Method for continuously measuring gold, silver, copper, lead and zinc in gold-based alloy

Abstract

The invention provides a method for continuously measuring gold, silver, copper, lead and zinc in gold-based alloy, and belongs to the technical field of gold alloy element content detection. According to the method, through combined use of a gravimetric method, an electrolytic method and a titration method, by taking chemical means such as extraction and back extraction, electrochemistry and complex reaction as a theoretical basis, the aim of continuously and accurately measuring gold, silver, copper, lead and zinc in the gold-based alloy can be achieved through one-time sample weighing and sample digestion, the efficiency is improved, the complexity of multiple times of treatment is reduced, and the method is suitable for large-scale popularization and application. The method is accurate and reliable. Different masking agents, buffer reagents, precipitants and the like are selected in a targeted manner to be used in one solution one by one, and the problems that an element method is not applicable, measurement is out of range, and elements interfere with one another are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gold alloy element content detection, and particularly relates to a method for continuously determining gold, silver, copper, lead and zinc in a gold-based alloy. BACKGROUND

[0002] The detection of gold, silver, copper, lead and zinc in a gold-based alloy mainly includes instrument methods such as inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), and some wet chemical analysis methods. From the detection method, none of these methods is a determination method for the specific five-element alloy of gold-based alloy. There are disadvantages such as mutual interference between the gold, silver, copper, lead and zinc matrix, inability to continuously determine, the need for multiple sampling and detection of multiple methods one by one, large sample consumption, long operation process, poor method repeatability and reproducibility, and the like.

[0003] Continuous determination refers to the determination of each element to be measured by different chemical treatment means for one digested sample. The above methods can only determine a unique measured value for a certain element, and cannot continuously determine gold, silver, copper, lead and zinc. Only single-element determination of a single method can be achieved by instrument method, gravimetric method or volumetric method. To measure all five elements of gold, silver, copper, lead and zinc, more than four or five methods are often required, and repeated sampling and multiple sample digestion are required. The operation process is long and complex. The patents with publication numbers CN114878565A and CN114739983A disclose methods for continuously determining copper, lead and zinc. The copper, lead and zinc elements to be measured are in the form of ions in the solution by sample digestion or precipitation, and then are taken separately. One sample is taken for one element. Although the determination of copper, lead and zinc is achieved, there is no correlation between each method, and it is not a continuous determination of one sample. Essentially, it is equivalent to the stacking of multiple independent methods. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a method for continuously determining gold, silver, copper, lead and zinc in a gold-based alloy, aiming to solve the problems of no suitable determination method for gold, silver, copper, lead and zinc in the existing gold-based alloy and large difference in determination results.

[0005] The embodiment of the present application provides a method for continuously determining gold, silver, copper, lead and zinc in a gold-based alloy, including the following steps: S1. Sample digestion The sample to be tested is digested to obtain a solution to be tested; S2. Determination of gold Ethyl acetate and methyl isobutyl ketone mixed solution is added to the solution to be tested, extraction is performed, and then solid-liquid separation is performed to obtain an extracted aqueous phase and an extracted organic phase. The extracted organic phase is then subjected to redox treatment and filtration to obtain a gold-rich filter residue and a filtrate 1. The gold-rich filter residue is subjected to smelting to obtain gold, and finally the content of gold is calculated. S3. Determination of silver The extracted aqueous phase is subjected to acid treatment, and then potassium cyanide is added. The silver content is calculated by using the Volhard method for titration measurement. S4. Determination of copper The solution after titration in step S3 is filtered, and then subjected to acid treatment. Tartaric acid is then added, and then constant potential electrolysis is performed to obtain an electrolyte after electrolysis, and the copper content is calculated. S5. Determination of lead Concentrated sulfuric acid is added to the electrolyte after electrolysis in step S4, heated to boiling, and then filtered after cooling to obtain lead sulfate precipitate and filtrate 2. Acetic acid-ammonium acetate is added to the lead sulfate precipitate, heated to completely dissolve the lead sulfate precipitate, and the content of lead is calculated by using the EDTA titration method. S6. Determination of zinc Ammonium chloride, ammonium persulfate and ammonia water are added to the filtrate 2 in step S5, heated to micro-boiling and immediately filtered to obtain a precipitate and filtrate 3. Ammonium acetate-acetic acid and potassium fluoride are added to the filtrate 3, and the content of zinc is calculated by using the EDTA titration method.

[0006] In the technical scheme of the embodiments of the present application, by using the combination of gravimetric method, electrolysis method and titration method, and based on the chemical means such as extraction and back extraction, electrochemistry and complex reaction, the purpose of continuous and accurate determination of gold, silver, copper, lead and zinc in gold-based alloy can be achieved by one sample weighing and sample digestion, the efficiency is improved, the complexity of multiple treatments is reduced, and the method is accurate and reliable. The combination of extraction-reduction method, electrochemical precipitation method, oxidation-reduction method and complex titration method solves the problems of unsuitable element method, out-of-range measurement and mutual interference between elements by adding different masking agents, buffer reagents and precipitating agents in one solution.

