Electrochemical Ammonia Recovery from Anaerobic Centrate Using a Nickel-Functionalized Activated Carbon Membrane Electrode

Abstract

Ammonia (NH 3 ) recovery from used water (previously wastewater) is highly desirable to depart from fossil fuel-dependent NH 3 production and curb nitrogen emission to the environment. Electrochemical NH 3 recovery is promising since it can simply convert aqueous NH 4 + to gaseous NH 3 using cathodic reactions (OH − generation). However, the use of a separated electrode and membrane imposes high resistances to the cathodic reaction and NH 3 transfer. This study examined an activated carbon (AC)-based membrane electrode functionalized with nickel to electrochemically recover NH 3 from synthetic anaerobic centrate. The membrane electrode was fabricated using nickeladsorbed AC powder and a polyvinylidene fluoride (PVDF) binder, and the PVDF membrane layer was formed at the electrode surface by phase inversion. The NH 3 -N recovery flux of 50.3 ± 0.4 gNH 3 -N/m 2 /d was produced at 17.1 A/m 2 with a recovery solution at pH 7, and NH 3 -N fluxes and energy consumptions were improved as the recovery solution became acidic (62.2 ± 2.1 gNH 3 -N/m 2 /d with 16.0 ± 1.6 kWh/kgNH 3 -N at pH 2). Increasing PVDF loadings did not impact the electrochemical performances of the Ni/AC-PVDF electrode, but slightly lower (7%) NH 3 -N fluxes were obtained with higher PVDF loadings. Ni dissolution (3.7−6.0% loss) was affected by the recovery solution pH, but it did not impact the performances over the cycles.

Flowable Nickel-Loaded Activated Carbon Cathodes for Hydrogen Production in Microbial Electrolysis Cells

“…Ni/AC powders were synthesized with two different methods based on previous studies. ,, With the Ni adsorption method, a fixed amount of AC powder (4 g, Norit SX plus CAT, Sigma-Aldrich Chemistry, USA) was mixed with 1 g of NiCl 2 ·6H 2 O (VWR, USA) in a glass beaker. The mixture of AC and Ni salts was stirred in deionized (DI) water (100 mL) for 30 min to induce the adsorption of Ni salts onto the AC surface.…”

Electrocatalytic Upcycling of Nitrate Wastewater into an Ammonia Fertilizer via an Electrified Membrane

“…Our calculation indicates that the total amount of the H + generated at the anode within the first 120 min was 15.2 ± 0.8 mmol (0.204 ± 0.011 A) with a final trap tank solution pH of 1.53 ± 0.10. The total molar amount of the generated NH 3 was only 1.05 mmol, implying that the remaining H + in the trap and anode chambers was sufficient to protonate the remaining NH 3 (7.63 ± 0.13 mM) in the feed tank (50 mL) . After a 3-h operation (e.g., circulating the flows through, the trap, cathodic, and anodic chambers), 99.3% of the generated TAN was recovered with only 0.15 ± 0.03 mM TAN remaining in the feed tank.…”

“…The total molar amount of the generated NH 3 was only 1.05 mmol, implying that the remaining H + in the trap and anode chambers was sufficient to protonate the remaining NH 3 (7.63 ± 0.13 mM) in the feed tank (50 mL). 27 After a 3-h operation (e.g., circulating the flows through, the trap, cathodic, and anodic chambers), 99.3% of the generated TAN was recovered with only 0.15 ± 0.03 mM TAN remaining in the feed tank. In addition, the trap tank can be repetitively used to recover and concentrate (NH 4 ) 2 SO 4 from multiple rounds of nitrate wastewater treatment (Figure S12).…”

“…To capture NH 3 gas, the external acid or buffer solutions (e.g., H 2 SO 4 ) must be used, which increases the cost and hazard risk or disposal issues. − Moreover, the oxygen evolution reaction such as water oxidation at the anode is only employed as a sacrificial half-reaction to provide protons and electrons for various cathodic reactions, such as H 2 production or NO 3 – reduction. , The anodic water oxidation consumes high electricity due to the high thermodynamic potential (e.g., 0.815 V vs NHE) and overpotential. Thus, properly redirecting the side reaction product H 2 from the cathode into the anodic chamber could potentially shift the water oxidation to H 2 oxidation (−0.414 V vs NHE) and thus decrease the total cell voltage and energy consumption.…”

Polysulfide-assisted urea synthesis from carbon monoxide and ammonia in water

“…Several techniques are available for the isolation and purification of urea from aqueous solution, such as forward osmosis (Ray, Perreault & Boyer, 2019), the use of adsorbents (e.g., activated carbons, zeolites, ion-exchange resins, and silica) (Urbanczyk, Sowa & Simka, 2016), and selective dissolution in certain solvents (e.g., ethanol) and subsequent recrystallization (Marepula, Courtney & Randall, 2021). Methods have also been developed for NH 3 recovery from wastewaters (Kuntke et al, 2018;Kim, Moreno-Jimenez & Efstathiadis, 2021). PSs is oxidized by O 2 to S 0 (Steudel, Holdt & Nagorka, 1986;Kleinjan, de Keizer & Janssen, 2005), which may be used for the next round of urea production.…”