The Experts below are selected from a list of 15360 Experts worldwide ranked by ideXlab platform

Tao Jiang - One of the best experts on this subject based on the ideXlab platform.

  • eco friendly and economical Gold Extraction by nickel catalyzed ammoniacal thiosulfate leaching resin adsorption recovery
    Journal of Cleaner Production, 2019
    Co-Authors: Zhonglin Dong, Yongbin Yang, Xiaoliang Liu, Tao Jiang
    Abstract:

    Abstract Nickel catalyzed ammoniacal thiosulfate leaching-resin adsorption recovery, an environmentally friendly and cost-effective process, was developed to extract Gold from a Gold concentrate calcine. The catalytic mechanism was presented based on thermodynamic analysis that NH3 catalyzed the anodic dissolution of Gold, and Ni3O4 catalyzed the cathodic reduction of O2. The leaching result indicates that thiosulfate consumption reduced considerably under nickel-ammonia catalysis, whilst Gold leaching percentage was comparable with that under conventional copper-ammonia catalysis. The kinetics study demonstrates that the reaction orders of initial nickel (II), ammonia and thiosulfate concentrations were separately 0.21, 0.37 and 0.28. The apparent activation energy calculation shows that the catalytic efficiencies of nickel-ammonia and copper-ammonia were close, and Gold leaching with nickel-ammonia catalysis was possibly diffusion controlled that was supported by the XPS analysis result. For the Gold recovery from its actual leach solution by ion-exchange resin, the resin and desorbent dosages were less, and loaded Gold could be desorbed by a simple one-step desorption process because nickel did not co-adsorb with Gold on resin surface. Besides, Gold leaching percentage only declined 1.8% after the leach solution was recycled five times, and thiosulfate consumption decreased 5.8 kg/t-calcine.

  • an eco friendly and efficient process of low potential thiosulfate leaching resin adsorption recovery for extracting Gold from a roasted Gold concentrate
    Journal of Cleaner Production, 2019
    Co-Authors: Zhonglin Dong, Tao Jiang, Yongbin Yang
    Abstract:

    Abstract Thiosulfate is a promising alternative lixiviant to cyanide for leaching Gold from its ores/concentrates due to increased environmental and public concern over the use of poisonous cyanide. However, high thiosulfate consumption and high cost for Gold recovery from pregnant solution have limited its industrial application. In this work, an innovative process for extracting Gold from a roasted Gold concentrate is proposed: firstly, Gold leaching with thiosulfate under a low mixed potential; then, Gold separation and enrichment with an ion-exchange resin to produce concentrated Gold solution that can be refined to metallic Gold by electrowinning. Compared with traditional thiosulfate leaching, the mixed potential of stable stage of low potential leaching decreased around 30 mV through using low concentrations of reagents and limiting oxygen supply, a slightly higher Gold Extraction was obtained, whilst thiosulfate consumption substantially reduced from 34.6 kg/t-concentrate to 15.8 kg/t-concentrate. The amount of undesirable anions particularly cuprous thiosulfate and polythionates in the pregnant solution significantly dropped owing to the mild leaching conditions. This considerably weakened their competitive adsorption with Gold (I) thiosulfate onto the resin, contributing to the decrease of resin dosage used for Gold recovery. The eluent dosage also declined because of the less interfering ions on resin surface. Based on these results, low potential thiosulfate leaching followed by resin adsorption recovery is put forward, providing an eco-friendly and efficient process for Gold Extraction from roasted Gold concentrate.

  • study on the oxygen pressure alkaline leaching of Gold with generated thiosulfate from sulfur oxidation
    Hydrometallurgy, 2018
    Co-Authors: Qiang Zhong, Yongbin Yang, Tao Jiang
    Abstract:

    Abstract Thiosulfate leaching is a promising alternative to cyanidation, but high thiosulfate consumption has restricted its wide commercial application. In this study, the simultaneous Gold Extraction by generated thiosulfate deriving from the oxidation of added sulfur during oxygen pressure alkaline leaching (OPAL) without cupric-ammonia catalysis was investigated, and the results were encouraging. It has been proven that the sulfur can be produced from the oxidation pretreatment of sulfide Gold ores or concentrates. Thus, this study provides an enlightenment to solve the problem of high thiosulfate consumption by a two-step process consisting of an appropriate oxidation pretreatment for sulfide Gold ores or concentrates and OPAL. The Gold Extraction from an ore and terminal thiosulfate concentration after the OPAL in this study reached 78.0% and 0.28 M, respectively, and they were further improved to 83.6% and 0.31 M by the addition of humic acid (HA). The function of HA was proposed that it not only prevented passivation species from coating Gold surface but also weakened the decomposition of generated thiosulfate. It can also be concluded that the improvement of temperature and oxygen partial pressure can substitute the cupric-ammonia catalysis for thiosulfate leaching.

