METHOD OF REGENERATING SPENT CHROME TANNING SOLUTIONS Russian patent published in 2010 - IPC C14C3/32 

FIELD: chemistry.

SUBSTANCE: method involves separation of suspended and fatty substances. A solution heated to 50-70°C is mixed with hydrogen peroxide and held for 30-120 minutes until complete decomposition of hydrogen peroxide. The mixture is mixed with a fresh tanning agent until achieving process concentration of chromium for tanning material and returning the solution for tanning. In order to separate suspended and fatty substances, silicic acid is added to the spent tanning solution in form of silicon dioxide (SiO₂), with ratio of SiO₂ to weight of suspended and fatty substances of the spent tanning solution equal to 1: 10-30.The solution is held for 5-15 minutes, after which the floating solid phase on which dissolved organic impurities are adsorbed is separated. Hydrogen peroxide is then added to the solution in dosages of 12-45% of the stoichiometric standard for complete mineralisation of organic impurities due to chemical consumption of oxygen of the solution.

EFFECT: simplification of the process with low content of dissolved organic impurities and consumption of oxidising agent.

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