Gold cyanide extraction method is the most common and most stable method of gold and silver ore and materials, but there are also leaching time (leaching cycle) long (one week to one year heap leaching, agitation leaching of 24 to 72 hours), organic carbon, antimony, arsenic, copper, zinc and other harmful elements very sensitive, causing a significant reduction of gold, silver leaching rate, the disadvantage substantial increase in production costs, in particular the Act cyanide is highly toxic, damage to the environment is considerable. Therefore, how to improve gold, silver leaching rate, reduce costs, find an alternative non-toxic or highly toxic cyanide toxicity smaller new technology and new technology is an important research topic.
Non-cyanidation leaching agents include thiourea, oxygen, bromine, iodine, ammonia, thiocyanate, calcium polysulfide and the like.
(1) of the Act thiourea under acidic conditions gold dissolution speed, non-toxic, selective than cyanide, is not sensitive to the base metal impurities, in dealing with some gold-bearing materials, such as anode slime, gold uranium acid and sulfuric acid leaching slag and so have some advantages, but high drug consumption, leaching equipment perishable, the lack of effective method for recovering gold from thiourea solution.
In 1997, it was found that sodium sulfite can inhibit the irreversible decomposition of alkaline thiourea to some extent, promote the dissolution of gold, gold dissolution can select rows from the gold-bearing waste; that the sodium silicate is an alkaline thiourea gold extraction efficiency stabilizer.
(2) a halogen and halide salt used in the Act reagent mainly chlorine, bromine, iodine, chloride, iodide, bromide, etc., e.g., chlorine, hypochlorite, chloride method, K reagent, Geobrom3400 , Bio-D reagents and other oxidants. Chlorine leaching process, both as an oxidizing agent, and as a complexing agent to generate AuCl32-, halogen ions (X-) is Au2 + Au + and strong ligand chloride leaching carbon material suitable for processing gold ore containing arsenic, antimony burn slag, re-election of gold concentrate containing arsenic and pyrite gold ores.
Bromide method is to replace one of the most promising cyanide leach gold extraction process, the advantage of cheap, high leaching, leaching speed, non-toxic, non-corrosive, agents can be recycled, the recovery of gold from the pregnant solution convenient. Many foreign research iodide method using iodine - iodide solution than cyanide leaching method can be obtained with high gold leach rates from iodine - iodide direct electrowinning of gold is also possible.
(3) of the Act nitrile using malononitrile (also known as cyanuric acid nitrile), cyanoacetamide and acetonitrile three kinds of nitrile to extract gold. In dealing with carbonaceous gold ores, nitrile cyanide gold leaching rate is much higher than the law. In dealing with oxidized ores and sulfide ores, its gold leaching with cyanide leaching rate as effective, but its high price.
(4) Method i.e. microorganisms capable of biological agents leach gold, which the cellular components of microbial protein, microbial metabolites of amino acids (glycine, histidine, aspartic acid, etc.). Protein and gold to form a complex with a negatively charged, this complex was purified by amino acid groups of the nitrogen atom, form a stable gold complex.
(5) of the Act coal golden reunion is the use of flotation reagents to improve the hydrophobic characteristics of the gold particle surface by the collision of the mixing process, the hydrophobic gold particles into the Aggregates. Contained gold aggregates through cycles, enrichment and ashing, the resulting ash after baking or other means smelting process to be finished gold.
(6) polysulfide Act and the Act uses lime sulfur and lime sulfur leaching of gold and silver produced by the reaction reagents, chelating polysulfide ions S22-, S32-, S42-, S52-, etc., which gold ions strong complexing ability, in a suitable oxidant (such as potassium permanganate, etc.) with the next, or by means of disproportionation polysulfide ions, can effectively dissolve gold and silver.
(7) Other methods Other methods are humic acid method, FM reducing reagent, thiosulfate method.
