Because of the large number of developing gold ore resources, easy to choose easy to deal with dwindling gold ore grade decreased gradually, more and more complex ore components. The major gold producing countries in the world, including China, have to turn their attention to the processing of difficult-to-treat ore. It is believed that contain arsenic, antimony or sulfur, carbon content of these gold ores using conventional methods difficult to deal with, will soon become an important source of the world's gold production. For gold ore arsenic, sulfur, refractory which reason, because the mineral composition of such complex ores, containing a considerable amount of interfering elements of gold extraction process, disseminated gold in the pyrite in the form of very fine, arsenic The formation of adhesions and inclusions in pyrite and stibnite makes it difficult to enrich and recover by general mechanical beneficiation and cyanide leaching methods. It must be pretreated to remove arsenic, sulfur, etc., which interfere with gold leaching, and then Dip leaching gold. For carbon-containing gold arsenic ore or concentrate, the reason for its refractory treatment is that, in addition to the symbiosis of gold and sulfide (mainly arsenopyrite, pyrite and part of stibnite), The noble metal cyano complex has a strong adsorption capacity of carbonaceous materials, and the ruthenium which occurs in stibnite, which makes the cyanidation process of the concentrate extremely complicated. The inhibition of gold by stibnite during cyanide is mainly manifested in the absorption of oxygen and free cyanide in solution, and the formation of secondary strontium salt film on the surface of gold particles, so when it is difficult to treat carbon-containing arsenic bismuth gold concentrate When cyanidation is carried out, it must be pretreated to dissociate the gold-containing sulfide. At present, more oxidative pretreatment methods have been studied, such as calcination, pressure oxidation, bacterial oxidation, chemical oxidation, nitric acid decomposition and electrochemical oxidation. The following describes their principles, characteristics, applicability and some examples of processing techniques. First, roasting A large number of scientific research and production practices have shown that for refractory box ores containing fine-grained gold-coated arsenic pyrite, pyrite, stibnite and carbonaceous ore, oxidative roasting or oxidizing roasting is used as cyanide. The ore preparation work before the chemicalization is technically and economically reasonable. If cyanidation of these raw materials is carried out directly without baking, the recovery rate of gold is not more than 50% to 70%. After pre-oxidation and bake, the cyanidation treatment may increase the recovery of gold to 95% to 97.5%. (1) Roasting of arsenic or sulfur gold ore For the treatment of gold ore or concentrate containing too much arsenic, sulfur gold or gold particles, the conventional method uses pre-oxidation roasting to remove harmful components, and then cyanide leaching of the calcine. The purpose of concentrate roasting is to fully expose the gold particles when the sulfide is decomposed, so that the impurity elements such as sulfur and arsenic in the concentrate can be volatilized as much as possible in the form of oxides, and the loose porous sand which is favorable for cyanation is produced. At present, the desulfurization rate of oxidizing roasting in foreign countries is generally 93% to 95%, the arsenic removal rate is 87% to 90%, and in China, it is 78% to 84% and 82% to 99%. Oxidation roasting is usually carried out in the range of 500 to 800 ° C, and in order to avoid agglomeration, the calcination temperature generally does not exceed 800 ° C. According to the arsenic, sulfur content, particle size, calcination temperature, calcination time, stirring strength and other conditions in the special mine, the desulfurization rate is generally 90% to 95%, the arsenic removal can reach 90%, and the roasting sulfur is 0.2%. 