Thiourea was used to leach gold from ore containing 0. Leaching of silver from solid waste using ultrasound assisted thiourea method article pdf available in ultrasonics sonochemistry 123. The best gold recovery results were obtained with ferric sulphate as the oxidizing agent. Lead metal was recovered from the brine solution in an electrolytic cell with. Jul 01, 1990 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. Thiourea, csnnh22 is an organic compound which dissolves easily i acid solution in a stable molecular form. Gold leaching is the key stage in process of gold mining. Sep 01, 2000 the use of thiourea as an alternative nonpolluting reagent for gold leaching is very well known. Thiourea bioleaching for gold recycling from ewaste. The behaviour of gold was examined with electrochemical tests and weight loss measurements a using.
Thiourea leaching of a coppergold ore using statistical. Us2872482a us571651a us57165156a us2872482a us 2872482 a us2872482 a us 2872482a us 571651 a us571651 a us 571651a us 57165156 a us57165156 a us 57165156a us 2872482 a us2872482 a us 2872482a authority us united states prior art keywords thiourea reaction ozone thiourea dioxide potential prior art date 19550316 legal status the legal status is an assumption. An additional argument for thiourea or thiosulphate are their high leaching rates that can reach 250mgcm2 per. Laboratory testing of this reagent has indicated that a thiourea process for gold extraction has. In this work the dissolutive behavior of gold in alkaline medium using thiourea tu, under different variables, was studied in a theoretical and experimental way, in order to determine the conditions under which it is feasible to dissolve gold in thiourea alkaline medium. For this propose, the gold leaching reagents are described and discussed in terms of their environmental and economical points of view.
Pdf leaching of ovacik gold ore with cyanide, thiourea and. Recently, there has been mch interest in the min ing and metallurgical processing indus tries in thiourea as an extractant for gold and silver, 614. Thiourea and sulphuric acid consumption were both 5 gkg. The purpose of hydrochloric leaching is to provide the oxidant required for the next stage of thiourea leaching and to expose the surfaces of the gold particles for further processing. When leaching at higher thiourea concentration, namely 100 kgt, the rate of gold extraction is high. Thiourea leaching has been reported to be affected to a much lesser degree by the presence of some of these cyanidation inhibitors. Recovery of silver, gold, and lead from a complex sulfide. N2 the hydrometallurgical application of thiourea in processing precious metal ores and concentrates has reached the development stage. In the main thiosulfatecopperammonia system, the presence.
Another common application for use of thiourea is a common sulfur source for making semiconductor cadmium sulfide nanoparticle. Cyanide extracts gold in an alkaline medium, and although no oxidant other than air from agitation is generally applied, addition of an oxidant may be beneficial 4. For the roasted gold concentrate, the dissolution of gold was 94. Thiourea leaching of goldbearing mine wastes from the. The dissolution of gold in thiourea solutions was reported for the first time in 1941, and it was continued in 1960 1. Pdf thiourea leaching gold and silver from the printed. Thiourea leaching of a coppergold ore using statistical design thiourea leaching of a coppergold ore using statistical design lacostebouchet, pierre. Gold electrowinning from thiourea solutions gold electrowinning from thiourea solutions juarez, c.
Chemical speciation the chemical speciation diagrams are constructed to show the relation of the different chemical species thiourea and goldthiourea either as. Dissolution behavior of gold in alkaline media using thiourea. Bioleaching, chlorination, aqua regia, bromine, thiocyanate, thiosulfate and thiourea leaching. Heap leaching is a tried and tested mining technique enabling the processing of different kinds of ores which could not otherwise be exploited under viable economic conditions. L amps shire abstract there is currently mch interest in how extraction of gold and silver from ores with acidic. Alternates to gold recovery by cyanide leaching 123pregnant solution. Request pdf thiourea bioleaching for gold recycling from ewaste recycling and reuse of electronic wastes ewastes are becoming an increasingly critical strategy for securing metal resources. Leaching goldsilver ores with sodium cyanide and thiourea under comparable conditions by j. 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. He suggested that the bromine process had the potentialto be a good and economic alternate to the cyanide leaching. Potentialapplications ofthiourea processingofgold in the byt. This paper introduces principle of leaching gold with acidic thiourea and main recovery methods. Recovery of silver, gold, and lead from a complex sulfide ore. To reduce the ph, thiourea leaching should be done in acidic medium so 30%sulfuric acid is used. Thioureathiocyanate leaching system for gold request pdf.
