A method for highly valuably recovering metallic silver from waste IC chips by using soluble starch

Abstract

The present invention relates to the field of resource recovery and utilization of metallic silver in renewable resource-based solid waste, and discloses a method for high-value resource recovery of precious metal silver in waste IC chips, which is applicable to separating impurities such as Fe, Cu, and Si in waste IC chips, so as to resource-recover high-purity elemental Ag. Specifically, it includes the following steps: A. Pretreatment of chips; B. Leaching of metal elements in chips; C. Rapid separation of Fe impurity metals; D. High-value recovery of precious metal Ag; E. Recovery of metal Cu. The raw materials of the present invention are mainly IC chips recycled from those phased out, scrapped, and discarded from electronic factories. The precious metals are resource-recovered through a simple and easy-to-operate method. The prepared silver is spherical silver powder and can be used in industrial applications such as photocatalysts.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization, and more specifically, to a method for separating metallic silver from other metals in waste IC chips of electronic waste and then recycling silver resourcefully. Background Art

[0002] Since the 20th century, the industries related to electronic information technology have entered a stage of rapid development. China is a major consumer country of electronic products. Every year, 7 million tons of electronic products are discarded due to product iteration, and the quantity is still increasing at a rate of about 10-15% per year. According to the data released by the US Environmental Protection Agency, nearly 63 million tons of electronic waste will be generated globally in 2021, and 70%-80% of traditional electronic waste is directly landfilled without effective treatment, which not only pollutes the environment but also wastes resources. Electronic waste is a type of waste with resource properties. In the production process of electronic products, various materials such as multiple precious metals, heavy metals, non-ferrous metals, and polymer materials are used. The value of the metal materials in electronic waste is the same as their value before scrapping. Therefore, the resourceful recycling of electronic waste can effectively relieve the pressure of environmental governance, have certain environmental and economic benefits, and show a good development trend. Among them, IC chips are an important part of electronic waste and are widely used in the field of electronic equipment manufacturing. Therefore, it is urgent to properly handle these huge amounts of discarded IC chips.

[0003] Waste IC chips usually consist of 30% plastic, 30% inert oxides, and 40% valuable metals. The valuable metals mainly include 27% copper, 7% iron, 2% silicon, etc., and the precious metals are gold, silver, palladium, etc., which have high economic value. The currently known silver recovery processes for waste IC chips mainly include: (1) Pyrometallurgical process: A method that uses a metallurgical furnace to heat at high temperature to melt precious metals in other metal smelting materials or molten salts, and then treats the metal smelting materials or molten salts by methods such as refining or electrolysis to obtain precious metal products. However, the pyrometallurgical process has many defects, including incomplete metal separation and high energy consumption; (2) Hydrometallurgical process: A method that uses strong acids, strong alkalis, or strongly oxidizing solvents to leach and transfer the valuable metals in waste IC chips into a solution. Compared with the pyrometallurgical process, the hydrometallurgical process has the characteristics of simple process flow, convenient operation, less waste emissions, wide range of engineering industrial applications, and high economic benefits. However, the hydrometallurgical process has problems such as poor adaptability to fluctuations in waste circuit boards, inability to dissolve resin materials or ceramic-coated and solder-coated waste circuit boards with acid-base solutions, low precious metal recovery rate, and a large amount of acid-base waste liquid generated during the leaching process; (3) Biological treatment process: The principle is to use the redox action of the physiological metabolism process and metabolites of microorganisms to leach metals from electronic waste. Biotechnology has been favored by researchers due to its advantages of short process flow and environmental friendliness. However, because this technology mostly uses microorganisms as test materials, the requirements for the test environment are relatively harsh, so it is not easy to promote in industry and difficult to achieve industrial application.

[0004] The Chinese patent with the application number CN201210214213.5 and the authorization date of January 15, 2014 discloses a process for extracting gold and silver from waste circuit board chips and integrated circuits with extremely low pollution, simple and easy-to-understand process operation, and environmental protection, including the following steps: A. Removing electronic pins; B. Leaching silver, copper, and base metals; C. Extracting silver; D. Leaching gold from the filter residue; E. Reducing gold; The raw materials are mainly the gold and silver in the chips and integrated circuits recycled from the eliminated, scrapped, and waste circuit boards of electronic factories. Although this method can recover the metals in the chips, the overall process is cumbersome, the operation difficulty is large, and the detected purity is relatively low, and the inclusion of cheap metals affects the quality and value of precious metals.

