A method and system for waste co-disposal and resource utilization

Abstract

The application discloses a kind of waste collaborative disposal and resource utilization method and system, it is related to resource comprehensive utilization technical field.The waste collaborative disposal and resource utilization method includes: carrying out secondary water washing and filtering to red mud, obtain alkali-free red mud, first filtrate and second filtrate;Second filtrate and nickel-cobalt hydrometallurgy magnesium-containing wastewater carry out precipitation reaction and filtering, obtain heavy metal slag and third filtrate;Third filtrate and first filtrate carry out precipitation reaction and filtering, obtain magnesium hydroxide precipitate and fourth filtrate;Carbon dioxide and ammonia gas are introduced into fourth filtrate, carry out double decomposition reaction and filtering, obtain sodium bicarbonate precipitate and fifth filtrate;Fifth filtrate is evaporated crystallization and obtains ammonium sulfate.The waste collaborative disposal and resource utilization method provided by the application not only makes red mud meet environmental safety requirements, makes the alkali washed out of red mud realize resource utilization, but also realizes the resource utilization of nickel-cobalt hydrometallurgy magnesium-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of comprehensive resource utilization technology, and in particular to a method and system for the co-processing and resource utilization of waste. Background Technology

[0002] Red mud is a highly alkaline waste generated during alumina production. Due to its large quantity and strong alkalinity, red mud is difficult to utilize comprehensively. Currently, the main method of disposal is stockpiling, but this requires large areas of land and significant funds to construct and maintain red mud dams. Because of its small particle size and poor agglomeration properties, exposed red mud in open-air dams easily generates dust after weathering, polluting the surrounding atmosphere and reducing visibility. Furthermore, the strong alkalinity of untreated red mud is a major obstacle to its large-scale reuse or recycling.

[0003] During the nickel-cobalt hydrometallurgical process, when metals are extracted from the ore through processes such as acid leaching, extraction, and electrowinning, a large amount of acidic wastewater containing high concentrations of magnesium ions is generated. This type of wastewater typically has a low pH value (1.5-3.5) and a magnesium content of 5-30 g / L. It is also accompanied by impurities such as nickel, cobalt, and sulfate. If directly discharged, this acidic wastewater with high concentrations of magnesium ions can easily lead to increased water hardness and damage to the ecological environment.

[0004] Therefore, it is urgent to develop methods for treating red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes, in order to solve the problems of the difficulty in disposing of and utilizing the magnesium-containing wastewater from these processes. Summary of the Invention

[0005] The main objective of this invention is to propose a method and system for the co-processing and resource utilization of waste, aiming to solve the problems of difficult treatment and resource utilization of magnesium-containing wastewater from red mud and nickel-cobalt hydrometallurgical processes.

[0006] To achieve the above objectives, this invention proposes a method for the co-processing and resource utilization of waste, used to treat magnesium-containing wastewater from red mud and nickel-cobalt hydrometallurgical processes. The method includes the following steps:

[0007] The red mud is washed with water and then filtered to obtain primary washed red mud and first filtrate, the first filtrate containing hydroxide ions and sodium ions.

[0008] The primary washed red mud is washed with water and then filtered to obtain dealkalized red mud and a second filtrate, the second filtrate containing hydroxide ions and sodium ions.

[0009] The pH value of the second filtrate is adjusted to the first preset pH value, and then mixed with magnesium-containing wastewater from nickel-cobalt hydrometallurgical process to carry out a precipitation reaction, thereby obtaining a solution containing heavy metal slag. The solution containing heavy metal slag is filtered to obtain heavy metal slag and a third filtrate. The heavy metal slag contains nickel hydroxide precipitate and cobalt hydroxide precipitate, and the third filtrate contains hydroxide ions, sodium ions, sulfate ions and magnesium ions.

[0010] The third filtrate is mixed with the first filtrate to obtain a mixture. The pH value of the mixture is adjusted to a second preset pH value, and a precipitation reaction is carried out to obtain a solution containing magnesium hydroxide precipitate. The solution containing magnesium hydroxide precipitate is filtered to obtain magnesium hydroxide precipitate and a fourth filtrate. The fourth filtrate contains sodium ions and sulfate ions.

[0011] Carbon dioxide and ammonia are introduced into the fourth filtrate to carry out a double decomposition reaction, resulting in a solution containing sodium bicarbonate precipitate. The solution containing sodium bicarbonate precipitate is filtered to obtain sodium bicarbonate precipitate and a fifth filtrate, wherein the fifth filtrate contains sulfate ions and ammonium ions.

[0012] The fifth filtrate was evaporated and crystallized to obtain ammonium sulfate.

[0013] In one embodiment, the red mud includes Bayer process red mud.

[0014] In one embodiment, the step of washing the red mud with water and then filtering it to obtain primary washed red mud and a first filtrate includes:

[0015] When washing the red mud with water, the mass ratio of the red mud to water is 1:(2-4); and / or,

[0016] The washing time is 0.5 to 2 hours.

[0017] In one embodiment, the step of washing the primary washed red mud with water, followed by filtration to obtain dealkalized red mud and a second filtrate:

[0018] When washing the primary washed red mud, the mass ratio of the primary washed red mud to water is 1:(1-2); and / or,

[0019] The washing time is 0.5 to 2 hours.

