Adsorption Equilibrium and Kinetics of Pb(II) from Aqueous Solution by Modified Walnut Shell

The adsorption equilibrium and kinetics of the removal of Pb(II) from aqueous solution by walnut shell modified with acrylic acid (MWNS) were investigated in the temperature range of 288-308 K. Thus, the samples of MWNS with different graft yields (3.65, 10.45, 18.49, and 19.66 wt %) were prepared by reacting walnut shell (WNS) with acrylic acid. The effects of graft yield, adsorbent dose, pH, contact time, and temperature on the adsorption of Pb(II) were studied. Both WNS and MWNS-4 (19.66 wt %) were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) analyses. Adsorption kinetics were examined using pseudo-first-order, pseudo-second-order model, Elovich kinetic model, intraparticle diffusion model, and Boyd kinetic model. The adsorption isotherm data were better interpreted by Langmuir isotherm model, and the maximum adsorption capacity for Pb(II) was 210.14 mg g(-1) at 308 K. The energy disperse spectroscopy (EDS) analysis was applied to verify the adsorption process. The thermodynamic parameters Delta G, Delta H, and Delta S were determined. Recycling property of MWNS-4 was studied. (C) 2016 American Institute of Chemical Engineers Environ Prog, 35: 1724-1731, 2016