2%, when arsenic is 0.3% to 1.5%, the gold leaching rate is 92% to 94%. For example, Canada's Campbell Red Lake Mines gold selection plant uses two-stage boiling roasting. The first stage roasting temperature is 560 ° C, the second stage is 30 ° C, the calcined sand contains arsenic 1.6%, sulfur content is 1.0%, and the gold leaching rate is 97.3. %,: Canada's Giant Yellow Knife gold selection plant uses two-stage boiling roasting, the first stage roasting temperature is 500 ° C, the second stage is 540 ° C, the calcine contains arsenic 1.0%, sulfur is 2.5%, and the arsenic removal rate is 91.6%. The desulfurization rate was 87.9%, and the gold leaching rate was 93.7%. The degree of roasting required for gold to reach the highest cyanide leaching rate depends on the gold in the concentrate. For gold-arsenic pyrite concentrate, arsenic removal and desulfurization are very important, and two-stage roasting is required. The first stage of arsenic removal is carried out at 450-600 °C, and the second stage desulfurization is at 550~. It is carried out at 800 °C. Whether a certain kind of concentrate is used for one-stage roasting or two-stage roasting, how high the temperature needs to be, can only be determined by experiments. When arsenic is removed from the feedstock by two-stage calcination, the amount of air supplied during the first stage of calcination should be less than the amount of air required to completely roast all of the sulfides. In this way, the roaster can be placed in the weak oxidizing gas cadmium , which can oxidize pyrite and arsenic pyrite into a mixture of pyrrhotite and hematite. The composition of the furnace gas is mainly nitrogen, water vapor and sulfur dioxide, and arsenic is Oxide (As 2 O 3 ) or arsenide forms volatilize, under which arsenic is rarely left in the form of iron arsenate, mostly calcium and magnesium arsenates. The Soviet scholar BB Lotje Ishkov studied the oxidative roasting mechanism of arsenic pyrite (FeAsS). The results show that in order to reduce the gold content in the calcined leaching residue, it is necessary to control the change of arsenic pyrite in the roasting process. feature. When the calcination temperature is 480 ° C in the presence of oxygen, sulfur in the arsenopyrite is burned into SO 2 gas, the temperature is increased, and the oxidation rate of sulfur is accelerated. When the calcination temperature reaches 1100 ° C, the desulfurization rate is 99.2% to 99.5%. Increasing the concentration of oxygen, the rate of combustion of sulfur is increased, and the concentration of oxygen is lowered. Even if the combustion temperature is reached, sulfur oxidation may stop. In the absence of air, arsenic can still enter the gas phase as follows: 2FeAsS+1 When oxidizing and roasting gold-arsenic pyrite is used abroad, the characteristics of arsenic and sulfur burning in the roasting process are different. Since Fe 2 + and Fe 3 + arsenate (MeAsO 3 , Me 3 AsO 4 ) are fusible, the calcination is preferably carried out in two stages. The first stage is for arsenic removal and prevention of FeAsO 3 and Fe 3 AsO 4 . The fusible material is calcined in a weak oxidizing atmosphere at 550-580 ° C, and the second stage is calcined at 600-620 ° C under an excess of air. At this time, it is difficult to form a fusible substance and a good porosity is obtained. The calcination, calcination contains As less than 1% to 1.5%. Concentrates treated with the Belle Terre gold mine in Quebec, Canada, contain only 2.3%. Low-temperature calcination at 482 ° C using a Wedge type multi-pile (baking) furnace removes almost all of the arsenic. According to the available data, the world's major gold-producing countries such as South Africa, the Soviet Union, Canada, Australia, the United States, Ghana and other countries use oxidizing roasting and arsenic removal methods for gold-containing arsenic concentrate recovery. The Dalny mine in Zimbabwe uses a boiling furnace to treat flotation concentrates containing 93 to 10 lg/t of gold, 22% of sulfur and 4.5% of arsenic. The treatment capacity is 600 t∕d. The boiling furnace is 5m in diameter and consists of two chambers A and B. According to the quantity of concentrate obtained, the working time of the roaster is 14~16h every day and night. The concentrate contains 72%~78% solids and 22%~24% sulfur. . The indoor furnace temperature of A is maintained at 588 ° C, and the furnace temperature is controlled by spraying water onto the boiling layer. Room B is mainly used to gradually cool the calcine. The furnace temperature in room B is maintained at 340-450 ° C. The arsenic grade in the calcine is 1.4%, sulfur is 1%, and gold is 120% to 150 g/t. In order to remove arsenic and prevent the formation of FeAsO 3 and Fe 3 AsO 4 fusibles, the calcination needs to be carried out in a weak oxidizing atmosphere or an inert