Thiosulfate Solution Research Articles

Improving the cementation effect of copper on gold in thiosulfate solution by pre-regulating the existing form of Cu2+

The effective recovery of Au(S2O3)23− from leachates using thiosulfate gold extraction techniques remains challenging. Metal cementation can be efficiently used to recover Au(S2O3)23−, but is easily affected by the oxidant (Cu(II)) in solution, leading to problems such as high consumption of the reduced metals and copper–gold co-precipitation. Copper powder cementation can prevent the co-precipitation of copper in solution to improve the grade of the gold product and also supplement the oxidant in the solution, thereby enhancing the cyclic leaching of gold into the solution, which can reduce production costs. In this study, copper powder was used to recover gold ions and the results showed that the gold cementation rate was negatively correlated with the Cu(NH3)42+ concentration. In order to weaken the negative influence of Cu(NH3)42+, this study proposes the application of a reduction voltage to convert Cu(NH3)42+ in solution to Cu(S2O3)35− before adding copper powder. After applying a reduction voltage of 0.14 V to a solution of 5 mmol/L CuSO4, 0.5 mol/L NH3, 0.1 mol/L Na2S2O3, and 10 mg/L Au(S2O3)23− for 20 min, the concentration of Cu(NH3)42+ in the solution changed from 5 mmol/L to 0.88 mmol/L. Under these conditions, gold ions were recovered, and the consumption of copper powder was reduced by 60%. Scanning electron microscopy and X-ray photoelectron spectroscopy characterization showed that under a applied reduction potential, the gold content on the surface of the copper powder was higher, and the Cu(II) content in the surface copper species was lower than that achieved in the direct cementation of copper powder. After cementation was completed, stirring the residual solution for 20 min restored the concentration of Cu(NH3)42+ to 4.963 mmol/L. At this point, the leaching rate of gold ore into the solution reached 89% of the first leaching, which maximized the circulation of the solution.

A comparative study of electrodeposition and sodium dithionite reduction for recovering gold in gold-rich solution from the adsorption of thiosulfate solution by ion exchange resin

A comparative study was performed on electrodeposition and sodium dithionite reduction for recovering gold in the gold-rich solution from the adsorption of thiosulfate solution by ion exchange resin. Using electrodeposition method, gold started to deposit when the potential was lower than −100 mVHg/HgO. The rise of Cl− concentration improved gold deposition while the increases of SO32− and S2O32− concentrations were unbeneficial to gold deposition. When the solution was deposited at the optimum potential of −600 mVHg/HgO for 5 h, the gold deposition percentage reached 99.33 %. With sodium dithionite reduction method, the gold reduction percentage achieved 100 % after only 5 min as S2O42− dosage was eight times of the theoretical amount. The increases of SO32− and S2O32− concentrations hindered gold reduction while the augment of Cl− concentration had no obvious effect. Overall, sodium dithionite reduction method has the advantages of shorter reaction time, higher gold recovery percentage, better solution stability and lower recovery cost, and thus it has a broader industrial application prospect.

Development of methods for controlling the quality of hypochlorous acid solution obtained by electrochemical synthesis

