Removal of nitrate from drinking water by ion-exchange followed by nzvi-based reduction and electrooxidation of the ammonia product to n2(G)

Inbal Fux, Liat Birnhack, Samuel C.N. Tang, Ori Lahav*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Ion-exchange (IX) is common for separating NO3 from drinking water. From both cost and environmental perspectives, the IX regeneration brine must be recycled, via nitrate reduction to N2(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 N2(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 N2(g) at the inherent high Cl concentration, which prepared the brine for the next IX regeneration cycle. The dominant reaction between nZVI and NO3 was described best (Wilcoxon test) by 4Fe(s) + 10H+ + NO3 → 4Fe2+ + NH4+ + 3H2O, and proceeded at >5 mmol·L−1·min−1 at room temperature and 3 < pH < 5.

Original languageEnglish
Article number2
Pages (from-to)1-19
Number of pages19
JournalChemEngineering
Volume1
Issue number1
DOIs
StatePublished - Sep 2017
Externally publishedYes

Keywords

  • Drinking water
  • Electrooxidation
  • Ion exchange
  • NZVI
  • Nitrate reduction

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