The procedures are as follows:

a. Gold ore grinding;

b. Stirring and briquetting;

c. Roasting;

d. Crushing and mixing;

e. Chemical extraction;

f. Pressure filtration;

g. Electrolysis.

This method adopts the roasting technology for solid block crude gold alloy (doré bullion), enabling multiple recovery of residual gold from waste slag and waste liquor generated in each process section. The whole extraction process only requires one production line, featuring high product yield and extremely low residual gold content in discharged impurities.

Activated carbon is added into the pregnant leach solution from gold heap leaching. After 10 to 30 days, the adsorption-saturated activated carbon is collected for desorption, by which desorption wastewater and desorbed activated carbon are obtained.

The desorbed activated carbon is subjected to 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 into a sedimentation tank, where high-efficiency impurity remover is dosed for impurity removal. The resulting precipitate is treated by pressure filtration and then sent to storage.

The high-efficiency impurity remover, which features high impurity removal efficiency, fast sedimentation speed, capacity to remove impurities such as copper, mercury, zinc and nickel, a wide applicable pH range, and no adverse impact on gold leaching. The process realizes long-term recycling and zero discharge of the leaching solution, maintains impurities in the leaching solution at a low concentration to improve the leaching rate, and enables the recovery of impurity metals.

This is a schematic process flow diagram for gold recovery from electronic waste via the combined iodide leaching-electrodeposition technology. The core of this process lies in the use of the iodine-iodide redox couple as the leaching agent, which reacts with gold to form stable, soluble gold-iodide complexes that dissolve into the solution.

Subsequently, the gold complex-laden leachate is fed into the electrodeposition system. With an electric current applied across the electrodes, gold ions are reduced to elemental gold and deposited on the cathode surface, achieving both efficient gold recovery and the regeneration and recycling of the iodine-based leaching agent. This schematic of the integrated process highlights the potential of the iodide-based method as a highly efficient, highly selective cyanide-free alternative. Its integrated "leaching-recovery-regeneration" design particularly embodies the green metallurgy philosophy of closed-loop circulation and reagent reuse.

However, this technical route also clearly identifies the key challenges that must be addressed for its industrial application, including cost control of iodine reagents, the impact of interfering ions on selectivity in complex systems, optimization of electrodeposition efficiency, and stable operation of the entire system during engineering scale-up.

The rapid gold leaching method, which extracts gold from gold ores using a mixed solution of bromate, iron salt and acid, is a leaching process with the advantages of simple operation, fast leaching rate and excellent process feasibility. Its specific steps are as follows:

Crush and grind the gold ore until the fraction of particles passing through a 200-mesh sieve accounts for more than 80% by mass.

Add the leaching solution to the ore powder obtained in Step 1 at a mass ratio of 15~40 parts ore powder to 100 parts leaching solution. Conduct stirred leaching for 10~120 minutes under ambient temperature and pressure, with the stirring speed controlled at 100~800 rpm.

Filter the ore pulp obtained in Step 2, rinse the leach residue thoroughly, and recover gold from the collected filtrate.

This process is not only applicable to easy-to-process gold ores, but also delivers satisfactory leaching performance for high-sulfur, high-arsenic carbonaceous refractory gold ores. It eliminates the need for oxidative pretreatment, thus reducing the complexity of the leaching process and production costs. This gold leaching method features simple process flow, fast leaching speed and high gold leaching rate. Gold in the filtrate is easy to recover, the reagents used for leaching are non-toxic and harmless, and no toxic or hazardous substances are generated during the entire leaching process. Being environmentally friendly, this process holds promising application prospects in industrial production.

the process flow and core reaction principles of the hydrochloric acid oxidative leaching technology for recovering precious metals from electronic waste (e-waste). The chemical foundation of this technology is that chloride ions (Cl⁻) act as ligands in an acidic environment, and react with precious metals (such as gold, platinum, palladium, etc.) to form soluble chloro-complexes (e.g., tetrachloroaurate anion [AuCl₄]⁻), thus realizing selective dissolution and separation of precious metals.

the complete procedure from raw material pretreatment, acid leaching, solid-liquid separation to final metal recovery, and elaborates on the dissolution mechanisms of different precious metals through specific chemical reaction equations.that as a non-cyanide alternative process with lower environmental risks, this chloride-based leaching method has significant advantages over conventional processes (especially traditional cyanidation) in terms of both efficiency and environmental performance.

