Oxidized gold ore is one of the most widely distributed and abundant gold ores in the world. It has been exposed to nature for a long time, with complex mineral composition and low grade, making extraction more difficult. Are you also facing low gold recovery rate and environmental protection failure leading to loss?
As the person in charge of a mineral processing plant, the gold ore characteristics and extraction methods will greatly affect your final revenue. In this article, we will analyze the characteristics of oxidized gold ore, and sort out a variety of technical paths from pretreatment to core extraction, to help you recover every gram of gold.
Ⅰ.What is Oxidized Gold Ore
Primary sulfide gold ore after long-term natural weathering and oxidation formation of secondary gold ore, that is, oxidized gold ore. Oxidized gold ore is usually yellow to brown, loose texture. This kind of ore contains a large amount of iron oxide, iron hydroxide, quartz, clay and other impurities in addition to the gold element. The gold is usually embedded in hematite or limonite.
It is these different physical and chemical properties that affect your choice of extraction process and the gold recovery rate.
Ⅱ.Oxidized Gold Ore Extraction Difficulties
Oxidized gold ore resources, although rich, but also let a lot of processors trouble. The following difficulties directly affect the gold recovery rate and production costs.
Mineral composition: oxide gold ore contains a large number of clay, iron oxide, quartz and organic carbon and other impurities. These impurities will have a chemical reaction with the extraction reagent, such as gold in solution will be organic carbon adsorbed first, resulting in a significant decrease in your recovery rate.
Lower gold grade: Oxidized gold ore has a lower gold content, requiring you to process a large amount of ore to obtain a certain amount of gold.
Environmental issues: The wastewater rejects generated during the extraction of gold ore have a significant impact on the environment. The main considerations are cyanide management, tailings management, and regulatory requirements.
These wastes (cyanide-containing wastewater, heavy metals, etc.) need to be processed by you and meet the environmental requirements before they can be discharged.
Ⅲ.Pretreatment of Oxidized Gold Ore
Many people extract it directly, and ultimately find that the recovery rate is low and the benefits are poor. However, pretreatment of oxidized gold ore is the basic step of gold extraction. After pretreatment, the ore has fewer impurities, and the gold element is separated from the vein, which is convenient for subsequent extraction.
1.Ore Characterization Analysis
Chemical Analysis: Comprehensive testing is performed to understand the composition of the ore. Determine the presence of gold, sulfur, iron oxides and other minerals.
Mineralogical studies: Determine the distribution of gold in the ore – whether it is readily selectable or trapped in the sulfides.
2.Crushing
Before crushing the ore, you can use a trommel screen to remove clay and avoid equipment sticking. Then use a jaw crusher and a cone crusher to break the ore into small pieces, initially breaking up the layer of impurities encapsulating the gold particles.
3.Grinding
Depending on the composition of the ore and the extraction method, the ore is ground to finer (200-325 mesh) using ball mill grinding. The grinding process fully exposes the gold-encapsulated vein minerals for the next step of extraction. Ultrafine grinding can also improve the recovery of difficult oxide ores.
Ⅳ.Oxidized Gold Ore Extraction Methods
There are many kinds of oxidized gold ore extraction methods, and each method is adapted to different situations. We suggest combining your actual needs (cost, environmental requirements, etc.) to choose. The following four mainstream extraction methods for oxidized gold ore:
1.Non-Cyanide Extraction Methods
Applicable scenarios: oxidized gold ore grade in 0.5-2g/t and low impurity content, more suitable for small and medium-sized mines.
Advantage: suitable for low-grade ore extraction program; low environmental protection processing costs, low equipment investment.
(1) Gravity Separation
Physical separation is achieved by utilizing the high density characteristics of gold. This method utilizes centrifuges, shaking beds or spiral chutes to efficiently recover free gold with coarse particle size. The whole process does not use chemicals and is environmentally friendly.
(2) Flotation separation
The principle of flotation method is to utilize the difference of surface properties of minerals to enrich valuable minerals. In this process, a trapping agent is added to enhance the hydrophobicity of the gold particles, allowing it to attach to the air bubbles and rise to the surface for recovery. Flotation is particularly effective for fine gold particles.
(3) Heap Leaching
Heap leaching is primarily used to process large scale, low grade oxide gold ores. This process stacks the ore into piles and sprays the leach solution to dissolve the gold. The precious liquid is then collected, from which the gold is recovered by adsorption or replacement.
(4) Magnetic Separation
Gold itself is not magnetic, but some oxidized gold ores contain associated magnetic minerals (such as magnetite, hematite, etc.). Magnetic separation can be used to separate these minerals, to facilitate the subsequent processing of non-magnetic gold particles.
