Sustainable and Green Synthesis and Characterization of Nano MnOx-CeO2 Materials; Removal and Kinetic Studies of Carmoisine Dye

Abstract

Sustainable and green synthesis approaches were used to prepare nano-disperse MnO_x-CeO₂ photo-catalysts (MnO_x-CeO₂⁵⁰⁰ and MnO_x-CeO₂⁷⁰⁰). These were characterized by XRD, TEM, low-temperature nitrogen adsorption and XPS techniques. These materials were used to remove carmoisine azo dye from water. XRD studies established the formation of phase Mn-Ce-O solid solutions based on cerium dioxide, as well as the presence of Mn₂O₃ and Mn₃O₄. The particle sizes of MnO_x-CeO₂⁵⁰⁰ and MnO_x-CeO₂⁷⁰⁰ were 8–10 and 20–30 nm while the specific surface areas were 128 and 54 m²/g. According to XPS the content of high-energy oxygen (responsible for catalytic activity) decreased at high temperatures. The efficiency of removing carmoisine azo dye in the presence of ammonium persulfate was about 93% in a neutral medium with MnO_x-CeO₂⁵⁰⁰ material. Recycling was carried out and MnO_x-CeO₂⁵⁰⁰ material was effective for 89% removal after 20 cycles. The 89% removal capacity of MnO_x-CeO₂⁵⁰⁰ material after 20 recycles made it an economic one from an industrial point of view.