Method for electrochemically dissolving a semiconductor substrate to recover precious metals

Abstract

The application discloses a method for recycling noble metal by electrochemically dissolving semiconductor lining plate, and belongs to the technical field of noble metal recycling. The technical scheme points of the method are as follows: lining plate cleaning; taking the lining plate as an anode, taking a titanium plate as a cathode, taking a mixed acid solution containing chloride ions as an anode electrochemical dissolving solution, taking a hydrochloric acid solution as a cathode electrochemical dissolving solution, arranging a cation exchange membrane between the cathode and the anode, taking the current density as 5-40 A / m 2 , and taking the dissolving temperature as 30-60 DEG C; repeatedly electrochemically dissolving gold to obtain gold powder, monitoring the reduction potential to be greater than or equal to 720 mV; oxidizing the remaining divalent platinum ions in the anode electrochemical dissolving solution into tetravalent platinum ions, adding ammonium chloride to react to generate ammonium chloroplatinate precipitate; filtering, washing and reducing the ammonium chloroplatinate to obtain platinum powder. By controlling the electrochemical dissolving temperature and the current density, oxidation and dissolving reaction of gold and platinum gold plating layers on the surface of the semiconductor lining plate is caused, the lining plate base material is not damaged and can be used for the second time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precious metal recovery, in particular to a method for recovering precious metal by electrochemical dissolution of semiconductor backing plate. BACKGROUND

[0002] As a support carrier of evaporation material, the semiconductor backing plate ensures the stability of the material in the high-temperature evaporation process, does not collapse or displace, and provides a flat and clean surface, reduces the pollution of the evaporation material, and ensures the uniformity and purity of the thin film deposited on the semiconductor substrate. After a period of use, the gold and platinum remaining on the surface of the backing plate need to be recovered. The existing backing plate gold and platinum recovery methods are as follows: one is to use a physical method to strip gold and platinum, that is, to use a high-pressure water gun to wash, manually scrape, sanding machine to polish, sand blasting and other methods to strip the gold and platinum plating layer. This method has the characteristics of high labor intensity and high loss of precious metals. Two is to use a chemical method, that is, to use aqua regia, cyanide or thiourea to dissolve the gold and platinum on the surface of the backing plate. The aqua regia method has the disadvantages of high corrosion and the generation of nitrogen oxides. The cyanide method is limited due to its toxicity. The thiourea method has the problems of easy decomposition of thiourea and low gold stripping efficiency. SUMMARY

[0003] In order to solve the problems in the prior art, the present application provides a method for recovering precious metal by electrochemical dissolution of semiconductor backing plate. The present application precisely controls the electrochemical dissolution temperature, current density and electrochemical dissolution system, so that the gold and platinum plating layer on the surface of the semiconductor backing plate undergoes an anodic oxidation dissolution reaction, the backing plate substrate is not damaged and can be used twice, the production cost is reduced, and resource recycling is realized.

[0004] The present application provides a method for recovering precious metal by electrochemical dissolution of semiconductor backing plate, which adopts the following technical scheme:

[0005] A method for recovering precious metal by electrochemical dissolution of semiconductor backing plate, the precious metal being gold and platinum, comprising the following steps:

[0006] S1, backing plate cleaning;

[0007] S2, electrochemical dissolution: the backing plate is used as an anode, a titanium plate after passivation treatment is used as a cathode, the anode electrochemical dissolution solution is an acid mixed solution containing chloride ions, the cathode electrochemical dissolution solution is a hydrochloric acid solution, a cation exchange membrane is arranged between the cathode and the anode, the current density is 5-40 A / m 2 , and the electrochemical dissolution temperature is 30-60℃;

[0008] S3, precious metal ion enrichment: repeating the above electrochemical dissolution, and enriching the precious metal ions in the anode electrochemical dissolution solution after multiple dissolutions to meet the reduction requirements;

[0009] S4, gold reduction: gold ions in the anode electrochemical dissolution solution after the enrichment of noble metal ions are reduced to obtain gold powder, the addition amount of the reducing agent is 1.2-1.5 times of the theoretical mass of gold, and the reduction potential of the anode electrochemical dissolution solution is monitored to be greater than or equal to 720 mV;

[0010] S5, platinum precipitation: divalent platinum ions in the remaining anode electrochemical dissolution solution obtained in step S4 are oxidized to tetravalent platinum ions, and then ammonium chloride is added to react to generate ammonium chloroplatinate precipitate;

[0011] S6, after the ammonium chloroplatinate is filtered and washed, platinum powder is obtained through reduction treatment.

[0012] By adopting the technical scheme, the gold and platinum gold plating layer on the surface of the semiconductor substrate is subjected to an anodic oxidation dissolution reaction by accurately controlling the electrochemical dissolution temperature, the current density and the anode electrochemical dissolution solution system components, and the current density and the electrochemical dissolution temperature are controlled, so that the noble metal is oxidized into metal ions, and at the same time, the base material is not corroded, so that the base material can be used again without damage, the production cost is reduced, and resource recycling is realized. The dissolved gold ions and platinum ions can rapidly form stable chloro complex ions (AuCl4 ﹣ and PtCl6 2﹣ ) with the chloride ions in the dissolution solution, thereby avoiding the situation that the noble metal ions pass through the cation exchange membrane and are deposited on the cathode plate. Therefore, compared with the traditional chemical dissolution method, the electrochemical dissolution has the advantages of high selectivity and strong controllability of the reaction, and the subsequent step-by-step reduction step, the reduction potential of the anode electrochemical dissolution solution and the addition amount of the reducing agent are controlled, so that the gold ions in the dissolution solution can be fully reduced to gold single element, and other metal ions are not reduced to single element at this reduction potential. Therefore, the purity of the gold powder obtained by the present application can reach 99.99%, and the recovery rate of the gold powder can reach more than 97%. Through the steps of platinum precipitation and reduction, the purity of platinum gold can reach more than 99.95%, and the recovery rate of platinum gold can reach more than 98%, which meets the application requirements of high-purity noble metal.

