Method for continuous determination of gold, silver, copper, lead and zinc in gold-based alloys

Abstract

The application provides a method for continuously determining gold, silver, copper, lead and zinc in a gold-based alloy, and belongs to the technical field of gold alloy element content detection. The method is based on the combination of the weight method, the electrolysis method and the titration method, and is based on the chemical means such as extraction, back extraction, electrochemistry and complex reaction, and through one-time sample weighing and sample digestion, the continuous and accurate determination of gold, silver, copper, lead and zinc in the gold-based alloy can be realized, the efficiency is improved, the complexity of multiple treatments is reduced, and the method is accurate and reliable. Through the targeted selection of different masking agents, buffer reagents and precipitating agents used one by one in one solution, the problems of unsuitable element method, determination out of range and mutual interference between elements are solved.

Description

Technical Field

[0001] This invention relates to the field of gold alloy element content detection technology, specifically to a method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys. Background Technology

[0002] The detection of gold, silver, copper, lead, and zinc in gold-based alloys mainly includes instrumental methods such as inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and atomic absorption spectrometry (AAS), as well as some wet chemical analysis methods. From the perspective of detection methods, none of these methods are specifically designed for the determination of gold-based alloys, a particular type of five-element alloy. These methods suffer from drawbacks such as mutual interference between the gold, silver, copper, lead, and zinc matrices, making continuous measurement impossible; requiring multiple samplings and testing by multiple methods one by one; consuming large amounts of sample; long operation procedures; and poor repeatability and reproducibility.

[0003] Continuous determination refers to the determination of each element to be measured by different chemical treatments on a digested sample. The above methods can only determine a single value for a specific element and cannot perform continuous determination of gold, silver, copper, lead, and zinc. They can only achieve single-element determination by a single method such as instrumental method, gravimetric method, or volumetric method. To determine all five elements of gold, silver, copper, lead, and zinc, it is often necessary to use 4-5 or more methods, and to repeatedly weigh and digest the sample, which is a long and complicated operation. The patents CN114878565A, "A Method for Determining High Contents of Copper, Lead, and Zinc in Polymetallic Minerals and Copper-Lead-Zinc Alloys," and CN114739983A, "A Method for Determining High Contents of Copper, Lead, and Zinc in Polymetallic Minerals and Copper-Lead-Zinc Alloys Using ICP-AES," mention the continuous determination of copper, lead, and zinc. By treating the sample through digestion or precipitation, the copper, lead, and zinc elements to be measured exist in the solution in ionic form. Then, each element is separated and tested individually. Although this experiment tested the determination of copper, lead, and zinc, there is no correlation between the methods, and it is not a continuous determination of a single sample. Essentially, it is equivalent to the accumulation of multiple independent methods. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a method for continuous determination of gold, silver, copper, lead and zinc in gold-based alloys, aiming to solve the problem that there is no suitable method for determining gold, silver, copper, lead and zinc in existing gold-based alloys and the determination results are highly inconsistent.

[0005] This application provides a method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys, comprising the following steps:

[0006] S1. Sample digestion

[0007] The sample to be tested is digested to obtain the test solution;

[0008] S2. Determination of Gold

[0009] A mixture of ethyl acetate and methyl isobutyl ketone was added to the test solution, and the solution was extracted. Then, solid-liquid separation was performed to obtain an aqueous phase and an organic phase after extraction. The organic phase after extraction was then subjected to oxidation-reduction treatment and filtered to obtain a gold-rich filter residue and filtrate. The gold-rich filter residue was then smelted to obtain gold, and the gold content was finally calculated.

[0010] S3. Determination of Silver

[0011] The aqueous phase after extraction was acid-treated, followed by the addition of potassium cyanide. The silver content was then determined by titration using the Volhart method.

[0012] S4. Determination of Copper

[0013] The solution after titration in step S3 is filtered, then acid-treated, followed by the addition of tartaric acid, and then electrolyzed using a constant potential electrolysis method to obtain the electrolyte and calculate the copper content.

[0014] S5. Determination of Lead

[0015] Concentrated sulfuric acid was added to the electrolyte after electrolysis in step S4, heated to boiling, cooled and filtered to obtain lead sulfate precipitate and filtrate II. Acetic acid-ammonium acetate was added to the lead sulfate precipitate and heated until the lead sulfate precipitate was completely dissolved. The lead content was calculated by EDTA titration.

[0016] S6. Determination of Zinc

[0017] Add ammonium chloride, ammonium persulfate and ammonia to filtrate two in step S5, heat to a gentle boil and filter immediately to obtain precipitate and filtrate three. Add ammonium acetate-acetic acid and potassium fluoride to filtrate three and calculate the zinc content by EDTA titration.

[0018] In the technical solution of this application embodiment, by combining gravimetric, electrolytic, and titration methods, and based on chemical techniques such as extraction and back-extraction, electrochemistry, and complexation reactions, the continuous and accurate determination of gold, silver, copper, lead, and zinc in gold-based alloys can be achieved through a single sample weighing and digestion. This improves efficiency, reduces the complexity of multiple processing steps, and ensures the method's accuracy and reliability. The combined extraction-reduction method, electrochemical precipitation method, redox method, and complexometric titration method, by adding different masking agents, buffer reagents, and precipitants in a single solution, solves the problems of inapplicability of elemental methods, measurement exceeding the specified range, and mutual interference between elements.

