Highly Selective Removal of toxic metal ions from Wastewater using Yemeni Limestone as a Natural and Low-Priced Adsorbent: behavior and mechanism

The current study examines the use of rock debris leading from mining in the Nakleen zone. The values of these rock wastes must be taken into account in a feasibility analysis, especially in light of potential ongoing mining operations. Treated Limestone obtained from different areas of Yemen was applied to adsorb Cd (II) and Pb (II) from wastewater. Treated limestone samples were characterized using various techniques, via FTIR, XRF, and TGA-DTA. Batch experiments were conducted with varying pH (2–9), Metal ions concentration (10–50 mg/L), stirring time (10–60 min), and limestone dosage (0.1–1.1 g/50 mL). The ICP-OES analysis was applied to determine the removal percentage of the Cd(II) and Pb(II)  ions using the adsorption process. Results show that the limestone was efficient for removing Pb (II) and Cd (II) ions with efficiencies of 99 %, and 98.5 % respectively. The adsorption of Cd(II) and Pb(II) ions onto limestone obeyed the Freundlich model due to electrostatic affinity. The maximum adsorption capacities of Nak-Cd+2 and Nak-Pb+2 after short time are 6.09 and 4.769 mg/g, respectively. This result indicates that the intercalation of several ions with Nak limestone was better suited to Cd+2 ions. The enhancement is attributed to the selectivity of adsorption sites in the Nak sample to Cd+2 ions