[0013] In a preferred embodiment, the cation exchange membrane is a perfluorosulfonic acid modified cation exchange membrane or an aromatic resin based modified cation exchange membrane with a thickness of 50-150 μm.

[0014] By adopting the above technical scheme, when the thickness of the cation exchange membrane is within the range, the migration rate of the cation can be ensured within a certain range, the stability of the membrane operation and the migration rate of the cation are ensured, in addition, the perfluorosulfonic acid modified cation exchange membrane or the aromatic resin based modified cation exchange membrane has good corrosion resistance, which ensures the continuity of the process.

[0015] In a preferred embodiment, the concentration of chloride ions in the anodic electrochemical dissolution solution is 2-6 mol / L, and the anodic electrochemical dissolution solution comprises water, hydrochloric acid and an additive in a mass ratio of 1: (0.5-2): (0.1-0.5).

[0016] In a preferred embodiment, the additive is one or more of sodium chloride, sodium chlorate and hydrogen peroxide.

[0017] By using the above technical solution, sodium chlorate and hydrogen peroxide can produce a synergistic effect with electrochemical oxidation to accelerate the dissolution of noble metals on the lining plate and improve the dissolution efficiency of noble metals; and the addition of sodium chloride not only provides chloride ions, but also improves the dissolution efficiency of noble metals due to the conductivity of sodium chloride in water.

[0018] In a preferred embodiment, in step S3, hydrochloric acid solution is added to the anodic electrochemical dissolution solution after each electrochemical dissolution to maintain the concentration of chloride ions in the anodic electrochemical dissolution solution at 2-6 mol / L.

[0019] By using the above technical solution, the application continuously adds hydrochloric acid to the anodic electrochemical dissolution solution, which not only provides sufficient chloride ions to complex noble metal ions, but also keeps the pH of the anodic electrochemical dissolution solution low, thereby avoiding the process of hydrolysis of base metal ions to generate precipitates or flocculants to adsorb or wrap noble metal ions and reduce their impact on the reduction of noble metal ions.

[0020] Further preferably, the multiple dissolutions are 8-40 times of electrochemical dissolution.

[0021] By using the above technical solution, by supplementing the anodic electrochemical dissolution solution with hydrochloric acid solution, there are always sufficient chloride ions in the dissolution solution to react with noble metal ions to form chloride complex ions, thereby maintaining the ion concentration balance and reaction activity of the electrochemical dissolution solution system, and using the recycling mode of repeated electrochemical dissolution and incremental addition of new electrochemical dissolution solution, the efficient saving of electrochemical dissolution solution resources and the substantial reduction of waste liquid discharge are realized.

[0022] In a preferred embodiment, the temperature of the gold ion reduction reaction in step S4 is 40-60℃, and further preferably, the reduction treatment refers to the crude gold powder obtained after reduction with a reducing agent sodium sulfite, 8-15% nitric acid or sulfuric acid solution is added, the temperature is controlled at 80-100℃, the stirring rate is 150-250 r / min, and the acid boiling reaction is carried out for 1.5-2 h, then the high-purity gold powder is obtained by washing with water.

[0023] In a preferred embodiment, in step S4, when the reduction potential of the anodic electrochemical dissolution solution is > 750 mV, the dropping speed of the reducing agent is 4-5 L / min, when the reduction potential of the anodic electrochemical dissolution solution is between 730-750 mV, the dropping speed of the reducing agent is 0.9-1.1 L / min, and when the reduction potential of the anodic electrochemical dissolution solution is ≤ 730 mV, the dropping is stopped, and the reaction is ended when the fluctuation range of the reduction potential of the anodic electrochemical dissolution solution is ≤ 10 mV.

[0024] According to the fact that the reduction potential of platinum ions is lower than that of gold ions, by detecting the reduction potential of the anodic electrochemical dissolution solution and the dropping speed of the reducing agent solution, it is ensured that platinum ions are not reduced in the process of gold reduction, and when the reduction potential is lower than 720 mV, it means that the reducing agent is excessive, and at this time, platinum ions are likely to be reduced to platinum gold, so in the present application, the reduction potential of the dissolution solution is controlled to be higher than 720 mV, which can improve the purity of gold and platinum gold.

[0025] In a preferred embodiment, in step S5, the adding amount of ammonium chloride is 1.0-2.5 times of the mass of platinum in the dissolution solution, the reaction temperature is 25-55℃, and the reaction time is 0.5-2 h.

[0026] In a preferred embodiment, in step S6, hydrazine hydrate is used as the reducing agent, the adding amount of hydrazine hydrate is 0.14-0.30 times of the mass of ammonium chloroplatinate, the reaction temperature is 60-80℃, and the reaction time is 1.0-1.5 h.

[0027] In a preferred embodiment, in step S1, the impurity removal and cleaning use a medicament which is a combination of one or more of organic acid, disodium EDTA, hydrogen peroxide and polyethylene glycol, and further preferably, the organic acid is one of citric acid, oxalic acid, tartaric acid, malic acid and succinic acid.

[0028] In a preferred embodiment, in step S1, the cleaning temperature is 35-55℃, and the cleaning time is 15-40 min.

[0029] In summary, the application has the following beneficial effects: through the synergistic optimization of the electrochemical dissolution parameters, the noble metal ion enrichment process and the step-by-step reduction steps, an efficient noble metal recovery system is constructed. On the one hand, the electrochemical dissolution link adopts a mixed system of low-concentration hydrochloric acid and chloride salt to replace the high-concentration aqua regia and other strong corrosive reagents in the traditional process, thereby reducing the generation of toxic gases. On the other hand, the electrochemical dissolution link adopts a low current density, which can effectively reduce the energy consumption and avoid the corrosion of the substrate. At the same time, the electrolysis temperature is controlled at 30-60 DEG C, so that the temperature can be maintained by using a low-power heating device, without the need for a high-power heating device. In addition, the noble metal ion enrichment link realizes the enrichment of noble metal ions through repeated electrolysis, without the need for additional evaporation of noble metal ion enrichment equipment, thereby further reducing the energy consumption and saving the cost. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the process flow chart of the recovery of noble metals from the semiconductor backing plate in the embodiments 1-5 of the application. DETAILED DESCRIPTION

[0031] The application will be further described below. Figure 1 The application will be further described below.