[0020] In one embodiment, the first preset pH value is 8-9; and / or,

[0021] The second preset pH value is greater than 11.

[0022] In one embodiment, the method of adjusting the first preset pH value includes introducing carbon dioxide into the second filtrate; and / or,

[0023] The method of adjusting the second preset pH value includes adding the first filtrate to the mixture.

[0024] In one embodiment, the step of introducing carbon dioxide and ammonia into the fourth filtrate to carry out a metathesis reaction to obtain a solution containing sodium bicarbonate precipitate, and filtering the solution containing sodium bicarbonate precipitate to obtain sodium bicarbonate precipitate and a fifth filtrate:

[0025] The amount of carbon dioxide introduced is calculated based on a molar ratio of carbon dioxide to sodium ions in the fourth filtrate of (1–1.2):1; and / or,

[0026] The amount of ammonia gas introduced is calculated based on a molar ratio of ammonia gas to sodium ions in the fourth filtrate of (1–1.1):1; and / or,

[0027] The temperature of the metathesis reaction is 30℃~40℃, and the time of the metathesis reaction is 1~2h.

[0028] In one embodiment, the evaporation and crystallization temperature is 90°C to 110°C; and / or,

[0029] The water vapor obtained from the evaporation and crystallization is collected after condensation and used to wash the red mud or the primary washed red mud.

[0030] This invention also proposes a waste co-processing and resource utilization system for treating red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes. The system includes a red mud treatment unit and a magnesium-containing wastewater treatment unit from nickel-cobalt hydrometallurgical processes. The magnesium-containing wastewater treatment unit comprises a nickel-cobalt recovery treatment unit, a magnesium recovery treatment unit, a sodium bicarbonate production unit, and an ammonium sulfate production unit, all connected in sequence.

[0031] The red mud treatment unit includes a primary pulping unit, a first filtration unit, a primary washed red mud storage unit, a secondary pulping unit, and a second filtration unit connected in sequence, as well as a first filtrate storage unit connected to the first filtration unit and a second filtrate storage unit connected to the second filtration unit. The red mud is pulped and washed in the primary pulping unit, and the substances in the primary pulping unit are separated by the first filtration unit to obtain primary washed red mud and a first filtrate. The primary washed red mud is pulped and washed in the secondary pulping unit, and the substances in the secondary pulping unit are separated by the second filtration unit to obtain dealkalized red mud and a second filtrate.

[0032] The nickel-cobalt recovery and treatment unit includes a purification and precipitation unit, a third filtration unit, and a third filtrate storage unit connected in sequence. The purification and precipitation unit is connected to the second filtrate storage unit. The magnesium-containing wastewater from the nickel-cobalt hydrometallurgical process and the second filtrate undergo a precipitation reaction through the purification and precipitation unit, and the substances in the purification and precipitation unit are separated through the third filtration unit to obtain heavy metal slag and the third filtrate.

[0033] The magnesium recovery and treatment unit includes a magnesium removal precipitation unit, a fourth filtration unit, and a fourth filtrate storage unit connected in sequence. The magnesium removal precipitation unit is connected to the first filtrate storage unit and the third filtrate storage unit, respectively. The first filtrate and the third filtrate undergo a precipitation reaction through the magnesium removal precipitation unit, and the substances in the magnesium removal precipitation unit are separated through the fourth filtration unit to obtain magnesium hydroxide precipitate and the fourth filtrate.

[0034] The sodium bicarbonate production unit includes a sodium bicarbonate reaction unit, a fifth filtration unit, and a fifth filtrate storage unit connected in sequence. The sodium bicarbonate reaction unit is connected to the fourth filtrate storage unit. The fourth filtrate, carbon dioxide, and ammonia undergo a metathesis reaction in the sodium bicarbonate reaction unit, and the substances in the sodium bicarbonate reaction unit are separated by the fifth filtration unit to obtain sodium bicarbonate and the fifth filtrate.

[0035] The ammonium sulfate production unit includes an evaporation and crystallization unit, which is connected to the fifth filtrate storage unit and is used to evaporate and crystallize the fifth filtrate to obtain ammonium sulfate.

[0036] In one embodiment, the ammonium sulfate production unit further includes a water storage unit for collecting water condensed from evaporation and crystallization, and the water storage unit is connected to both the primary pulping unit and the secondary pulping unit.