2015年9月18日星期五
Interview with Executive Vice President of the Chilean National Commission Copper Sergio Hernández
How can "1 + 1" generated "> 2" effect? Although it is not the only answer, but the "win-win cooperation, complementarity and development," but would be a best choice. For China and Chile to carry out investment and trade activities in terms of the same.
http://www.goldcyanide.com/
How can "1 + 1" generated "> 2" effect? Although it is not the only answer, but the "win-win cooperation, complementarity and development," but would be a best choice. For China and Chile to carry out investment and trade activities in terms of the same.
2015, to coincide with the signing of Sino-Chilean FTA occasion of ten years, according to the agreement, starting from January 1 this year, on the basis of free trade agreements on the trading of all Chile's exports to China are zero tariffs. At this point, you can enjoy tariff-free policy before 1611 kinds of goods increased by the 5725 kinds. Avoidance of double customs restrictions between the two countries, trade regime more flexible, and from more closely. In this way, the state furthest apart on two maps forum is "1 + 1" mutual promotion and action, and constantly create "> 2" effect.
Chile is the world's largest copper producer and exporter of copper, while China is the largest consumer of copper and copper importer. According to statistics, China's annual consumption of copper imports 47 percent of the total amount, which has 40% of imports from Chile. Sergio Hernández, executive vice president at the Chilean National Copper Commission opinion, precisely because of such a close relationship between supply and demand, cooperation between the two countries in the field of investment will be just around the corner copper.
Make good use of "China and Chile Week" platform
By 2015, China and Chile established diplomatic relations 45 anniversary usher. To celebrate this important anniversary, the Government of Chile on August 23 - August 28 held a special "China and Chile Week" in Shanghai and Beijing. During the event, the former President of Chile, the Chilean delegation in the Asia-Pacific region, led by Ambassador Extraordinary and Plenipotentiary of Chile Eduardo Frei (Eduardo FREI) about 150 people participated in the multilateral activities. In this delegation, not only on behalf of the Chilean entrepreneurs more than 10 industries, as well as the person in charge from the mining industry, economy, agriculture, engineering, trade and other key sectors of the Chilean government. As executive vice president of the Chilean National Copper Commission, Sergio Hernández this line for Chilean copper enterprises to establish a cooperative relationship with Chinese enterprises spare no effort to publicize.
'' China and Chile Week 'is a good platform, which allows Chinese entrepreneurs and investors a better understanding of the opportunities and advantages of investment in Chile, so as to promote bilateral cooperation in the copper mining enterprises fields. "Sergio Hernández "As a national public service institution, the Chilean National Copper Commission itself does not engage in any mining investment business, its function is to assist the Chilean copper business with Chinese companies to establish or carry out investment cooperation. The 'China and Chile Week', the Commission will Chilean copper to Chinese investors on investment projects and development plans over the next 10 years in Chile's copper industry. "
Copper focus on two areas of cooperation
According to data provided by the Export Promotion Bureau of Chile, in 2014 and Chile bilateral trade amounted to $ 32.671 billion, accounting for 24 percent of Chile's foreign trade volume. During 2002 to 2014, bilateral trade volume of 24% average annual growth rate, Chile's exports to China increased by an average of 25% annually. From China's perspective, in 2014 Chile is China's 24th largest import target country and No. 33 export countries, import and export respectively, accounted for 1.08 percent and 0.56 percent of China's total foreign trade.