[0032] The following embodiments of the application are directed to the recovery of noble metals from the backing plate coated with gold and platinum. The backing plate substrate is stainless steel, and the backing plate contains an aluminum layer, and the gold and platinum coating layer is on the aluminum layer. In order to ensure that the base backing plate is not corroded and the noble metals can be effectively recovered, a low current density and a low electrochemical dissolution temperature are used in the process. In this process, the gold and platinum in the plating layer can be effectively oxidized into metal ions, and the stainless steel substrate can also be effectively prevented from being corroded in the process of electrochemical dissolution. After single dissolution, the undissolved backing plate is replaced, and hydrochloric acid is added to the electrolyte to control the content of chloride ions, so that the electrolyte can be recycled for 8-40 times, effectively reducing the discharge amount of wastewater, ensuring that the stainless steel substrate is not corroded, and realizing secondary use.

[0033] The specific production process flow chart of embodiments 1-5 is shown in Figure 1 .

[0034] Embodiment 1

[0035] An electrochemical dissolution method for recovering noble metals from a semiconductor backing plate, wherein the noble metals are gold and platinum, comprising the following steps:

[0036] S1, impurity removal and cleaning: the semiconductor backing plate is placed in a composite reagent composed of citric acid and EDTA-2Na in a mass ratio of 3:1, and is soaked and cleaned at a temperature of 40 DEG C for 25 min. After cleaning, the backing plate has no corrosion marks;

[0037] S2, electrochemical dissolution: the impurity-removed backing plate is placed in an anode basket as an anode, the surface of the anode basket is plated with a tantalum-iridium coating with a thickness of 5 μm, a titanium plate after passivation treatment by immersion in a 10% nitric acid solution for 30 min is used as a cathode, the anode electrochemical dissolution solution is a mixed solution containing chloride ions with a concentration of 2 mol / L, the cathode electrochemical dissolution solution is a hydrochloric acid solution with a concentration of 1.2 mol / L, a fluororesin-based modified cation exchange membrane (brand DuPont NaFion TM , model N-117) with a thickness of 80 μm is arranged between the cathode and the anode, the current density is controlled to be 20 A / m 2 , the electrochemical dissolution temperature is 45°C, the electrochemical dissolution time is 6 h, and the ion reaction equation of the process is:

[0038] Anode: Au + 4Cl ﹣ -3e ﹣ = AuCl4 ﹣

[0039] Pt + 6Cl ﹣ -4e ﹣ = PtCl6 2﹣

[0040] Cathode: 2H + + 2e ﹣ = H2↑

[0041] The mixed solution is composed of water, hydrochloric acid and sodium chloride with a mass ratio of 1:0.5:0.1;

[0042] S3, noble metal ion enrichment: after single dissolution, the backing plate is replaced, and the above electrochemical dissolution is repeated 8 times, a small amount of hydrochloric acid solution is supplemented after each electrochemical dissolution to make the chloride ion concentration in the anode electrochemical dissolution solution reach 2 mol / L, and then the anode electrochemical dissolution solution after multiple dissolutions is used repeatedly, and the noble metal ion enrichment is performed on the anode electrochemical dissolution solution after multiple dissolutions to make the Au 3＋ concentration reach 10 g / L, meeting the reduction requirement;

[0043] S4, gold reduction: the pH of the anode electrochemical dissolution solution after the noble metal ion enrichment is 1, a reducing agent sodium sulfite is added, the addition amount of sodium sulfite is 1.3 times of the theoretical mass of gold, the adding mode is that the sodium sulfite is configured into a sodium sulfite solution with a concentration of 20%, and the sodium sulfite solution is added into the anode electrochemical dissolution solution in a dropwise manner, the reduction potential of the dissolution solution is monitored during the dropwise adding process, when the reduction potential is greater than 750 mV, the dropwise adding speed is 4 L / min, when the reduction potential is between 730 mV and 750 mV, the dropwise adding speed is 1 L / min, when the reduction potential is less than or equal to 730 mV, the dropwise adding is stopped, and when the change amount of the reduction potential is 5 mV within 5 min (note that when the change amount of the reduction potential is less than or equal to 10 mV within 5 min, the surface gold ions have been completely reduced), it is indicated that the gold ions in the solution have been completely reduced, the reaction is stopped, the whole process is kept stirring, and the reduction reaction temperature is controlled to be 50 DEG C, after the reaction is completed, the generated crude gold powder is collected by filtration, and the ion reaction equation of the process is as follows:

[0044] 2AuCl4 ﹣ + 3SO3 2﹣ + 3H2O = 2Au↓+ 3SO4 2﹣ +6H + + 8Cl ﹣

[0045] S5, acid boiling: the crude gold powder is transferred into a reaction kettle, a nitric acid solution with a concentration of 10% is added, the temperature is increased to 85 DEG C, the temperature state is kept for 2 h, after the acid boiling is completed, the heating is stopped, and the temperature is naturally cooled to room temperature, the gold powder is separated from the acid solution by vacuum filtration, and then the gold powder is washed with deionized water until the pH of the washing liquid is 6, and high-purity gold powder is obtained by drying;