  • improved thiosulfate leaching of a refractory Gold concentrate calcine with additives
    Hydrometallurgy, 2015
    Co-Authors: Yongbin Yang, Tao Jiang, Xi Zhang, Dan Wang
    Abstract:

    Abstract One of the major problems of thiosulfate leaching was the high consumption of thiosulfate. In this work, additive was used to reduce thiosulfate consumption and simultaneously increase Gold leaching. Thiosulfate leaching without additive was not effective to treat a refractory Gold concentrate calcine with high iron, sulfur and arsenic due to its low Gold Extraction (72.7%) and high thiosulfate consumption (42.4%). Thus, several additives including sodium chloride, sodium sulfite, CMC (sodium carboxymethyl cellulose), CMS (sodium carboxymethyl starch) and HA (sodium humic acid) were used to improve the leaching. HA as a new kind of additive had the best performance, and it could improve Gold Extraction to 81.4%, which was obviously higher than the Extraction by cyanidation (78.2%), and reduce thiosulfate consumption to 13.2%. As the XPS and SEM/EDS results indicated, there were less passivation species including copper sulfides, sulfur, iron hydroxide, etc. on the surface of calcine leached with the addition of HA. The role of the HA in the thiosulfate leaching was also preliminarily analyzed in this paper, and was proposed as follows: HA weakened the interaction between cupric ions and thiosulfate, and also eliminated the catalytic effects of iron minerals on thiosulfate decomposition; on the other hand, HA prevented passivation species from coating the surfaces of Gold and Gold-bearing minerals, and allowed the Extraction of some encapsulated Gold.

Yongbin Yang - One of the best experts on this subject based on the ideXlab platform.

  • eco friendly and economical Gold Extraction by nickel catalyzed ammoniacal thiosulfate leaching resin adsorption recovery
    Journal of Cleaner Production, 2019
    Co-Authors: Zhonglin Dong, Yongbin Yang, Xiaoliang Liu, Tao Jiang
    Abstract:

    Abstract Nickel catalyzed ammoniacal thiosulfate leaching-resin adsorption recovery, an environmentally friendly and cost-effective process, was developed to extract Gold from a Gold concentrate calcine. The catalytic mechanism was presented based on thermodynamic analysis that NH3 catalyzed the anodic dissolution of Gold, and Ni3O4 catalyzed the cathodic reduction of O2. The leaching result indicates that thiosulfate consumption reduced considerably under nickel-ammonia catalysis, whilst Gold leaching percentage was comparable with that under conventional copper-ammonia catalysis. The kinetics study demonstrates that the reaction orders of initial nickel (II), ammonia and thiosulfate concentrations were separately 0.21, 0.37 and 0.28. The apparent activation energy calculation shows that the catalytic efficiencies of nickel-ammonia and copper-ammonia were close, and Gold leaching with nickel-ammonia catalysis was possibly diffusion controlled that was supported by the XPS analysis result. For the Gold recovery from its actual leach solution by ion-exchange resin, the resin and desorbent dosages were less, and loaded Gold could be desorbed by a simple one-step desorption process because nickel did not co-adsorb with Gold on resin surface. Besides, Gold leaching percentage only declined 1.8% after the leach solution was recycled five times, and thiosulfate consumption decreased 5.8 kg/t-calcine.

