Gold mineral ore dressing

1 Development of leaching gold mine pretreatment technology

The refractory gold ore refers to a gold ore that has not been effectively leached by conventional cyanidation after the ore has been finely ground. There are many reasons why such ore is difficult to leach. It is generally believed that the mineralogical causes of infiltration are as follows: (1) the ore contains cyanide insoluble gold-containing minerals and compounds; (2) the ore contains pyrite and arsenic. Gold-coated minerals such as pyrite; (3) In the process of roasting or cyanidation, iron, lead , antimony or other oxides or precipitates of arsenic and sulfide form a film on the surface of the gold particles, and the formation of the film prevents the dissolution of gold. Wait. These reasons have caused refractory gold mines to undergo special treatment in order to obtain higher recovery rates. In order to effectively recover gold from refractory gold mines, a large number of pretreatment studies have been carried out at home and abroad.

For arsenic-containing and bismuth-containing refractory gold deposits, the researchers found that prior to leaching, pretreatment methods such as alkaline pretreatment, addition of anti-filming agent and catalyst for such ore can significantly improve the leaching index. Oktay Celep et al. found that the direct cyanidation leaching only obtained the extraction rate of gold 49% and silver 18% at a temperature of 80 ° C, sodium hydroxide concentration of 5 mol / L, ore particle size of 5 μm. Alkaline pretreatment of ore under conditions, the leaching rate of silver increased from 18% to 90%, and the leaching rate of gold increased by 20%.

~30%. In the study of an arsenic-sulfur-lead gold deposit in Tianshui, Gansu, Wang Ting et al. found that the addition of a film-preventing agent and an activator can increase the gold leaching rate before the cyanidation leaching of the arsenic-sulfur-lead gold deposit. Li Xueqiang et al. proposed a new process of “catalytic oxidation of acid immersion wet ruled gold” for a arsenic-containing refractory gold-silver concentrate. HNO3 was used as a catalyst, SAA was used as an activator, and oxygen was used as an oxidant. Cyanide was prepared by pre-treatment of temperature and pressure. With gold extraction, the recovery rate can be increased from 13% to 56% to 92% to 95%. Jin Shibin et al. used roasting gold ore and concentrate under different conditions for roasting-calcination cyanidation gold leaching. It was found that antimony trioxide does not adversely affect cyanide leaching gold, but it will cyanide after calcination. The immersion gold has an adverse effect. Tianshu Guo et al top when alkali leaching arsenic removal process, the addition of hydrogen peroxide and potassium permanganate and sodium auxiliary aids alkali leaching arsenic removal, achieved good results in a high arsenic Refractory gold. Xue Guang et al. found that the content of arsenic in gold concentrate is usually controlled below 0.1%. With the increase of arsenic content, the cyanide leaching rate of gold and silver gradually decreases. For gold concentrates with an arsenic mass fraction of 0.45%, the addition of 4% to 5% sodium sulfate in the case of calcination can make the cyanidation leaching rates of gold and silver reach 95% and 60%, respectively.

In the treatment of other types of difficult gold mines, roasting, alkali ammonia pretreatment, etc. before leaching can significantly increase the leaching rate of gold. Zhang Jinxiang et al. used the column immersion method of “alkaline ammonia pretreatment + cyanide leaching” to treat a refractory gold mine in Hami, Xinjiang, and the gold leaching rate can reach 80.91%. The recovery rate of conventional cyanide gold in a refractory gold ore flotation concentrate in Xinjiang is only 40.82%. Zhang Lizheng and others have undergone two-stage roasting pre-oxidation treatment on a gold concentrate and then cyanide leaching. Gold cyanide recovery The rate can reach above 91.42%. Fang Xihui et al. proposed a high-impregnation silver concentrate with a high copper content, complex embedding characteristics and low leaching rate of conventional processes. A pretreatment of lime and ammonium sulfate for a period of two stages and no re-grinding enhanced leaching process was obtained. The leaching rate above % is 9% higher than the on-site indicator and has practical guiding significance. Wu Zaiyu used roasting-acid immersion-cyanide process to recover gold, silver and copper in complex gold concentrates. It was found that the calcination temperature, calcination time, type and amount of calcining additives had significant effects on the leaching rate of gold, silver and copper.

