A method of treatment with a carbonate-containing alkaline wash

Abstract

The application relates to the technical field of waste recycling, in particular to a treatment method of carbonate-containing alkaline washing liquor. The treatment method comprises the following steps: performing double hydrolysis reaction on the carbonate-containing alkaline washing liquor and an aluminum-containing acidic solution to obtain a hydrolysis slurry; wherein, in the case of the same cations, the solubility of the formed salt in the double hydrolysis reaction is greater than the solubility of the carbonate in the carbonate-containing alkaline washing liquor; performing solid-liquid separation on the hydrolysis slurry to obtain a sodium-containing solution; and performing membrane separation on the sodium-containing solution to obtain soft water. The treatment method reduces the content of salt (especially carbonate) in the alkaline washing liquor through the combination of chemical reaction and physical separation, finally outputs soft water with an electric conductivity of 10 muS / cm to 50 muS / cm, and the reused soft water accounts for 65% to 85% of the total volume of the soft water.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste recycling, and particularly relates to a treatment method of carbonate-containing alkaline washing solution. BACKGROUND

[0002] In the industries of alumina production and textile printing and dyeing, the carbonate-containing alkaline washing solution has strong pH value buffering property, and generally uses strong acid (for example, sulfuric acid) to directly neutralize. However, this method has defects. Taking the production of pseudoboehmite by carbonization method in alumina production as an example, a large amount of pseudoboehmite washing solution is generated in the production process and needs to be reduced in solid phase concentration by membrane treatment. However, the pseudoboehmite product has excellent peptization property, and the nano colloidal particles easily cause the microfiltration membrane and nanofiltration membrane to be blocked. The nano colloidal particles easily block the microfiltration membrane and nanofiltration membrane in the membrane treatment system. Therefore, before the membrane treatment, the pH value of the alkaline washing solution needs to be regulated so that the pH value of the alkaline washing solution is close to the isoelectric point of the pseudoboehmite, so as to reduce the electrostatic force between the nano colloidal particles, so as to promote the nano colloidal particles to be aggregated into micron particles that can be separated. However, due to the existence of the acid-base buffer system in the alkaline washing solution, a large amount of acid needs to be added to reduce the pH value of the alkaline washing solution when the pH value of the alkaline washing solution is regulated.

[0003] However, a large amount of acid not only easily corrodes the equipment, but also forms a large amount of salt with the alkaline solution. The salt directly enters the membrane treatment system, which causes the microfiltration membrane and nanofiltration membrane to be scaled and shortens the service life. The microfiltration membrane and nanofiltration membrane are scaled, which significantly reduces the service life of the membranes. SUMMARY

[0004] The present application provides a treatment method of carbonate-containing alkaline washing solution to solve the technical problem of how to reduce the content of salt in the alkaline washing solution.

[0005] In a first aspect, the present application provides a treatment method of carbonate-containing alkaline washing solution, which comprises:

[0006] The carbonate-containing alkaline washing solution and the aluminum-containing acidic solution are subjected to double hydrolysis reaction, so that the carbonate in the carbonate-containing alkaline washing solution is consumed by aluminum ions under the action of the sodium oxide component, and a hydrolysis slurry is obtained; wherein, in the case of the same cation, the solubility of the combined salt formed by the aluminum-containing acidic solution in the double hydrolysis reaction is greater than the solubility of the carbonate in the carbonate-containing alkaline washing solution;

[0007] The hydrolysis slurry is subjected to solid-liquid separation to obtain a sodium-containing solution;

[0008] The sodium-containing solution is subjected to membrane separation to obtain soft water.

[0009] Optionally, the amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline washing solution satisfy: n1:n2=(0.5 to 1.5):(2 to 4).

[0010] Optionally, the volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy: V1:V2=1:(15 to 30).

[0011] Optionally, the solid-phase concentration of the aluminum-containing acidic solution is 50 g / L to 110 g / L, calculated based on aluminum oxide as the solid-phase substance.

[0012] Optionally, the solid-phase concentration of the carbonate-containing alkaline washing solution is 7 g / L to 9 g / L, calculated based on sodium oxide as the solid-phase substance.

[0013] Optionally, the temperature of the double hydrolysis reaction is 25°C to 90°C.

[0014] Optionally, the pH value of the hydrolysis slurry is 6.0 to 8.0.

