Application of cobalt catalytic activation persulfate in recovery of gold in thiosulfate leachate

Abstract

The invention relates to the technical field of precious metal recovery and water treatment, in particular to application of cobalt catalytic activation persulfate in recovery of gold in thiosulfate leachate. The invention provides application of cobalt catalytic activation persulfate in recovery of gold in thiosulfate leachate. The method comprises the following steps: blending a cobalt catalyst, persulfate and a thiosulfate leaching solution containing Au (S2O3) 2 < 3->, and carrying out complex breaking reduction to obtain a gold elementary substance. The CoNC / persulfate technology provided by the invention is proved to be a catalytic system based on singlet oxygen species, has high oxidation capacity and strong complex breaking selectivity, shows remarkable solution acid-base property adaptation and coexisting cation / anion interference resistance, and has ultrahigh recovery selectivity.

Description

Technical Field

[0001] The invention relates to the technical field of precious metal recovery and water treatment, and in particular to the application of cobalt-catalyzed activated persulfate in recovering gold from thiosulfate leachate. Background Art

[0002] The thiosulfate-copper ammonia solution system is often used to leach gold ions from electronic waste and gold ore. Compared with the aqua regia leaching system, the reaction conditions of this system are milder and it is an ideal green leaching method.

[0003] However, the gold ions in the leachate of this system are in the form of Au(S2O3)2 3- The existence of the coordination complex structure produces steric hindrance, and at the same time, saturated coordination is formed between the sulfur atoms and the gold atoms, which greatly affects the binding of Au ions to the adsorption sites.

[0004] Therefore, commonly used adsorbents, such as activated carbon, resin, molecular sieve and other traditional materials, as well as most new adsorbents, are difficult to effectively separate Au(S2O3)2 from thiosulfate leachate due to steric hindrance and low reduction potential. 3- Common adsorbents need to be modified to a certain extent. For example, CN 115282951 A discloses a method for recovering gold from thiosulfate aqueous solutions using modified activated carbon. The method modifies the activated carbon with sulfur in an attempt to improve its gold recovery rate from thiosulfate aqueous solutions. However, the gold recovery rate of the modified activated carbon is only around 50%, failing to achieve efficient recovery.

[0005] In addition, Au(S2O3)2 3- The low reduction potential makes it difficult for the subsequent gold ion reduction process to occur, which greatly affects the popularization and expansion of this green leaching system. Summary of the Invention

[0006] The invention provides the use of cobalt-catalyzed activated persulfate in recovering gold from thiosulfate leachate.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The application of cobalt catalytic activation of persulfate in the recovery of gold from thiosulfate leachate is to combine cobalt catalyst, persulfate and Au(S2O3)2 3- The gold is mixed with thiosulfate leachate and the gold is reduced by breaking the complex.

[0009] Different from the conventional application of cobalt single atom catalytic activation of persulfate system in the degradation of organic pollutants, the inventors found that cobalt single atom catalytic activation of persulfate system can efficiently recover gold from thiosulfate leachate. Cobalt catalyst can complete the recovery of Au(S2O3)23- At the same time, the cobalt catalyst activates the persulfate to produce a large amount of singlet oxygen, which oxidizes and decomplexes the adsorbed Au(S2O3)2 3- The Au-S bonds in the ions are broken, thereby releasing the Au element.

[0010] Preferably, Au(S2O3)2 3- Under the action of singlet oxygen, the gold-sulfur bond is opened, and the complex is broken and reduced to obtain gold element.

[0011] Preferably, the Au(S2O3)2 3- The recovery rate of gold is ≥99.0%, and the purity of the gold element is ≥99.5%.

[0012] Preferably, cobalt catalyst, persulfate and Au(S2O3)2 3- The mass ratio between them is 2:(10~25):(1~80).

