A Boundary‐Layer Model of a Parallel‐Plate Electrochemical Reactor for the Destruction of Nitrates and Nitrites in Alkaline Waste Solutions

Abstract

so that a plot of Q vs. ~q yields a straight line with the intercept of in (io). This plot is the so-called Allen-Hickling plot. This procedure has been used extensively to determine the exchange current density from potential step data. The potential step data were collected with positive voltage feedback so that the voltage loss due to electrolyte resistance was compensated properly. The double-layer charging current is significant only in the initial time period. The kinetic current was obtained by square root extrapolation of the current between 0.6 and 1.0 ms to time zero. At least three measurements were taken at each potential. Sufficient time was allowed between measurements (usually 15 min). The activation polarization curve for the high-Btu gas is shown in Fig. 3. The corresponding Allen-Hickling plot is presented in Fig. 4. The exchange current density calculated according to the above procedure is 1.49 mA/cm 2, which is more than an order of magnitude lower than that of copper (26.3 mA/cm 2) or nickel (48.3 mA/cm2). The electrocatalytic activity of lithium letrite is significantly lower than that of nickel or copper. The Allen-Hickling plots for medium and low-Btu gases are shown in Fig. 5 and 6. A complete comparison of the three materials is listed in Table II. SummaryAn experimental approach was conducted to study the electrochemical properties of lithium ferrite as an alternative anode material in MCFC. Some unique characteristics were observed: (i) the open-circuit potential was shifted in the positive direction for lithium ferrite. The measured OCP is a mixed potential; (it) the steady state current is about 60 % lower than that of nickel under the same conditions; (iii) two waves were found in the cyclic voltammograms: the first wave is attributed to hydrogen oxidation and the second wave is related to oxidation of Fe 2 § to Fe 3 § in the structure; (iv) the exchange current density of hydrogen oxidation on lithium ferrite is an order of magnitude lower than that on copper or nickel; (v) kinetically speaking, lithium ferrite is not a favorable anode material, despite its having better sulfur tolerance and sintering resistance than nickel.

Harnessing Photoelectrochemistry for Wastewater Nitrate Treatment Coupled with Resource Recovery

“…Percentage breakdown of nitrogen species, NO 3 – (mg-NO 3 – /L), NO 2 – (mg-NO 2 – /L), and NH 4 + (mg-NH 4 + /L), is indicated for each source. Data was compiled from the U.S. Environmental Protection Agency (EPA) development documents, , EPA’s database for industrial wastewater treatment technologies, and pertinent journal papers. ,− ,,− EPA’s specifications for nitrogen-contaminants in drinking water: <44.3 mg-NO 3 – /L (dashed blue line) and <3.3 mg-NO 2 – /L…”

Flue Gas CO2 Capture via Electrochemically Mediated Amine Regeneration: Desorption Unit Design and Analysis

“…Pickett’s work on the theoretical approximation of laminar boundary layers provides an analysis of the correlation of cell dimension and mass transfer characteristics. Prasad and Farell incorporated the mass transfer approximation to model the destruction of nitrates in waste solution. The recent works of Walsh et al provide empirical mass transfer correlations for the inclusion of turbulence promoters in industrial reactors. , …”

Electrochemical reduction of nitrate and nitrite in simulated liquid nuclear wastes

“…Apart from nitrate and nitrite, both types of wastes contain other ionic species as it is shown in Table 1. A flow sheet of the process for treating liquid radioactive wastes has been presented by Prasad et al [3] in which a necessary step is the removal of nitrate and nitrite [1][2][3].…”

“…The treatment of the LLW can be performed by electrochemical reduction of nitrate and nitrite to the non-toxic nitrogen gas [1,[3][4][5][6][7][8][9][10][11]. An ideal electrochemical method must combine (i) selective conversion of nitrate and nitrite to nitrogen; (ii) high rate of reduction; (iii) high current efficiency (%CE); and (iv) low energy consumption.…”