The article presents materials on developing quality control methods for hypochlorite acid obtained by electrochemical synthesis. Electrochemical synthesis of hypochlorous acid was carried out using a combined electrochemical-pyrolytic method. The electrocatalytic activity of the obtained materials in the hypochlorite acid synthesis reaction was evaluated under the electrolysis of 0.05 M NaCl solutions in a duct cell with a Ti cathode at 25 ºС. The cathode area was varied, so the cathode current density was 40 mA/cm2. The pH of the solutions was monitored with a pX-150MI universal ionometer. The volumetric current density in the channel cell was 2.4 A/dm3, and the volumetric rate of solution supply was 9.5 l/h. The authors developed an original method of iodometric titration, which is based on the sequential determination of the content of hypochlorite ions, their total content with chlorite ions, and the total content simultaneously with chlorite and chlorate ions. The content of individual components of the mixture is determined as the difference between the total content of ions and the content of hypochlorite ions. The iodometric method of titration of oxidants is based on the reaction of replacing oxygen-containing compounds of chlorine with elemental iodine with its subsequent titration with standard solutions of sodium thiosulfate. It is proposed to fix the endpoint of the titration potentiometrically, which allows you to speed up the analysis, and it is also relatively easy to automate it using an automatic titrator. The content of oxygen-containing compounds in the solutions depends on the oxidation conditions and the specified operating modes of the electrochemical catalyst. The solution's acidity determines the presence of hypochlorous acid and can be calculated based on the equilibrium constant of its dissociation. The developed analysis methods will allow the control of the quality of veterinary drugs based on hypochlorous acid obtained by electrochemical synthesis.

Adsorption of Gold from Copper–Tartrate–ThiosulfateSolutions with Ion-Exchange Resins

The adsorption behavior of gold from copper–tartrate–thiosulfate solutions with ion-exchange resins was studied in this paper. Experimental parameters include resin dosage, pH, temperature, copper, tartrate, and thiosulfate concentration. A moderate increase in resin dosage, pH, temperature, and tartrate concentration is beneficial for gold adsorption, but an excessive tartrate concentration or higher temperature depresses the adsorption process. Increasing copper and thiosulfate concentrations may competitively occupy the active sites on the resin surface, leading to a reduction in the gold adsorption capacity. The XPS and FT-IR analyses indicate that copper and gold on the resin after adsorption mainly exist in the form of Cu+ and Au+, and sulfur mainly exists in the form of SO42− and S2O32−. This implies that the use of resin for gold recovery from thiosulfate leachate may face critical challenges because there is inevitably a higher content of copper and thiosulfate.

The comparison of gold extraction methods from the rock using thiourea and thiosulfate

AbstractGold extraction from the rock is generally carried out using mercury. However, the high toxicity of mercury has a very dangerous impact on the environment and health. Various efforts have been made to reduce the use of mercury in gold extraction, one of which is the leaching method using thiosulphate and thiourea solution because they have low toxicity and are environmentally friendly. This study aimed to determine the results of gold extraction with thiosulphate and thiourea solution and determined the optimum concentration and time of extraction. The yield of the gold extract with thiosulphate solution was greater than that of thiourea solution. The thiosulphate solution had an optimum concentration of 0.3 M and an optimum time of 2 h. While the thiourea solution had an optimum concentration of 0.2 M and an optimum time of 3 h. The results of the Friedman test on the leaching time and concentration parameters show that leaching time has a significant effect on the Au leaching process, and the concentration parameter does not affect the Au leaching process from solid samples.

Leaching of Gold from an Oxide Gold Ore with Copper–Tartrate–Thiosulfate Solutions at Elevated Temperatures

Leaching of Gold from an Oxide Gold Ore with Copper–Tartrate–Thiosulfate Solutions at Elevated Temperatures

Application of cationic membrane electrolysis on the recovery of copper from thiosulfate solutions

Due to the instability of thiosulfate ions (S2O32−), the recovery of metals from thiosulfate solution using direct electrodeposition has not been widely adopted yet. In the current work, the cationic membrane electrolysis (CME) equipped with cationic membrane was employed for the copper recovery from thiosulfate solution. The effect of operational parameters such as pH and ionic strength of anodic compartment, electrode distance, cell voltage and electrolysis temperature on the copper stripping were investigated systematically, and the duration of cationic membrane was considered subsequently. The result indicated that the pH of anodic compartment played a decisive role in the electrolysis process, i.e. high pH value (>14.0) promoted OH− ions penetration, while low pH (<13.0) easily generated H+ and passed through cationic membrane leading to the dissociation of S2O32−. At optimal experimental conditions, the recovery efficiency of copper reached more than 99%, with energy consumption of 1.58 W h/g Cu, while less than 0.3% of S2O32− was decomposed which was consistent with IR analysis of electrolytic solution. Besides, the cationic membrane used in electrolysis process reached 10 times and easily regenerated. This work provided an effective green and economic approach to recover copper from thiosulfate solution, and then avoid the decomposition of S2O32− using electrolysis process.