[0013] Preferably, the Au(S2O3)2 3- The thiosulfate leachate includes: Mn 2+ Mg 2+ 、Cu 2+ 、Ni 2+ 、Fe 2+ 、Al 2+ 、Cl - PO4 3- 、HCO3 2- 、SO4 2- At least one of .

[0014] Preferably, the persulfate is potassium peroxymonosulfate and / or potassium peroxydisulfate.

[0015] In addition to persulfate, there are many other oxidants that can be used with cobalt catalysts to degrade organic matter. However, the inventors found during the experiment that not all oxidants can be used for Au(S2O3)2 3- Oxidative decomplexation, such as hydrogen peroxide, has a very poor treatment effect on the thiosulfate leachate and is completely unable to recover the Au therein.

[0016] Preferably, the cobalt catalyst is obtained by chemical vapor deposition by reacting a precursor obtained by calcining a ZnCo-ZIF material with ammonium chloride at 800-900° C. for 1-2 hours under an inert atmosphere.

[0017] Preferably, cobalt salt, zinc salt and 2-methylimidazole are mixed in methanol, stirred, centrifuged and dried to obtain ZnCo-ZIF material; under an inert atmosphere, the ZnCo-ZIF material is calcined at 850-950° C. at a rate of 5° C. / min for 2-4 hours to obtain a precursor.

[0018] Preferably, the precursor is placed at an end close to the inlet for the inert atmosphere, and the ammonium chloride is placed at an end away from the inlet for the inert atmosphere.

[0019] Preferably, the mass ratio of the precursor to ammonium chloride is 1:(10-50).

[0020] Therefore, the present invention has the following beneficial effects:

[0021] (1) The present invention found that cobalt-catalyzed activation of persulfate system can efficiently recover gold from thiosulfate leachate.

[0022] (2) The CoNC / persulfate technology provided by the present invention does not involve the use of rare metals, the dosage of Co catalyst and persulfate is ultra-low, the operation method is simple, and the reaction conditions are mild.

[0023] (3) The CoNC / persulfate technology provided by the present invention has ultrafast Au(I) recovery kinetics and ultrahigh Au(I) recovery capacity.

[0024] (4) The CoNC / persulfate technology provided by the present invention has been confirmed to be a catalytic system based on singlet oxygen species, with high oxidation ability and strong complex breaking selectivity, showing significant adaptability to solution acidity and alkalinity and tolerance to interference from coexisting cations and anions, and ultra-high recovery selectivity.

[0025] (5) The CoNC / persulfate technology provided by the present invention achieved an Au(I) recovery rate exceeding 99.0% in several simulated thiosulfate leaching systems, while traditional adsorption techniques only obtained adsorbed Au(I). In comparison, the CoNC / persulfate technology can directly obtain high-value-added elemental gold, with a gold product purity exceeding 99.5%, showing extremely high economic feasibility.

[0026] (6) The CoNC / persulfate technology provided by the present invention for efficiently recovering gold from thiosulfate leachate is effective in the treatment of Au(S2O3)2 3- After the oxidative decomplexation, the released Au(I) can be directly deposited on the surface of the CoNC material in the form of Au element, without the need for a subsequent precipitation process. This reduces the application of chemical agents during the precipitation process, is more environmentally friendly, and can reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The electron microscope scanning results of CoNC catalyst, where a is the SEM image, b and c are TEM images, d is the C element spectrum, e is the N element spectrum, and f is the Co element spectrum;

[0028] Figure 2 Structural characterization results of CoNC catalyst, where a is XRD, b is XANES, c is EXAFS, and d is EXAFS curve fitting;

[0029] Figure 3 Kinetic curves of Au(I) recovery over NC and CoNC catalysts;

[0030] Figure 4 The recovery kinetics and recovery capacity of CoNC catalyst for Au(I) under different oxidant systems, where a is the recovery kinetics and b is the recovery capacity;

[0031] Figure 5 The recovery kinetics of Au(I) by CoNC catalyst at different PDS dosages;