[0007] In some embodiments, step S1 specifically includes the following steps: 1.0-3.0g of sample is weighed, 20-50ml of ethanol solution is added, ultrasonic oscillation is performed for 10-20min, 10-20ml of nitric acid is added, digestion is performed 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.

[0008] In this embodiment, by adding citric acid in the digestion, citric acid acts as a complex stabilizer, the carboxyl group of citric acid forms a coordination bond with copper, lead and zinc, forming a citric acid copper / lead / zinc complex with hydrophilicity, which is then retained in the aqueous phase, without affecting the organic extraction of gold in the first step, and also ensuring that the subsequent elements to be measured are not lost.

[0009] In some embodiments, step S2 specifically comprises the following steps: 30-50 ml of a mixed solution of ethyl acetate and methyl isobutyl ketone is added to the solution to be measured, and extraction is performed for 1-2 min, followed by solid-liquid separation to obtain organic phase 1 and aqueous phase 1. The aqueous phase 1 is subjected to the above extraction steps again to obtain organic phase 2 and aqueous phase 2. The aqueous phase 2 is used as the post-extraction aqueous phase for subsequent operations. The organic phase 1 and the organic phase 2 are combined to obtain a post-extraction organic phase. 200-300 ml of water is added to the post-extraction organic phase, followed by the addition of 1-2 ml of hydrochloric acid and heating to boiling. 1-2 g of thiourea is added while hot, and heating is performed at 100-120°C for 10-15 min. Sodium sulfite is added gradually while hot until no more precipitate is produced. Filtration is performed to obtain gold-rich filter residue and filtrate 1. The gold-rich filter residue is subjected to smelting to obtain gold. Finally, the content of gold is calculated.

[0010] In this embodiment, a mixed organic extraction system of ethyl acetate and methyl isobutyl ketone is constructed to extract gold. When the volume ratio of ethyl acetate to methyl isobutyl ketone is 1:2, the recovery rate of gold extraction 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 speed becomes faster and faster. Due to the involvement of multiple digestions and repeated extractions in the operation process, combined with the influence of the temperature of the digestion solution, too fast volatilization will lead to differences in the amount of extractant, a decrease in the extraction rate, poor precision of the results, and low recovery rate.

[0011] In some embodiments, the amount of sodium sulfite added each time is not greater than 0.10 g.

[0012] In this embodiment, sodium sulfite is added gradually in small amounts. The sulfite ion (SO3 2- ) reduces the oxidizing trivalent gold ion (Au 3+ ) to elemental gold, achieving the purpose of determining gold by gravimetric method.

[0013] In some embodiments, step S3 specifically comprises the following steps: the filtrate 1 is concentrated to 50 ml, 10-20 ml of nitric acid is then added, and heating is performed for 5-10 min. Next, 0.5 g of potassium cyanide is added, and the Fehling method is used to measure the titration of silver, and the content of silver is calculated.

[0014] In this embodiment, the Volhard method is adopted, potassium thiocyanate is used as titrant, and iron ammonium vanadate is used as indicator. Since Ag + has a stronger combination ability with SCN - than Fe 3+ , after the AgSCN precipitation reaction is completed, the excess Fe 3+ reacts with SCN - to generate Fe(SCN)6 3- (red), which indicates the end point. During the titration process, a small amount of copper and lead participates in the reaction. Potassium cyanide is added to mask the copper and lead. The excess potassium cyanide reacts with copper and lead to generate extremely stable copper cyanide complex [Cu(CN)4] 3- and lead cyanide complex [Pb(CN)4] 3- . At this time, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be generated, and copper and lead do not participate in the reaction. On the other hand, in order to create a stable electrolysis environment for the next copper measurement-electrolysis method, the complex reaction can avoid the hydrolysis of copper ions, avoid the decrease in conductivity caused by the precipitation due to hydrolysis, inhibit the anode passivation, form a stable complex (such as Cu(CN)3 2- ) with the anode copper ions, reduce the accumulation of the anode oxide layer, prevent the formation of the passivation film, and maintain the high-efficiency electrolysis of the anode.

[0015] In some embodiments, step S4 specifically includes the following steps: filtering the solution after titration in 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 a volume of 300 ml, and then performing electrolysis by using the constant potential electrolysis method. After the electrolysis is completed, the cathode electrode is taken out, the cathode electrode is soaked in an ethanol solution to remove copper, and then the cathode electrode is taken out, dried, and weighed to calculate the copper content. In the electrolysis, the current of the electrolysis is 5 A, and the cathode point potential is 0.34 V. The electrolysis time is 30-60 min.

