Treatment method of papermaking pulping black liquor

Abstract

The invention belongs to the field of waste treatment and recovery. The invention provides a method for treating papermaking pulping black liquor, which comprises the following steps: mixing papermaking pulping black liquor with metal ion salt, carrying out cation replacement reaction to enable organic matters such as lignin and hemicellulose to generate repolymerization growth to obtain pretreatment liquid, and carrying out solid-liquid separation on the pretreatment liquid to obtain organic matters and a separation liquid, thereby completing treatment. And the separated organic matter solid is dried to obtain low-water-content powder, and the low-water-content powder can be subjected to subsequent thermochemical upgrading treatment to produce high-value chemicals. On the basis of a cation replacement principle, high-valence metal ions are adopted to replace sodium ions in a stable cluster formed by electronegative lignin colloidal particles and peripheral positive sodium ions in the black liquor, so that re-crosslinking and re-polymerization growth and separation of the lignin colloidal particles are realized, and the lignin colloidal particles are separated from the black liquor under the condition that reaction environments such as harsh acidity are not needed. And efficient, green and low-cost treatment of the black liquor is realized.

Description

Technical Field

[0001] The invention belongs to the field of waste treatment and recycling, and relates to a method for treating papermaking pulping black liquor. Background Art

[0002] Paper is an indispensable basic need in people's daily life. In the modern industrial system, the production process of the papermaking industry is complex and delicate, especially the pulping link as the core starting point of the papermaking industry, which directly determines the quality and production cost of paper. The general process of the papermaking industry can be roughly divided into several key steps such as raw material preparation, pulping, papermaking, post-processing and finished product packaging. Among them, pulping is the process of converting raw materials (such as wood, bamboo, waste paper, etc.) into pulp suitable for papermaking. According to the type of raw materials and pulping methods, pulp can be divided into chemical pulp, mechanical pulp, semi-chemical pulp and other types, and chemical pulp is widely used because of its high cellulose content and good paper quality.

[0003] The dry ingredients of pulp are mainly composed of three components: cellulose, hemicellulose and lignin. Cellulose is the main component of plant cell walls and the most important fiber source in the papermaking process. It gives paper strength and durability. Hemicellulose exists as a byproduct of cellulose and has a certain effect on the softness and water absorption of paper. Lignin is a complex aromatic polymer. Although it contributes to the strength of paper, it is often regarded as an impurity that needs to be removed during the pulping process because its presence affects the bleaching effect of pulp and the whiteness of the final paper.

[0004] In the process of pulping, the kraft process (also known as kraft cooking) and the caustic soda process (also known as causticizing process) are two commonly used chemical pulping methods. Both methods can effectively separate cellulose from lignin and hemicellulose in raw materials such as wood to form pulp. However, this process will produce a large amount of black liquor containing a large amount of organic matter, mainly lignin. This black liquor has a very high pollution load due to its high concentration of lignin, organic pollutants and chemicals, and direct discharge will cause serious damage to the water environment. It is often difficult for sewage treatment plants to effectively treat black liquor using traditional sewage treatment technology. At present, pulp mills usually use a multi-stage evaporation process to concentrate black liquor to reduce its volume and facilitate subsequent treatment. However, this process not only consumes a lot of energy, resulting in a large amount of additional carbon emissions, but also increases the operating costs of enterprises and reduces economic benefits. In addition, the conventional disposal methods (such as incineration and landfill) of solid wastes such as lignin residues after multi-stage evaporation treatment will also bring environmental problems. Incineration will produce harmful gases such as carbon dioxide and nitrogen oxides, exacerbating the greenhouse effect; while landfilling may pollute the soil and groundwater, release greenhouse gases such as methane, and pose long-term hazards to the regional environment.

