Ion-exchange (IX) is common for separating NO 3− from drinking water. From both cost and environmental perspectives, the IX regeneration brine must be recycled, via nitrate reduction to N 2(g) . Nano zero-valent iron (nZVI) reduces nitrate efficiently to ammonia, under brine conditions. However, to be sustainable, the formed ammonia should be oxidized. Accordingly, a new process was developed, comprising IX separation, nZVI-based nitrate removal from the IX regeneration brine, followed by indirect ammonia electro-oxidation. The aim was to convert nitrate to N 2(g) while allowing repeated usage of the NaCl brine for multiple IX cycles. All process steps were experimentally examined and shown to be feasible: nitrate was efficiently separated using IX, which was subsequently regenerated with the treated/recovered NaCl brine. The nitrate released to the brine reacted with nZVI, generating ammonia and Fe(II). Fresh nZVI particles were reproduced from the resulting brine, which contained Fe(II), Na + , Cl − and ammonia. The ammonia in the nZVI production procedure filtrate was indirectly electro-oxidized to N 2(g) at the inherent high Cl − concentration, which prepared the brine for the next IX regeneration cycle. The dominant reaction between nZVI and NO 3 − was described best (Wilcoxon test) by 4Fe (s) + 10H + + NO 3 − → 4Fe 2+ + NH 4 + + 3H 2 O, and proceeded at >5 mmol·L −1 ·min −1 at room temperature and 3 < pH < 5.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.