To address the key challenges of efficiently separating and recovering precious metals from waste printed circuit boards (WPCBs) and achieving a win-win outcome of economic and environmental benefits in the resource utilization of electronic waste, the following process is developed:

First, WPCBs are pulverized into particles via mechanical processing technology. The obtained particles are then separated into metallic and non-metallic fractions under the action of a high-voltage electrostatic field. After that, two liquid phase separation systems are constructed successively for the recovered metallic fractions: the Fe-Cu high-temperature liquid phase separation system and the Cu-Pb relatively low-temperature liquid phase separation system.

Next, by leveraging the selective partitioning rule of components in the WPCB metallic fractions in the aforesaid liquid phase separation systems, base metals and other non-ferrous metals are separated with high efficiency, while nearly all precious metals are enriched in the Cu-rich phase.

Subsequently, hydrometallurgical technology is adopted to separate and recover precious metals from the small amount of Cu-rich materials loaded with highly concentrated precious metals. This process can significantly reduce the consumption of chemical reagents during the separation and recovery of multi-component metals, and mitigate the ecological and environmental hazards posed by electronic waste.

The method for extracting gold from gold tailings comprises the following steps:

1)Mix gold tailings sand with water to prepare ore pulp;

2)Subject the ore pulp to ultrafine treatment to reduce the particle size to below 2 μm. A chemical reagent containing functional groups capable of forming coordination compounds with gold ions can be added either before or during the ultrafine treatment, so that the chemical complexation reaction proceeds synchronously with the ultrafine treatment; alternatively, the chemical reagent can be added after the ultrafine treatment to allow sufficient complexation reaction to complete;

3)Carry out solid-liquid separation and retain the liquid phase, which contains gold complex ions.

This extraction method boasts mild operating conditions, low production cost, low reagent consumption, fast extraction speed, and an extraction rate as high as 98%. Furthermore, the solid residue left after extraction can be further used to produce ceramic tiles, mineral admixtures for concrete and lightweight hollow wall materials. After drying, it can also serve as a filler for rubber or plastics, thus realizing full reutilization of resources and turning waste into wealth.

The process for recovering rare and precious metals via hydrometallurgical treatment of spent petrochemical catalysts falls into the technical field of hazardous waste treatment.

This process comprises a series of hydrometallurgical recovery procedures for rare and precious metals: slurrying, coarse grinding and ultrafine grinding leaching at ambient temperature, followed by subsequent steps including heated leaching, filtration and washing, platinum precipitation by cementation, and nickel recovery.

While improving the leaching efficiency of spent petrochemical catalysts, this process can shorten leaching duration, reduce energy consumption and lift the recovery rate of rare and precious metals. Meanwhile, waste gas is effectively treated, water is recycled, and a sound production environment is guaranteed.

This process is characterized by adopting a new leaching agent system of NH₃-NH₄F (or NH₃-NH₄HF₂) to replace the NH₃-(NH₄)₂CO₃ or NH₃-(NH₄)₂SO₄ system used in traditional ammonia leaching processes. The original process route of "high-temperature reduction roasting followed by atmospheric ammonia leaching" is thus simplified to direct atmospheric ammonia leaching. When coupled with solvent extraction and electrowinning, this method forms a new process flow for treating such ores.

This process has the advantages of short process flow, simple and convenient operation, low energy consumption, short leaching time and high copper leaching rate. It can be applied to the selective recovery of copper from copper oxide ores, and is particularly suitable for processing refractory copper oxide ores with high content of alkaline gangue.

This method belongs to the technical field of the metallurgical industry.

First, fine grinding is conducted to break the inclusions in carbon-sulfur-arsenic-bearing gold ore and liberate the encapsulated gold, creating favorable conditions for subsequent gold leaching. Next, gold is concentrated through jet-pulsed flotation, which effectively reduces the volume of ore to be processed in follow-up procedures.