[0037] This invention provides a method for the co-treatment and resource utilization of red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes. The method involves a two-stage pulping and washing process to remove free alkali from the surface of the red mud. The treated red mud has a Na2O (an indicator of red mud alkalinity) content of less than 1%, making it suitable for use in building materials such as cement sintered bricks and non-autoclaved bricks. Simultaneously, the washing liquid generated during the secondary washing process of the red mud, namely the first filtrate and the second filtrate, is collected. Utilizing the stronger alkalinity of the first filtrate compared to the second filtrate, the first and second filtrates are respectively applied to the heavy metal ion removal process and magnesium recovery process of the magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes, thus realizing the resource utilization of metallic magnesium in the wastewater. Furthermore, this invention also utilizes the wastewater generated from the treatment of magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes and the alkali removed from the red mud. By introducing carbon dioxide and ammonia into the magnesium-removed filtrate, sodium bicarbonate precipitate is obtained. The reacted solution is then filtered, and the collected filtrate is evaporated and crystallized to obtain ammonium sulfate. Therefore, the waste co-processing and resource utilization method provided by this invention, through water washing of red mud and the synergistic use of alkali, magnesium-containing wastewater from nickel-cobalt hydrometallurgical, greenhouse gases carbon dioxide and ammonia leached from the red mud, not only ensures that the red mud meets environmental safety requirements and facilitates subsequent resource utilization, but also enables the resource utilization of the alkali leached from the red mud and the resource utilization of magnesium-containing wastewater from nickel-cobalt hydrometallurgical. It achieves the synergistic treatment of waste gas, wastewater and solid waste. The adopted process is simple, has low treatment cost, and is easy to industrialize. It has the advantages of simple treatment method, low cost, low waste output and good economic benefits. It can be used to solve the problems of red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical which are difficult to treat and difficult to achieve resource utilization. Attached Figure Description

[0038] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of an embodiment of the waste co-processing and resource utilization system provided by the present invention.

[0040] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0043] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0044] Red mud is a highly alkaline waste generated during alumina production. Due to its large quantity and strong alkalinity, red mud is difficult to utilize comprehensively. Currently, the main method of disposal is stockpiling, but this requires large areas of land and significant funds to construct and maintain red mud dams. Because of its small particle size and poor agglomeration properties, exposed red mud in open-air dams easily generates dust after weathering, polluting the surrounding atmosphere and reducing visibility. Furthermore, the strong alkalinity of untreated red mud is a major obstacle to its large-scale reuse or recycling.

[0045] In the nickel-cobalt hydrometallurgical process, the extraction of metals from the ore through acid leaching, extraction, and electrowinning processes generates a large amount of acidic wastewater containing high concentrations of magnesium ions. This wastewater typically has a low pH (1.5-3.5) and a magnesium content of 5-30 g / L, along with impurities such as nickel, cobalt, and sulfate. Direct discharge of this high-concentration magnesium-containing acidic wastewater can easily lead to increased water hardness and damage the ecological environment. Therefore, it is urgent to develop methods for treating red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes to solve the problems of difficult disposal and resource utilization of this wastewater.

[0046] In view of this, the present invention proposes a method for the co-processing and resource utilization of waste, for treating magnesium-containing wastewater from red mud and nickel-cobalt hydrometallurgical processes. The method for the co-processing and resource utilization of waste includes the following steps:

[0047] The red mud is washed with water and then filtered to obtain primary washed red mud and first filtrate, the first filtrate containing hydroxide ions and sodium ions.

[0048] The primary washed red mud is washed with water and then filtered to obtain dealkalized red mud and a second filtrate, the second filtrate containing hydroxide ions and sodium ions.

[0049] The pH value of the second filtrate is adjusted to the first preset pH value, and then mixed with magnesium-containing wastewater from nickel-cobalt hydrometallurgical process to carry out a precipitation reaction, thereby obtaining a solution containing heavy metal slag. The solution containing heavy metal slag is filtered to obtain heavy metal slag and a third filtrate. The heavy metal slag contains nickel hydroxide precipitate and cobalt hydroxide precipitate, and the third filtrate contains hydroxide ions, sodium ions, sulfate ions and magnesium ions.

[0050] The third filtrate is mixed with the first filtrate to obtain a mixture. The pH value of the mixture is adjusted to a second preset pH value, and a precipitation reaction is carried out to obtain a solution containing magnesium hydroxide precipitate. The solution containing magnesium hydroxide precipitate is filtered to obtain magnesium hydroxide precipitate and a fourth filtrate. The fourth filtrate contains sodium ions and sulfate ions.

[0051] Carbon dioxide and ammonia are introduced into the fourth filtrate to carry out a double decomposition reaction, resulting in a solution containing sodium bicarbonate precipitate. The solution containing sodium bicarbonate precipitate is filtered to obtain sodium bicarbonate precipitate and a fifth filtrate, wherein the fifth filtrate contains sulfate ions and ammonium ions.

[0052] The fifth filtrate was evaporated and crystallized to obtain ammonium sulfate.

[0053] In the technical solution of this invention, free alkali on the surface of red mud is washed away through a two-stage pulping and washing process. The Na2O (an indicator of the alkalinity of red mud) content of the treated red mud is less than 1%, which can be used in building materials such as cement sintered bricks and non-autoclaved bricks. At the same time, the washing liquid generated in the second washing process of red mud, namely the first filtrate and the second filtrate, is collected. Taking advantage of the fact that the alkalinity of the first filtrate is stronger than that of the second filtrate, the first filtrate and the second filtrate are applied to the heavy metal ion removal process and magnesium recovery process of magnesium-containing wastewater from nickel-cobalt hydrometallurgical process, realizing the resource utilization of metallic magnesium in magnesium-containing wastewater from nickel-cobalt hydrometallurgical process. In addition, the technical solution of this invention also utilizes the wastewater generated from the treatment of magnesium-containing wastewater from nickel-cobalt hydrometallurgical process and the alkali washed away from the red mud. By introducing carbon dioxide and ammonia into the magnesium-removed filtrate, sodium bicarbonate precipitate is obtained, and the solution after the reaction is filtered. The collected filtrate is evaporated and crystallized to obtain ammonium sulfate. Therefore, the waste co-processing and resource utilization method provided by this invention, through water washing of red mud and the synergistic use of alkali, magnesium-containing wastewater from nickel-cobalt hydrometallurgical, greenhouse gases carbon dioxide and ammonia leached from the red mud, not only ensures that the red mud meets environmental safety requirements and facilitates subsequent resource utilization, but also enables the resource utilization of the alkali leached from the red mud and the resource utilization of magnesium-containing wastewater from nickel-cobalt hydrometallurgical. It achieves the synergistic treatment of waste gas, wastewater and solid waste. The adopted process is simple, has low treatment cost, and is easy to industrialize. It has the advantages of simple treatment method, low cost, low waste output and good economic benefits. It can be used to solve the problems of red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical which are difficult to treat and difficult to achieve resource utilization.

