The development of a hydrometallurgical process for the recycling of waste Pb-free solder based on nitric acid leaching, followed by the separation of Ag and Cu through AgCl precipitation or cementation, was investigated. Nitric acid dissolved Cu and Ag from the waste material while converting tin to stannic oxide (SnO 2 ), which is very sparingly soluble in the HNO 3 solution. More than 99% of the Ag and Cu in the waste Pb-free solder were dissolved in 2 kmol·m ¹3 HNO 3 under the leaching conditions of 75°C, 100 kg·m ¹3 pulp density and stirring at 400 rpm for 120 min. The addition of NaCl or Cu powder was used to separate Ag from Cu in the solution. The addition of 2 kg·m ¹3 of NaCl or 125 kg·m ¹3 of Cu powder to the leaching solution at 30°C led to the successful recovery of 3755 g·m ¹3 of Ag. Thus, the results showed that Sn, Ag and Cu could be separated and recovered from waste Pb-free solder by the proposed recycling process.
Precious metals which include the platinum group, gold, and silver, play indispensable roles in high technology industries of the modern world due to their outstanding physical and chemical properties. As a result of diminishing availability of mineral sources, increasing demand, and environmental concerns, the recovery of precious metals from both leaching and industrial waste solutions is becoming a very important technology. Magnetic solid phase extraction (MSPE) is a technique that has received substantial consideration in the separation and recovery of precious metals because of the many advantages it offers compared to conventional methods. This technique is based on the extraction of different analytes from solutions using solid adsorbents with magnetic properties. This review focuses on different types of magnetic adsorbents, the main procedures used for synthesis, characterization and their application in precious metals recovery based on recently published literatures.
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