This process falls under the technical field of metallurgy, and is implemented in accordance with the following steps:

① Raw gold ore is first processed by open-circuit coarse crushing. All coarsely crushed products are fed into the intermediate crushing system and then classified by a vibrating screen. Coarse oversize materials are returned to the intermediate crushing equipment for further crushing, while qualified undersize materials meeting the particle size requirement are fed into the HPGR mill.

② After open-circuit fine crushing by the HPGR, the crushed products are treated through the combined action of a wet vibrating screen and classification equipment. The finer overflow products are delivered to the all-slime cyanidation leaching system, while the underflow sand and coarse-grained materials are mixed with an appropriate amount of pH-adjusting lime, then transported to the leaching yard for heap construction, so as to realize the classified leaching process for gold ore materials.

③ After the leaching process is completed, gold-bearing pregnant solution and tailings are obtained.

This process adopts HPGR open-circuit fine crushing. The crushed products feature finer particle size and abundant surface microcracks, which can significantly improve the gold leaching rate, reduce the consumption of leaching reagents, and shorten the heap leaching cycle. Meanwhile, the classified fine-grained products can be recovered synchronously during the heap leaching process.

Current pretreatment methods for precious metal-bearing waste blue film sheets include the roasting method and wet stripping method, with the latter further categorized into inorganic solvent stripping and organic solvent stripping.

The roasting method features a short treatment process, as alloy feedstock can be directly obtained after roasting. However, it comes with high investment costs, as it requires the procurement of incinerators and flue gas treatment facilities (a large volume of hazardous flue gas generated during roasting needs proper treatment), leading to elevated environmental protection costs.

The organic solvent-based wet stripping method has the edge in easy scaling and automated production. Nevertheless, it is plagued by defects including long process flow, high requirements for production equipment, large reagent consumption, severe health hazards to humans caused by highly volatile reagents, and intractable waste liquid disposal.

As for the inorganic solvent-based wet stripping method, it also has shortcomings such as long treatment process, low level of mechanization during operation, and relatively low treatment efficiency.

For easily treatable ores, the Carbon-in-Pulp (CIP) and Carbon-in-Leach (CIL) processes are now widely adopted. As mentioned above, these two new process flows represent important research achievements and progress in the chemical metallurgy industry. According to incomplete statistics, roughly 50% of the world's gold is currently produced via these processes, which fully demonstrates their high production efficiency and wide industrial adoption.

These processes are applicable to a broad range of feed materials, thus providing great flexibility for process selection. Coupled with their impressive metal recovery rates and low investment costs, it comes as no surprise that they rank among the most widely used metallurgical processes worldwide.

Overall, the CIP process has a significant economic advantage over the traditional cyanidation process. Its core differentiating advantage lies in its gold recovery mechanism: the zinc displacement process (a conventional downstream step of traditional cyanidation) recovers gold through reduction, where gold ions are reduced and deposited onto zinc powder. This process requires clear filtrate as a prerequisite, otherwise high-purity gold cannot be extracted at all.

The CIP process, by contrast, extracts gold directly from ore pulp, so the straightforward and convenient solid-liquid separation method can be applied directly. This approach not only simplifies operation, but also considerably cuts equipment and labor costs.

The spent three-way catalysts are first ball-milled into fine powder, then mixed with lead flue dust and lead-silver slag for granulation. The obtained granules are fed into a blast furnace for smelting and enrichment, and the produced crude lead (lead bullion) is sent for cupellation, which yields a silver-palladium-platinum-rhodium alloy.

The alloy is leached with nitric acid to separate silver and palladium, which are then isolated from the nitric acid leachate via precipitation. The remaining undissolved residue is leached with aqua regia to separate platinum, which is subsequently extracted from the aqua regia leachate, while the aqua regia-insoluble residue is rhodium powder.

However, due to the relatively high content of platinum group metals (PGMs) in the spent three-way catalysts, the enrichment of PGMs via lead-silver capture is far from satisfactory, requiring two stages of enrichment and resulting in excessive PGM loss in the smelting slag. In addition, the enriched crude lead has an excessively high PGM grade, causing considerable PGM loss in lead oxide and cupellation slag during the cupellation process, which necessitates further enrichment and a subsequent secondary cupellation of the reprocessed crude lead.

Overall, this method has the drawbacks of long process flow, lengthy production cycle, heavy polluti

The main components of three-way catalysts are as follows: alumina (Al₂O₃) accounts for over 98%, with a palladium (Pd) content of 3000–10000 g/t, platinum (Pt) content of 150–10000 g/t, and rhodium (Rh) content of 150–600 g/t.

The process proceeds as follows: the three-way catalyst is first ball-milled into powder, fed into a reaction vessel, and leached via the aqueous chlorination method in a hydrochloric acid medium; the obtained leachate is then treated via the sodium nitrite complexation process.