[0046] S6, platinum precipitation: the remaining anode electrochemical dissolution solution in step S4 is heated and boiled, hydrogen peroxide is added for oxidation, the concentration of the hydrogen peroxide is 30%, and the addition amount of the hydrogen peroxide is 0.4 times of the mass of platinum gold, so that all the divalent platinum ions in the electrolyte are oxidized into tetravalent platinum ions, then ammonium chloride is added to generate ammonium chloroplatinate precipitate, the reaction temperature is controlled to be 40 DEG C, the stirring speed is 100 r / min, the reaction time is 1 h, and the addition amount of the ammonium chloride is 1.5 times of the mass of platinum in the dissolution solution, after the reaction is completed, the generated ammonium chloroplatinate precipitate is light yellow, and the ion reaction equation of the process is as follows:

[0047] PtCl6 2- + 2NH4 + = (NH4)2PtCl6↓

[0048] S7, filtration: the vacuum filtration method is used to filter and separate the ammonium chloroplatinate precipitate to obtain ammonium chloroplatinate solid, the filter cake is washed with ammonium chloride solution for 5 times, then the filter cake is slurried with water, the mass ratio of ammonium chloroplatinate solid to water is 1:15, then sodium hydroxide solution is added to adjust the pH of the system to 8.5;

[0049] S8, hydrazine hydrate with a mass of 0.14 times of the ammonium chloroplatinate is added to the ammonium chloroplatinate solution, the reaction temperature is controlled at 70°C, the reaction time is 1.2h, after the reaction is completed, the generated platinum powder is collected by filtration, washed with pure water for 3 times, and dried at 80°C for 2h to obtain high-purity platinum powder, the ionic reaction equation of the reaction process is as follows:

[0050] 2PtCl6 2- + 3N2H4= 2Pt↓ +3N2↑+12Cl - +8H + 。

[0051] Example 2

[0052] The difference from example 1 is the adjustment of parameters in each step, which is as follows:

[0053] A method for electrochemically dissolving a semiconductor substrate to recover precious metals, wherein the precious metals are gold and platinum, comprising the following steps:

[0054] S1, impurity removal and cleaning: the semiconductor substrate is immersed in a composite reagent composed of oxalic acid and hydrogen peroxide with a mass ratio of 4:1 at a temperature of 50°C for 35min, and after cleaning, the substrate has no corrosion marks;

[0055] S2, electrochemical dissolution: the impurity-removed substrate is placed in an anode basket as an anode, the surface of the anode basket is coated with a tantalum-iridium coating with a thickness of 8μm, a titanium plate after passivation treatment by immersing in a 15% nitric acid solution for 25min is used as a cathode, the anode electrochemical dissolution solution is a mixed solution containing 3mol / L of chloride ions, the cathode electrochemical dissolution solution is a 1.8mol / L hydrochloric acid solution, a fluororesin-based modified cation exchange membrane (brand DuPont NaFion TM , model N-117) with a thickness of 120μm is arranged between the cathode and the anode, the current density is controlled at 10A / m 2 , the electrochemical dissolution temperature is 55°C, and the electrochemical dissolution time is 7h;

[0056] The mixed solution is composed of water, hydrochloric acid and sodium chlorate with a mass ratio of 1:1.2:0.2;

[0057] S3, noble metal ion enrichment: replace the liner after single dissolution, repeat the above electrochemical dissolution for 15 times, supplement a small amount of hydrochloric acid solution after each electrochemical dissolution to make the concentration of chloride ions in the anode electrochemical dissolution solution reach 3 mol / L, and enrich the noble metal ions in the anode electrochemical dissolution solution after multiple dissolutions to Au 3＋ The concentration reaches 15.8 g / L, meeting the reduction requirement;

[0058] S4, gold reduction: the pH of the anode electrochemical dissolution solution after noble metal ion enrichment is 0.8, a reducing agent sodium sulfite is added, the addition amount of sodium sulfite is 1.5 times of the theoretical mass of gold, the addition mode is that the sodium sulfite is configured into a sodium sulfite solution with a concentration of 20%, and is added into the anode electrochemical dissolution solution in a dropwise manner, the reduction potential of the dissolution solution is monitored during the dropwise addition, when the reduction potential is greater than 750 mV, the dropwise addition speed is 4.2 L / min, when the reduction potential is between 730-750 mV, the dropwise addition speed is 0.9 L / min, when the reduction potential is ≤730 mV, the dropwise addition is stopped, and when the change amount of the reduction potential is 2 mV within 5 min, it indicates that the gold ions in the solution have been completely reduced, the reaction is stopped, the whole process is kept stirring, and the reduction reaction temperature is controlled at 55°C, after the reaction is completed, the generated crude gold powder is collected by filtration;

[0059] S5, acid boiling: the crude gold powder is transferred to a reaction kettle, a 12% nitric acid solution is added, the temperature is raised to 90°C, and the acid boiling is kept at this temperature for 1.5 h, after the acid boiling is completed, the heating is stopped, and the temperature is naturally cooled to room temperature, the gold powder is separated from the acid solution by vacuum filtration, and then the gold powder is washed with deionized water until the pH of the washing liquid is 7, and high-purity gold powder is obtained by drying;

[0060] S6, platinum precipitation: the remaining anode electrochemical dissolution solution in step S4 is heated and boiled, hydrogen peroxide is added for oxidation, the concentration of the hydrogen peroxide is 20%, and the addition amount is 0.8 times of the mass of platinum gold, so that all the divalent platinum ions in the electrolyte are oxidized to tetravalent platinum ions, then ammonium chloride is added to react to generate ammonium chloroplatinate precipitate, the reaction temperature is controlled at 50°C, the stirring rate is 120 r / min, the reaction time is 1.5 h, and the addition amount of ammonium chloride is 2.2 times of the mass of platinum in the dissolution solution;

[0061] S7, filtration: the ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain ammonium chloroplatinate solid, the solid is washed with ammonium chloride solution for 5 times, then the filter cake is slurried with water, the mass ratio of ammonium chloroplatinate solid to water is 1:15, then sodium hydroxide solution is added to adjust the pH of the system to 9.0;

[0062] S8, to the ammonium chloroplatinate solution, add hydrazine hydrate with the mass of 0.18 times of the ammonium chloroplatinate, control the reaction temperature to be 75℃, the reaction time is 1.4h, after the reaction, filter the generated platinum powder, wash with pure water for 3 times, dry at 80℃ for 2h, get high purity platinum powder.

