A comprehensive treatment method of waste circuit board smelting cinder by fire process

Abstract

The present application relates to solid waste resource processing technical field, specifically to a kind of waste circuit board pyrometallurgy ash comprehensive processing method, comprising (1) with nitric acid leaching ash, filtration is obtained filter residue 1 and filtrate 1, (2) filter residue 1 is dried and then photolysis treatment is carried out, and the photolysis material obtained is leached with nitric acid and filtered, to obtain filtrate 2 and tin-rich residue, filtrate 2 is added with zinc powder to recover silver powder, and the remaining liquid and the filtrate 1 generated by acid leaching are combined and treated;(3) the filtrate 1 is first lead precipitation to obtain lead sulfate, and the remaining liquid after lead precipitation is obtained by replacement method to obtain copper powder, and the remaining liquid after copper replacement is added with ammonia water and filtered to obtain precipitate, the precipitate is washed with water, dried and calcined to obtain zinc oxide, and the remaining liquid is evaporated to recover ammonium nitrate.The present application realizes the separation and recovery of copper, lead, zinc, silver and tin, and the process flow is compact, and the metal recovery rate is high.

Description

A comprehensive treatment method for flue dust from pyrometallurgical processing of waste circuit boards Technical Field

[0001] This invention relates to a waste circuit board resource utilization technology, specifically to a comprehensive treatment method for pyrometallurgical ash from waste circuit boards. Background Technology

[0002] As the pace of product updates and replacements in the information and electronics industry accelerates, electronic products are being phased out and discarded at an increasingly faster rate. In order to reduce pollution from these waste electronic products and to reduce their quantity and make them more valuable, they are usually dismantled to obtain waste plastics, waste metals, and waste circuit boards, which can be used as recycling resources.

[0003] Waste circuit boards are the most valuable and difficult-to-process component of electronic waste. The bare boards after removing electronic components contain a large amount of valuable metals. Pyrometallurgical processes can facilitate large-scale and rapid processing and achieve high metal yields. However, pyrometallurgical smelting also generates a large amount of soot, such as flue ash, ash from the heating surfaces of waste heat boilers, and dust collector ash. This soot requires further harmless treatment. In fact, this soot is also enriched with cuprous halides, zinc oxide, lead oxide, tin dioxide, silver halides, etc., and may also contain trace amounts of iron. Therefore, it is necessary to comprehensively treat the soot from waste circuit board smelting to fully recover the valuable metal resources contained therein. Summary of the Invention

[0004] The purpose of this invention is to provide a method for processing pyrometallurgical ash from waste circuit boards, so as to separate and recover metals such as copper, lead, and zinc, while reducing environmental pollution from pyrometallurgical dust and ash.

[0005] To address the above problems, this invention provides a comprehensive treatment method for pyrometallurgical ash from waste circuit boards, comprising the following steps:

[0006] (1) Acid leaching of smoke and dust

[0007] The flue dust is leached with nitric acid. This utilizes the fact that cuprous halides, lead oxide, and zinc oxide are soluble in nitric acid, while silver halides and tin dioxide are insoluble, thus achieving the separation of copper, lead, and zinc from tin and silver. The flue dust leaching reaction is as follows: where X represents Cl or Br.

[0008] 3CuX+7HNO3=3Cu(NO3)2+NO↑+HX+3H2O

[0009] ZnO + 2HNO3 = Zn(NO3)2 + H2O

[0010] PbO + 2HNO3 = Pb(NO3)2 + H2O

[0011] The filtrate 1 produced by leaching the flue dust is a mixed solution of copper, lead, and zinc nitrates, and the filter residue 1 is a mixture of silver halide and tin dioxide.

[0012] (2) Silver-tin recycling

[0013] The main components of filter residue 1 are silver halide and tin dioxide. Silver halide is irradiated by light of certain specific wavelengths and decomposes into elemental silver and halogen elements. The halogen elements (Cl2 or Br2) produced by photolysis volatilize in the gaseous state at 90℃. The photolysis reaction is as follows: where X represents Cl or Br.

[0014] 2AgX = light = Ag + X2

[0015] The light sources used for the photolysis of silver halides include both ultraviolet and visible light. The shorter the wavelength of the light source and the higher the energy, the faster the photolysis rate.

