Application of Activated Clay for Improvement of Water Quality in Wire Electric Discharge Machining

抄録

In this study, the availability of activated clay treatment for decreasing the electrical conductivity in the real wire cut water was demonstrated. Activated clay (AC) was prepared, and its characteristics were investigated. The ability to adsorb Zn²⁺ and the removal ability through electrical conductivity were evaluated. It was found that the AC had a montmorillonite-like structure. Its specific surface area, micropore volume, mesopore volume, and macropore volume were 125.0 m²/g, 0.7 μL/g, 172.6 μL/g, and 13.7 μL/g, respectively. The cation exchange capacities at pH 5 and pH 10 were 56.2 and 67.2 cmol/kg, respectively. The effects of temperature, contact time, and pH of the solution on the adsorption of Zn²⁺ were measured. The amount of Zn²⁺ adsorbed by the AC increased with an increase in the adsorption temperature or in the pH. Adsorption isotherms data were fitted to the Freundlich equation compared to the Langmuir equation. Adsorption equilibrium was reached within 30 min, and kinetic data were fitted to the pseudo-second-order model compared to the pseudo-first-order model. Additionally, the AC was proven to effectively suppress the electrical conductivity. The suppression achieved by using washed AC was higher than that obtained by virgin AC. Washing AC with distilled water is useful for removing released ions (SO₄^2-). Therefore, the column treatment packed with washed AC was evaluated in this paper. Finally, washed AC could remove Zn²⁺, resulting in the reduction of electrical conductivity (removal percentage is 47%). These findings provide significant information that can be useful for the removal of Zn²⁺ and reducing the electrical conductivity from wire cut water.