Subsequently, oxidation reactions are carried out to convert arsenic into arsenate, sulfur into sulfate, and passivate the carbonaceous matter, so that fine-grained gold particles are fully exposed. After that, precipitation reactions are performed to transform arsenic into stable scorodite, eliminating the risk of arsenic re-leaching; meanwhile, sulfate and carbonate are converted into calcium sulfate and calcium carbonate respectively. Calcium carbonate is then separated and removed, and caustic soda (sodium hydroxide) is regenerated for recycling.

A cyanide-free gold leaching agent is adopted to extract gold from the pretreated gold ore with carbon, sulfur and arsenic removed. This green and eco-friendly reagent contains no toxic cyanide, and is environmentally compatible.

The entire green gold leaching process operates under ambient temperature and pressure at a near-neutral condition (pH 6–8), making it suitable for wide promotion and application.

This method follows a targeted process route: Sn is first leached and separated, followed by leaching of Cu from WPCBs. Next, Al, Ni and Zn are leached and recovered respectively, and the process concludes with the leaching and recovery of Au and Ag.

When recovering various rare and precious metals from WPCBs, this method enables sequential and orderly leaching of all target metals, realizing cascade recovery of rare and precious metals from WPCBs. As a key green recycling technology for waste resources, it supports the circular utilization of waste resources and mitigates environmental hazards from electronic wastes including WPCBs.

The impurity removal process is carried out as follows: Activated carbon is added into the pregnant leach solution obtained from gold heap leaching. After 10 to 30 days of adsorption, the adsorption-saturated activated carbon is extracted for desorption, producing desorption wastewater and desorbed activated carbon. The desorbed activated carbon is then sent for acid pickling treatment. The acidic wastewater generated from acid pickling, the aforementioned desorption wastewater, and the smelting wastewater produced during gold slime smelting are all delivered to a sedimentation tank, where high-efficiency impurity remover is dosed for impurity removal treatment. The resulting precipitates are subjected to pressure filtration and then stored in the warehouse.

The applied high-efficiency impurity remover features high impurity removal efficiency, fast sedimentation rate, and strong removal capacity for impurities including copper, mercury, zinc and nickel. It also has a wide adaptable pH range and will not interfere with the gold leaching process. This process realizes long-term recycling and zero discharge of the leachate, maintains impurities in the leachate at a low concentration to improve the gold leaching rate, and enables the recovery of impurity metals.

The process for recovering precious metals from spent precious metal catalysts mainly consists of the following steps: pretreatment of the precious metal-bearing spent catalysts, leaching of precious metals into solution, and purification and recovery of precious metals from the solution.

The leaching solution used in this process contains sodium hypochlorite, hydrogen ions, sulfate ions and phosphate ions, which boasts the merits of low cost, low pollution, low hazard and easy industrial scalability. In addition, the mixed acid of sulfuric acid and phosphoric acid at an appropriate ratio also has outstanding properties including stable performance, non-volatility and strong capacity to dissolve precious metals.

Furthermore, staged roasting is adopted for the pretreatment of precious metal-bearing spent catalysts. This process can burn off the carbon deposits on the spent catalysts more completely, facilitating the recovery of precious metals in subsequent steps and improving the corresponding recovery rate.

The method is characterized in that it comprises the following steps:

Grind the raw ore until the -0.075 mm particle fraction accounts for 60% to 80% of the total mass. Add 500-1200 g/t of sodium sulfide (Na₂S), 100-1000 g/t of sodium butyl xanthate, and 25-100 g/t of pine alcohol oil (dosages calculated based on the mass of raw ore) for flotation, to obtain copper concentrate and flotation tailings.

Subject the flotation tailings to magnetic separation at a magnetic field intensity of 0.35-1.30 T, to obtain magnetic concentrate and magnetic tailings.

Thicken and dewater the magnetic concentrate to a liquid-solid ratio of 2-3:1, add concentrated sulfuric acid to adjust the pH to 1, perform agitation leaching for 20 to 60 minutes, and carry out solid-liquid separation to obtain leachate and leaching residue. The leachate is treated via hydrometallurgical processes to obtain cathode copper.

The method of the present invention is a combined beneficiation-metallurgy process with a high comprehensive copper recovery rate. As a simple, efficient, economical, energy-saving and environment-friendly method for comprehensive copper recovery, it is applicable to mixed copper ores.