[0016] The photolysate contains metallic silver and tin dioxide. Silver can be selectively leached with nitric acid, while tin dioxide remains in the leaching residue, thus achieving the separation of silver and tin.

[0017] 3Ag + 4HNO3 = 3AgNO3 + NO↑ + 2H2O

[0018] Silver nitrate solution can be reduced to metallic silver by zinc powder, or the silver ions can be converted into silver halide precipitate by hydrohalic acid.

[0019] Zn + 2AgNO3 = Zn(NO3)2 + 2Ag

[0020] AgNO3 + HX = AgX↓ + HNO3

[0021] If zinc powder is used for reduction, the by-product zinc nitrate solution can be combined with the nitric acid leachate from the flue ash for further treatment.

[0022] (3) Copper, lead and zinc recycling

[0023] The filtrate 1 produced by acid leaching of flue dust is first precipitated to remove lead, and then filtered to obtain lead sulfate, which can be used as a raw material for the production of metallic lead and lead salt products.

[0024] ZnSO4+Pb(NO3)2=PbSO4↓+Zn(NO3)2

[0025] (NH4)2SO4+Pb(NO3)2=PbSO4↓+2NH4NO3

[0026] The residual liquid from lead precipitation contains copper nitrate, which is recovered by replacing it with zinc powder.

[0027] Zn+Cu 2+ =Zn 2+ +Cu

[0028] The residual liquid after copper displacement is converted into a precipitate using ammonia or ammonium carbonate.

[0029] Zn(NO3)2+2NH3·H2O=Zn(OH)2↓+2NH4NO3

[0030] Zn(NO3)2+(NH4)2CO3=ZnCO3↓+2NH4NO3

[0031] Zinc precipitate is then washed and calcined to obtain zinc oxide.

[0032] Zn(OH)₂=ZnO+H₂O

[0033] ZnCO3=ZnO+CO2

[0034] The remaining liquid after zinc precipitation can be evaporated and crystallized to recover ammonium nitrate.

[0035] In this application, smoke and / or soot refers to dust such as flue dust generated during the pyrometallurgical smelting of waste circuit boards, dust accumulated on the heating surfaces of waste heat boilers, and dust collected from dust collectors.

[0036] The present invention provides a comprehensive resource-based treatment of ash and dust generated from the pyrometallurgical smelting of waste circuit boards, separating silver or silver halide, tin dioxide, lead sulfate, copper, and zinc oxide. The corresponding metals can then be obtained through conventional processing using existing technologies. This invention achieves the separation and resource utilization of copper, lead, zinc, silver, and tin, with a compact process flow and high metal recovery rate. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention.

[0038] Figure 1 is a process flow diagram of a comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to this embodiment. Detailed Implementation

[0039] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they should be performed in accordance with the techniques or conditions described in the literature in the field, or in accordance with the product manual.

[0040] In the description of this invention, unless otherwise stated, the terms "upper" and "lower" indicate the orientation or state relationship based on the orientation or state relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0041] In the following embodiments, all instruments and equipment used, unless otherwise specified, are conventional products that can be purchased through legitimate channels. Unless otherwise stated, all methods described are conventional methods, and all raw materials are available from publicly available commercial sources.

[0042] Example 1

[0043] As shown in Figure 1, this embodiment provides a comprehensive treatment method for pyrometallurgical ash from waste circuit boards, including the following steps:

[0044] (1) Acid leaching of soot

[0045] The fumes from the smelting of waste circuit boards were first leached with nitric acid at a temperature of 25°C, a liquid-to-solid ratio of 6:1 L / kg, and a time of 90 min. After leaching, the mixture was filtered to obtain filter residue 1 and filtrate 1.