2Cyanide gold extraction process development

The cyanidation process is still the most commonly used gold extraction method. The cyanidation process includes diafiltration cyanidation, stirred cyanidation, heap leaching, carbon slurry method, carbon leaching method, and whole mud cyanidation. In order to improve the leaching rate, further increase the leaching rate and reduce the consumption of cyanide in the cyanidation process, the researchers mainly carried out the following two aspects: (1) leaching conditions such as temperature, oxygen, particle size, etc. (2) Adding ammonia, sodium hydroxide and other auxiliary infusion during the process of cyanide gold extraction to improve the gold leaching index. The following is a brief review of the development of the above cyanidation process.

(1) Development of diafiltration cyanide and stirred cyanidation process

Diafiltration cyanide and stirred cyanide are two common methods for cyanidation of gold and silver. The diafiltration cyanide equipment is simple, the investment is small, the effect is quick, the solvent consumption is small, the electricity is saved, and the cyanated pulp does not have to be concentrated and filtered. The stirring cyanidation method has the characteristics of high degree of mechanization, short leaching time and high leaching rate.

Cui Yiqi et al. calculated the cyanide immersion silver process and found that as long as the oxidation potential (U) of the oxidant is greater than -0.3097V, the cyanide immersion silver reaction can occur thermodynamically with the participation of oxidant. Teng Yun et al. conducted a pilot study on the cyanide leaching method for the Chagan silver deposit, and determined the optimum cyanidation conditions suitable for the ore. Under this condition, the silver leaching rate was 54% to 67%. Huang Weiping, Chen Qinggen and others have done similar work. Wang Jiqing et al. found that the gold concentrate in Shandong Jinzhou was treated by edge grinding and oxycyanation. It was found that adding a proper amount of ammonia water in a section of grinding can enhance the leaching of gold and gold ore and improve the leaching rate of gold and silver. It inhibits copper leaching and improves the effective utilization of sodium cyanide. Compared with no ammonia, the gold cyanide leaching rate increased by 0.47%, the silver leaching rate increased by 5.33%, and the copper leaching rate decreased by 6.50%. In order to improve the leaching rate of gold and silver in a gold oxide ore, Luo Xianping proposed a process of using calcium peroxide to enhance cyanide leaching for the characteristics of ore. Compared with the original process, the leaching rate of gold and silver is obviously improved. The increase is about 5% and 9%, and the economic benefits are very obvious.

(2) Development of heap leaching process

The cyanide reactor has no gold extraction rate, strong adaptability to ore, high land quality, simple process, easy operation and low production cost. It is still the main method for low-grade gold ore leaching production. It treats low-grade ore of 0.5~3g/t, and the recovery rate of gold can reach 50%-80%.

In the design and application of gold heap leaching process, the ore cause, cyanide solution concentration, temperature, spray intensity, dissolved oxygen and many other factors need to be properly grasped and controlled. These factors will directly affect the application of gold accumulation process. The effect; therefore, reasonable grasp and control of the various factors affecting the application of gold heap leaching process, can better guide industrial practice, play the maximum function of heap leaching process, make low-grade gold mine, gold-bearing waste rock and tailings, etc. The gold in the ore resources can be effectively extracted and maximized. Wei Zongwu et al. conducted an orthogonal heap leaching test on an oxidized gold mine in Guizhou, and found that the factors affecting the gold leaching effect were ore particle size > leaching time > NaCN dosage > lime dosage. At the Zijinshan Gold Mine Concentrator, He Ri should pass the heap height affecting the heap leaching effect, the heap ore particle size, the NaCN concentration and pH value of the spray solution, the NaCN concentration and pH value of the noble liquid, the spray system, and the spray. The main process parameters such as strength were optimized, and the reasonable process parameters of the light industry were further determined. Quartz , Yu Zhongbao and others have also done similar research work.

Yin Jiangsheng et al. used a tailings granulation heap leaching method for a 200t/d gold ore beneficiation plant established in 1985, which enabled the mine to increase gold production without increasing the cost of geotechnical exploration. Qi Ruixia et al. found through experiments that the leaching process of copper and gold from the Minnan copper-gold ore was carried out by acid leaching copper and cyanide leaching gold. The leaching rate of copper was 86.82% and the leaching of gold was obtained. The rate is 82.10%, the acid consumption is 38kg/t, and the cyanide consumption is 0.32kg/t. Du Libin, Wu Hanquan and others have also done similar work.