atmosphere (restricted air feed rate) at 550 to 580 ° C, and for desulfurization and good porosity. The calcination needs to be calcined at 600-650 ° C in excess of air. Two-stage peening can ideally meet the above process requirements. The Romanian Dalni gold-making plant adopts a flotation-two-stage oxidation roasting-cyanide leaching process, and processes 800t of ore daily. The flotation concentrate contains gold of 90~1201l/t. Sulfur is 16% to 22% and arsenic is 6%. The concentrate is calcined at 25t∕d, and calcined in two stages at 560°C. The calcine contains 125-150 g/t of gold, 1%-2% of sulfur, and 1%-1.5% of arsenic. The calcination is cyanide leaching, the leaching rate is 95%-97%, and the tailings leaching gold is 4.5%-6.0g/t. The Irkutsk Branch of the National Institute of Rare Metals of the USSR and the Institute of Non-ferrous Metals of the Soviet Union have done a lot of research work on the oxidizing roasting of gold and arsenic concentrates. The Soviet Institute of Nonferrous Metallurgy completed the boiling of arsenic pyrite in the Dalazon mine. The design of the roasting workshop was officially put into production in 1957. The gold and arsenic concentrates were treated with gold: 45% to 62g/t, silver 61 to 83g/t, arsenic 9% to 13%, and sulfur 32% to 40%. . The preferred volatile arsenic process is employed. The mechanical dust output in the roaster is 20% of the concentrate. After electric dedusting, qualified industrial white arsenic containing 92% to 99% As 2 O 3 can be obtained, including gold 1~2g/t, in the baking sand. The actual recovery rate of gold is 96.1% to 97%. In foreign factories, the gold in the sand is often enriched in the hearth during the boiling roasting practice, especially at the bottom of the furnace. After long-term operation of the roaster, the grade of the box in the calcine of the furnace bottom can exceed 2 to 3 kg/t or even higher. This is mainly due to the continuous precipitation of gold dissociated during the oxidation of gold and sulfide in the concentrate. China has more gold and arsenic resources, and it is necessary to remove arsenic and sulfur in advance in order to effectively recover the gold. Hunan Institute of Nonferrous Metals has done a lot of research work on roasting and arsenic removal of arsenic-bearing gold concentrates, and the arsenic gold concentrate of Hunan Golden Cave Gold Mine (component: gold 98.5g∕t, arsenic 19.35%, sulfur 18.92%) Iron, 25%, silver 8.5g / t, 锑 0.025%, copper 0.062%, lead 0.025%) using kiln arsenic removal process. The main indicators are: arsenic volatilization rate of 99.16%, desulfurization rate of 78.4%, calcine containing gold 166g/t, chalk grade (including As 2 O 3 ) 97.97%, and white gold loss of 0.66%. Practice has proved that the rotary kiln roasting gold arsenic concentrate, in addition to investment, has a quick effect. In addition to the advantages of easy operation, it is mainly able to achieve different requirements for arsenic and desulfurization in a kiln. A gold mine in Shandong Province is a medium-sulfur type gold-bearing iron ore with high sulfur grade, low gold grade, fine gold inlay size, and some gold inclusions in the ore. The key issues in dealing with such ore are It is to eliminate the interfering elements, and at the same time expose the gold to the cyanide solution. Through the experimental research on several kinds of smelting process, it is considered that the reasonable scheme for the medium-sulfur type gold-bearing iron ore is to adopt the mixed flotation + mixed concentrate oxidizing roasting + cinder cyanide process. Therefore, the total recovery rate of the gold smelting and smelting in the test was over 90%, which was more than 15% higher than the current production process index of the mine. (2) Roasting of arsenic, antimony or carbon gold ore When calcining a carbon-containing gold-arsenic concentrate, it is preferably carried out in two stages: the first stage of calcination is carried out at a temperature of 500 to 600 ° C and the air supply is insufficient; at a temperature of 650 to 700 ° C and an excess of air is fed. The second stage of baking is carried out. The first stage of calcination should burn arsenic to the calcined less than 1%: and the second stage of roasting should burn out the carbon and sulfur. In order to achieve self-heating calcination in the calciner, the sulfur content in the concentrate should be 22% to 24%. The calcination