It has also been used in the production and modification of synthetic resins. The extraction of gold and silver from chalcopyrite concentrates has been investigated. A method is provided for recovering gold and silver from precious metal bearing materials including ores, leaching residues, flue dust, electronic scrap, jewelry scrap, etc. Chemical speciation the chemical speciation diagrams are constructed to show the relation of the different chemical species thiourea and gold thiourea either as a function of. Typical pregnant thiourea leach solution analysis 6 6. Precious metal leaching was attempted from received copper concentrates as well as preoxidised concentrates. Leaching of silver from solid waste using ultrasound assisted thiourea method article pdf available in ultrasonics sonochemistry 123. In the method, the gold and silver are extracted from the precious metal bearing materials with a thiourea solution to form a thiourea leach, and the thiourea leach is. The thiourea process of gold and silver extraction from ores, concentrates or secondary raw materials con sists of gold and silver leaching into the thiourea solution and the consequent precipitation of these metals from the solu tion. In the presence of sodium sulphite, the effective concentration of thiourea is increased and the dissolution rate of gold in thiourea solution is greatly increased. Sep 01, 2000 the use of thiourea as an alternative nonpolluting reagent for gold leaching is very well known. Alternative lixiviants to cyanide for leaching gold ores 515 have possible applications in treating silicate ores if only small amounts of high gold sul.
Solubilizing the silver and gold with an acidified thiourea leach solution and then recovering the gold and silver. Therefore, a method for leaching or dissolving gold from ores or precious. Huiatt 2 abstract the bureau of mines investigated a hydrometallurgical procedure to re cover gold, silver, and byproduct lead from a complex leadzinc sulfide ore. The leaching of gold, silver and their alloys in alkaline. This waste is products of amalgamation and cyaniding processes. Leaching process involves time consuming stages to reach the total metal dissolution.
One can rough grind to 40 mesh or even 20 mesh and run several cls 2 tests on 2 pounds or one ounce of ore see chapter 7 for test instructions. An economic assessment of thiourea leaching was compared with conventional cyanidation. Potentialapplications ofthiourea in the processingofgold. Thiourea was used to leach gold from ore containing 0. For the roasted gold concentrate, the dissolution of gold was 94. The thiourea leaching of gold and silver from the gold bearing silicate ore of the hishikari mine kagoshima, japan was studied.
Recovery of silver, gold, and lead from a complex sulfide ore. Gold extraction was 89% and thiourea consumption was 3. The present communication deals with the leaching of gold and silver from the printed circuit boards pcbs of waste mobile phones using an effective and less hazardous system, i. Barrick thiosulfate leaching of double refractory ore. Thiourea leaching of gold concentrates and recovery of gold. Recovery of silver, gold, and lead from a complex sulfide.
Gold electrowinning from thiourea solutions was studied by linear sweep voltammetry and chronopotentiometry. Us4778519a recovery of precious metals from a thiourea. Laboratory testing of this reagent has indicated that a thiourea process for gold extraction has. Studies on extraction of refractory gold and silver. The effects of initial concentrations of ferric, thiourea tu and thiocyanate as well as temperature and ph on gold leaching rates were studied. Link with starting formulation testedphoto gold dissolving in 3 days.
According to the method, under an alkaline condition, thiourea is taken as a gold leaching reagent, sodium hexametaphosphate or trisodium phosphate is taken as a stabilizing agent, calcium peroxide is taken as an oxidizing agent, edta ethylene diamine tetraacetic acid is taken as a. Influence of thiourea concentration on gold dissolution. Reduction of thiourea consumption in gold extraction by acid. One can rough grind to 40 mesh or even 20 mesh and run several cls 2 tests on 2 pounds or one ounce of ore see chapter 7. Cn103276206a method for leaching gold in alkaline thiourea. Auag noble metal wastes represent a wide range of waste types and forms with various ballast elements and components. The method for the recovery of gold from its flotation concentrate using acidic thiourea leaching followed by adsorption on an organosilicon polymer pstm3c was discussed in the present study. A lixiviant for gold and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. The extraction of gold from bioleached pyrite using novel. The leaching of gold in thiourea thiocyanate solutions has been studied by the rotatingdisc technique using ferric sulfate as oxidant. But with this method i end up with a lot of hcl, which i reuserecycle in a variety of ways.
The apparent activation energy of the extraction of gold and silver was smaller than that of the reaction rate of thiourea consumption by ferric iron. How know a good chemical mixture with thiourea, to get good results in leaching gold. No acid consumption was observed during leaching at ph 3. An innovative thiourea gold leaching process sciencedirect. Bioleaching, chlorination, aqua regia, bromine, thiocyanate, thiosulfate and thiourea leaching. Gold recovery from electronic waste by pressure oxidation. There is currently much interest in how extraction of gold and silver from ores with acidic thiourea solution compares with extraction using alkaline cyanide solution. A leaching agent for gold leaching and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. The most common uses for thiourea have been for the production of thiourea dioxide 30%, in leaching of gold and silver ores 25%, in diazo papers blueprint papers 15%, and as a catalyst in the synthesis of fumaric acid 10% iarc 2001. The use of thiourea scnh 2 2 tu has been studied extensively, mainly because it is not harmful to the environment, nontoxic to human beings, and the dissolution of gold in thiourea solutions is much faster than in cyanide solutions. The aim of this experimental work was devoted to the preliminary evaluation of the feasibility of thiourea leaching for the extraction of gold from a domestic goldbearing ore 4 gt au, at laboratory scale.