[0032] Figure 6 is the effect of coexisting cations on the Au(I) recovery rate of CoNC, where a is the effect of coexisting cations on the Au(I) recovery rate of CoNC, and b is the recovery selectivity of CoNC for different metal ions;

[0033] Figure 7 is the effect of the environment on the Au(I) recovery of CoNC, where a is the effect of coexisting anions on the Au(I) recovery of CoNC / PDS, and b is the Au(I) recovery of CoNC / PDS in different simulated leaching solution systems;

[0034] Figure 8 The effect of active species on the Au(I) recovery rate of CoNC, where a is the effect of different quenching agents and solvents on the Au(I) recovery kinetics of CoNC / PDS, b is the EPR spectrum, and c is the ADPA degradation curve of CoNC / PDS at different times;

[0035] Figure 9 UPLC-MS ion chromatograms of APDA degradation by CoNC / PDS system at different times;

[0036] Figure 10 The chemical structure of the product after CoNC / PDS recovers Au(I), where a is the TEM image, b is the XRD spectrum, and c is the XRD spectrum of the separated and recovered gold. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below generally represent only a portion of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0038]

Catalyst preparation

[0039] CoNC catalyst

[0040] S1. Co(NO₃)₂·6H₂O (0.103 g) and Zn(NO₃)₂·6H₂O (1.674 g) were dissolved in methanol (45 mL). The mixture was then added to 45 mL of methanol containing 2-methylimidazole (1.848 g). The mixture was sonicated at room temperature for 10 minutes and then stirred on a magnetic stirrer for 4 hours. The mixture was centrifuged, washed several times with methanol, and finally dried in a vacuum oven to obtain ZnCo-ZIF.

[0041] S2. Place 50 mg of ZnCo-ZIF powder in a quartz boat in a tube furnace. Raise the temperature to 900°C at a rate of 5°C min. -1 , maintained under an argon atmosphere for 3 hours. After cooling naturally to room temperature, it was acid-washed and dried. The resulting product was placed in a porcelain boat and placed in the center of a tube furnace for a secondary annealing treatment via chemical vapor deposition: the device was heated to 850°C under an argon atmosphere for 1 hour. Simultaneously, another porcelain boat containing 2g of NH4Cl was placed at the upstream end of the tube furnace and subjected to chemical vapor deposition to obtain the CoNC catalyst.

[0042] NC catalyst

[0043] S1. Dissolve Zn(NO₃)₂·6H₂O (1.674 g) in methanol (45 mL) and add the resulting solution to 2-methylimidazole (1.848 g) in 45 mL of methanol. Ultrasonicate at room temperature for 10 minutes and then stir on a magnetic stirrer for 4 hours. Centrifuge, rinse several times with methanol, and dry in a vacuum oven to obtain Zn-ZIF.

[0044] S2. Place 50 mg of Zn-ZIF powder in a quartz boat in a tube furnace. Raise the temperature to 900°C at a rate of 5°C min. -1 , and maintained under an argon atmosphere for 3 hours. After cooling naturally to room temperature, it was acid-washed and dried. The resulting product was placed in a porcelain boat and placed in the center of a tube furnace for a secondary annealing treatment via chemical vapor deposition: the device was heated to 850°C under an argon atmosphere for 1 hour. Simultaneously, another porcelain boat containing 2g of NH4Cl was placed at the upstream end of the tube furnace and subjected to chemical vapor deposition to obtain the NC catalyst.

[0045] [Example]

[0046] Application Example 1: Removal kinetics and recovery capacity of Au(I) by CoNC under PDS oxidant conditions

[0047] CoNC / PDS system

[0048] (1) A 10 mg / L Au(I) deionized aqueous solution (prepared from Na3Au(S2O3)2) was added to a beaker. 0.3 mM potassium persulfate (PDS) was then added. 1 mg of CoNC catalyst was weighed and added to the beaker. The mixture was magnetically stirred at room temperature. The Au(I) concentration was measured at different reaction times, and the kinetic data were recorded.