[0015] Optionally, the aluminum-containing acidic solution is at least one of an aluminum sulfate solution, an aluminum nitrate solution, or an aluminum chloride solution.

[0016] Optionally, the step of subjecting the hydrolysis slurry to solid-liquid separation to obtain a sodium-containing solution comprises:

[0017] subjecting the hydrolysis slurry to solid-liquid separation to obtain a sodium-containing solution and an aluminum hydroxide precipitate;

[0018] subjecting the aluminum hydroxide precipitate to purification treatment to obtain pseudoboehmite.

[0019] Optionally, the conductivity of the sodium-containing solution is 10,000 μS / cm to 15,000 μS / cm.

[0020] The conductivity of the soft water is 10 μS / cm to 50 μS / cm.

[0021] The processing method of the carbonate-containing alkaline washing solution provided by the embodiment of the present application is particularly suitable for carbonate-containing alkaline washing solution. Through the alkaline environment of the carbonate-containing alkaline washing solution itself, the bicarbonate ions in the washing solution can react with aluminum ions in the aluminum-containing acidic solution to generate double hydrolysis. In this process, aluminum ions are hydrolyzed to generate aluminum hydroxide precipitate and release hydrogen ions, and these hydrogen ions further promote the reaction of bicarbonate ions to generate carbon dioxide gas, thereby effectively regulating and reducing the concentration of carbonate in the washing solution. In addition, it is worth noting that under the condition of the same cation, the combined salt formed by the double hydrolysis reaction of the aluminum-containing acidic solution has higher solubility than the carbonate in the carbonate-containing alkaline washing solution. Therefore, after the double hydrolysis reaction is completed, these combined salts can further reduce the solubility of carbonate in a competitive manner, thereby enhancing the overall effect of the double hydrolysis reaction, thereby effectively reducing the salt content of the carbonate-containing alkaline solution, and avoiding the blockage of the membrane pore channel in the subsequent membrane separation stage. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate preferred embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0024] Figure 1 The processing method of the carbonate-containing alkaline washing solution provided by the embodiment of the present application is a processing method of the carbonate-containing alkaline washing solution.

[0025] Figure 2 The processing method of the carbonate-containing alkaline washing solution provided by the embodiment of the present application is a processing method of the carbonate-containing alkaline washing solution. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] The range descriptions described in the present application, such as numerical range, ratio range, etc., include all possible sub-ranges and single values within the range, for example, the range description of "1 to 6" or "1~6" covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "comprising" and the like used herein mean "including but not limited to"; the terms "first", "second" and the like are used only to distinguish different entities or operations, and do not imply actual order or relationship; the expressions "at least one", "multiple", "at least one kind" and the like refer to any combination of the corresponding objects, including single or multiple combinations of the objects. The proportional relationships involved in the present application, such as mass ratio, molar ratio, etc., should be understood as the corresponding relationship between the front and rear terms of the proportion in the order described. The raw materials, reagents, instruments and equipment used in the present application can be purchased or prepared by existing methods.

[0028] It should be noted that the carbonate-containing alkaline washing solution is generally produced in the later stage of the aging stage of the carbonation neutralization process, and the pH value is generally stable at more than 11, which makes the acidification process of the alkaline washing solution generally need to go through the consumption of two buffer pairs, which are the conjugate acid-base pairs: CO3 2- / HCO3 - (pH about 10.33) and HCO3 - / H2CO3 (pH about 6.35). In the acidification stage, the two buffer pairs will react as follows:

[0029] CO3 2- +H + →HCO 3;

[0030] HCO3 - +H + →H2CO3→CO2+H2O, so neutralizing the two buffer pairs needs to consume a large amount of acid solution, however, the addition of a large amount of acid solution not only will cause corrosion of the equipment, but also will introduce additional salt after the reaction, which will aggravate the load of the subsequent membrane treatment stage; at the same time, the wastewater containing these salts directly into the membrane system will cause fouling of the membrane system, thereby significantly reducing the service life of the membrane.