[0016] In this embodiment, the 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 and deposited on the cathode. A small amount of iron and zinc is also electrolyzed and mixed in the cathode copper, which affects the results. Tartaric acid is introduced into the electrolysis solution system. Tartaric acid is a binary organic acid containing two carboxyl groups and two hydroxyl groups, which can form stable complexes with metal ions (such as Fe 3+ , Zn 2+ ) to mask iron and zinc, and also prevent the hydrolysis of copper.

[0017] In some embodiments, step S5 specifically comprises 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 two, 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 EDTA titration.

[0018] In this embodiment, the determination of lead is based on complexation reaction, and EDTA titration is used. The reaction is as follows: color reaction: Pb2 + + dimethylphenol orange → purple red complex, complex titration reaction: Pb 2+ + EDTA4- → Pb-EDTA 2- .

[0019] In some embodiments, step S6 specifically comprises the following steps: concentrating the filtrate two in 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 three, concentrating the filtrate three 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 EDTA titration.

[0020] In this embodiment, the determination of zinc is based on complexation reaction, and EDTA titration is used. In the titration process, iron is masked by potassium fluoride; masking reaction: Fe 3+ + 6F - → FeF6 3- .

[0021] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. DETAILED DESCRIPTION

[0022] The embodiments of the technical solutions of the present application will be described in detail below. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0023] 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 the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application are intended to cover non-exclusive inclusion.

[0024] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0025] In order to solve the problem that there is no suitable determination method for gold, silver, copper, lead and zinc in the existing gold-based alloy, and the determination results are greatly different, the application provides a method for continuous determination of gold, silver, copper, lead and zinc in a gold-based alloy. Through the joint use of gravimetric method, electrolytic method and titration method, and based on chemical means such as extraction and back extraction, electrochemistry and complex reaction, the purpose of continuous and accurate determination of gold, silver, copper, lead and zinc in the gold-based alloy can be achieved through one-time sample weighing and sample digestion, the efficiency is improved, the complexity of multiple treatments is reduced, and the method is accurate and reliable. In the digestion, citric acid is added, the carboxyl group of citric acid forms a coordination bond with copper, lead and zinc to form a citric acid copper / lead / zinc complex with hydrophilicity, and then remains in the aqueous phase, without affecting the organic extraction of gold in the first step, and also ensuring that the measured elements in the following step are not lost; an ethyl acetate and methyl isobutyl ketone mixed organic extraction system is constructed to extract gold, when the volume ratio of ethyl acetate to methyl isobutyl ketone is 1:2, the recovery rate of gold extraction reaches more than 99.9% under the acidity of 1 mol / L; in the silver measurement, potassium cyanide is added for masking, and the excess potassium cyanide reacts with copper and lead to form extremely stable copper cyanide complex [Cu(CN)4] 3- and lead cyanide complex [Pb(CN)4] 3- At this time, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be generated, and copper and lead do not participate in the reaction. On the other hand, in order to create a stable electrolysis environment for the next copper measurement-electrolysis, the complex reaction can avoid the hydrolysis of copper ions, avoid the decrease of conductivity caused by the precipitation generated by hydrolysis, inhibit the anode passivation, form a stable complex (such as Cu(CN)3 2- ) with the anode copper ions, reduce the accumulation of the anode surface oxide layer, prevent the formation of the passivation film, and maintain the high-efficiency electrolysis of the anode; in the copper electrolysis process, tartaric acid is introduced into the electrolysis solution system, tartaric acid contains two carboxyl groups and two hydroxyl groups, and can react with metal ions (such as Fe 3+ , Zn 2+) form stable complex, to mask iron and zinc, while also able to prevent copper hydrolysis; in the determination of zinc, iron is masked with potassium fluoride. The present application combines extraction-reduction method, electrochemical precipitation method, redox method, complexometric titration method, by adding different masking agent, buffer reagent, precipitant, etc. in a solution one by one, solves the problem of element method not applicable, determination out of range, mutual interference between elements cannot be continuously determined.

[0026] The embodiment of the present application provides a kind of gold, silver, copper, lead, zinc continuous determination method in gold-based alloy, comprising the following steps: S1. sample digestion The sample to be measured is digested to obtain a test solution; S2. determination of gold Ethyl acetate and methyl isobutyl ketone mixed solution are added to the test solution, extracted, then solid-liquid separation is carried out, to obtain the water phase after extraction and the organic phase after extraction, then the organic phase after extraction is subjected to redox treatment, filtration is carried out, to obtain gold-rich filter residue and filtrate one, the gold-rich filter residue is subjected to smelting, to obtain gold, and finally the content of gold is calculated; S3. determination of silver The water phase after extraction is subjected to acid treatment, then potassium cyanide is added, and the titration measurement of silver is carried out by using the Volhard method, to calculate the content of silver; S4. determination of copper The solution after titration in step S3 is filtered, then subjected to acid treatment, then tartaric acid is added, then the constant potential electrolysis method is used for electrolysis, to obtain the electrolyte after electrolysis, and the content of copper is calculated; S5. determination of lead Concentrated sulfuric acid is added to the electrolyte after electrolysis in step S4, heated to boiling, cooled and filtered, to obtain lead sulfate precipitate and filtrate two, acetic acid-ammonium acetate is added to the lead sulfate precipitate, heated to completely dissolve the lead sulfate precipitate, and the content of lead is calculated by using the EDTA titration method; S6. determination of zinc Ammonium chloride, ammonium persulfate and ammonia are added to the filtrate two in step S5, 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 by using the EDTA titration method.

