The effect of surface modification on polyvinyl alcohol-chitosan hydrogels towards the recovery of metals from e-waste

Abstract

Electronic waste poses a huge threat to the environment and health due to the release of toxic metals and coated resins occurred during improper recycling. In this context, a facile approach was employed for the preparation of surface modified hydrogels involving polyvinyl alcohol (PVA) and chitosan (CS) with conducting polymers viz. polyaniline (PANI) and polypyrrole (PPy) to remove the selective Pb(II) and Cd(II) ions from synthetic solution and real-time waste computer printed circuit boards (wPCBs). FTIR spectroscopy clearly revealed the crosslinking effectiveness, identification of functional groups and coating efficiency. The prepared hydrogels were thermally stable up to 500 ºC as determined from thermogravimetric analysis. The surface of PVA-CS hydrogel modified by PANI and PPy showed large amount of active sites to entrap the metal ions as revealed by scanning electron microscopy. Surface area determined by BET analysis for PVA-CS hydrogel coated by PANI and PPy with 299.7 and 264.05 m²/g, respectively exhibits an opportunity to recover huge amount of metal ions. At varied parameters such as surface coating efficiency, contact time and hydrogel dosage, the recovery of toxic metal ions was widely investigated. At an optimized condition, the hydrogels were employed for the successful recovery of selective Pb(II) and Cd(II) ions from the waste PCBs. Kinetic and isothermal models study revealed best fit results for Pseudo second-order and multilayer adsorption by Freundlich isotherm. Hence, the prepared surface modified hydrogels could act as promising adsorbents for the successful recovery of toxic and other precious metals from e-waste.