of gold-bismuth concentrate can cause the antimony to evaporate, but the calcination temperature should not be higher than 650 °C, so as to avoid the melting phenomenon of reducing the exposure of gold. The gold-bismuth concentrate is usually calcined in two stages: the first stage of calcination is carried out at a temperature of 500 to 600 ° C for 1 h; the second stage of roasting is carried out at a temperature of 1000 ° C for 2 to 3 h. The calcination is first leached with dilute sulfuric acid and then treated by cyanidation. The calcine obtained by roasting a high-carbon flotation concentrate is characterized by a small amount of arsenic, about 1%, a cerium content of 0.6% to 0.8%, and a carbon content of 4%. It is preferred to treat such a calcined material at a temperature of 80 to 90 ° C for 1 h with a 7.5% alkali solution, and arsenic is leached to recover gold. The adsorption of cyanidation by AM-2B anion exchange resin can increase the gold recovery rate by 1% to 2%, and the recovery rate of carbon-containing calcine can be increased by 5%. Use high concentration of sodium cyanide (0.4 ~ 0.5g ∕ L), and cyanide under the condition that the anion exchange resin AM-2B accounts for 4% to 5% of the ore, which can reduce the adsorption of gold by carbon, cyanide operation The recovery rate of Zhongjin is 85% to 87%, but in the case of carbonaceous materials, the recovery rate is about 79% to 81%. The carbon slurry method has a good economic effect, and has become an important method for recycling gold today due to its simple process, low investment and low production cost. The carbon slurry process includes the following processes: 1. Adsorption of activated carbon in leaching pulp; 2. Desorption of gold-loaded charcoal: 3. Recover gold from the desorbed gold-containing liquid by electrolysis: 4. Desorption of desorbed charcoal. Since the United States built the world's first large-scale carbon slurry gold extraction plant in 1973, more than 40 carbon pulp plants have been put into production in the United States, South Africa, Canada, Australia, the Philippines and Chile. China's Linghu Gold Mine and Shaanxi Lijiagou Gold Mine Carbon Pulp Plant have been put into operation in 1984 and 1986. The two sets of 500t and 250t carbon slurry processes imported from the United States were also completed and put into operation in Zhangjiakou and Shaoguan gold mines. The carbon leaching method is a development of a carbon slurry method which is suitable for treating those refractory gold ores in which ore having carbonaceous components (including organic matter) are present. Since the carbonaceous component in the ore adsorbs gold in the cyanide solution and causes "depletion loss", the effect of using the carbon slurry process to treat such ore is inferior, so a new carbon leaching process has been developed. The carbon immersion method differs from the carbon slurry method in that the carbon slurry method is first immersed and then sucked, while the carbon leaching method is immersed in the side suction, and the kinetic conditions for dissolution of gold are improved by suction while immersing, and the leaching result is More practical. The McCalle Gold Mine in the United States has been completed and put into operation a large-scale carbon immersion gold extraction plant. Soviet scholar BH Rasley was studying gold containing 31 to 34 g/t. For the boiling roasting of flotation concentrates with 20% to 26% of sulfides, 3% to 5% of arsenic, 锑0% to 18%, and 1.4% of carbonaceous minerals, concentrates containing no antimony or carbon, first stage The baking temperature is set to 450 to 500 ° C, and the second stage is 600 to 650 ° C. For carbonaceous concentrates, the first stage is 550 ° C and the second stage is 650 ° C. Only the calcin produced under these conditions can be fully recovered in the adsorption cyanide. The Irkutsk branch of the National Institute of Rare Metals of the Soviet Union studied carbon-bearing gold-arsenic concentrates and, based on the results of the study, developed oxidative roasting and decomposition of arsenopyrite in a period of roasting and in two-stage roasting. The sulfide and carbon are completely oxidized, and the slag is ground, and the slag is further ground and then subjected to selective (95%-0.074 mm), two-stage cyanidation and a cyanide filter cake for intermediate alkali treatment. After cyanidation, the disk recovery was 93%. The Soviet