Evaluating the ability of Iranian natural zeolite to remove lead from polluted groundwater in Fashafuye plain

The removal efficiency of lead from groundwater in Fashafuye Plain was investigated by two types of Iranian zeolites (type A and B) in batch-mode experiments. Surface properties, structure, and composition of both zeolites were analyzed and it was found that both were clinoptilolite but type B contained impurities such as gypsum and halite. Electron beam methods showed that zeolite type B had a more porous structure and a larger mean pore diameter. Because of the variation in pH in the Fashafuye plain for the both zeolites, batch experiments were conducted in pH = 6, 7, and 8, with the highest removal efficiency for A and B being approximately 82.3 and 84.2%, respectively, at pH 6 and 298 K within 90 min. The Freundlich model predicted metal ion adsorption behavior accurately and illustrated that multilayer lead adsorption appeared on the inhomogeneous surface of clinoptilolites. The pseudo-2nd-order equation is the best-fitting kinetic model for both zeolites, implying that chemisorption might be involved in the adsorption process. The thermodynamic equilibrium coefficients were calculated, indicating that lead adsorption on the clinoptilolites was endothermic and spontaneous. Adsorbent selectivity for lead was also investigated by adding them to the polluted groundwater from two sites in the Fashafuye plain, with the results revealing that zeolite type B had a higher uptake efficiency than type A.