1.Preparation before using gold leaching reagent
(1) Ore fineness and slurry quality fraction.
After crushing and grinding the ore slurry, first of all, to ensure that the ore fineness and slurry quality fraction required for cyanide leaching or other gold leaching reagent, which depends on the nature of the ore and process, such as the whole mud cyanide, ore fineness is usually in the -200 mesh 85% ~ 95%, and flotation concentrate cyanide often need to be re-grinding, usually up to 325 mesh or 350 mesh or even finer. Of course, the most suitable grinding fineness is determined by test.
Cyanideor other gold leaching chemicals leaching slurry quality fraction generally fluctuates within 25% to 33%, concentrate leaching quality fraction is low, the whole mud cyanide quality fraction is high, if cyanide with carbon adsorption (or ion exchange resin adsorption) method of gold extraction, in order to ensure that the adsorbent in the slurry suspension, the slurry must be kept at 40% to 50% quality fraction.
(2) Slurry debris removal.
From the quarry to the ore is often with a large number of wood chips, gravel, fuse, plastic bags, rubber tyre fragments and other debris, these substances suspended in the slurry is easy to cause the slurry flow through the equipment and pipeline clogging, affecting the smooth progress of cyanidation.
Some substances, such as wood chips will also adsorb dissolved gold, resulting in the loss of gold, especially in the carbon pulp process, wood chips with the gold-carrying charcoal into the desorption operation, in the high alkalinity, high temperature solution, the wood chips are easy to be corroded, slurry so that the viscosity of the solution increases, the wood chips will also be adhered to the surface of the charcoal particles, affecting the desorption of an electrolytic process of the technical indexes and the process of the flow of the smooth.
In addition, wood chips in and demineralised charcoal into the regeneration kiln activation process, will be further converted into charcoal, its nature of brittle, after returning to the leaching broken into fine charcoal and adsorption of gold lost in the tailings. Therefore, before cyanide leaching slurry slag separation, chip removal is very important.
At present, the equipment used for chip removal are fixed screen, cylindrical screen and linear vibrating screen. Horizontal cylindrical screen has higher screening efficiency and less screen wear than plane fixed screen; while linear vibrating screen has higher efficiency because it works under vibration condition, these two kinds of screens are widely used in carbon slurry plant.
In addition, in order to strengthen the debris removal process, in the charcoal slurry plant is often set up multi-stage debris removal, such as first in the overflow of the classifier, with a coarser mesh (2 ~ 3mm) to screen off a large number of coarse particles of wood chips and sundries.
And then in the hydrocyclone before the feed with a plane sieve or a cylindrical sieve (sieve mesh is generally taken to be 24 mesh), and finally in the concentration of the former use of a finer (eg, 28 ~ 35 mesh) cylindrical sieve or linear vibrating screen, will be the remaining fine wood chips and other Sieve out the sundries, some even set up another section of chip removal screen before cyanidation or beneficiation process, so as to reduce the wood chips in the slurry to the lowest amount.
(3) De-drugging of flotation concentrate
As the flotation chemicals, especially the yellow drug and No.2 oil are very unfavorable to the cyanide or other gold leaching chemicals leaching process and the carbon adsorption gold extraction process, it is necessary to carry out de-drugging before the cyanide leaching of flotation concentrate. In order to improve the effect of de-drugging, the multi-stage de-drugging treatment method of de-drugging, re-grinding and re-drugging can be used.
Slurry in cyanideor other gold leaching chemicals before the fineness, quality score, debris removal, de-drugging and a series of preparations, these operations can be carried out sequentially, can also cross each other for many times.
(4) Adjust the pH value of the slurry and slurry pretreatment
Usually cyanide or other gold leaching chemicals is carried out in the pH value of 10 ~ 11, the production of lime as an adjusting agent. Add lime to the slurry, lime can be added directly to the ball mill (dry addition), can also be adjusted to lime into milk of lime, and then through the pipeline to the mill or adjust the slurry tank (wet addition). The latter is more convenient and hygienic than the former.
When the leached material contains some minerals that hinder the gold leaching process, such as magnetic pyrite, albite and a small amount of carbonaceous minerals, it is necessary to carry out aerated alkaline leaching or oxidative leaching before cyanide leaching of gold, in order to eliminate the adverse effects of these minerals on cyanide leaching of gold.
2.Gold leaching chemicals–Environmentally friendly gold leaching agent
In recent years, with the continuous increase in the demand for gold mineral resources, mine environmental protection and its governance work has become urgent. Many countries, because of its great harm to mine workers and the environment, began to restrict the use of cyanide.
Therefore, the environmental protection leaching agent, a new type of environmental protection material used to replace the traditional cyanide leaching process has arisen. It is of great significance in the field of gold extraction. Below is some key information about Eco Leach:
- The development of environmentally friendly gold extraction technology: as a low-toxicity, recyclable gold leaching agent, the environmentally friendly leaching agent is gradually replacing the traditional sodium cyanide, solving the problem of environmental pollution and safety worries.
- Characteristics of environmentally friendly leaching agent: environmentally friendly leaching agent is usually formulated from thiourea, thiosulfate and ferrocyanide with the addition of urea and caustic soda chemical reagents to formulate environmentally friendly gold extraction agent. Compared with the traditional cyanide, the toxicity of these agents is lower, safer to use.
- Application of environmentally friendly leaching agent: environmentally friendly leaching agent is suitable for a variety of gold-bearing ores in the leaching of gold production process to use, changing the history of the past single use of sodium cyanide as a gold extraction agent. These products have entered the growth period in the market, gradually affirmed by customers, and have a broad market prospect.
- Toxicity test of environmentally friendly leaching agent: According to the toxicity test report of different environmentally friendly gold extracting agents, their acute toxicity LD50 value is much higher than that of sodium cyanide, showing lower toxicity.
- Principle of gold leaching of environmentally friendly leaching agent: environmentally friendly gold leaching agent is a mixture of ferric cyanide, urea or thiosulphate and alkali and other compounds, and its principle of gold leaching is mainly through the formation of stable complexes with gold to achieve the dissolution of gold.
- Policy support: It is mentioned in the Technical Policy on Prevention and Control of Gold Industry Pollution issued by the Ministry of Ecology and Environment of China that it encourages the use of cyanide-free or low-cyanide leaching chemicals to extract gold, and the pre-treatment of difficult-to-treat gold ores and gold concentrates gives priority to the use of biological oxidation, pressure oxidation and other wet pre-treatment technologies.
To sum up, as a new and environmentally friendly material for gold extraction, environmentally friendly leaching agent is being accepted and applied by more and more mining enterprises and scientific research institutes to realise the greening and environmental protection of the gold extraction process.
3. Y&X low-toxicity environmental gold leaching reagent
Here we briefly introduce an environmentally friendly leaching reagent YX500 launched by Y&X, which has successfully replaced sodium cyanide and is widely used in gold processing and metallurgical production, with full independent intellectual property rights.
YX500 has achieved industrial production and application, the development of the ‘synergistic leaching’ and ‘in situ treatment’ technology to ensure that under the premise of the leaching index to achieve the tailings slurry discharge standards.
The research results have been appraised by China Gold Association, which are innovative, with broad market prospect, and the overall technology has reached the international advanced level, among which the ‘synergistic leaching – in-situ treatment’ technology has reached the international leading level. The product can directly replace sodium cyanide, without any changes to the original cyanide process, YX500 agent has low toxicity and environmental protection, high recovery rate, good stability, easy to operate, fast recovery, low dosage, low cost, easy storage and transport and so on.
For more information, please feel free to contact Y&X team.