Kinetic and equilibrium studies of the removal of Pb~(2+) from aqueous solutions using Na_2SO_4-EVA/Cloisite~® 20A composite

摘要

The present work describes the suitability of Na_2SO_4 to improve the wetability of a hydrophobic composite, ethylene vinyl acetate/Cloisite~® 20A, to remove Pb~(2+) 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 Na_2SO_4. X-ray diffraction showed that the use of Na_2SO_4 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 Pb~(2+) ions. Equilibrium adsorption was achieved in 8 h with a 90% Pb~(2+) 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 Pb~(2+) 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.