[0019] In some embodiments, step S1 specifically includes the following steps: weigh 1.0~3.0g of sample, add 20~50ml of ethanol solution, sonicate for 10~20min, then add 10~20ml of nitric acid, digest until no bubbles are generated, then add 15~30ml of hydrochloric acid until the sample is completely dissolved and concentrated to 1~2ml, add 3~5ml of 50% citric acid, and then add 30~50ml of water for leaching.

[0020] In this embodiment, citric acid is added during digestion. Citric acid acts as a complexing stabilizer, and the carboxyl group of citric acid forms a coordination bond with copper, lead, and zinc to form a hydrophilic copper / lead / zinc citrate complex, which remains in the aqueous phase. This ensures that no element is lost in the subsequent analytes without affecting the organic extraction of gold in the first step.

[0021] In some embodiments, step S2 specifically includes the following steps: adding 30-50 ml of a mixed solution of ethyl acetate and methyl isobutyl ketone to the test solution, extracting for 1-2 min, then separating the solid and liquid phases to obtain organic phase 1 and aqueous phase 1. Repeating the above extraction steps on aqueous phase 1 to obtain organic phase 2 and aqueous phase 2. Aqueous phase 2 is used as the aqueous phase after extraction for subsequent operations. Combining organic phase 1 and organic phase 2 to obtain the extracted organic phase. Adding 200-300 ml of water to the extracted organic phase, then adding 1-2 ml of hydrochloric acid and heating to boiling, while hot, adding 1-2 g of thiourea, heating at 100-120°C for 10-15 min, and while hot, gradually adding sodium sulfite until no more precipitation occurs. Filtering to obtain gold-rich filter residue and filtrate 1. Melting the gold-rich filter residue to obtain gold, and finally calculating the gold content; the volume ratio of ethyl acetate to methyl isobutyl ketone is 1:2.

[0022] In this embodiment, a mixed organic extraction system of ethyl acetate and methyl isobutyl ketone was constructed to extract gold. When the volume ratio of ethyl acetate to methyl isobutyl ketone was 1:2, the gold recovery rate reached over 99.9% at an acidity of 1 mol / L. When the ratio was greater than 1:2, gold could not be completely extracted. When the ratio was less than 1:2, the proportion of methyl isobutyl ketone continued to increase, and the evaporation rate became faster and faster. Since the operation involved multiple digestions and repeated extractions, coupled with the influence of the digestion solution temperature, excessively rapid evaporation would lead to inconsistent amounts of extractant and a decrease in extraction efficiency, resulting in poor precision and low recovery rate.

[0023] In some embodiments, the amount of sodium sulfite added each time is no more than 0.10g.

[0024] In this embodiment, sodium sulfite is added in small amounts one at a time, utilizing sulfite ions (SO3) 2- ) will oxidize trivalent gold ions (Au) 3+It is reduced to elemental gold in order to achieve the purpose of determining gold by gravimetric method.

[0025] In some embodiments, step S3 specifically includes the following steps: concentrating the filtrate to 50 ml, then adding 10-20 ml of nitric acid, heating for 5-10 min, then adding 0.5 g of potassium cyanide, and titrating the silver using the Volhart method to calculate the silver content.

[0026] In this embodiment, the Volhart method is used, with potassium thiocyanate as the titrant and ferric ammonium vanadium as the indicator. Because Ag... + With SCN - The binding capacity is much greater than that of Fe 3+ Strong, after the AgSCN precipitation reaction is complete, excess Fe 3+ With SCN - The reaction produces Fe(SCN)6 3- (Red) indicates the endpoint. During titration, small amounts of copper and lead participate in the reaction, which are masked by the addition of potassium cyanide. Excess potassium cyanide reacts with copper and lead to form the extremely stable copper-cyanide complex [Cu(CN)4]. 3- and lead-cyanide complex [Pb(CN)4] 3- At this point, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be formed, and copper and lead do not participate in the reaction. On the other hand, to create a stable electrolytic environment for the next step of copper content determination-electrolysis, the complexation reaction can avoid the hydrolysis of copper ions, avoid the decrease in conductivity caused by precipitation due to hydrolysis, and at the same time inhibit anodic passivation. Potassium cyanide forms a stable complex with copper ions at the anode (such as Cu(CN)3). 2- This reduces the accumulation of oxide layer on the anode surface, prevents the formation of passivation film, and maintains efficient anode electrolysis.

[0027] In some embodiments, step S4 specifically includes the following steps: filtering the solution titrated in step S3, adding 5-20 ml of nitric acid to the filtrate, heating to a gentle boil, then adding 0.5 g of tartaric acid, and adding water to a volume of 300 ml. Electrolysis is then performed using a constant potential electrolysis method. After electrolysis, the cathode electrode is removed, immersed in an ethanol solution to remove copper, then removed, dried, and weighed to calculate the copper content. During electrolysis, the electrolysis current is 5 A, and the cathode potential is 0.34 V. The electrolysis time is 30-60 min.

[0028] In this embodiment, a constant potential electrolysis method is used to improve the accuracy and sensitivity of copper electrolysis. During the electrolysis process, copper ions are reduced to elemental copper at the cathode and deposited. As elemental copper is deposited at the cathode, small amounts of iron and zinc are electrolyzed and mixed in with the cathode copper, affecting the results. Tartaric acid is introduced into the electrolysis solution system. Tartaric acid is a dibasic organic acid containing two carboxyl groups and two hydroxyl groups, which can react with metal ions (such as Fe). 3+ Zn 2+ It forms a stable complex that masks iron and zinc, while also preventing the hydrolysis of copper.

