Production of chrome tanning composition from waste chromium-copper pickling liquor
Abstract
Abstract A CHRONE TANNING COMPOSITION IS OBTAINED FROM THE WASTE LIQUOR RESULTING FROM THE PICKLING OF CUPREOUS MATERIAL WITH AN AQUEOUS SULFURIC ACID-SODIUM DICHROMATE SOLUTION BY REDUCING AT LEAST MOST OF THE HEXAVALENT CHROMINUM CONTENT OF THE CONCENTRATED WASTE LIQUID TO THE TRIVALENT STATE, AND BY THEN LOWERING THE COPPER CONTENT OF THE WASTE LIQUOR TO A MAXIMUM OF ABOUT 8 GRAMS PER LITER BY ELECTROLYSIS OR BY ADDING TO THE LIQUOR A METAL WHICH WILL DISPLACE COPPER FROM THE LIQUOR. THE METHOD FURTHER INCLUDES THE STEPS OF NEUTRALIZING THE AQUEOUS SOLUTION TO OBTAIN THEREIN A RATIO OF HYDROXYL TO TRIVALENT CHROMIUM IONS IN THE CHROMIC SALT SOLUTION WITHIN THE RANGE OF ABOUT 1:3 TO 2:1 AND THE STEP OF CENCENTRATING THE WASTE LIQUOR TO AT LEAST A TOTAL CHROMIUN CONTENT OF ABOUT 0.4 POUND PER GALLON (EXPRESSION AS CR2O3), BOTH OF WHICH STEPS CAN BE CARRIED OUT AT ANY STAGE OF THE METHOD. THE RESULTING PRODUCT LIQUOR CAN BE USED DIRECTLY FOR TANNING OR CAN BE DEHYDRATED TO A TANNING SALT COMPOSITION.
Inventors
- 👤 J Robinson
- 👤 J Howard
- 👤 R Hahn
- 👤 D Hemming
Bibliographic Details
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