  • an eco friendly and efficient process of low potential thiosulfate leaching resin adsorption recovery for extracting Gold from a roasted Gold concentrate
    Journal of Cleaner Production, 2019
    Co-Authors: Zhonglin Dong, Tao Jiang, Yongbin Yang
    Abstract:

    Abstract Thiosulfate is a promising alternative lixiviant to cyanide for leaching Gold from its ores/concentrates due to increased environmental and public concern over the use of poisonous cyanide. However, high thiosulfate consumption and high cost for Gold recovery from pregnant solution have limited its industrial application. In this work, an innovative process for extracting Gold from a roasted Gold concentrate is proposed: firstly, Gold leaching with thiosulfate under a low mixed potential; then, Gold separation and enrichment with an ion-exchange resin to produce concentrated Gold solution that can be refined to metallic Gold by electrowinning. Compared with traditional thiosulfate leaching, the mixed potential of stable stage of low potential leaching decreased around 30 mV through using low concentrations of reagents and limiting oxygen supply, a slightly higher Gold Extraction was obtained, whilst thiosulfate consumption substantially reduced from 34.6 kg/t-concentrate to 15.8 kg/t-concentrate. The amount of undesirable anions particularly cuprous thiosulfate and polythionates in the pregnant solution significantly dropped owing to the mild leaching conditions. This considerably weakened their competitive adsorption with Gold (I) thiosulfate onto the resin, contributing to the decrease of resin dosage used for Gold recovery. The eluent dosage also declined because of the less interfering ions on resin surface. Based on these results, low potential thiosulfate leaching followed by resin adsorption recovery is put forward, providing an eco-friendly and efficient process for Gold Extraction from roasted Gold concentrate.

  • study on the oxygen pressure alkaline leaching of Gold with generated thiosulfate from sulfur oxidation
    Hydrometallurgy, 2018
    Co-Authors: Qiang Zhong, Yongbin Yang, Tao Jiang
    Abstract:

    Abstract Thiosulfate leaching is a promising alternative to cyanidation, but high thiosulfate consumption has restricted its wide commercial application. In this study, the simultaneous Gold Extraction by generated thiosulfate deriving from the oxidation of added sulfur during oxygen pressure alkaline leaching (OPAL) without cupric-ammonia catalysis was investigated, and the results were encouraging. It has been proven that the sulfur can be produced from the oxidation pretreatment of sulfide Gold ores or concentrates. Thus, this study provides an enlightenment to solve the problem of high thiosulfate consumption by a two-step process consisting of an appropriate oxidation pretreatment for sulfide Gold ores or concentrates and OPAL. The Gold Extraction from an ore and terminal thiosulfate concentration after the OPAL in this study reached 78.0% and 0.28 M, respectively, and they were further improved to 83.6% and 0.31 M by the addition of humic acid (HA). The function of HA was proposed that it not only prevented passivation species from coating Gold surface but also weakened the decomposition of generated thiosulfate. It can also be concluded that the improvement of temperature and oxygen partial pressure can substitute the cupric-ammonia catalysis for thiosulfate leaching.

  • improved thiosulfate leaching of a refractory Gold concentrate calcine with additives
    Hydrometallurgy, 2015
    Co-Authors: Yongbin Yang, Tao Jiang, Xi Zhang, Dan Wang
    Abstract:

    Abstract One of the major problems of thiosulfate leaching was the high consumption of thiosulfate. In this work, additive was used to reduce thiosulfate consumption and simultaneously increase Gold leaching. Thiosulfate leaching without additive was not effective to treat a refractory Gold concentrate calcine with high iron, sulfur and arsenic due to its low Gold Extraction (72.7%) and high thiosulfate consumption (42.4%). Thus, several additives including sodium chloride, sodium sulfite, CMC (sodium carboxymethyl cellulose), CMS (sodium carboxymethyl starch) and HA (sodium humic acid) were used to improve the leaching. HA as a new kind of additive had the best performance, and it could improve Gold Extraction to 81.4%, which was obviously higher than the Extraction by cyanidation (78.2%), and reduce thiosulfate consumption to 13.2%. As the XPS and SEM/EDS results indicated, there were less passivation species including copper sulfides, sulfur, iron hydroxide, etc. on the surface of calcine leached with the addition of HA. The role of the HA in the thiosulfate leaching was also preliminarily analyzed in this paper, and was proposed as follows: HA weakened the interaction between cupric ions and thiosulfate, and also eliminated the catalytic effects of iron minerals on thiosulfate decomposition; on the other hand, HA prevented passivation species from coating the surfaces of Gold and Gold-bearing minerals, and allowed the Extraction of some encapsulated Gold.