[0063] Example 3

[0064] The difference from example 1 is the adjustment of parameters in each step, as follows:

[0065] A method for electrochemically dissolving semiconductor substrates to recover precious metals, wherein the precious metals are gold and platinum, comprising the following steps:

[0066] S1, impurity removal and cleaning: place the semiconductor substrate in a composite reagent composed of tartaric acid and polyethylene glycol with a mass ratio of 2:1, soak and clean at a temperature of 35℃ for 15min, and the cleaned substrate has no corrosion marks;

[0067] S2, electrochemical dissolution: place the impurity-removed substrate in an anode basket as an anode, the surface of the anode basket is coated with a tantalum-iridium coating with a thickness of 3μm, a titanium plate treated by soaking in 8% nitric acid solution for 35min for passivation is used as a cathode, the anode electrochemical dissolution solution is a mixed solution with a chloride ion concentration of 4mol / L, the cathode electrochemical dissolution solution is a hydrochloric acid solution with a concentration of 0.5mol / L, a fluororesin-based modified cation exchange membrane (brand DuPont NaFion TM , model N-117) with a thickness of 50μm is arranged between the cathode and the anode, control the current density to be 5A / m 2 , the electrochemical dissolution temperature is 30℃, and the electrochemical dissolution time is 4h;

[0068] The mixed solution is composed of water, hydrochloric acid and hydrogen peroxide with a mass ratio of 1:2:0.5;

[0069] S3, precious metal ion enrichment: replace the substrate after single dissolution, repeat the above electrochemical dissolution for 40 times, supplement a small amount of hydrochloric acid solution after each electrochemical dissolution to make the chloride ion concentration in the anode electrochemical dissolution solution reach 4mol / L, and enrich the precious metal ions in the anode electrochemical dissolution solution after multiple dissolutions to make the Au 3＋ concentration reach 30g / L, meeting the reduction requirement;

[0070] S4, gold reduction: the pH of the anode electrochemical dissolution solution after the noble metal ion enrichment is 0.5, a reducing agent sodium sulfite is added, the addition amount of the sodium sulfite is 1.2 times of the theoretical mass of gold, the adding mode is that the sodium sulfite is configured into a sodium sulfite solution with a concentration of 20%, and the sodium sulfite solution is added into the anode electrochemical dissolution solution in a dropwise manner, the reduction potential of the dissolution solution is monitored during the dropwise adding process, when the reduction potential is greater than 750 mV, the dropwise adding speed is 4.4 L / min, when the reduction potential is between 730 mV and 750 mV, the dropwise adding speed is 0.95 L / min, when the reduction potential is less than or equal to 730 mV, the dropwise adding is stopped, and when the change amount of the reduction potential is 6 mV within 5 min, it is indicated that the gold ions in the solution have been completely reduced, the reaction is stopped, the whole process is kept stirring, and the reduction reaction temperature is controlled to be 40 ℃, after the reaction is completed, the generated crude gold powder is collected by filtration;

[0071] S5, acid boiling: the crude gold powder is transferred into a reaction kettle, a nitric acid solution with a concentration of 8% is added, the temperature is raised to 80 ℃, the acid boiling is kept for 2.5 h at the temperature, after the acid boiling is completed, the heating is stopped, and the temperature is naturally cooled to room temperature, the gold powder is separated from the acid solution by vacuum filtration, and then the gold powder is washed with deionized water until the pH of the washing liquid is 7, and high-purity gold powder is obtained by drying;

[0072] S6, platinum precipitation: the remaining anode electrochemical dissolution solution in step S4 is heated and boiled, hydrogen peroxide is added for oxidation, the concentration of the hydrogen peroxide is 15%, and the addition amount of the hydrogen peroxide is 1 times of the mass of platinum gold, so that all the divalent platinum ions in the electrolyte are oxidized into tetravalent platinum ions, then ammonium chloride is added to react to generate ammonium chloroplatinate precipitate, the reaction temperature is controlled to be 25 ℃, the stirring speed is 80 r / min, the reaction time is 0.5 h, the addition amount of the ammonium chloride is 1.2 times of the mass of the platinum in the dissolution solution, and the ammonium chloroplatinate precipitate with a light yellow color is generated after the reaction is completed;

[0073] S7, filtration: the ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain ammonium chloroplatinate solid, the ammonium chloroplatinate solid is washed with an ammonium chloride solution for 5 times, the filter cake is slurried with water, the mass ratio of the ammonium chloroplatinate solid to water is 1:15, then sodium hydroxide solution is added to adjust the pH of the system to 8.5;

[0074] S8, hydrazine hydrate with a mass of 0.22 times of the mass of the ammonium chloroplatinate is added into the ammonium chloroplatinate solution, the reaction temperature is controlled to be 60 ℃, the reaction time is 1 h, after the reaction is completed, the generated platinum powder is collected by filtration, washed with pure water for 3 times, and dried at 80 ℃ for 2 h, and high-purity platinum powder is obtained.

