(68c) Remediating and Valorizing Nitrogen-Polluted Wastewaters Via Electrodialysis and Nitrate Reduction
AIChE Annual Meeting
Monday, November 8, 2021 - 8:40am to 9:00am
The EDNR reactor consists of three chambers and operates in two stages (Fig. 1a), with the influent entering the middle chamber and products recovered from the left and right chambers. In stage 1, influent NO3â and NH4+ are separated via electrodialysis (ED) and ammonia is recovered in the right chamber. In stage 2, ammonia is synthesized from the electrochemical nitrate reduction (NR) in the left chamber.
We have demonstrated proof-of-concept EDNR reactors using titanium foil (left chamber, NR electrode), Ti/IrO2-Ta2O5 mesh (left and middle chambers, ED electrode), and Pt foil (right chamber, ED electrode). With recirculating batches of simulated wastewater (100 ppm NO3â + 500 ppm NH4+) for three cycles (9 hours, Fig. 1b), 75% influent NH4+ was recovered into the right chamber and 25% influent NO3â was converted to NH4+ in the left chamber (Fig. 1c and 1d). Furthermore, the performance of EDNR can be readily adjusted to various influent conditions by rationally designing the electrochemical environments (e.g., electrode material, initial electrolyte composition) in each chamber and controlling the operational parameters (e.g., current density, electrode potential, influent flow rate, stage period). Our preliminary results have shown that the addition of Na+ promotes NR performance in influent with low NO3â concentrations. Such flexibility allows us to have controllable and stable water remediation and ammonia production from unstable and uncontrollable wastewaters.