Abstract
Cyanide-free, sulphate-based copper electroplating waste solutions and spent nitric acid solutions from the etching of copper were investigated for copper recovery by cementation. It was found that continuous rotation of pieces of iron together with waste copper sulphate solution or intense circulation of the solution along through motionless iron pieces (e.g. scrap iron) with occasional shaking results in copper recovery of more than 99% within 15–30 min. In the case of copper-laden nitric acid solution before cementation it must be at least 2 fold diluted and sodium pyrosulfite should be added to overcome the oxidizing medium of nitric acid. When the pH of the solution is below 1, it is recommended to increase the pH to 1.5 (by adding NaOH prior to cementation). The postcementation solution treatment comprises pH correction to pH 9 followed by the removal of metal hydroxides by sedimentation or filtration.
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