Union has oxidized roasting of carbon-containing arsenic-containing antimony concentrates obtained under semi-industrial conditions (containing 17.9% of total sulfur, 4.5% of total arsenic, 1.17% of total cerium, and 1.84% of organic carbon). The calcination is at 450 ° C and 600. It was carried out in two stages in a muffle furnace at 650 ° C, and each stage was baked for 2 h. The desulfurization rate of calcination is 97.7%, the arsenic removal rate is not more than 58.5%, and the bismuth oxide is left in the calcine, and the decarburization rate is 100%. When calcined at a lower temperature (a calcination of 300 ° C, 3 h, two-stage roasting is 500 ° C, 1 h), the arsenic removal rate can be improved under conditions of deep desulfurization (98.0%) and bismuth (83.8%). 90.6%, at this time, the content of arsenic and antimony in the calcined sand was 0.52% and 0.25%, respectively, while in the case of general two-stage roasting (450-500 ° C and 600-650 ° C), it was 2.2% and 1.7%, respectively. The carbon content is 0.4%. However, in the case of adsorption cyanation of the calcine pretreated with alkali, the yield level of the noble metal is still similar to that obtained by the above calcination conditions. At the same time, the above-mentioned concentrate was subjected to a thermal decomposition roasting test. Thermal decomposition was carried out in a special test apparatus with air at a temperature of 800 to 850 ° C for 2 h and a negative pressure of 0.1 × 10 6 Pa in the system. The calcined calcined sand contains 0.18% arsenic, 14.56% sulfur, 2.1% organic carbon and 0.72% cerium. The process arsenic removal rate is 96.7% and the desulfurization rate is 32.3%. When the thermal decomposition temperature is raised to 950 ° C, the cerium content in the calcine can be reduced to 0.52%. Second, pressurized oxidation The pressure oxidation of gold-bearing concentrates and ores is an effective treatment for refractory gold-bearing minerals, especially for the treatment of some gold minerals associated with sulfides. Scholars from the United States, the Soviet Union and other countries have done a lot of research work on pressurized oxidative leaching. In 1985, Homestake Inc. of the United States deposited the McLaugblin gold mine in Livonia with a pressurized leaching process that processed 2,700 tons of ore. Democracy Germany conducted an expansion test of 250t ore, leaching at 200 ° C and a pressure of about 400 × 10 4 Pa, and then leaching 98.8% of gold from the leach residue by cyanidation. The Soviet Union leached at 180 ° C for 1.5 h, and the cyanide extraction rate of gold in the slag reached 98.5%. Sherritt Gorden Mining Company of Canada has conducted extensive research on pressurized oxidative pretreatment of gold and arsenic concentrates. The cyanidation recovery rate of gold was increased from 40% to 84% after pretreatment of the flotation concentrate containing 96g of antimony, 6.5% of arsenic and 34% of sulfur in the eastern part of Ottawa by pressurized oxidation for 1~2h. When the same method was used to treat flotation concentrates containing 226 g∕t, arsenic 8.5%, and 24.3% sulfur in northern Canada, the cyanidation recovery of gold was 98%. The Soviet Union has conducted comparative tests on oxidized roasting, pressurized oxidation and bacterial oxidation on gold arsenic ore. The sample is a flotation concentrate containing 7.5% arsenic, 18.8% sulfur and 11.5% carbon. The test results show that the recovery rate of calcined gold cyanide is 79.1%; the recovery rate of bacterial gold oxide is 81%-88%; the pressure is oxidized at 180 °C, and the recovery rate of gold is 89% by resin adsorption cyanidation method. . The paper published by Laskerin et al. demonstrates that gold-containing arsenic pyrite containing arsenic is about 6% and sulfur is about 28% and is accompanied by carbonaceous materials by weak alkaline-pressure leaching cyanidation. The recovery rate can be increased by 90% to 95%. Most of the gold particles in the sample are continuous, so the leaching effect is better. The conditions were treated in an autoclave, the temperature was allowed to be 180 ° C, and the pressure was 98 × 10 4 Pa. Mountiin Ita and Reuison Mining Company of Pl8cer Development Ltd jointly conducted oxidative roasting, bacterial oxidation and pressurized oxidation tests on the Poregera gold ore in Papua New Guinea. The results show that pressurized oxidation is The most effective pretreatment method. The gold arsenic sulfide iron ore of 14g/t, 28.5% iron and 36% sulfur is treated by pressure oxidation at 180 °C, and the cyanidation recovery rate of gold is 97%; the calcination cyanidation is 77%; Bacterial oxidation was 86.5%; conventional cyanidation was 32%. In the early 1980s, the Sherritt Research Center conducted a pressurized oxidation test on pyrite or arsenopyrite concentrates and gold in ores. The test temperature was generally 170-190 ° C, the residence time was about 2 h, and the total pressure was 1500 ～. 