A method for treating hazardous waste containing copper and high arsenic and its application

Abstract

This invention discloses a method for treating hazardous waste containing copper and high arsenic, and its application, relating to the fields of chemical and metallurgical technology. Specifically, the method includes the following steps: acid leaching of white dust, followed by solid-liquid separation to obtain acid leaching residue and acid leaching solution; adding goethite slag to the acid leaching solution for a first reaction to obtain ferric arsenate leaching residue and a first reaction solution; adding iron powder to the first reaction solution for a second reaction to obtain copper slag and a second reaction solution; and adding steel mill flue dust and an oxidant to the second reaction solution for a third reaction to obtain goethite slag and iron-removed liquid. This method treats copper- and high-arsenic hazardous waste white dust, producing only one type of ferric arsenate slag for storage, while other filter residues are uniform and can be sold at a price. It has excellent application prospects for achieving efficient recovery of valuable metals and high-value utilization of white dust.

Description

Technical Field

[0001] This invention relates to the field of chemical and metallurgical technology, and in particular to a method for treating hazardous waste containing copper and high levels of arsenic, and its application. Background Technology

[0002] During copper smelting, trace elements such as Pb, Zn, As, Sb, Bi, and Cd contained in the furnace feed are enriched in the flue dust (referred to as white dust). The treatment process for white dust is mainly wet extraction, with sulfuric acid leaching being the mainstream method. Essentially, this method utilizes the property that Pb, Bi, and their compounds are almost insoluble in dilute sulfuric acid solution. Through leaching, Pb and Bi are separated from metals such as Cu, Zn, In, and Cd, while a large amount of impurity elements such as As and Fe enter the leachate.

[0003] Currently, there are two main types of methods for separating arsenic from arsenic-containing solutions in sulfuric acid systems in related technologies: (1) Patent "A method for co-processing arsenic sulfide slag and arsenic-containing flue dust in copper smelting" (application number 202110999586.7), which uses arsenic sulfide slag to sulfide-precipitate copper in the acid leaching solution of flue dust. Ferrous sulfate (FeSO4) is added to the solution after copper precipitation, and reacts under oxygen pressure to generate arsenic sulfide (FeAsO4), which has high stability. However, a large amount of sulfuric acid is generated during the arsenic precipitation process. This excess sulfuric acid needs to be neutralized, which in turn generates a large amount of neutralization slag, which needs further treatment. (2) In the patent "A Method for Leaching Zinc Oxide and Copper White Dust" (application number 202210667812.6), zinc oxide and copper white dust are mixed and added to an acid leaching solution for neutral leaching treatment. Iron powder is added to the neutral leaching solution to achieve copper precipitation and dechlorination. Oxygen is introduced into the solution after copper precipitation and dechlorination, and oxygen pressure precipitation of iron is carried out under specific temperature, pressure and time conditions to remove arsenic, thereby generating ferric arsenate slag. However, only within a strict range of process parameters can arsenic be ensured to precipitate in the form of ferric arsenate.

[0004] In view of the above shortcomings, this study proposes a method for treating copper-containing high-arsenic hazardous waste, aiming to solve the problems of harmless treatment of intermediate products in copper smelting and comprehensive recovery of valuable metals. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for treating hazardous waste containing copper and high levels of arsenic.

[0006] The present invention also provides applications of the above method.

[0007] A method for treating copper- and high-arsenic hazardous waste according to a first aspect of the present invention includes the following steps:

[0008] (1) After acid leaching of white smoke dust, solid-liquid separation is performed to obtain acid leaching residue and acid leaching solution;

[0009] (2) Add goethite slag to the acid leaching solution to carry out the first reaction, and obtain arsenic iron leaching residue and the first reaction solution;

[0010] (3) Add iron powder to the first reaction solution to carry out a second reaction, and obtain copper slag and a second reaction solution;

[0011] (4) After adding steel plant ash and oxidant to the second reaction solution to carry out the third reaction, goethite slag and iron-removed liquid are obtained.

[0012] In some embodiments of the present invention, the white smoke dust includes arsenic-containing copper white smoke dust.

[0013] In some embodiments of the present invention, the white smoke dust comprises the following components by mass percentage: 2-8 wt% Cu, 5-20 wt% Pb, 2-15 wt% Zn, 1-5 wt% Bi, 4-15 wt% As, and 0.1-3 wt% Fe.

[0014] In some embodiments of the present invention, the white smoke dust comprises the following components by mass percentage: 4-8 wt% Cu, 10-20 wt% Pb, 6-10 wt% Zn, 1-3 wt% Bi, 4-10 wt% As, and 0.1-1 wt% Fe.