A Pretreatment of Refractory Gold Ores Containing Sulfide Minerals to Improve Gold Leaching by Ammonium Thiosulfate: A Model Experiment Using Gold Powder and Arsenic-Bearing Sulfide Minerals

The use of thiosulfate to extract gold from refractory ores is promising because of its non-toxicity and high selectivity. Sulfide minerals (i.e., pyrite, arsenopyrite, chalcopyrite), major gold carriers in refractory gold ores, however, hinder gold extraction due to the high consumption of a lixiviant. In this study, a new method to improve gold extraction from sulfide bearing gold ores is proposed based on the model experiments using a mixture of gold powder and arsenopyrite-bearing sulfide (HAsBS) ore. The effects of HAsBS ore on gold leaching in ammonium thiosulfate solutions were investigated, and it was found that gold extraction in the presence of HAsBS ore was suppressed because of the unwanted decomposition of thiosulfate on the surface of sulfide minerals. To improve gold extraction in the presence of the sulfide minerals, this study investigated the effects of the pretreatment of HAsBS ore using ammonium solutions containing cupric ions and confirmed that HAsBS ore was oxidized in the pretreatment and its surface was covered by the oxidation products. As a result, thiosulfate consumption was minimized in the subsequent gold leaching step using ammonium thiosulfate, resulting in an improvement in gold extraction from 10% to 79%.

Selective Cementation of Gold Using an Iron Oxide and Zero-Valent Aluminum Galvanic System from Gold–Copper Ammoniacal Thiosulfate Solutions

Ammonium thiosulfate leaching is a promising alternative to the conventional cyanide method for extracting gold from ores. However, strategies for recovering gold from the leachate are less commercially used due to its low affinity to gold. The present study investigated the recovery of gold from the leachate using iron oxides (hematite, Fe2O3 or magnetite, Fe3O4). Cementation experiments were conducted by mixing 0.15 g of aluminum powder as an electron donor and 0.15 g of an electron mediator (activated carbon, hematite, or magnetite) in 10 mL of ammonium thiosulfate leachate containing 100 mg/L gold ions and 10 mM cupric ions for 24 h at 25 °C. The results of the solution analysis showed that when activated carbon (AC) was used, the gold was recovered together with copper (recoveries were 99.99% for gold and copper). However, selective gold recovery was observed when iron oxides were used, where the gold and copper recoveries were 89.7% and 21% for hematite and 85.9% and 15.4% for magnetite, respectively. An electrochemical experiment was also conducted to determine the galvanic interaction between the electron donor and electron mediator in a conventional electrochemical setup (hematite/magnetite–Al as the working electrode, Pt as the counter electrode, Ag/AgCl as the reference electrode) in a gold–thiosulfate medium. Cyclic voltammetry showed a gold reduction “shoulder-like” peak at −1.0 V using hematite/Al and magnetite/Al electrodes. Chronoamperometry was conducted and operated at a constant voltage (−1.0 V) determined during cyclic voltammetry and further analyzed using SEM-EDX. The results of the SEM-EDX analysis for the cementation products and electrochemical experiments confirmed that the gold was selectively deposited on the iron oxide surface as an electron mediator.

Investigation of the Bimodal Leaching Response of RAM Chip Gold Fingers in Ammonia Thiosulfate Solution.

