Kinetic and equilibrium studies of the removal of Pb2+ from aqueous solutions using Na2SO4-EVA/Cloisite® 20A composite

The present work describes the suitability of Na2SO4 to improve the wetability of a hydrophobic composite, ethylene vinyl acetate/Cloisite® 20A, to remove Pb2+ ions from aqueous solutions through adsorption. The composite was synthesized via melt-blending method. Scanning electron microscopy showed that suspending the composite in de-ionized water improved porosity resulting from the removal of Na2SO4. X-ray diffraction showed that the use of Na2SO4 improved the amorphous nature of the composites and hence increased wetability. The holes on the composite improved the contact area between Cloisite® 20A particles and Pb2+ ions. Equilibrium adsorption was achieved in 8 h with a 90% Pb2+ ion removal from synthetic wastewater. Kinetic and equilibrium models were applied to determine the type of adsorption mechanism involved. The results showed that the sorption of Pb2+ was found to be mainly based on physical interactions and ion-exchange mechanisms. It was established that the adsorption follow pseudo second-order rate equation and intraparticle diffusion was the rate determining step. The results showed that sorption mechanism assumed intraparticle diffusion implying that porous structure of the adsorbent influenced diffusion.