[0029] In some embodiments, step S5 specifically includes the following steps: concentrating the electrolyte in step S4 to 70-80 ml, adding 10-20 ml of concentrated sulfuric acid, heating to boiling, cooling and filtering to obtain lead sulfate precipitate and filtrate II, adding 30-100 ml of acetic acid-ammonium acetate to the lead sulfate precipitate, heating until the lead sulfate precipitate is completely dissolved, and calculating the lead content using EDTA titration.

[0030] In this embodiment, the determination of lead is based on a complexation reaction and employs EDTA titration. The reaction that occurs is as follows: Colorimetric reaction: Pb2 + +Xylenol orange → purple-red complex, complexometric titration reaction: Pb 2+ +EDTA4-→Pb-EDTA 2- .

[0031] In some embodiments, step S6 specifically includes the following steps: concentrating filtrate two from step S5 to 50-80 ml, adding 3-5 g ammonium chloride, 0.5-1 g ammonium persulfate and 20-40 ml ammonia water, heating to a gentle boil and filtering immediately to obtain precipitate and filtrate three, concentrating filtrate three to 100 ml, adding 10-30 ml ammonium acetate-acetic acid and 5 ml potassium fluoride with a concentration of 50-100 g / L, and calculating the zinc content by EDTA titration.

[0032] In this embodiment, zinc was determined based on a complexation reaction using EDTA titration. During the titration, iron was masked using potassium fluoride. The masking reaction was: Fe... 3+ +6F - →FeF6 3- .

[0033] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Detailed Implementation

[0034] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0036] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0037] To address the lack of suitable methods and significant discrepancies in existing determinations of gold, silver, copper, lead, and zinc in gold-based alloys, this application provides a method for the continuous determination of these five elements in gold-based alloys. By combining gravimetric, electrolytic, and titration methods, and based on chemical techniques such as extraction and back-extraction, electrochemistry, and complexation reactions, this method achieves continuous and accurate determination of gold, silver, copper, lead, and zinc in gold-based alloys through a single sample weighing and digestion process. This improves efficiency, reduces the complexity of multiple processing steps, and ensures the method's accuracy and reliability. In this process, citric acid was added during digestion. Citric acid acts as a complexing stabilizer; its carboxyl groups form coordinate bonds with copper, lead, and zinc, creating hydrophilic copper / lead / zinc citrate complexes that remain in the aqueous phase. This ensures no loss of subsequent analytes without affecting the organic extraction of gold in the first step. A mixed organic extraction system using ethyl acetate and methyl isobutyl ketone was constructed to extract gold. At a volume ratio of 1:2 for ethyl acetate to methyl isobutyl ketone and an acidity of 1 mol / L, the gold recovery rate reached over 99.9%. For silver determination, potassium cyanide was added for masking. Excess potassium cyanide reacts with copper and lead to form extremely stable copper-cyanide complexes [Cu(CN)4]. 3- and lead-cyanide complex [Pb(CN)4] 3-At this point, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be formed, and copper and lead do not participate in the reaction. On the other hand, to create a stable electrolytic environment for the next step of copper content determination-electrolysis, the complexation reaction can avoid the hydrolysis of copper ions, avoid the decrease in conductivity caused by precipitation due to hydrolysis, and at the same time inhibit anodic passivation. Potassium cyanide forms a stable complex with copper ions at the anode (such as Cu(CN)3). 2- This reduces oxide buildup on the anode surface, prevents passivation film formation, and maintains efficient anode electrolysis. During copper electrolysis, tartaric acid is introduced into the electrolyte solution system. Tartaric acid contains two carboxyl groups and two hydroxyl groups, which can react with metal ions (such as Fe). 3+ Zn 2+ This method forms stable complexes to mask iron and zinc, while also preventing the hydrolysis of copper. In the determination of zinc, iron is masked using potassium fluoride. This application combines extraction-reduction, electrochemical precipitation, redox, and complexometric titration methods. By adding different masking agents, buffers, and precipitants in a single solution, it solves the problems of unsuitability of elemental methods, exceeding the measurement range, and the inability to continuously measure elements due to mutual interference.

[0038] This application provides a method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys, comprising the following steps:

[0039] S1. Sample digestion

[0040] The sample to be tested is digested to obtain the test solution;

[0041] S2. Determination of Gold

[0042] A mixture of ethyl acetate and methyl isobutyl ketone was added to the test solution, and the solution was extracted. Then, solid-liquid separation was performed to obtain an aqueous phase and an organic phase after extraction. The organic phase after extraction was then subjected to oxidation-reduction treatment and filtered to obtain a gold-rich filter residue and filtrate. The gold-rich filter residue was then smelted to obtain gold, and the gold content was finally calculated.

[0043] S3. Determination of Silver

[0044] The aqueous phase after extraction was acid-treated, followed by the addition of potassium cyanide. The silver content was then determined by titration using the Volhart method.

[0045] S4. Determination of Copper

[0046] The solution after titration in step S3 is filtered, then acid-treated, followed by the addition of tartaric acid, and then electrolyzed using a constant potential electrolysis method to obtain the electrolyte and calculate the copper content.

[0047] S5. Determination of Lead

[0048] Concentrated sulfuric acid was added to the electrolyte after electrolysis in step S4, heated to boiling, cooled and filtered to obtain lead sulfate precipitate and filtrate II. Acetic acid-ammonium acetate was added to the lead sulfate precipitate and heated until the lead sulfate precipitate was completely dissolved. The lead content was calculated by EDTA titration.