[0031] Therefore, in the treatment process of these alkaline washing solutions, the core technical problem is how to break through the buffer effect of the buffer pairs under the premise of avoiding the use of strong acid and realize multi-target collaborative treatment. Specifically, (1) traditional strong acid neutralization needs to add excess acid to break through CO3 2- / HCO3 - and HCO3 -(1) The double buffering of H2CO3 will cause device corrosion and salt accumulation problems, so it is necessary to efficiently break the carbonate buffer system; (2) The pseudo-boehmite nano colloidal particles with a particle size of less than 100 nm in the washing solution have a high Zeta potential and have a colloid stability problem, which is easy to block the subsequent membrane system, so it is necessary to overcome the difficulty of stable dispersion of nano colloids; (3) Under the premise of the membrane treatment of the Na + Under the premise of the membrane treatment of the Na

[0032] Based on the above problems, the embodiment of the present application provides the following technical solutions:

[0033] Figure 1 An exemplary process flow diagram of a treatment method of a carbonate-containing alkaline washing solution provided by the embodiment of the present application is shown;

[0034] As Figure 1 shown, the embodiment of the present application provides a treatment method of a carbonate-containing alkaline washing solution, which comprises:

[0035] S1. Double hydrolysis reaction of the carbonate-containing alkaline washing solution and the aluminum-containing acidic solution to obtain a hydrolysis slurry; wherein, in the case of the same cations, the solubility of the formed salt in the double hydrolysis reaction of the aluminum-containing acidic solution is greater than the solubility of the carbonate in the carbonate-containing alkaline washing solution;

[0036] S2. Solid-liquid separation of the hydrolysis slurry to obtain a sodium-containing solution;

[0037] S3. Membrane separation of the sodium-containing solution to obtain soft water.

[0038] It should be noted that the membrane separation can be processed by using an ultrafiltration reverse osmosis membrane system.

[0039] It should be noted that the treatment method of the carbonate-containing alkaline washing solution provided by the embodiment of the present application reduces the content of salt (especially carbonate) in the alkaline washing solution by chemical reaction combined with physical separation, and finally outputs soft water. The core mechanism is as follows:

[0040] 1. Double hydrolysis reaction: chemical conversion and consumption of carbonate (mainly salt reduction step)

[0041] (1) Reaction core: mixing the carbonate-containing (mainly sodium carbonate Na2CO3) alkaline washing solution with the aluminum-containing acidic solution {such as aluminum sulfate Al2(SO4)3, aluminum nitrate Al(NO3)3, etc.}.

[0042] (2) Role of Aluminum ions: In alkaline conditions (provided by the sodium oxide Na2O component in the wash solution), aluminum ions Al 3 + will strongly hydrolyze to form Al(OH)3 aluminum hydroxide precipitate.

[0043] (3) Key to carbonate consumption: the hydrolysis of aluminum ions Al 3+ will release H + ions. These H + ions will react with carbonate ions CO3 2- in the alkaline wash solution:

[0044] CO3 2- + H + → HCO3 -;

[0045] HCO3 - + H + → H2CO3 → H2O + CO2↑,

[0046] Result: Carbonate (CO3 2- ) is consumed by the H + ions produced by the hydrolysis of aluminum ions and converted into carbon dioxide gas (CO2) that escapes the system. At the same time, aluminum ions form insoluble Al(OH)3 aluminum hydroxide precipitate.

[0047] (4) Salt reduction effect: This double hydrolysis reaction, through chemical reactions, converts high concentration of sodium carbonate salt dissolved in water into gas (CO2) and insoluble solid Al(OH)3, thus significantly reducing the total amount of salt in the solution in the form of carbonate.

[0048] 2. Solid-liquid separation: removal of insoluble solids (physical salt reduction)

[0049] Operation: Perform solid-liquid separation (e.g. filtration, sedimentation centrifugation) on the "hydrolysis slurry" obtained after the double hydrolysis reaction {containing the generated Al(OH)3 aluminum hydroxide precipitate, possibly other insoluble substances, and a solution containing dissolved sodium salt}.

[0050] Result: After separation, solid residue {mainly Al(OH)3} and sodium-containing solution are obtained.

[0051] Salt reduction effect: This solid-liquid separation step removes the insoluble solid material Al(OH)3 generated in the double hydrolysis reaction, which itself also carries ions (e.g. OH - and adsorbed Na + , etc.) out of the solution, further reducing the total dissolved solids in the final solution. More importantly, it prepares a relatively clear solution for subsequent membrane separation.

[0052] 3. Membrane separation: Deep desalination (Physical desalination)

[0053] Operation: The sodium-containing solution obtained by solid-liquid separation is subjected to membrane separation treatment (usually reverse osmosis RO or nanofiltration NF).

