Efficient removal of piperazine by catalytic wet air oxidation using RuNiCe/γ-Al2O3-activated carbon†

Abstract

The effective degradation of industrial wastewater containing high concentrations of chemical oxygen demand (COD) and ammonia nitrogen (NH₃-N) is a critical challenge in industrial production. The RuNiCe/AAC catalyst prepared via impregnation and demonstrated a remarkable 99% efficiency rate in the catalytic wet air oxidation (CWAO) of industrial piperazine wastewater for removal. Analysis reveals uniform dispersion of nanometal particles across the carrier's surface and pores. Noble and transition metals regulate chemisorbed oxygen on the catalyst surface, facilitating redox reactions. The strong Ce–Ni interaction promotes the reduction of Ce⁴⁺ during CWAO, inducing reversible valence state changes. This enables electron transfer from high-binding-energy Ni to lower-binding-energy Ru, fostering a synergistic interaction that enhances reaction rate and catalyst stability. The catalyst promotes the generation of hydroxyl radicals from dissolved oxygen, which attack piperazine, leading to heterocyclic ring opening and conversion to N-acetylethylenediamine. Subsequent N–C bond cleavage produces formaldehyde, ethanedioic acid, and ethylenediamine, ultimately achieving complete piperazine mineralization via diverse degradation pathways. This study further advances the research progress of efficient degradation of ammonia-nitrogen organic wastewater and provides new insights into the structural design of non-homogeneous catalysts for CWAO.