Kinetics, mechanism, isotherm and thermodynamic studies of liquid phase adsorption of Pb2+ onto wood activated carbon supported zerovalent iron (WAC-ZVI) nanocomposite

Abstract

Abstract The kinetics, mechanism, isotherm, and thermodynamics of adsorption of Pb2+ onto wood-activated carbon-supported zerovalent iron (WAC-nZVI) nanocomposite was successfully studied. WAC-nZVI was characterized by a combination of spectroscopic and analytical techniques (BET, PZC, FTIR, SEM, and EDX). BET surface area was 101.50 m2/g and BJH Adsorption average pore diameter 116.73 Å. The adsorption of Pb2+ studied in batch process depends on various operational parameters ranging from effect of pH to ionic strength. Kinetics data were best described by pseudo-second-order model based on high initial adsorption rate, h2 (166.67 mgg−1 min−1) and correlation coefficient (R2 > 0.99). The mechanism was controlled by both external and intraparticle diffusion models confirmed by Bangham and Boyd models. Equilibrium data were fitted to seven isotherm models. The Langmuir monolayer adsorption capacity (77.52 m2/g) surpassed those previously investigated for adsorption of Pb2+ onto nanoadsorbents. Validity of kinetics and isotherm models was studied using three statistical models. Post-adsorption characterization by SEM, EDX, and FTIR confirmed the presence of Pb2+ on the loaded-WAC-nZVI. Thermodynamic parameters (∆Ho, ∆So, ∆Go) confirmed the feasibility, spontaneity, and randomness of the adsorption process. This study revealed a great potential of novel WAC-nZVI in effective removal of Pb2+ from waste water.