[0054] Effect of membrane separation: Reverse osmosis membranes have very dense pore sizes, allowing only water molecules to pass through, while most dissolved salt ions (e.g., Na + , and other anions remaining in the solution, such as SO4 2- , NO3 - , Cl - , etc.) are retained on the concentrated water side.

[0055] Result: After membrane separation, two streams are produced: soft water (product water) - purified water with very low salt (total dissolved solids TDS) content; concentrated water - wastewater containing high concentrations of salt.

[0056] Desalination effect: This is the final deep desalination step. It efficiently removes the remaining dissolved salts (mainly Na + ions remaining after the first reaction and anions introduced by the aluminum-containing acidic solution) in the sodium-containing solution through physical membrane separation, thereby obtaining soft water that meets the requirements.

[0057] Therefore, the processing method of the carbonate-containing alkaline cleaning solution provided in the embodiments of the present application has the following main mechanisms:

[0058] (1) Chemical conversion consumption (core): Utilize the double hydrolysis reaction of aluminum ions under alkaline conditions to consume carbonate ions (CO3 2- ) in the alkaline cleaning solution, converting them into gas CO2 (escaping the system) and insoluble solid Al(OH)3 (subsequently separated). This processing step directly and significantly eliminates the main source of salt (sodium carbonate) in the original cleaning solution.

[0059] (2) Physical removal of solids: Through solid-liquid separation, remove the insoluble Al(OH)3 aluminum hydroxide precipitate produced by the double hydrolysis reaction and the ions it carries, further reducing the total amount of dissolved solids.

[0060] (3) Physical deep desalination: Perform membrane separation (reverse osmosis / nanofiltration) on the remaining sodium-containing solution, utilizing the physical screening effect of the membrane to efficiently remove the remaining dissolved sodium salts and other ions in the solution, ultimately producing soft water with very low salt content.

[0061] (4) Key design point (anion selection):

[0062] The limitation that the solubility of the sodium salt formed by the anion of the aluminum-containing acidic solution is greater than the solubility of sodium carbonate is very important. This ensures that:

[0063] In the double hydrolysis reaction process, the anions introduced by the aluminum-containing acidic solution (e.g., SO4 2- , NO3 - ) form sodium salts (Na2SO4, NaNO3) with high solubility. These newly formed sodium salts do not form new aluminum hydroxide precipitates in the reaction system or subsequent sodium-containing solution (otherwise it will interfere with the reaction or block the membrane).

[0064] In addition, these highly soluble sodium salts can be smoothly left in the solution and finally effectively removed by the membrane separation step, thereby ensuring the low salt quality of the soft water.

[0065] In summary, the treatment method of the carbonate-containing alkaline washing solution provided in the embodiments of the present application combines chemical reaction (conversion and consumption of main salts) and physical separation (removal of solids and deep desalination) two means, which efficiently reduces the salt content in the alkaline washing solution, and finally obtains soft water.

[0066] In some optional embodiments, the amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline washing solution satisfy: n1:n2=(0.5 to 1.5):(2 to 4).

[0067] In these embodiments, the amount of substance ratio (0.5 to 1.5):(2 to 4) of aluminum ions in the aluminum-containing acidic solution and carbonate ions in the carbonate-containing alkaline washing solution can promote the double hydrolysis reaction to proceed sufficiently, ensuring that aluminum ions can fully consume carbonate ions, thereby effectively reducing the carbonate component of the carbonate-containing alkaline washing solution.

[0068] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5.

[0069] The amount of substance n2 of carbonate ions in the carbonate-containing alkaline washing solution can be 2, 2.5, 3, 3.5, or 4.

[0070] In some optional embodiments, the volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy: V1:V2=1:(15 to 30).

[0071] In these embodiments, the volume ratio of 1:(15 to 30) of the aluminum-containing acidic solution and the carbonate-containing alkaline washing solution can promote the double hydrolysis reaction between aluminum ions in the aluminum-containing acidic solution and carbonate ions in the carbonate-containing alkaline washing solution to proceed sufficiently, and the carbonate component of the carbonate-containing alkaline washing solution can be effectively reduced by the consumption of aluminum ions.

[0072] The volume V2 of the carbonate-containing alkaline washing solution can be 15, 16, 17, 18, 19, 20, 25, or 30.