2000kPa. The recovery rate of gold in all concentrates generally increases from 50% to 74% to 96% to 99%. This recovery rate is higher than that after baking. Recently, Arieuo Processing has succeeded in researching a new low-pressure oxidation leaching process, the Arseno process (referred to as the Asinno process), to recover gold from difficult ore concentrates and concentrates. The leaching process is a nitrate-catalyzed low-pressure oxidation leaching process suitable for the treatment of pyrite-type and arsenopyrite-type refractory gold ores and concentrates. Due to this catalysis, the leaching reaction is fast, and the sulfide can be completely decomposed in less than 15 minutes. Using the basic chemistry of this method, several processes have been developed for processing a wide variety of feedstocks, from ore with a lower sulphide content to a concentrate with a high sulphide content, Bacon Donaldson of Vancouver, Canada. Both the Bacon (Donaldson and Associate) and the Hazen Institute in Colorado, USA, have conducted extensive research and testing on the process, and have achieved good results, proving that this is a treatment of refractory gold ore. An economical and effective new process. According to reports, the Institute of Chemical Metallurgy of the Chinese Academy of Sciences has studied a catalytic oxidation acid leaching-cyanation method (which has applied for national patents). Compared with conventional methods, the new process can shorten the leaching time to 15 minutes and save a lot of titanium metal materials. Practice has proved that the treatment of high arsenic and high sulfur gold concentrate by this method can completely oxidize the arsenopyrite and pyrite, and increase the cyanide leaching rate of gold to over 97%. Zhongnan University of Technology broke through the frame of pressure leaching, using MnO 2 as an oxygen donor, and leaching refractory slag of refractory arsenic sulfide gold ore with H 2 SO 4 at atmospheric pressure. The slag contains 76g of strontium, 16.9% of sulfur (the elemental sulfur has been removed), 20.31% of iron and 9.74% of arsenic. Under the optimal conditions, FeS and toxic sand are almost completely decomposed. When leaching with sodium polysulfide, the gold leaching rate is >98.5%, and arsenic and manganese can also be recovered separately. This increases the possibility that the law can be applied to small and medium-sized mines. Third, bacterial oxidation Bacterial leaching has been developed in recent years. It is suitable for the treatment of difficult-to-dip gold-bearing sulfide ore (such as pyrite, arsenopyrite, etc.). This method turns gold-bearing sulfide ore into a sulfate solution and then uses cyanide. The leaching residue is leached to recover gold. Papua New Guinea was leached with bacteria to soak gold with fine particles, submicroscopic gold and gold in solid solution in pyrite. The leaching rate of gold was 86.5%. The Soviet Union used the bacterial leaching-cyanide method to treat gold ore containing carbon, arsenic and antimony. The leaching rate of gold was 94.5%. Canada's Giant Bay Resources uses a bacterial leaching-cyanide process to treat Salmita refractory gold ore, with a gold leaching recovery of 95.6%. The recovery rate by conventional cyanidation method is 65%. Carbon-bearing gold-arsenic concentrates are very difficult to handle. Gold is symbiotic with arsenic pyrite in these concentrates. The carbonaceous shale contained in the concentrate has a high adsorption activity for the gold cyanide complex. The carbon-gold-arsenic concentrate treatment process stipulates that carbon shale is pre-separated by flotation method, bacterial leaching is carried out on the flotation tailings, and cyanidation is carried out on the leaching residue. After leaching for 70 hours, the arsenic content in the concentrate decreased from 6.6% to 1.0% to 1.2%, and the arsenic