New Insights into the Electrochemical Production of Potassium Peroxodiphosphate

Abstract

Fundamental studies involving rotating disc and ring-disc electrodes, in conjunction with a potential reversal procedure, were conducted to determine the optimal conditions for the electrosynthesis of potassium peroxodiphosphate. The research focused either on anode activation through potential reversal or on using potassium nitrate as an additive. Fundamental research was corroborated using a batch cylindrical reactor divided by a cation exchange membrane. The anode was a helical platinum wire and the cathodic reaction was hydrogen evolution at a nickel electrode. The best results were obtained using a 2 M K2HPO4 solution with a pH of 12.5 and a 0.6 M KNO3 solution in the anodic compartment at 239 mA cm−2 and 10 ◦C. The maximum current efficiency for peroxodiphosphate production was 32.6%, with a potassium peroxodiphosphate concentration of 79.5 mmol dm−3, giving a specific energy consumption of 2.84 kW h kg−1 and a space-time yield of 13.8 kg (m3 h)−1. However, for electrolysis times longer than two hours, the reactor performance diminishes due to the side reaction of oxygen evolution, which decreases the pH of the anodic compartment. Therefore, this process is promising for either the direct use of the anodic solution as an oxidizing agent for refractory contaminants or the production of pure salt.