Removal of Pb(II) in Aqueous Solutions Using Synthesized Zeolite X from Ecuadorian Clay

Abstract

Zeolite X was synthesized from clay using the alkaline fusion method and hydrothermal treatment to remove Pb(II) in aqueous solutions. Clay and zeolite were characterized through X-ray diffraction and fluorescence (XRD, FRX), as well as through specific surface area (SSA). The adsorbents were prepared as cylindrical extrudates using clay and a clay-zeolite combination (60-40%, respectively). The effects of pH, isotherm, and adsorption kinetics on the removal of Pb(II) in solutions of 80 mg Pb(II)/L were studied. It was possible to obtain a zeolite X from clay, with an SSA of 376 m2/g, 30 times greater than that of clay (12 m2/g). In the combined extrudate was present the zeolitic structure, with an SSA 12 times higher compared to the clay extrudate. The adsorption capacity, at 30 °C and V/m ratio of 1 g/L, is almost double compared to the clay extrudate (24 mg Pb(II)/g vs. 13 mg Pb(II)/g). Adsorption follows second order kinetics, and the Langmuir isotherm equation showed a good fit with the experimental equilibrium data for the two extrudates. The Webber-Morris and Bangham-Burt’s models suggest that pore and film diffusion influence the kinetic mechanism.

Enhanced Removal of As(V) and Pb(II) from Drinking and Irrigating Water Effluents Using Hydrothermally Synthesized Zeolite 5A

“…The Langmuir isotherm model assumes that only one solute species will occupy an active site on the homogeneous surface of the adsorbent [30], and that there are no interactions between adsorbed species [32]. Equation (10) represents the above-mentioned model:…”

“…This model assumes that, due to the diversity of adsorption sites on the zeolite surface, the surface of the adsorbent is multilayer and not homogeneous [28]. The heterogeneous character of the 18PZ5A surface is also confirmed by the parameter n; if it is less than 1, the adsorption is chemical, and if it is greater than 1, the adsorption is physical and favorable [32]. A value of 3.45 was obtained, indicating a favorable and heterogeneous physisorption condition.…”

“…On the other hand, the Temkin isothermal model also had a relatively high value of R 2 compared to the others; this model describes the relationship between the adsorbent and the heat of adsorption [67]. Another value to consider is b T , which makes reference to the high iteration between adsorbate and adsorbent [32]. After evaluating the isotherm models by various criteria, we observed that R 2 is the only parameter that repeats and allows comparison with the models, so previously described statistical equations were used to evaluate modeling errors [38] such as the BIC and RSS.…”