[0046] (2) Silver-tin recycling

[0047] Filter residue 1 was dried at 80℃ for 4 hours, and then subjected to photolysis. The light source used for photolysis had a wavelength of 1 nm and an illuminance of 10,000 lx. During the photolysis process, the temperature of filter residue 1 was maintained at 90℃, and the photolysis time was 60 min per kilogram of filter residue 1. The powder after photolysis was leached with 1 mol / L nitric acid at a liquid-to-solid ratio of 3:1 L / kg at 70℃ for 40 min, and then filtered to obtain filtrate 2 and tin-rich slag. Zinc powder was added to filtrate 2 for reduction to obtain silver powder. The reduction and silver precipitation temperature was 70℃ for 20 min. The remaining liquid A and filtrate 1 produced from acid leaching of flue dust were combined and treated.

[0048] (3) Copper, lead and zinc recycling

[0049] The filtrate from the acid leaching of flue ash is first treated with zinc sulfate to precipitate lead, followed by filtration to obtain lead sulfate. The remaining lead-precipitated liquid is then treated with zinc powder to recover copper. The remaining copper-displaced liquid is treated with ammonia to precipitate zinc, followed by filtration. The resulting zinc hydroxide is washed, dried, and calcined to obtain zinc oxide. The remaining zinc-precipitated liquid undergoes crystallization to recover ammonium nitrate.

[0050] Using the above method to treat the pyrometallurgical smelting ash from waste circuit boards, the copper recovery rate reached 94%, the lead and zinc recovery rate reached 93%, and the silver recovery rate reached 98%.

[0051] Example 2

[0052] The method in this embodiment is basically the same as that in Embodiment 1, with the main difference being the selection of parameters.

[0053] (1) Acid leaching of soot

[0054] The ash from the smelting of waste circuit boards was first leached with nitric acid at a temperature of 40°C, a liquid-to-solid ratio of 3:1 L / kg, and a time of 60 min. After leaching, the residue was filtered to obtain filter residue 1 and filtrate 1.

[0055] (2) Silver-tin recycling

[0056] Filter residue 1 was dried at 120℃ for 2 hours, and then subjected to photolysis. The light source used for photolysis had a wavelength range of 800 nm and an illuminance of 100,000 lx. During the photolysis process, the temperature of filter residue 1 was maintained at 120℃, and the photolysis time was 90 min per kilogram of dry filter residue. The powder after photolysis was leached with 4 mol / L nitric acid at a liquid-to-solid ratio of 1:1 L / kg at 50℃ for 20 min, and then filtered to obtain filtrate 2 and tin-rich slag. Zinc powder was added to filtrate 2 for reduction to obtain silver powder and residual liquid A. The reduction and precipitation of silver was carried out at 40℃ for 40 min. The residual liquid from silver reduction and filtrate 1 from acid leaching of flue dust were combined and treated.

[0057] (3) Copper, lead and zinc recycling

[0058] The filtrate from the acid leaching of flue ash is first treated with zinc sulfate to precipitate lead, and then filtered to obtain lead sulfate. The remaining liquid after lead precipitation is replaced with zinc powder to obtain copper powder. The remaining liquid after copper replacement is mixed with the remaining liquid from silver reduction, and then ammonia water is added to precipitate zinc. The resulting zinc precipitate is washed with water, dried, and calcined to obtain zinc oxide powder. The remaining liquid after zinc precipitation is evaporated and crystallized to recover ammonium nitrate.

[0059] Using the above method to treat the pyrometallurgical smelting ash from waste circuit boards, the copper recovery rate reached 98%, the lead and zinc recovery rate reached 98%, and the silver recovery rate reached 94%.

[0060] Example 3

[0061] The method in this embodiment is basically the same as that in Embodiment 1, with the main difference being the selection of parameters.

[0062] (1) Acid leaching of soot

[0063] The ash from the smelting of waste circuit boards was first leached with nitric acid. The specific method had the following characteristics: leaching temperature 30℃, liquid-to-solid ratio 4:1 L / kg, and time 70 min. After leaching, the mixture was filtered to obtain filter residue 1 and filtrate 1.

[0064] (2) Silver-tin recycling

[0065] Filter residue 1 was dried at 100℃ for 3 hours, and then subjected to photolysis. The light source used for photolysis had a wavelength range of 5nm and an illuminance of 30,000 lx. During the photolysis process, the temperature of filter residue 1 was maintained at 100℃, and the photolysis time was 70 min per kilogram of dry filter residue. The powder after photolysis was leached with 2 mol / L nitric acid at a liquid-to-solid ratio of 2:1 L / kg at 60℃ for 30 min, and then filtered to obtain filtrate 2 and tin-rich slag. Zinc powder was added to filtrate 2 for reduction to obtain silver powder. The reduction and silver precipitation was carried out at 50℃ for 30 min. The residual liquid from silver reduction and filtrate 1 from acid leaching of flue dust were combined and treated.

