Synthesis of Starch-Iron Oxide Nanocomposite by Coprecipitation Method and Its Use for Adsorption of Nickel and Cadmium from Wastewater

Backgrounds & objectives: Contamination of the environment by heavy metals, pollute water and agricultural products. The aggregation of these metals will cause various diseases for human. Therefore, it is important to study how to make them safe. The purpose of this study is to evaluate the efficiency of starch-iron oxide nanocomposite in removing two heavy metals, nickel and cadmium, from wastewater. Methods: In this study, an attempt was made to use starch as natural polymer to prepare starch-iron oxide nanocomposites. Its structural properties and functional groups were investigated using scanning electron microscopy (FE-SEM), elemental decomposition (EDX) and Fourier transform infrared (FT-IR) spectroscopy. Then, the efficiency of starch-iron oxide nanocomposite as an adsorbent for the removal of heavy metals including nickel and cadmium from continuous synthetic solutions was investigated. For this purpose, aqueous solution with a concentration of 1000 mg/l of nickel and cadmium metals was prepared. The effect of adsorbent amount, pH and contact time on the removal process was studied. Langmuir, Freundlich and Temkin isotherm models were used for study of procedure isotherm. Results: The synthesized nanocomposite has good efficiency in removing nickel and cadmium. Maximum uptake of heavy metal ions was occurred at pH=4, using 0.05g of starch-iron oxide nano-composite from 20 ml aqueous solutions content 10 ppm of two studied ions. The adsorption efficiencies were found to be pH dependent which because of ionic interaction, by increasing pH value the removal increased. The cadmium adsorption process follows the Freundlich equation, while the nickel metal does not follow any of the equations. Investigations of kinetics of the process were performed and showed pseudo second-order model has the best correlation for adsorption procedure. Conclusion: In general, this investigation showed that, the fabricated adsorbent has high efficiency for removal of nickel and cadmium ions. But application of this method in the industry should be economically evaluated.