Medium-entropy metal-organic framework-integrated catalytic distillation system for near 100% urea removal.

Abstract

Urea is a pervasive nitrogenous pollutant that must be effectively eliminated from wastewater to prevent ecological damage, but existing treatment technologies remain inadequate. Here we show an integrated urea oxidation reaction-membrane distillation system that simultaneously achieves near-complete urea removal and resource recovery. The system employs a medium-entropy metal-organic framework (ME-MOF) electrocatalyst, which requires only 1.36 V versus the reversible hydrogen electrode (RHE) to achieve 100 mA cm^-2 for urea electrooxidation. And, it operates stably for 1,000 h at a total current of 1 A, enabling the removal of 99.7% urea from concentrated streams to meet the stringent U.S. Environmental Protection Agency (EPA) emission standard for fertilizer wastewater (<35 mg L^-1 NH₃-N). Operando characterizations reveal that entropy-stabilized multimetal sites enhance charge transfer and suppress Ni leaching. Furthermore, comprehensive life-cycle and techno-economic analyses demonstrate the system's competitive environmental impact compared with conventional anaerobic ammonium oxidation (anammox) processes, achieving economic viability with a net profit of $2.9 per m³ of effluent treated, in contrast to a loss of $0.63 per m³ for anammox treatment.