Enhanced ammonia-rich solution production and electrode separation using magnetic nickel-loaded carbon black in flow-electrode electrochemical deionization (FEED)

Carbon materials with abundant micropores and large specific capacitance (e.g., activated carbon, AC) are usually considered to be ideal candidates for flow-electrode capacitive deionization and are now widely employed to the ammonia recovery from wastewater. However, the microporous structure endows AC with a strong adsorption capacity toward ammonia nitrogen, which greatly reduces the recovery efficiency (the storage of ammonia nitrogen in the electrolyte). In this study, magnetic nickel-loaded carbon black (Ni 0 -CB) particles were simply synthesized by impregnating Ni onto the surface of the carbon black (CB) particles, endowing no <50 % of electrical energy savings and increasing ammonia recovery efficiency by ~20 % in comparison to AC. When charging, Na + and NH 4 + were migrated to the cathode, with the conversion of NH 4 + into NH 3 was accelerated due to the higher pH of Ni-CB systems. The excellent electrical conductivity of the CB body and compensation of the conductivity of Ni greatly decreased the electrical energy consumption. Followed by reverse discharge, Na + and less NH 4 + would be turned back into the spacer chamber; the adsorption toward NH 3 was effectively reduced due to the abundant mesopores of CB. Thus, NH 3 was more likely to be retained in the electrolyte. In addition, the superior magnetic features of Ni-CBs realized the rapid separation of the CB and ammonia-rich solution. The introduction of magnetic Ni-CB in flow-electrode electrochemical deionization technology realized the improved ammonia-rich solution production from wastewater and the recycling of carbon particles without additional solid–liquid separation (i.e., filtration, settlement).