Cyanidation process is widely used to extract gold because of some merits like high gold extraction efficiency and guaranteed gold recovery rate. However, this process does result in gold tailings containing cyanide. Cyanide-containing gold tailings cannot be discharged at will, because cyanide is toxic and has a great impact on environmental pollution. How to solve this problem? Today, I will introduce the method of removing cyanide from gold tailings, and introduce the new process of removing cyanide from gold tailings in the form of project cases.
For the tailings after using the gold all-slime cyanidation-carbon slurry method, many mines use the traditional alkaline chlorination method to treat the cyanide and discharge the tailings to the tailings pond for storage, and some mines filter the tailings and then adopt tailings dry stacking. Alkaline chlorination refers to the destruction of cyanide in gold tailings by chlorine-based oxidants such as bleaching powder, sodium hypochlorite, and liquid chlorine. The tailings dry stacking refers to the process of using a series of concentration and dewatering equipment such as thickeners and filter presses for the gold tailings to separate the wet tailings from solid, and then stockpiling the dry the tailings solids, with the tailings liquid returning to the beneficiation process.
The operation method of the incineration method is to mix the cyanide waste residue, coal and clay (including quicklime) in a certain proportion to make a ball, and then put it into an incinerator for incineration, thereby removing the cyanide method. The organic oxides can be decomposed by the incineration method to achieve the purpose of volume reduction, detoxification, energy recovery and by-products. Studies have shown that after incineration, the removal rate of cyanide in the cyanide waste residue is more than 90%, and the waste residue can be used for brick making.
Biological method refers to the use of some fungi and bacteria to degrade cyanide in cyanide residues. The biological method has the advantages of no cyanide accumulation and no secondary pollution. It can effectively remove cyanide, and the operation is simple. While there are problems such as low treatment concentration and low load.
Natural degradation method refers to the process of degrading cyanide in gold tailings into non-toxic substances by means of natural physical and chemical effects such as natural oxidation, volatilization, and sunlight exposure. This gold tailings processing method has the advantages of small investment and low production cost, but has disadvantages such as large floor space, slow process, easy limitation by natural factors, and difficulty to meet standards of discharging waste.
The above four methods for removing cyanide are relatively traditional methods, with pros and cons respectively. Xinhai recently undertook a cyanide removal project from gold tailings in Inner Mongolia. Let's take a look at the new ideas for cyanide removal.
Properties of gold tailings: the tailings of the Mongolia 120tpd gold cyanidation project are the tailings discharged from pressure filtration machines after on-site cyanidation leaching. The tailings contain about 20% water and 400ppm cyanide. Xinhai customized the cyanide removal process according to the conditions of the processing plant.
New technological process for removing cyanide from gold tailings:
1. The tailings of the disc filter are transported by the belt conveyor to the high-efficiency agitation tank for pulping, and the bleaching powder and circulating water are added to the agitation tank to fully stir and react;
2. The mixing ore slurry flows into the double impeller agitation tank for self-flow, and the cyanide removal process continues. The ore pulp that reaches the standard is pumped into the box filter press for dehydration by the slurry pump. The filtered filtrate is buffered in the buffer tank, and is pumped back to the first high-efficiency agitation tank by the slurry pump for slurry mixing.
This new cyanide removal process requires less investment and equipment. You only need a filter, a conveyor, an agitation tank, and a filter press to complete the entire cyanide removal process. The whole process will not cause air pollution and water environment pollution. And the tailings treated by this process can also be used for mine filling, production of building materials, etc., with significant advantages.