However, the process flow also explicitly reveals the key challenges faced by this technology in practical applications, including severe corrosion of process equipment caused by the highly acidic, chloride-rich environment, the requirement for precise control of reaction conditions (such as temperature and chloride ion concentration) to avoid side reactions, as well as the technical difficulty of efficient separation and purification of target precious metals from the complex pregnant leach solution (PLS).

The process commences with the dismantling and pretreatment of waste printed circuit boards (WPCBs). After crushing and liberation, the feedstock enters the core high-temperature smelting stage. During this phase, organic components are pyrolyzed into gases and oils, ceramic constituents form molten slag, while metals are enriched in the copper matte.

Subsequently, the copper matte is processed through converting and electrolytic refining to yield cathode copper with a purity as high as 99%. Eventually, precious metals such as gold (Au), silver (Ag) and platinum (Pt) are concentrated in the anode slime generated during electrolysis, and further extracted via anode slime refining.

This flow chart clearly demonstrates that although pyrometallurgical technology can form a complete industrial chain covering the whole process from pretreatment to precious metal recovery and achieve high metal enrichment and recovery rates (Au, Pd > 95%), it continuously produces waste gas containing pollutants including CO₂, CO, zinc (Zn), tin (Sn) and mercury (Hg), as well as waste slag rich in impurities (e.g. Sn, Fe) during operation. This also intuitively confirms that the technology faces core challenges of high energy consumption and severe secondary environmental pollution.

The precious metal enrichment method for iron-precious metal alloys obtained via electric arc furnace (EAF) smelting enrichment is particularly applicable to iron-precious metal alloys produced from self-produced low-grade precious metal-bearing materials generated during precious metal smelting, when EAF smelting is adopted for precious metal collection.

The pyrometallurgical smelting process using iron as a collector is one of the key processes for recovering platinum group metals (PGMs) from spent automotive exhaust catalysts and other PGM-containing catalysts. It mainly includes two enrichment routes: EAF smelting and plasma furnace smelting, both of which are suitable for treating low-grade precious metal materials.

Low-grade precious metal materials are mainly divided into two categories: the first is secondary resource materials represented by spent automotive exhaust catalysts and petroleum refining catalysts; the second is self-produced low- represented by neutralized wastewater residues, chlorination insoluble residues and other by-products generated in the precious metal smelting process.

The method comprises the following steps:

(1) Mechanically crush rare and precious metal-bearing slag materials, add slagging agents and low-value metals, and mix thoroughly to obtain feedstock;

(2) Feed the said feedstock into a pyrometallurgical furnace for smelting, and separate the smelted products to obtain precious metal alloy and smelting slag;

(3) Cool the said precious metal alloy via a combined cooling mode integrating natural cooling and forced water cooling, then conduct mechanical crushing and beneficiation separation to obtain precious metal concentrate and tailings respectively; the tailings are returned to the low-value metal storage for reuse;

(4) The said precious metal concentrate can be sold directly, or sent to the precious metal extraction process for separation and purification of precious metals.

By selecting low-value metals that are readily available for mining and metallurgical enterprises, and leveraging their physicochemical properties as well as adjusting the mixing ratio of raw materials, enrichment of target metals through pyrometallurgical smelting can be achieved. Meanwhile, the by-products can be reused or stockpiled as general solid waste, without causing secondary environmental pollution.

The rapid gold induction melting furnace leverages electromagnetic induction technology. It generates eddy currents inside the metal via an alternating magnetic field, enabling fast and uniform heating and melting. This heating method not only delivers high efficiency, but also significantly reduces oxidation and decarburization, thus guaranteeing the high purity of gold. Compared with traditional melting methods, the induction melting furnace heats at a much faster rate, completing the entire melting process in a short time while preserving the purity of the metal.

For metallurgical applications, the rapid gold induction melting furnace has remarkable advantages. It supports precise control of melting temperature, ensuring consistency and stability throughout the gold melting process. In addition, the induction melting furnace comes with energy-saving features: its high-efficiency energy conversion and low-energy-consumption design make it an ideal choice for the metallurgical industry. With a high degree of automation and user-friendly operation, the equipment can realize fully automatic unattended operation, further improving production efficiency.

The rapid gold induction melting furnace is also widely used in jewelry manufacturing, refining, recycling and other fields. Its vacuum or controlled-atmosphere melting environment effectively reduces contamination from impurities and gases, improving the quality of gold. In addition, the compact design and flexible process parameters of the equipment make it adaptable to operations of different scales.