[0054] In the above treatment process, conventional pulping and washing are used to dealkalize the red mud. Since red mud contains Na₂O, which dissolves in water to produce hydroxide and sodium ions, the first and second filtrates collected after washing contain hydroxide and sodium ions. The magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes is acidic and contains not only magnesium ions but also heavy metal ions (such as nickel and cobalt ions) and sulfate ions. Therefore, the heavy metal ions can be precipitated first by passing the wastewater through the slightly weaker alkaline second filtrate, and then the magnesium ions can be precipitated through the slightly stronger alkaline first filtrate, thus achieving magnesium ion recovery. Because the fourth filtrate from magnesium hydroxide removal contains sulfate and sodium ions, it can be used to produce sodium bicarbonate and ammonium sulfate after introducing carbon dioxide and ammonia.

[0055] In embodiments of the present invention, the red mud includes Bayer process red mud. Bayer process red mud has a high pH value and strong alkalinity due to incomplete recovery of alkali solution. The technical solution of the present invention uses Bayer process red mud for the co-treatment and resource utilization of magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes.

[0056] In embodiments of the present invention, the red mud has a particle size of 5 μm to 20 μm. Smaller particle sizes increase the difficulty of water penetration and exchange, affecting the cleaning effect and potentially requiring more washes or higher water consumption. Furthermore, it is detrimental to the settling of red mud particles. The present invention sets the red mud particle size to 5 μm to 20 μm, which helps to improve the dissolution rate of alkaline substances in water, and the red mud particles settle more quickly, thus achieving a better cleaning effect.

[0057] In an embodiment of the present invention, in the step of washing the red mud with water and then filtering it to obtain primary washed red mud and a first filtrate, the mass ratio of red mud to water during washing is 1:(2-4). The free alkali on the surface of the red mud is removed by washing with water. The pH of the first filtrate is controlled by controlling the amount of water. Magnesium ions require a pH > 11 to be effectively removed; below 11, magnesium ions are not completely removed. The technical solution of the present invention sets the mass ratio of red mud to water to 1:(2-4), so that the pH of the first filtrate is between 11 and 13. Within this range, the mass ratio of red mud to water can be 1:2, 1:2.5, 1:3, 1:3.5, or 1:4.

[0058] In an embodiment of the present invention, in the step of washing the red mud with water and then filtering it to obtain primary washed red mud and a first filtrate, the washing time is 0.5 to 2 hours. Setting the washing time within the above range allows the red mud and water to come into full contact, achieving a better cleaning effect and efficiency. Within this range, the washing time can be 0.5 hours, 1 hour, 1.5 hours, or 2 hours.

[0059] In an embodiment of the present invention, in the step of washing the primary washed red mud with water, followed by filtration to obtain dealkalized red mud and a second filtrate, the mass ratio of the primary washed red mud to water during washing is 1:(1-2). The purpose of controlling the water volume is to control the pH of the second filtrate, allowing heavy metal ions to precipitate and be removed under alkaline conditions. The technical solution of the present invention sets the mass ratio of the primary washed red mud to water to 1:(1-2), so that the pH of the second filtrate is between 9 and 11.

[0060] In an embodiment of the present invention, in the step of washing the primary washed red mud with water, followed by filtration to obtain dealkalized red mud and a second filtrate, the washing time is 0.5 to 2 hours. Setting the washing time within the above range allows for sufficient contact between the primary washed red mud and water, achieving better cleaning effect and efficiency. Within this range, the washing time can be 0.5 hours, 1 hour, 1.5 hours, or 2 hours.

[0061] In an embodiment of the present invention, the first preset pH value is 8-9. Under this pH condition, heavy metal ions such as nickel ions and cobalt ions in magnesium-containing wastewater from nickel-cobalt hydrometallurgation react with hydroxide ions to form precipitates, as shown in the following reaction equation:

[0062] Ni 2+ +2OH - =Ni(OH)2↓;

[0063] Co 2+ +2OH - =Co(OH)2↓.

[0064] In an embodiment of the present invention, the second preset pH value is greater than 11. Under this pH condition, magnesium ions in magnesium-containing wastewater from nickel-cobalt hydrometallurgation react with hydroxide ions to form a precipitate, thereby recovering magnesium from the wastewater. The reaction equation for the corresponding precipitate is as follows:

[0065] Mg 2+ +2OH - =Mg(OH)2↓.