[0005] The application number is CN202111588147.3, which discloses a method for extracting gold from oxidized roasted encapsulated chips. (1) Crush the circuit board chips to a certain size, and place the crushed powder in a muffle furnace for oxidized roasting; (2) After the oxidized roasting is completed, leach the obtained powder to remove copper; (3) Leach gold from the residue after copper removal to obtain a gold-containing leaching solution. The process idea of oxidized roasting chips - oxidized leaching to remove copper - chlorinated leaching to dissolve gold avoids the safety problems in the current gold extraction process by cyanidation method. At the same time, it avoids the chips being mixed into electronic waste for treatment and improves the metal recovery rate. However, this method requires more heat energy for separation, which is another kind of resource waste. At the same time, the acidic waste liquid and harmful gases generated during separation do not conform to the original intention of the current country's "waste-free city". Summary of the Invention

[0006] 1. Problems to be Solved

[0007] Aiming at the problem that precious metals (Ag) in new electronic waste IC chips cannot be quickly, efficiently and cleanly recycled, the present invention provides a new method for cleanly and low-energy recycling of precious metal ions in high-purity IC chips. The method of the present invention can recover the metals in the IC chips in a directional and step-by-step manner to the greatest extent. Through a clean and low-cost method, not only the precious metals are recovered, but also the low-value metals are highly purified and separated, maximizing the resource utilization of the IC chips and reducing secondary pollution at the same time.

[0008] 2. Technical Solutions

[0009] The purpose of the present invention is to provide a clean resource recycling technology for metallic silver in waste IC chips in view of the problems existing in the current process of recycling metals from waste IC chips, where it is difficult to cleanly and effectively separate silver from other cheap metals in the chips, resulting in low purity of the silver recovery product and inability to maximize its value, as well as generating a large amount of waste acid and waste alkali, causing environmental pollution and making it difficult to apply the IC chip resource utilization process in the industrial field. The present invention can cleanly and efficiently extract metallic silver from waste chips, thus achieving the result of resource recycling, and there is no need to add processes or purchase inhibitors additionally during the process, thus achieving the effects of resource utilization of waste IC chips and energy conservation and emission reduction.

[0010] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0011] A method for highly valuably recycling metallic silver from waste IC chips using soluble starch, comprising the following steps:

[0012] A. Pretreatment of chips: Heat to separate and crush the chips;

[0013] B. Metal leaching: The crushed chips after being treated in step A are leached with nitric acid under heating conditions; this enables the target components to transfer from the solid phase to the liquid phase, which is conducive to the subsequent recovery of heavy metals.

[0014] C. Selective separation of Fe: Soluble starch is added to the filtrate obtained by filtering in step B, and the mass concentration ratio of the soluble starch to the Fe content in the filtrate is 5.20 - 7.30; the mixture is subjected to a hydrothermal reaction at 130 - 175 °C, and the precipitate (hematite by-product) is separated; the following reaction occurs during this process:

[0015] 2Fe 3+ + 3H2O = Fe2O3↓ + 6H +

[0016]

[0017] D. Selective recovery of Ag: The filtrate after separating the precipitate in step C is subjected to a hydrothermal reaction at 160 - 230 °C, followed by solid-liquid separation. The filter residue is silver powder, and after drying, grinding, and sieving the filter residue solid, spherical silver powder can be obtained;

[0018] 4Ag + + 2H2O = 4Ag↓ + O2↑ + 4H +

[0019]

[0020] E. Recovery of Cu: Alkali is added to the filtrate obtained by solid-liquid separation in step D to form a precipitate of Cu, and the recovered Cu is separated.

[0021] Cu 2 ++ OH - = Cu(OH)2↓

[0022] Preferably, the hydrothermal reaction temperature in step D is higher than that in step C, and the temperature difference between the two is greater than 20 °C.

[0023] Preferably, the mass concentration ratio of the soluble starch to the Fe content in the filtrate in step C is further preferably 6.0 - 7.0.