[0005] The low-cost and rapid separation of organic matter mainly composed of lignin and dispersion liquid is an important part of the efficient treatment and resource conversion of black liquor, and has therefore been widely studied. For example, CN114364841B reports a process for extracting lignin from black liquor with acid adjustment as the core, including precipitating lignin by acidifying black liquor, adjusting the temperature to above 60°C, cooling and separation, displacement washing / ion exchange washing and other stages. Although this method can obtain lignin of higher purity, a large amount of wastewater is produced in the displacement washing / ion exchange washing stage, and the cost is relatively high. The document Waste and Biomass Valorization (2020) 11: 4731-4742 reports that a certain degree of lignin separation is achieved by a coagulation-flocculation method under acidic conditions of pH = 2.0 in polyethylene oxide, and the chemical oxygen demand is reduced by 75% and the turbidity is reduced by 95%. This method needs to be carried out under strong acidic conditions, corrodes pipelines, and produces acidic wastewater. In addition, there are also reports on the use of composite precipitants, but the operating temperature is room temperature, which is not suitable for the black liquor temperature directly offline (60-90°C).

[0006] From the above, it can be seen that black liquor treatment and resource conversion are key links in the green development of the papermaking industry. At present, it is still necessary to develop new theories and technologies that are more efficient, low-carbon, low-energy and low-cost to replace current processes, which can create economic benefits for enterprises and provide an important driving force for promoting technological change and industrial upgrading. Summary of the invention

[0007] In view of the problems existing in the prior art, the object of the present invention is to provide a method for treating papermaking pulping black liquor, comprising mixing papermaking pulping black liquor with a metal ion salt, wherein the valence state of the metal ions in the metal ion salt is divalent or above, performing a cation replacement reaction, causing lignin and hemicellulose to repolymerize and grow, obtaining a pretreatment liquid, and performing solid-liquid separation on the pretreatment liquid to obtain organic matter and a separation liquid, thereby completing the treatment. The present invention is based on the principle of cation replacement, and uses high-valent metal ions to replace the sodium ions in the stable clusters formed by electronegative lignin colloid particles and peripheral positive sodium ions in the black liquor, thereby achieving re-crosslinking, repolymerization, growth and separation of the lignin colloid particles, and thus achieving efficient, green and low-cost treatment of black liquor without the need for harsh acidic reaction environment conditions.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for treating papermaking pulping black liquor, the method comprising:

[0010] The papermaking pulping black liquor is mixed with a metal ion salt, wherein the valence state of the metal ions in the metal ion salt is divalent or above, and a cation replacement reaction is performed to cause the organic matter to repolymerize and grow to obtain a pretreatment liquid. The pretreatment liquid is subjected to solid-liquid separation to obtain organic matter and a separation liquid, thereby completing the treatment.

[0011] In black liquor, the main reason why the organic matter, such as lignin and hemicellulose, is difficult to separate from the aqueous liquid is that the electronegative organic colloid forms stable clusters with the peripheral positive sodium ions, and an electrostatic balance is established between each cluster. Therefore, breaking the cluster balance in the system is the key to achieving the re-aggregation of lignin colloids. The present invention is based on the principle of cation replacement, and adopts high-valent metal ions to replace the sodium ions in the cluster to achieve cross-linking and re-aggregation growth and separation of organic colloids, complete the growth of organic colloids (lignin colloids and hemicellulose colloids) into large particles, and then adopts low-cost rapid separation of organic matter and aqueous liquid that can be effectively achieved through solid-liquid separation. The treatment method is not harsh on the requirements of reaction environment conditions such as pH value, and can effectively avoid the adverse effects caused by the large-scale use of acidic substances. The treatment method is simple and convenient, does not require complicated replacement and washing procedures, effectively reduces wastewater production, and is suitable for large-scale industrial treatment.

[0012] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] As a preferred technical solution of the present invention, the papermaking pulping black liquor includes evaporated concentrated black liquor.

[0014] As a preferred technical solution of the present invention, in the papermaking pulping black liquor, the total mass proportion of the organic matter is 1% to 30%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28, 29% or 30%, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are equally applicable.

[0015] Preferably, the organic matter comprises lignin and hemicellulose.

[0016] As a preferred technical solution of the present invention, the metal ion in the metal ion salt includes any one of iron, cobalt, calcium, aluminum or magnesium.

