An Overview of the Development of the Precious Metals Recycling Industry in Our Country

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The eight platinum group elements—osmium, iridium, platinum, ruthenium, palladium, rhodium, gold, and silver—are widely used in industry due to their excellent corrosion and oxidation resistance, high melting points, good electrical conductivity, and catalytic activity. They have become important materials for modern industry and defense manufacturing. However, due to limited mineral reserves, difficulties in production, and low output, prices continue to rise. Many industrially developed countries are turning their attention to the recycling of precious metal resources – this inexhaustible \"rich mine\" – and they regard the recovery of precious metal waste on an equal footing with the exploitation of mineral resources. Summary: According to available data, over 85% of the precious metals that have been used in the world have been recycled and reused. Recently, the annual profits of electronic waste processing companies in the United States have reached $25 million to $30 million. According to statistics, it costs about $300,000 to extract 1 ton of silver, while only $10,000 is needed to recycle 1 ton of silver ； It costs $250 to $300 to extract 1 ounce of gold, while only $100 is needed to recycle 1 ounce of gold. Another example: by recycling the used batteries from old phones and accumulating 1 ton of them, 100 grams of gold can be extracted from them ； In contrast, ordinary gold-bearing ore (sand) can yield only a few grams of gold per ton, with the maximum amount being no more than a few dozen grams. Despite years of development, China has initially established a relatively comprehensive system for the recycling of used precious metals, which mainly focuses on the recycling of used precious metal jewelry and waste materials used in jewelry production, as well as the recycling of tailings from precious metal mines and slags from smelting and refining plants, in addition to the recycling of waste residues (liquids) from electrolysis and electroplating processes. However, compared with developed countries, the recycling of precious metal recyclables in our country started late, and the technology is relatively backward. Recycling operations are conducted in a crude manner, and an effective system for precious metal recycling along with corresponding management mechanisms have not yet been established; therefore, policy support is urgently needed. At present, there are approximately 150 to 200 companies in our country that recycle used precious metals; these recycling units are scattered and do not form a cohesive scale ； Moreover, the recycling equipment is rudimentary, the technology is outdated, and the recovery rate is low, resulting in waste of resources and energy ； The recycling channels are chaotic, with a lack of **effective supervision. Small workshops for the recycling of precious metal waste are the majority. The emergence of these individual operators, while playing a certain role in the recycling of precious metal waste, has caused serious problems such as environmental pollution. Main sources of recycling materials for precious metals (1) Recovery of precious metals from mine tailings and processing waste. In order to improve their economic efficiency, mining companies and those involved in the processing of precious metals conduct thorough research on the recovery of precious metals from tailings and processing waste. These companies are willing to invest in improving the rate of precious metal recovery, and they have well-developed recovery systems; precious metals, as by-products, can generate economic benefits for these enterprises. The platinum ore resources currently mined around the world can be mainly divided into two categories: placer platinum ore and associated ore. Scheelite was once widely distributed in over 100 regions across more than 50 countries, and it was the main resource for production over the more than 100 years prior to the 1920s. Scheelite can be processed through simple gravity separation to yield a platinum group metals concentrate composed mainly of coarse platinum and osmium-iridium compounds, which have a high density of about 20 g/cm³; these compounds can then be separated and refined using chemical methods to produce pure metals of platinum, iridium, and osmium ； The situation with symbiotic ores is more complex; these ores contain over 10 valuable elements such as platinum, palladium, osmium, iridium, ruthenium, rhodium, gold, silver, nickel, copper, cobalt, iron, and sulfur. They represent a precious resource that must be utilized in a comprehensive manner. The main resource deposits, such as those in Bushveld in South Africa, Stillwater in the United States, Norilsk in Russia, Sudbury in Canada, and Jinchuan in China, are all symbiotic ore deposits. The separation of base metals from precious metals is crucial for determining the methods and efficiency of tailings recovery; it constitutes the core of comprehensive utilization processes for sulfide ores and a key focus in technological development. The goal is to achieve both the extraction of copper, nickel, and cobalt products and the enrichment of precious metal concentrates at the highest possible recovery rate. Compared with other **large-scale symbiotic ores, the platinum group metals content in China’s Jinchuan symbiotic ores is the lowest; the technical challenges associated with their comprehensive extraction are greater, and production is more constrained by