Efficiency of natural zeolite in the removal of heavy metals lead, cadmium, and cobalt using a fixed-bed adsorption column in Varamin aquifer (Iran, Tehran Province)

In the last few decades, pollution caused by heavy metals in groundwater sources has been recognized as a major environmental problem. In this research, the ability of clinoptilolite zeolite as a low-cost adsorbent for the removal of heavy metal ions specifically lead, cadmium, and cobalt (which have a higher concentration than the permissible limit of drinking standard indicators in the Varamin region) in continuous absorption systems was investigated. XRD, XRF, ICP-MS, BET, and FESEM tests were carried out to check the characteristics of the absorbent materials, to determine the crystal structure, type, and percentage of minerals, and to check the concentration of elements. Equilibrium sorption studies were carried out using discontinuous experiments to analyze the sorption capacity of clinoptilolite. Langmuir and Freundlich adsorption models were fitted to the data and the effect of the initial concentration of the solution at different pH was determined using adsorption experiments to validate the measured data, fitting statistical parameters such as root mean square error (RMSE) and regression coefficient (R2) were used and the Langmuir model showed a better fit to the absorption data of the above elements. In continuous experiments, the height of the fixed layer of clinoptilolite was 40 cm, the column diameter was 4 cm, the particle size was 0.42 to 0.84 mm, and the volumetric flow rate, was 1.65 ml/min. The breakthrough curves generated fromthe laboratory data were in good agreement with the Thomas model and Yoon-Nelson model. This research demonstrates that clinoptilolite can be an effective adsorbent for the removal of heavy metals such as lead, cadmium, and cobalt and has the potential to be used in the development a new in-situ remediation approach for the removal of these metals from polluted groundwater.