Arsenate removal by chitosan iron oxyhydroxide beads: Preparation, characterization, and adsorption studies

This study compared arsenic removal from drinking water by two different adsorbents: iron-im-pregnated chitosan beads (Fe-ICB) and iron-doped chitosan beads (Fe-dCB). Scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared, and Raman spectroscopy were applied to characterize the materials produced. The As(V) adsorption capacity of both types of materials was evaluated by batch tests, followed by a column test using the most promising material. The XRD and the Raman spectroscopy confirmed the presence of 2-line ferrihydrite in the produced Fe-dCB, and no specific iron oxy-hydroxide was identified in the Fe-ICB. Both types of materials followed either the Langmuir or the Freundlich isotherm adsorption models. The Fe-dCB were more efficient in removing As(V) than the Fe-ICB. The actual maximum capacity of the produced Fe-dCB ranged from 0.27 to 0.61 mg/g under the conditions tested (concentration: 1 mg/L; pH: 7.0; 100 rpm). The Fe-dCB with the better adsorption capacity at low concentrations (<0.1 mg/L) were used in a column test using an As(V) influent concentration of 0.060 mg/L. The Fe-dCB produced close to 91,000 BVs, meeting the standard for drinking water (0.01 mg/L). Therefore, the material exhibits promising adsorbent properties for filtration applications with low arsenic concentrations.