the scale of nickel and copper production. Effective processing methods must be developed in order to achieve high recovery rates. From ore to precious metal concentrate with a purity of 50%, the enrichment factor required throughout the entire processing chain is 80,000 times in South Africa and Canada, while in Jinchuan, China, this figure is 1.5 million times. The higher the required enrichment factor, the more enrichment steps are needed, the longer the process becomes, and the lower the recovery rate of precious metals may be. (2) The recycling of used gold and silver jewelry also includes the recycling of precious metals used in dentistry as well as other precious metal ornaments used in daily life. Most used gold and silver jewelry is recycled by banks or jewelry companies (stores). After the gold and silver market was opened up, **, collective, and individual jewelry stores can all recycle gold and silver, which has resulted in a fairly well-developed system for its recycling. Recycling of this portion of waste gold and silver accounts for a significant proportion, especially gold. The consumption of gold and silver is primarily used in jewelry, electronics, dentistry, industrial decoration, reserves, commemorative coins, official currency, electroplating, pens, clocks, and more. According to statistics, the current global gold consumption amounts to 3,235.1 tons, of which 2,840.3 tons are used in the jewelry industry, accounting for 87.8%. Since the beginning of the 21st century, China’s annual gold consumption has remained around 210 tons ； In 2004, total gold consumption in mainland China increased by 3%, reaching 213.2 tons, which placed it fourth in the world, behind India with 855.2 tons, the United States with 409.5 tons, and Saudi Arabia with 228 tons. Currently, the average gold possession per person in Asia is 10 grams, while in China it is only 0.2 grams. As domestic per capita consumption levels rise, this figure is set to increase further. Given the long history of the use of precious metals in jewelry in our country, a well-developed system for recycling such waste precious metals exists. In some areas, jewelry recycling and reprocessing have become key industries that form the backbone of the local economy. For example, in Yongxing County, Hunan Province, where there are over 30,000 people employed in the metallurgical industry, more than 1.2 million tons of waste residues, scrap, and liquid waste containing precious metals such as gold and silver are collected each year from various parts of the country. Using unique processing techniques, these materials are refined to produce 1,700 tons of precious metals such as gold, silver, palladium, and platinum per year. This generates an annual output value of 4.5 billion yuan, with taxes amounting to 45 million yuan. Yongxing has become the largest national base for the recycling of precious metal \"three wastes\". Yongxing does not possess mineral resources such as gold or silver. Over 300 years ago, the hardworking people of Yongxing began to collect \"waste materials\" from various parts of the country in order to smelt and process them. In recent years, the county has guided this industry toward large-scale, standardized, and intensive operations. More than 130 enterprises of a certain scale that meet environmental standards and are scattered across 4 towns were concentrated in the smelting industrial park. At present, over 80 companies have an annual output value of more than 5 million yuan, and 15 of them pay taxes of over 1 million yuan. In 2002, the county was awarded the title of “China’s Silver Capital” for its silver production of 1,500 tons. (3) Recovery of precious metals from electrode sludge and electroplating wastewater: Manufacturers involved in the electrolytic and electroplating processes of non-ferrous metals as well as precious metals can treat electrode sludge and electroplating wastewater to recover the precious metals contained within them. In electrolytic copper plants, the anode sludge generated during the electrolysis process contains miscellaneous metals; its chemical composition is shown in the table below. For the anode sludge from certain copper plants, Cu, Ni, Au, Ag, Pt, and Pd are generally considered valuable elements that should be recovered. (4) In the photographic film industry, the largest amount of silver is consumed in photosensitive materials, which is why manufacturers in this sector attach great importance to the recovery of silver from these materials, and generally establish comprehensive recycling systems for this purpose. Kodak film in the United States has a 70-year history of silver recycling, and now boasts comprehensive recycling networks worldwide. The largest user of silver is the photography industry. According to available data, the amount of silver consumed each year in photographic materials accounts for about one-third of the total silver used in industrial applications. Of this amount, 90% is dissolved in the developing solutions (mainly in fixing or rinsing solutions), and 100% of that silver can be recovered. In recent years, recycled silver has accounted for over 1/4 of the world’s total silver supply. The proportion of recycled silver is even higher in developed countries; in the United States, the amount of silver recovered from recycled materials was 1,700 tons in 1999 and 1,600 tons in 2000, accounting for over 40% of the country’s total refined silver production (4,000 tons). There are 16 large-scale silver recycling plants in Japan, along with over 150 companies that deal