Abstract
The extraction of precious metals is of significant importance for recycling valuable precious metal resources, however, most of the current methods for extraction are inefficient, energy-intensive, or environmentally unfriendly. Herein, we report a new chemical dissolution system for precious metals employing the trichloroisocyanuric acid (TCCA) as an oxidant and tributyl monomethyl ammonium chloride (N4441Cl) as a complexant. The leaching yield was achieving 100 wt% for the metals of Au, Pd, Cu, and Ag at 25 °C, and the average dissolution rate of gold was reaching 375 mg/h, 107.1 times higher than that of traditional cyanide method. Based on the analysis of UV-Vis and XPS results, a possible reaction mechanism was proposed: the precious metals were probably oxidized by TCCA, then the formed precious metal ions coordinate with N4441Cl strongly to promote the dissolution process. Applied to gold dissolution from ores, waste electronic and electrical equipment (WEEE) and waste catalysts, the leaching yield of the TCCA-N4441Cl coordinative composite reached 97, 100, and 100 wt%, respectively, demonstrating that this method is not only efficient and environmentally friendly, but also with great adaptability and high potential for real applications.
Highlights
Precious metals are widely used in various industrial fields, including modern electronics, medicine and chemical catalysis [1,2,3,4,5,6,7]
The trichloroisocyanuric acid (TCCA)-Ionic liquids (ILs) composite solution showed a good solubility for Au00, Pd00, Cu00, Ag00 at room
The TCCA-ILs composite solution showed a good solubility for Au, Pd, Cu, Ag at room temperature (25 ◦ C, N4441 Cl = 3 g, TCCA = 0.3 g, acetone = 5 mL, metal = 0.01 g)
Summary
Precious metals are widely used in various industrial fields, including modern electronics, medicine and chemical catalysis [1,2,3,4,5,6,7]. The high value and depletion of precious metal reserves make the recovery of noble metals from the secondary resources highly desirable [8]. Waste electronic and electrical equipment (WEEE) and the spent catalysts are among the most important raw materials for precious metal recycling due to massive annual production and high element abundance. The annual production of waste catalysts is about 500,000–700,000 tons [9,10]. By 2021, about 52.2 million tons of WEEE will be generated [11,12]. The recyclable noble metals in these waste materials are much more abundant than the natural ores, for example, the estimated concentration of gold in the WEEE is about 0.15 wt%
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