[0066] In an embodiment of the present invention, the method of adjusting the first preset pH value includes introducing carbon dioxide into the second filtrate.

[0067] While controlling the amount of the second filtrate and magnesium-containing wastewater can precipitate some metal slag, the pH of the solution gradually decreases as heavy metal slag precipitates, potentially leading to incomplete precipitation and ineffective removal. Adding carbon dioxide not only controls the pH to alkaline conditions but also generates a carbonate buffer solution with sodium hydroxide, stabilizing the pH at this alkaline level. This invention's technical solution, by passing carbon dioxide through the second filtrate to obtain a carbonate buffer solution with a pH of 8-9, facilitates complete heavy metal precipitation. Furthermore, this invention simultaneously treats red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes while also absorbing carbon dioxide, achieving synergistic treatment of waste gas, wastewater, and solid waste.

[0068] In an embodiment of the present invention, adjusting the second preset pH value includes adding the first filtrate to the mixture. The first filtrate is strongly alkaline. The technical solution of the present invention controls the amount of the first filtrate added to make the pH value of the solution greater than 11, without the need for additional alkaline substances such as sodium hydroxide or quicklime, and also facilitates the consumption of the first filtrate.

[0069] In an embodiment of the present invention, the step of introducing carbon dioxide and ammonia into the fourth filtrate to perform a metathesis reaction to obtain a solution containing sodium bicarbonate precipitate, and filtering the solution containing sodium bicarbonate precipitate to obtain sodium bicarbonate precipitate and a fifth filtrate:

[0070] The amount of carbon dioxide introduced is calculated based on a molar ratio of carbon dioxide to sodium ions in the fourth filtrate of (1-1.2):1.

[0071] In an embodiment of the present invention, the step of introducing carbon dioxide and ammonia into the fourth filtrate to perform a metathesis reaction to obtain a solution containing sodium bicarbonate precipitate, and filtering the solution containing sodium bicarbonate precipitate to obtain sodium bicarbonate precipitate and a fifth filtrate:

[0072] The amount of ammonia gas introduced is calculated based on the molar ratio of ammonia gas to sodium ions in the fourth filtrate being (1-1.1):1.

[0073] After carbon dioxide and ammonia are introduced into the fourth filtrate, the carbon dioxide and ammonia react first to produce ammonium bicarbonate. Sodium bicarbonate (baking soda) is then formed through a double decomposition reaction between ammonium bicarbonate and sodium salt. The reaction equation is as follows:

[0074] NH3·H2O + CO2 = NH4HCO3;

[0075] NH4HCO3+Na + =NaHCO3 + NH4 + .

[0076] In embodiments of the present invention, the temperature of the metathesis reaction is 30°C to 40°C, and the reaction time is 1 to 2 hours. Within this range, the temperature of the metathesis reaction can be 30°C, 32°C, 34°C, 36°C, 38°C, or 40°C, and the reaction time can be 1 hour, 1.5 hours, or 2 hours. In one embodiment of the present invention, the temperature of the metathesis reaction is set to 30°C, and the reaction time is 1 hour.

[0077] In embodiments of the present invention, the evaporation crystallization temperature is 90°C to 110°C. Within this range, the evaporation crystallization temperature can be 90°C, 95°C, 100°C, 105°C, or 110°C. In one embodiment of the present invention, the evaporation crystallization temperature is set to 100°C.

[0078] In an embodiment of the present invention, the water vapor obtained from the evaporation and crystallization is collected after condensation and used for washing the red mud or the primary washed red mud. Recycling the water generated during the evaporation and crystallization process can reduce costs and avoid resource waste.

[0079] This invention also proposes a waste co-processing and resource utilization system for treating red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes. Please refer to [link to relevant documentation]. Figure 1The waste co-processing and resource utilization system includes a red mud treatment unit and a magnesium-containing wastewater treatment unit from nickel-cobalt hydrometallurgical processes. The magnesium-containing wastewater treatment unit from nickel-cobalt hydrometallurgical processes includes a nickel-cobalt recovery treatment unit, a magnesium recovery treatment unit, a sodium bicarbonate production unit, and an ammonium sulfate production unit connected in sequence. Wherein:

[0080] The red mud treatment unit includes a primary pulping unit, a first filtration unit, a primary washed red mud storage unit, a secondary pulping unit, and a second filtration unit connected in sequence, as well as a first filtrate storage unit connected to the first filtration unit and a second filtrate storage unit connected to the second filtration unit. The red mud is pulped and washed in the primary pulping unit, and the substances in the primary pulping unit are separated by the first filtration unit to obtain primary washed red mud and a first filtrate. The primary washed red mud is pulped and washed in the secondary pulping unit, and the substances in the secondary pulping unit are separated by the second filtration unit to obtain dealkalized red mud and a second filtrate.

[0081] The nickel-cobalt recovery and treatment unit includes a purification and precipitation unit, a third filtration unit, and a third filtrate storage unit connected in sequence. The purification and precipitation unit is connected to the second filtrate storage unit. The magnesium-containing wastewater from the nickel-cobalt hydrometallurgical process and the second filtrate undergo a precipitation reaction through the purification and precipitation unit, and the substances in the purification and precipitation unit are separated through the third filtration unit to obtain heavy metal slag and the third filtrate.

