Precious metal recycling is a systematic process, with core steps including detection and grading, pre-treatment, metal extraction, and refining and purification.
Testing and grading form the foundation for determining scrap value, typically employing non-destructive testing techniques with specialized equipment to rapidly identify metal content and types. The pre-treatment stage involves crushing, sorting, and removing surface impurities to prepare materials for subsequent extraction. Physical pre-treatment technologies now achieve micron-level precision disassembly. Through multi-stage crushing, magnetic separation, eddy current separation, and other processes, metals are efficiently separated from non-metals within mixed scrap.
The metal extraction stage employs pyrometallurgy, hydrometallurgy, or biometallurgy depending on scrap type. Innovations in pyrometallurgy combine traditional high-temperature smelting with plasma technology, where plasma torches reach 10,000°C to thoroughly decompose organic matter in complex scrap while simultaneously enriching multiple metals.
Hydrometallurgy employs various chemical solutions to selectively dissolve and separate precious metals. Refining and purification are critical steps for obtaining high-purity metals, with techniques like electrolytic refining and chemical reduction achieving purities exceeding 99.95%.
Platinum group metals (PGMs) include platinum, palladium, rhodium, iridium, and ruthenium. Sharing similar physicochemical properties, their recovery processes also share commonalities. These metals are typically found in industrial catalysts, electronic waste, and jewelry scrap, presenting high recovery value.
Recovering platinum group metals requires specialized techniques, typically employing hydrometallurgical processes. These include aqua regia dissolution, solvent extraction, ion exchange, and precipitation reduction. Pyrometallurgical methods are also commonly used for high-grade platinum group metal waste, separating precious metals from base materials through high-temperature smelting.
For recovering platinum group metals from automotive catalysts, a "dissolution-precipitation" process developed by German companies enables selective precipitation of these metals by controlling pH and temperature. This achieves 99.99% purity at a cost 35% lower than refining from primary ore.
The technical challenge in platinum group metal recovery lies in their similar chemical properties, requiring precise control of process parameters for separation and purification. Internationally advanced companies employ innovative technologies such as plasma smelting and supercritical fluid extraction to enhance recovery efficiency and product purity.
The process of recycling precious metal platinum typically begins with a pretreatment stage. Platinum-containing scrap is cleaned, dried, and mechanically crushed to increase its surface area. This is followed by oxidative roasting, which converts platinum into an oxidized state to enhance its solubility.
Next, a aqua regia dissolution process is employed. Under controlled temperature and acid ratio conditions, platinum is converted into soluble compounds. The filtered solution undergoes reduction precipitation, where reducing agents like hydrogen gas or formaldehyde reduce platinum ions into metallic platinum precipitates.
The precipitated platinum is filtered, washed, and calcined at high temperatures to yield pure platinum metal powder or lumps. Internationally advanced enterprises employ plasma smelting technology to process platinum-containing waste alumina, reducing energy consumption by 30% compared to traditional methods.
The recovery process begins with intelligent collection and traceability management of waste materials, utilizing RFID technology to track ruthenium-containing substances. The pretreatment stage employs a "crushing-magnetic separation-air classification" process to separate metals from plastics in the waste, elevating purity to 95%.
The extraction phase utilizes a combined "pyrometallurgical smelting + hydrometallurgical refining" process. Ruthenium-containing waste is melted in a 1500°C electric arc furnace, separating ruthenium from other metals with a recovery rate of 92%. Residual materials proceed to the hydrometallurgical workshop, where they are dissolved using aqua regia and ruthenium is precipitated via thiourea derivatives.
The refining stage utilizes vacuum distillation equipment. Within a liquid nitrogen environment at -196°C, controlled temperature gradients separate ruthenium from other platinum group metals. This method achieves ruthenium purity exceeding 99.99%, meeting the semiconductor industry's demand for ultra-pure materials.