[0049] (2) 50 mL of 800 mg / L Au(I) deionized water solution (prepared from Na3Au(S2O3)2) was added to a beaker. 10 mM PDS was then added. 1 mg of CoNC catalyst was weighed and added to the beaker. After magnetic stirring at room temperature for 24 h, the Au(I) concentration was measured and the Au(I) recovery capacity was calculated.

[0050] Application Example 2: Removal kinetics and recovery capacity of Au(I) by CoNC under PMS oxidant conditions

[0051] CoNC / PMS system

[0052] (1) A 10 mg / L Au(I) deionized aqueous solution (prepared from Na3Au(S2O3)2) was added to a beaker. 0.3 mM potassium peroxymonosulfate (PMS) was then added. 1 mg of CoNC catalyst was weighed and added to the beaker. The mixture was magnetically stirred at room temperature. The Au(I) concentration was measured at different reaction times, and the kinetic data were recorded.

[0053] (2) 50 mL of 800 mg / L Au(I) deionized water solution (prepared from Na3Au(S2O3)2) was added to a beaker. 10 mM PMS was then added. 1 mg of CoNC catalyst was weighed and added to the beaker. After magnetic stirring at room temperature for 24 h, the Au(I) concentration was measured and the Au(I) recovery capacity was calculated.

[0054] Comparative Example 1

[0055] CoNC system

[0056] This comparative example is basically the same as Application Example 1, except that the addition of PDS is eliminated.

[0057] Comparative Example 2

[0058] CoNC / H2O2 system

[0059] This comparative example is basically the same as Application Example 1, except that PDS is replaced by an equal amount of hydrogen peroxide (H2O2).

[0060] Comparative Example 3

[0061] NC / PDS system

[0062] This comparative example is basically the same as Application Example 1, except that the CoNC catalyst is replaced by an equal amount of NC catalyst.

[0063] Application Example 3: Removal kinetics of Au(I) by CoNC under different PDS dosage conditions

[0064] Prepare seven beakers filled with 50 mL of a 10 mg / L Au(I) deionized water solution (prepared with Na3Au(S2O3)2). PDS was added to each beaker to adjust the PDS content to 0, 0.05 mM, 0.1 mM, 0.2 mM, 0.3 mM, 0.4 mM, and 0.6 mM. Then, 1 mg of CoNC catalyst was weighed and added to each of the seven beakers. The mixture was magnetically stirred at room temperature, and the Au(I) concentration at different reaction times was measured, and the kinetic data was recorded.

[0065] Application Example 4 Recovery of Au(I) by CoNC under the influence of coexisting cations

[0066] Seven beakers containing 50 mL of a 10 mg / L Au(I) deionized water solution (prepared with Na3Au(S2O3)2) were prepared, and 50 mg / L of Mn(II), 50 mg / L of Mg(II), 50 mg / L of Cu(II), 50 mg / L of Ni(II), 50 mg / L of Fe(II), 50 mg / L of Al(II), and a 50 mg / L mixed solution containing these six ions were added to each beaker. Subsequently, 0.3 mM PDS was added to each of the seven beakers, and 1 mg of CoNC catalyst was weighed and added to each of the seven beakers. After magnetic stirring at room temperature for 6 h, the Au(I) concentration and the concentration of other cations were measured, and the Au(I) recovery rate and the removal rate of other cations were calculated.

[0067] Application Example 5 Recovery of CoNC to Au(I) under the influence of coexisting anions

[0068] (1) Prepare 5 beakers containing 50 mL of 10 mg / L Au(I) deionized water solution (prepared from Na3Au(S2O3)2) and add 10 mg / L Cl - , 10mg / L PO4 3- , 10mg / L HCO3 2- , 10mg / L SO4 2-and a 10 mg / L mixed solution containing these four ions. Subsequently, 0.3 mM PDS was added to each of the five beakers. 1 mg of CoNC catalyst was weighed and added to each of the five beakers. After magnetic stirring at room temperature for 6 h, the Au(I) concentration was measured and the Au(I) recovery rate was calculated.