[0015] In some embodiments of the present invention, the white smoke dust comprises the following components by mass percentage: 5-7 wt% Cu, 10-15 wt% Pb, 8-10 wt% Zn, 2-3 wt% Bi, 4-8 wt% As, and 0.1-0.1 wt% Fe.

[0016] In some embodiments of the present invention, the acid solution used in the acid leaching treatment is a solution containing sulfuric acid.

[0017] In some embodiments of the present invention, the initial sulfuric acid concentration of the acid leaching treatment is 40 g / L-50 g / L.

[0018] In some embodiments of the present invention, the solid-liquid ratio of the white smoke dust to the sulfuric acid-containing solution is 1:(2~3) (mL / g).

[0019] In some embodiments of the present invention, the temperature of the acid leaching treatment is 80-90°C.

[0020] In some embodiments of the present invention, the acid leaching treatment time is 0.5 h to 2 h.

[0021] In some embodiments of the present invention, the final acid concentration of the acid leaching treatment is 2 g / L-7 g / L.

[0022] In some embodiments of the present invention, the final acid concentration of the acid leaching treatment is 4 g / L-6 g / L.

[0023] In some embodiments of the present invention, the solid-liquid separation is performed by pressure filtration.

[0024] In some embodiments of the present invention, the goethite slag may be the goethite slag prepared in step (4).

[0025] In some embodiments of the present invention, the first reaction is carried out in an autoclave.

[0026] In some embodiments of the present invention, the conditions for the first reaction are: a reaction temperature of 150-170°C, a pressure of 1-1.4 MPa, and an oxygen partial pressure of 0.4-0.8 MPa.

[0027] In some embodiments of the present invention, the conditions for the first reaction are: a reaction temperature of 155-165°C, a pressure of 1.1-1.3 MPa, and an oxygen partial pressure of 0.5-0.7 MPa.

[0028] In some embodiments of the present invention, the reaction time of the first reaction is 2-4 hours, specifically, it can be 2 hours, 3 hours, or 4 hours.

[0029] In some embodiments of the present invention, the molar ratio of copper to iron powder in the first reaction solution is 1:1-2.

[0030] In some embodiments of the present invention, the temperature of the second reaction is 70-75°C.

[0031] In some embodiments of the present invention, the second reaction takes 30-55 minutes.

[0032] In some embodiments of the present invention, the second reaction takes 40-50 minutes.

[0033] In some embodiments of the present invention, the steel plant ash comprises the following components by weight percentage: 1-15 wt% Fe, 0.1-1 wt% As, and 50-70 wt% Zn.

[0034] In some embodiments of the present invention, the steel plant ash comprises the following components by weight percentage: 2-10 wt% Fe, 0.2-0.8 wt% As, and 58-65 wt% Zn.

[0035] In some embodiments of the present invention, the time for the third reaction is 4-6 hours, specifically, it can be 4 hours, 5 hours, or 6 hours.

[0036] In some embodiments of the present invention, the iron content in the iron-removed liquid is ≤2g / L.

[0037] In some embodiments of the present invention, the pH value at the endpoint of the third reaction is 5.0-5.4.

[0038] In some embodiments of the present invention, the method further includes a step of removing impurities from the iron-removed liquid to prepare zinc sulfate heptahydrate.

[0039] In some embodiments of the present invention, the oxidant includes oxygen.

[0040] In some embodiments of the present invention, the oxidant includes oxygen-enriched air.

[0041] In some embodiments of the present invention, the oxygen concentration in the oxygen-enriched air is 35-40%.

[0042] According to a second aspect of the invention, the above method is proposed to be applied in any of the following:

[0043] 1) Recover valuable metals from white smoke dust;

[0044] 2) Arsenic removal from white smoke dust.

[0045] In some embodiments of the present invention, the valuable metals include lead, bismuth, arsenic, iron, copper, and zinc.

[0046] According to some embodiments of the present invention, at least the following beneficial effects are achieved:

[0047] 1. This invention provides a method for treating hazardous waste containing copper and high arsenic content. The method involves acid leaching of white flue dust. Cu, Zn, Fe, and As from the smelting slag enter the solution, while Pb, Bi, and other elements are enriched in the leaching residue and sold externally. The leachate is then treated in an autoclave, where iron powder is used to replace and precipitate copper to recover sponge copper. After copper precipitation, steel mill flue dust is added to the liquid during the iron removal process to form goethite slag. This goethite slag acts as an iron supplement for arsenic precipitation in the autoclave, causing approximately 95% of the arsenic to be deposited and converted into stable ferric arsenate precipitate. After iron removal, the liquid undergoes deep impurity removal to recover valuable metals such as Zn from the solution.

