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Gold recovery chemicals is the reagent that used to extract gold, which is one of necessary element in gold processing plant. The commonly used gold recovery chemicals can be mainly divided into three types: flotation chemicals, heap leaching chemicals and cyanidation leaching (CIL, CIP) chemicals.
Gold recovery industry has important economic significance, but the content of gold in most ore is extremely low. In order to extract gold, it is necessary to crush and grind the ore to suitable size and then separate the gold from the ore using specific mineral processing method and gold recovery chemicals. At present, gravity separation, flotation separation, heap leaching and cyanidation (CIL,CIP) are four commonly used gold recovery methods. Relatively speaking, the gravity separation method is the simplest process. According to the different mineral density and particle size, the ore separation can be achieved by the action of fluid dynamics and various mechanical forces. While flotation separation, heap leaching and cyanidation processes for extracting gold is relatively complicated, as gold recovery chemicals are essential in these three processes. So what are commonly used gold recovery chemicals in these processes?
The mineral flotation process is to strengthen the hydrophobicity of useful minerals and the hydrophilicity of gangue minerals through a certain flotation chemical system. Under the action of mechanical agitation, the useful minerals are floated up to become concentrate, and the gangue minerals sink and become tailings. Through this flotation process, the concentrate and tailings can be well separated. The main gold recovery chemicals to be added during the gold flotation process are: flotation collectors, flotation foaming agents and flotation conditioners.
How to select the proper type of flotation collectors for gold recovery varies from the nature of the ore. In the flotation process of sulfide ore, xanthate, xanthate derivatives, aerofloat, benzoxazole thiol are commonly used collectors for gold recovery. In the flotation of oxided ore, fatty acids and its sodium soaps, alkyl sulfonates, alkyl sulfates, phosphates and arsenates are commonly used collectors. In addition, kerosene and diesel are generally used as oil flotation collectors for gold recovery chemicals.
In the gold flotation recovery process, foaming chemicals must be added to the slurry. Commonly gold recovery foaming chemicals used are eucalyptus oil, camphor oil, cresylic acid, higher alcohols and No. 2 flotation oil (2# oil).
The flotation conditioners can be classified into pH adjusting agent, activator, inhibitor, flocculating agent and dispersing agent depending on the function. The gold recovery chemicals like lime, sodium carbonate, sodium hydroxide and sulfuric acid are used for adjusting slurry pH; sodium sulfide is used for activation; water glass and phosphate are used for dispersion; flocculation and starch are used for flocculation.
The heap leaching method is mainly suitable for low grade gold ore recovery, with the average grade of gold ore is 0.8-1.5g/t. Heap leaching gold recovery process is to firstly crush the ore to a certain particle size (-15mm) and then convey it to the storage hopper, adding gold ore, lime and binder according to the specified amount, mixing them thoroughly and sending the gold ore to the disc granulator. After granulation, the gold ore is piled on the non-leakage ground (dip pad). Start pre-soaking with lime solution until the pH of the heap effluent reaches 9 to 11 and then spray with NaCN solution or environmentally friendly gold recovery chemicals with a concentration of 0.2 to 1.0 g/L.
When the solution slowly passes through the heap (diafiltration) from top to bottom, the gold will dissolve. At this time, the gold-containing solution (pregnant solution) flowing out from the bottom surface is sent to precipitate the precious metal, and cyanide solution after gold removal or non-toxic immersion gold solution (lean solution) is returned to the spray heap for recycling. In summary, the heap leaching gold recovery chemicals are mainly sodium cyanide, potassium cyanide, environmentally friendly gold leaching reagent, lime solution and binder.
The cyanidation method uses an aqueous solution of an alkali metal cyanide as a solvent to leach gold, and then extracts gold from pregnant solution by using a zinc powder replacement device, carbon in pulp, or carbon in leaching method. Cyanide is an essential gold recovery chemical for cyanidation. Commonly used cyanide agents are NaCN, KCN, NH4CN, and Ca(CN)2. Taking into account the relative solubility of cyanide to gold, stability, the impact of impurities on the process, the price and reliability of supply, NaCN is the most commonly used cyanide in the industry.
However, since cyanide is a highly toxic gold recovery chemical, it has caused serious pollution to the environment during the gold recovery process, so cyanide has been banned in many countries. At present, non-toxic gold recovery chemicals become more and more popular, which is a new eco-friendly gold recovery chemical that can completely replace cyanide, and has gradually become a new choice for many gold recovery plants. There are many manufacturers specializing in the production of environmentally-friendly gold recovery chemicals. CNFREE environmental-friendly gold dressing agents are one of them. In fact, the usage of eco-friendly gold dressing agents is similar to the usage of cyanide for recovering gold. CNFREE eco-friendly gold recovery chemical is characterized by a reduction in environmental pollution while ensuring leaching effect and leaching rate, and is therefore favored by many gold ore recovery plants.
In summary, in gold flotation process, the commonly used gold recovery chemicals are collectors (kerosene, diesel, fatty acids and their sodium soaps, alkyl sulfonates, alkyl sulfates, phosphates, arsenates), foaming agents (eucalyptus oil, camphor oil, cresol acid, higher alcohols and No. 2 flotation oil), and conditioning agents (lime, water glass, sulfuric acid); in gold heap leaching process, the commonly used gold recovery chemicals are sodium cyanide, potassium cyanide, environmentally friendly gold leaching agent and lime; in gold cyanidation leaching process like CIL, CIP process, the commonly used gold recovery chemicals are sodium cyanide and eco-friendly gold dressing agent. Of course, to choose which kind of gold recovery chemical for the gold dressing plant is still based on the properties of the gold ore itself, the project condition and government policies.
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