Water treatment with activated alumina

Purification. N. S. Moe [Chem. Scand., 21 1389 (1967)] obtained highly pure solvent for polarographic use by first drying with molecular sieves (Linde 4A) and then treatment with active alumina (Woelm, activity grade one). The final water content was shown to be about 100 p.p.m. by Karl Fischer titration. 

The fractional distillation of organic Hquids and the use of azeotropes to remove water has been mentioned earlier. In many instances, organic liquids may be dried directly by adding desiccants. Traces of water may be removed from some solvents by treatment with activated alumina or, on the laboratory scale, with sodium, sodium borohydride, or calcium hydride. Molecular sieves of type 4A, i.e., with a porosity of 4A, are also extremely useful for the removal of water and a number of other small molecules from organic liquids. 

In certain solvents, such as dimethylformamide and dimethyl sulfoxide, water is a rather poor proton donor [347], and other impurities may be responsible for the protonation of the basic intermediates (radical anions, anions, and dianions). During preparative experiments the impurities may be reprotonated by water or, in case tetraalkylammonium salts (except tetramethylammonium salts) are used as supporting electrolyte, by attack on the cations (Hofmann elimination). Treatment of the medium with active alumina may lower the concentration of such protonating impurities [38,260]. 

Organic solution was fractionated by column chromatography on activated alumina. PCBs were eluted with n-hexane. Elemental sulfur was removed by treatment with activated copper before GC analysis. Filler was extracted with a didiloromethane-methanol (2 1) mixture in a sonication bath. Organic extract was fractionated by HPLC as for the water procedure. 

---