[0017] As a preferred technical solution of the present invention, the anions in the metal ion salt include sulfate and / or nitrate.

[0018] Preferably, the metal ion salt includes any one of aluminum sulfate, calcium nitrate, iron nitrate, magnesium sulfate or cobalt nitrate.

[0019] In the present invention, the anions in the metal ion salts have an impact on the high-value conversion of separated organic matter and downstream processes such as wastewater treatment, especially chloride ions.

[0020] As a preferred technical solution of the present invention, the amount of the metal ion salt is 1-120 kg per ton of papermaking pulping black liquor, for example, 1 kg, 3 kg, 5 kg, 8 kg, 10 kg, 15 kg, 20 kg, 25 kg, 30 kg, 35 kg, 40 kg, 45 kg, 50 kg, 55 kg, 60 kg, 65 kg, 70 kg, 75 kg, 80 kg, 85 kg, 90 kg, 95 kg, 100 kg, 105 kg, 110 kg, 115 kg or 120 kg, etc., preferably 5-15 kg, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0021] In the treatment method of the present invention, the amount of the metal ion salt used is 1-120 kg per ton of papermaking pulping black liquor to produce treatment and separation effects. Considering the separation effect and separation cost, the best amount is 5-15 kg.

[0022] As a preferred technical solution of the present invention, the pH of the cation replacement reaction is 1 to 7, for example 1, 1.3, 1.5, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.3, 6.5, 6.8 or 7, etc., preferably 2 to 6, considering the separation effect and separation cost, further preferably 5 to 6, but not limited to the listed values, other values ​​not listed within the above numerical range are also applicable.

[0023] In the treatment method of the present invention, the pH of the liquid phase system after the metal ion salt and the papermaking pulping black liquor are mixed can achieve the treatment and separation effect when it is between 1 and 7. An acidic environment is preferred, that is, the preferred pH value is 2 to 6. When the cost of pH adjustment control is further considered, the pH value is 5 to 6.

[0024] As a preferred technical solution of the present invention, the pH of the cation replacement reaction is controlled by adding an auxiliary agent, and the auxiliary agent includes an acidic solution.

[0025] As a preferred technical solution of the present invention, the acidic solution includes hydrochloric acid with a mass percentage concentration of 5% to 36%, such as 5%, 10%, 15%, 20%, 25%, 30%, 32% or 36%, etc., sulfuric acid of 10% to 70%, such as 10%, 20%, 30%, 40%, 50%, 60% or 70%, etc., or nitric acid of 10% to 68%, such as at least one of 10%, 20%, 30%, 40%, 50%, 60% or 68%, etc.

[0026] Preferably, the auxiliary agent is first added to the papermaking pulping black liquor to adjust the pH, and then the metal ion salt is added and mixed.

[0027] As a preferred technical solution of the present invention, the temperature of the cation replacement reaction is 15 to 80°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc., preferably 40 to 60°C, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0028] As a preferred technical solution of the present invention, the temperature of the papermaking pulping black liquor produced by the upstream production line is controlled to be 40-60° C., and the papermaking pulping black liquor at 40-60° C. is mixed with the metal ion salt.

[0029] In the treatment method described in the present invention, the treatment and separation effects increase with increasing temperature, and no longer increase with temperature after reaching a certain value. The feature of the present invention is that the temperature of the black liquor produced by the upstream pulping at the outlet can be comprehensively considered, and the hot black liquor can be directly mixed with the metal ion salt without having to be carried out at room temperature.

[0030] As a preferred technical solution of the present invention, the time of the cation replacement reaction is 0.1 to 24 h, for example, 0.1 h, 0.5 h, 0.8 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h or 24 h, etc., preferably 1 to 10 h, more preferably 1.5 to 3 h, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0031] In the treatment method of the present invention, an obvious effect appears after 10 minutes, and the particles grow up with time. However, in the later stage, the re-aggregation growth is not obvious with the extension of time, and 1.5 to 3 hours is the best.

[0032] As a preferred technical solution of the present invention, the solid-liquid separation method includes filter pressing.