However, talking about the situation of Chinese enterprises copper mine in Chile to carry out the investment, Sergio Hernández but somewhat regret. He gestures said:. "'0' Although China is the largest importer of Chilean copper, but due to various reasons, investment cooperation between the two countries in terms of copper but still failed to achieve 'zero' breakthrough, I think, From another perspective also shows that our cooperation with Chinese enterprises in this area has great potential in the future. Chile and China have much in common, is not limited to China is a big consumer of copper and copper mine in Chile is the largest suppliers of this point, China and Chile have strong complementarity. "
Copper exports has always occupied an important position in the Sino-Chilean bilateral trade, the copy of the data from the Chilean National Copper Commission show that in 2013 China imported $ 15.1 billion worth of copper from Chile, accounting for 79 of the country's total exports to China that year %, which accounted for 37.5% of total exports that year of copper; in 2014, Chile's copper production was 5.78 million tons, with exports hit a 7-year high of 5.66 million tons, China is still a superpower copper imports from Chile total imports of nearly 2.2 million tons, equivalent to 38.9 percent of Chile's total copper exports. "Most of Chile's copper exports to China are the original form of copper ore, and smelting in China." Sergio Hernández said, "China has more advanced smelting technology, we hope that the two companies can field in the deep processing of copper to carry out a series of cooperation. At present, including the Chilean Copper Corporation of Chile, including two large copper enterprise in dialogue with Chinese companies, and we expect them to have great new progress. "
In addition, Sergio Hernández also said that open and Technical College is looking forward to cooperation in the field of copper smelting and Chinese research institutions and enterprises, to enhance Chile's copper smelting capacity by training professionals. It is understood that many universities have teaching strengths of Chile and international prestige. Engineering is a relatively mature discipline in Chile, with over 40 years of experience, professional sound education system also makes it received international recognition. Among the most prominent was undoubtedly the mining project, has a world-class level. Sergio Hernández said: "At present, one of the biggest advantages of Chile in the field of engineering is divided into very detailed, each tiny areas have a high level of professional and related technologies, such as earthquake engineering, environmental engineering, solid pipeline transportation , hydrometallurgy and natural surface and underground mining and mine operations, a lot of new technology has also been applied to the project. However, these are not enough. Chile in copper concentrate production and transport still faces enormous challenges, We therefore hope that the excellent copper-producing countries from the introduction of industrial technology, so as to enhance the country's copper concentrate production capacity. "
Chilean copper investment opportunities and challenges
Last September, Chile's Minister of Mines Aurora participated in the International Conference of mineral resources held in Melbourne had said Chilean Mining 2014 - 2025 the amount of investment will reach $ 105 billion. Among them, the copper industry investment will reach $ 81 billion, other mineral projects in gold, silver and iron ore will get $ 23 billion investment. Chile "strategy" recently also announced that the Minister of Mines of Chile and the Chilean National Commission Aurora Williams Copper announced that 2015 ~ 2024 Chile Copper intends to develop 31 projects and 11 other mining projects, the proposed investment were $ 67.035 billion and $ 10.255 billion. If all the projects implemented, to 2024 Chile's copper output will increase by 33% at present. Data over copper project similar to last year, showing that investment in copper mining investment in Chile still occupy an important position in the field.
It is worth noting that the price of copper continued to decline since last year, than in 2011 decreased approximately by about one-third of the peak, which to some extent affected the enthusiasm of investors. Sergio Hernández believes copper prices affected by many factors, including not only the impact of the global economic downturn, the dollar, crude oil and other commodity prices, etc., as well as from China's economic slowdown, demand for smaller, etc. Interaction factors. He admitted that in the next two and half years, copper prices are likely to continue to maintain at a lower level (which does not include the Chilean copper production decline and other factors). "But, from the procurement perspective, the decline in copper prices may well be a good thing." Sergio Hernández also said.
Nevertheless, Sergio Hernández still on Chilean copper investment confidence. He said that Chile has an open, free and stable mining investment environment and high market transparency. In recent years, many countries have chosen to enter Chile to carry out mining investment. Data show that Chile is acceptable in terms of resources mineral foreign capital directly into the more important countries. In order to improve competitiveness, since 2011 Chile has also implemented a series of plans to promote investment and competitiveness, focusing on solving difficulties foreign companies investing in Chile, including energy costs and bureaucratic barriers. In addition, healthy public finances, a sound legal system, stable policy mechanisms and government support has become an important factor in attracting foreign capital. "Although the 2014 Chile exploration spending fell by 22%, less than the world's exploration spending levels, but Chile still has a good investment environment and potential advantages of geological prospecting." Sergio Hernández represented.