[0049] S6. Determination of Zinc

[0050] Add ammonium chloride, ammonium persulfate and ammonia to filtrate two in step S5, heat to a gentle boil and filter immediately to obtain precipitate and filtrate three. Add ammonium acetate-acetic acid and potassium fluoride to filtrate three and calculate the zinc content by EDTA titration.

[0051] In the technical solution of this application embodiment, by combining gravimetric, electrolytic, and titration methods, and based on chemical techniques such as extraction and back-extraction, electrochemistry, and complexation reactions, the continuous and accurate determination of gold, silver, copper, lead, and zinc in gold-based alloys can be achieved through a single sample weighing and digestion. This improves efficiency, reduces the complexity of multiple processing steps, and ensures the method's accuracy and reliability. The combined extraction-reduction method, electrochemical precipitation method, redox method, and complexometric titration method, by adding different masking agents, buffer reagents, and precipitants in a single solution, solves the problems of inapplicability of elemental methods, measurement exceeding the specified range, and mutual interference between elements.

[0052] Further, in some embodiments, step S1 specifically includes the following steps: weigh 1.0~3.0g of sample, add 20~50ml of ethanol solution, sonicate for 10~20min, then add 10~20ml of nitric acid, digest until no bubbles are generated, then add 15~30ml of hydrochloric acid until the sample is completely dissolved and concentrated to 1~2ml, add 3~5ml of 50% citric acid, and then add 30~50ml of water for leaching.

[0053] In the technical solution of this application embodiment, by adding citric acid during digestion, citric acid acts as a complexing stabilizer. The carboxyl group of citric acid forms a coordination bond with copper, lead, and zinc to form a hydrophilic copper / lead / zinc citrate complex, which then remains in the aqueous phase. This ensures that the elements to be measured are not lost without affecting the organic extraction of gold in the first step.

[0054] Further, in some embodiments, step S2 specifically includes the following steps: adding 30-50 ml of a mixed solution of ethyl acetate and methyl isobutyl ketone to the test solution, extracting for 1-2 min, then separating the solid and liquid phases to obtain organic phase 1 and aqueous phase 1. Repeating the above extraction steps on aqueous phase 1 to obtain organic phase 2 and aqueous phase 2. Aqueous phase 2 is used as the aqueous phase after extraction for subsequent operations. Combining organic phase 1 and organic phase 2 to obtain the extracted organic phase. Adding 200-300 ml of water to the extracted organic phase, then adding 1-2 ml of hydrochloric acid and heating to boiling. While hot, adding 1-2 g of thiourea and heating at 100-120°C for 10-15 min. While hot, adding sodium sulfite sequentially until no more precipitate is produced. Filtering to obtain gold-rich filter residue and filtrate 1. Melting the gold-rich filter residue to obtain gold, and finally calculating the gold content; the volume ratio of ethyl acetate to methyl isobutyl ketone is 1:2.

[0055] In the technical solution of this application embodiment, a mixed organic extraction system of ethyl acetate and methyl isobutyl ketone was constructed to extract gold. When the volume ratio of ethyl acetate to methyl isobutyl ketone is 1:2, the gold recovery rate reaches more than 99.9% at an acidity of 1 mol / L. When the ratio is greater than 1:2, gold cannot be completely extracted. When the ratio is less than 1:2, the proportion of methyl isobutyl ketone continues to increase, and the volatilization rate becomes faster and faster. Since the operation involves multiple digestions and repeated extractions, coupled with the influence of the digestion solution temperature, excessively rapid volatilization will lead to inconsistent amounts of extractant and a decrease in extraction efficiency, resulting in poor precision and low recovery rate.

[0056] Furthermore, in some embodiments, the melting of the gold-rich filter residue specifically includes the following steps: adding a small amount of borax and sodium carbonate protective agent to a porcelain crucible and melting at 1100°C for 10-15 minutes.

[0057] Furthermore, in some embodiments, the amount of sodium sulfite added each time is no more than 0.10g.

[0058] In the technical solution of this application embodiment, sodium sulfite is added in small amounts one at a time, utilizing sulfite ions (SO3) 2- ) will oxidize trivalent gold ions (Au) 3+ It is reduced to elemental gold in order to achieve the purpose of determining gold by gravimetric method.

[0059] Furthermore, in some embodiments, step S3 specifically includes the following steps: concentrating the filtrate to 50 ml, then adding 10-20 ml of nitric acid, heating for 5-10 min, then adding 0.5 g of potassium cyanide, and titrating the silver using the Volhart method to calculate the silver content.

[0060] Furthermore, in some embodiments, the Volhart method specifically includes the following steps: adding 1-2 mL of ferric ammonium sulfate indicator, titrating with potassium thiocyanate standard solution, and titrating until a light pink color is obtained as the titration endpoint.