[0027] The technical scheme of the embodiment of the application is characterized in that, by using the combination of the gravimetric method, the electrolytic method and the titration method, and taking the chemical methods such as extraction and back extraction, electrochemistry and complex reaction as the theoretical basis, the continuous and accurate determination of gold, silver, copper, lead and zinc in the gold-based alloy can be realized by one-time sample weighing and sample digestion, the efficiency is improved, the complexity of multiple treatments is reduced, and the method is accurate and reliable. The combined extraction-reduction method, the electrochemical precipitation method, the oxidation-reduction method and the complex titration method are used in one solution by adding different masking agents, buffer reagents and precipitating agents, thereby solving the problems of unsuitable element method, out-of-range determination and mutual interference between elements.

[0028] Further, in some embodiments, step S1 specifically comprises the following steps: weighing 1.0-3.0 g of the sample, adding 20-50 ml of an ethanol solution, ultrasonic oscillation for 10-20 min, then adding 10-20 ml of nitric acid, digesting until no bubbles are generated, then adding 15-30 ml of hydrochloric acid until the sample is completely dissolved, and concentrating to 1-2 ml, adding 3-5 ml of citric acid with a concentration of 50%, and then adding 30-50 ml of water for leaching.

[0029] In the technical scheme of the embodiment of the application, citric acid is added in the digestion, the carboxyl group of the citric acid forms a coordination bond with copper, lead and zinc, and a citric acid copper / lead / zinc complex with hydrophilicity is formed, thereby ensuring that the to-be-detected elements are not lost without affecting the organic extraction of gold in the first step.

[0030] Further, in some embodiments, step S2 specifically comprises the following steps: adding 30-50 ml of a mixed solution of ethyl acetate and methyl isobutyl ketone to the to-be-detected solution, extracting for 1-2 min, then performing solid-liquid separation to obtain organic phase 1 and water phase 1, repeating the above extraction steps on the water phase 1 again to obtain organic phase 2 and water phase 2, taking the water phase 2 as the post-extraction water phase for subsequent operation, combining the organic phase 1 and the organic phase 2 to obtain a post-extraction organic phase, adding 200-300 ml of water to the post-extraction organic phase, then adding 1-2 ml of hydrochloric acid and heating to boiling, adding 1-2 g of thiourea while hot, heating at 100-120 ℃ for 10-15 min, and then adding sodium sulfite while hot in sequence until no more precipitate is generated, filtering to obtain gold-rich filter residue and filtrate one, smelting the gold-rich filter residue to obtain gold, and finally calculating the content of gold.

[0031] In the technical scheme of the embodiment of the present application, the ethyl acetate and methyl isobutyl ketone mixed organic extraction system is constructed to extract gold, when the volume ratio of ethyl acetate to methyl isobutyl ketone is 1:2, the recovery rate of gold extraction reaches more than 99.9% under the 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 speed is faster and faster. Due to the involvement of multiple digestion and repeated extraction in the operation process, combined with the influence of the temperature of the digestion solution, too fast volatilization will lead to different amounts of extractant and decreased extraction rate, resulting in poor precision and low recovery rate of the results.

[0032] Further, in some embodiments, the smelting of the gold-rich filter residue specifically comprises the following steps: adding a small amount of borax and sodium carbonate protective agent in a porcelain crucible, and smelting at 1100°C for 10-15 min.

[0033] Further, in some embodiments, the amount of sodium sulfite added each time is not more than 0.10 g.

[0034] In the technical scheme of the embodiment of the present application, sodium sulfite is added in small amounts successively, and the sulfite ion (SO3 2- ) is used to reduce the oxidizing trivalent gold ion (Au 3+ ) into elemental gold, so as to realize the purpose of gravimetric determination of gold.

[0035] Further, in some embodiments, step S3 specifically comprises the following steps: the filtrate is concentrated to 50 ml, then 10-20 ml of nitric acid is added, heated for 5-10 min, then 0.5 g of potassium cyanide is added, and the silver is titrated and measured by the Volhard method, and the silver content is calculated.

