Cadmium removal and recovery from aqueous solutions by novel adsorbents prepared from orange peel and Fe2O3 nanoparticles

An agricultural waste-orange peel powder (OPP) was successfully modified into a novel magnetic nanoadsorbent (MNP-OPP) by co-precipitating it with Fe3O4 nanoparticles (MNP) for cadmium ion removal from aqueous solutions. Characterization of MNP-OPP by FTIR, SEM, XRD, TEM and VSM revealed the covalent binding of hydroxyl groups of MNP with the carboxyl groups of OPP, and further confirmed its physico-chemical properties favorable for metal binding. The cadmium adsorption onto MNP-OPP, MNP and OPP was tested under different pH, ionic strength, natural organic matter, adsorbate concentration, contact time and temperature conditions. Results revealed a faster kinetics and efficiency of MNP-OPP in comparison to those of MNP and OPP and further confirmed a complexation and ion exchange mechanism to be operative in metal binding. The adsorption equilibrium data obeyed. the Langmuir model and the kinetic data were well described by the pseudo-second-order model. Thermodynamic studies revealed the feasibility and endothermic nature of the system. Breakthrough capacity from column experiments, adequate desorption as well as reusability without significant loss of efficiency established the practicality of the developed system. Cadmium removal was achieved at 82% from a simulated electroplating industry wastewater. The experimental results reveal the technical feasibility of MNP-OPP, its easy synthesis, recovery, economic, eco-friendly and a promising advanced adsorbent in environmental pollution cleanup. (C) 2011 Elsevier B.V. All rights reserved.