[0069] (2) Using the method in experiment (1), the concentration of coexisting anions was changed to 50 mg / L, and other test conditions remained the same, and the Au(I) recovery rate was measured.

[0070] Application Example 6 Recovery of CoNC to Au(I) under Simulated Different Thiosulfate Leaching Conditions

[0071] (1) Cu-NH3-S2O3 leaching system: Prepare three beakers filled with 50 mL of 10 mg / L Au(I) deionized water solution (prepared with Na3Au(S2O3)2) and adjust the pH to 9.0. Add 5 mM Cu(II), 0.5 M NH3·H2O and 0.1 M S2O3 to each of the three beakers. 2- The mixture was prepared by adding 0.05 mM, 0.1 mM and 0.2 mM PDS, respectively. 1 mg of CoNC catalyst was weighed and added to the three beakers respectively. After magnetic stirring at room temperature for 6 h, the Au(I) concentration was measured and the Au(I) recovery rate was calculated.

[0072] (2) Cu-EDTA-S2O3 leaching system: Referring to experiment (1), the simulated leaching solution water quality background was changed to 5mM Cu(II), 0.01M EDTA and 0.1M S2O3 2- The recovery rate of Au(I) was calculated by keeping other test conditions consistent.

[0073] (3) Cu-EDTA-NH3-S2O3 leaching system: Referring to experiment (1), the water quality background of the simulated leaching solution was changed to 5mMCu(II), 0.01M EDTA, 0.05M NH3·H2O and 0.1M S2O3 2- The recovery rate of Au(I) was calculated by keeping other test conditions consistent.

[0074] (4) Cu-EDA-S2O3 leaching system: Referring to experiment (1), the background of the simulated leaching solution was changed to 5 mM Cu(II), 0.01 M EDA and 0.1 M S2O3 2- The pH of the mixed solution was changed to 9.5, and other test conditions remained the same, and the Au(I) recovery rate was calculated.

[0075] (5) Fe-EDTA-S2O3 leaching system: Referring to experiment (1), the simulated leaching solution water quality background was changed to 5mM Fe(III), 0.05M EDTA and 0.1M S2O3 2- The recovery rate of Au(I) was calculated by keeping other test conditions consistent.

[0076] (6) Fe-EDTA-TU-S2O3 leaching system: Referring to experiment (1), the water quality background of the simulated leaching solution was changed to 5mMFe(III), 0.05M thiourea (TU), 0.01M EDTA and 0.1M S2O3 2- The recovery rate of Au(I) was calculated by keeping other test conditions consistent.

[0077] Performance Results

[0078] 1. Structural characterization

[0079] The obtained CoNC catalyst and NC catalyst were tested by SEM, TEM and EDS using scanning electron microscope (FlexSEM1000II, Hitachi) and transmission electron microscope (JEM-3010, Hitachi). The following SEM and TEM test equipment are the same here. Figure 1 As shown, SEM and TEM results confirm that the synthesized CoNC catalyst exhibits nanoscale size and a dodecahedral structure, with no apparent particle agglomeration and good dispersion. Elemental energy dispersive spectrometry confirms that C, N, and Co are uniformly distributed within the CoNC, with atomic percentages of 94.28%, 3.46%, and 1.10%, respectively.

[0080] X-ray diffractometer (XRD-6100) was used to analyze the CoNC catalyst. The XRD equipment used here is the same. X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were also performed at the Shanghai Synchrotron Radiation Facility in transmission mode with an electron beam energy of 3.0 geoV. Sample data were analyzed using Athena and Artemis software.