sulfide oxidation rate was 93% to 95%. After the adsorption cyanidation of the dross, the recovery rate of adsorbed cyanide gold was 92%. The gold recovery rate is only 5% to 10% if the raw concentrate is cyanated directly without prior bacterial leaching. The carbonaceous concentrate obtained by flotation contains 20g of strontium and 1% of arsenic. It can be placed in copper or lead concentrate for fire treatment to recover gold. When the Soviet Union used H. ferrooxidans to treat gold arsenic flotation concentrate, the oxidation rate of arsenopyrite reached 87%-91%. When the bacterial leaching residue was cyanated, the recovery rate of gold reached 88%-90%. Mineral Leiching Technologies has proposed bacterial leaching of sulfur, arsenic, antimony gold ore and concentrates. Bacteria break down gold-containing sulfide minerals that are difficult to handle with reagents, while converting harmful impurities arsenic and antimony into inactive compounds. The process was carried out in a stirred tank for 1 to 5 days. The bacteria (T. thermophilus) oxidize pyrite and other sulfides to convert sulfur into sulfuric acid. In a strong acid medium, the activity of the bacteria is limited. Therefore, the pH should be kept above 1.0. After the bacteria are leached, the solid phase and the liquid phase are separated, washed, neutralized, and treated with a usual cyanidation method to extract gold. Bacterial leaching increased the recovery of gold from 76.3% to 95.6%. The Soviet Union used a bacterial method to treat gold-bearing-arsenic-arsenic concentrates, which mainly contained pyrite, arsenopyrite and stibnite. Due to the close symbiosis of gold and sulfide, the strong adsorption of carbonaceous materials on gold-containing cyanide solution and the interference of cyanide on cyanide make the concentrate difficult to process and directly leaching by conventional methods, and the gold recovery rate is low. Higher recovery rates are obtained with bacterial leaching rules. Practice has proved that when the arsenic, sulfur and antimony concentrates are treated by the bacterial pre-oxidation-cyanide method, the gold leaching rate can be greatly improved, and at the same time, the environmental pollution problem can be solved. Fourth, chemical oxidation This pre-oxidation method was first developed and industrially applied to the treatment of carbonaceous ore by the Carlin gold mine in the 1970s. The alkaline chlorination process is very effective when the ore is carbon due to the presence of harmful impurities and gold is contaminated in easily oxidized sulfide ore, so in the Carlin and Jerrit Canyon in the United States (Jerritt Canyon) This process is used in China. Only a third of gold can be leached from the carbonaceous ore by conventional cyanidation. Although the recovery rate of gold can be greatly improved after roasting, it is not suitable for investment costs and environmental reasons. Studies have shown that the harmful effects of carbon in ores can be eliminated by treatment with oxidants in the slurry. The limestone in the treated ore reacts with chlorine to form calcium hypochlorite, which in turn oxidizes the carbonaceous material to CO and CO 2 . After such pretreatment, the ore can be cyanated and leached with 83% gold, and the chlorine consumption is 13.7 kg ∕t·ore. In order to reduce costs, the Carlin Gold Mine has succeeded in researching a "secondary oxidation process". Most of the oxidation is now carried out by bubbling air in the presence of sodium carbonate in the first stage, and in the second stage the chlorination is used to complete the oxidation of the ore. Alkaline oxidation of pyrite was carried out in the laboratory using the Poregera concentrate in Papua New Guinea. It was found that NaOH is more effective than CiCO 3 or Ca(OH) 2 . After chemical oxidation pretreatment, the cyanidation leaching rate of gold is increased from about 25.30% (conventional cyanide) to 60% to 70%. Five, nitric acid decomposition Nitric acid is the most effective oxidant for pyrite and arsenopyrite and non-ferrous metal sulfides. When the sulfide is decomposed with nitric acid, both iron and arsenic can be transferred into the solution, and the metal ruthenium or the like is enriched in the insoluble residue. In order to decompose gold concentrate containing arsenic sulfide, scholars in the Soviet Union and other countries have conducted extensive tests using nitric acid as a leaching agent. The leaching conditions are HNO 3 150-200 g ∕L, liquid-solid ratio 5:1, temperature 75-85 ° C, The leaching time of sulfur, arsenic and iron was 96%, 98% and 97%, respectively. The residual nitric acid in the mother liquor is denitrified by calcination at 350 ° C, and the crystal residue is calcined at 650 to 700 ° C to solidify arsenic. The chemical reaction formula for the oxidation of metal sulfides with nitric acid in the presence of oxygen: The Soviet scholar Ð.