[0061] In the technical solution of this application embodiment, the Volhart method is adopted, with potassium thiocyanate as the titrant and ferric ammonium vanadium as the indicator. Because Ag... + With SCN - The binding capacity is much greater than that of Fe 3+ Strong, after the AgSCN precipitation reaction is complete, excess Fe 3+ With SCN - The reaction produces Fe(SCN)6 3- (Red) indicates the endpoint. During titration, small amounts of copper and lead participate in the reaction, which are masked by the addition of potassium cyanide. Excess potassium cyanide reacts with copper and lead to form the extremely stable copper-cyanide complex [Cu(CN)4]. 3- and lead-cyanide complex [Pb(CN)4] 3- At this point, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be formed, and copper and lead do not participate in the reaction. On the other hand, to create a stable electrolytic environment for the next step of copper content determination-electrolysis, the complexation reaction can avoid the hydrolysis of copper ions, avoid the decrease in conductivity caused by precipitation due to hydrolysis, and at the same time inhibit anodic passivation. Potassium cyanide forms a stable complex with copper ions at the anode (such as Cu(CN)3). 2- This reduces the accumulation of oxide layer on the anode surface, prevents the formation of passivation film, and maintains efficient anode electrolysis.

[0062] Further, in some embodiments, step S4 specifically includes the following steps: filtering the solution titrated in step S3, adding 5-20 ml of nitric acid to the filtrate, heating to a gentle boil, then adding 0.5 g of tartaric acid and adding water to a volume of 300 ml. Electrolysis is then performed using a constant potential electrolysis method. After electrolysis, the cathode electrode is removed, immersed in an ethanol solution to remove copper, then removed, dried, and weighed to calculate the copper content. During electrolysis, the electrolysis current is 5 A, and the cathode potential is 0.34 V. The electrolysis time is 30-60 min.

[0063] Furthermore, in some embodiments, the constant potential electrolysis method specifically includes the following steps: the weighed mesh platinum cathode, platinum anode, and gancourt electrode are placed in the solution and connected to the copper electrolysis equipment. The uniform stirring mode is turned on, the cathode potential is controlled at 0.34V, and electrolysis is performed with a current of 5A. When the electrolysis current drops below 200mA and electrolysis continues for 20 minutes without any new copper deposition on the electrode surface, the cathode is removed from the solution without interrupting the current.

[0064] In the technical solution of this application embodiment, a constant potential electrolysis method is used to improve the accuracy and sensitivity of copper electrolysis. During the electrolysis process, copper ions are reduced to elemental copper at the cathode and deposited. As elemental copper is deposited at the cathode, a small amount of iron and zinc are electrolyzed and mixed in with the cathode copper, affecting the results. Tartaric acid is introduced into the electrolysis solution system. Tartaric acid is a dibasic organic acid containing two carboxyl groups and two hydroxyl groups, which can react with metal ions (such as Fe). 3+ Zn 2+ It forms a stable complex that masks iron and zinc, while also preventing the hydrolysis of copper.

[0065] Further, in some embodiments, step S5 specifically includes the following steps: concentrating the electrolyte in step S4 to 70-80 ml, adding 10-20 ml of concentrated sulfuric acid, heating to boiling, cooling and filtering to obtain lead sulfate precipitate and filtrate II, adding 30-100 ml of acetic acid-ammonium acetate to the lead sulfate precipitate, heating until the lead sulfate precipitate is completely dissolved, and calculating the lead content using EDTA titration.

[0066] Furthermore, in some embodiments, the EDTA titration method for calculating the lead content specifically includes the following steps: adding 3-6 drops of xylenol orange and titrating with Na2EDTA standard titration solution until a bright yellow color is obtained.

[0067] In the technical solution of this application embodiment, the determination of lead is based on a complexation reaction and uses EDTA titration. The reaction that occurs is as follows: Colorimetric reaction: Pb2 + +Xylenol orange → purple-red complex, complexometric titration reaction: Pb 2+ +EDTA4-→Pb-EDTA 2- .

[0068] Further, in some embodiments, step S6 specifically includes the following steps: concentrating filtrate two from step S5 to 50-80 ml, adding 3-5 g ammonium chloride, 0.5-1 g ammonium persulfate and 20-40 ml ammonia water, heating to a gentle boil and filtering immediately to obtain precipitate and filtrate three, concentrating filtrate three to 100 ml, adding 10-30 ml ammonium acetate-acetic acid and 5 ml potassium fluoride with a concentration of 50-100 g / L, and calculating the zinc content by EDTA titration.

[0069] Furthermore, in some embodiments, the EDTA titration method for calculating the zinc content specifically includes the following steps: adding 3-6 drops of xylenol orange as an indicator, and titrating with Na2EDTA standard titration solution until a bright yellow color is obtained.

[0070] In the technical solution of this application embodiment, the determination of zinc is based on a complexation reaction and employs EDTA titration. During the titration process, iron is masked using potassium fluoride; the masking reaction is: Fe 3+ +6F - →FeF6 3- .

[0071] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0072] Example 1

[0073] This embodiment provides a method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys, specifically including the following steps:

[0074] Weigh 3.0g of sample into a beaker, add 30ml of ethanol solution, sonicate for 20min, add 20ml of nitric acid, digest until no bubbles are produced, add 30ml of hydrochloric acid, continue digestion until completely dissolved, concentrate to 2ml, add 5ml of 50% citric acid, and then add 50ml of water to leach out, to obtain the test solution.

[0075] Transfer the test solution to a separatory funnel, add 50 ml of ethyl acetate and methyl isobutyl ketone (volume ratio 1:1), extract thoroughly for 2 min, and allow to stand for separation. Transfer the aqueous phase to another separatory funnel, add 50 ml of ethyl acetate and methyl isobutyl ketone (volume ratio 1:2) again, extract again for 2 min, and allow to stand for separation. Combine the organic phases from the two extractions and place them in a beaker. Add 200 ml of water and 2 ml of hydrochloric acid, heat to a gentle boil, add 3 g of thiourea while hot, heat at 100℃ for 15 min, and add 0.1 g of sodium sulfite sequentially while hot. After the gold is completely reduced to a precipitate, allow to stand for 10 min, then filter to obtain gold-rich filter residue and filtrate one. Place the gold-rich filter residue along with the filter paper in a porcelain crucible, add a small amount of borax and sodium carbonate as a protective agent, and melt at 1100℃ for 15 min. After cooling, weigh and calculate the gold content.

