Efficiency of mining rock wastes in the removal of toxic heavy metal ions (Pb²+, Cu²+, and Cd²+) from contaminated water solutions

Abstract Abu Tartur plateau Western Desert of Egypt hosting the largest phosphate mine in the Middle East. Annually, few million tons of carbonates, black shale, siltstone, glauconite and sandstone were generated from Abu Tartur mine operations as rock wastes from the overburden. Phosphatic dolomite (PD) and black shale were collected from mine waste. PD along with a synthesized sodalite-based materials (SBPD) created from calcined phosphatic dolomite (CPD) and black shale were assessed as low-cost adsorbents for the removal of Pb²⁺, Cu²⁺, and Cd²⁺ from synthetic waste water. Heavy metal pollution (e.g., Cd, Pb, Cu) has become a crucial issue worldwide. Among various remediation strategies, adsorption is widely recognized for its environmental sustainability, cost-effectiveness, and operational simplicity.Characterization of both PD, CPD and SBPD was carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). Optimal adsorption conditions including adsorbent dosage, pH, initial metal concentration, and contact time were investigated for Pb, Cu, and Cd. The best performance for SBPD was achieved with a 0.2 g dose for Pb and Cd, while PD showed optimal results at 0.3 g for Pb and 0.6 g for Cu. Both materials demonstrated a preferential removal sequence of Pb²⁺ >Cu²⁺ >Cd²⁺. Kinetic and isotherm models were applied to interpret the adsorption mechanisms, with results confirming that sodalite exhibited higher metal removal efficiency than unmodified phosphatic dolomite.