Utilization of biosynthesized silica-supported iron oxide nanocomposites for the adsorptive removal of heavy metal ions from aqueous solutions

Abstract The present study deals with heavy metal ion removal from synthetic contaminated water using biosynthesized silica-supported iron oxide nanocomposites (nano-IOS). Agricultural and garden waste has been utilized to prepare nano-IOS through a green synthesis process. Nano-IOS was characterized by XRD, SEM, FTIR, and zeta potential analysis. The nanocomposites were used to adsorb heavy metal ions viz. Pb2+, Cd2+, Ni2+, Cu2+, and Zn2+ with optimization of reaction constraints including pH, the concentration of heavy metal ion, adsorbent dosage, and contact time in batch mode experiments. The optimized dose of nano-IOS was obtained as 0.75 g/L for adsorption of Pb2+, Cd2+, Ni2+, Cu2+, and Zn2+ (10.0 mg/L) with a contact duration of 70 min. at pH 5.0 for Pb2+, Cd2+, and Cu2+, and 6.0 for Ni2+ and Zn2+. The adsorption behavior of the nano adsorbent was well described by Langmuir adsorption isotherm and pseudo-second order kinetic models indicating chemisorption on the surface of nano-IOS. The adsorption was also found spontaneous and endothermic. Thus, the environmentally benign and bio-synthesized nano-IOS can be utilized as an effective nano-adsorbent for the rapid sequestration of heavy metal ions.