Pretreatment by acid washing is recommended for improved gold leaching and lower thiourea consumption. When leaching proceeds further the dissolution of gold increases to about 87% au. The aim of this paper is to study leaching of gold with cyanide replacing alternatives such as ammonium thiosulfate, chloridehypochlorite, thiourea and thiocyanate to provide new cases for the tool. Investigate of effective factors on extraction of silver from. Nowadays the most popular industrial processes include cyanide, thiourea, and thiosulfate leaching methods. It has been reported that gold dissolves more efficiently with thiourea in acid than in alkaline solution.
There are a few wellreputed leaching methods using a variety of different reagents. I have been using hclcl to remove the gold then dropping it with smb. Leaching goldsilver ores with sodium cyanide and thiourea. It has also been used in the production and modification of synthetic resins. No acid consumption was observed during leaching at ph 3. However, the processes of gold recovering from thiourea solutions have received little attention, particularly the electrowinning process.
The parameters studied were acid pretreatment, leaching time, ph, thiourea concentration and the oxidizing agents used. The benefit of pionera biopolymer is also observed in the merrill crowe process. According to the label on the consumer product, the liquid silver cleaning product tarnx contains thiourea, a detergent, and sulfamic acid. Pdf an innovative thiourea gold leaching process stefano. 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.
Thiourea leachingthiourea is another reagent capable of extracting gold and is less toxic thancyanide 4,6. Iiioxalatethiosulfatethiourea for gold leaching has also been reported 36. And today, over 115 years later, most of the worlds gold is recovered with cyanide playing a large part in the beneficiation of the yellow precious metal. The use of cyanide for the extraction of gold from ores and concentrates is the predominant treatment method for primary recovery of this metal. The redox potential of gold i and silveri thiourea complexes in acidic thiourea solutions are 0. Pdf gold leaching by use of an n,n disubstituted thiourea. Gold leaching leaching reagents applications home pionera. This is especially relevant in the cilcip circuits used in gold processing. Gold cyanide solution leaching gold with cyanide since the 1890s, cyanide has been used to recover gold from gold bearing ores. Potentialapplications ofthiourea in the processingofgold. Figures 16 clearly show the complex behaviour of thiosulfate leaching of gold from. The effects of initial concentrations of ferric, thiourea.
It is the most commonly used leaching process for gold extraction. Gold electrowinning from thiourea solutions, minerals. Alternative lixiviants to cyanide for leaching gold ores. Gold electrowinning from thiourea solutions was studied by linear sweep voltammetry and chronopotentiometry. At first, because the highest percentage of minerals in samples contain carbonate minerals so a heating stage up to 500. The process design of gold leaching and carboninpulp. In the presence of sodium sulphite, the effective concentration of thiourea is increased and the dissolution rate. Terminology cyanide is hydrocyanic acid, or any of its salts or derivatives leaching is a widely used extractive metallurgy technique which converts metals into soluble salts in aqueous media.
The role of ligands and oxidants in thiosulfate leaching. 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. The study has permitted identification of the influence of temperature, leaching agent concentration, pulp density and leaching time on the gold dissolution. Link with starting formulation testedphoto golddissolving in 3 days. Investigate of effective factors on extraction of silver. Oct 18, 1988 the main unit operations in a thiourea leaching method are 1 thiourea leaching by agitation, dump, or heap leaching, 2 recovery of dissolved gold and silver on activated carbon, 3 carbon elution, and 4 recovery of gold and silver from the elution solutions. Report of investigations 9022 recovery of silver, gold, and lead from a complex sulfide ore using ferric chloride, thiourea, and brine leach solutions.
The main unit operations in a thiourea leaching method are 1 thiourea leaching by agitation, dump, or heap leaching, 2 recovery of dissolved gold and silver on activated carbon, 3 carbon elution, and 4 recovery of gold and silver from the elution solutions. Agitation leaching tests were performed by the bureau of mines on 14 precious metal ores using sodium cyanide nacn and thiourea nh22cs as extractants. Bureau of mines on 14 precious metal ores using sodium cyanide nacn and thiourea nh22cs as extractants. Various trials have shown the potential of pionera biopolymer to increase metal recovery in leaching circuits.
