Modular Functionalization of Metal-Organic Frameworks for Nitrogen Recovery from Fresh Urine

Nitrogen recovery from wastewater represents a sustainable route to recycle reactive nitrogen (Nr). It can reduce the demand of producing Nr from the energy-extensive Haber-Bosch process and lower the risk of causing eutrophication in the meantime. In this aspect, source-separated fresh urine is an ideal source for nitrogen recovery given its ubiquity and high nitrogen contents. However, current techniques for nitrogen recovery from fresh urine require high energy input and are of low efficiencies because the recovery target, urea, is a challenge to separate. In this work, we developed a novel fresh urine nitrogen recovery process with the assistance of modular functionalized metal-organic frameworks (MOFs). Specifically, we employed three distinct modification methods to design and synthesize functionalized MOF-808 derivatives to facilitate our newly developed Nr recovery process. By integrating these functional materials into the treatment process, we achieved an average of 75% total nitrogen reduction and 45% nitrogen recovery with five cycles, each with a 30 min treatment of synthetic fresh urine. The nitrogen recovery process developed in this work can serve as a sustainable and efficient nutrient management that is suitable for decentralized toilet wastewater treatment. This work also provides a new perspective of implementing versatile advanced materials for water and wastewater treatment.