(3) Development of carbon slurry method

The carbon slurry method generally refers to a process in which a monovalent gold cyanide [KAu(CN)2] is adsorbed by carbon after completion of cyanidation leaching. It has only developed in the past 30 years and has become a new technology for gold smelting. The carbon slurry method is mainly applicable to gold-containing oxidized ore with high sludge content.

Changning City Longxin Mining Company mining dressing and smelting scale of 400t / d gold mine in recent years with the nature of the ore changes, using the original all slime cyanidation - Zinc powder replacement process, the recovery rate is only about 70%; and with The granulation heap leaching-carbon adsorption gold extraction has a recovery rate of less than 50%. Through technological transformation, the company replaced the original whole mud cyanide-zinc powder replacement process with carbon slurry method. The recovery rate of gold increased by nearly 10%, and the annual profit was 2.1 million yuan. Wang Ting et al. found that the cyanide leaching rate of the ore directly using the carbon slurry process was 5% to 10%, and the leaching rate was quite slow. After oxidation with NaOH and H2O2 for 12-15 hours, the anti-filming agent and activator were added during the cyanidation process, and the cyanide leaching rate was greatly improved and the leaching speed was accelerated.

(4) Development of carbon immersion method

The carbon immersion method is the same as the carbon slurry method, which is a new hydrometallurgical process discovered in recent years. The two principles are the same. Foreign scholars believe that the difference between the two processes is that the carbon slurry method is a separate process of leaching and carbon adsorption, and the carbon leaching method combines the two processes of leaching and carbon adsorption into one. get on. The ore contains high levels of impurities such as arsenic, antimony and copper, and the carbon-dipping method is superior to the oxygen-consuming gold ore.

Since the 1970s, a carbonaceous gold mine has used the flotation-gold concentrate roasting-cyanide gold extraction process, and the gold recovery rate is about 60%, which has not been exploited for many years. Ma Jing et al. optimized the multi-factor process conditions for the presence of graphite , organic carbon and gold in the ore. The final study used pretreatment-cyanide carbon leaching gold extraction process, pretreatment-cyanide carbon leaching gold leaching rate. The leaching rate is higher than 5% by direct cyanide carbon leaching. Gold extraction by carbon leaching process, in order to fully expose gold, in order to dissolve with CN-, generally requires fine grinding, domestic carbon immersion plant grinding fineness is more than -0.074mm accounted for more than 90%, which usually requires two paragraphs Grinding can achieve the required fineness. In the design and production of Xiajiadian gold mine, gold extraction was carried out under coarse grinding according to the nature of the ore. The gold leaching rate reached 94.26% on average, and the average sodium cyanide dosage was 262.7g/t, which was much lower than the general production.

(5) Development of the whole mud cyanidation process

The whole mud cyanidation leaching gold extraction is suitable for fine-fine-grained, dispersed, oxidized quartz vein type gold ore. The method has the advantages of mature technology, stable index, high recovery rate, strong ore targeting, and real estate gold. .

In recent years, some concentrating plants have carried out improvements in the whole mud cyanidation process, and the gold leaching rate and recovery rate have been significantly improved. Yang Changying et al. conducted a pilot study on a refractory gold mine and found that the two-stage recovery method of whole mud cyanidation + flotation achieved an ideal technical index of 64.78% gold leaching rate and 93.05% recovery rate. Guantong is aimed at the characteristics of fine-grained natural gold with severe weathering and porous structure in a gold mine in Shandong. Under the condition of gold grade 4.45g/t, the whole mud cyanide leaching process can be used to obtain a gold leaching rate of 97.30. %index of. Liu Guoying et al. used a full mud cyanidation gold leaching process for an oxidized quartz vein type gold mine in Hebei Province, and determined the fineness of the ore grinding to be -0.074mm, accounting for 85%. Adding human lime to alkali pretreatment of gold ore, and then adding The sodium cyanide leaching gold obtained a test index of a leaching rate of 96.89% and an adsorption rate of 99.55%.

The addition of an infusion agent during the whole mud cyanidation process accelerates the leaching of gold and increases the leaching rate of gold. Liu Xiaozhu et al. used limestone-type carbonaceous fine-grained gold ore as the research object to carry out the experimental study on the whole mud cyanidation and the addition of infusion enhancer leaching. Bi Fenglin et al. used the orthogonal factorial method for the ore to optimize the control conditions of the whole mud cyanidation. Finally, the NaOH was determined as the alkali leaching agent, and the optimal process parameters were obtained. Zhang Xiaoping, Bai Hetian and others have also done similar work.

