Rapid production of hydroxysodalite from a clay-based waste through microwave-assisted technique for treatment of wastewater contaminated with zinc cation

In the current work, the cabbage-like hydroxysodalite powder was produced from a clay-based waste deposited in the landfill of raw vegetable oil refinery through the microwave-assisted technique to treat the wastewater discharged from a zinc extraction industry. The selected waste was a Ca-bentonite, mainly containing montmorillonite, illite, and kaolinite which contaminated with the vegetable oil components. The effects of microwave irradiation power, and time on crystalline structure of products as well as uptake of heavy metal ions like zinc, cadmium, nickel, and aluminum were studied in details. The experimental results showed that the partial recrystallization of hydroxysodalite under the irradiation power of 200 W within 10–15 min contributes to the enhancement of adsorption efficiency. The maximal uptake of heavy metal ions was obtained in the relative crystallinity range of 22.5–43.0%. The prepared adsorbent possessed the higher efficiency, 94.0%, for the immobilization of Zn ²⁺ from the concentrated wastewater, 413 mg L ⁻¹. The competitive adsorption of Cd ²⁺, Ni ²⁺, and Al ³⁺ ions over the hydroxysodalite was extremely dependent on the ion concentration. Furthermore, the adsorption kinetics of Zn ²⁺ over the hydroxysodalite particles follows the pseudo-second-order (PSO) model, indicating the chemical nature of treatment process. The equilibrium data were fitted by the Langmuir isotherm, confirming the homogenous, and monolayer adsorption. The presented route for the production of hydroxysodalite is facile, and rapid in comparison to hydrothermal method.