Oxidative thiosulfate leaching using Cu(II)-NH3 has been explored for both mining and recycling applications as a promising method for Au extraction. This study seeks to understand the dissolution behavior of Au from waste RAM chips using a Cu(II)-NH3-S2O3 solution. In the course of this work, bimodal leaching and Au loss were observed in a manner that we have not identified in the literature. Identification of the existence of a specific Au-Ni-Cu lamellar structure in the gold fingers from RAM chips by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) revealed the possibility of interference between Au recovery and the existence of Cu and Ni. During leaching, the co-extraction of Ni was found to predict a negative impact on the Au recovery, as a result of chemical interactions from the Au-Ni-Cu interlayer. Decopperization as a pretreatment was found necessary to remove the pre-existing Cu and promote Au leaching. As part of the study parameters, such as Cu(II) concentration, aeration rates, thiosulfate and ammonia concentrations, particle sizes, and temperatures, were investigated. A satisfactory Au recovery of 98% was achieved using 50 mM Cu(II), 120 mL/min aeration rate, 0.5 M (NH3)2S2O3, and 0.75 M NH4OH (i.e., AT/AH ratio of 0.67) for 4 h residence time at room temperature (25 °C). However, there were several high recoveries prior to Au loss from the lixiviant. It was revealed that the main cause of lower Au recovery was due to a precipitation or cementation reaction that included a sulfur species formation. Because of the bimodal leaching, a composite response comprised of the time to Au loss and maximum recovery was developed, termed leaching proclivity, to facilitate statistical analysis. Furthermore, this study explores the interactions between Au-Ni-Cu and provides suggestions for improving Au thiosulfate leaching under the interference of co-existing metals from waste PCB materials.

Facile synthesis of thiolated silica-encapsulated magnetic adsorbents: Effective adsorption and rapid separation of Au(Ⅰ) from thiosulfate solution

It is important to develop a facile and highly efficient synthetic strategy to fabricate an adsorbent exhibiting excellent adsorption performance and separation ability to recover Au from thiosulfate solutions. Herein, we report a magnetic silica composite (Fe3O4 @SiO2-SH) that was successfully fabricated using an economical, one-pot synthesis method for efficient Au(I) adsorption. The results revealed that the performance of the adsorbent was pH dependent, and the single saturated adsorption capacity was 15.11 mg/g. The adsorption process could be well-explained by the Elovich kinetic model and Langmuir isotherm model, indicating that chemical adsorption dominated the monolayer adsorption process. Furthermore, the adsorption process was exothermic. The chemical structures and properties of the adsorbents were analyzed using various characterization and analysis methods. The chelating interaction between -SH and Au(I) promoted the adsorption of Au on Fe3O4 @SiO2-SH. The gold-loaded, highly reusable adsorbent could be readily eluted using Na2S2O3 (3 mol/L), and > 90% of the gold could be recovered from the adsorbent in a thiosulfate gold leaching solution with Cu2+-NH3-S2O32- as the leaching system. Most of the adsorbent in the pulp could be collected using a magnet, and this reduced the separation cost. The adsorbent can recover more than 90% of gold in both simulated and actual thiosulfate-based gold leaching solutions, indicating that the results reported herein provide a cost-effective strategy for the fabrication of magnetic silica composites characterized by a satisfactory adsorption capacity.

Leaching of Gold with Copper–Tartrate–Thiosulfate Solutions

Leaching of Gold with Copper–Tartrate–Thiosulfate Solutions

Gold recovery from pregnant thiosulfate solution by ion exchange resin: Synergistic desorption behaviors and mechanisms

The behaviors and mechanisms of gold desorption from its loading resin with the mixed solution of Na2SO3 and NaCl were studied. The desorbent displayed evident “synergistic role” on the gold desorption and had good desorption performance over wide ranges of reagent concentration, flow rate and gold loading amount. Based on the thermodynamic analysis, a two-step desorption mechanism was proposed: (1) SO32– reacted with [Au(S2O3)2]3– to generate [Au(S2O3)(SO3)]3–; (2) The resin had weak affinity for the two-ligand gold complex which was thus replaced by Cl– readily. SEM-EDS, characteristic color of gold complex, Raman spectra and binding energy calculation results indicated SO32– could react with [Au(S2O3)2]3– to form [Au(S2O3)(SO3)]3–, and the affinity of the resin for the newly-generated complex was weaker than that for Cl–, which demonstrated the above mechanism. The mechanism model of gold recovery from pregnant thiosulfate solution by ion exchange resin was finally constructed.