In addition, the Chilean government has also taken a series of mature trade policies, designed to successfully combine the Chilean economy and international markets. Today, the Chilean government has been promoting the development of the export industry and the services sector as an important task, in order to attract international investment. "Chile has a very important platform - the relevant provisions of the free trade agreement on services, it can not only provide convenience for the many service companies in Chile, but also that Chilean companies and more than 60 countries, the company established a business relationship escort Escort. "Sergio Hernández added.
Sergio Hernández said: "Although the Chilean mining industry is facing many challenges, such as water and energy, ecological communities, environmental norms standards, but the Chilean mining industry is trying to build a strong innovation ecosystem, the industry association, suppliers, research closely integrated with the service and the country, through the effective use of renewable resources, to strengthen cooperation with domestic and foreign academic and research institutions, and increase investment in human capital and the development of advanced mining systems, to more effectively address the challenges facing the mining industry in order to attract more investors. Therefore, we are also very welcome and look forward to Chinese enterprises to invest in Chile to carry out mine! "
2015年9月14日星期一
Application and Maintenance of the Thickener in Mineral Processing Plant
Thickener belongs to dehydration equipment in Mineral Processing Plant, commonly used for the thickening of ore concentrate and the dewatering of the tailings before filtration, as well as the thickening and purification of liquid containing solid particles in coal industry, chemical industry, building materials ,and water source &sewage treatment industry.
In the processing of dewatering tailings,thickening is mainly used to make use of the recycling water and to store the tailings in the tailings dam.Otherwise, to improve the operating process such as the thicker slurry is needed when it is too thin, so thickener is one of the necessary dewatering machine among the process of miming solutions.
For now, mechanical discharge thickener, also named rake-type thickener, is most widely used which can be operated continuously, and there are three types concluding center -transmission thickener, peripheral roller transmission thickener and multilayer thickener,and the peripheral roller transmission one can also be divided into two types such as rack peripheral transmission and roller peripheral transmission.
Though thickener is easy to manage when daily operating, it is quite cardiac to the whole mining plant, and if anything wrong happens to thickener,the whole plant has to stop operating. There are several points suggested by the tailings dry stacking team of the Mining Machinery Co.,LTD that needed to pay attention to when operate the thickener.
Firstly, several attention points when starting and parking the thickener
The motor should be started before the ore fed in order to guarantee the normal work of the thickener, and the ore should be fed after the thickener has already running up. When special circumstances happens, thickener must be stop then the ore
Should stop feed,then quicky lift the rake or increase the amount of the discharge of ore, to avoid the scraper not being sated on the slurry pulp, thus to guarantee the continuity and uniformity of the feed and discharge (the discharge of the thickening )of the ore.
Secondly, some attention aspects when daily operating the thickener
At the same time,to meet the demand of the production, the feed concentration and the concentration of the thickening as well as the quality of the overflow water should be checked at daily works. In actual operation,the concentration of the thickening can be changed by controlling the pace of the feed ore, when adjust the discharge concentration, attention must be paid to prevent the increase of the solid in the overflow process to ensure the overflow water can meets the requirements.
Thickener means a lot to the mining plant, thus we should have a overwhelming understanding to the aspects that affect the production capacity of the thickener.the capacity of the thickener means thickening area to processing tons of day and night, there are several factors that affects the productivity.
Firstly, the density of the feed ore and the discharge ore; secondly,the composition of the particle size; thirdly,the viscosity of the foam; fourthly,the existence of the pharmacy and electrolyte; fifthly,the temperature of the slurry; sixthly, the value of the concentration material.
