstract

Abstract Fe3+ complexed with 3-aminopropyltriethoxysilane (APTES)-modified carboxymethyl chitosan (CMC) named Fe-ACMC was synthesized by a one-step method at room temperature and pressure. The surface morphology and chemical structure of Fe-ACMC were characterized by SEM-EDS, XRD, BET, FT-IR, XPS, and ζ-potential. Both Fe3+ and APTES adsorbed onto the CMC surface. The optimum pH for arsenate [As(V)] adsorption was 3–9 with removal efficiency > 99%. The adsorption of As(V) onto Fe-ACMC could reach equilibrium within 25 min with the maximum adsorption capacity of 84.18 mg g–1. The pseudo-second-order model (R2 = 0.995) fitted well the kinetic data, while the Freundlich model (R2 = 0.979) well described adsorption isotherm of As(V) on Fe-ACMC. The co-existing anions (NO3–, CO32–, and SO42–) exhibited a slight impact on the As(V) adsorption efficiency, whereas PO43– inhibited As(V) adsorption on Fe-ACMC. The real applicability of Fe-ACMC (0.8 g L–1) was achieved to remove ca. 10.0 mg L–1 of As(V) from natural waters to below 0.05 mg L–1. The regeneration and reuse of Fe-ACMC for As(V) adsorption were achieved by adding 0.2 mol L–1 HCl, whereas the adsorption capacity decreased after 5 cycles. The main adsorption mechanism of As(V) on Fe-ACMC was attributed to electrostatic attraction and inner-sphere complexation between –NH2···Fe3+ and As(V). The dynamic adsorption of As(V) onto Fe-ACMC was investigated in a fixed-bed column. Thomas model was the most suitable model to elucidate the dynamic adsorption behavior of As(V). The loading capacity of Fe-ACMC packed column for As(V) was 47.04 mg g–1 at pH 7 with an initial concentration of 60 mg L–1, flow rate of 3 mL min–1, and bed height of 0.6 cm. The excellent performance of Fe-ACMC for adsorption makes it a good candidate for a wide range of applications.