The process route of palladium-carbon waste catalyst, waste electronic slurry and other wastes is: roasting → roasting slag → dissolving precious metals → separation and purification.
The technological route of waste palladium electroplating solution is: replacement → slag replacement → precious metal dissolution → separation and purification.
The technological route of waste electronic components (integrated circuit boards, contacts and contacts) containing palladium is: classified disassembly → roasting → roasting slag → dissolving precious metals → separation and purification.
It should be pointed out that no matter what process is adopted, there must be perfect environmental protection facilities. For example, the roaster should be equipped with perfect dust removal facilities, and the waste gas and wastewater should be treated and discharged after reaching the standard.
Analysis and countermeasures of domestic palladium and platinum secondary resources recovery
At present, the country has not promulgated unified laws and regulations on the recovery of precious metal secondary resources, and it is difficult to concentrate the recovery of precious metal secondary resources. A small part is carried out in state-owned companies, and most of them are carried out in private and self-employed households. Under normal circumstances, the recycling of state-owned companies is more formal, the process is standardized, the equipment is in good condition, there are perfect waste gas and wastewater treatment facilities and the working environment is good. However, private and self-employed enterprises have chaotic recycling, backward technology and equipment, lack of corresponding waste gas and wastewater treatment facilities and poor working environment.
The recovery of palladium from waste electronic components containing palladium in Zhejiang and Guangdong is analyzed as an example.
Taizhou, Zhejiang Province is currently the largest dismantling center for used household appliances and electrical appliances in Asia. In Ningbo, Wenling, Wenzhou, Taizhou, Zhejiang, Dongguan, Puning, Chaoshan and other places, due to their proximity to the high seas, since the early 1990s, a large number of waste electronic components (integrated circuit boards, contacts, contacts) containing palladium (platinum) have been smuggled in from the high seas, and small workshops and smelters to recover palladium (platinum) from these "foreign garbage" are all over these places. Yongxing County, Chenzhou City, known as the "Silver Capital of China", also extracted a considerable amount of associated palladium, platinum and rhodium from the waste residue and waste liquid of Guangdong gold mines, smelters and electroplating electronics factories.
The process of recovering palladium in small workshops and smelters in coastal areas is very simple: waste electronic components containing palladium → roasting → nitric acid (or aqua regia) dissolution → ammonium chloride precipitation → water dissolution → ammonia water complexation → hydrazine hydrate reduction → crude palladium (90%). This process has the following disadvantages: ① The flue gas generated during the roasting of waste electronic components will cause certain harm to operators and nearby residents. (2) Nitric acid dissolving roasting slag will produce gases such as NO and NO2, which will pollute the air if discharged directly without treatment. (3) The grade of palladium produced is only about 90%, which can't meet the industrial requirements and needs to be sent to a special refinery for refining and purification.
At present, the annual output of palladium recovered from waste electronic components (integrated circuit boards, contacts and contacts) in Zhejiang and Guangdong provinces has reached 100 ~ 120t, which is 8 billion to 9.6 billion yuan based on the current 80,000 yuan /Kg palladium, and the annual output of recovered platinum has reached 2 million to 25t, which is 270,000 yuan /Kg platinum.
Because the waste electronic components containing palladium (platinum) come in through some informal channels, and there are no formal invoices, most of these small workshops and smelters have incomplete procedures and cannot deduct tax bills, resulting in high taxes. Therefore, after they are processed into crude palladium, some of them are returned to Hong Kong, and then sold to Japan, South Korea and Taiwan Province Province through Hong Kong, which is mainly used to make electronic components such as circuit boards, contacts and contacts. Part of it is sold to other domestic enterprises or individuals in the form of no invoice.
In view of the backward technology and equipment of some small smelters, there are no corresponding waste gas and wastewater treatment facilities, which cause serious pollution to the environment, and at the same time, they do not invoice and pay taxes, which makes no contribution to the national GDP income and does not conform to the relevant national tax policies. It is suggested that the relevant state departments should improve relevant laws and regulations as soon as possible, ban small factories with small scale and heavy pollution, support a number of enterprises with advanced technology and equipment, a certain scale and perfect three wastes treatment facilities from taxation policies, vigorously develop circular economy, and give help in introducing talents and technical consultation, so as to make the recovery of palladium and platinum secondary resources in China enter a virtuous circle.