A sodium Basic Copper Carbonate(WSDTY) solution (90 l) containing 146 g Na2 CO3 /l was added to a 200 l vessel equipped with stirrer and heated to a temperature of 60° C. While stirring intensively and maintaining this temperature, 44 l of a waste solution from copper etching processes with a density of 1.34 g/cc and containing 21 g/l of HCl, 183 g/l of NaCl and 272 g/l of CuCl2 were added at a steady rate over a period of one hour.
During the addition, the pH which initially was higher than 12, came to a value of 7.7. After the stirrer was turned off, the basic copper carbonate formed deposited within 30 minutes as a light green precipitated sludge. A portion (100 l) of the supernatant, sodium-chloride-containing solution which now contained only 8 mg/l of Cu, was decanted off. A sample (A) was taken from the precipitated sludge, filtered, washed and dried. The properties of this basic copper carbonate obtained after a single precipitation process are listed in the following.
Sodium carbonate solution was added once again to the remaining aqueous basic copper carbonate suspension and waste solution from copper etching processes was added as described above. Here also, a sample (B) was taken from the precipitated sludge at the end of the reaction after the supernatant solution had been decanted off. This process was repeated an additional three times, and samples C, D, and E were taken after each precipitation process. The properties of Samples B, C. D, and E may also be found.
The bulk of the deposited, basic copper carbonate was now filtered off, washed and dried. A total of 51 kg of light green basic copper carbonate was obtained. It contained 55.4 weight percent Cu, 26.1 weight percent CO3, 0.02 weight percent Cl, 0.3 weight percent Na and 0.5 weight percent H2 O. This composition corresponds to the formula CuCO3. Cu(OH)2. xH2 O, in which x is less than 0.5.
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