Pure Chromium Sulfate Heptahydrate from Waste Tanning Solutions | ||
| Egyptian Journal of Chemistry | ||
| Article 4, Volume 55, Issue 2, April 2012, Pages 161-178 PDF (688.23 K) | ||
| DOI: 10.21608/ejchem.2012.1140 | ||
| Abstract | ||
| THIS work defines a method for the preparation of pure chromium sulfate heptahydrate from waste tanning solution. The waste resource contains free and soluble fats, calcium hydroxide, iron, magnesium as soluble elements together with chromium ions. The waste solution was filtered to get rid of insoluble materials. This was followed by removal of calcium, iron and magnesium by precipitation as insoluble oxalate salts using 1.3 stoichiometric ratio of oxalic acid in faint acidic medium. Soluble fats were removed by solvent extraction using 1:1 mixture of petroleum ether and isopropanol at 60°C. The remaining solution contains chromium sulfate together with minor fat impurities. Chromium was selectively precipitated as insoluble hydroxide cake at pH 8.5. Polyacrylamide (0.05%) solution helps fast agglomeration and sedimentation of Cr (OH) 3. The hydroxide was washed repeatedly with hot distilled water. The hydroxide cake was partially dehydrated prior to reaction with pure sulfuric acid to prepare pure chromium sulfate solution. Dry chromium sulfate heptahydrate salt was prepared by addition of absolute ethyl alcohol at room temperature whereby the salt is insoluble in alcohol. The influence of some parameters that affect the productivity of the method was studied. | ||
| Keywords | ||
| Chromium sulfate; Tanning waste solutions; Precipitation and Chemical techniques | ||
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