| 摘要: | 以化學置換程序(cementation process)回收氯化銅蝕刻廢液，除可回收金屬銅之外，反應後之回收液，亦可進一步製成混凝劑。本研究依據實際氯化銅廢液之性質，自行配置含銅離子(Cu2+)與自由酸(HCl)之人工廢液，並以金屬鐵或鋁為犧牲金屬，進行批次實驗，再以操作反應溫度、銅回收率和反應時間、銅粉純度及回收液品質為評估指標，建立合適之操作方式，最後驗證於實廠廢液。 研究結果顯示，以鐵為犧牲金屬之置換反應，在一次添加足量鐵金屬時，初始銅離子與自由酸濃度越高，回收速率越快，但會造成反應溫度過高(75℃)，影響操作上的安全性，尤以初始銅離子與自由酸濃度分別大於75g/l時，最為顯著。自由酸濃度及犧牲金屬劑量的增加，有助於提升置換反應速率、銅回收率及回收液之氯化亞鐵含量，此外，自由酸濃度愈高時，氫離子可消耗置換反應後殘留的鐵金屬，提高銅粉純度，但鐵劑量越高，則會降低銅粉純度。以分批添加鐵的方式，可減少鐵金屬與自由酸的反應，但相對的亦降低了整體的置換反應速率，所以當以鐵為犧牲金屬時，建議仍以一次添加鐵的方式為優先考慮，而分批添加鐵的方式，僅適用在高濃度銅離子與高自由酸(>75g/l)之廢液。 以鋁為犧牲金屬之置換反應，由於鋁金屬與銅之氧化還原電位高，置換反應性佳，一次添加足量鋁金屬，操作上易發生反應溫度劇升的危險，因此，若要使銅離子完全置換，勢必將足量鋁金屬採取分批添加的方式。此外，若是系統同時存在銅離子、氯離子及銅金屬，且在反應溫度過低時(<65℃)，由XRD分析結果發現，會產生氯化亞銅結晶物，造成銅粉含氯量過高，降低銅粉品質。而本研究中，初始銅離子濃度介於35~75g/l之間，以分批添加鋁金屬方式，至總添加量達初始銅離子莫耳比1.2時，經75分鐘反應時間，可達到99％以上銅回收率。 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. |