[0048] (1) Acid leaching of white smoke dust allows Cu, Zn, Fe, and As to enter the solution, while Pb and Bi elements remain in the leaching residue, ensuring that the recovery rate of Pb and Bi is greater than 95%;

[0049] (2) When goethite slag is used as an arsenic precipitant, the "acid swelling" phenomenon of FeSO4 arsenic precipitation will not occur during the high-pressure autoclave arsenic precipitation process, and no neutralization slag will be generated; and when goethite slag is used as an iron supplement for removing arsenic from white smoke dust acid leaching solution in high-pressure autoclave, the system arsenic and iron balance is achieved, so that ~95% of arsenic forms stable ferric arsenate slag, and the ferric arsenate content in the slag is greater than 80%;

[0050] (3) Use iron powder to replace copper precipitation to ensure that the copper recovery rate is greater than 95%. The added iron powder is processed through an iron removal process to produce goethite slag, which is returned to the autoclave as an iron supplement for arsenic precipitation, thus achieving "one iron for two uses";

[0051] (4) Use steel plant flue ash as a neutralizing agent in the iron removal process of goethite, control the pH at the end of iron removal to 5~5.4, and ensure that the liquid iron after iron removal is ≤2g / L;

[0052] 2. The method of this invention for treating copper- and high-arsenic hazardous waste white smoke dust produces only one type of ferric arsenate slag for storage, while other filter residues are uniform and can be sold at a price. It has a promising application prospect in achieving efficient recovery of valuable metals and high-value utilization of white smoke dust.

[0053] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0054] Figure 1 This is a process flow diagram of the present invention for treating hazardous waste containing copper and high arsenic. Detailed Implementation

[0055] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0056] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0057] In the description of this invention, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0058] In the description of this invention, it should be noted that, unless otherwise explicitly limited, terms such as "setup" and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0059] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0060] The term "not higher than" means less than or equal to, and should be understood to include the number itself.

[0061] The term "not less than" means greater than or equal to, and should be understood to include the number itself.

[0062] In the embodiments of this invention, the white dust involved is white dust produced as an intermediate product in copper smelting (containing approximately 6.19 wt% Cu, approximately 14.4 wt% Pb, approximately 8.59 wt% Zn, approximately 2.65 wt% Bi, approximately 6.24 wt% As, and approximately 0.78 wt% Fe) and steel mill dust (containing approximately 0.5 wt% As, approximately 62 wt% Zn, and approximately 2.56 wt% Fe). In the dust, Pb, Zn, and Cu mainly exist in the form of sulfates or oxides, while As mainly exists in the form of As₂O₃.

[0063] Example 1

[0064] This example provides a method for treating hazardous waste containing high levels of copper and arsenic. The method involves adding goethite slag from the iron removal process to an autoclave used in the acid leaching solution for treating white dust, using it as an iron source for arsenic precipitation from the white dust. This allows the arsenic in the solution to react with the iron to form FeAsO4. The process flow diagram is shown below. Figure 1 As shown, the main chemical reaction principle is as follows:

[0065] 2H3AsO3 + O2 → 2H3AsO4;

[0066] FeOOH + H₂O → Fe(OH)₃;

[0067] H3AsO4+Fe(OH)3→FeAsO4↓+3H2O.

[0068] The specific steps are as follows:

[0069] (1) White dust (containing 6.19 wt% Cu, 14.4 wt% Pb, 8.58 wt% Zn, 2.65 wt% Bi, 6.25 wt% As, and 0.78 wt% Fe) is uniformly fed into an acid leaching tank (white dust feed rate is 10 t / h) via a metering screw feeder, and mixed with sulfuric acid solution at a liquid-to-solid ratio of 2.5:1 (a liquid-to-solid ratio of (2~3):1 is acceptable) (mL / g). The sulfuric acid concentration in the resulting slurry is 45 g / L, and the total amount of sulfuric acid solution added is 26.75 m 3 / h. The reaction temperature is controlled within the range of 80-90℃ (85℃ in this example), the reaction time is 60min, and the final acid content is controlled not to exceed 5.5 g / L. After the reaction is completed, the material is cooled to below 70℃ and pumped to a filter press for filtration to separate lead-bismuth slag (containing 23.06wt.% Pb and 4.24wt.% Bi) and filtrate. The lead-bismuth slag is sold externally, and the filtrate is mixed with goethite slag returned from the iron removal process to form a slurry. The prepared slurry is then pumped to an autoclave via a relay pump.