[0033] As a preferred technical solution of the present invention, the treatment method further comprises performing a thermal decomposition coupling upgrading treatment on the obtained separated organic matter to obtain a regenerated product.

[0034] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0035] The present invention is based on the principle of cation replacement, and adopts high-valent metal ions to replace sodium ions in clusters to realize cross-linking, repolymerization growth and separation of lignin colloid particles and hemicellulose colloid particles, and gradually grows into large particles. Subsequently, low-cost rapid separation of organic matter and aqueous liquid after polymerization growth can be effectively achieved through solid-liquid separation. The treatment method has no strict requirements on reaction environment conditions, and has mild pH, which can effectively avoid the adverse effects caused by the large-scale use of acidic substances. The treatment method has a simple and convenient operation process, does not require complicated replacement and washing processes, effectively reduces wastewater production, and is suitable for large-scale industrial treatment.

[0036] The present invention is applicable to the treatment of black liquor obtained from various pulping raw materials, and can achieve an organic matter separation efficiency of > 90%. By specifically matching the best high-valent metal ion salt and dosage for specific black liquor, optimizing the pH value, temperature and time conditions, an efficient separation of organic matter with an efficiency of 96% can be achieved.

[0037] The present invention produces high-value-added regeneration products by subjecting the obtained separated organic matter to thermochemical upgrading treatment, thereby effectively realizing recycling and avoiding the harm caused by incineration and landfill treatment of solid waste obtained after multi-stage evaporation treatment. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0039] It should be clear to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0040] Example 1

[0041] This embodiment provides a method for treating papermaking pulping black liquor, the method comprising:

[0042] (1) providing papermaking pulping black liquor, wherein the papermaking pulping black liquor is bamboo chip-based pulping black liquor, and contains organic matter (including lignin and hemicellulose) in an accumulated amount of about 5% by weight;

[0043] (2) providing a metal ion salt, wherein the metal ion salt is aluminum nitrate;

[0044] (3) The production temperature of papermaking pulping black liquor is maintained at 60° C., hydrochloric acid is added as an auxiliary agent to adjust the pH to 6, 10 g of the metal ion salt is added per kilogram of papermaking pulping black liquor, the two are directly mixed, and the timing of the cation replacement reaction is started to cause lignin and hemicellulose to repolymerize and grow. After 3 hours, a pretreated liquid is obtained, and the pretreated liquid is filtered to obtain organic matter and a separation liquid, thereby completing the treatment.

[0045] Example 2

[0046] This embodiment provides a method for treating papermaking pulping black liquor, the method comprising:

[0047] (1) providing papermaking pulping black liquor, wherein the papermaking pulping black liquor is wood chip and reed-based pulping black liquor, and contains organic matter (including lignin and hemicellulose) in an accumulated amount of about 4% by weight;

[0048] (2) providing a metal ion salt, wherein the metal ion salt is calcium nitrate;

[0049] (3) The production temperature of papermaking pulping black liquor is maintained at 50° C., sulfuric acid as an auxiliary agent is added to adjust the pH to 6, and the timing of the cation replacement reaction is started. 15 grams of the metal ion salt is added per kilogram of papermaking pulping black liquor and the two are mixed to allow lignin and hemicellulose to repolymerize and grow. After 20 hours, a pretreated liquid is obtained, and the pretreated liquid is filtered to obtain organic matter and a separation liquid, thereby completing the treatment.

[0050] Example 3

[0051] This embodiment provides a method for treating papermaking pulping black liquor. In step (2) of the treatment method, the metal ion salt is adjusted from aluminum nitrate to cobalt nitrate. Except for the above, other conditions are exactly the same as those in Example 1.

[0052] Example 4

[0053] This embodiment provides a method for treating papermaking pulping black liquor. In step (2) of the treatment method, the metal ion salt is adjusted from aluminum nitrate to magnesium nitrate. Except for the above, other conditions are exactly the same as those in Example 1.