(6) Development of other methods

The resin slurry method is a relatively advanced filterless gold extraction technology. The resin has the characteristics of fast adsorption rate, large adsorption capacity, desorption under normal temperature and pressure, and has been gradually applied in gold production. Compared with traditional activated carbon, resin has the advantages of strong anti-pollution ability, strong wear resistance, easy regeneration and high efficiency. Although the resin slurry method has many advantages over the carbon slurry method, the resin slurry method is restricted by the properties of the special resin for the gold extraction, the resin desorption process and the facilities. The treatment scale of the Bupleurum Gold Mine Concentrator is 150t/d. The resin slurry method is used. Compared with the original whole zinc cyanide powder replacement process, the leaching rate is increased by 6.06%, and the total gold recovery rate is improved. 5.58%, the economic benefits of the concentrator have also been greatly improved. The original gold extraction process of Dongxi Gold Mine in Huoshan County, Anhui Province is a carbon slurry method. The gold and silver leaching rate and recovery rate are not high. The Jilin Provincial Metallurgical Research Institute conducted an industrial test of the resin pulping method in the gold mine. The leaching rate of gold reached 97.29%, the adsorption rate was 99.95%, the leaching rate of silver was 66.67%, and the adsorption rate was 99.66%. In view of the shortcomings of the resin slurry method, Han Chunguo et al. conducted a comparative test on the adsorption capacity and selective adsorption capacity of D370, 201×4 and 201×7 resins adsorbed from cyanide noble liquid. D370 type resin has large adsorption capacity for gold and silver, good selectivity, desorption under normal temperature and pressure, and good desorption effect.

Ultrafine grinding has been widely used in paper coatings, plastics, rubber, printing inks and petrochemical industries, and micron or submicron powder processing technologies are maturing. With the development and improvement of ultra-fine grinding technology, many scholars have carried out research on the use of ultra-fine grinding to open the sulphide package to dissociate gold, and have achieved different degrees of progress. Lan Bibo [201] conducted an ultra-fine grinding-cyanide leaching gold test on a refractory gold concentrate, and obtained the optimal process conditions. Under this test condition, the gold leaching rate can reach 93.70%, a low grade. The gold ore has the characteristics of low-sulfur semi-oxidized fine particles, and the leaching rate of gold by conventional grinding cyanide leaching is about 70%, and the gangue wrapped gold is basically not recovered. Luo Zengxin adopted ultra-fine grinding technology for this ore, which made the continuous body fully dissociated and combined with the whole mud leaching gold extraction process. The good leaching rate was 94.33%, and the gold leaching rate was improved compared with the conventional cyanide leaching. 25%.

In some specific mines, researchers have proposed new processes for oxygen-rich leaching. An oxidized gold mine is located in the plateau area, with high altitude and low oxygen content in the air. The conventional cyanidation process is adopted, and the leaching period is long, which will affect the economic benefits of the mine. In order to ensure the gold recovery rate and shorten the gold leaching period, Hu Min et al. proposed a new process of oxygen-rich leaching of gold oxide ore. The adsorption rate of gold can reach 99.14%. Compared with conventional leaching, the oxygen-rich leaching time can be shortened. Times, and the amount of sodium cyanide used in the experiment only needs half of the conventional leaching.

3 Development of clean gold extraction technology

Despite the mature technology, simple operation and low cost of cyanide gold extraction, its toxicity is extremely harmful to human ecological environment and life safety. At the same time, it cannot directly deal with some refractory ore. The increasing number of refractory gold mines for cyanidation, the research on the method of non-cyanide gold extraction has also been active, and there have been progress in the following aspects: (1) The thiourea method has been solved by adding additives (such as CL). thiourea gold leaching during consumption problem; (2) found that iron, oxygen, sodium hexametaphosphate and other factors in the system have a greater impact thiosulphate leaching of gold; (3) a method discovered by the The ZLT chlorination immersion gold system consisting of oxidizing organic matter ZLT and sodium chloride can solve the problem of high cost of inorganic chlorination.