[0070] (2) The reaction temperature of the high-pressure reactor was controlled at 160℃, the pressure was maintained at 1.2MPa, the oxygen partial pressure was set at 0.6MPa, and the reaction lasted for 3 hours. After the reaction was completed, the material was discharged into the flash tank to achieve rapid cooling and depressurization, and then transferred to the regulating tank for further cooling. Finally, the liquid and solid were separated by a thickener to obtain ferric arsenate leaching residue and high-pressure leachate. The ferric arsenate leaching residue (ferric arsenate slag, containing 28.89wt.% Fe and 29.47wt.% As) was stockpiled.

[0071] (3) Add iron powder (the amount of iron powder added is 0.55t / h, and the iron content of the iron powder is 98.50wt%) to the high-pressure leaching solution to replace the copper precipitation, control the temperature at 70-75℃ (72℃ in this example), and the reaction time is 45min. After the reaction is completed, the liquid and solid are separated to obtain the filter residue and the liquid after copper precipitation; the filter residue is sponge copper (containing 98.58wt.% Cu), which is sold externally;

[0072] (4) After copper precipitation, steel plant flue dust (containing 2.56 wt% Fe, 0.50 wt% As, and 62 wt% Zn, with an injection rate of 1.09 t / h) and oxygen-enriched air (with an injection rate of 100 m³ / h) are added to the liquid. 3 / h, the oxygen concentration in the oxygen-enriched air can be 35~40v%, in this example it is about 38v%), start stirring, the reaction time is 5h, the iron content of the final liquid is controlled to be ≤2g / L, the final pH is 5~5.4, after the reaction is completed, the liquid and solid are separated to obtain goethite slag and iron-removed liquid. The goethite slag is returned to the pre-reaming tank of the reactor and then pumped into the high-pressure reactor; the iron-removed liquid (containing Fe 1.84g / L, As 0.18g / L, Zn 49.09g / L) is subjected to deep impurity removal and sold or used to make zinc sulfate heptahydrate products.

[0073] The components of the separated lead-bismuth slag, ferric arsenate slag, sponge copper, and iron removal liquid were detected, the generated amounts were counted, and the copper recovery rate, zinc leaching rate, and arsenic removal rate were calculated.

[0074] Table 1

[0075]

[0076] The results are shown in Table 1. As can be seen from the table, the recovery rate of copper was 95.38%, the leaching rate of zinc was 98.33%, and the removal rate of arsenic was 95.55%.

[0077] Example 2

[0078] This example provides a method for treating hazardous waste containing copper and high levels of arsenic. The specific steps are as follows:

[0079] The specific steps are as follows:

[0080] (1) White dust (containing 5.25 wt% Cu, 14.40 wt% Pb, 8.59 wt% Zn, 2.65 wt% Bi, 6.54 wt% As, and 0.26 wt% Fe) is uniformly fed into an acid leaching tank (white dust feed rate is 10 t / h) via a metering screw feeder, and mixed with sulfuric acid solution at a liquid-to-solid ratio of 2.5:1 (solid-to-liquid ratio of (2~3):1 is acceptable) (mL / g). The sulfuric acid concentration in the resulting slurry is 45 g / L, and the total amount of sulfuric acid solution added is 22.88 m 3 / h. The reaction temperature is controlled within the range of 80-90℃ (85℃ in this example), the reaction time is 60min, and the final acid content is controlled not to exceed 5.5 g / L. After the reaction is completed, the material is cooled to below 70℃ and pumped to a filter press for filtration to separate lead-bismuth slag (containing 22.55wt.% Pb and 4.15wt.% Bi) and filtrate. The lead-bismuth slag is sold externally, and the filtrate is mixed with goethite slag returned from the iron removal process to form a slurry. The prepared slurry is then pumped to an autoclave via a relay pump.

[0081] (2) The reaction temperature of the high-pressure reactor was controlled at 160℃, the pressure was maintained at 1.2MPa, the oxygen partial pressure was set at 0.6MPa, and the reaction lasted for 3 hours. After the reaction was completed, the material was discharged into the flash tank to achieve rapid cooling and depressurization, and then transferred to the regulating tank for further cooling. Finally, the liquid and solid were separated by a thickener to obtain ferric arsenate leaching residue and high-pressure leachate. The ferric arsenate leaching residue (ferric arsenate slag, containing 28.01 wt.% Fe and 34.61 wt.% As) was stockpiled.