[0081] The results are as follows Figure 2 As shown, Figure 2 a is the XRD result of CoNC, showing a typical amorphous graphitized structure, confirming that the CoNC catalyst does not contain Co metal, indicating that the Co supported on the NC substrate structure may be Co single atoms. Figure 2b shows that the XANES curve of CoNC is located to the right of Co foil, CoO and CoPc, where the valence state of Co element is significantly higher than the 0 valence of Co foil and only slightly higher than the +2 valence of CoPc, indicating that the valence state of Co in CoNC is between +2 and +3. Figure 2 The EXAFS images in c~d show that the Co element in CoNC is coordinated with the N atom and exists in the form of single atoms on the NC substrate, and the Co-N coordination number is 4.

[0082] 2. Removal performance

[0083] Application Example 1 and Comparative Example 1 tested the CoNC / PDS and NC / PDS systems for Au(S2O3)2 3- The recovery of Au(I) in Figure 3 As shown in the figure, it can be observed that the recovery rate of Au(I) by CoNC / PDS is significantly faster than that of NC / PDS system, and the rate constant of its kinetic model fitting (0.039min -1 ) is about 6.5 times that of the NC / PDS system. The above results indicate that the introduction of Co single atoms into the PDS catalytic system significantly improves the recovery performance of Au(I).

[0084] Application Example 1, Application Example 2 and Comparative Example 1 compare the treatment effects of CoNC on Au(I) under three different oxidants (PMS, PDS and H2O2). Figure 4 As shown, Figure 4 a is the recovery rate of Au(I) by CoNC within 300 min without adding oxidant. However, in the persulfate system, both CoNC / PMS and CoNC / PDS can effectively recover Au(I) with a recovery rate exceeding 99.5%. The kinetic rate constant of CoNC / PMS (0.066 min -1 ) was significantly higher than CoNC / PDS (0.009min -1 ). Figure 4 Figure b shows that the recovery capacities of CoNC / PMS and CoNC / PDS for Au(I) are higher than 22 g / g and 85 g / g, respectively, while the recovery capacities of CoNC / H2O2 and CoNC / blank for Au(I) are both lower than 0.1 g / g.

[0085] The above results fully confirm that the Co single atom / persulfate system has a great influence on the Au(S2O3)2 3- The rapid kinetics of Au(I) recovery and the ultra-high adsorption capacity (far exceeding the 0.1 g / g of conventional adsorbents) are considered. Considering that the recovery capacity is directly related to the technical and economic feasibility, the subsequent patent systems all use the high recovery capacity CoNC / PDS system for research.

[0086] 3. Oxidant dosage

[0087] Figure 5 The recovery kinetics of Au(I) from CoNC catalysts at different PDS dosages were compared. The researchers found that the recovery rate of Au(I) from CoNC / PDS increased with increasing PDS dosage. When the PDS concentration in the system increased to 0.3 mM, nearly 100% recovery of Au(I) was achieved within 60 minutes. Subsequent studies using the CoNC / PDS system were conducted using 0.3 mM PDS.

[0088] 4. Coexisting ions

[0089] The metal ion concentrations in the samples were determined using an Agilent inductively coupled plasma mass spectrometer (ICP-MS 7700). Figure 6 The effects of potential coexisting metal ions in the thiosulfate leaching system on the recovery of Au(I) by the CoNC / PDS system were investigated. Figure 6 As shown in Figure a, single divalent or trivalent metal ions in the solution, including Mn(II), Mg(II), Cu(II), Ni(II), Fe(III), and Al(III), have almost no effect on the recovery rate of Au(I). Even under the condition of the coexistence of six ions, the recovery rate of Au(I) by CoNC / PDS is still higher than 96.5%, which is much higher than the removal rate of the other six coexisting ions (less than 77.4%). Figure 6 As shown in b, the selectivity coefficient of CoNC / PDS for Au(I) recovery exceeds 2.0×10 9 mL / g, which is much higher than the value under pure adsorption conditions of CoNC (1.4×10 4 mL / g), and the selectivity coefficients of CoNC / PDS for the other six coexisting ions (less than 4.1×10 4 The above results fully demonstrate the excellent recovery selectivity of CoNC / PDS for Au(I) in the coexisting cation system.

