Detailed Analysis of 6 Common Gold Ore Beneficiation Methods

Different gold extraction processes are used for different types of gold ore. Gold extraction processes include gravity separation, flotation, heap leaching, cyanidation, and non-cyanide methods (i.e., non-toxic gold extraction processes). Domestic gold mining and metallurgical processes include single gravity separation, single flotation, gravity separation-flotation, amalgamation-flotation, whole-ore cyanidation-zinc powder displacement, whole-ore cyanidation carbon pulp, whole-ore cyanidation resin gold extraction process, flotation + gold concentrate cyanidation, heap leaching process, etc.  Combined process flows can be used as needed, such as gravity separation-flotation, flotation-cyanidation (concentrate or tailings cyanidation), cyanidation-flotation, and gravity separation (flotation)-carbon leaching processes, all of which are applied in gold mines.

1. Amalgamation Method

This method has unique advantages in recovering liberated native gold (especially coarse-grained gold). It is based on the selective wetting of gold particles in the pulp by liquid metal, separating them from other metal minerals and gangue, and recovering the gold in the form of amalgam, which is then separated by distillation.

Its advantages are that the gold extraction process is simple and low-cost, and it can reduce gold losses in the tailings. The disadvantage is that mercury is highly toxic, causing serious environmental pollution and being extremely detrimental to human health. However, there is currently no way to solve this problem. With increasingly stringent environmental protection regulations, this method is being used less and less.

2. Chlorination Method

The chlorination method has a fast leaching rate and can deactivate carbonaceous substances containing gold. However, if reducing substances (sulfides) are present in the raw material, it leads to excessive chlorine consumption. In addition, acidic chlorine-containing solutions are highly corrosive, so they require high-quality equipment.

3. Flotation Method

This method is mainly used to treat finely disseminated vein gold ore. Gold is often floated into copper and lead concentrates, and then gold is extracted from these concentrates. Therefore, it is a relatively economical and reasonable process for ores containing non-ferrous metals, allowing for comprehensive utilization of multiple metals. The disadvantages are low recovery rate for oxidized ores and difficulty in collecting coarse-grained gold. The main equipment for gold ore flotation is the flotation machine, which is used in conjunction with other equipment such as ball mills, dryers, and spiral classifiers. Each piece of equipment has an irreplaceable and important function, responsible for the beneficiation, grinding, drying, and classification of the gold ore, respectively.

4. Cyanidation Method

Its process flow has been gradually improved. It involves crushing and grinding the gold-bearing ore, followed by cyanide leaching. After sufficient leaching, activated carbon is added to adsorb the gold. The gold-loaded carbon is then washed and desorbed, separating into a gold-rich solution and desorbed carbon. The gold-rich solution undergoes electrolysis to produce gold powder, which is then smelted into gold ingots. The desorbed carbon is regenerated and mixed with new carbon in a certain proportion for repeated use in the process.

The cyanidation method is the main method for gold ore beneficiation domestically and internationally, but it has a long processing time, and cyanide is a highly toxic substance.  With the increasing demand for environmental protection, the treatment of cyanide in tailings poses a significant cost burden for enterprises. Therefore, this method is not recommended.

5. Thiourea Method

The gold-rich solution obtained from thiourea gold dissolution can be used for gold precipitation by iron or aluminum displacement or electrodeposition, depending on the gold content. The gold mud is then smelted to obtain refined gold. The gold mud smelting process is the same as that for cyanide gold mud.

The thiourea gold extraction process is a non-toxic gold extraction process. my country has already adopted this method to treat gravity separation and flotation gold concentrates. However, this process still has the problems of high cost and unstable operation.

6. Resin Method for Gold Extraction

The resin method is suitable for treating clay-type gold ores with high clay content, and gold ores containing natural adsorbents such as graphite, asphalt, shale, and iron oxides, which are difficult to treat with the traditional cyanide-zinc displacement method. It is also suitable for treating roasted gold-bearing pyrite and low-concentration gold-containing solutions from heap leaching.

The resin pulp method is better than the carbon pulp method and has lower production costs. The ion exchange method is more effective for ores containing gold-adsorbing substances (such as clay minerals). However, the disadvantages are that the resin has poorer selectivity than activated carbon, a finer particle size, lower density, and poorer abrasion resistance. It is also easily adsorbed onto the surface of the pulp. Therefore, the carbon-in-pulp method is more suitable for treating slurries containing a high concentration of other metal cyanide complex ions.