[0036] Further, in some embodiments, the Volhard method specifically comprises the following steps: 1-2 mL of ferric ammonium sulfate indicator is added, and titration is performed with a potassium thiocyanate standard solution until the solution turns light red, which is the end point of titration.

[0037] In the technical scheme of the embodiment of the present application, the Volhard method is used, potassium thiocyanate is used as the titrant, and ferric ammonium vanadium is used as the indicator. The combination ability of Ag + and SCN - is much stronger than that of Fe 3+ . After the AgSCN precipitation reaction is complete, the excess Fe 3+ reacts with SCN - to generate Fe(SCN)6 3- (red) to indicate the end point. During the titration process, a small amount of copper and lead are involved in the reaction, and potassium cyanide is added for masking. The excess potassium cyanide reacts with copper and lead to generate an extremely stable copper cyanide complex [Cu(CN)4] 3-and lead cyanide complex [Pb(CN)4] 3- At this time, the ionic product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be generated, and copper and lead do not participate in the reaction. On the other hand, in order to create a stable electrolysis environment for the next step of copper measurement-electrolysis method, the complex reaction can avoid the hydrolysis of copper ions, avoid the decrease of conductivity caused by the precipitation due to hydrolysis, and inhibit the anode passivation at the same time. Potassium cyanide forms a stable complex (such as Cu(CN)3 2- ) with the anode copper ions, reduces the accumulation of the anode surface oxide layer, prevents the formation of the passivation film, and maintains the high efficiency of the anode electrolysis.

[0038] Further, in some embodiments, step S4 specifically includes the following steps: filtering the solution after titration in 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 a volume of 300 ml, then performing electrolysis by constant potential electrolysis method. After electrolysis, the cathode electrode is taken out, immersed in an ethanol solution to remove copper, then taken out and dried and weighed to calculate the copper content. In the electrolysis, the current of electrolysis is 5 A, and the cathode point potential is 0.34 V. The electrolysis time is 30-60 min.

[0039] Further, in some embodiments, the constant potential electrolysis method specifically includes the following steps: placing the weighed mesh platinum cathode, platinum anode, and Ganzin electrode into the solution and connecting them to the copper electrolysis equipment, starting the uniform stirring mode, controlling the cathode potential at 0.34 V, and performing electrolysis with a current of 5 A. When the electrolysis current decreases to below 200 mA and continues to electrolyze for 20 min without adding new copper on the electrode surface, the cathode is removed from the solution without interrupting the current.

[0040] In the technical scheme of the embodiments of the present application, the constant potential electrolysis method is used to improve the accuracy and sensitivity of copper electrolysis. In the electrolysis process, copper ions are reduced to elemental copper on the cathode, and a small amount of iron and zinc are electrolyzed together with the cathode copper, which affects the results. Tartaric acid is introduced into the electrolysis solution system. Tartaric acid is a binary organic acid containing two carboxyl groups and two hydroxyl groups, which can form stable complexes with metal ions (such as Fe 3+ , Zn 2+ ) to mask iron and zinc, and also prevent the hydrolysis of copper.

[0041] Further, in some embodiments, step S5 specifically comprises 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 two, 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 EDTA titration.

[0042] Further, in some embodiments, the EDTA titration method for calculating the lead content specifically comprises the following steps: adding 3-6 drops of dimethyl phenol orange as an indicator, and titrating with a Na2EDTA standard titration solution until a bright yellow color is obtained.

[0043] In the technical solution of the embodiments of the present application, the determination of lead is based on complexation reaction, and EDTA titration is used. The reaction is as follows: color reaction: Pb2 + + dimethyl phenol orange → purple red complex, complex titration reaction: Pb 2+ + EDTA4- → Pb-EDTA 2- .

[0044] Further, in some embodiments, step S6 specifically comprises the following steps: concentrating the filtrate two in 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 three, concentrating the filtrate three 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 EDTA titration.

[0045] Further, in some embodiments, the EDTA titration method for calculating the zinc content specifically comprises the following steps: adding 3-6 drops of dimethyl phenol orange as an indicator, and titrating with a Na2EDTA standard titration solution until a bright yellow color is obtained.

[0046] In the technical solution of the embodiments of the present application, the determination of zinc is based on complexation reaction, and EDTA titration is used. In the titration process, iron is masked by potassium fluoride; masking reaction: Fe 3+ + 6F - → FeF6 3- .

[0047] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and cannot be understood as a limitation of the present application. If a specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product manual is used. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0048] Example 1 The embodiment provides a method for continuously determining gold, silver, copper, lead and zinc in a gold-based alloy, and specifically comprises the following steps: Take 3.0 g of the sample into a beaker, add 30 ml of an ethanol solution, ultrasonically shake for 20 min, add 20 ml of nitric acid, digest until no bubbles are generated, add 30 ml of hydrochloric acid, continue to digest until completely dissolved, and concentrate to 2 ml, add 5 ml of citric acid with a concentration of 50%, and then add 50 ml of water for leaching to obtain a to-be-tested solution.

