| dc.description.abstract | Cementation process is a promising technology for recovery of metal copper from wasted etching liquid containing copper chloride. Also, after solid/liquid separation, the supernatant can be recovered and reused as coagulant. In this study, synthesis wasted liquids containing various concentration of copper ion and free acid (HCl) were prepared in order to simulate the real characteristics of wasted etching liquid. Also, batch tests of cementation were studied by using metal iron or aluminum as the sacrificed metal. Several indicators of performance, such as reaction temperature, copper recovery rate and reaction time, purity of copper powder, and quality of the recovered supernatant, were evaluated. The proper operation mode of cementation was established and applied to the real wasted etching liquid for verification.
Experimental results showed that once adding enough dosage of sacrificed metal iron, the copper recovery rate increased with the increase of initial concentration of copper and free acid. However, this also resulted in raising temperature up to greater than 75℃ and affecting the safety of operation, especially, in the case of copper ion and free acid concentrations were both greater than 75 g/l. Nevertheless, increasing the concentration of free acid and the amount of the sacrificed metal iron could enhance the reaction rate of cementation, the recovery rate of copper and the content of ferrous chloride in supernatant. In addition, the more free acid the more hydrogen ion would consume the residue metal iron and then could obtain higher purity of copper powder. On the contrary, increasing the dosages of metal iron would decrease the purity of copper powder. Although, adding metal iron in a mode of sequencing replenishment could reduce the reaction between iron and free acid, the reaction rate of cementation would decrease at the same time. Therefore, it was suggested that adding enough iron at once was priority choice unless the concentration of copper ion and free acid were both too high (＞75 g/l).
Regarding the system with aluminum as sacrificed metal, due to higher oxidation-reduction potential and vigorous reaction, the temperature was sharply increased when enough aluminum was added once. In order to avoid the danger of operation, sequencing replenishment of metal aluminum until the end of reaction is preferable. In addition, if the reaction temperature was below 65℃ as well as the coexistence of copper ion, chloride ion and metal copper, the results of XRD analysis revealed that crystal of cuprous chloride was found within the copper powder, consequently, too much chloride would resulted in lowering the purity of the recovered copper. Actually, this study found that copper recovery could be greater than 99% in 75 minutes of reaction time as the initial copper ion concentration (Cu0) was in the range of 35~75g/l and the replenishment of aluminum reached the Al/Cu0 molar ratio was 1.2.
Based on the results of the study for synthesis wasted liquids. Further applying the suggestion of operating mode to the real wasted etching liquid, it found that 100% of copper recovery rate, 89% of copper purity, and 25% of ferrous chloride were obtained in 25 minutes of reaction time when using iron as sacrificed metal. On the other hand, it also attained 100% of copper recovery rate and 99% of copper purity in 75 minutes when using aluminum as sacrificed metal for cementation. | en_US |