[0082] The magnesium recovery and treatment unit includes a magnesium removal precipitation unit, a fourth filtration unit, and a fourth filtrate storage unit connected in sequence. The magnesium removal precipitation unit is connected to the first filtrate storage unit and the third filtrate storage unit, respectively. The first filtrate and the third filtrate undergo a precipitation reaction through the magnesium removal precipitation unit, and the substances in the magnesium removal precipitation unit are separated through the fourth filtration unit to obtain magnesium hydroxide precipitate and the fourth filtrate.

[0083] The sodium bicarbonate production unit includes a sodium bicarbonate reaction unit, a fifth filtration unit, and a fifth filtrate storage unit connected in sequence. The sodium bicarbonate reaction unit is connected to the fourth filtrate storage unit. The fourth filtrate, carbon dioxide, and ammonia undergo a metathesis reaction in the sodium bicarbonate reaction unit, and the substances in the sodium bicarbonate reaction unit are separated by the fifth filtration unit to obtain sodium bicarbonate and the fifth filtrate.

[0084] The ammonium sulfate production unit includes an evaporation and crystallization unit, which is connected to the fifth filtrate storage unit and is used to evaporate and crystallize the fifth filtrate to obtain ammonium sulfate.

[0085] The waste co-processing and resource utilization system provided by this invention uses a red mud treatment unit to dealkalize red mud and collects the washing liquid generated from the dealkalization process for resource utilization, reducing wastewater generation and achieving high economic benefits. A nickel-cobalt hydrometallurgical magnesium-containing wastewater treatment unit removes heavy metal impurities from the wastewater and recovers magnesium ions. This unit also produces sodium bicarbonate and ammonium sulfate, enabling the resource utilization of waste liquid generated from both the dealkalization and magnesium-containing wastewater treatment processes, thus reducing wastewater generation. The waste co-processing and resource utilization system provided by this invention has advantages such as low complexity, low cost, low waste output, and high economic benefits.

[0086] In an embodiment of the present invention, the ammonium sulfate production unit further includes a water storage unit for collecting water condensed during evaporation and crystallization, and the water storage unit is connected to both the primary pulping unit and the secondary pulping unit. Recycling the water generated during the evaporation and crystallization process can reduce costs and avoid resource waste.

[0087] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0088] The red mud samples and magnesium-containing wastewater samples from nickel-cobalt hydrometallurgical processes used in the various embodiments of the present invention are the same. The main chemical components of the red mud samples are shown in Table 1 (Bayer process red mud), and the main chemical components of the magnesium-containing wastewater samples from nickel-cobalt hydrometallurgical processes are shown in Table 2.

[0089] Table 1. Main chemical components (wt%) of Bayer process red mud

[0090]

[0091] Table 2. Main chemical components (mg / L) of magnesium-containing wastewater samples from nickel-cobalt hydrometallurgical processes.

[0092] <![CDATA[Mg 2+ ]]> <![CDATA[Ni 2+ ]]> <![CDATA[Co 2+ ]]> <![CDATA[Fe 2+ / Fe 3+ ]]> <![CDATA[Na + / K + ]]> <![CDATA[SO4 2- ]]> <![CDATA[Mn 2+ ]]> content 9000 450 100 1000 1500 25000 200

[0093] Example 1

[0094] A method for co-processing and resource utilization of waste includes the following steps:

[0095] (1) Add 3L of evaporated crystallization water to the primary pulping tank, turn on the stirring of the primary pulping tank, add 1kg of red mud (particle size 10μm), wash with water for 1h, and then filter to obtain 1.25kg of primary washed red mud and 2.75L of first filtrate.

[0096] (2) Add 2L of evaporated crystallization water and 1kg of primary water-washed red mud to the secondary pulping tank, turn on the secondary pulping tank to stir, wash for 1 hour, and then filter to obtain 1.2kg of dealkalized red mud and 1.8L of second filtrate.

[0097] (3) CO2 (aeration rate of 100 mL / min) was introduced into 1.8 L of the second filtrate to adjust the pH value of the second filtrate to 8-9. Then, 6 L of magnesium-containing wastewater from nickel-cobalt hydrometallurgical process was added to carry out a precipitation reaction. The heavy metal ions nickel and cobalt ions in the wastewater formed precipitates to obtain a solution containing heavy metal slag. The solution containing heavy metal slag was filtered to obtain 24 g of heavy metal slag and 7.8 L of the third filtrate.

[0098] (4) Mix 7.8L of the third filtrate with 2.6L of the first filtrate to obtain a mixture with a pH value greater than 11 and carry out a precipitation reaction to obtain a solution containing magnesium hydroxide precipitate. Filter the solution containing magnesium hydroxide precipitate to obtain 45g of magnesium hydroxide precipitate and 10.4L of the fourth filtrate.

[0099] (5) Introduce CO2 (aeration rate of 30 mL / min) and ammonia (aeration rate of 10 mL / min) into 10.4 L of the fourth filtrate and carry out a double decomposition reaction at 30 °C for 1 h to obtain a solution containing sodium bicarbonate precipitate. Filter the solution containing sodium bicarbonate precipitate to obtain 180 g of sodium bicarbonate precipitate and 10.4 L of the fifth filtrate.