Zhonglin Dong - One of the best experts on this subject based on the ideXlab platform.

  • eco friendly and economical Gold Extraction by nickel catalyzed ammoniacal thiosulfate leaching resin adsorption recovery
    Journal of Cleaner Production, 2019
    Co-Authors: Zhonglin Dong, Yongbin Yang, Xiaoliang Liu, Tao Jiang
    Abstract:

    Abstract Nickel catalyzed ammoniacal thiosulfate leaching-resin adsorption recovery, an environmentally friendly and cost-effective process, was developed to extract Gold from a Gold concentrate calcine. The catalytic mechanism was presented based on thermodynamic analysis that NH3 catalyzed the anodic dissolution of Gold, and Ni3O4 catalyzed the cathodic reduction of O2. The leaching result indicates that thiosulfate consumption reduced considerably under nickel-ammonia catalysis, whilst Gold leaching percentage was comparable with that under conventional copper-ammonia catalysis. The kinetics study demonstrates that the reaction orders of initial nickel (II), ammonia and thiosulfate concentrations were separately 0.21, 0.37 and 0.28. The apparent activation energy calculation shows that the catalytic efficiencies of nickel-ammonia and copper-ammonia were close, and Gold leaching with nickel-ammonia catalysis was possibly diffusion controlled that was supported by the XPS analysis result. For the Gold recovery from its actual leach solution by ion-exchange resin, the resin and desorbent dosages were less, and loaded Gold could be desorbed by a simple one-step desorption process because nickel did not co-adsorb with Gold on resin surface. Besides, Gold leaching percentage only declined 1.8% after the leach solution was recycled five times, and thiosulfate consumption decreased 5.8 kg/t-calcine.

  • an eco friendly and efficient process of low potential thiosulfate leaching resin adsorption recovery for extracting Gold from a roasted Gold concentrate
    Journal of Cleaner Production, 2019
    Co-Authors: Zhonglin Dong, Tao Jiang, Yongbin Yang
    Abstract:

    Abstract Thiosulfate is a promising alternative lixiviant to cyanide for leaching Gold from its ores/concentrates due to increased environmental and public concern over the use of poisonous cyanide. However, high thiosulfate consumption and high cost for Gold recovery from pregnant solution have limited its industrial application. In this work, an innovative process for extracting Gold from a roasted Gold concentrate is proposed: firstly, Gold leaching with thiosulfate under a low mixed potential; then, Gold separation and enrichment with an ion-exchange resin to produce concentrated Gold solution that can be refined to metallic Gold by electrowinning. Compared with traditional thiosulfate leaching, the mixed potential of stable stage of low potential leaching decreased around 30 mV through using low concentrations of reagents and limiting oxygen supply, a slightly higher Gold Extraction was obtained, whilst thiosulfate consumption substantially reduced from 34.6 kg/t-concentrate to 15.8 kg/t-concentrate. The amount of undesirable anions particularly cuprous thiosulfate and polythionates in the pregnant solution significantly dropped owing to the mild leaching conditions. This considerably weakened their competitive adsorption with Gold (I) thiosulfate onto the resin, contributing to the decrease of resin dosage used for Gold recovery. The eluent dosage also declined because of the less interfering ions on resin surface. Based on these results, low potential thiosulfate leaching followed by resin adsorption recovery is put forward, providing an eco-friendly and efficient process for Gold Extraction from roasted Gold concentrate.

Toyohisa Fujita - One of the best experts on this subject based on the ideXlab platform.

  • Gold Extraction from thiosulfate solution using trioctylmethylammonium chloride
    Hydrometallurgy, 2004
    Co-Authors: Liu Kejun, Wan Tai Yen, Atsushi Shibayama, Toshio Miyazaki, Toyohisa Fujita
    Abstract:

