Evaluation of using clinoptilolite as a filter in drinking water wells for removal of lead (small-scale physical sand box model)

In this study, clinoptilolite was used in batch and sand box model experiments to investigate the uptake efficiency of lead from contaminated groundwater in Fashafuye Plain. Surface properties, structure, and composition of adsorbent were investigated using XRF, XRD, SEM, and BET. Based on BET, clinoptilolite has a surface area of 38.8 (m²/g) and mean-value pore size of 17.97 nm. On account of the pH variability in the Fashafuye plain, batch testing was conducted in pH = 6, 7, and 8 with various concentrations (1, 1.5, 3.5, 6, 8.5, 10 and 12.5 mg/L). The maximum uptake efficiency, 96.3 %, was obtained with clinoptilolite dose of 0.05 g, pH = 6 at 328 K within 90 min, corresponding to 47.4 mg/g of adsorption capacity. The Freundlich isotherm was used to predict multilayer lead adsorption on the heterogeneous area of clinoptilolite. The desirable kinetic model for clinoptilolite is the pseudo-2nd-order equation. The thermodynamic parameters showed that lead adsorption on clinoptilolite were endothermic and spontaneous. Based on column tracer tests, the values of dispersivity were calculated 90.3 and 10 cm for Site no. 2 and no. 9, respectively, indicating some preferential flow and scale-dependent dispersion. The amount of drawdown in sand box model experiments is lower in Site no. 2 than in Site no. 9, which is due to sediment permeability. The real contaminated groundwater tests showed that clinoptilolite was successful in absorbing lead from polluted groundwater and removal efficiency in batch experiments and sand box models were more than 85 and 25 %, respectively, due to shorter contact time in sand box model.