[0090] Figure 7 aThe effect of coexisting anions on the recovery of Au(I) in the CoNC / PDS system was investigated. Figure 7 As shown in Figure a, single anions in the solution, including chloride, phosphate, bicarbonate, and sulfate, barely affect the recovery of Au(I). Even in the presence of all four ions, the recovery of Au(I) by CoNC / PDS remains above 99.5%.

[0091] Figure 7b The recovery performance of CoNC / PDS for Au(I) in several typical thiosulfate leaching systems was investigated. In the three systems of Cu-NH3, Cu-EDTA, Cu-EDTA-NH3 and Cu-EDA, the Au(I) recovery rate of CoNC / PDS exceeded 94.56%, and could reach 99.9% by adjusting the PDS concentration. When the PDS concentration was 0.05M, the Au(I) recovery rate of CoNC / PDS in Fe-EDTA was slightly lower than 90.0%, and could reach 93.1% by adjusting the PDS concentration. In the Fe-EDTA-TU system, due to the high affinity of thiourea (TU) for Au, the recovery of CoNC / PDS for Au(S2O3)2 3- The adsorption and decomposition effect of ions significantly improved Au(I) recovery by increasing PDS concentration and generating more oxygen reactive species (ROS). At a PDS concentration of 0.2 M, the Au(I) recovery rate reached 95.2%. These results fully demonstrate the excellent interference tolerance of the CoNC / PDS system and its good recovery ability for Au(I) in a simulated leaching system, demonstrating its potential for application in thiosulfate leachates.

[0092] 5. Active Species

[0093] To identify the recovery of Au(S2O3)2 by CoNC / PDS system 3- The key ROS species that play an oxidative decomplexation effect in the process of Au(I) in the sample were measured by Bruker electron spin resonance (Micro EPR) spectrometer.

[0094] The quenchers used in this section are: methanol, methanol:PDS molar ratio of 100:1; furfuryl alcohol, furfuryl alcohol:PDS molar ratio of 10:1; L-histidine, histidine:PDS molar ratio of 10:1; 2,2,6,6-tetramethylpiperidine, TEMP, TEMP:PDS molar ratio of 10:1; heavy water, D2O, deionized water was replaced with heavy water to prepare a 10 mg / L Au(I) aqueous solution (prepared with Na3Au(S2O3)2).

[0095] Quenching reaction method: 50 mL of 10 mg / L Au(I) deionized water solution (prepared from Na3Au(S2O3)2) and 1 mg CoCN were added to each quencher in the above amount.

[0096] Figure 8 aThe effects of various quenchers and the recovery kinetics under heavy water (D2O) conditions were investigated. The potential ROS in this system are SO4· - , OH and 1 O2. Methanol is SO4· - and ·OH, Figure 8a shows that compared with the pure water system, the addition of methanol did not inhibit the Au(I) recovery kinetics, but accelerated the reaction (related to the solvent effect), indicating that SO4· - , ·OH is not the key ROS species that dominates the decomplexation reaction in the CoNC / PDS system. 1 Further verification of the typical O2 quenchers furfuryl alcohol, L-histidine and TEMP 1 The role of O2. Figure 8 a shows that the three quenchers all significantly inhibited the recovery of Au(I), among which TEMP had the most obvious effect, which is consistent with 1 Furthermore, it was found that D2O conditions significantly accelerated the Au(I) recovery process, which was due to 1 The existence life of O2 in D2O is longer than that in H2O, which strengthens 1 O2's oxidative decomplexing ability. Figure 8 b EPR probe experiment confirmed that there is no SO4· - and ·OH, while TEMP- 1 O2 indicates that a large amount of 1 O2.

