Decolorization and Mineralization of Rhodamine B in Aqueous Solution with a Triple System of Cerium(IV)/H₂O₂/Hydroxylamine

Hydroxylamine (HA) can react with hydrogen peroxide (H₂O₂) to generate hydroxyl radical (HO^•), but the reaction rate between them is very slow (2.2 × 10^-4 M^-1 s^-1). We propose a new system to accelerate the formation of aminoxyl radical (NH₂O^•) by the addition of cerium [Ce(IV)] to induce the continuous production of HO^• through reaction with H₂O₂. We also investigate the decolorization and mineralization of rhodamine B (RhB) and mechanism in the Ce(IV)/H₂O₂/HA system. The initial pH plays a significant role in decolorization of RhB. In this work, observation of the rapid decolorization process after 60 min revealed that approximately 80% of RhB was degraded at the initial pH of 4.0. The HO^• radicals were considered as the primary reactive oxidant in the system, during its investigation through coumarin capturing, benzoic acid capturing, and radical quenching experiments. The results of the present study suggest that the addition of Ce(IV) can greatly enhance the production of HO^•, and the rapid decolorization and mineralization of RhB can occur through the Ce(IV)/H₂O₂/HA system at acidic pH conditions.