[0082] (3) Add iron powder (the amount of iron powder added is 0.47t / h, and the iron content of the iron powder is 98.50wt%) to the high-pressure leaching solution to replace the copper precipitation, control the temperature at 70-75℃ (72℃ in this example), and the reaction time is 45min. After the reaction is completed, the liquid and solid are separated to obtain the filter residue and the liquid after copper precipitation; the filter residue is sponge copper (containing 98.50wt.% Cu), which is sold externally;

[0083] (4) After copper precipitation, steel plant flue dust (containing 8.12 wt% Fe, 0.49 wt% As, and 61.90 wt% Zn, with an injection rate of 0.89 t / h) and oxygen-enriched air (with an injection rate of 100 m³ / h) are added to the liquid. 3 / h, the oxygen concentration in the oxygen-enriched air can be 35~40v%, in this example it is about 38v%), start stirring, the reaction time is 5 hours, control the iron content of the final liquid to ≤2g / L, the final pH=5~5.4, after the reaction is completed, the liquid and solid are separated to obtain goethite slag and iron-removed liquid. The goethite slag is returned to the pre-reaming tank of the reactor and then pumped into the high-pressure reactor; the iron-removed liquid (containing Fe 1.84g / L, As 0.17g / L, Zn 51.47g / L) is subjected to deep impurity removal and sold or used to make zinc sulfate heptahydrate products.

[0084] The components of the separated lead-bismuth slag, ferric arsenate slag, sponge copper, and iron removal liquid were detected, the generated amounts were counted, and the copper recovery rate, zinc leaching rate, and arsenic removal rate were calculated.

[0085] Table 2

[0086]

[0087] The results are shown in Table 2. As can be seen from the table, the recovery rate of copper was 90.24%, the leaching rate of zinc was 99.01%, and the removal rate of arsenic was 95.15%.

[0088] Comparative Example 1

[0089] This example provides a method for treating hazardous waste containing copper and high arsenic. The only difference from the steps in Example 1 is that the initial concentration of the white smoke dust and sulfuric acid mixture slurry is 55 g / L, and the final acid concentration of the acid leaching solution is controlled to be 10.13 g / L.

[0090] The components of the separated lead-bismuth slag, ferric arsenate slag, sponge copper, and iron removal liquid were detected, the generated amounts were counted, and the copper recovery rate, zinc leaching rate, and arsenic removal rate were calculated.

[0091] The slag rate of ferric arsenate (accounting for 21.06% of white dust) was 21.06%, the arsenic removal rate was 95.39%, and the copper recovery rate was 95.34%. High acid leaching had little impact on the copper recovery rate and arsenic removal rate.

[0092] The embodiments of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for treating hazardous waste containing high levels of copper and arsenic, characterized in that, Includes the following steps: (1) After acid leaching of white smoke dust, solid-liquid separation is performed to obtain acid leaching residue and acid leaching solution; (2) Add goethite slag to the acid leaching solution to carry out the first reaction, and obtain arsenic iron leaching residue and the first reaction solution; (3) Add iron powder to the first reaction solution to carry out a second reaction, and obtain copper slag and a second reaction solution; (4) After adding steel plant ash and oxidant to the second reaction solution to carry out the third reaction, goethite slag and iron-removed liquid are obtained; The white smoke dust comprises the following components by mass percentage: 2-8 wt% Cu, 5-20 wt% Pb, 2-15 wt% Zn, 1-5 wt% Bi, 4-15 wt% As, and 0.1-3 wt% Fe; The acid solution used in the acid leaching is a solution containing sulfuric acid; The acid leaching treatment is performed at a temperature of 80-90℃; The acid leaching treatment time is 0.5 h to 2 h; The final acid concentration of the acid leaching treatment is 2 g / L-7 g / L; The first reaction was carried out in an autoclave; The conditions for the first reaction are: temperature 150-170℃, pressure 1-1.4MPa, and oxygen partial pressure 0.4-0.8MPa; The reaction time for the first reaction is 2-4 hours; The steel plant flue dust comprises the following components by weight percentage: 1-15 wt% Fe, 0.1-1 wt% As, and 50-70 wt% Zn; The endpoint of the third reaction is at a pH of 5.0-5.

4.

2. The method according to claim 1, characterized in that, The temperature of the second reaction is 70-75℃; And / or, the second reaction takes 30-55 minutes.

3. The method according to claim 1, characterized in that, The third reaction takes 4-6 hours.

4. The method according to claim 1, characterized in that, The iron content in the liquid after iron removal is ≤2g / L; And / or, the oxidant includes oxygen-enriched air.

5. The application of the method according to any one of claims 1 to 4 in any of the following: 1) Recover valuable metals from white smoke dust; 2) Arsenic removal from white smoke dust.

6. The application according to claim 5, characterized in that, The valuable metals include lead, bismuth, arsenic, iron, copper, and zinc.

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