[0100] (6) Evaporate and crystallize 10.4L of the fifth filtrate (the evaporation and crystallization temperature is 100℃) to obtain 190g of ammonium sulfate. The condensate from the evaporation and crystallization is returned to the pulp washing tank.

[0101] Results: The Na2O content of the red mud treated in this embodiment was 0.90%, the magnesium ion concentration in the wastewater decreased from 9000 mg / L to 6 mg / L, and the purity of the recovered magnesium hydroxide precipitate was 85%.

[0102] Example 2

[0103] Compared with Example 1, the difference is that in step (1), the amount of water added for evaporation and crystallization is 2.5L and the water washing time is 0.5h; in step (2), the amount of water added for evaporation and crystallization is 2L and the water washing time is 0.5h.

[0104] Results: The Na2O content of the red mud treated in this example was 0.87%, the magnesium ion concentration in the wastewater decreased from 9000 mg / L to 8 mg / L, and the purity of the recovered magnesium hydroxide precipitate was 86%.

[0105] Example 3

[0106] Compared with Example 1, the difference is that in step (1), the amount of water added for evaporation of crystallization is 4L and the water washing time is 1.5h; in step (2), the amount of water added for evaporation of crystallization is 1.5L and the water washing time is 2h.

[0107] Results: The Na2O content of the red mud treated in this embodiment was 0.82%, the magnesium ion concentration in the wastewater decreased from 9000 mg / L to 10 mg / L, and the purity of the recovered magnesium hydroxide precipitate was 83%.

[0108] Example 4

[0109] Compared with Example 1, the difference is that carbon dioxide is not introduced in step (3), and the amount of the second filtrate is 1.8L.

[0110] Results: In this example, 18g of heavy metal slag was obtained, 50g of magnesium hydroxide precipitate was obtained, and the purity of magnesium hydroxide was 68%.

[0111] Example 5

[0112] A waste co-processing and resource utilization system, such as Figure 1 As shown, it includes a red mud treatment unit and a magnesium-containing wastewater treatment unit from nickel-cobalt hydrometallurgical processes. The magnesium-containing wastewater treatment unit from nickel-cobalt hydrometallurgical processes includes a nickel-cobalt recovery treatment unit, a magnesium recovery treatment unit, a sodium bicarbonate production unit, and an ammonium sulfate production unit connected in sequence; wherein:

[0113] The red mud treatment unit includes a primary pulping unit, a first filtration unit, a primary washed red mud storage unit, a secondary pulping unit, and a second filtration unit connected in sequence, as well as a first filtrate storage unit connected to the first filtration unit and a second filtrate storage unit connected to the second filtration unit.

[0114] The nickel-cobalt recovery and processing unit includes a purification and precipitation unit, a third filtration unit, and a third filtrate storage unit connected in sequence. The purification and precipitation unit is connected to the second filtrate storage unit.

[0115] The magnesium recovery and treatment unit includes a magnesium removal precipitation unit, a fourth filtration unit, and a fourth filtrate storage unit connected in sequence. The magnesium removal precipitation unit is connected to the first filtrate storage unit and the third filtrate storage unit, respectively.

[0116] The sodium bicarbonate production unit includes a sodium bicarbonate reaction unit, a fifth filtration unit, and a fifth filtrate storage unit connected in sequence, and the sodium bicarbonate reaction unit is connected to the fourth filtrate storage unit.

[0117] The ammonium sulfate production unit includes an evaporation and crystallization unit and a water storage unit. The evaporation and crystallization unit is connected to the fifth filtrate storage unit, and the water storage unit is connected to the primary pulping unit and the secondary pulping unit.

[0118] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for the co-processing and resource utilization of waste, characterized in that, The method for co-processing and resource utilization of red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes includes the following steps: The red mud is washed with water and then filtered to obtain primary washed red mud and first filtrate, the first filtrate containing hydroxide ions and sodium ions. The primary washed red mud is washed with water and then filtered to obtain dealkalized red mud and a second filtrate, the second filtrate containing hydroxide ions and sodium ions. The pH value of the second filtrate is adjusted to the first preset pH value, and then mixed with magnesium-containing wastewater from nickel-cobalt hydrometallurgical process to carry out a precipitation reaction, thereby obtaining a solution containing heavy metal slag. The solution containing heavy metal slag is filtered to obtain heavy metal slag and a third filtrate. The heavy metal slag contains nickel hydroxide precipitate and cobalt hydroxide precipitate, and the third filtrate contains hydroxide ions, sodium ions, sulfate ions and magnesium ions. The third filtrate is mixed with the first filtrate to obtain a mixture. The pH value of the mixture is adjusted to a second preset pH value, and a precipitation reaction is carried out to obtain a solution containing magnesium hydroxide precipitate. The solution containing magnesium hydroxide precipitate is filtered to obtain magnesium hydroxide precipitate and a fourth filtrate. The fourth filtrate contains sodium ions and sulfate ions. Carbon dioxide and ammonia are introduced into the fourth filtrate to carry out a double decomposition reaction, resulting in a solution containing sodium bicarbonate precipitate. The solution containing sodium bicarbonate precipitate is filtered to obtain sodium bicarbonate precipitate and a fifth filtrate, wherein the fifth filtrate contains sulfate ions and ammonium ions. The fifth filtrate was evaporated and crystallized to obtain ammonium sulfate.