with the recycling of waste materials from the photography industry; these facilities recycle 400–500 tons per year (all waste materials containing 0.1% silver in Japan can be recycled). The former Soviet Union also recovered over 600 tons of silver from various wastes each year. In our country, 200 tons of silver are used each year in the photography industry, and 80% of this silver ends up in waste liquids during the processing of film and negatives. If it were recovered, the amount of silver that could be obtained would be over 150 tons. Based on the world average recycling level, our country could also recycle 375 tons of silver each year. (5) Recovery of gold and silver from used electrical appliances – the recovery of precious metals from such appliances represents the main trend in the precious metals recycling industry, and it will remain the sector with the fastest growth in terms of the amount of recycled precious metals available as raw materials for a long time to come. Used electrical appliances include computers, televisions, refrigerators, washing machines, and mobile phones, among others. These products have been available in our country for only a short time, and there are no relevant regulations regarding the recycling of these waste products. In some areas, precious metals are recovered from imported electronic waste using outdated recovery techniques, with no environmental protection measures in place, resulting in severe pollution. Over time, some electronic products in the country also reach the end of their useful life. Starting from 2003, at least 5 million televisions, 4 million refrigerators, and 6 million washing machines will need to be discarded each year in China. Japan has been importing industrial waste for decades; currently, 40% of the precious metals recovered come from imported industrial waste. As Japanese companies establish factories overseas, most of the electronic waste and other industrial waste also ends up abroad. In those developing countries, **there are usually no means for waste recycling or purification; Japanese companies cannot bear to see this \"golden waste\" go to waste, so they purchase it on-site and then ask the ships that transport raw materials from their home country to bring those materials back with them on their return journey. Electronic waste contains various precious metals such as gold, platinum, and palladium. Nippon Asahi Puri, which is engaged in the recycling of precious metals, established a 100%-owned precious metals recycling company named \"Shanghai Asahi Puri Environmental Technology Co., Ltd.\" in Shanghai, China, on March 12, 2003. The new company will first deal with the plating waste liquid emitted from electronic components and semiconductor factories, as well as the recovery of precious metals such as gold and silver from the scraps of electronic components ； Later, the company considered expanding its treatment scope to photo development waste liquids and scraps from jewelry processing. All the recovered metals are sold to China, thereby establishing a system for the recycling of precious metals in that country. (6) Recovery of platinum group precious metals from spent catalysts: The precious metal elements included are gold, silver, platinum, palladium, rhodium, osmium, iridium, and ruthenium. Except for gold and silver, which are rarely used as catalysts, the other six elements are widely utilized. Platinum group metals are extensively applied in catalysts for hydrogenation, oxidation, dehydrogenation, hydrolysis, ammonia synthesis, methanol synthesis, hydrocarbon synthesis, acetic acid synthesis, hydroformylation, carbonylation, and ortho-hydroxylation. When used as catalysts, the most commonly used precious metals are platinum, palladium, and silver. In recent years, due to the increasing use of precious metal catalysts for automobile exhaust purification, the amount of platinum group metals that serve as catalysts in these catalysts has been rising year by year. Once catalysts become poisoned and lose their functionality, a large portion of them cannot be regenerated; as a result, a huge amount of waste precious metal catalysts are generated worldwide each year. It has therefore become increasingly important and urgent to find appropriate ways to handle and make full use of these secondary resources. Currently, the platinum group metals consumed annually in automotive catalysts around the world account for 30% to 42% of the total platinum consumption, palladium accounts for 56% to 76%, and rhodium accounts for 95% to 98%, all of which hold the leading position in their respective applications. Over the past 20 years, automotive catalysts that make extensive use of precious metals have become a major environmental protection technology and new materials industry on the international stage, showing strong growth trends. The Precious Metals Plant of Yangzi Petrochemical Maintenance Company recovers sponge palladium from the waste palladium-carbon catalysts generated by its purified terephthalic acid production facility. With a production capacity of 1,000 kg per year, it produces high-purity palladium chloride, which is then fed back into the acetic acid production unit associated with the purified terephthalic acid facility to be used as a catalyst in the oxidation of ethylene to acetaldehyde, thereby completely replacing imported catalysts. It is understood that in recent years, only in the platinum reforming process of the petrochemical industry are catalysts containing precious metals such as platinum, rhodium, and palladium