GB1037725A - Fluid treatment - Google Patents

Abstract

<PICT:1037725/C6-C7/1> Ions are removed from solutions in two electro-dialysis stages, one a stack of cationic permeable membranes defining fluid compartments having an acid solution adjacent each compartment through which the solution to be de-ionized flows, and second a similar stack having anionic permeable membranes forming compartments adjacent an alkali solution. The acid and alkali stages may be reversed in accordance with the solution treated, and other treatment effected between the two stages. For example instant tea powder is made by extracting tea leaves with hot water at 160 DEG F., and passing the extract through a dialysis cell of the alkali type, using dilute KOH. Anions contained in the tea are removed with KOH from a pipe 15, and the treated tea flows through a pipe 17 when it is treated with oxygen or a little H2O2 which forms a soluble tannin-caffeine complex. The tea and oxidized complex are then passed through a dialysis cell of the acid type through a pipe 18. The tea now at pH5 is finally concentrated and dried. Tea made from the entirely soluble powder is free of salts and forms a clear solution. The current applied to the electrodes may be periodically reversed to prevent deposition of solids on the membranes. The process may be applied to removing salt from whey, or treating sugar solutions, milk, molasses, fruit juices, wine, sewage, and other liquids, when the two treatment stages may be reversed.