Adsorption Behaviour of Ethylene Vinyl Acetate and Polycaprolactone-Bentonite Composites for Pb2+ Uptake

The results presented in this work show that the hydrophobic thermoplastics, namely ethylene vinyl acetate (EVA) and polycaprolactone (PCL), could be good matrices for the synthesis of polymer/bentonite composites via the melt-blending method for the removal of heavy metals from water. The hydrophobic nature of the polymers was countered by using dry Na2SO4 to form large free-volume pores. These pores, formed after the removal of the Na2SO4 by washing, improved the contact ratio between bentonite particles and Pb2+ ions. The composites were able to achieve up to 78% Pb2+ removal at an initial concentration of 200 mg/L in 10 h with a clay loading of 3% (w/w). The results confirmed that the PCL/bentonite composite was more effective and efficient in the adsorption of Pb2+ than the EVA/bentonite composite. The experimental data for both composites followed Langmuir and Freundlich models. The uptake of Pb2+ was found to be a result of a chemical interaction between the heavy metal, silanol (Si-OH) and aluminol (Al-OH) groups. The adsorption of Pb2+ onto the composites was found to follow pseudo-first-order kinetics and the results supported a monomolecular reaction mechanism.