A novel sustainable N recycling process: Upcycling ammonia to ammonium fertilizer from dilute wastewater and simultaneously realizing phenol degradation via a visible solar-driven PECMA system with efficient Ag2S-BiVO4 photoanodes

Abstract

The selective recovery of NH4+ as N fertilizers from dilution wastewater is a promising but challenging topic. Herein, a novel visible-light driven photo-electrochemical membrane stripping cell (designated “PECMA”) with Ag2S-BiVO4 heterojunction photoanode was proposed to recover ammonium from dilute wastewater, which comprised an anode chamber for organics treatment, intermediate chamber for separating ammonium, cathode chamber for upcycling NH4+ into NH3, and recovery chamber for converting NH3 into (NH4)2SO4. The NH4+ is concentrated by 21.5 times and recovered as (NH4)2SO4 with a concentration of 7103 mg L−1 after 10 cycles. At a current density of 3.86 A m−2, PECMA system achieves excellent NH4+ removal and recovery rates of 97.5 and 37.2 g N m−2 d−1 in 100 mgN L−1 wastewater. Moreover, PECMA degrades refractory organic pollutants through ClO· generated by Ag2S-BiVO4 photoanode, which effectively decompose phenol to CO2 with a degradation rate of 93 %. Although tested as a proof-of-concept, the hybrid system opens up a novel field involving a sunlight-water-energy nexus, promising high efficiency NH4+ recovery and wastewater remediation.