Iron oxide nanoparticles stabilized by lignocellulosic waste as green adsorbent for Cr(VI) removal from wastewater

Abstract

Magnetite nanoparticles and magnetite-pine cone nanocomposite were prepared and applied in the adsorption of hexavalent chromium from water. Pine cone powder stabilized the nanoparticles and acted as a support while simultaneously introducing functional groups which improved metal adsorption. The nanocomposite retained the nanoparticles magnetic properties while improving chromium adsorption efficiency. Adsorption of hexavalent chromium on both materials was pH and concentration dependent with the most efficient adsorption occurring at pH 2 and 75 mg/L. On both materials, chromium adsorption was spontaneous with Gibbs free energy values of −19.2 kJ mol−1 to −23.7 kJ mol−1 and −18.0 kJ mol−1 to −24.2 kJ mol−1 for nanoparticles and nanocomposite respectively between 298 K and 319 K. The changes in enthalpy and entropy were determined to be 44.4 kJ mol−1, 212.7 J K−1 mol−1 and 78.3 kJ mol−1, 323.3 J K−1 mol−1 for the prepared nanoparticles and nanocomposite respectively.