[0073] It should be noted that in the case where the volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy V1:V2<1:35, the aluminum ions in the aluminum-containing acidic solution are relatively low, which is insufficient to completely consume the carbonate ions in the carbonate-containing alkaline washing solution, and at the same time, a large amount of HCO3 - / CO3 2- buffering system, which makes it necessary to add an additional acidic reagent to adjust the pH value of the hydrolysis slurry before membrane separation, not only increasing the overall processing cost, but also increasing the salt processing load of membrane separation; in the case where the volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy V1:V2>1:15, the aluminum-containing acidic solution is added in excess, and excessive aluminum ions can cause the end point pH value of the double hydrolysis reaction to be less than 6, which can break the stable state of the aluminum hydroxide precipitate in the hydrolysis slurry, causing the redissolution of the aluminum hydroxide precipitate, and thus affecting the subsequent solid-liquid separation and membrane separation processing effect.

[0074] In some optional embodiments, the solid-phase concentration of the aluminum-containing acidic solution is 50 g / L to 110 g / L, based on the solid phase of aluminum oxide.

[0075] The solid-phase concentration refers to the mass fraction of the remaining solid part in the total amount of the system after the liquid or suspended system is dried under specified conditions.

[0076] In these embodiments, the aluminum-containing acidic solution with a solid-phase concentration of 50 g / L to 110 g / L can make the aluminum-containing acidic solution have sufficient aluminum ions, and these aluminum ions can be uniformly dispersed in the aluminum-containing acidic solution, which is beneficial to the double hydrolysis reaction.

[0077] The solid-phase concentration of the aluminum-containing acidic solution can be 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, or 110 g / L.

[0078] It should be noted that in the case that the solid phase concentration of the aluminum-containing acidic solution is less than 50 g / L, the solid phase concentration of the aluminum-containing acidic solution is low, in order to ensure the amount of aluminum ions, the volume of the aluminum-containing acidic solution needs to be increased, which leads to the dilution of the overall double hydrolysis reaction system, so that the pH value of the final hydrolysis slurry deviates from the range of 6 to 8, causing the re-dissolution of aluminum hydroxide precipitation or colloid in the hydrolysis slurry, affecting the subsequent solid-liquid separation and membrane separation treatment effect; in the case that the solid phase concentration of the aluminum-containing acidic solution is greater than 110 g / L, the viscosity of the aluminum-containing acidic solution is too large, the mixing process of the double hydrolysis reaction is uneven, the risk of local reaction is increased, and flocculent aluminum hydroxide can be formed in the hydrolysis slurry, which can wrap unreacted particles, thereby reducing the efficiency of the double hydrolysis reaction.

[0079] It should be noted that the effective component in the aluminum-containing acidic solution is aluminum oxide hydrate, such as aluminum hydroxide.

[0080] In some optional embodiments, the solid phase concentration of the carbonate-containing alkaline washing solution is 7 g / L to 9 g / L, calculated based on sodium oxide as the solid phase.

[0081] In these embodiments, the carbonate-containing alkaline washing solution with a solid phase concentration of 7 g / L to 9 g / L has sufficient alkaline substances and carbonate ions, which is beneficial to the progress of the double hydrolysis reaction and the consumption of carbonate ions in the carbonate-containing alkaline washing solution, thereby effectively reducing the carbonate component in the carbonate-containing alkaline washing solution.

[0082] The solid phase concentration of the carbonate-containing alkaline washing solution can be 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, or 9.0 g / L.

[0083] It should be noted that in the case that the solid phase concentration of the carbonate-containing alkaline washing solution is less than 7 g / L, the alkaline substance content of the carbonate-containing alkaline washing solution is insufficient, which makes it difficult to promote the progress of the double hydrolysis reaction, and the double hydrolysis reaction time needs to be prolonged or the double hydrolysis reaction temperature needs to be increased, which will increase the energy consumption of the double hydrolysis reaction; in the case that the solid phase concentration of the carbonate-containing alkaline washing solution is greater than 9.0 g / L, the concentration of carbonate ions in the carbonate-containing alkaline washing solution is too high, and the addition amount of the aluminum-containing acidic solution needs to be increased, otherwise the concentration of residual sodium salt in the hydrolysis slurry will be too high, which will increase the risk of fouling in the subsequent membrane separation stage.

[0084] In some optional embodiments, the temperature of the double hydrolysis reaction is 25°C to 90°C.

