Ammonia Extraction of Nonferrous Metals from Electroplating Sludge

The study investigates the process of ammonia leaching of copper, zinc, and nickel from solid electroplating sludge. The research determines the kinetics and optimal conditions for copper extraction from the sludge, including ammonia concentration, pH, and solution temperature, and establishes, using copper as an example, the regimes of electroextraction that yield metal of high purity. The results show that equilibrium formation depends only slightly on solution temperature, which characterizes processes with external diffusion kinetics. At an ammonia concentration above 10 wt %, up to 99% of copper salts dissolve, and the copper ion concentration reaches 12 g/dm3. In contrast, the concentrations of nickel and zinc in the sludge remain much lower, and at equilibrium their concentrations reach 1.2 and 2.4 g/dm3, respectively. Copper deposits on the cathode as a dense, compact layer. At a current density of 1.5 A/dm2 and a copper concentration in the solution above 5 g/dm3, the current efficiency of copper approaches 100%.