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

Abstract

The electrochemical reduction of NO 3 ) in 0.1 M K 2 SO 4 and 0.05 M KNO 3 solution was studied on various electrodes in two different cell configurations, a divided and an undivided one. The products in all cases were NO 2 ) , NH 3 , N 2 and small amounts of NO 2 and NO. The more efficient cathodes as regards the conversion of NO 3 ) to N 2 were Al and the alloy Sn85Cu15, where the selectivity for nitrogen formation was 43 and 35.3% at )1.8 and )2.0 V, respectively. The kinetic analysis of the experimental results was carried out by numerical solution of the resulted differential equations according to the scheme:The rate constants on Sn85Cu15 at )2.0 V for the above reactions were found to be k 1 ¼ 4:9 Â 10 À4 s )1 , k 2 ¼ 1:76 Â 10 À5 s )1 and k 3 ¼ 7:66 Â 10 À3 l mol )1 s )1 . At more negative potential more NO 2 ) ions reduced and converted either to N 2 or NH 3 . The rate constant of reduction of nitrate was almost the same in the region between )1.7 and )2.0 V, because the reaction is limited by the diffusion. In order to oxidize a part of the undesirable byproducts NO 2 ) and NH 3 at the anode of the cell to nitrate and nitrogen respectively, an undivided cell was used. Comparison between the two cell configurations indicated that, although in the undivided cell the % removal efficiency of nitrate was lower than that in the divided one, the selectivities of NO 2 ) and NH 3 were 4.8 and 2.2 times lower, respectively.

Simultaneous Voltammetric Determination of Nitrate and Nitrite Ions Using a Copper Electrode Pretreated by Dissolution/Redeposition

“…Among many electrode materials, copper is expected to be the most effective material in terms of electroreduction of nitrate and nitrite ions. [15][16][17][18][19][20][21] Indeed, many studies have shown that pretreated and/or modified copper electrodes are effective for the determination of nitrate and nitrite ions. 13,14,[22][23][24][25][26] However, the pretreatments and/or modifications of copper electrodes in the studies seem to be complicated, time consuming and insufficiently sensitive for the determination of nitrate and nitrite ions in natural water samples.…”

Fabrication and Characterization of a Cu-Zn-TiO2Nanotube Array Polymetallic Nanoelectrode for Electrochemically Removing Nitrate from Groundwater

“…It can be seen that the IrO 2 anodes have always maintained a low ammonia production, while Pt anodes have higher ammonia production in the middle of the reaction. So we deem IrO 2 is a better oxidizing agent for NH 4 + and NO 2 − than Pt. Adding too little NaCl would cause too little hypochlorite to be produced, meaning that all of the nitrite and ammonia would not be removed.…”

“…The chemical methods produce toxic byproducts, such as nitrite and ammonia and require either large quantities of metals or hydrogen as reducing agent. 4 In recent years, attention has been particularly focused on electrochemical methods of removing nitrate from water. Electrochemical methods have advantages such as no demand for chemicals before or after the treatment, no sludge produce, small area occupied by the plant and low investment costs.…”

“…Pt has a low nitrate reduction activity, whereas Cu and Zn are much more active. 3,4 Electrodes made of two metals often have higher catalytic activities than do electrodes made of one metal. Using a Cu/Zn cathode and a Pt anode has been found to give a high electrocatalytic activity for nitrate.…”

“…1 Major anthropogenic sources of nitrate in groundwater are industrial wastewater, domestic sewage, animal waste, nitrogen fertilizers, and other waste liquids. [2][3][4] The World Health Organization has set a guideline maximum nitrate concentration in drinking water of 45 mg/L, and the European Union regulatory limit is 50 mg/L for regular potable water and 15 mg/L for water ingested by infants. [5][6][7] High nitrate concentrations in drinking water can seriously harm human health, impairing oxygen transport to the tissues.…”