[0076] Gold content calculation:

[0077] W Au =m Au / m*100%

[0078] In the formula:

[0079] W Au —The mass fraction of gold, expressed as a percentage (%).

[0080] m Au —The mass of gold after roasting, in grams (g).

[0081] m — Sample mass, in g.

[0082] The aqueous phase from the second extraction was concentrated to 50 ml by heating, 20 ml of nitric acid was added, and the mixture was heated for 10 min. 0.5 g of potassium cyanide was added, and the mixture was cooled to room temperature. The entire reaction was carried out in a fume hood. Then, 2 mL of ferric ammonium sulfate indicator was added, and the mixture was titrated with potassium thiocyanate standard solution until the test sample turned pale red, which was the titration endpoint. The silver content was then calculated.

[0083] Silver content calculation:

[0084] W Ag =(C Ag *(V1-V0)*M Ag ) / (m*1000))*100%

[0085] In the formula:

[0086] W Ag —The mass fraction of silver, expressed as a percentage (%);

[0087] C Ag —The actual concentration of the potassium thiocyanate standard titration solution, in moles per liter (mol / L).

[0088] V1—The actual volume of potassium thiocyanate standard titration solution consumed, in milliliters (mL).

[0089] V0—The volume of potassium thiocyanate standard titration solution consumed by the blank solution, in milliliters (mL).

[0090] M Ag —Molar mass of silver, in grams per mole (g / mol).

[0091] m — Sample mass, in grams (g).

[0092] Filter the titrated solution, add 20 ml of nitric acid, heat to a gentle boil, add 0.5 g of tartaric acid, remove and cool to room temperature, add water to a volume of 300 ml, place the weighed mesh platinum cathode, platinum anode, and Gangon electrode into the solution, connect to the copper electrolysis equipment, turn on the uniform stirring mode, control the cathode potential at 0.34 V, electrolyze with a current of 5 A, wait until the electrolysis current drops below 200 mA, and continue electrolysis for 20 min without new copper deposition on the electrode surface, remove the cathode from the solution without interrupting the current, slowly immerse the cathode in an ethanol solution, take it out, dry it, weigh it, and calculate the copper content;

[0093] Copper content calculation:

[0094] W Cu =m Cu / m*100%

[0095] In the formula:

[0096] W Cu —Copper mass fraction, expressed as a percentage (%).

[0097] m Cu —The mass of copper after reduction, in grams (g);

[0098] m — Sample mass, in g.

[0099] Concentrate the above electrolyte to 80 ml, add 20 ml of concentrated sulfuric acid, heat to boiling, cool and filter to obtain lead sulfate precipitate and filtrate 2. Add 80 ml of acetic acid-ammonium acetate to the lead sulfate precipitate, heat until the lead sulfate precipitate is completely dissolved, add 3-6 drops of xylenol orange, and titrate with Na2EDTA standard titration solution until bright yellow, and calculate the lead content.

[0100] Lead content calculation:

[0101] W Pb =(C Pb *(V2-V3)*M Pb ) / (m*1000))*100%

[0102] In the formula:

[0103] W Pb —The mass fraction of lead, expressed as a percentage (%);

[0104] C Pb —The actual concentration of the EDTA standard titration solution, in moles per liter (mol / L).

[0105] V2—The actual volume of EDTA standard titration solution consumed, in milliliters (mL);

[0106] V3 — The volume of EDTA standard titration solution consumed by the blank solution, in milliliters (mL);

[0107] M Pb — Molar mass of lead, expressed in grams per mole (g / mol).

[0108] m — Sample mass, in grams (g).

[0109] Concentrate the above filtrate 2 to 580 ml, add 5 g ammonium chloride, 1 g ammonium persulfate and 40 ml ammonia water, heat to a gentle boil and filter immediately to obtain precipitate and filtrate 3. Concentrate filtrate 3 to 100 ml, add 30 ml ammonium acetate-acetic acid and 5 ml potassium fluoride with a concentration of 80 g / L, titrate with Na2EDTA standard titration solution until bright yellow, and calculate the zinc content;

[0110] Zinc content calculation:

[0111] W Zn =(C Zn *(V4-V5)*M Zn ) / (m*1000))*100%

[0112] In the formula:

[0113] W Zn —The mass fraction of zinc, expressed as a percentage (%);

[0114] C Zn —The actual concentration of the EDTA standard titration solution, in moles per liter (mol / L).

[0115] V4—The actual volume of EDTA standard titration solution consumed, in milliliters (mL).

[0116] V5 — The volume of EDTA standard titration solution consumed by the blank solution, in milliliters (mL);

[0117] M Zn —The molar mass of zinc, expressed in grams per mole (g / mol).

[0118] m — Sample mass, in grams (g).

[0119] The sources and performance parameters of the raw materials are as follows:

[0120] Laboratory quality control sample HJ-1 was selected as the test sample, and its values ​​are shown in Table 1.