[0066] (3) Copper, lead and zinc recycling

[0067] The filtrate from the acid leaching of flue ash is first treated with ammonium sulfate to precipitate lead, and then filtered to obtain lead sulfate. The remaining liquid after lead precipitation is treated with zinc powder to recover copper. The remaining liquid after copper displacement and the remaining liquid from silver reduction are treated with ammonium carbonate to precipitate zinc, and then filtered. The resulting zinc carbonate is washed with water, dried, and calcined to obtain zinc oxide. The remaining liquid after zinc precipitation is evaporated and crystallized to recover ammonium nitrate.

[0068] Using the above method to treat pyrometallurgical smelting ash from waste circuit boards, the copper recovery rate reached 95%, the lead and zinc recovery rate reached 96%, and the silver recovery rate reached 98%.

[0069] Example 4

[0070] The method in this embodiment is basically the same as that in Embodiment 1, with the main difference being the selection of parameters.

[0071] (1) Acid leaching of soot

[0072] The ash from the smelting of waste circuit boards was first leached with nitric acid. The specific method had the following characteristics: leaching temperature 35℃, liquid-to-solid ratio 4:1 L / kg, and time 80 min. After leaching, the residue was filtered to obtain filter residue 1 and filtrate 1.

[0073] (2) Silver-tin recycling

[0074] Filter residue 1 was dried at 100℃ for 3 hours, and then subjected to photolysis. The light source used for photolysis had a wavelength range of 30 nm and an illuminance of 20,000 lx. During the photolysis process, the temperature of filter residue 1 was maintained at 90℃, and the photolysis time was 60 min per kilogram of dry filter residue. The powder after photolysis was leached with 2 mol / L nitric acid at a liquid-to-solid ratio of 2:1 L / kg at 60℃ for 30 min, and then filtered to obtain filtrate 2 and tin-rich slag. Zinc powder was added to filtrate 2 for reduction to obtain silver powder. The reduction and silver precipitation was carried out at 50℃ for 30 min.

[0075] (3) Copper, lead and zinc recycling

[0076] The filtrate from the acid leaching of flue ash is first treated with ammonium sulfate to precipitate lead, and then filtered to obtain lead sulfate. The remaining liquid after lead precipitation is treated with zinc powder to recover copper. The remaining liquid after copper displacement and the remaining liquid from silver reduction are treated with ammonium carbonate to precipitate zinc, and then filtered. The resulting zinc carbonate is washed with water, dried, and calcined to obtain zinc oxide. The remaining liquid after zinc precipitation is evaporated and crystallized to recover ammonium nitrate.

[0077] Using the above method to treat pyrometallurgical smelting ash from waste circuit boards, the copper recovery rate reached 96%, the lead and zinc recovery rate reached 97%, and the silver recovery rate reached 97%.

[0078] Example 5

[0079] The method in this embodiment is basically the same as that in Embodiment 1, with the main difference being the selection of parameters.

[0080] (1) Acid leaching of soot

[0081] The ash from the smelting of waste circuit boards was first leached with nitric acid. The specific method had the following characteristics: leaching temperature 35℃, liquid-to-solid ratio 4:1 L / kg, and time 80 min. After leaching, the residue was filtered to obtain filter residue 1 and filtrate 1.

[0082] (2) Silver-tin recycling

[0083] Filter residue 1 was dried at 100℃ for 3 hours, and then subjected to photolysis. The light source used for photolysis had a wavelength range of 300 nm and an illuminance of 80,000 lx. During the photolysis process, the temperature of filter residue 1 was maintained at 90℃, and the photolysis time was 80 min per kilogram of dry filter residue. The powder after photolysis was leached with 2 mol / L nitric acid at a liquid-to-solid ratio of 2:1 L / kg at 60℃ for 30 min, and then filtered to obtain filtrate 2 and tin-rich slag. Zinc powder was added to filtrate 2 for reduction to obtain silver powder. The reduction and silver precipitation was carried out at 50℃ for 30 min.