[0054] Example 5

[0055] This embodiment provides a method for treating papermaking black liquor. In step (3) of the treatment method, the produced black liquor is cooled to a temperature of 15°C and maintained thereat before being mixed with a metal ion salt. Except for the above, other conditions are exactly the same as those in Example 1.

[0056] Example 6

[0057] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the produced black liquor is cooled to a temperature of 25°C and maintained thereat before being mixed with a metal ion salt. Except for the above, other conditions are exactly the same as those in Example 1.

[0058] Example 7

[0059] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the temperature of the produced black liquor is adjusted from 60°C to 40°C, and then directly mixed with the metal ion salt. Except for the above, other conditions are exactly the same as those in Example 1.

[0060] Example 8

[0061] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the temperature of the produced black liquor is adjusted from 60°C to 80°C, and then directly mixed with the metal ion salt. Except for the above, other conditions are exactly the same as those in Example 1.

[0062] Example 9

[0063] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the pH value is adjusted from 6 to 2. Except for the above, other conditions are exactly the same as those in Example 1.

[0064] Example 10

[0065] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the pH value for adjusting the pH is adjusted from 6 to 3. Except for the above, other conditions are exactly the same as those in Example 1.

[0066] Embodiment 11

[0067] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the pH value for adjusting the pH is adjusted from 6 to 5. Except for the above, other conditions are exactly the same as those in Example 1.

[0068] Example 12

[0069] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the pH value for adjusting the pH is adjusted from 6 to 7. Except for the above, other conditions are exactly the same as those in Example 1.

[0070] Embodiment 13

[0071] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the time of the cation replacement reaction is adjusted from 3 hours to 0.2 hours. Except for the above, other conditions are exactly the same as those in Example 1.

[0072] Embodiment 14

[0073] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the time of the cation replacement reaction is adjusted from 3 hours to 1.5 hours. Except for the above, other conditions are exactly the same as those in Example 1.

[0074] Embodiment 15

[0075] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the time of the cation replacement reaction is adjusted from 3 hours to 15 hours. Except for the above, other conditions are exactly the same as those in Example 1.

[0076] Example 16

[0077] This embodiment provides a method for treating papermaking pulping black liquor. In step (3) of the treatment method, the time of the cation replacement reaction is adjusted from 3 hours to 20 hours. Except for the above, other conditions are exactly the same as those in Example 1.

[0078] Control group 1

[0079] This control group provides a method for treating papermaking pulping black liquor. In step (2) of the treatment method, the metal ion salt is adjusted from aluminum sulfate to calcium chloride. Except for the above, other conditions are exactly the same as those in Example 1.

[0080] Control group 2

[0081] This control group provides a method for treating papermaking pulping black liquor. In step (2) of the treatment method, the metal ion salt is adjusted from aluminum sulfate to ferric chloride. Except for the above, other conditions are exactly the same as those in Example 1.

[0082] Comparative Example 1

[0083] This embodiment provides a method for treating papermaking pulping black liquor. In step (2) of the treatment method, the metal ion salt is adjusted from aluminum sulfate to sodium chloride. Except for the above, other conditions are exactly the same as those in Example 1.

[0084] The separation efficiency of the organic matter obtained in the embodiment, the control group and the comparative example was calculated as follows: separation efficiency = (mass of the obtained organic matter after drying - total amount of metal salt used) / (mass of the obtained organic matter after drying + mass of the separated liquid after evaporation and drying - total amount of metal salt used) * 100%. The chromaticity of the filtrate is the dilution multiple when the separated liquid is diluted with distilled water and compared with the reference water sample until the color difference is consistent.

[0085] Table 1

[0086] Group Organic matter separation efficiency (%) Filtrate chromaticity (times) Example 1 94％ 383 Example 2 90％ 564 Example 3 83％ 1985 Example 4 81％ 2316 Example 5 87％ 1584 Example 6 90％ 581 Example 7 95％ 343 Example 8 95％ 364 Example 9 96％ 310 Example 10 96％ 291 Embodiment 11 92％ 479 Example 12 85％ 2130 Embodiment 13 89％ 1320 Embodiment 14 92％ 488 Embodiment 15 95％ 343 Example 16 95％ 331 Control group 1 91％ 591 Control group 2 89％ 1271 Comparative Example 1 45％ 8531

[0087] It can be seen from Table 1 that a single metal salt can be used to achieve efficient separation of organic matter; within the test range, the higher the temperature of the repolymerization growth, the lower the pH, and the longer the time, the better the separation effect.

