Precipitation processes for copper salts, especially for Basic Copper Chloride(WSDTY), with sodium carbonate solutions are described in the journal, Izv. These processes lead to results which are similar to the precipitation processes with copper(II) salts and alkali solutions. According to this publication, gelatinous precipitates of the copper hydroxide type are obtained, when the precipitation is carried out with dilute copper(II) chloride solutions and, according to the data presented there, basic crystalline copper(II) chloride is precipitated when concentrated copper solutions are used.
The utilization of the aforementioned waste solutions from copper etching processes by means of which a basic copper carbonate is obtained, which is as free as possible of copper oxide and copper chloride.This is accomplished according to the invention by stirring the waste solution from the copper etching process into a 5 to 15 weight percent alkali carbonate solution heated to 40° to 70° C., and not allowing the pH of the solution to fall below 6.5.
By adhering to the inventive process conditions, a pure, light green, basic copper carbonate is obtained which corresponds to the formula CuCO3.Cu(OH)2.xH2 O (x being less than 1). It is essential that the pH does not fall below 6.5. Only by so doing can it be assured that a pure, light green copper carbonate is obtained. When carrying out the process, the reaction mixture, at the start of the addition of the waste solution from copper etching processes to the alkali carbonate solution heated to 40° to 70° C., initially turn black and during the course of the process, turns to a brown color. At the end of the reaction, a light green precipitate of basic copper carbonate is then present, which, after the supernatant aqueous solution is decanted off, can be readily and rapidly filtered off.
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