Modification of ion exchange resin with magnetite for chromium removal

Abstract

A hybrid adsorbent was developed by introducing magnetite nanoparticles (Fe3O4) onto the surface of ion exchange resin (cation and anion exchange resins) to improve the adsorption performance for chromium removal from aqueous solution. A rough surface was observed on the surface of both magnetite-loaded cation resin (IRN77-Fe3O4) and anion resin (IRN78-Fe3O4), revealed by field-emission scanning electron microscope (FESEM). In addition, Fe-O bond was detected on Fourier transform infrared spectroscopy (FTIR) spectra on the surface of both magnetite-embedded ion exchange resins (MIER). From energy-dispersive x-ray spectroscopy (EDX) analysis, 8.2 % and 5.2 % of iron elements was identified on the surface of IRN77-Fe3O4 and IRN78-Fe3O4, respectively. A larger surface area compared to the unmodified resin was detected for MIER by using a Brunauer–Emmett–Teller (BET) surface area analyzer. Batch adsorption tests with chromium ion were performed with both modified and unmodified resins at various conditions. The equilibrium study identified that optimum conditions for Cr(III) and Cr(VI) adsorption were at pH 3, 1 hour reaction time, and 0.3 g of adsorbents. The adsorption capacity for Cr(III) using IRN77-Fe3O4 increased up to 17% with a faster removal rates than IRN 77. On the contrary, the IRN78-Fe3O4 was discovered to have a lower adsorption capacity of chromium (VI) than unmodified resin due to pH change during adsorption. The maximum adsorption capacity of Cr(III) and Cr(VI) removal using IRN77-Fe3O4 and IRN78-Fe3O4 was remarked at 69.2521 and 77.2798 mg/g, respectively. Furthermore, the adsorption kinetics for both resins fitted well to the pseudo-second-order model. Based on the experimental results, it was found that ion exchange and electrostatic attraction were dominant mechanisms for chromium removal. Lastly, sorption-desorption studies were performed to evaluate reusability for both modified resins. The adsorption capacity for both MIER can achieve maximum removal efficiency of more than 90% for five cycles of usage. Modified ion exchange resin with magnetite nanoparticles could be a promising adsorbent in the remediation of chromium and potentially used in actual field applications to remove other heavy metal contaminants.