used; these precious metals account for about 3% of the catalyst’s composition. The service life of such catalysts is 3 to 5 years, and the total amount used across the entire industry is around 600 tons, of which 1,800 kilograms consists of precious metals. In chemical urea production plants, metal mesh containing gold, platinum, rhodium, and palladium is used, with a service life of half a year; the annual consumption amounts to 200 kilograms. (7) Recovery of precious metals for functional materials Functional materials refer to those that exhibit special properties such as electrical, magnetic, optical, biological, and chemical properties in addition to mechanical properties. Due to their high electrical and magnetic conductivity, precious metal materials play a significant role in the field of functional materials, being primarily used in temperature sensing sensors and sensitive components. Currently, with the rapid development of electronic technology, the development of new functional materials is also advancing swiftly. Recycling functional materials that have become obsolete or failed is another area for the recovery of precious metals. Technology of recycling precious metals: At present, as research into precious metal recycling technologies continues to advance, various techniques are constantly evolving, with new innovations in this field emerging every day. However, the three most representative methods are: pyrometallurgical enrichment, hydrometallurgical enrichment, and microbial adsorption. (1) Pyrometallurgical enrichment: Pyrometallurgical enrichment boasts strong adaptability when dealing with complex waste. At present, almost all of the world’s renowned precious metal recycling plants use pyrometallurgical enrichment processes. Pyrometallurgical enrichment includes processes such as smelting enrichment, pyrometallurgical chlorination and high-temperature volatilization, and incineration. Its main processes are combustion and melting. The use of large rotary kilns during combustion allows the material weight to be reduced by 30%, and an exhaust gas purification device is installed at the end of the kiln. The material after combustion is ground, screened, and magnetically separated, and the resulting products are then melted in induction furnaces, refined chemically, or refined through electrolysis. (2) Wet enrichment: Wet enrichment is the main process for processing gold and silver ores. To date, the cyanidation method remains the most important and widely used approach for processing raw ore and concentrate. The principle of wet enrichment is to first crush and grind the gold-bearing ore to a particle size at which the gold particles separate from the matrix or minerals, then leach the gold using an oxidizing agent, and finally separate the gold-containing leachate from the leach residue. (3) Microbial adsorption of metals refers to the process of using live or dead microbial cells and their metabolic products to adsorb metals through physical and chemical mechanisms (including complexation, deposition, redox reactions, ion exchange, etc.). In August 2003, a research team at the University of Birmingham in the UK invented a much faster and cheaper method for recovering precious metal catalysts used in cars, and filed for a patent. The new recycling method involves immersing the metal in nitric acid and hydrochloric acid, after which it passes through a reactor containing bacteria; the metal then deposits on the cell walls, and it can be collected for recycling. The recycling process takes only 15 minutes, with an efficiency of about 90%. For refractory gold ores containing arsenic and sulfur, the gold is enclosed within sulfide minerals, resulting in a very low leaching rate of gold when using conventional cyanidation methods. If sulfide-containing minerals are destroyed through bacterial pre-oxidation to release gold, which is then leached using cyanide, the gold leaching rate can generally reach 90%. This method not only achieves a high leaching rate for gold, but also does not produce waste gases containing arsenic and sulfur; furthermore, the waste residue is stable and does not pollute the environment. In summary, overall, China does not yet have a well-established system for the recycling of precious metals; there are also no dedicated regulatory agencies. To date, it is not possible to determine the total amount and recycling rate of gold, silver, and platinum group metals recycled in the country. A small number of enterprises in our country already possess the relevant technologies and equipment for recycling electronic waste, and they should receive **policy support. Companies that recycle precious metals must give top priority to environmental protection; they need to use advanced technical equipment and processes to make full use of precious metal waste, while ensuring that the resulting secondary waste meets environmental standards. At the same time, **it is necessary to fully leverage the role of technical supervision and regulation by formulating a set of technical specifications for precious metal recycling, as well as standards for raw materials and products that suit China’s current conditions. This will help accelerate the establishment of a market-based system for precious metal recycling and regulate this market. Additionally, the technical advantages of these new standards should be utilized to encourage precious metal recycling enterprises to pursue technological innovation, thereby speeding up the development of advanced recycling technologies for precious metals.