Investigating the Effectiveness of Natural Zeolite (Clinoptilolite) for the Removal of Lead, Cadmium, and Cobalt Heavy Metals in the Western Parts of Iran's Varamin Aquifer

This study investigates the ability of natural clinoptilolite zeolite as a low-cost adsorbent for removing heavy metal ions, specifically lead, cadmium, and cobalt, from the aquifer in the Varamin region in a discontinuous absorption system. Characterization techniques such as XRD, XRF, ICP-MS, BET, and FESEM were used to analyze the zeolite. Batch experiments were conducted to determine the adsorption capacity of clinoptilolite at three pH values (6, 7, and 8) and a constant temperature of 25 °C by adding 0.05 g of adsorbent to 50 mL solutions containing different concentrations of Pb²⁺, Cd²⁺, and Co²⁺ ions. The remaining metal concentrations in the solutions were measured. The Langmuir and Freundlich adsorption models were fit to the data and the effect of initial solution concentration at different pH values was determined. The results indicated that the adsorption capacity of clinoptilolite increased with an increasing initial concentration of elements in the solution, with a higher capacity for removing lead and cadmium compared to cobalt. The root means square error (RMSE) and coefficient of determination (R²) were used to evaluate and validate the data and concentration of ions calculated by the mathematical models. Both models were able to adequately explain the adsorption of metal ions on the zeolite, but the Langmuir model had a better fit with the adsorption data. This research demonstrates that clinoptilolite can be an effective adsorbent for removing heavy metals and has potential for use in developing a new in-situ remediation approach for removing these metals from polluted groundwater.