    Abstract Alkyl phosphorus esters, alkyl amines, amine oxides and their mixtures with amines (Hydrometallurgy 46 (1997) 363; Solv. Extr. Ion Exch. 16 (6), (1998) 1407) were used to extract Gold from thiosulfate solution but the re-adjustment of pH was required and Extraction efficiency was poor in the alkaline pH range. In this study, trioctylmethylammonium chloride (TOMAC) was used as an extractant to extract Gold from thiosulfate leaching solution without pH and other adjustments. The effects of Gold concentration, pH, ammonia, thiosulfate and cupric ion concentrations, extractant concentration, diluent and retention time on Gold Extraction were investigated. It was found that 0.18 mol/L extractant diluted with n -octane+1-hexanol at O/A ratio of 1:1 could extract more than 99% of Gold from the thiosulfate solution at the standard leaching condition (1.0 mol/L S 2 O 3 2− , 0.03 mol/L Cu 2+ and 3.0 mol/L NH 3 /NH 4 + at pH 10.2) in 0.6 ks (1 ks=1000 s). The loading capacity and selectivity of the Gold extractant, trioctylmethylammonium chloride, were also studied.

  • using nickel as a catalyst in ammonium thiosulfate leaching for Gold Extraction
    Materials Transactions, 2004
    Co-Authors: Harunobu Arima, Toyohisa Fujita, Wan Tai Yen
    Abstract:

    The use of copper as a catalyst for Gold leaching in ammonium thiosulfate solution might cause the high consumption of thiosulfate. Also, the high copper consumption is resulted in the zinc precipitation process for recovering the Gold from the pregnant solution. In this investigation, nickel was used as a catalyst to minimize the reagent consumption. On a 100 mass%-75 mm of silicate type Gold ore containing 16 g/t Au and 0.2 mass% of Fe and C, the nickel catalyzed ammonium thiosulfate solution could extract 95% of Gold with the 1.2 kg/t-ore of ammonium thiosulfate consumption in 24 hours at the most favorable reagent combination of 0.0001 mol/dm 3 NiSO4, 0.05 mol/dm 3 (NH4)2S2O3 and 0.5 mol/dm 3 NH4OH at pH9.5, while the standard cyanidation at 0.02 mol/dm 3 (1.0 g/dm 3 ) NaCN consumed around 1.5 kg/t-ore NaCN. In the concentration range of 0:0001� 0:005 mol/dm 3 Ni 2þ , the ammonium thiosulfate consumption was 1� 5 kg/t-ore, while the ammonium thiosulfate consumption of copper catalyzed lixiviant was greatly increased from 3 kg/t-ore to 21 kg/t-ore as the increase of Cu 2þ concentration from 0.0001 mol/dm 3 to 0.001 mol/dm 3 . The feasibility of recycling barren solution was confirmed with zinc precipitation at nearly 100% of Gold recovery. Nickel consumption on the cementation process was less than 50%. For extracting Gold from the copper bearing sulfide ore, a higher ammonia and thiosulfate concentrations were required with 0.0001 mol/dm3 of Ni2þ. The ammonium thiuosulfate consumption with nickel as catalyst on the copper bearing sulfide ore was about 1� 5 kg/t-ore less than that using copper as catalyst.

  • Gold Recovery from Nickel Catalyzed Ammonium Thiosulfate Solution by Strongly Basic Anion Exchange Resin
    Materials Transactions, 2003
    Co-Authors: Harunobu Arima, Toyohisa Fujita
    Abstract:

    Copper catalyzed ammonium thiosulfate leaching process has been proposed as an alternative Gold Extraction process to cyanidation. In order to recover Gold from the ammonium thiosulfate solution, ion exchange process has been proposed as a Gold recovery method using strongly basic anion exchange resin. However, the co-adsorption of copper along with Gold causes difficulty in separating Gold and copper at the Gold elution stage. Our previous study has demonstrated that nickel catalyzed ammonium thiosulfate solution for Gold Extraction has the advantage of reducing thiosulfate consumption. In this study, the results also demonstrated the advantage of Gold recovery from the nickel catalyzed ammonium thiosulfate solution by strongly basic anion exchange resin. The optimal Gold loading conditions on a 1 g/dm 3 strongly base anion exchange resin (wet base value) are investigated in several ion concentrations and 95 kg-Au/t-resin has been obtained. The alternative Gold eluant was investigated as the Gold loaded resin cannot be eluted by conventional hydrochloric acid. Results showed that the elution efficiency was in the order of OH � < Cl � � NO3 � < Br � � I � < ClO4 � . The maximum Gold recovery by using 2.5 mol/dm 3 ClO4 � was around 98% with the stripped resin assayed as 0.2 kg/t Au. The feasibility of resin recycling has demonstrated that there was no deterioration in Gold adsorption and desorption for four cycles.