2. The method for co-processing and resource utilization of waste as described in claim 1, characterized in that, The red mud mentioned includes Bayer process red mud.

3. The method for co-processing and resource utilization of waste as described in claim 1, characterized in that, In the step of washing the red mud with water and then filtering it to obtain primary washed red mud and the first filtrate: When washing the red mud with water, the mass ratio of the red mud to water is 1:(2~4); and / or, The washing time is 0.5 to 2 hours.

4. The method for co-processing and resource utilization of waste as described in claim 1, characterized in that, In the step of washing the primary washed red mud with water and then filtering it to obtain dealkalized red mud and a second filtrate: When washing the primary washed red mud, the mass ratio of the primary washed red mud to water is 1:(1~2); and / or, The washing time is 0.5 to 2 hours.

5. The method for co-processing and resource utilization of waste as described in claim 1, characterized in that, The first preset pH value is 8~9; and / or, The second preset pH value is greater than 11.

6. The method for co-processing and resource utilization of waste as described in claim 1, characterized in that, The method of adjusting to the first preset pH value includes passing carbon dioxide into the second filtrate; and / or, The method of adjusting to the second preset pH value includes adding the first filtrate to the mixture.

7. The method for co-processing and resource utilization of waste as described in claim 1, characterized in that, In the step of introducing carbon dioxide and ammonia into the fourth filtrate to carry out a double decomposition reaction, obtaining a solution containing sodium bicarbonate precipitate, and filtering the solution containing sodium bicarbonate precipitate to obtain sodium bicarbonate precipitate and the fifth filtrate: The amount of carbon dioxide introduced is calculated based on a molar ratio of carbon dioxide to sodium ions in the fourth filtrate of (1~1.2):1; and / or, The amount of ammonia gas introduced is calculated based on a molar ratio of ammonia gas to sodium ions in the fourth filtrate of (1~1.1):1; and / or, The temperature of the metathesis reaction is 30℃~40℃, and the time of the metathesis reaction is 1~2h.

8. The method for co-processing and resource utilization of waste as described in claim 1, characterized in that, The evaporation and crystallization temperature is 90℃~110℃; and / or, The water vapor obtained from the evaporation and crystallization is collected after condensation and used to wash the red mud or the primary washed red mud.

9. A waste co-processing and resource utilization device, characterized in that, The equipment for co-processing and resource utilization of red mud and magnesium-containing wastewater from nickel-cobalt hydrometallurgical processes includes a red mud treatment unit and a magnesium-containing wastewater treatment unit. The magnesium-containing wastewater treatment unit comprises, in sequence, a nickel-cobalt recovery unit, a magnesium recovery unit, a sodium bicarbonate production unit, and an ammonium sulfate production unit; wherein: The red mud treatment unit includes a primary pulping unit, a first filtration unit, a primary washed red mud storage unit, a secondary pulping unit, and a second filtration unit connected in sequence, as well as a first filtrate storage unit connected to the first filtration unit and a second filtrate storage unit connected to the second filtration unit. The red mud is pulped and washed in the primary pulping unit, and the substances in the primary pulping unit are separated by the first filtration unit to obtain primary washed red mud and a first filtrate. The primary washed red mud is pulped and washed in the secondary pulping unit, and the substances in the secondary pulping unit are separated by the second filtration unit to obtain dealkalized red mud and a second filtrate. The nickel-cobalt recovery and treatment unit includes a purification and precipitation unit, a third filtration unit, and a third filtrate storage unit connected in sequence. The purification and precipitation unit is connected to the second filtrate storage unit. The magnesium-containing wastewater from the nickel-cobalt hydrometallurgical process and the second filtrate undergo a precipitation reaction through the purification and precipitation unit, and the substances in the purification and precipitation unit are separated through the third filtration unit to obtain heavy metal slag and the third filtrate. The magnesium recovery and treatment unit includes a magnesium removal precipitation unit, a fourth filtration unit, and a fourth filtrate storage unit connected in sequence. The magnesium removal precipitation unit is connected to the first filtrate storage unit and the third filtrate storage unit, respectively. The first filtrate and the third filtrate undergo a precipitation reaction through the magnesium removal precipitation unit, and the substances in the magnesium removal precipitation unit are separated through the fourth filtration unit to obtain magnesium hydroxide precipitate and the fourth filtrate. The sodium bicarbonate production unit includes a sodium bicarbonate reaction unit, a fifth filtration unit, and a fifth filtrate storage unit connected in sequence. The sodium bicarbonate reaction unit is connected to the fourth filtrate storage unit. The fourth filtrate, carbon dioxide, and ammonia undergo a metathesis reaction in the sodium bicarbonate reaction unit, and the substances in the sodium bicarbonate reaction unit are separated by the fifth filtration unit to obtain sodium bicarbonate and the fifth filtrate. The ammonium sulfate production unit includes an evaporation and crystallization unit, which is connected to the fifth filtrate storage unit and is used to evaporate and crystallize the fifth filtrate to obtain ammonium sulfate.

10. The waste co-processing and resource utilization equipment as described in claim 9, characterized in that, The ammonium sulfate production unit also includes a water storage unit, which is used to collect water condensed from evaporation and crystallization, and is connected to the primary pulping unit and the secondary pulping unit respectively.

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