The rhodium recovery process resembles that of other platinum group metals but requires more refined separation techniques. Since rhodium often coexists with other platinum group metals, precise detection of its content and composition is essential prior to recovery.
The recovery process typically employs hydrometallurgical techniques, including aqua regia dissolution, solvent extraction, and selective precipitation. Specialized extractants developed internationally effectively separate rhodium from other precious metals based on its unique properties.
Refining stages predominantly employ electrolytic refining or chemical reduction methods to obtain high-purity rhodium metal. The technical challenge in rhodium recovery lies in its high chemical inertness, requiring high temperatures, pressures, or specialized catalysts for effective dissolution and processing.
The precious metal palladium recovery process begins with acidification pretreatment, adjusting the waste liquid's pH to between 2 and 3 to dissolve palladium ions from complex compounds. This is followed by liquid-liquid extraction, where trioctylamine organic solvent is added. Palladium selectively transfers palladium ions from the aqueous phase to the organic phase.
The mixture is then stirred at a constant temperature of 25°C for 30 minutes, achieving an extraction efficiency exceeding 95%. The stripping process uses a thiourea solution to transfer palladium ions from the organic phase back to the aqueous phase, concentrating the palladium from tens of ppm in the original waste liquid to several thousand ppm.
The chemical reduction stage occurs in a temperature-controlled reactor. Hydrogen gas is slowly introduced into the palladium ion solution while maintaining a strict temperature range of 60–80°C. Precipitated metallic palladium forms as a dark gray powder. Following dissolution, recrystallization, and electrolytic refining, the final product achieves a purity of 99.99%.
The recovery process for precious metal iridium requires exceptionally precise operations, as iridium ranks among the world's most corrosion-resistant metals. The procedure begins with thorough sorting and evaluation of scrap materials to determine iridium content and contamination levels.
During pretreatment, iridium-containing scrap is pulverized to a 100-200 mesh particle size, increasing its reaction surface area. This is followed by high-temperature oxidation roasting at 800-900°C to convert iridium into a more soluble oxide form.
The dissolution stage employs an autoclave, using aqua regia or mixed acids under high temperature and pressure conditions. This process may require 24-48 hours. The resulting solution undergoes multi-stage filtration to remove insoluble impurities.
The purification stage employs ion exchange resins or solvent extraction technology to selectively separate iridium ions. Finally, high-purity iridium metal powder is obtained via ammonium salt precipitation or high-temperature hydrogen reduction. Further smelting yields iridium ingots.
The precious metal gold recycling process begins with an online appointment, where details such as gold type and estimated weight are provided. This is followed by testing using a spectrometer to measure purity and a high-precision electronic scale to determine weight, ensuring all equipment is professionally calibrated.
After testing, a recycling quote is provided based on the results and current market prices. If the quote is accepted, the transaction proceeds with a signed agreement specifying the gold details, price, and payment method.
Payment is finalized according to the agreed method. Throughout the process, customers should ensure recyclers use professional equipment, request to observe the testing procedure and results, and stay informed about market conditions to secure a fair price.
Recovering gold from precious metals is relatively straightforward due to gold's stable chemical properties and established recovery techniques. However, it remains crucial to choose legitimate recycling channels to avoid fraudulent practices.
A research team at Flinders University in Australia has developed a revolutionary gold extraction technology. By combining trichloroisocyanuric acid (a harmless compound commonly found in swimming pool disinfectants) with saltwater pools, it creates an effect that dissolves gold. Specially designed sulfur-rich polymers then precisely capture the gold elements. This method is more environmentally friendly than traditional cyanide processes and can efficiently recover gold from electronic waste.
Leading international precious metal recycling companies include established firms such as Johnson Matthey (UK), Heraeus (Germany), Umicore (Belgium), and Hong Kong Dongsheng Precious Metals Recycling. These companies boast extensive histories and advanced technological expertise. They typically offer comprehensive precious metal recycling, refining, and trading services, backed by international certifications and quality assurance systems.
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