Effective cadmium ion removal from wastewater using glycerol-assisted synthesis and alumina-coated MnNi catalysts derived from mixed metal salts

This study introduces the application of glycerol as an environmentally friendly nucleation and interaction agent in the synthesis of MnNi-based catalysts, utilizing metal salt hydrates of acetate and nitrate, for the first time. A protective alumina (Al₂O₃) coating was incorporated at concentrations of 1 %, 2 %, and 3 % to further enhance the catalyst's efficacy. The catalysts' performance in removing cadmium ions (Cd²⁺) from wastewater was evaluated using a batch reactor. The catalyst with a 2 % Al₂O₃ coating demonstrated optimal performance, achieving complete removal of cadmium within 35 min. Advanced characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis, confirmed improvements in crystallinity, increased surface area, and a favorable alumina-coated NiMnO₃ catalyst structure. These findings elucidate the novel role of glycerol in controlling particle morphology and dispersion, as well as identifying the most effective alumina coating strategy to enhance removal efficiency and extend catalyst lifespan. • A novel MnNi catalyst was synthesized using acetate and nitrate hydrates with glycerol as a green nucleation agent for the first time. • Alumina coatings (1 %, 2 %, 3 %) were applied to enhance stability, morphology, and catalytic performance. • The 2 % Al₂O₃-coated catalyst showed optimal performance, achieving 100 % cadmium ion removal within 35 min in batch reactors. • XRD, FTIR, SEM, TEM, and BET confirmed morphological evolution, porosity, and improved surface area. • A stable coated NiMnO₃ catalyst and controlled nucleation yielded a reusable and high-efficiency catalyst for wastewater treatment.