[0075] Example 4

[0076] The difference from example 1 is the adjustment of the parameters in each step, and the specific adjustment is as follows:

[0077] A method for recovering precious metals from a semiconductor substrate by electrochemical dissolution, wherein the precious metals are gold and platinum, comprising the following steps:

[0078] S1, impurity removal cleaning: placing the semiconductor substrate in a composite reagent composed of malic acid and EDTA-disodium in a mass ratio of 3:2, soaking and cleaning at a temperature of 45°C for 30 min, and the substrate has no corrosion marks after cleaning;

[0079] S2, electrochemical dissolution: placing the impurity-removed substrate into an anode basket as an anode, the surface of the anode basket is coated with a tantalum-iridium coating with a thickness of 7μm, a titanium plate after passivation treatment by soaking in a 12% nitric acid solution for 32 min is used as a cathode, the anode electrochemical dissolution solution is a mixed solution with a chloride ion concentration of 5mol / L, the cathode electrochemical dissolution solution is a hydrochloric acid solution with a concentration of 1.5mol / L, a fluororesin-based modified cation exchange membrane (brand DuPont NaFion TM , model N-117) with a thickness of 100μm is arranged between the cathode and the anode, the current density is controlled to be 30A / m 2 , the electrochemical dissolution temperature is 50°C, and the electrochemical dissolution time is 5h;

[0080] The mixed solution is composed of water, hydrochloric acid and sodium chloride in a mass ratio of 1:1.8:0.3;

[0081] S3, precious metal ion enrichment: replacing the substrate after single dissolution, repeating the above electrochemical dissolution for 30 times, supplementing a small amount of hydrochloric acid solution after each electrochemical dissolution to make the chloride ion concentration in the anode electrochemical dissolution solution reach 5mol / L, and enriching the precious metal ions in the anode electrochemical dissolution solution after multiple dissolutions to Au 3＋ concentration of 25g / L to meet the reduction requirements;

[0082] S4, gold reduction: the pH of the anode electrochemical dissolution solution after enrichment of the precious metal ions is 0.9, a reducing agent sodium sulfite is added, the amount of sodium sulfite added is 1.4 times the theoretical mass of gold, the adding method is to configure the sodium sulfite into a sodium sulfite solution with a concentration of 20%, and add it into the anode electrochemical dissolution solution in a dropwise manner, monitor the reduction potential of the dissolution solution during the dropwise addition process, when the reduction potential is greater than 750mV, the dropwise addition speed is 4.7L / min, when the reduction potential is between 730-750mV, the dropwise addition speed is 0.9L / min, when the reduction potential is ≤730mV, stop dropwise addition, and when the change amount of the reduction potential is 7mV within 5min, it indicates that the gold ions in the solution have been completely reduced, stop the reaction, the whole process is kept stirring, and the reduction reaction temperature is controlled to be 48°C, after the reaction is completed, the generated crude gold powder is collected by filtration;

[0083] S5, boiling acid: the crude gold powder is transferred to a reaction kettle, a 15% nitric acid solution is added, the temperature is raised to 88°C, and the temperature is maintained for 1.8h. After the acid boiling is completed, the heating is stopped, and the temperature is naturally cooled to room temperature. The gold powder and the acid solution are separated by vacuum filtration, and the gold powder is washed with deionized water until the pH of the washing liquid is 7. The high-purity gold powder is obtained by drying;

[0084] S6, platinum precipitation: the remaining anode electrochemical dissolution solution in step S4 is heated and boiled, and hydrogen peroxide is added for oxidation. The concentration of the hydrogen peroxide is 20%, and the amount of the hydrogen peroxide added is 0.6 times the mass of the platinum gold. The divalent platinum ions in the electrolyte are oxidized to tetravalent platinum ions. Ammonium chloride is then added to react to form ammonium chloroplatinate precipitate. The reaction temperature is controlled at 45°C, the stirring rate is 95r / min, the reaction time is 1.2h, and the amount of the ammonium chloride added is 2.5 times the mass of the platinum in the dissolution solution. After the reaction is completed, the yellowish ammonium chloroplatinate precipitate is formed;

[0085] S7, filtration: the ammonium chloroplatinate precipitate is separated by vacuum filtration to obtain ammonium chloroplatinate solid. The filter cake is washed with ammonium chloride solution for 5 times, then the filter cake is slurried with water at a mass ratio of 1:15, and then sodium hydroxide solution is added to adjust the pH of the system to 8.5.

[0086] S8, hydrazine hydrate is added to the ammonium chloroplatinate solution at a mass of 0.26 times the mass of the ammonium chloroplatinate. The reaction temperature is controlled at 72°C, and the reaction time is 1.3h. After the reaction is completed, the generated platinum powder is collected by filtration, washed with pure water for 3 times, and dried at 80°C for 2h to obtain high-purity platinum powder.

[0087] Example 5

[0088] The difference between example 1 and the present embodiment is the adjustment of the parameters in each step, which is as follows:

[0089] A method for electrochemically dissolving a semiconductor substrate to recover precious metals, wherein the precious metals are gold and platinum, comprising the following steps:

[0090] S1, impurity removal and cleaning: the semiconductor substrate is immersed in a complex reagent composed of succinic acid and EDTA-disodium at a mass ratio of 5:1 at a temperature of 55°C for 40min. After cleaning, the substrate has no corrosion marks;

[0091] S2, electrochemical dissolution: the impurity-removed backing plate is placed in an anode basket as an anode, a titanium plate with a tantalum-iridium coating of 3 μm in thickness and passivated by immersion in a 14% nitric acid solution for 28 min is used as a cathode, the anode electrochemical dissolution solution is a mixed solution with a chloride ion concentration of 6 mol / L, the cathode electrochemical dissolution solution is a hydrochloric acid solution with a concentration of 2.0 mol / L, a fluororesin-based modified cation exchange membrane (brand DuPont NaFion TM , model N-117) with a thickness of 150 μm is arranged between the cathode and the anode, the current density is controlled to be 40 A / m 2 , the electrochemical dissolution temperature is 60°C, and the electrochemical dissolution time is 4 h;

[0092] The mixed solution is composed of water, hydrochloric acid and sodium chloride at a mass ratio of 1:1.4:0.4;

