Kinetic Studies of the Electrochemical Treatment of Nitrate and Nitrite Ions on Iridium‐Modified Carbon Fiber Electrodes

Abstract

Electrochemical reductions of nitrate and nitrite ions in neutral solution were studied using an Ir-deposited carbon fiber electrode. The objective of the study was to set up a process to remove nitrate and nitrite ions from industrial and municipal wastes as well as from the nitrate and nitrite ion enriched water supplies. Since nitrate and nitrite ion reduction kinetics is very slow on plain carbon, the iridium-modified fibers showed a significant reduction of nitrate and nitrite ions. Nitrogen and ammonia were identified as the two major gaseous products of the reduction process. A first-order inhibition kinetics model is proposed and was used to analyze the nitrate and nitrite ion reduction kinetics. The reduction rates of nitrate and nitrite ions were favored at higher cathode potential (cf. ±950 mV and ±850 mV) in a solution of pH = 7.0 with hydrogen evolution efficiency increasing with cathodic potential. A simple model for the batch re-circulation process was developed for the reduction of nitrate ion at surface-modified fiber electrode. There was a good agreement between the model predictions and experimental results.

Electrochemical reduction of nitrate ion on various cathodes ? reaction kinetics on bronze cathode

“…The calculated values were k 2 =1.76· 10 )5 s )1 and k 3 ¼ 7:66 Â 10 À3 l mol )1 s )1 . In fact, the values of the rate constants include the hydrogen adsorption according to reference [42], where the rate of nitrate, when the hydrogen coverage is high, can be expressed as:…”

Influence of Operational Parameters on Rapid Nitrate Removal Using an Electrochemical Flow Cell

“…This CV curve showed two cathodic peak currents at point e and b´. Accordingly, NO 3 -was mainly reduced by the cathodic reduction at the negative potential of -0.2 V at point e and the reduced species were thought to be stable intermediate byproducts such as NO 2 -or NH 3 [16]. Significantly, at the backward scan direction another recognizable anodic current except anodic peak current except a peak d´ was not observed, which denotes that the reduced species of NO 3 -was not reoxidized to NO 3 -.…”

“…The applied electrolytic current ranged from 0.10 to 2.90 A, which was equivalent to the volumetric electric charge from 300 to 8,700 C/L. At these volumetric electric charges the main reduced intermediate products were found to be NO 2 -and NH 3 [16]. The enhancement of NO 3 -reduction with the increase in volumetric electric charge was observed at 300, 1,500 and 2,700 C/L where NO 3 -concentration was measured 1.18, 0.92 and 0.71 mM, respectively.…”

“…6 (b The slope of the regression line was 0.783 mM-N/mM-Cl 2 , which is equivalent to the molar ratio of Cl 2 consumption to TN removal of 1.28. Based on the equations (15) and (16), the theoretical molar ratio of chlorine to NH 3 is projected to be 1.5 for N 2 evolution and 2 for N 2 O evolution. Although the observed molar ratio was slightly smaller than the theoretical molar ratio due to the uncertainty of estimation of Cl 2 consumption for chloramine accumulation, it was close to the theoretical molar ratio for N 2 evolution.…”

An In Situ Copper Plated Boron‐Doped Diamond Microelectrode Array for the Sensitive Electrochemical Detection of Nitrate

“…A variety of techniques for the electrochemical reduction of nitrate over the years has been explored at metal electrode substrates such as cadmium [9,10], lead [11,12], silver [13], mercury [14,15], cadmium -copper alloy [16], copper [1, 3, 17 -19], an iridium deposited carbon fiber electrode [20], and boron-doped diamond [21 -23]. Though the majority of these studies focus on the associated fundamental electrolytic process.…”