(1) Thiourea method

The thiourea method is one of the more studied methods of non-cyanide gold extraction. In recent years, many gold and silver mines have improved the original thiourea process to obtain better indicators and benefits. An iron-manganese type gold-silver mine is a low-grade refractory ore. When leaching gold and silver directly with thiourea, the gold and silver leaching are 46.25% and 18.37%, respectively, and the thiourea consumption is 12g/t. Zeng Liang et al. found that by preheating the ore sample by heating the ore sample to 90 ° C and adding pyrite and concentrated sulfuric acid, the optimum leaching conditions were at pH 1.5, potential 300 mV, sodium sulfite 6 g, and leaching time 4 h. The leaching rates of gold and silver were 98% and 45%, respectively, and the consumption of thiourea was only 6g/t. Luo Binhui, He Xiaocai and others also carried out similar work. Dong Suiming et al. conducted an experimental study on the addition of an additive CL thiourea leaching gold to a sulphur-rich high arsenic gold concentrate. The results show that the additive CL can improve the thiourea leaching process, reduce the thiourea concentration required for leaching, and increase the gold leaching rate, which can make the gold leaching rate of the gold concentrate reach over 89%.

(2) Thiosulfate method

D. Feng and JSJvan Deventer have done a lot of research on the extraction of gold and silver by the thiosulfate method. They have found through extensive experiments that the presence of pyrite, hematite, metallic iron and iron ions in the thiosulfate system can seriously affect the leaching of gold; the use of thiosulfate from pyrite concentrates and sulfide ores Adding a small amount of manganese dioxide to the gold extraction system can increase the leaching rate and leaching rate of gold without increasing the consumption of thiosulfate; in the pure gold thiosulfate system, the presence of oxygen will reduce gold. The dissolution of the leaching and the presence of nitrogen bubbles will greatly increase the dissolution of gold; the type of thiosulfate significantly affects the leaching of gold in the ore, and the dissolution behavior of gold and different thiosulfate determines the extraction rate of gold; In the two systems of leaching pure gold and gold sulfide ore, ammonium orthophosphate and sodium hexametaphosphate can increase the leaching rate of gold. JA Heath et al. also found through experiments that the EDTA and oxalate complexes of ferric iron have low reactivity with thiosulfate, and can increase gold when adding thiourea as a leaching catalyst. Leach rate. The experiment also shows that the presence of pyrite and pyrrhotite reduces the iron complex, and the gold leaching rate is significantly reduced.

Domestic researchers have also made considerable progress in the study of the thiosulfate method. Zheng Ruofeng et al. conducted a field test on a 400t oxidized gold ore in an alpine region of Sichuan using a film-copper ammonia thiosulfate drip heap leaching gold extraction process, and obtained a good indicator of a gold recovery rate of 60.8%. Peng Huiqing et al. used the green thiosulfate method to immerse gold in the tailings recovery gold of a magnetic separation plant in Anhui Province. The best process conditions for gold leaching were obtained through experiments. Under this condition, the gold leaching rate reached over 90%. . Zhang Qing applied ultrasonic enhancement to the catalytic oxidation of nitric acid and combined with thiosulfate leaching gold to propose a new wet leaching gold process for arsenic-containing refractory gold ore. The results show that the ultrasonic enhancement can accelerate the mass transfer process of nitrate ions, significantly accelerate the catalytic oxidation of nitric acid, and reduce the reaction temperature. At the same time, the combination of nitric acid oxidation and thiosulfate leaching in the ultrasonic field can destroy or dissolve the mineral surface. Elemental sulfur or passivation film greatly reduces the inhibitory effect of elemental sulfur on subsequent gold extraction and increases the leaching rate of gold. The gold leaching rate can be increased from 13.94% to 85.6% of conventional cyanide leaching.

(3) Chlorination

Chlorination, also known as liquid chlorination or hydration, refers to a method of extracting gold using chlorides having oxidizing properties, including liquid chlorine, hypochlorite, high temperature chlorination, and the like. However, due to the high cost of many of the above-mentioned inorganic chlorination methods, it is difficult to truly replace the cyanide gold extraction process.

The chlorination process has had some innovation in recent years. Shi Yangao et al. developed a ZLT chloride leaching gold solution system consisting of oxidizing organic compounds ZLT and NaC1. The system has strong oxidizing ability and can oxidize elemental gold into soluble chlorogold complex ions [AuCl4]. ]-, on this basis, the corresponding ZLT gold extraction process research and test was carried out for a variety of different gold and silver raw materials, so that the ZLT method can be widely applied to the treatment of gold-silver-containing oxidized ore, primary ore, low grade. Polymetallic ore, high arsenic and high graphite carbonaceous refractory gold ore and copper-lead electrolytic anode slime with high grade gold and silver.

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