[0024] Preferably, the reaction time of the hydrothermal reaction in step C is 320 - 400 min, and further preferably 355 - 365 min. Controlling the reaction time can achieve the control of the H + concentration, thereby controlling the hydrolysis of metal ions and ensuring the hydrolysis precipitation of iron ions while other ions do not precipitate.

[0025] Preferably, before the hydrothermal reaction in step C, the pH of the filtrate is adjusted to 0.3 ± 0.02.

[0026] Preferably, the hydrothermal reaction temperature in step C is further optimized to 140 - 160 °C.

[0027] Preferably, the hydrothermal reaction temperature in step D is further optimized to 160 - 190 °C.

[0028] Preferably, the reaction time of the hydrothermal reaction in step D is 560 - 640 min, and more preferably 595 - 605 min.

[0029] Preferably, the drying temperature of the filter residue solid in step D is 60 - 100 °C.

[0030] Preferably, the heating temperature in step B is 50 - 90 °C, and more preferably 65 - 75 °C, to improve the metal leaching rate and leaching rate.

[0031] Preferably, in step E, the added alkali adjusts the pH to 8.2 ± 0.05.

[0032] Preferably, the method specifically includes:

[0033] A. Chip pretreatment: Take waste IC chips, heat the glue connecting the chip heat sink and the chip with a hot air gun at 200 - 240 °C for 30 seconds, disassemble the heat sink, and the separated chips are crushed by a coarse crusher into chip crushing materials with a diameter of 2.5 - 1 cm, and then use a fine crusher to perform secondary crushing on them until the size is 0.3 cm;

[0034] B. Metal leaching: Pour the chip powder pretreated in step A into a glass beaker, add a 3 mol / L nitric acid solution according to a solid-liquid ratio of 1:3, stir and leach at a temperature of 50 - 90 °C on a heating stirrer, with a stirring rate of 300 r / min and a time of 1 - 2 h, and separate the solid and liquid by a centrifuge to obtain a solution containing silver and other metals and a filter residue alloy;

[0035] C. Selective separation of Fe: Measure the pH of the filtrate obtained by filtration in step B, then use nitric acid to adjust the pH of the filtrate to 0.3 ± 0.02, and measure the Fe content in the solution. Pour the solution into a reaction kettle, add soluble starch, and the mass concentration ratio of soluble starch to the Fe content in the solution is 5.20 - 7.30. After stirring evenly, cover it, and perform a hydrothermal reaction at 130 - 175 °C in a programmable temperature oven for 300 min. After the reaction, a brick-red precipitate appears at the bottom of the reaction kettle. Separate the solid and liquid by a centrifuge, collect the supernatant, and put the bottom precipitate into a drying oven to dry at 75 °C for 20 h. The bottom precipitate is the hematite by-product;

[0036] D. Selective cleaning and recovery of Ag: The filtrate after separating iron in step C is poured into a reaction kettle, and then the reaction kettle is tightly covered and reacted by hydrothermal method at 160 °C - 230 °C for 600 min. After the reaction, it is cooled to room temperature and solid-liquid separation is carried out using a centrifuge. The filter residue is silver powder. The filter residue solid is dried at 60 - 100 °C, ground and sieved to obtain spherical silver powder;

[0037] E. Cu recovery: After removing Fe, Al, and Ag from the chip leaching solution, Cu mainly exists in the supernatant. That is, the filtrate D obtained in the previous step is added with 7 mol / L NaOH, the pH is adjusted to 8.2 ± 0.05, and it is left standing at 30 °C for 5 h; Solid-liquid separation is carried out to collect the generated precipitate, and it is dried overnight at 80 °C.

[0038] 3. Beneficial effects

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) The present invention provides a method for highly valuably recovering metallic silver in waste IC chips by using soluble starch, without the need to add other redundant reagents. Only a little reagent with a very low market price is needed to recover and utilize the high-value precious metal. At the same time, other impurity low-value metals in the IC chips are also recycled. Compared with the existing pyrometallurgical recovery method, this method is more resource-saving and simpler, and only needs to rely on a reaction kettle without other equipment and instruments, with fast operation and high working efficiency; At the same time, compared with the existing methods for recovering metallic silver in waste IC chips, the method of the present invention can directionally separate and precipitate about 99.8% of Fe in the solution. The recovery rate of metallic silver by the method of the present invention is higher, with a purity of up to 98%. The recovered products can all be used as industrial raw materials and have considerable value.