[0049] Transfer the to-be-tested solution into a separatory funnel, add 50 ml of ethyl acetate and methyl isobutyl ketone (volume ratio 1:1), fully extract for 2 min, and then let the layers stand, transfer the water phase into another separatory funnel, add 50 ml of ethyl acetate and methyl isobutyl ketone (volume ratio 1:2) again, extract for 2 min again, let the layers stand, combine the organic phases extracted twice, and then add into a beaker, add 200 ml of water, add 2 ml of hydrochloric acid, heat to micro-boiling, while hot, add 3 g of thiourea, heat at 100 ℃ for 15 min, while hot, add 0.1 g of sodium sulfite gradually, after the gold is completely reduced to a precipitate, let stand for 10 min, and then filter to obtain a gold-rich filter residue and a filtrate I, and the gold-rich filter residue is placed in a porcelain crucible together with filter paper, a small amount of borax and sodium carbonate protective agent is added into the porcelain crucible, and then smelting is performed at 1100 ℃ for 15 min, after cooling, the mass of gold is calculated; Gold content calculation: W Au = m Au / m*100% In the formula: W Au —mass fraction of gold, in percentage (%); m Au —mass of gold after roasting, in grams (g); m—mass of the sample, in grams (g).

[0050] Heat and concentrate the water phase extracted the second time to 50 ml, add 20 ml of nitric acid, heat for 10 min, add 0.5 g of potassium cyanide, cool to room temperature, and perform the reaction in a fume hood throughout the process, then add 2 mL of ferric ammonium sulfate indicator, titrate with a potassium thiocyanate standard solution, and titrate to a light red sample to be tested as the titration end point, and calculate the silver content; Silver content calculation: W Ag =((C Ag *(V1-V0)*M Ag ) / (m*1000))*100% In the formula: W Ag— mass fraction of silver, expressed in percentage (%); C Ag — actual concentration of potassium thiocyanate standard titration solution, in moles per liter (mol / L); V1— volume of potassium thiocyanate standard titration solution actually consumed, in milliliters (mL); V0— volume of potassium thiocyanate standard titration solution consumed by the blank solution, in milliliters (mL); M Ag — molar mass of silver, in grams per mole (g / mol); m— sample mass, in grams (g).

[0051] The above titrated solution is filtered, 20 ml of nitric acid is added, heated to micro-boiling, 0.5 g of tartaric acid is added, removed and cooled to room temperature, water is added to a volume of 300 ml, the weighed mesh platinum cathode, platinum anode, and Gunning electrode are placed in the solution and connected to the copper electrolysis equipment, the uniform stirring mode is started, the cathode potential is controlled at 0.34 V, electrolysis is carried out with a current of 5 A, and when the electrolysis current drops to below 200 mA, and continues to electrolyze for 20 min without adding new copper on the electrode surface, the cathode is removed from the solution, slowly immersed in an ethanol solution, taken out and dried, and weighed to calculate the copper content; Copper content calculation: W Cu = m Cu / m*100% In the formula: W Cu — mass fraction of copper, in percentage (%); m Cu — mass of copper after reduction, in grams (g); m— sample mass, in (g).

[0052] The above electrolyte is concentrated to 80 ml, 20 ml of concentrated sulfuric acid is added, heated to boiling, cooled and filtered to obtain lead sulfate precipitate and filtrate, 80 ml of acetic acid-ammonium acetate is added to the lead sulfate precipitate, heated to completely dissolve the lead sulfate precipitate, 3-6 drops of dimethyl phenol orange are added, titrated with Na2EDTA standard titration solution to bright yellow, and the lead content is calculated; Lead content calculation: W Pb = ( (C Pb * (V2-V3) *M Pb ) / (m*1000) ) *100% In the formula: W Pb — mass fraction of lead, expressed in percentage (%); C Pb actual concentration of EDTA standard titration solution, unit: mol / L; V2 - actual volume of EDTA standard titration solution consumed, unit: mL; V3 - volume of EDTA standard titration solution consumed by blank solution, unit: mL; M Pb molar mass of lead, unit: g / mol; m - sample mass, unit: g.

[0053] The filtrate was concentrated to 580 ml, 5 g of ammonium chloride, 1 g of ammonium persulfate and 40 ml of ammonia water were added, heated to micro-boiling and immediately filtered to obtain a precipitate and filtrate three, the filtrate three was concentrated to 100 ml, 30 ml of ammonium acetate-acetic acid and 5 ml of potassium fluoride with a concentration of 80 g / L were added, titrated with Na2EDTA standard titration solution to bright yellow, and the content of zinc was calculated; Zinc content calculation: W Zn = ( (C Zn * (V4-V5) *M Zn ) / (m*1000) ) *100% In the formula: W Zn mass fraction of zinc, expressed in percentage (%); C Zn actual concentration of EDTA standard titration solution, unit: mol / L; V4 - actual volume of EDTA standard titration solution consumed, unit: mL; V5 - volume of EDTA standard titration solution consumed by blank solution, unit: mL; M Zn molar mass of zinc, unit: g / mol; m - sample mass, unit: g.