[0088] Then, the organic matter obtained in Example 1 and Example 2, Control Group 1 and Control Group 2 and Comparative Example 1 was subjected to thermal decomposition coupling upgrading treatment, and the hydrogen chloride in the flue gas of Example 1 and 2 was less than 50 mg / Nm 3 , while the hydrogen chloride in the flue gas of the control groups 1, 2 and comparative example 1 using chlorine-containing compounds reached 900 mg / Nm 3 High concentration of hydrogen chloride will corrode the pipeline, which is not conducive to practical application.

[0089] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0091] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for treating papermaking pulping black liquor, characterized in that: The processing method comprises: The papermaking pulping black liquor is mixed with a metal ion salt, wherein the valence state of the metal ions in the metal ion salt is divalent or above, and a cation replacement reaction is performed to cause the organic matter to repolymerize and grow to obtain a pretreatment liquid. The pretreatment liquid is subjected to solid-liquid separation to obtain organic matter and a separation liquid, thereby completing the treatment.

2. The method for treating papermaking pulping black liquor according to claim 1, characterized in that: In the papermaking pulping black liquor, the total mass proportion of the organic matter is 1% to 30%; Preferably, the organic matter comprises lignin and hemicellulose.

3. The method for treating papermaking pulping black liquor according to claim 1 or 2, characterized in that: The metal ion in the metal ion salt includes any one of iron, cobalt, calcium, aluminum or magnesium; Preferably, the anions in the metal ion salt include sulfate and / or nitrate; Preferably, the metal ion salt includes any one of aluminum sulfate, calcium nitrate, iron nitrate, magnesium sulfate or cobalt nitrate.

4. The method for treating papermaking pulping black liquor according to any one of claims 1 to 3, characterized in that: The amount of the metal ion salt used is 1-120 kg per ton of papermaking pulping black liquor, preferably 5-15 kg.

5. The method for treating papermaking pulping black liquor according to any one of claims 1 to 4, characterized in that: The pH of the cation replacement reaction is 1-7, preferably 2-6, and more preferably 5-6.

6. The method for treating papermaking pulping black liquor according to claim 5, characterized in that: The pH of the cation replacement reaction is controlled by adding an auxiliary agent, wherein the auxiliary agent includes an acidic solution; Preferably, the acidic solution comprises at least one of hydrochloric acid with a mass percentage concentration of 5% to 36%, sulfuric acid with a mass percentage concentration of 10% to 70%, or nitric acid with a mass percentage concentration of 10% to 68%. Preferably, the auxiliary agent is first added to the papermaking pulping black liquor to adjust the pH, and then the metal ion salt is added and mixed.

7. The method for treating papermaking pulping black liquor according to any one of claims 1 to 6, characterized in that: The temperature of the cation replacement reaction is 15 to 80°C, preferably 40 to 60°C; Preferably, the temperature of the papermaking pulping black liquor produced by the upstream production line is controlled to be 40-60° C., and the papermaking pulping black liquor at 40-60° C. is mixed with the metal ion salt.

8. The method for treating papermaking pulping black liquor according to any one of claims 1 to 7, characterized in that: The time of the cation replacement reaction is 0.1 to 24 hours, preferably 1 to 10 hours, and more preferably 1.5 to 3 hours.

9. The method for treating papermaking pulping black liquor according to any one of claims 1 to 8, characterized in that: The solid-liquid separation method includes filter pressing.

10. The method for treating papermaking pulping black liquor according to any one of claims 1 to 9, characterized in that: The treatment method further comprises performing thermal decomposition coupling upgrading treatment on the obtained separated organic matter to obtain a regenerated product.