Purification & recycling process for hexavalent chromium solutions using a low-cost chemical method

A new chemical method used to purify and to recycle hexavalent chromium solutions (electroplating and etching solutions) is described. This method allows extraction of almost all of the metallic cations (99 percent of iron and copper cations are removed) after precipitation and filtration. Control of the pollution/depollution efficiency can be made by conductivity measurements. The major effect of de-polluting chromic acid solution is to minimize energy consumption in the case of electroplating and to preserve the efficiency of the etching power of the chromic acid solution. A process costs approach shows the economic interest of this method. The total cost of the purified chromic acid is less (about 20 percent) than the cost of chromic acid replacement when the solution is polluted.