This process has multiple drawbacks: it requires secondary leaching, and an excessive volume of leachate will impair the recovery efficiency of precious metals. The leaching residue suffers from incomplete leaching, making it economically unviable to recover valuable components from the residue. The overall process is lengthy and cumbersome: the sodium nitrite complexation step requires multiple cycles to separate platinum, palladium and rhodium, leading to high labor intensity, high reagent costs, and large volumes of waste gas and wastewater. During the hydrolysis of base metals, precious metals are easily entrained in the hydrolysis products. During the separation of Pt, Pd and Rh, the obtained Pt and Pd fractions are often entrained with Rh, while the Rh product contains residual Pt and Pd. The process is difficult to regulate and poses high operational difficulty.

Although this method can directly recover and separate Pt, Pd and Rh, it suffers from low recovery rates, high costs, and a heavy workload for waste gas and wastewater treatment, which is not conducive to environmental protection.

The sulfuric acid curing pretreatment method for refractory copper oxide ores falls within the technical field of metallurgy (for patent scenarios, it is recommended to replace this phrase with pertains to the technical field of metallurgy to align with standard patent writing conventions). The process is as follows: Refractory copper oxide ore, water and concentrated sulfuric acid are fed into a pelletizer in a prescribed proportion. The reaction between water, concentrated sulfuric acid and the ore liberates copper from gangue or other associated minerals, fulfilling the dual purposes of separating copper from other valuable metals and gangue minerals, as well as loosening the structure of the refractory copper oxide ore to increase its porosity.

This pretreatment method significantly improves the technical and economic indicators of heap leaching, thereby achieving a substantial increase in copper leaching rate, recovery rate and resource utilization efficiency, while reducing production costs.

The main components of three-way catalysts (TWCs) are as follows: aluminum oxide (Al₂O₃) accounts for over 98% of the total mass, with palladium (Pd) content ranging from 3000 to 10000 grams per ton of catalyst, platinum (Pt) at 150–1000 g/t, and rhodium (Rh) at 150–600 g/t.

There are generally two conventional processes for recovering rare and precious metals from spent (deactivated) three-way catalysts in existing industrial technologies:

1、Pyrometallurgical Process: The spent TWCs are first ball-milled into powder, mixed with lead fume dust and lead-silver slag for granulation, then charged into a blast furnace for smelting and enrichment to obtain crude lead. The crude lead then undergoes cupellation, which yields a Ag-Pd-Pt-Rh alloy. Next, silver and palladium are dissolved from the alloy using nitric acid, and the two metals are separated from the leachate via precipitation. The remaining undissolved solid is treated with aqua regia to leach platinum, which is subsequently extracted from the solution, while the solid residue insoluble in aqua regia is rhodium powder.

2、Hydrometallurgical Process: The spent TWCs are ball-milled into powder and fed into a reaction kettle, where leaching is carried out via aqueous chlorination in a hydrochloric acid medium, and the obtained leachate is processed using the sodium nitrite complexation method.

This invention falls within the field of comprehensive utilization of precious metal secondary resources, and specifically relates to a method for recovering precious metals from spent automotive catalysts via a hydrometallurgical dissolution - stripping activation - hydrometallurgical dissolution process, which addresses the technical challenge of precious metal recovery from spent automotive catalysts.

The method is implemented through the following steps:

(1) Ball milling: Spent three-way catalysts (TWCs) are ball-milled to 200 mesh in a ball mill. Sampling and assay show the precious metal contents are 100–300 ppm platinum (Pt), 1500–2500 ppm palladium (Pd), and 100–300 ppm rhodium (Rh);

(2) Aqueous chlorination;

(3) Filtration;

(4) Stripping activation;

(5) Dissolution;

(6) Filtration;

(7) Iron powder reduction;

(8) Refining of platinum, palladium and rhodium.

The method has the following advantages:

It delivers high precious metal recovery rates, with platinum recovery exceeding 97%, palladium recovery exceeding 98.5%, and rhodium recovery exceeding 95%; it boasts a short production cycle and remarkable economic benefits; it is easy to operate, convenient for industrial scale-up, and features a more eco-friendly production process.

Heap Leaching Process for Low-Grade Gold Ore Based on High Pressure Grinding Roll Comminution

This heap leaching process for low-grade gold ore based on high pressure grinding roll (HPGR) comminution falls under the technical field of metallurgy, and is implemented in accordance with the following steps:

① The run-of-mine (ROM) gold ore is first subjected to open-circuit coarse crushing, and all coarse crushed products are fed into the secondary crushing system, followed by classification via a vibrating screen. Coarse oversize materials are returned to the secondary crushing equipment for further comminution, while undersize materials with qualified particle size are delivered into the HPGR.

② The HPGR performs open-circuit fine crushing, and the crushed products are treated through the combined operation of a wet vibrating screen and classification equipment. The finer overflow product is fed into the all-slime cyanidation leaching system, while the underflow (settled sand) and coarse-grained materials are mixed with an appropriate amount of lime for alkali adjustment, then transported to the leach pad for heap construction, realizing the classified leaching process for gold ore materials.

③ Upon completion of leaching, gold-bearing pregnant solution and tailings are obtained.

This process adopts HPGR open-circuit fine crushing, whose crushed products feature finer particle size and abundant surface microcracks. It can significantly improve the gold leaching rate, reduce the consumption of leaching agents, and shorten the heap leaching cycle. While the heap leaching operation is carried out, the fine-grained classified products are also recovered simultaneously.