REMOVAL OF HEAVY METAL TRACES FROM CONCENTRATED ALKALI METAL CHLORIDE SOLUTION

摘要

PROBLEM TO BE SOLVED: To avoid the trouble of operation generated in electrolysis by heavy metal ions, in removing heavy metal traces from a conc. alkali metal chloride soln. up to a detection limit range, by adding an iron salt soln. to the alkali metal chloride soln. to coprecipitate and separate a metal salt causing trouble. SOLUTION: Since strong trouble is generated in operation in the presence of heavy metal ions at a time of chloro-alkali-electrolytic work according to an amalgam method, an iron chloride soln. (FeCb 40wt.%) is added to a acidic saline soln. (NaCl 24.5wt.%) with pH of 5 containing 0.4 ppm of molybdenum until pH becomes 3. Whereupon, a light brown precipitate composed of an iron oxide hydrate is formed and, since this precipitate forms a medium flocculent precipitate with the elapse of time, it can be easily filtered off. The residual amt. of molybdenum in this filtrate is below 0.01 ppm of a Mo detection limit.