Adsorption behavior of lead onto a new class of functionalized silica gel

In this study the surface of silica gel was functionalized with 2-thiophenecarbonyl, 2-furoyl and l-proline. The synthesized materials were characterized by fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) with energy dispersive X-ray analyzer (EDX). Batch adsorption studies were carried out to analyze the adsorption of the lead ion from aqueous solution. The factors influencing % adsorption of Pb(II) onto the silica gel and functionalized silica gel such as initial pH value of the Pb(II) ion solution, adsorbent dose, initial Pb(II) ion concentration, contact time and temperature were investigated. Langmuir and Freundlich isotherm models were used to determine the isotherm parameters associated with the adsorption process. Kinetic data were analyzed considering pseudo-first order, pseudo-second order and intraparticle diffusion approaches. The latter two mechanisms seem to be significant in the rate-controlling step. Negative values of Gibb's free energy change (ΔG°) showed that the adsorption was feasible and spontaneous and negative values of enthalpy change (ΔH°) confirmed exothermic adsorption.