Upcycling wastewater nitrate into ammonia fertilizer via concurrent electrocatalysis and membrane extraction

Ning Shi, Jianan Gao, Kai Li, Yifan Li, Wen Zhang, Qipeng Yang, Bo Jiang

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Electrocatalytic upcycling of nitrate (NO3) in wastewater into the valuable ammonium-based fertilizer has been considered as a green and appealing alternative to biological nitrogen removal or the industrial ammonia (NH3) production processes. This work investigated an innovative and energy-efficient electrolysis flow-through cell consisting of a porous activated iron nickel (FeNi) alloy cathode and a hollow polypropylene fiber membrane extraction unit to realize the electrochemical NO3 reduction and simultaneous upcycling to ammonium sulphate salts ((NH4)2SO4). Cathodic and anodic electrochemical half-reactions were coupled to enable NO3 reduction to ammonia and in-situ acid/base productions to promote the membrane stripping of NH3. Our results show that after electrolysis operation for 14 h for a synthetic wastewater containing 150 mM NO3 under a cathodic current density of 30 mA·cm−2, 99 % of NO3 removal efficiency, 98 % of ammonia selectivity, 93 % of Faradic efficiency and 97 % of total ammonia nitrogen (TAN) recovery were achieved respectively. A NH3 recovery flux and a specific energy consumption reached 2050 g-(NH4)2SO4·m−2·d−1 and 11 kWh·kg−1-(NH4)2SO4, respectively, which outcompetes many reported processes. Direct electron transfer was the main mechanisms of electrochemical NO3 reduction to ammonia. Interfacial reaction thermodynamics and kinetics analysis of key intermediates (e.g., *NO3, *NO2, and *NO) shows that the NiFe2O4 (3 1 1)-Ni site on the thermally activated FeNi alloy surface exhibited higher reactivity and specificity toward electrochemical NO3 reduction to ammonia over nitrogen (N2) or hydrogen (H2) generation. Ultimately, this study aims to promote sustainable nitrogen nutrient recovery and ammonia fertilizer synthesis from wastewater treatment.

Original languageEnglish (US)
Article number140959
JournalChemical Engineering Journal
Volume455
DOIs
StatePublished - Jan 1 2023

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Environmental Chemistry
  • General Chemical Engineering
  • Industrial and Manufacturing Engineering

Keywords

  • Ammonia recovery
  • Electrocatalysis
  • FeNi catalyst
  • Membrane extraction
  • Nitrate reduction

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