Influence of cell construction on the electrochemical reduction of nitrate

The electrochemical reduction of nitrates in the weakly alkaline electrolyte, simulating spent solution after regeneration of a strongly basic anion exchanger was studied. Copper was used as the cathode material. The influence of the electrolyser construction, cathode form and process parameters on the current efficiency of the nitrate reduction was followed. Four types of cell construction were used: a plate-electrode cell, a cell with a fluidised bed of inert particles in the inter-electrode space, a packed bed cathode cell and a vertically moving particle bed cell. The highest current efficiency with respect to the nitrate reduction was observed for the vertically moving particle bed reactor. On the other hand, unexpectedly high efficiency was also observed for the simple plate-electrode cell, the disadvantage being very low current density (below 40 A m(-2)) resulting in suitable behaviour. From the point of view of cell efficiency coupled with simplicity of construction and operation, the optimal cell seems to be the cell with the fluidised bed of inert particles in the inter-electrode space. (C) 2002 Elsevier Science B.V. All rights reserved.