Except those factors, the most important factor is the mud which is the most difficult material to slime. There are two sources of the mud: one kind is formed in the process of the ore shattering,called row mud, the other one is produced in the grinding process that is being gringding too much,called producing mud.Due to the fine particle size of the ore mud, so increase the mineral surface area and the moisture content which depending on wetting and capilary phenomenon,for the micro colloidal particle of 0.1-0.001mm, the the molecular forces and electrostalic repulsion between same charged particles caused no precipitation due to the tendency of their own settlement.Therefore,the fine mud is the most difficult material to slime of the precipitation process.In ore dressing plant, one way is to add electrolyte, or to add colloidal surfactant( usually by adding water glass and soda) thus to adjust the solid and liquid ratio of the slurry pulp or to heat the slurry pulp to accelerate the subsidence particle dispersed pulp.
With the influence of the national policy in recent years,tailings dry stacking is becoming more and more popular,thus increase the demand for the thickener, therefore through the introduction above to know more about the thickener is necessary.
In the processing of dewatering tailings,thickening is mainly used to make use of the recycling water and to store the tailings in the tailings dam.Otherwise, to improve the operating process such as the thicker slurry is needed when it is too thin, so thickener is one of the necessary dewatering machine among the process of miming solutions.
For now, mechanical discharge thickener, also named rake-type thickener, is most widely used which can be operated continuously, and there are three types concluding center -transmission thickener, peripheral roller transmission thickener and multilayer thickener,and the peripheral roller transmission one can also be divided into two types such as rack peripheral transmission and roller peripheral transmission.
Though thickener is easy to manage when daily operating, it is quite cardiac to the whole mining plant, and if anything wrong happens to thickener,the whole plant has to stop operating. There are several points suggested by the tailings dry stacking team of the Mining Machinery Co.,LTD that needed to pay attention to when operate the thickener.
Firstly, several attention points when starting and parking the thickener
The motor should be started before the ore fed in order to guarantee the normal work of the thickener, and the ore should be fed after the thickener has already running up. When special circumstances happens, thickener must be stop then the ore
Should stop feed,then quicky lift the rake or increase the amount of the discharge of ore, to avoid the scraper not being sated on the slurry pulp, thus to guarantee the continuity and uniformity of the feed and discharge (the discharge of the thickening )of the ore.
Secondly, some attention aspects when daily operating the thickener
At the same time,to meet the demand of the production, the feed concentration and the concentration of the thickening as well as the quality of the overflow water should be checked at daily works. In actual operation,the concentration of the thickening can be changed by controlling the pace of the feed ore, when adjust the discharge concentration, attention must be paid to prevent the increase of the solid in the overflow process to ensure the overflow water can meets the requirements.
Thickener means a lot to the mining plant, thus we should have a overwhelming understanding to the aspects that affect the production capacity of the thickener.the capacity of the thickener means thickening area to processing tons of day and night, there are several factors that affects the productivity.
Firstly, the density of the feed ore and the discharge ore; secondly,the composition of the particle size; thirdly,the viscosity of the foam; fourthly,the existence of the pharmacy and electrolyte; fifthly,the temperature of the slurry; sixthly, the value of the concentration material.
Except those factors, the most important factor is the mud which is the most difficult material to slime. There are two sources of the mud: one kind is formed in the process of the ore shattering,called row mud, the other one is produced in the grinding process that is being gringding too much,called producing mud.Due to the fine particle size of the ore mud, so increase the mineral surface area and the moisture content which depending on wetting and capilary phenomenon,for the micro colloidal particle of 0.1-0.001mm, the the molecular forces and electrostalic repulsion between same charged particles caused no precipitation due to the tendency of their own settlement.Therefore,the fine mud is the most difficult material to slime of the precipitation process.In ore dressing plant, one way is to add electrolyte, or to add colloidal surfactant( usually by adding water glass and soda) thus to adjust the solid and liquid ratio of the slurry pulp or to heat the slurry pulp to accelerate the subsidence particle dispersed pulp.
