Removal of lead ions onto potassium-type fine-grained zeolite prepared from dry or wet milling treatment

Potassium-type zeolite (KZ) was prepared from coal fly ash by hydrothermal activation treatment using potassium hydroxide solution and potassium-type fine-grained zeolite was prepared by dry milling (KZ-D) or wet milling (KZ-W). The effects of the different treatments on the Pb²⁺ adsorption performance were assessed. KZ-W resulted in a much smaller particle diameter (0.61 ± 0.12 µm) than KZ-D (1.4 ± 0.48 µm) and KZ (6.5 ± 0.49 µm). KZ-W also realized a higher pore volume, mean pore diameter, and specific surface area, than KZ-D and KZ. Additionally, KZ-W realized a greater Pb²⁺ adsorption capacity (242.6 mg/g) than KZ (195.3 mg/g) or KZ-D (188.9 mg/g). The adsorption phenomena were fitted to the Freundlich and Langmuir models to clarify the Pb²⁺ adsorption mechanism, and then both models showed a good fit to the experimental data (the correlation coefficients of 0.914–0.996 for Freundlich model and 0.897–0.981 for Langmuir model). Additionally, the ion exchange capability, elemental distribution, and binding energy before and after adsorption were analyzed. The results indicated that the physicochemical characteristics of the tested adsorbent surface affected the Pb²⁺ adsorption capacity in the aqueous phase. According to kinetics, the pseudo-second-order model matched the experimental data (the correlation coefficients of 0.996–0.999). The samples also demonstrated selective adsorption of Pb²⁺ in a binary solution. The results demonstrated that KZ-W can effectively remove Pb²⁺ from the aqueous phase and that it may be a useful tool for preventing contamination of water bodies.