[0084] (3) Copper, lead and zinc recycling

[0085] The filtrate from the acid leaching of flue ash is first treated with zinc sulfate to precipitate lead, followed by filtration to obtain lead sulfate. The remaining lead-precipitated liquid is then treated with zinc powder to recover copper. The copper-replaced liquid and the liquid from silver reduction are treated together with ammonia to precipitate zinc, followed by filtration. The resulting zinc hydroxide is washed, dried, and calcined to obtain zinc oxide. The remaining zinc-precipitated liquid is evaporated and crystallized to recover ammonium nitrate.

[0086] Using the above method to treat the pyrometallurgical smelting ash from waste circuit boards, the copper recovery rate reached 96%, the lead and zinc recovery rate reached 97%, and the silver recovery rate reached 96%.

[0087] As for other reagents with similar properties and the selection of similar reaction parameters, those skilled in the art can determine them based on common knowledge, and will not elaborate further. In addition, percentages in this application that are not explicitly stated are usually mass percentages, and will not be elaborated further.

[0088] The above descriptions are merely embodiments of the present invention. Commonly known structures, properties, and reactant ratios are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. For example, simply adjusting the parameter selection within or near a specified parameter range should also be considered within the scope of protection of the present invention, and these will not affect the effectiveness of the invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A comprehensive treatment method for flue gas ash from pyrometallurgical processing of waste circuit boards, characterized in that... The process includes the following steps: (1) Acid leaching of waste circuit board smelting ash is first leached with nitric acid, and then filtered to obtain filter residue 1 and filtrate 1; (2) Silver and tin recovery: after drying, filter residue 1 is subjected to photolysis treatment, and the obtained photolysis material is leached with nitric acid and then filtered to obtain filtrate 2 and tin-rich slag. A reducing agent is added to filtrate 2 to recover silver powder. The silver reduction temperature is 40-70℃ and the time is 20-40min; (3) Copper, lead and zinc recovery: first, lead is precipitated in filtrate 1 to obtain lead sulfate. The remaining liquid after lead precipitation is added to zinc powder or iron powder to replace copper powder. The remaining liquid after copper replacement is added to ammonia water or soluble carbonate to react and filter to precipitate. The precipitate is washed with water, dried and calcined to obtain zinc oxide. The remaining liquid after zinc precipitation is evaporated to recover ammonium nitrate.

2. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 1, characterized in that: In step (1), the leaching temperature is 25-40℃, the liquid-solid ratio of nitric acid solution to soot is 3:1-6:1 L / kg, and the time is 60-90 min.

3. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 1, characterized in that: In step (2), the wavelength of the light source used for photolysis is 0.01 to 800 nm, the illuminance is 10,000 to 100,000 lx, the temperature of filter residue 1 is maintained at 90 to 120°C during the photolysis process, and the photolysis time for each kilogram of filter residue 1 is 60 to 90 min.

4. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 1, characterized in that: In step (2), the filter residue 1 is dried at 80-120℃ for 2-4 hours.

5. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 1, characterized in that: In step (2), the concentration of nitric acid is 1-4 mol / L, the liquid-solid ratio of nitric acid to photolyzed material is 1:1-3:1 L / kg, the photolysis temperature is 50-70℃, and the photolysis time is 20-40 min.

6. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 1, characterized in that: The reducing agent used in step (2) includes at least one of zinc powder, copper powder, iron powder, formaldehyde, hydrazine hydrate and formic acid.

7. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 6, characterized in that: The reducing agent used in step (2) is zinc powder, and the remaining liquid from the silver reduction is added to filtrate 1 to recover the zinc.

8. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 1, characterized in that: The reagents used for lead precipitation in step (3) include sulfuric acid and soluble sulfates.

9. The comprehensive treatment method for pyrometallurgical ash from waste circuit boards according to claim 1, characterized in that: The soluble carbonates in step (3) include sodium carbonate, ammonium carbonate, or potassium carbonate.

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