[0041] (2) For the metal ions in waste IC chips, the method of the present invention successively adopts strategies of pretreatment, leaching, iron precipitation, silver recovery, and copper recovery. An excessive amount of soluble starch is used in the iron precipitation step, and the excessive soluble starch plays a role in the silver recovery step, further improving the recovery rate of metallic silver.

[0042] (3) Nitric acid is used in the leaching step of the present invention, and its effect is significantly better than that of hydrochloric acid and sulfuric acid;

[0043] (4) In the step of precipitating iron in the present invention, by controlling the heating temperature and time, the recovery rate of metallic silver can be further improved.

[0044] (5) No waste liquid or harmful gas is generated during the whole process of the method of the present invention. Compared with other methods for treating IC chips, it is more energy-saving and environment-friendly, achieving the recycling of metal resources and promoting the development of electronic waste treatment and disposal towards the direction of green, low-carbon, and sustainable. Description of the drawings

[0045] Figure 1 It is the XRD pattern of the crystal form of hematite, the high-value product recovered in step 3) of Example 1;

[0046] Figure 2 It is the SEM pattern of the crystal form of hematite, the high-value product recovered in step 3) of Example 1;

[0047] Figure 3 It is the XRF spectrum of the composition of hematite, the high-value product recovered in step 3) of Example 1;

[0048] Figure 4 It is the XRD pattern of the crystal form of silver, the high-value product recovered in step 4) of Example 1;

[0049] Figure 5 It is the SEM pattern of the morphology of silver, the high-value product recovered in step 4) of Example 1;

[0050] Figure 6 It is the XRF spectrum of the composition of silver, the high-value product recovered in step 4) of Example 1;

[0051] Figure 7 It is the XRD pattern of the crystal form of cupric hydroxide, the high-value product recovered in step 5) of Example 1;

[0052] Figure 8 It is the SEM pattern of the morphology of cupric hydroxide, the high-value product recovered in step 5) of Example 1;

[0053] Figure 9 It is the XRF spectrum of the composition of cupric hydroxide, the high-value product recovered in step 5) of Example 1;

[0054] Figure 10 It shows the removal of metals when the mass concentration ratio of soluble starch to Fe content in the solution is 3, 6.5, and 9 respectively in step 3) of Example 3;

[0055] Figure 11 It shows the influence of different hydrothermal reaction temperatures on the removal of metals in step 3) of Example 4;

[0056] Figure 12 It shows the influence of different hydrothermal reaction times on the removal of metals in step 3) of Example 5;

[0057] Figure 13 It shows the influence of using sulfuric acid leaching method on the removal of metals in step 3) of Comparative Example 1. Specific implementation method

[0058] The present invention will be further described below in conjunction with specific embodiments.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs.

[0060] For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. For example, soluble starch can be purchased through commercial channels.

[0061] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement, or value. One of ordinary skill in the art can readily determine the degree of flexibility for a particular variable.

[0062] Concentrations, amounts, and other numerical data may be presented herein in a range format. It should be understood that such range formats are used merely for convenience and brevity and should be interpreted flexibly as including not only the explicitly recited values as the limits of the range, but also all individual values or sub-ranges subsumed within that range as if each value and sub-range were explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted as including not only the explicitly recited limits of 1 to about 4.5, but also the individual numbers (such as 2, 3, 4) and sub-ranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges reciting only one numerical value, such as "less than about 4.5", which should be interpreted as including all of the above values and ranges. In addition, this interpretation should apply regardless of the breadth of the range or feature being described.

[0063] Any step recited in any method or process claim can be performed in any order and is not limited to the order recited in the claim.

[0064] Example 1

[0065] Taking a certain brand of used computer IC chips as raw materials, it is intended to recover metal ions in the waste IC chips by using soluble starch.

[0066] The specific implementation process of this example is as follows:

[0067] 1) Pretreatment of computer IC chips:

[0068] Take used computer IC chips, heat the glue connecting the chip heat sink and the chip with a hot air gun at 200 - 240 °C for 30 seconds, disassemble the heat sink, and the separated chips are crushed by a coarse crusher into chip crushing materials with a diameter of 0.5 - 1 cm, and then they are crushed a second time by a fine crusher to a size of about 0.3 cm.

