Utilization of agricultural waste adsorbent for the removal of lead ions from aqueous solutions

This work investigated the potentiality of using chemically modified onion skin waste (CMOSW) as an adsorbent for the removal of lead ions (Pb2+) from an aqueous solution. The material properties were characterized using techniques, such as Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The effects of adsorbent dosage, contact time, pH and initial Pb2+ concentration on the removal efficiency were investigated by experimental tests. The experimental data were analysed by the Langmuir and Freundlich isotherms, while kinetic data obtained at different concentrations were analysed using a pseudo-first-order and pseudo-second-order models. A distinct adsorption of Pb2+ was revealed by the SEM results. From the FTIR analysis, the experimental result was corresponded to the peak changes of the spectra obtained before and after the adsorption of Pb2+. The maximum removal efficiency of Pb2+ by the CMOSW was 97.3±0.01% at an optimum CMOSW dosage of 1.4 g/L, contact time of 120 min and solution pH of 6.0. Experimental data obtained fitted well with the Freundlich isotherm model. The kinetics of the Pb2+ adsorption by CMOSW appeared to be better described by the pseudo-second-order model, suggesting the chemisorption mechanism dominance