Removal of heavy metals from aqueous solution by limestone

This study focused on the removal of Pb(II), Cd(II), Cu(II), and Zn(II) using reagent solutions by natural limestone in a batch system. The sorbent, collected from the Late Cretaceous limestone beds, Tunisia, was characterised by X-ray diffraction (XRD), chemical analysis (XRF) and infrared spectroscopy (FTIR). XRF showed that the studied limestone contained high amount of calcium carbonates. XRD confirmed the presence of quartz along with the sharp peaks of calcite. FTIR spectra indicated that limestone was mainly composed of calcite, confirming the results of XRD and XRF analyses. Preliminary adsorption tests indicated that high removal efficiency could be achieved by limestone. The presence of impurities enhanced the adsorption capacity. Kinetic experiments showed that the sorption of metal ions best fitted the second order kinetic model with equilibration time of 60 min. These results suggested that the Campanian-Maastritchian limestone could be used for the removal of toxic metals from wastewaters.