Leaching gold silver ores with sodium cyanide and thiourea under comparable conditions by j. A method for leaching or dissolving gold from ores or. The effects of some associated minerals on thiosulfate gold leaching were studied through thermodynamic analysis and leaching experiments on composite ore samples containing various minerals and a reference silicate gold ore. In the leaching test on the reference gold ore, about 93% of gold was extracted within 3. Pdf thiourea leaching gold and silver from the printed. According to the label on the consumer product, the liquid silver cleaning product tarnx contains thiourea, a detergent, and sulfamic acid. Another common application for use of thiourea is a common sulfur source for making semiconductor cadmium sulfide nanoparticle. The thiourea leaching of gold and silver from the goldbearing silicate ore of the hishikari mine kagoshima, japan was studied. Pdf leaching of gold and silver from crushed auag wastes. Gold recovery from nonmetallic secondary raw materials by leaching with thiourea and adsorption on ion exchangers. Dissolution behavior of gold in alkaline media using thiourea. The application of novel thiourea leaching technologies to the extraction of gold from a bioleached pyrite concentrate was investigated. Thiourea is easily oxidized to formamidine disulphide, which reduces the leaching efficiency and increases reagent consumption. The gold is recovered from this solution by electrowinning, zinc precipitation or refining technology such as the mintek minataur process.
Leaching goldsilver ores with sodium cyanide and thiourea under comparable conditions by j. Alternative lixiviants to cyanide for leaching gold ores. In view of the recent interest in noncyanide leachants for gold and silver, one such alternative reagent, namely thiourea, has been employed in the present work. Agitation leaching tests were performed by the bureau of mines on 14 precious metal ores using sodium cyanide nacn and thiourea nh22cs as extractants. The parameters studied were acid pretreatment, leaching time, ph, thiourea concentration and the oxidizing agents used. However, the processes of gold recovering from thiourea solutions have received little attention, particularly the electrowinning process. The process design of gold leaching and carboninpulp circuits. Thioureathiocyanate leaching system for gold request pdf although both thiourea and thiocyanate have been studied to leach gold from pure gold disk yang et al. The study had allowed identification of the effect of thiourea, oxidizer and acid concentration, leaching time, temperature and pulp density on gold. Recovery of silver, gold, and lead from a complex sulfide ore using ferric chloride, thiourea, and brine leach solutions by r. The interac tion of leach variables with thiourea consumption and gold extraction was established. Request pdf thioureathiocyanate leaching system for gold the leaching of gold in thioureathiocyanate solutions has been studied by the rotatingdisc technique using ferric sulfate as.
Link with starting formulation testedphoto golddissolving in 3 days. Pdf leaching of silver from solid waste using ultrasound. The use of thiourea as an alternative nonpolluting reagent for gold leaching is very well known. Determination of gold in solutions of thiourea analytical. Thiourea leaching of a coppergold ore using statistical. Bureau of mines on 14 precious metal ores using sodium cyanide nacn and thiourea nh22cs as extractants. Elsevier hydrometallurgy 47 1998 189203 hydrometallurgy thiourea leaching of a copper gold ore using statistical design pierre lacostebouchet a, guy deschnes b, edward ghali c, a agnico eagle, cadillac, quebec, canada b canmet, ottawa, ontario, canada c laval university, quebec city, quebec, canada received 16 september 1996. L amps shire abstract there is currently mch interest in how extraction of gold and silver from ores with acidic thiourea solution compares with extraction using alkaline cyanide solution. In this regard, leaching studies focus on the use of strong acids hcl, hno 3, h 2 so 4 and oxidative reagents cyanide, thiourea, halide, nitrate, iodide, and thiosulfates 35. For this propose, the gold leaching reagents are described and discussed in terms of their environmental and economical points of view. In tadzhikistan the volume of goldcontaining waste converted to gold is 18 tons. Thiourea is a reducing and complexing agent and can be used for the processing of gold and silver. The influence of thiourea concentration on the leaching of gold was investigated by varying csnh 2 2 in the range from 10 to 100 gkg. I have been using hclcl to remove the gold then dropping it with smb.
L amps shire abstract there is currently mch interest in how extraction of gold and silver from ores with acidic thiourea solution compares with extraction using. Chemical speciation the chemical speciation diagrams are constructed to show the relation of the different chemical species thiourea and goldthiourea either as. The invention discloses a method for leaching gold in an alkaline thiourea system efficiently and stably. In order to determine the maximum size to which an ore may be ground for cls leaching, thiourea leaching, or any kind of leaching, a number of tests should be run. Pdf an innovative thiourea gold leaching process stefano. Gold recovery from its flotation concentrate using acidic. Gold electrowinning from thiourea solutions, minerals. Atthisstage, itappears that thegoldithiourea ionlaucsnh22. Study on mechanism of gold leaching by thiourea in the. Thiourea bioleaching for gold recycling from ewaste. Thiosulphate leaching is a process that removes gold from gold bearing ores without the use of cyanide. Use of thiourea leaching during goldcontaining dump.