[0054] Among them, the source and performance parameters of the raw materials are as follows: Select laboratory quality control sample HJ-1 as test sample, and the value is shown in Table 1.

[0055] Table 1 HJ-1 value table Comparative examples 1-5 Comparative Examples 1-5 each provide a method for continuous determination of gold, silver, copper, lead and zinc in a gold-based alloy, and differ from Example 1 in that the volume ratio of ethyl acetate to methyl isobutyl ketone is different in the determination of gold, as shown in Table 2 below, and other steps are substantially the same as in Example 1 and will not be repeated here.

[0056] Table 2 Volume ratio of ethyl acetate to methyl isobutyl ketone and gold recovery rate in Example 1 and Comparative Examples 1-5 Table 2 results show that as the proportion of methyl isobutyl ketone gradually increases, the extraction recovery rate of gold gradually increases, and when the proportion reaches 1:1, there is no obvious yellow color in the extraction solution, and the extraction rate of gold is significantly improved. When the proportion is 1:2, the extraction effect is best and the extraction rate is highest, and the extraction recovery rate of gold reaches 99.95%. However, as the proportion of methyl isobutyl ketone continues to increase, the volatilization speed becomes faster and faster. Due to the multiple digestion and repeated extraction involved in the operation process, combined with the influence of digestion solution temperature, too fast volatilization will result in different amounts of extractant and decreased extraction rate, leading to poor precision of results and low recovery rate.

[0057] Comparative Example 6 This comparative example provides a method for continuous determination of gold, silver, copper, lead and zinc in a gold-based alloy, and differs from Example 1 in that no potassium cyanide is added in the determination of silver, and other steps are substantially the same as in Example 1 and will not be repeated here.

[0058] Table 3 Determination results of gold, silver, copper, lead and zinc in Example 1 and Comparative Example 6 Table 3 results show that without the addition of potassium cyanide, the silver result is high, and the copper, lead and zinc results are low. The determination results of gold, silver, copper, lead and zinc in Example 1 are basically consistent with the specified values. The addition of potassium cyanide plays two roles. First, it ensures the accuracy of the silver result. Excessive potassium cyanide reacts with copper and lead to form extremely stable copper cyanide complexes [Cu(CN)4] 3- and lead cyanide complexes [Pb(CN)4] 3- At this time, 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, which ensures the accuracy of the silver, copper and lead results. Second, it creates a stable electrolytic environment for the next copper determination-electrolysis method. The complexation reaction can avoid the hydrolysis of copper ions, avoid the decrease in conductivity caused by the precipitation due to hydrolysis, inhibit the anode passivation, form stable complexes (such as Cu(CN)3 2- ) with anode copper ions, reduce the accumulation of oxide layer on the anode surface, prevent the formation of passivation film, maintain efficient electrolysis of the anode, and ensure the accuracy of the copper result.

[0059] To further verify the accuracy of the present scheme, two national standard materials GBW(E)020240 and GBW(E)020241 were used as test samples, and the standard mass values and uncertainties thereof are shown in Table 4.

[0060] Table 4 Standard mass values and uncertainties The test was performed according to the method of Example 1, and the test results are shown in Table 5.

[0061] Table 5 Test results As can be seen from Table 5, the test results of the present scheme are basically consistent with the composition of the standard sample.