[0097] The concentration of 3,3'-(anthracene-9,10-diyl)dipropionic acid (ADPA) in the sample was determined using a UV-visible spectrophotometer (T2602) from Youke Instruments. The concentration of ADPA in the sample was determined using a Waters ultra-high performance liquid chromatography-ion mobility-quadrupole time-of-flight mass spectrometer (VION IMS QTOS). 1 APDA probe is a specific probe for rapid O2 reaction and can be used to verify the 1 O2 plays a key role. Figure 8 As shown in c, the APDA concentration in the CoNC / PDS system decreased rapidly within 30 minutes, indicating that 1 Rapid reaction of O2 and APDA. Figure 9 The ion chromatogram shown confirms 1 The above experimental characterization results fully confirm that the addition reaction of O2 and APDA in CoNC / PDS 1 O2 is the dominant ROS species. 1 The high reaction selectivity of O2 is the key reason why this system can efficiently oxidize and decomplex and selectively recover Au(I).

[0098] 6. Recycling quality

[0099] Figure 10 The chemical structure morphology of the product after CoNC / PDS recovered Au(I) was investigated. Figure 10a shows that a large number of gold nanoparticles are newly generated on the surface of the CoNC catalyst, indicating that the recovered Au(I) form is mainly gold. This is further confirmed by Figure 10 As confirmed by the XRD spectrum of b, Figure 10 b shows that the material after the reaction presents the (111), (200) and (220) peaks of zero-valent Au. By calcining the material after the reaction, we can obtain a high-purity gold product (tested by GB / T 38145-2019, the purity exceeds 99.8%). Figure 10 c is the XRD spectrum of the obtained gold product, and the sharp peak shape confirms its high purity.

Claims

1. Application of cobalt-catalyzed activation of persulfate in the recovery of gold from thiosulfate leachate, characterized in that: Cobalt catalyst, persulfate and Au(S2O3)2 3- The gold is mixed with thiosulfate leachate and the gold is reduced by breaking the complex.

2. The use according to claim 1, characterized in that Au(S2O3)2 3- Under the action of singlet oxygen, the gold-sulfur bond is opened, and the complex is broken and reduced to obtain gold element.

3. The use according to claim 1, wherein The Au(S2O3)2 3- The recovery rate of gold is ≥99.0%, and the purity of the gold element is ≥99.5%.

4. The use according to claim 1, wherein Cobalt catalyst, persulfate and Au(S2O3)2 3- The mass ratio between them is 2:(10~25):(1~80).

5. The use according to claim 1, characterized in that The Au(S2O3)2 3- The thiosulfate leachate includes: Mn 2+ Mg 2+ 、Cu 2+ 、Ni 2+ 、Fe 2+ 、Al 2+ 、Cl - PO4 3- 、HCO3 2- 、SO4 2- At least one of .

6. The use according to claim 1, wherein The persulfate is potassium peroxymonosulfate and / or potassium peroxydisulfate.

7. The use according to claim 1, wherein The cobalt catalyst is obtained by chemical vapor deposition by reacting a precursor obtained by calcining a ZnCo-ZIF material with ammonium chloride at 800-900° C. for 1-2 hours under an inert atmosphere.

8. The use according to claim 7, characterized in that Cobalt salt, zinc salt and 2-methylimidazole are mixed in methanol, stirred, centrifuged and dried to obtain ZnCo-ZIF material; under an inert atmosphere, the ZnCo-ZIF material is calcined at 850-950°C at a rate of 5°C / min for 2-4h to obtain a precursor.

9. The use according to any one of claims 7 or 8, characterized in that The precursor is placed at one end close to the inert atmosphere inlet, and the ammonium chloride is placed at one end away from the inert atmosphere inlet.

10. The use according to claim 9, characterized in that The mass ratio of the precursor to ammonium chloride is 1:(10-50).

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