  • Gold leaching by using ammonium thiosulfate solution
    Shigen-to-sozai, 2001
    Co-Authors: Kejun Liu, Atsushi Shibayama, Wan Tai Yen, Toru Suzuki, Toyohisa Fujita
    Abstract:

    The sponge Gold (99.92 % pure) has been leached with ammonium thiosulfate solution. In this investigation, the Gold leaching rate (Extraction rate) and the thiosulfate oxidation rate (consumption rate) have been studied on the effects of CuSO4, (NH4)2S2O3, (NH4)2SO4, NH4OH, stirring speed and retention time. The copper ion acts as a catalyst in Gold dissolution, on the other hand, it also accelerates oxidation of thiosulfate (consumption). It was found that the best Gold Extraction was obtained at 12 hours under following optimum conditions:0.8 ∼ 1.0 mol / l (NH4)2S2O3, 0.03 mol / l CuSO4, 2.0 ∼ 3.0 mol / l NH4OH, 0.4 ∼ 0.5 mol / l (NH4)2SO4, pH 10 ± 0.2 and 150 rpm. The thiosulfate oxidation is about 15 % of the initial concentration.

G Oforisarpong - One of the best experts on this subject based on the ideXlab platform.

  • mycohydrometallurgy biotransformation of double refractory Gold ores by the fungus phanerochaete chrysosporium
    Hydrometallurgy, 2013
    Co-Authors: G Oforisarpong, K Osseoasare, Ming Tien
    Abstract:

    Abstract Double refractory Gold ores (DRGO) contain organic carbonaceous matter (CM) and sulfide minerals, and thus require pretreatment before cyanidation for Gold Extraction. Though there have been several studies into microbial pretreatment of DRGO, available literature indicates that microbial degradation of both sulfides and CM in a single-stage process has not achieved much success. In an on-going research, the fungus Phanerochaete chrysosporium, has been used to effectively reduce the Gold adsorption (preg-robbing) nature of surrogate CM on one hand, and decompose sulfides (pyrite and arsenopyrite) on the other. Such an application of fungi in hydrometallurgy has been termed ‘mycohydrometallurgy’. The present research focused on assessing the possibility of using the fungus to simultaneously decompose sulfides and deactivate carbonaceous matter in refractory Gold ores so as to liberate locked-up Gold and reduce preg-robbing. Flotation concentrate (FC) of DRGO and bacterial-oxidized FC (BFC) were utilized in this investigation. After 21 days of fungal-treatment, overall sulfide sulfur decomposition of 57% in FC led to increase in Gold Extraction from 41% to 78%. Similarly, fungal-treatment of BFC led to 13% increase in Gold Extraction over the as-received (81%). The results demonstrate a novel alternative pretreatment process for DRGO.

  • myco hydrometallurgy coal model for potential reduction of preg robbing capacity of carbonaceous Gold ores using the fungus phanerochaete chrysosporium
    Hydrometallurgy, 2010
    Co-Authors: G Oforisarpong, Ming Tien, K Osseoasare
    Abstract:

    Abstract During the cyanidation process for Gold Extraction, natural carbonaceous matter (CM) present in refractory Gold ores adsorbs dissolved aurocyanide complexes, thereby reducing Gold Extraction — a phenomenon known as preg-robbing. The natural CM consists mainly of elemental carbon, humic acids and hydrocarbons, and coal can be used to model the behavior of CM. In this study, samples of lignite, sub-bituminous, bituminous and anthracite coals were used as surrogate materials to test the capability of the fungus Phanerochaete chrysosporium to reduce the preg-robbing capacity of CM. By utilizing several growth media including glucose, millet and wheat bran it was established that millet and wheat bran provided the best environment for fungal growth and biomodification of coal. As-received, control and bio-treated coal samples were subjected to Gold adsorption tests and the results indicate that P. chrysosporium can decrease the Gold adsorption ability of coal by over 90% depending on the growth media used. Reduction in Gold adsorption was more pronounced in anthracite due to its high ability to adsorb Gold in the as-received form. The results demonstrate a potentially effective alternative pretreatment process that utilizes the fungus, P. chrysosporium, in reducing preg-robbing in Gold Extraction.