[0062] In summary, the present application provides a method for continuously determining gold, silver, copper, lead and zinc in a gold-based alloy. By the joint use of gravimetric method, electrolytic method and titration method, and based on the chemical means of extraction and back extraction, electrochemistry and complexation reaction, the purpose of continuously and accurately determining gold, silver, copper, lead and zinc in a gold-based alloy can be achieved through one-time sample weighing and sample digestion, thereby improving the efficiency and reducing the complexity of multiple treatments. The method is accurate and reliable. In the digestion, citric acid is added as a complexing stabilizer. The carboxyl group of citric acid forms a coordination bond with copper, lead and zinc to form a citric acid copper / lead / zinc complex with hydrophilicity, which is then left in the aqueous phase, without affecting the organic extraction of gold in the first step, and ensuring that the measured elements in the following step are not lost. An ethyl acetate and methyl isobutyl ketone mixed organic extraction system is constructed to extract gold. When the volume ratio of ethyl acetate to methyl isobutyl ketone is 1:2, the recovery rate of gold extraction reaches more than 99.9% under the acidity of 1 mol / L. In the silver measurement, potassium cyanide is added for masking. The excess potassium cyanide reacts with copper and lead to form extremely stable copper cyanide complex [Cu(CN)4] 3- and lead cyanide complex [Pb(CN)4] 3- At this time, the ion product Q of silver thiocyanate in the solution is greater than the solubility product constant Ksp, so silver thiocyanate precipitate can be generated, and copper and lead do not participate in the reaction. On the other hand, in order to create a stable electrolysis environment for the next copper measurement-electrolysis, the complexation reaction can avoid the hydrolysis of copper ions, avoid the decrease of conductivity caused by the precipitation due to hydrolysis, inhibit the anode passivation, form a stable complex (such as Cu(CN)3 2- ) with the anode copper ions, reduce the accumulation of the anode surface oxidation layer, prevent the formation of passivation film, and maintain the high efficiency of the anode electrolysis; in the copper electrolysis process, tartaric acid is introduced into the electrolysis solution system. Tartaric acid contains two carboxyl groups and two hydroxyl groups, which can react with metal ions (such as Fe 3+ , Zn 2+) form stable complex, to mask iron and zinc, while also able to prevent copper hydrolysis; in the determination of zinc, iron is masked by potassium fluoride. The present application combines extraction-reduction method, electrochemical precipitation method, redox method, complexometric titration method, by adding different masking agent, buffer reagent, precipitant, etc. in a solution one by one, solves the problem of element method not applicable, determination out of range, mutual interference between elements cannot be continuously determined.

[0063] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for continuous determination of gold, silver, copper, lead, and zinc in a gold-based alloy, characterized in that, Includes the following steps: S1. Sample digestion The sample to be tested is digested to obtain the test solution; S2. Determination of Gold 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. S3. Determination of Silver 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. S4. Determination of Copper 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. S5. Determination of Lead 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. S6. Determination of Zinc 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.

2. The method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys according to claim 1, characterized in that, 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.

3. The method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys according to claim 1, characterized in that, Step S2 specifically includes the following steps: Add 30-50 ml of a mixed solution of ethyl acetate and methyl isobutyl ketone to the test solution, extract for 1-2 min, then separate the solid and liquid phases to obtain organic phase 1 and aqueous phase 1. Repeat the above extraction steps for 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. Combine organic phase 1 and organic phase 2 to obtain the extracted organic phase. Add 200-300 ml of water to the extracted organic phase, then add 1-2 ml of hydrochloric acid and heat to boiling. While hot, add 1-2 g of thiourea and heat at 100-120°C for 10-15 min. While hot, add sodium sulfite sequentially until no more precipitate is formed. Filter to obtain gold-rich filter residue and filtrate 1. Melt the gold-rich filter residue to obtain gold, and finally calculate the gold content.

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

2.

5. The method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys according to claim 3, characterized in that, The amount of sodium sulfite added each time shall not exceed 0.10g.

6. The method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys according to claim 1, characterized in that, Step S3 specifically includes the following steps: concentrate the filtrate to 50 ml, then add 10-20 ml of nitric acid, heat for 5-10 min, then add 0.5 g of potassium cyanide, and use the Volhart method to titrate the silver content and calculate the silver content.

7. The method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys according to claim 1, characterized in that, Step S4 specifically includes the following steps: filter the solution after titration in step S3, add 5-20 ml of nitric acid to the filtrate, heat to a gentle boil, then add 0.5 g of tartaric acid and add water to a volume of 300 ml. Then electrolyze using a constant potential electrolysis method. After electrolysis, remove the cathode electrode, immerse the cathode electrode in an ethanol solution to remove copper, then remove it, dry it, weigh it, and calculate the copper content.

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

9. The method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys according to claim 1, characterized in that, Step S5 specifically includes the following steps: Concentrate the electrolyte from step S4 to 70-80 ml, add 10-20 ml of concentrated sulfuric acid, heat to boiling, cool and filter to obtain lead sulfate precipitate and filtrate II, add 30-100 ml of acetic acid-ammonium acetate to the lead sulfate precipitate, heat until the lead sulfate precipitate is completely dissolved, and calculate the lead content using EDTA titration.

10. The method for continuous determination of gold, silver, copper, lead, and zinc in gold-based alloys according to claim 1, characterized in that, Step S6 specifically includes the following steps: Concentrate filtrate two from step S5 to 50-80 ml, add 3-5 g ammonium chloride, 0.5-1 g ammonium persulfate and 20-40 ml ammonia water, heat to a gentle boil and filter immediately to obtain precipitate and filtrate three, concentrate filtrate three to 100 ml, add 10-30 ml ammonium acetate-acetic acid and 5 ml potassium fluoride with a concentration of 50-100 g / L, and calculate the zinc content by EDTA titration.

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