With the influence of the national policy in recent years,tailings dry stacking is becoming more and more popular,thus increase the demand for the thickener, therefore through the introduction above to know more about the thickener is necessary.
2015年9月13日星期日
Gold cyanide processing gold extraction method
Gold cyanide processing gold extraction method
Gold cyanide processing gold extraction method, the basic principle of gold cyanidation method, gold cyanide leaching six factors, methods to extract gold from cyanide leaching solution List
Cyanide gold extraction is one of the main methods to extract gold from gold ore. Cyanide to explain the mechanism of gold dissolution is not the same, most of that in the case of gold cyanide solution at the presence of oxygen to generate a gold complex can be dissolved. The basic reaction is:
4Au + 8KCN + 2H2O + O2 → 4KAu (CN) 2 + 4KOH
Generally considered the gold is dissolved cyanide occurs in two steps:
2Au + 4KCN + O2 + 2H2O → 2Au (CN) 2 + H2O + 2KOH
2Au + 4KCN + H2O2 → 2KAu (CN) 2 + 2KOH
Surface gold in cyanide solution to dissolve gradually from outside to inside. The oxygen concentration in the solution with the gold dissolution speed.
Factors cyanide gold leaching rate when there are: the concentration of cyanide and oxygen, pH value of the pulp, the raw material properties of gold minerals, leaching temperature, slime content, pulp density and leach time.
Leaching cyanide concentration is generally 0.03% to 0.08% with increasing the dissolution rate of gold cyanide concentration was straight up to the maximum. Then rise slowly, when the cyanide concentration of 0.15%, the unrelated gold dissolution rate and cyanide concentration, or even decline (due to cyanide hydrolysis).
Gold dissolution rate increased with oxygen concentration increases, the use of oxygen-rich solution can be enhanced or high-pressure inflatable cyanide to dissolve gold.
Ability to dissolve gold and silver cyanide reagent is: ammonium cyanide> cyanide calcium> sodium> potassium cyanide. Potassium cyanide most expensive, most currently used sodium cyanide, cyanide consumption depends on the nature of the material and operational factors, often 20 to 200 times the theoretical amount.
Material properties affect the leaching rate of gold. Although cyanidation gold extraction is the main method, but some gold-bearing mineral raw materials should not be used directly cyanidation process, if the ores of copper, arsenic, antimony, tin, sulfur, phosphorus, magnetite, marcasite, etc. will greatly increase cyanide consumption or consumption of pulp in the oxygen content is high component. Lower gold extraction rate, high carbon-containing ore, gold has been dissolved carbon will absorb the loss and with the tailings. Pre-roasting or flotation methods on harmful impurities can be removed.
Hydrolysis of cyanide is: KCN + H2O ← → KOH + HCN ↑, therefore volatile toxic HCN; lime cyanide hydrolysis weakened the reactor to the left direction, reduce chemical loss of cyanide. Lime and acids as well as the role of the pulp and precipitation of harmful ions, and the dry dissolve gold at the best conditions, commonly used as a protective lime base. Lime added in an amount to make the pulp pH value of 11 to 12 is appropriate, when the pulp pH value is too high for gold dissolution disadvantage.
Gold particles size mainly affects cyanide time, coarse gold (> 74 microns) was dissolved slower speed. Therefore, before using cyanide amalgamation, re-election or pre-flotation recovery of coarse gold it is reasonable to. In the grinding process, to fine gold particles fully monomer dissociation is still improving gold leaching rate of more to factor.
When the content of cyanide sludge and slurry concentration component directly affects the rate of diffusion. Pulp concentration should be less than 30 to 33%. Pulp sludge concentration for a long time should be less than 22 to 25 percent, but under the concentration should be too low, otherwise increase cyanide consumption.
Cyanidation time depends on material properties, cyanide and cyanide way conditions. Usually cyanide leaching stirring often more than 24 hours, sometimes for more than 40 hours, we need 72 hours when the hoof and gold cyanide, cyanide leaching percolation takes more than five days.