[0069] 2) Leaching of metals in computer IC chips:

[0070] Pour the chip powder obtained after the treatment in step 1) into a glass beaker, add 3 mol / L nitric acid solution according to the solid-liquid mass ratio of 1:3, stir and leach at 80 °C on a heating stirrer, with a stirring rate of 300 rpm / min and a time of 2 h, and separate the solid and liquid by a centrifuge to obtain a solution containing silver and other metals and a small amount of filter residue.

[0071] 3) Selective separation of Fe:

[0072] Take the filtrate obtained by filtration in step 2), measure its pH using a pH meter, then adjust the pH of the filtrate to 0.3 ± 0.02 with nitric acid, and measure the Fe content in the solution. Pour the solution into a reaction kettle, add soluble starch, and the mass concentration ratio of soluble starch to the Fe content in the solution is 6.5. After stirring evenly, cover it, and react by hydrothermal method at 150 °C in a programmable temperature oven for 300 min. After the reaction, brick-red precipitate appears at the bottom of the reaction kettle. Separate the solid and liquid by a centrifuge, collect the supernatant, and put the bottom precipitate into a drying oven to dry at 80 °C for 20 h. The bottom precipitate is the hematite by-product, and the iron oxide content is 98.5%;

[0073] 4) High-efficiency recovery of Ag:

[0074] Pour the filtrate after separating iron in step 3) into a reaction kettle, then tightly cover the reaction kettle and react by hydrothermal method at 180 °C for 600 min. After the reaction, cool it to room temperature, take out the solid-liquid mixture in the kettle body and put it into a 50 ml centrifuge tube, and use a centrifuge to rotate at a speed of 8000 rpm for 8 min to separate the solid and liquid. The filter residue at the bottom after separation is silver powder. Dry the filter residue solid at 80 °C, grind it and sieve it to obtain spherical silver powder, and the silver purity is 98.9%;

[0075] 5) Cu recovery:

[0076] After removing Fe, Al, and Ag from the chip leaching solution, Cu mainly exists in the supernatant. That is, add 7 mol / L NaOH to the filtrate obtained in step 4), fully stir and adjust the pH to 8.2 ± 0.05 under stirring, and let it stand at 30 °C for 5 h. Use a centrifuge to separate the solid and liquid and collect the generated precipitate, and dry it overnight at 80 °C. The blue precipitate at the bottom is copper hydroxide precipitate, and the copper hydroxide purity is 93.4%.

[0077] Example 2

[0078] Using a certain brand of waste mobile phone IC chip as raw material, it is intended to recover metal ions in the waste IC chip by using soluble starch.

[0079] The specific implementation process of this example is as follows:

[0080] 2) Pretreatment of mobile phone IC chip:

[0081] Take the waste mobile phone IC chip, heat the glue connecting the chip heat sink and the chip with a hot air gun at 200 - 240 °C for 30 seconds, remove the heat sink, and the separated chip is crushed by a coarse crusher into chip crushing materials with a diameter of 0.5 - 1 cm. Then, use a fine crusher to perform secondary crushing until the particle size is about 1 mesh.

[0082] 2) Metal leaching from mobile phone IC chips:

[0083] Pour the chip powder obtained in step 1) into a glass beaker, add 3 mol / L nitric acid solution according to the solid-liquid mass ratio of 1:3, heat and stir on a heating stirrer at 90 °C for leaching with a stirring rate of 300 rpm / min for 1 h, and perform solid-liquid separation with a centrifuge to obtain a solution containing silver and other metals and a small amount of filter residue.