[0093] S3, noble metal ion enrichment: after single dissolution, the backing plate is replaced, and the above electrochemical dissolution is repeated for 25 times. After each electrochemical dissolution, a small amount of hydrochloric acid solution is supplemented to make the chloride ion concentration in the anode electrochemical dissolution solution reach 6 mol / L. The anode electrochemical dissolution solution after multiple dissolutions is subjected to noble metal ion enrichment to make the Au 3＋ concentration reach 30 g / L, meeting the reduction requirement;

[0094] S4, gold reduction: after noble metal ion enrichment, hydrochloric acid is added to the anode electrochemical dissolution solution to adjust the pH to 1.2, and then a reducing agent, sodium sulfite, is added. The amount of sodium sulfite added is 1.5 times the theoretical mass of gold. The sodium sulfite is configured into a 20% sodium sulfite solution, and is added to the anode electrochemical dissolution solution in a dropwise manner. During the dropwise addition process, the reduction potential of the dissolution solution is monitored. When the reduction potential is greater than 750 mV, the dropwise addition speed is 5 L / min. When the reduction potential is between 730-750 mV, the dropwise addition speed is 0.9 L / min. When the reduction potential is ≤730 mV, the dropwise addition is stopped. When the change in reduction potential is 3 mV within 5 min, it indicates that the gold ions in the solution have been completely reduced. The reaction is stopped. The whole process is kept stirring, and the reduction reaction temperature is controlled to be 60°C. After the reaction is completed, the generated crude gold powder is collected by filtration;

[0095] S5, acid boiling: the crude gold powder is transferred to a reaction kettle, a 11% nitric acid solution is added, the temperature is raised to 92°C, and the acid boiling is maintained at this temperature for 1.6 h. After the acid boiling is completed, the heating is stopped, and the temperature is naturally cooled to room temperature. The gold powder and the acid solution are separated by vacuum filtration, and then the gold powder is washed with deionized water until the washing liquid pH is 6.5. The high-purity gold powder is obtained by drying;

[0096] S6, platinum precipitation: the remaining anode electrochemical dissolution solution in step S4 is heated to boiling, hydrogen peroxide is added for oxidation, the concentration of hydrogen peroxide is 25%, the amount of hydrogen peroxide added is 0.5 times the mass of platinum, so that all the divalent platinum ions in the electrolyte are oxidized to tetravalent platinum ions, then ammonium chloride is added to react to form ammonium chloroplatinate precipitate, the reaction temperature is controlled at 55°C, the stirring rate is 120 r / min, the reaction time is 2 h, the amount of ammonium chloride added is 2.3 times the mass of platinum in the dissolution solution, after the reaction is completed, light yellow ammonium chloroplatinate precipitate is generated;

[0097] S7, filtration: vacuum filtration is used to separate the ammonium chloroplatinate precipitate to obtain ammonium chloroplatinate solid, after washing with ammonium chloride solution for 5 times, the filter cake is slurried with water, the mass ratio of ammonium chloroplatinate solid to water is 1:15, then sodium hydroxide solution is added to adjust the pH of the system to 8.5;

[0098] S8, hydrazine hydrate is added to the ammonium chloroplatinate solution, the amount of hydrazine hydrate is 0.30 times the mass of ammonium chloroplatinate, the reaction temperature is controlled at 80°C, the reaction time is 1.6 h, after the reaction is completed, the generated platinum powder is collected by filtration, washed with pure water for 3 times, and dried at 80°C for 2 h to obtain high-purity platinum powder.

[0099] Comparative Example 1

[0100] A method for recovering precious metals by electrochemically dissolving a semiconductor substrate, which is different from Example 1 in that in step S2, the current density is 60 A / m 2 , the electrochemical dissolution temperature is 80°C, and the electrochemical dissolution time is 6 h, and the other steps are the same as in Example 1, after 6 h of dissolution, the surface of the semiconductor substrate has obvious pitting corrosion.

[0101] Comparative Example 2

[0102] A method for recovering precious metals by electrochemically dissolving a semiconductor substrate, which is different from Example 1 in that in step S2, the concentration of chloride ions in the anode electrochemical dissolution solution is 8 mol / L, and the other steps are the same as in Example 1, after 6 h of dissolution, the surface of the semiconductor substrate has obvious pitting corrosion.

[0103] Comparative Example 3

[0104] A method for recovering precious metals by electrochemically dissolving a semiconductor substrate, which is different from Example 1 in that in step S4, the dropping speed of the sodium sulfite solution is different, specifically as follows: when the reduction potential is > 750 mV, the dropping speed of the sodium sulfite solution is 8 L / min, when the reduction potential is between 730-750 mV, the dropping speed is 3 L / min, and when the reduction potential is ≤ 730 mV, the dropping is stopped and the crude gold powder is directly collected by filtration, and the other steps are the same as in Example 1.

[0105] Comparative Example 4

[0106] A method for recovering noble metal by electrochemically dissolving semiconductor substrate, which is different from example 1 in that the reduction potential in step S4 is different, specifically: when the reduction potential is 700 mV or higher, the dropping speed of sodium sulfite solution is 4 L / min, when the reduction potential is between 680-700 mV, the dropping speed is 1 L / min, and when the reduction potential is ≤680 mV, the dropping is stopped and the crude gold powder is collected by filtration, and the other steps are the same as example 1.

[0107] The purity and recovery rate of the gold powder and platinum powder obtained in the above examples and comparative examples are shown in Table 1.

[0108] Table 1 Recovery results of gold and platinum

[0109] Item Gold powder recovery % Gold powder purity % Platinum gold recovery % Platinum gold purity % Example 1 98.6 99.995 97.6 99.956 Example 2 96.7 99.992 98.7 99.954 Example 3 99.1 99.993 98.3 99.956 Example 4 98.7 99.996 97.6 99.957 Example 5 97.8 99.993 98.6 99.954 Comparative Example 1 99.4 99.991 97.2 99.893 Comparative Example 2 98.9 99.993 96.7 99.912 Comparative Example 3 98.2 95.794 94.6 99.943 Comparative Example 4 99.1 95.978 95.1 99.958

[0110] In combination with the recovery data of noble metal in Table 1:

[0111] The recovery rate obtained in examples 1-5 of the present application is 98% or more, the purity is 99.99% or more, the recovery rate of platinum gold is 97% or more, and the purity of platinum gold is 99.9% or more, indicating that the gold and platinum obtained by the present application not only have high purity, but also the yield of platinum and gold is effectively improved by the method of the present application.

