Efficacy of Iron-Based Nanoparticles and Nanobiocomposites in Removal of Cr3+

This paper discusses the efficacy of zero-valent iron nanoparticles (ZVIN), magnetic iron oxide nanoparticles (MIN), zero-valent iron nanoparticles/tea waste composite (ZVIN-TW), magnetic iron oxide nanoparticles/tea waste composite (MIN-TW), zero-valent iron nanoparticles/sugarcane bagasse composite (ZVIN-SB) and magnetic iron oxide nanoparticles/sugarcane bagasse composite (MIN-SB) in the removal of trivalent chromium ions. The effect of pH, adsorbent dosage, time, and initial metal ion concentration on removal efficiency was studied. The maximum chromium uptake was obtained when the pH, adsorbent dosage, and initial metal ion concentration were respectively 6, 0.1 g/100 mL, and 250 mg/L. The experimental uptake capacity of ZVIN, MIN, ZVIN-TW, MIN-TW, ZVIN-SB, and MIN-SB was found to be 231.19, 232.59, 219.94, 232.08, 244.18, and 245.68 mg/g, respectively. The experimental data fitted well with Langmuir isotherm (Type I) and pseudo-second-order kinetics. The activation energy analyzed using a D-R isotherm was found to be 12.34, 12.65, 12.12, 12.95, 14.40, and 14.22 kJ/mol respectively for ZVIN, MIN, ZVIN-TW, MIN-TW, ZVIN-SB, and MIN-SB. The results of intraparticle diffusion and Boyd's study showed that film diffusion and chemical reaction controlled the overall adsorption process. Ion exchange, hydrogen bonding, and electrostatic attraction were found to be the three major mechanisms involved in the adsorption. Investigation on temperature variation confirmed the adsorption process. The presence of cations and anions affected the adsorption response. The nanoparticles and nanobiocomposites were characterized by point of zero charge (pH(pzc)), ultraviolet visible spectroscopy, BrunauerEmmett- Teller surface area analysis, X-ray powder diffraction study, Fourier transform infrared (FTIR) spectral study, scanning electron microscopy, energy dispersive X-ray spectroscopy analysis, atomic force microscopy (AFM) studies, and vibrating sample magnetometer (VSM) analysis. AFM images showed a triangular morphology in ZVIN and MIN for particle sizes of 296.8 and 263 nm, respectively. FTIR study revealed hydroxyl, carboxyl, iron, and other compounds to be the functional groups. VSM analysis showed the superparamagnetic nature of MIN, MIN-TW, and MIN-SB. Nanoparticles and nanobiocomposites were found to be effective adsorbents. (C) 2016 American Society of Civil Engineers.