Electrochemical synthesis of peroxodiphosphate using boron-doped diamond anodes

Peroxodiphosphate salts are strong oxidizing agents that presently can be used as reagents in organics synthesis, cosmetic, agriculture, polluted water treatment, and also as bleaching agents in the detergent industry. They also have potential uses as persulfates substitutes. In this work, a new method for the synthesis of peroxodiphosphate, based on the use of boron-doped diamond electrodes, is described. The procedure developed is able to produce high-purity peroxodiphosphate (no reagents different from phosphate salts are used as raw materials) with a high current efficiency. The efficiencies of the process strongly depend on the pH and on the operating conditions (temperature and current density). The optimum range of pH is 12-13. Current densities over 1000 A m(-2), and low temperatures, guarantee high current efficiencies and product conversions. The pH control is considered to be one of the more important operation constraints in the process. Great concentrations of phosphate in the raw materials increase the process efficiencies but they also seem to favor the corrosion of the electrode. Concentrations below 1 M of PO43- are recommended to avoid this problem. (c) 2005 The Electrochemical Society.