[0112] When the current density, dissolution temperature and chloride ion concentration in the anode electrochemical dissolution solution during electrochemical dissolution of comparative example 1 and comparative example 2 exceed the limits of the present application, the semiconductor substrate has been corroded after electrochemical dissolution of comparative example 1 and comparative example 2, which will affect the secondary use of the substrate.

[0113] Comparative example 3 compared with example 1, when the dropping speed of the reducing agent is too fast, it will lead to the situation of local sodium sulfite excess, so the platinum ion will also be reduced, especially when the reduction potential is between 730-750 mV, the dropping speed is too fast, the reduction potential drops fast, when the reduction potential drops to 720 mV, the reducing agent has been excessive, and the platinum ion has also been reduced, resulting in the decrease of the purity of gold powder and the yield of platinum gold.

[0114] Comparative example 4 compared with example 1, when the reduction potential is 700 mV or higher, sodium sulfite solution is dropped at a faster speed, when the reduction potential is between 680-700 mV, the dropping speed is reduced, and when the reduction potential is lower than 680 mV, the dropping is stopped, but the purity of the gold powder and the recovery rate of the platinum gold are both reduced, the reason is that in the process of gold reduction, platinum ion is also reduced, resulting in the decrease of gold purity and platinum recovery rate.

[0115] The embodiments of the present application are preferred embodiments of the present application, and do not limit the protection scope of the present application, and therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for recovering precious metals, which are gold and platinum, from an electrochemical dissolution semiconductor substrate, characterized by, The method comprises the following steps: S1, cleaning the liner, the liner body is stainless steel, and the liner comprises an aluminum layer, and the aluminum layer comprises a gold and platinum coating; S2, electrochemical dissolution: the backing plate is used as an anode, the titanium plate after passivation treatment is used as a cathode, the anode electrochemical dissolution solution is an acid mixed solution containing chloride ions, the cathode electrochemical dissolution solution is a hydrochloric acid solution, a cation exchange membrane is arranged between the cathode and the anode, the current density is 5-40 A / m 2 , the electrochemical dissolution temperature is 30-60℃, the concentration of chloride ions in the anode electrochemical dissolution solution is 2-6 mol / L, the anode electrochemical dissolution solution comprises water, hydrochloric acid and an additive in a mass ratio of 1: (0.5-2): (0.1-0.5), and the additive is one or several of sodium chloride, sodium chlorate and hydrogen peroxide; S3, noble metal ion enrichment: repeating the above electrochemical dissolution, and performing noble metal ion enrichment on the anode electrochemical dissolution solution after multiple dissolutions to meet the reduction requirements; S4, gold reduction: gold ions in the anode electrochemical dissolution solution after the noble metal ion enrichment are reduced to obtain gold powder, the reducing agent is added in a dropwise manner, the adding amount of the reducing agent is 1.2-1.5 times the theoretical mass of gold, the reduction potential of the anode electrochemical dissolution solution is monitored to be greater than or equal to 720 mV, and the specific control of the reduction potential is as follows: when the reduction potential of the anode electrochemical dissolution solution is greater than 750 mV, the dropwise adding speed of the reducing agent is 4-5 L / min, when the reduction potential of the anode electrochemical dissolution solution is between 730 mV and 750 mV, the dropwise adding speed of the reducing agent is 0.9-1.1 L / min, and when the reduction potential of the anode electrochemical dissolution solution is less than or equal to 730 mV, the dropwise adding is stopped, and the reaction is ended when the fluctuation range of the reduction potential of the anode electrochemical dissolution solution is less than or equal to 10 mV; S5, platinum precipitation: the divalent platinum ions in the remaining anode electrochemical dissolution solution obtained in the step S4 are oxidized into tetravalent platinum ions, and then ammonium chloride is added to generate ammonium chloroplatinate precipitation; S6, the ammonium chloroplatinate is filtered, washed, and then reduced to obtain platinum powder.

2. The method of claim 1, wherein the method further comprises: The cation exchange membrane is a perfluorosulfonic acid modified cation exchange membrane or an aromatic resin based modified cation exchange membrane with a thickness of 50-150 μm. ​ 3. The method of claim 1, wherein the method further comprises: In the step S3, hydrochloric acid solution is supplemented into the anode electrochemical dissolution solution after each electrochemical dissolution to make the concentration of chloride ions in the anode electrochemical dissolution solution be 2-6 mol / L. ​ 4. The method of claim 1, wherein the method further comprises: In the step S4, the temperature of the gold ion reduction reaction is 40-60 ℃. ​ 5. The method of claim 1, wherein the method further comprises: In the step S5, the adding amount of ammonium chloride is 1.0-2.5 times the mass of platinum in the dissolution solution, the reaction temperature is 25-55 ℃, and the reaction time is 0.5-2 h. ​ 6. The method of claim 1, wherein the method further comprises: In the step S6, hydrazine hydrate is used as the reducing agent, the adding amount of hydrazine hydrate is 0.18-0.30 times the mass of ammonium chloroplatinate, the reaction temperature is 60-80 ℃, and the reaction time is 1.0-1.5 h. ​ 7. The method of claim 1, wherein the method further comprises: In the step S1, the cleaning agent is one or a combination of organic acid, disodium EDTA, hydrogen peroxide and polyethylene glycol, the cleaning temperature is 35-55 ℃, and the cleaning time is 15-40 min. ​

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