Aliquat-336 impregnated chitosan microspheres for Au(I) extraction from thiosulfate solution: Preparation, adsorption mechanism, and application

In this paper, Ionic liquid Aliquat-336 impregnated chitosan microspheres (CMA) was synthesized and applied for Au(I) recovery from thiosulfate solution, which possessed adjustable particle size, good hardness and good selectivity adsorption capacity. The synthesis parameters (Aliquat-336 dosage and size) of CMA were explored. And the effects of initial solution pH, initial gold concentration, thiosulfate concentration and temperature on the gold(I) adsorption performance by CMA were was investigated systematically. The results showed CMA performed well over a wide pH range, and maximum gold adsorption capacity of 20.3 mg/g. Additionally, the gold adsorption behavior on CMA was similar to pseudo-first-order kinetics and the Langmuir model. SEM-EDS, FT-IR and XPS analyses confirmed that the mechanism of [Au(S2O3)2]3- adsorb on the CMA may be anion exchange. Notably, CMA exhibited an excellent selectivity for Au(I) in a Cu-ethylenediamine (en)-S2O32- solution. Loaded gold on CMA was easily eluted using a sodium sulfite solution, achieving a gold recovery of 62.2 %, even after four adsorption–desorption cycles. Finally, in the actual gold ore leachate adsorption and slurry adsorption method, the adsorption of gold and copper by CMA is approximately 98 % and 7 %, respectively. This study makes significant progress towards gold selective recovery in thiosulfate system, which is useful for the gold thiosulfate hydrometallurgy field.

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

Aminophosphonic acid derivatized polyacrylonitrile fiber for rapid adsorption of Au(S2O3)23– from thiosulfate solution

A fast and efficient Au (I) recovery adsorption method from an actual leaching solution of Cu2+-en-S2O32- is presented. Aminophosphonic acid derivatized polyacrylonitrile fibers (PAN-NP), prepared with triethylenetetramine and phosphoric acid by chemical grafting, were used as the adsorbent. The adsorbent was well characterized by FT-IR, SEM, TGA and XPS. The effects of contact time, pH, temperature, and Au (Ⅰ) concentration were also investigated. PAN-NP can rapidly capture Au(S2O3)23– (20 min) and has a maximum adsorption capacity of 14.68 kg/t. Compared with -SH modified, PAN-NP has better stability and without oxidized. The adsorption process was described based on the Langmuir isothermal model (R2 > 0.99). Thermodynamic parameters indicated that the adsorption of Au(S2O3)23– on PAN-NP was exothermic (ΔHθ = −9.906 kJ/mol) and adsorption mechanism involved a collective effect resulting the anion exchange of Au(S2O3)23– with –RNH3+H2PO3-, electrostatic attraction between –RNH3+ and Au(S2O3)23– and complexation of P = O with Au (Ⅰ). Besides, PAN-NP-Au can be effectively eluted by sodium sulfite. Importantly, in the Cu2+-en-S2O32- actual leaching solution, the PAN-NP can efficiently recover Au (I) with an adsorption percentage of up to 97 % at a the solid­liquid ratio of 1:50, thereby affording a satisfactory application result. This is a meaningful method for recovering Au (Ⅰ) from thiosulfate solution.

