REMOVAL OF CHROMIUM FROM CELL LIQUOR

摘要

24 Soluble hexavalent chromium values are removed from aqueous chlorate solutions by employing a critical effective ratio of OH- : Cr2O7= ions of at least 3:1 in the aqueous chlorate solution and by employing a dithionite to reduce the hexavalent chromium to trivalent chromium, preferably in the mole ratio of S2O4= : Cr2O7= of at least 3:1. The trivalent chromium forms chromic hydroxide (Cr(OH)3) with the hydroxyl ions and precipitates from the aqueous chlorate solution. The process is rapid and effective in quantitative removal of hexavalent chromium from the aqueous chlorate solutions and is especially useful for the removal of sodium dichromate from cell liquor which is intended to be employed in chlorine dioxide production and which is produced by diaphragmless electrolysis of sodium chloride.