[0084] 3) Selective separation of Fe:

[0085] Take the filtrate obtained by filtration in step 2), measure its pH with a pH meter, then adjust the pH of the filtrate to 0.3 ± 0.02 with nitric acid, and measure the Fe content in the solution (3.2 g / L). Pour the solution into a reaction kettle, add soluble starch, and the mass concentration ratio of soluble starch to the Fe content in the solution is 6. After stirring evenly, cover it, and react in a programmed temperature chamber at 160 °C by hydrothermal method for 300 min. After the reaction, a brick-red precipitate appears at the bottom of the reaction kettle. Perform solid-liquid separation with a centrifuge, collect the supernatant, and put the bottom precipitate into a drying oven at 110 °C for drying for 20 h. The bottom precipitate is the hematite by-product, and the iron oxide content is 98.1%;

[0086] 4) Efficient recovery of Ag:

[0087] Pour the filtrate after separating iron in step 3) into a reaction kettle, then tightly cover the reaction kettle and react by hydrothermal method at 160 °C for 650 min. After the reaction, cool it to room temperature, take out the solid-liquid mixture in the kettle body and put it into a 50 ml centrifuge tube, and use a centrifuge to rotate at a speed of 8000 rpm for 12 min for solid-liquid separation. The filter residue at the bottom after separation is silver powder. Dry the filter residue solid at 100 °C, grind and sieve it to obtain spherical silver powder, and the silver purity is 99.9%;

[0088] 5) Cu recovery:

[0089] After removing Fe, Al, and Ag from the chip leaching solution, Cu mainly exists in the supernatant. That is, add 7 mol / L NaOH to the filtrate obtained in step 4), fully stir and adjust the pH to 8.2 ± 0.05 under stirring, and let it stand at 30 °C for 5 h. Perform solid-liquid separation with a centrifuge to collect the generated precipitate, and dry it overnight at 80 °C. The blue precipitate at the bottom is copper hydroxide precipitate, and the copper hydroxide purity is 95.0%.

[0090] Example 3

[0091] In this example, soluble starch was used to recover metal ions from waste IC chips. The waste IC chips treated were the same as those in Example 1, and the steps of the method were basically the same as those in Example 1, except that:

[0092] In step 3), the mass concentration ratios of soluble starch to the Fe content in the solution were 3, 6.5, and 9, respectively.

[0093] Experiments showed that when the mass concentration ratio of soluble starch to the Fe content in the solution in step C was 6.5, almost all iron could be removed, while silver and copper did not precipitate, as shown in the figure.

[0094] When the mass concentration ratio was 6.5, the removal effect was the best. However, when too much soluble starch was added, under the same reaction conditions, Ag would co-precipitate, affecting the purity of metal recovery and the retention rate of Ag.

[0095] Example 4

[0096] In this example, soluble starch was used to recover metal ions from waste IC chips. The waste IC chips treated were the same as those in Example 1, and the steps of the method were basically the same as those in Example 1, except that:

[0097] After adding soluble starch in step 3), the reaction was carried out at 90, 125, 150, and 180 °C for 300 min.

[0098] Experiments showed that the temperature of 150 °C was the most suitable. Too high or too low a temperature could not achieve the optimal removal effect of Fe and the high retention rate of Ag.

[0099] Example 5

[0100] In this example, soluble starch was used to recover metal ions from waste IC chips. The waste IC chips treated were the same as those in Example 1, and the steps of the method were basically the same as those in Example 1, except that:

[0101] After adding soluble starch in step C, the reaction was carried out at 150 °C for 60, 150, 300, and 600 min, respectively.

[0102] Experiments showed that the metal precipitation rates were different at different reaction times. In a short time, the removal rate of the cheap metal Fe was relatively low. If the reaction time was too long, Ag would co-precipitate.

[0103] Comparative Example 1

[0104] In this embodiment, soluble starch is used to recover metal ions from waste IC chips. The waste IC chips to be processed are the same as those in Embodiment 1, and the steps of the method are basically the same as those in Embodiment 1, except that:

[0105] In step B, the leaching is carried out using 3 mol / L hydrochloric acid or sulfuric acid.

[0106] Experiments show that hydrochloric acid and sulfuric acid will affect the leaching effect during leaching. Ag will react with hydrochloric acid, and the presence of sulfuric acid will inhibit the separation of metal Fe under the same conditions.