Spectrophotometric Determination of Thiosulfate in Desulfurization Solutions by Decoloration of Methylene Blue

Spectrophotometric Determination of Thiosulfate in Desulfurization Solutions by Decoloration of Methylene Blue Published on: May 1, 2023 Xiuxiu Zhao, Ming Xu, Chunying Ma, Yingying Ma, Xianji Ma Spectroscopy, May 2023, Volume 38, Issue 5 Pages: 19–22,34 This article proposes a method for the determination of thiosulfate by decoloring spectrophotometry with methylene blue as an oxidant. Methylene blue has redox properties. Its oxidized form is blue, and its reduced form is colorless. Thiosulfate is a medium-strength reducing agent. In an acidic medium, the two can undergo redox reactions to reduce methylene blue and cause the solution to exhibit a fading reaction within a certain range, and the degree of fading is proportional to the amount of thiosulfate added. This method measures the change in absorbance (AU) at a fixed wavelength of 664 nm, and ΔAU has a linear relationship with the content of thiosulfate. The linear range is 0–0.3 mmol/L. From this curve, the content of thiosulfate in the desulfurization solution can be accurately measured. This method is not interfered with by other secondary salts in the desulfurization solution during the thiosulfate determination process, and has high sensitivity. The color change can be observed by the naked eye to judge whether there is thiosulfate in the solution. This method is simple to perform and is an improved method for the determination of thiosulfate in a desulfurization solution.

Synthesis of highly superhydrophilic [formula omitted] film using dip coating method

In the present work, Copper Oxide (Cu2O) film is fabricated on a glass using mixing solution of sodium thiosulfate and copper sulfate by dip coating method. After some modification super hydrophilic Cu2O film was obtained. The prepared film shows outstanding water absorbance with very less contact angle. XRD shows mixed phase of Cu2O and CuO. The UV–VIS spectroscopy of film shows absorption peak at 575 nm which corresponds to 2.56 eV energy band gap which is calculated from tauc’s plot. SEM analysis shows that the surface morphology of deposited Cu2O film on glass slide shows grain of irregular shape. The EDX spectrum of obtained Cu2O shows elemental composition of 61.58% of Cu and 38.42% of O. FTIR provides information about materials phase composition. Results show that all copper oxide surfaces tends to hydrophilic behavior after drying at ambient condition.

Non-toxic, high selectivity process for the extraction of precious metals from waste printed circuit boards

The work presented here focused on the extraction of gold (Au), silver (Ag) and palladium (Pd) from electronic waste using a solution of ammonium thiosulfate. Thiosulfate was used as a valid alternative to cyanide for precious metal extractions, due to its non-toxicity and high selectivity. The interactions between sodium thiosulfate, total ammonia/ammonium, precious metal concentrations and the particle size of the waste printed circuit boards (WPCBs) were studied by the response surface methodology (RSM) and the principal component analysis (PCA) to maximize precious metal mobilization. Au extraction reached a high efficiency with a granulometry of less than 0.25 mm, but the consumption of reagents was high. On the other hand, Ag extraction depended neither on thiosulfate/ammonia concentration nor granulometry of WPCBs and it showed efficiency of 90% also with the biggest particle size (0.50 < Ø < 1.00 mm). Pd extraction, similarly to Au, showed the best efficiency with the smallest and the medium WPCB sizes, but required less reagents compared to Au. The results showed that precious metal leaching is a complex process (mainly for Au, which requires more severe conditions in order to achieve high extraction efficiencies) correlated with reagent concentrations, precious metal concentrations and WPCB particle sizes. These results have great potentiality, suggesting the possibility of a more selective recovery of precious metals based on the different granulometry of the WPCBs. Furthermore, the high extraction efficiencies obtained for all the metals bode well in the perspective of large-scale applications.

Post-Leaching of Silver from a Non-Sulfide Lead–Zinc Ore Flotation Tailing Leach Residue in a Copper–Ammonium Thiosulfate Solution: A Fuzzy Logic Prediction

Post-Leaching of Silver from a Non-Sulfide Lead–Zinc Ore Flotation Tailing Leach Residue in a Copper–Ammonium Thiosulfate Solution: A Fuzzy Logic Prediction