[0085] In these embodiments, the double hydrolysis reaction at a temperature of 25°C to 90°C can facilitate sufficient reaction between carbonate ions in the carbonate-containing alkaline solution and aluminum ions in the aluminum-containing acidic solution to generate a large amount of aluminum hydroxide precipitation product, sodium salt, and carbon dioxide gas; at the same time, the double hydrolysis reaction at a temperature of 25°C to 90°C can facilitate the escape of carbon dioxide gas from the hydrolysis slurry, without causing the re-dispersion or crystal form transformation of the aluminum hydroxide, so that the aluminum hydroxide precipitation can still grow and settle normally.

[0086] The temperature of the double hydrolysis reaction can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C.

[0087] It should be noted that, when the temperature of the double hydrolysis reaction is less than 25°C, this makes the double hydrolysis reaction slow and affects the growth of the aluminum hydroxide crystal nucleus in the double hydrolysis reaction, so that the aluminum hydroxide crystal nucleus forms aluminum hydroxide colloid, which can block the membrane pores in the subsequent membrane separation process, thereby affecting the service life of the membrane used in the membrane separation process; when the temperature of the double hydrolysis reaction is greater than 70°C, this makes the carbon dioxide generated by the double hydrolysis reaction escape from the hydrolysis slurry to form bubbles, which can interfere with the morphology of the aluminum hydroxide precipitation and form flocculent aluminum hydroxide, which can cause the moisture content of the filter cake obtained in the subsequent solid-liquid separation stage to be too high, resulting in soft water loss; in addition, the temperature of the double hydrolysis reaction can increase the energy consumption of the double hydrolysis reaction.

[0088] In some optional embodiments, the pH value of the hydrolysis slurry is 6.0 to 8.0.

[0089] In these embodiments, the hydrolysis slurry with a pH value of 6.0 to 8.0 indicates that the aluminum ions in the aluminum-containing acidic solution and the carbonate ions in the carbonate-containing alkaline solution can react sufficiently, which makes the hydrolysis slurry slightly neutral, and can avoid the re-dissolution of the aluminum hydroxide precipitation and affect the treatment effect in the subsequent membrane separation stage.

[0090] The pH value of the hydrolysis slurry can be 6.0, 6.5, 7.0, 7.5, or 8.0.

[0091] In some optional embodiments, the aluminum-containing acidic solution is at least one of an aluminum sulfate solution, an aluminum nitrate solution, and an aluminum chloride solution.

[0092] In these embodiments, the aluminum-containing acidic solution including at least one of an aluminum sulfate solution, an aluminum nitrate solution, and an aluminum chloride solution has high water solubility, and can quickly release sufficient aluminum ions to participate in the double hydrolysis reaction and effectively consume carbonate ions in the carbonate-containing alkaline solution; in addition, the anions (SO4 2- , NO3- Cl - Sodium salts formed by sodium ions have higher solubility than sodium carbonate. These sodium salts can prevent crystallization during the membrane treatment stage, which would clog the pores of the membrane. They can also reduce the content of other impurity salts, ensuring stable operation in the subsequent membrane separation stage.

[0093] Figure 2 A detailed flowchart illustrating a treatment method for a carbonate-containing alkaline washing solution provided in an embodiment of this application is shown by way of example.

[0094] In some alternative implementations, such as Figure 2 As shown, the step of performing solid-liquid separation on the hydrolyzed slurry to obtain a sodium-containing solution includes:

[0095] S201. The hydrolyzed slurry is subjected to solid-liquid separation to obtain a sodium-containing solution and aluminum hydroxide precipitate;

[0096] S202. The aluminum hydroxide precipitate is purified to obtain boehmite.

[0097] In these embodiments, aluminum hydroxide precipitate and sodium-containing solution in the hydrolyzed slurry can be effectively separated by solid-liquid separation. Then, the aluminum hydroxide precipitate can be purified by purification treatment to obtain a relatively pure aluminum hydroxide product.

[0098] In some alternative embodiments, the conductivity of the sodium-containing solution is from 10,000 μS / cm to 15,000 μS / cm;

[0099] The conductivity of the soft water is from 10 μS / cm to 50 μS / cm.

[0100] In these embodiments, a sodium-containing solution with a conductivity of 10,000 μS / cm to 15,000 μS / cm indicates that the sodium-containing solution contains a certain amount of salt components, which is beneficial for the subsequent separation of these oxygen components by membrane separation; in addition, soft water with a conductivity of 10 μS / cm to 50 μS / cm indicates that its salt content is low and can meet the standards for reuse.