[0121] Table 1 HJ-1 Measurement Table

[0122]

[0123] Comparative Examples 1-5

[0124] Comparative Examples 1-5 provide a method for the continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys. The difference from Example 1 is that the volume ratio of ethyl acetate to methyl isobutyl ketone is different in the determination of gold, as shown in Table 2 below. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0125] Table 2 shows the volume ratio of ethyl acetate to methyl isobutyl ketone and the gold recovery rate in Examples 1 and Comparative Examples 1-5.

[0126]

[0127] Table 2 shows that as the proportion of methyl isobutyl ketone gradually increases, the gold extraction recovery rate gradually increases. When the ratio reaches 1:1, there is no obvious yellow color in the extraction solution, and the gold extraction rate is significantly improved. When the ratio is 1:2, the extraction effect is the best, the extraction rate is the highest, and the gold extraction recovery rate reaches 99.95%. However, as the proportion of methyl isobutyl ketone continues to increase, the volatilization rate becomes faster and faster. Since the operation involves multiple digestions and repeated extractions, coupled with the influence of the digestion solution temperature, excessively rapid volatilization will lead to inconsistent amounts of extractant and a decrease in extraction efficiency, resulting in poor precision and low recovery rate.

[0128] Comparative Example 6

[0129] This comparative example provides a method for the continuous determination of gold, silver, copper, lead and zinc in gold-based alloys. The difference from Example 1 is that potassium cyanide was not added in the measurement of silver. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0130] Table 3 shows the determination results of gold, silver, copper, lead, and zinc in Example 1 and Comparative Example 6.

[0131]

[0132] Table 3 shows that without the addition of potassium cyanide, the silver results were too high, while the results for copper, lead, and zinc were too low. The determination results for gold, silver, copper, lead, and zinc in Example 1 were basically consistent with the specified values. The addition of potassium cyanide serves two purposes: firstly, it ensures the accuracy of the silver results; secondly, excess potassium cyanide reacts with copper and lead to form extremely stable copper-cyanide complexes [Cu(CN)4]. 3- and lead-cyanide complex [Pb(CN)4] 3- At this point, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be formed. Copper and lead do not participate in the reaction, thus ensuring the accuracy of the silver, copper, and lead results. Secondly, it creates a stable electrolytic environment for the next step of copper content determination—electrolysis. The complexation reaction avoids the hydrolysis of copper ions, preventing the decrease in conductivity caused by precipitation due to hydrolysis, and simultaneously inhibits anodic passivation. Potassium cyanide forms a stable complex with the copper ions at the anode (such as Cu(CN)3). 2- This reduces oxide buildup on the anode surface, prevents passivation film formation, maintains efficient anode electrolysis, and ensures accurate copper results.

[0133] To further verify the accuracy of this scheme, two national standard reference materials, GBW(E)020240 and GBW(E)020241, were used as test samples. The mass values ​​and uncertainties of the standard reference materials are shown in Table 4.

[0134] Table 4. Standard Material Quality Values ​​and Uncertainties

[0135]

[0136] The test was conducted according to the method in Example 1, and the test results are shown in Table 5.

[0137] Table 5 Test Results

[0138]

[0139] As can be seen from Table 5, the test results of this scheme are basically consistent with the composition of the standard sample.

[0140] In summary, this application provides a method for the continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys. By combining gravimetric, electrolytic, and titration methods, and based on chemical techniques such as extraction and back-extraction, electrochemistry, and complexation reactions, the method achieves continuous and accurate determination of gold, silver, copper, lead, and zinc in gold-based alloys through a single sample weighing and digestion process. This improves efficiency, reduces the complexity of multiple processing steps, and ensures the method's accuracy and reliability. In this process, citric acid was added during digestion. Citric acid acts as a complexing stabilizer; its carboxyl groups form coordinate bonds with copper, lead, and zinc, creating hydrophilic copper / lead / zinc citrate complexes that remain in the aqueous phase. This ensures no loss of subsequent analytes without affecting the organic extraction of gold in the first step. A mixed organic extraction system using ethyl acetate and methyl isobutyl ketone was constructed to extract gold. At a volume ratio of 1:2 for ethyl acetate to methyl isobutyl ketone and an acidity of 1 mol / L, the gold recovery rate reached over 99.9%. For silver determination, potassium cyanide was added for masking. Excess potassium cyanide reacts with copper and lead to form extremely stable copper-cyanide complexes [Cu(CN)4]. 3- and lead-cyanide complex [Pb(CN)4] 3- At this point, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be formed, and copper and lead do not participate in the reaction. On the other hand, to create a stable electrolytic environment for the next step of copper content determination-electrolysis, the complexation reaction can avoid the hydrolysis of copper ions, avoid the decrease in conductivity caused by precipitation due to hydrolysis, and at the same time inhibit anodic passivation. Potassium cyanide forms a stable complex with copper ions at the anode (such as Cu(CN)3). 2-This reduces oxide buildup on the anode surface, prevents passivation film formation, and maintains efficient anode electrolysis. During copper electrolysis, tartaric acid is introduced into the electrolyte solution system. Tartaric acid contains two carboxyl groups and two hydroxyl groups, which can react with metal ions (such as Fe). 3+ Zn 2+ This method forms stable complexes to mask iron and zinc, while also preventing the hydrolysis of copper. In the determination of zinc, iron is masked using potassium fluoride. This application combines extraction-reduction, electrochemical precipitation, redox, and complexometric titration methods. By adding different masking agents, buffers, and precipitants in a single solution, it solves the problems of unsuitability of elemental methods, exceeding the measurement range, and the inability to continuously measure elements due to mutual interference.

