PDF Publication Title:
Text from PDF Page: 036
3.3 Iodine Leaching Iodine/iodide has been reported as an alternative to cyanidation with air as the oxidant (Qi et al., 1991; Angelidis et al., 1995; Baghalha, 2012). Significant gold-iodine-iodide system reactions are listed in Eq. 3.3, 3.4, 3.5, 3.6, and 3.7. 2Au + 3I3- = 2AuI4- + I- 2Au + I- + I3- = 2AuI2- AuI + I- = AuI2- AuI4- + I- = AuI2- + I3- 3AuI2- = 2Au + AuI4- +2I- pK = 2.44 pK = 1.42 pK = 0.15 pK = 17.7 pK = 1.2 (3.3) (3.4) (3.5) (3.6) (3.7) Of all the halogens, the gold iodide complex is the most stable in aqueous solution. It is reported that both the diiodo and the tetraiodo complexes are stable up to pH 14, and the tetraiodo complex is more stable than the tetrabromo complex and tetrachloro complex (Kelsall et al., 1993). Furthermore, the standard redox potential of Au/AuI4- at 25 °C is approximately 0.57 V vs SHE, which is much lower than that of Au/AuCl4- (Wan et al., 1993). The advantage of iodine over chlorine and bromine is that leaching can be conducted over a wider pH range, as shown in Fig. 3.1 (Kelsall et al., 1993). The gold dissolution rate is highly dependent on iodine and iodide concentrations and is not affected by pH changes over the pH range of 2-10 (Aylmore, 2005). Qi and Hiskey investigated the kinetics and mechanism of the gold dissolution in iodide solutions using a rotating disk technique. This indicated that gold was oxidized by the mass transport controlled reaction as shown in Eq. 3.4. The kinetics of this reaction exhibited first order with respect to I3- and half order with respect to I- with an activity energy of 33 KJ/mole. Angelidis et al. also examined the feasibility of iodine-iodide solutions for gold dissolution from a roasted pyrite-arsenopyrite ore. Approximately 60% of gold could be recovered at the triodide concentration of 1.25 X 10-4 M and iodide concentration of 10-2 M (Angelidis et al., 1995). Baghalha used an iodine/iodide solution to leach gold from two types of gold ores, a carbonaceous ore and an oxidized ore. The study showed that only 20% gold could be extracted in the presence of 20 g/L iodide and 8g/L iodine. This result is due to adsorption of gold-iodide complexes on organic matter. In contrast, 89% of gold was leached from the oxide ore in the solution containing 20 g/L iodide and 4g/L iodine within one day (Baghalha, 2012). 23PDF Image | HYDROMETALLURGICAL TREATMENT OF E-SCRAP
PDF Search Title:
HYDROMETALLURGICAL TREATMENT OF E-SCRAPOriginal File Name Searched:
Cui_mines_0052E_11489.pdfDIY PDF Search: Google It | Yahoo | Bing
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
IT XR Project Redstone NFT Available for Sale: NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Be part of the future with this NFT. Can be bought and sold but only one design NFT exists. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Turbine IT XR Project Redstone Design: NFT for sale... NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Includes all rights to this turbine design, including license for Fluid Handling Block I and II for the turbine assembly and housing. The NFT includes the blueprints (cad/cam), revenue streams, and all future development of the IT XR Project Redstone... More Info
Infinity Turbine ROT Radial Outflow Turbine 24 Design and Worldwide Rights: NFT for sale... NFT for the ROT 24 energy turbine. Be part of the future with this NFT. This design can be bought and sold but only one design NFT exists. You may manufacture the unit, or get the revenues from its sale from Infinity Turbine. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Supercritical CO2 10 Liter Extractor Design and Worldwide Rights: The Infinity Supercritical 10L CO2 extractor is for botanical oil extraction, which is rich in terpenes and can produce shelf ready full spectrum oil. With over 5 years of development, this industry leader mature extractor machine has been sold since 2015 and is part of many profitable businesses. The process can also be used for electrowinning, e-waste recycling, and lithium battery recycling, gold mining electronic wastes, precious metals. CO2 can also be used in a reverse fuel cell with nafion to make a gas-to-liquids fuel, such as methanol, ethanol and butanol or ethylene. Supercritical CO2 has also been used for treating nafion to make it more effective catalyst. This NFT is for the purchase of worldwide rights which includes the design. More Info
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
Infinity Turbine Products: Special for this month, any plans are $10,000 for complete Cad/Cam blueprints. License is for one build. Try before you buy a production license. May pay by Bitcoin or other Crypto. Products Page... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)