Platinum group metals (PGMs) are widely utilized in the preparation of various industrial catalysts due to their excellent comprehensive properties. After long-term service, industrial catalysts will fail and turn into spent materials that still contain precious metals such as platinum, palladium and rhodium, holding extremely high recycling value. Focusing on precious metal recycling equipment and process optimization, Henan Yusai Precision Machinery Co., Ltd. has accumulated rich technical experience in the field of spent catalyst resource utilization. At present, a mature technical system has been formed for the recovery of PGMs from spent catalysts in industry. Based on different processing principles and technical routes, six mainstream recovery methods have been developed, which are applicable to spent catalysts with different carriers and impurity contents to meet diverse industrial recycling requirements.
The high-temperature volatilization method belongs to the dry recovery process. Under precisely controlled high-temperature roasting conditions, the PGMs in spent catalysts undergo oxidation and chlorination reactions and are converted into volatile metal oxides or chlorides. The gaseous precious metal components are absorbed and enriched by special equipment, and high-purity platinum group metals can be finally obtained through subsequent purification and reduction procedures. This method is suitable for spent catalysts with simple components and good high-temperature reaction adaptability.
The carrier dissolution method is a commonly used wet recovery process, which is mainly applied to alumina-based spent catalysts. Taking advantage of the chemical stability difference between alumina carriers and PGMs, hydrochloric acid, sulfuric acid, liquid alkali and other solvents are adopted to dissolve and decompose the catalyst carrier. In contrast, PGMs with stable chemical properties remain in the leaching residue. After filtering and collecting the residue, precious metals can be recovered via refining and purification. This process features simple operation and stable recovery performance.
The selective dissolution method is a high-precision wet process with a technical principle opposite to that of the carrier dissolution method. This method retains the complete catalyst carrier without damage. Special selective solvents are used to targetedly dissolve and leach PGM components from the catalyst while keeping the carrier intact. After solid-liquid separation to remove solid carriers, the metal-containing solution is subjected to extraction and refining to complete the recovery process. It has the advantages of low impurity introduction and high purity of finished products.
The total dissolution method is applicable to spent catalysts with complex components and high impurity contents. A strong dissolution system is adopted to completely dissolve the catalyst carrier, impurities and PGMs to form a mixed leachate. On the basis of differences in physical and chemical properties, solvent extraction and ion exchange technologies are used to separate PGM ions from the solution, and the final recovery is realized via reduction and refining procedures. This process boasts strong universality and is suitable for large-scale industrial treatment of complex materials.
Pyrometallurgical smelting is a mature dry metallurgical process that requires no acid or alkali solvents. Spent catalysts are melted at high temperatures, and PGMs are enriched into high-grade alloy materials by virtue of the differences in melting point and density of each component, while carriers and impurities form slag and are separated and discharged. The enriched metal materials can be refined and purified to obtain finished products. This technology is characterized by large processing capacity and strong anti-interference ability against impurities, making it suitable for the treatment of large-batch spent catalysts with high impurity content.
The combustion method is a special recovery process for carbon-based spent catalysts. Carbon-based spent catalysts are put into a special kiln and burned under controlled temperature to remove carbon carriers, obtaining calcine rich in platinum group metals. Subsequently, aqua regia dissolution or aqueous chlorination is applied to leach precious metals from the calcine, and PGMs can be recovered after separation, purification and reduction. This method can efficiently remove carbon impurities and simplify the subsequent purification process.
Each of the six recovery processes has its unique advantages, disadvantages and applicable scenarios. In actual production, a single process or combined processes are flexibly selected according to the carrier type, metal content and impurity condition of spent catalysts. Supported by precision manufacturing and process upgrading technology, Henan Yusai Precision Machinery Co., Ltd. provides matched professional equipment and systematic technical solutions for spent catalyst PGMs recycling, effectively balancing recovery efficiency, product purity, production cost and environmental performance, and realizing efficient and cyclic recovery of platinum group metals.