Cementation of dissolved gold from the leaching solution is performed by pulverised zinc merrillcrowe process. Since the initial report of thiourea as a complexing reagent for gold leaching, considerable research has been directed toward the use of thiourea as an alternative to cyanide for gold extraction from different auriferous mineral resources. The addition of small concentrations of thiourea in thiosulfate and thiocyanate systems has been shown to enhance the anodic oxidation of gold, as discussed in other sections. Other uses of thiourea are as a photographic toning agent, in hair preparations, as.
After grinding and roasting of the ore, and pre leaching of copper,gold can be leached out nearly to 100 % at the following conditions. The dissolution of gold by cyanide iy expressed by with gold solubilized as an anionic complex. Gold cyanidation also known as the cyanide process or the macarthurforrest process is a hydrometallurgical technique for extracting gold from lowgrade ore by converting the gold to a watersoluble coordination complex. A method for leaching or dissolving gold from ores or. Thiourea leaching of gold concentrates and recovery of. A lixiviant for gold and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. Pdf a novel reagent for gold leaching was synthesized and the leaching conditions investigated. Modern day heap leaching, which has a relatively low level of energy consumption, is for example. In addition, it was found that in the presence of thiourea the gold oxidation rate increases chandra and jeffrey, 2004. C was performed in furnace before leaching process laboratory furnace 2. Read thiourea leaching of a coppergold ore using statistical design, hydrometallurgy on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at. Alternatively, you can download the file locally and open with any standalone pdf reader. 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.
The process design of gold leaching and carboninpulp circuits 14 januaryfebruary 1999 the journal of the south african institute of mining and metallurgy figure 2the carboninpulp cip process figure 1computeraided process engineering cape. Study on mechanism of gold leaching by thiourea in the. An innovative thiourea gold leaching process sciencedirect. In this paper the optimum conditions for leaching gold from sulfide ore with thiourea are studied experimentally. Hence, the application of thiourea to gold leaching may lie in improving other alternative lixiviant processes where only small dosages are used. It was noted that leaching time increases with decreasing concentrations of fe 111 ions, which were reduced to fe 11 during the reaction, a dynamic thiourea leaching of gold and silver was performed. However, in actual leaching systems, some sulfide minerals significantly catalyze the redox reaction between thiourea and ferric ion, causing high thio urea. A leaching agent for gold leaching and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. After one hour of leaching time about 50 % silver and 98 % gold were solubilized. The role of ligands and oxidants in thiosulfate leaching of gold.
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 gold bearing ore 4 gt au, at laboratory scale. If they are present in the ore, extra cyanide must be added which can add considerably to the cost of leaching the gold. Gold extraction was 89% and thiourea consumption was 3. Recovery of precious metals from a thiourea leach pesic. 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. In fact, one study suggests that copper, antimony, and arsenic minerals, and activated carbon actually increase the effectiveness of thiourea processing of gold. Thiourea leaching of gold concentrates and recovery of gold.
The leaching of gold in thioureathiocyanate solutions has been studied by the rotatingdisc technique using ferric sulfate as oxidant. The residue from the first stage was subjected to thiourea leaching in the presence of 0. The leaching and adsorption of gold using low concentration. Thiourea is easily oxidized to formamidine disulphide, which reduces the leaching efficiency and increases reagent consumption. At the same time, some fundamental investigations of the system have been reported. The leaching of gold and silverbearing ores with thiourea fas. Imperial college visitor synopsis the aqueous chemistry of goldl that has found practical application ismainly the chemistry ofthe. Therefore, a method for leaching or dissolving gold from ores or precious. Examples include copper, nickel, iron and sulphide minerals. Recovery of gold from acidic thiourea leaching solution of. Minerals that cause excessive consumption of cyanide are called cyanocides. Imperial college visitor synopsis the aqueous chemistry of gold l that has found practical application ismainly the chemistry ofthe. Thiourea is a reducing and complexing agent and can be used for the processing of gold and silver.
1255 1134 23 93 1202 1090 605 866 125 1253 1089 1397 308 1248 616 577 1561 269 609 273 474 1474 872 1215 1206 1485 423 434 1076 1482 13 1185 367 575 26 937 638 142 926 755 420