К. Kumbazalov and others used nitric acid to decompose gold-arsenic sulfide concentrate. The mechanism of action is the arsenic transferred to the nitric acid solution when the concentrate is operated under optimal nitrate conditions. Sulfur is oxidized to nitrous acid and sulfuric acid, while the non-ferrous metal is completely transferred to the solution. Gold and silver are enriched in insoluble residues (leaching). After the cyanide treatment, the recovery rate of gold can reach 92% to 94%. Sixth, electrochemical oxidation For the treatment of gold, arsenic and carbonaceous ores, the purpose of the electrochemical oxidation method is to fully dissociate and expose the fine-grained dispersion gold encapsulated in the sulfide, and then recover the gold by cyanidation. The conditions are: liquid: solid = 5:1, current density is 8.3A∕L, leaching time is 8h, solution temperature is 50-70°C, and it is carried out in caustic soda solution, and the recovery rate of gold can reach the index equivalent to calcination. Level. The Soviet Union uses NaOH solution as the electrochemical oxidation leaching solution of arsenic pyrite and pyrite, which has the advantages of low price, high conductivity and no secondary process, and clarifies the electrochemical leaching of arsenic pyrite and pyrite by NaOH. Kinetics and mechanism. The oxidized concentrate can be leached from 72% to 78% of arsenic pyrite and 45% to 53% of pyrite in the optimum conditions of NaOH concentration of 2.5 to 3.75 mol∕L and solution temperature not exceeding 50-60 °C. . For specific concentrates and minerals, the leaching rate depends on the unit volume of the cell, the yield of oxygen in the solution, the anodic current density, the size of the ore and the composition of the concentrate. Conclusion (1) The cyanidation method is the most commonly used method for extracting gold from ore. Most of the world's gold selection plants still use this method. However, the refractory gold ore containing arsenic, sulfur, antimony and carbon is not suitable for direct treatment by conventional cyanidation. Therefore, countries all over the world attach great importance to the pretreatment process of refractory gold ore and study several comparisons. An effective process plan. (2) At present, there are many oxidative pretreatment methods, such as roasting, pressurized oxidation, bacterial oxidation and chemical oxidation. Although pressurized oxidation and chemical oxidation are used in some gold mines, they have limited limitations. The treatment volume is small, the grade is low, and the mine with low sulfur content is economically cost-effective. The bacterial oxidation is basically in the experimental research stage. Only in a few countries such as the United States and South Africa, industrial production has just begun. It is estimated that there must be It will take a while to promote the application in industry. (3) For the treatment of gold ore containing arsenic, sulfur, antimony and carbon, roasting is the most commonly used pre-oxidation method. At present, large-scale gold-making plants at home and abroad mostly use roasting process, usually using two-stage roasting method. The first section maintains low temperature and anoxic conditions, while the second section is operated under higher temperature and oxygen excess conditions. China's rotary kiln roasting satisfies the above requirements in a kiln. (d) Although roasting is still a relatively common method in some places, it is required to achieve a certain amount of sulfur and/or carbon in the ore during self-heating roasting. Due to the characteristics of high air volume, low speed, wide coverage, and space saving, commercial fans have been favored by many companies. Commercial Fan,Commercial Ceiling Fans,Commercial Stand Fan,Industrial Exhaust Fan Julai (Chongqing) ventilation equipment Co.,Ltd , https://www.julaifans.com
O 2 =2FeS+As 2 O 3 ↑
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