[0107] The above content is a schematic description of the present invention and its implementation manners. This description is not restrictive. What is shown in the embodiments is only one of the implementation manners of the present invention, and the actual implementation manners are not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it and design similar implementation manners and embodiments to this technical solution without creative efforts without departing from the purpose of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for highly valuably recovering metallic silver from waste IC chips by using soluble starch, characterized in that, It includes the following steps: A. Chip pretreatment: Heating to separate and crush the chip; B. Metal leaching: Using nitric acid to leach the crushed chip processed in step A under heating conditions; Transfer the target components from the solid phase to the liquid phase, which is beneficial to the recovery of heavy metals; C. Selective separation of Fe: Adjust the pH of the filtrate obtained by filtering in step B to 0.3±0.02 and add soluble starch thereto, and the mass concentration ratio of the soluble starch to the Fe content in the filtrate is 6.0 - 7.0; Carry out a hydrothermal reaction on the mixed solution at 140 - 160°C for 320 - 400 min, and separate the precipitate; D. Selective recovery of Ag: Carry out a hydrothermal reaction on the filtrate after separating the precipitate in step C at 160 - 230°C, carry out solid-liquid separation, and the filter residue is silver powder. The filter residue solid is dried, ground, and sieved to obtain spherical silver powder; E. Recovery of Cu: Add an alkali to the filtrate obtained by solid-liquid separation in step D to form a precipitate of Cu, and separate to obtain the recovered copper hydroxide.

2. The method for highly valuably recycling metallic silver from waste IC chips by using soluble starch according to claim 1, wherein The hydrothermal reaction temperature in step D is higher than that in step C, and the temperature difference between the two is greater than 20°C.

3. The method for highly valuably recycling metallic silver from waste IC chips by using soluble starch according to claim 2, wherein The hydrothermal reaction temperature in step D is 160 - 190°C.

4. The method for highly valuably recovering metallic silver from waste IC chips by using soluble starch according to claim 1, wherein The reaction time of the hydrothermal reaction in step D is 560 - 640 min.

5. The method for highly valuably recycling metallic silver from waste IC chips by using soluble starch according to claim 1, wherein, In step E, the added alkali makes the pH reach 8.2±0.

05.

6. The method for highly valuably recovering metallic silver from waste IC chips by using soluble starch according to any one of claims 1 to 5, characterized in that, It includes: A. Chip pretreatment: Take waste IC chips, use a hot air gun to heat the glue connecting the chip heat sink and the chip at 200 - 240°C for 30 seconds, disassemble the heat sink, and the separated chips are crushed by a coarse crusher into chip crushing materials with a diameter of 2.5 - 1 cm, and then use a fine crusher to carry out secondary crushing until the size is 0.3 cm; B. Metal leaching: Pour the chip powder pretreated in step A into a glass beaker, add a 3 mol / L nitric acid solution according to a solid-liquid ratio of 1:3, and carry out warm stirring leaching on a heating stirrer at a temperature of 50 - 90°C for 1 - 2 h, and carry out solid-liquid separation by a centrifuge to obtain a solution containing silver and other metals and a filter residue alloy; C. Selective separation of Fe: Measure the pH of the filtrate obtained by filtering in the process of step B, then use nitric acid to adjust the pH of the filtrate to 0.3±0.02, and measure the Fe content in the solution. Pour the solution into a reaction kettle, add soluble starch, and the mass concentration ratio of the soluble starch to the Fe content in the solution is 5.20 - 7.

30. After stirring evenly, cover it, and carry out a hydrothermal reaction in a programmed temperature box at 130 - 175°C for 300 min. After the reaction ends, a brick-red precipitate appears at the bottom of the reaction kettle. Carry out solid-liquid separation by a centrifuge, collect the supernatant, and put the bottom precipitate into a drying oven at 75°C for drying for 20 h. The bottom precipitate is the hematite by-product; D. Selective clean recovery of Ag: Pour the filtrate after separating iron in step C into a reaction kettle, then tightly cover the reaction kettle and carry out a hydrothermal reaction at 160°C - 230°C for 600 min. After the reaction, cool to room temperature and carry out solid-liquid separation by a centrifuge. The filter residue is silver powder. The filter residue solid is dried at 60 - 100°C, ground, and sieved to obtain spherical silver powder; E. Cu Recovery: After removing Fe, Al, and Ag from the chip leaching solution, Cu mainly exists in the supernatant. That is, add 7 mol / L NaOH to the filtrate D obtained in the previous step, adjust the pH to 8.2 ± 0.05, and let it stand at 30 °C for 5 h; separate the solid and liquid to collect the generated precipitate, and dry it overnight at 80 °C.

Images