The method of extracting gold from cyanide leaching solution List
Mention gold from cyanide leach solution methods more, if CIP (CIP), carbon leaching (CIC), magnetic carbon method (MCIP) or resin exchange process can go solid-liquid separation operations. Usually cyanide slurry solid-liquid separation to get your solution (gold solution). From your liquid gold extraction methods are zinc substitution precipitation, activated carbon adsorption, ion exchange resin adsorption method or electrolytic deposition method. Metal zinc wire or zinc powder from the solution by precipitation of gold is a commonly used method of substitution. Before entering your fluid replacement precipitate jobs clarified to remove the sludge and suspended solids, because these impurities to precipitate the next replacement job is harmful.
The basic principle is that gold precipitated zinc substitution: in your liquid zinc will dissolve in the solution leaving the gold precipitates out your liquid ion Au (CN) 2- and Zn role reaction is usually written as:
2KAu (CN) 2 + 3Zn + 4KCN + 2H20 ← → 2Au ↓ + 2K2Zn (CN) 4 + K2Zn02 + H2 ↑
There must be sufficient cyanide and alkali solution when the zinc substitution, or else gold dissolved oxygen in the solution will have been precipitated leaving the zinc oxide powder was redissolved into Zn (OH) 2 precipitation:
Zn + 1 / 2O2 + H2O ← → Zn (OH) 2 ↓
There solution K2Zn (CN) 4 will be broken down into cyanide zinc precipitate insoluble:
K2Zn (CN) 4 + Zn (OH) 4 ← → 2Zn (CN) 2 ↓ + 2KOH
These zinc hydroxide and zinc cyanide as a white precipitate will be housed in a thin film formed on the surface of metallic zinc, zinc substitution effect and prevented from expensive solution for gold. The conventional settling tank by adding a small amount of lead acetate and lead nitrate and better contribute to the dissolution of zinc replacement precipitate gold. Expensive solution containing soluble sulfide, mercury, copper and other impurities are replaced hinder gold precipitation.
Gold cyanide processing gold extraction method, the basic principle of gold cyanidation method, gold cyanide leaching six factors, methods to extract gold from cyanide leaching solution List
Cyanide gold extraction is one of the main methods to extract gold from gold ore. Cyanide to explain the mechanism of gold dissolution is not the same, most of that in the case of gold cyanide solution at the presence of oxygen to generate a gold complex can be dissolved. The basic reaction is:
4Au + 8KCN + 2H2O + O2 → 4KAu (CN) 2 + 4KOH
Generally considered the gold is dissolved cyanide occurs in two steps:
2Au + 4KCN + O2 + 2H2O → 2Au (CN) 2 + H2O + 2KOH
2Au + 4KCN + H2O2 → 2KAu (CN) 2 + 2KOH
Surface gold in cyanide solution to dissolve gradually from outside to inside. The oxygen concentration in the solution with the gold dissolution speed.
Factors cyanide gold leaching rate when there are: the concentration of cyanide and oxygen, pH value of the pulp, the raw material properties of gold minerals, leaching temperature, slime content, pulp density and leach time.
Leaching cyanide concentration is generally 0.03% to 0.08% with increasing the dissolution rate of gold cyanide concentration was straight up to the maximum. Then rise slowly, when the cyanide concentration of 0.15%, the unrelated gold dissolution rate and cyanide concentration, or even decline (due to cyanide hydrolysis).
Gold dissolution rate increased with oxygen concentration increases, the use of oxygen-rich solution can be enhanced or high-pressure inflatable cyanide to dissolve gold.
Ability to dissolve gold and silver cyanide reagent is: ammonium cyanide> cyanide calcium> sodium> potassium cyanide. Potassium cyanide most expensive, most currently used sodium cyanide, cyanide consumption depends on the nature of the material and operational factors, often 20 to 200 times the theoretical amount.
