Oxidation of Rhodamine B in aqueous medium in ambient conditions with raw and acid-activated MnO2, NiO, ZnO as catalysts

• Oxides, MnO2, NiO and ZnO, were used in oxidation of Rhodamine B dye in water.
• FTIR, XRD, SEM, surface area, CEC characteristics of the materials were measured.
• The catalysts could achieve almost total oxidation of the dye in aqueous medium.
• Oxidation was possible at ambient temperature and pressure varying other parameters.
• Reaction scheme for mineralization of the dye to innocuous products is proposed.

Various catalysts have been utilized for wet oxidation of organic compounds in water. Rhodamine B is a cationic xanthene dye, used in a large number of industries and is considered as an undesirable chemical in water. In the present work, commercially available metal oxides, MnO2, NiO and ZnO, and those activated by treating with 1.0 N H2SO4 were used to oxidize the dye in water to innocuous compounds. The catalysts were characterized with FTIR, XRD, SEM, cation exchange capacity and BET surface area, pore volume and pore size distribution measurements. Oxidation was carried out in a batch reactor at ambient temperature and pressure under different conditions of pH, reaction time, dye concentration, catalyst loading, and temperature. Acid-activated MnO2 was the best catalyst with almost 100% Rhodamine B oxidation (dye 1.0 mg/L, catalyst loading 2.5 g/L). The catalysts could be recovered and reused. Oxidation followed first order kinetics and a reaction mechanism was proposed based on analysis of the products.

Rhodamine B dye in water was oxidized under ambient conditions with commercial MnO2, NiO and ZnO in a batch reactor with pH, reaction time, dye concentration, catalyst loading, and temperature as the experimental variables. Acid-activated MnO2 could achieve 100% Rhodamine B oxidation at a concentration of 1.0 mg/L with a catalyst loading of 2.5 g/L. The catalysts could be recovered and reused.Figure optionsDownload high-quality image (48 K)Download as PowerPoint slide