2.Oxidized Gold Ore Cyanidation Extraction Method
Scenario: It is suitable for mines with a gold grade of 1-3g/t and high impurity content, and large-scale enterprises can also choose this method.
Mix and stir the ore ground into fine powder with cyanide solution to dissolve the gold to form gold-cyanide complex. At this point you get the leach solution. Activated carbon is then used to adsorb the gold, zinc powder to displace the gold, or electrolytic deposition of gold.
Cyanidation is one of the most commonly used methods for extracting gold from oxidized gold ores. The technology of this method is mature and the recovery is stable at 70%-90%. The cost of cyanide reagent is low and suitable for large-scale production. But be careful, you need to equip professional equipment to deal with cyanide-containing wastewater and waste residue to ensure environmental protection and safety.
3.Oxidized Gold Ore Sulfide Extraction Method
Applicable scenes: difficult to treat oxidized gold ore; partially oxidized ore with insufficient degree of oxidation; oxidized gold ore with low recovery rate.
Adding sulfiding agent to the oxidized gold ore transforms the gold element in the ore into gold sulfide, and then extracts the gold through flotation and cyanidation.
This method can effectively improve the recovery rate of difficult to process gold ore, and it can also reduce your production cost when used with other methods. However, you need to pay attention to controlling the amount of sulfiding agent so as not to contaminate the reagent.
4.Oxidizing and Roasting Extraction Method
Applicable scenes: oxidized gold ores with extremely high impurity content; gold-bearing ores that cannot be extracted by conventional methods.
The oxidized gold ore powder is roasted at high temperature to remove the impurities in the ore through high temperature. At the same time, the gold element is converted into soluble compounds. The recovery rate of this method can reach 75%-90%. However, harmful gases such as sulfur dioxide will be produced during the extraction process, and the equipment investment and environmental protection costs are high.
Ore extraction test is an indispensable step before your decision, which can avoid great risks in the future for you with minimal cost.
Ⅴ.Key Equipment for Oxidized Gold Ore Extraction
It is also very important for you to choose the right equipment, and the right processing equipment can greatly improve the extraction efficiency of gold ore. We recommend the following mineral processing equipment for you:
1.Overflow ball mill: this kind of ball mill can grind the ore to the fineness you want and fully expose the gold particles. At the same time, it will not over-grind and cause the loss of valuable minerals. The structure of the equipment is also simple, easy to operate and low energy consumption.
2.Flotation machine: this equipment can adjust the amount of gas and stirring intensity, so as to accurately separate the gold and impurities, and help you easily recover the fine-grained gold. At the same time, the use of environmentally friendly capture agent, to reduce the pressure of your subsequent processing.
3.Magnetic separator: It is used to remove magnetic iron minerals (such as magnetite, limonite, etc.) in the ore at the pretreatment stage to reduce their interference in the subsequent cyanidation process and enhance the leaching efficiency.
4.Gravity separator: utilizing density difference to separate gold, no additional reagents, easy operation and low cost.
Summary
There is no standard practice for the extraction of oxide gold ore, only the method that suits your mineral properties and mine conditions. We hope this article has helped you understand the characteristics of oxide gold ores and adopt the appropriate extraction methods and equipment to maximize gold recovery while minimizing environmental impact. Contact Sandreck for more information.
FAQs
Q:The recovery of oxidized gold ore by cyanidation is less than 60%, what could be the reason?
A:The most common reason is that the gold is encapsulated by iron oxide or clay, which makes it difficult for the leachant to contact the gold particles. It is recommended that you first do a detailed mineral analysis to confirm the nature of the inclusions . Then break the inclusions by ultra-fine grinding (-400 mesh or more) or roasting pretreatment, the recovery rate can be increased to more than 85%.
Q:How should I treat tailings with high gold content after gravity separation?
A:This usually indicates the presence of fines or inclusions of gold. It is recommended that you increase the grinding fineness (to below -200 mesh) or use flotation to recover fine-grained gold. You may also consider entering gravity tailings into a cyanide leaching system for integrated recovery.
Q:Can magnetic separator really improve the recovery of oxidized gold ore?
A:For oxidized ores containing magnetic minerals such as magnetite and hematite, magnetic separation pretreatment can significantly improve the leaching effect. By removing magnetic minerals, cyanide consumption can be reduced, slime interference can be minimized, and your overall recovery rate can be increased by 3-8 percentage points.
Q:How to control the cost of ultra-fine grinding with high power consumption?
A:It is recommended to adopt the principle of “more crushing and less grinding”, and reduce the grinding size as much as possible in the front-end crushing stage. Choose frequency conversion energy saving ball mill, your power consumption can be reduced by 15-25%. At the same time, it is also important to optimize the proportion of steel balls.
