Heap leaching is a common method for gold extraction from ores, and the properties of the raw ore, including its mineralogical characteristics, associated minerals, and particle size distribution, significantly impact the efficiency of the heap leaching process.
1. Mineralogical Characteristics
The raw material used in heap leaching consists of large ore blocks stacked on a pad. The leaching solution penetrates the ore surface, pores, and cleavage planes to contact and dissolve the gold. Therefore, ores with high porosity and well-developed cleavage facilitate the leaching process. Dense primary ores, however, are difficult to treat with heap leaching. In contrast, oxidized ores, which have undergone weathering, tend to become porous and permeable, making them more suitable for heap leaching.
Finer gold particles exhibit faster leaching rates, but these must be exposed for effective leaching. Coarser gold particles require longer leaching times, and their recovery rates are typically lower, making them less ideal for heap leaching. The shape of the gold particles also plays a crucial role; thin, exposed flakes leach more rapidly, whereas coarse, rounded particles leach more slowly. Gold particles with open pores on their surface leach more efficiently.
2. Associated Minerals
The various mineral components within the ore influence the leaching process to different extents. Minerals that react with cyanide and oxygen in the leaching solution, or those that adsorb on the surface of gold particles, can hinder gold leaching by consuming cyanide and oxygen or purifying the gold surface.
Iron sulfide minerals, such as pyrite, marcasite, and pyrrhotite, can react chemically with cyanide and oxygen in the leaching solution, consuming these reagents. Intermediate products from these reactions also deplete the available oxygen and cyanide.
Arsenic-bearing minerals like arsenopyrite, realgar, orpiment, and arsenic trioxide can similarly react with oxygen and cyanide, reducing the effective chemical components in the leaching solution.
Copper and zinc minerals also react with cyanide, leading to its consumption. Antimony minerals may form deposits on gold particles, obstructing the leaching process. Excessive calcium oxide, used as a protective alkali, can form calcium peroxide on gold surfaces at high pH levels, further inhibiting leaching.
Ores containing carbonaceous minerals can adsorb the dissolved gold, leading to losses in the heap and reducing the overall gold recovery.
3. Ore Particle Size
From a kinetic perspective, smaller particle sizes increase the exposed surface area of gold particles, enhancing contact between the solid and liquid phases and accelerating the leaching process.
However, overly fine particles can slow down the percolation rate of the leaching solution, negatively affecting the solid-liquid separation within the heap. In extreme cases, fine particles can block the uniform flow of the leaching solution, creating dead zones that impair leaching efficiency. Fine particles can also complicate the washing process, leading to the loss of gold-bearing solutions and extending the leaching time.
Y&X's widely recognized product, YX500 gold leaching reagent, serves as an eco-friendly alternative to the highly toxic sodium cyanide, effectively overcoming nearly all of its disadvantages. YX500 is already in industrial production and application. The innovative "combined leaching" and "on-site cleaning" technologies developed by Y&X ensure that tailing pond sludge is discharged according to environmental standards while maintaining high gold recovery rates.
Key advantages of YX500 include:
1. Low toxicity and environmental friendliness, offering enhanced safety in transportation, use, and storage.
2. As a standard chemical product, YX500 can be shipped via sea, rail, or road, greatly reducing transportation costs.
3. It can directly replace sodium cyanide without requiring any modifications to existing leaching processes.
4. YX500 enables faster leaching than sodium cyanide, cutting production cycles by 30%, which saves labor, reduces costs, and conserves water.
5. It provides excellent stability and improved carbon adsorption capacity, significantly boosting the performance of activated carbon and increasing gold recovery rates.
