Synthesis of zeolite-A/Fe3O4/biochar/MOF-5 composite for the defluoridation of drinking water

High concentrations of F⁻in groundwater used for drinking purpose have a serious public health problem in the Rift Valley area of Ethiopia. In this study, the zeolite-A/Fe₃O₄/Biochar/MOF-5 (Z-A/Fe₃O₄/BC/MOF-5) composite was synthesized through the solvothermal method as a mitigation option for the defluoridation of drinking water. The as-synthesized adsorbent was characterized by XRD, BET, FT-IR, and SEM–EDX to identify phase structure, surface area, functional group, morphology, and elemental composition, respectively. The adsorption study of the synthesized composite was started by optimizing the defluoridation parameters. According to these factors, the maximum defluoridation efficiency (96.20%) and defluoridation capacity (28.86 mg/g) were obtained at 10 mg/L of F⁻ initial concentration, 0.6 g/L of adsorbent dose, 12 h of contact time, and pH 3. The Freundlich and pseudo-second-order models are well fitted to explain the adsorption isotherm and kinetic, with R² values of 0.98338 and 0.99722, sequentially. The defluoridation performance of the Z-A/Fe₃O₄/BC/MOF-5 composite was tested on real water samples collected from Kenteri and Ziway town, Ethiopia. Interestingly, this experimental test revealed its high performance, which is 91.92% and 93.29% F⁻ removal efficiency from 12.25 and 8.5 mg/L of F⁻ initial concentration, respectively. The recyclability study also showed the high activity of Z-A/Fe₃O₄/BC/MOF-5 composite in the removal of F⁻ with 93.60, 91.10, 89.00, 86.00, and 74.80% defluoridation efficiency for first, second, third, fourth and fifth cycles, respectively. Thus, the synthesized composite adsorbent can be reused and be a feasible option for the defluoridation of drinking water.