Material properties affect the leaching rate of gold. Although cyanidation gold extraction is the main method, but some gold-bearing mineral raw materials should not be used directly cyanidation process, if the ores of copper, arsenic, antimony, tin, sulfur, phosphorus, magnetite, marcasite, etc. will greatly increase cyanide consumption or consumption of pulp in the oxygen content is high component. Lower gold extraction rate, high carbon-containing ore, gold has been dissolved carbon will absorb the loss and with the tailings. Pre-roasting or flotation methods on harmful impurities can be removed.
Hydrolysis of cyanide is: KCN + H2O ← → KOH + HCN ↑, therefore volatile toxic HCN; lime cyanide hydrolysis weakened the reactor to the left direction, reduce chemical loss of cyanide. Lime and acids as well as the role of the pulp and precipitation of harmful ions, and the dry dissolve gold at the best conditions, commonly used as a protective lime base. Lime added in an amount to make the pulp pH value of 11 to 12 is appropriate, when the pulp pH value is too high for gold dissolution disadvantage.
Gold particles size mainly affects cyanide time, coarse gold (> 74 microns) was dissolved slower speed. Therefore, before using cyanide amalgamation, re-election or pre-flotation recovery of coarse gold it is reasonable to. In the grinding process, to fine gold particles fully monomer dissociation is still improving gold leaching rate of more to factor.
When the content of cyanide sludge and slurry concentration component directly affects the rate of diffusion. Pulp concentration should be less than 30 to 33%. Pulp sludge concentration for a long time should be less than 22 to 25 percent, but under the concentration should be too low, otherwise increase cyanide consumption.
Cyanidation time depends on material properties, cyanide and cyanide way conditions. Usually cyanide leaching stirring often more than 24 hours, sometimes for more than 40 hours, we need 72 hours when the hoof and gold cyanide, cyanide leaching percolation takes more than five days.
The method of extracting gold from cyanide leaching solution List
Mention gold from cyanide leach solution methods more, if CIP (CIP), carbon leaching (CIC), magnetic carbon method (MCIP) or resin exchange process can go solid-liquid separation operations. Usually cyanide slurry solid-liquid separation to get your solution (gold solution). From your liquid gold extraction methods are zinc substitution precipitation, activated carbon adsorption, ion exchange resin adsorption method or electrolytic deposition method. Metal zinc wire or zinc powder from the solution by precipitation of gold is a commonly used method of substitution. Before entering your fluid replacement precipitate jobs clarified to remove the sludge and suspended solids, because these impurities to precipitate the next replacement job is harmful.
The basic principle is that gold precipitated zinc substitution: in your liquid zinc will dissolve in the solution leaving the gold precipitates out your liquid ion Au (CN) 2- and Zn role reaction is usually written as:
2KAu (CN) 2 + 3Zn + 4KCN + 2H20 ← → 2Au ↓ + 2K2Zn (CN) 4 + K2Zn02 + H2 ↑
There must be sufficient cyanide and alkali solution when the zinc substitution, or else gold dissolved oxygen in the solution will have been precipitated leaving the zinc oxide powder was redissolved into Zn (OH) 2 precipitation:
Zn + 1 / 2O2 + H2O ← → Zn (OH) 2 ↓
There solution K2Zn (CN) 4 will be broken down into cyanide zinc precipitate insoluble:
K2Zn (CN) 4 + Zn (OH) 4 ← → 2Zn (CN) 2 ↓ + 2KOH
These zinc hydroxide and zinc cyanide as a white precipitate will be housed in a thin film formed on the surface of metallic zinc, zinc substitution effect and prevented from expensive solution for gold. The conventional settling tank by adding a small amount of lead acetate and lead nitrate and better contribute to the dissolution of zinc replacement precipitate gold. Expensive solution containing soluble sulfide, mercury, copper and other impurities are replaced hinder gold precipitation.
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