[0141] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys, characterized by, It comprises the following steps: S1. Sample digestion The sample to be tested is digested to obtain a test solution; S2. Gold determination Ethyl acetate and methyl isobutyl ketone mixed solution is added to the test solution, and then extraction is carried out, followed by solid-liquid separation to obtain the water phase after extraction and the organic phase after extraction. Then, the organic phase after extraction is subjected to redox treatment and filtration to obtain gold-rich filter residue and filtrate one. The gold-rich filter residue is smelted to obtain gold, and finally the content of gold is calculated; S3. Silver determination The water phase after extraction is subjected to acid treatment, and then potassium cyanide is added. The silver is measured by titration using the Volhard method, and the content of silver is calculated; S4. Copper determination The solution after titration in step S3 is filtered, and then subjected to acid treatment. Subsequently, tartaric acid is added, and then electrolysis is carried out using the constant potential electrolysis method to obtain the electrolyte after electrolysis, and the content of copper is calculated; S5. Lead determination Concentrated sulfuric acid is added to the electrolyte after electrolysis in step S4, and heated to boiling. After cooling, filtration is carried out to obtain lead sulfate precipitate and filtrate two. Acetic acid-ammonium acetate is added to the lead sulfate precipitate, and heated until the lead sulfate precipitate is completely dissolved. The content of lead is calculated using the EDTA titration method; S6. Zinc determination Ammonium chloride, ammonium persulfate and ammonia water are added to the filtrate two in step S5, and heated to micro-boiling and immediately filtered to obtain a precipitate and filtrate three. Ammonium acetate-acetic acid and potassium fluoride are added to the filtrate three, and the content of zinc is calculated using the EDTA titration method.

2. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 1, characterized in that, Step S1 specifically comprises the following steps: 1.0-3.0g of sample is weighed, 20-50ml of ethanol solution is added, ultrasonic oscillation is carried out for 10-20min, 10-20ml of nitric acid is added, digestion is carried out until no bubbles are generated, 15-30ml of hydrochloric acid is added until the sample is completely dissolved, and then concentrated to 1-2ml, 3-5ml of 50% citric acid is added, and then 30-50ml of water is added for leaching.

3. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 1, characterized in that, Step S2 specifically comprises the following steps: 30-50ml of ethyl acetate and methyl isobutyl ketone mixed solution is added to the test solution, and extraction is carried out for 1-2min, and then solid-liquid separation is carried out to obtain organic phase 1 and water phase 1. Water phase 1 is subjected to the above extraction step again to obtain organic phase 2 and water phase 2. Water phase 2 is used as the water phase after extraction for subsequent operation. Organic phase 1 and organic phase 2 are combined to obtain the organic phase after extraction. 200-300ml of water is added to the organic phase after extraction, and then 1-2ml of hydrochloric acid is added and heated to boiling. 1-2g of thiourea is added while hot, heated at 100-120℃ for 10-15min, and then sodium sulfite is added gradually while hot until no more precipitate is generated. Filtration is carried out to obtain gold-rich filter residue and filtrate one. The gold-rich filter residue is smelted to obtain gold, and finally the content of gold is calculated.

4. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 3, characterized in that, The volume ratio of ethyl acetate and methyl isobutyl ketone is 1:

2.

5. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 3, characterized in that, The amount of sodium sulfite added at a time is not more than 0.10g.

6. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 1, characterized in that, Step S3 specifically comprises the following steps: The filtrate one is concentrated to 50ml, and then 10-20ml of nitric acid is added and heated for 5-10min. Then, 0.5g of potassium cyanide is added, and the silver is measured by titration using the Volhard method, and the content of silver is calculated.

7. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 1, characterized in that, The step S4 specifically comprises the following steps: filtering the solution titrated in the step S3, adding 5-20 ml of nitric acid to the filtrate, heating to micro-boiling, then adding 0.5 g of tartaric acid, and adding water to 300 ml, then electrolyzing by using the constant potential electrolysis method, after the electrolysis, taking out the cathode electrode, soaking the cathode electrode in the ethanol solution to remove copper, then taking out, drying and weighing, and calculating the copper content.

8. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 7, characterized in that, In the electrolysis, the current of the electrolysis is 5 A, the cathode point potential is 0.34 V, and the electrolysis time is 30-60 min.

9. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 1, characterized in that, The step S5 specifically comprises the following steps: concentrating the electrolyte in the step S4 to 70-80 ml, adding 10-20 ml of concentrated sulfuric acid, heating to boiling, cooling, and filtering to obtain lead sulfate precipitate and filtrate II, adding 30-100 ml of acetic acid-ammonium acetate to the lead sulfate precipitate, heating to completely dissolve the lead sulfate precipitate, and calculating the lead content by using the EDTA titration method.

10. The method for continuous determination of gold, silver, copper, lead, zinc in gold-based alloys according to claim 1, characterized in that, The step S6 specifically comprises the following steps: concentrating the filtrate II in the step S5 to 50-80 ml, adding 3-5 g of ammonium chloride, 0.5-1 g of ammonium persulfate and 20-40 ml of ammonia water, heating to micro-boiling and immediately filtering to obtain a precipitate and filtrate III, concentrating the filtrate III to 100 ml, adding 10-30 ml of ammonium acetate-acetic acid and 5 ml of potassium fluoride with a concentration of 50-100 g / L, and calculating the zinc content by using the EDTA titration method.

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