Selective aqueous ammonia sensors using electrochemical stripping and capacitive detection

Abstract

Managing waterborne ammonia-nitrogen pollution requires monitoring distributed wastewater nitrogen discharges. In this study, we demonstrated and investigated a proof-ofconcept sensor that combines selective electrochemical separation and sensitive capacitive detection for sensing total ammonia nitrogen (TAN). By varying TAN concentration in synthetic ammonia-polluted water (up to 50 mg/L), we selectively separated ammonia nitrogen from feedwater into a sulfuric acid solution, in which capacitance decreased linearly with increasing TAN (R 2 > 0.99). Experimental observations were supported by theoretical explanations for the decrease in capacitance as ammonia absorbs into the sulfuric acid solution and abstracts protons. Capacitive detection facilitated TAN sensing at higher acid concentrations (up to 0.5 M H 2 SO 4 ) than conductivity detection (up to 0.01 M H 2 SO 4 ), which enables sensitive sensors with larger TAN detection ranges, longer deployment, and less complexity. Results from this study provide evidence of the use of selective separations and their transport mechanisms for environmental sensing applications.

Electrified Ion Exchange Enabled by Water Dissociation in Bipolar Membranes for Nitrogen Recovery from Source-Separated Urine

“…Our previous nitrogen recovery studies using ECS indicated that the recovery efficiency varied with the influent nitrogen concentration. 24,36 We expected EXS to be more compatible with fluctuating nitrogen concentrations because it separates nitrogen from urine onto resins; indeed, three nearly identical ammonium breakthrough curves were again observed with concentrated synthetic urine, albeit with half as many bed volumes (Figure S18a). The mass of ammonium removed by the resin was identical for synthetic and real urine (around 300 mg NH 4 + for the 12 mL resin used, Figure S18b), which demonstrated that resin equalized nitrogen loading from different streams.…”

“…WD-based EIX can avoid close resin–electrode contact, especially when protons are produced by WD in bipolar membranes (BPMs). Only ex situ BPM-assisted regeneration has been demonstrated, making BPM-assisted in situ regeneration a promising but underexplored approach for enhancing process intensification. − …”

Ion exchange enabled selective separation from decontamination to desalination to decarbonization: recent advances and opportunities

“…83 Mild basic solution can be readily produced with electrochemical approaches, such as water splitting. 46,65,88,89 With a simple electrochemical reactor containing two electrodes and an ion exchange membrane (Fig. 7a), the electrolyte pH can readily be elevated to pH 11 even with a low current density.…”

Electro‐membrane reactor: A powerful tool for green chemical engineering

“…Besides, Schlumpberger et al developed 108 a electrochemical water treatment method called “Shock electrodialysis,” which shows promise for water deionization and ionic separations. Lalwani et al investigated 109 a proof of concept sensor dependent on electrodialysis technology for sensing total ammonia nitrogen (TAN).…”