Assessment of the electrochemical production of sodium perborate

Abstract

BACKGROUND: The convenient operating conditions for the electrochemical production of sodium perborate were first estimated by using a rotating ring-disc electrode. Based on these results two reactors, cylindrical batch and a recirculating parallel-plate arrangement coupled with a reservoir, were examined employing as anolyte a solution of sodium carbonate, borax and sodium silicate as a stabilising agent. With the use of the recirculating system the behaviour of platinum and boron-doped diamond as anode materials was analysed and employing also different separators between the anodic and cathodic compartments.RESULTS: The recirculating system with a platinum anode showed a suitable performance at a current density of 100 mA cm−2 and 10 °C of temperature. Under these operating conditions, the sodium perborate concentration was 97.6 mmol L−1 with a current efficiency of 21.4%. The specific energy consumption was 1.9 kW h mol−1 and the space-time yield was 29.3 mol m−3 h−1.CONCLUSION: A powder of monohydrate sodium perborate was obtained with 20 g L−1 NaOH as the initial catholyte concentration, alkalised the anolyte after the electrolysis, settled at 10 °C, and after drying in a vacuum oven at 40 °C. The particles form oblong-shaped agglomerates with different sizes, in the order of 50 μm. Thus, the electrosynthesis of this oxidising agent is appraised as an alternative procedure to the chemical method.