[0101] The conductivity of the sodium-containing solution can be 10000 μS / cm, 11000 μS / cm, 12000 μS / cm, 13000 μS / cm, 14000 μS / cm or 15000 μS / cm.

[0102] The conductivity of the soft water can be 10 μS / cm, 20 μS / cm, 30 μS / cm, 40 μS / cm, or 50 μS / cm.

[0103] Based on a general inventive concept, the application provides an application of a treatment method of a carbonate-containing alkaline wash liquor, and the treatment method is used in a soft water recovery system of the carbonate-containing alkaline wash liquor.

[0104] The application is implemented based on the above treatment method, and the specific steps of the treatment method can refer to the above embodiments. Since the application adopts part or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0105] The application will be further described below in combination with specific embodiments. The experimental methods not specified in the following embodiments are generally determined according to national standards / industry standards; if there is no corresponding national standard / industry standard, the general international standard, the conventional condition or the condition suggested by the manufacturer is used.

[0106] Embodiment 1

[0107] As shown in the above embodiments, a treatment method of a carbonate-containing alkaline wash liquor comprises: Figure 2

[0108] S1. performing a double hydrolysis reaction on the carbonate-containing alkaline wash liquor and an aluminum-containing acidic solution to obtain a hydrolysis slurry; wherein in the case of the same cations, the solubility of the combined salt formed by the aluminum-containing acidic solution in the double hydrolysis reaction is greater than the solubility of the carbonate.

[0109] S201. performing a solid-liquid separation on the hydrolysis slurry to obtain a sodium-containing solution and an aluminum hydroxide precipitate;

[0110] S202. performing a purification treatment on the aluminum hydroxide precipitate to obtain a pseudo-boehmite;

[0111] S3. performing a membrane separation on the sodium-containing solution to obtain soft water.

[0112] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline wash liquor satisfy: n1:n2=0.5:2.

[0113] The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline wash liquor satisfy: V1:V2=1:20.

[0114] The solid phase concentration of the aluminum-containing acidic solution is 105 g / L in terms of aluminum oxide as the solid phase; the temperature of the aluminum-containing acidic solution is 25°C.

[0115] The solid phase concentration of the carbonate-containing alkaline wash liquor is 8 g / L in terms of sodium oxide as the solid phase; the pH value of the carbonate-containing alkaline wash liquor is 11.2, and the temperature of the carbonate-containing alkaline wash liquor is 70°C.

[0116] ​The temperature of the double hydrolysis reaction is 90℃.

[0117] The pH value of the hydrolysis slurry is 7.8.

[0118] The kind of the aluminum-containing acidic solution is aluminum sulfate solution.

[0119] Example 2

[0120] Compared with Example 1, the differences of Example 2 are as follows, and the rest are the same:

[0121] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline washing solution satisfy: n1:n2=0.75:2.5.

[0122] The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy: V1:V2=1:15.

[0123] The solid phase concentration of the aluminum-containing acidic solution is 50g / L, calculated based on aluminum oxide as the solid phase; the temperature of the aluminum-containing acidic solution is 25℃.

[0124] The solid phase concentration of the carbonate-containing alkaline washing solution is 7g / L, calculated based on sodium oxide as the solid phase; the pH value of the carbonate-containing alkaline washing solution is 11.0; the temperature of the carbonate-containing alkaline washing solution is 25℃.

[0125] The temperature of the double hydrolysis reaction is 25℃.

[0126] The pH value of the hydrolysis slurry is 6.0.

[0127] The kind of the aluminum-containing acidic solution is aluminum chloride solution.

[0128] Example 3

[0129] Compared with Example 1, the differences of Example 3 are as follows, and the rest are the same:

[0130] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline washing solution satisfy: n1:n2=1:3.

[0131] The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy: V1:V2=1:30.

[0132] The solid phase concentration of the aluminum-containing acidic solution is 110g / L, calculated based on aluminum oxide as the solid phase; the temperature of the aluminum-containing acidic solution is 70℃.

[0133] The solid phase concentration of the carbonate-containing alkaline washing solution is 9g / L, calculated based on sodium oxide as the solid phase; the pH value of the carbonate-containing alkaline washing solution is 11.5; the temperature of the carbonate-containing alkaline washing solution is 70℃.

[0134] The temperature of the double hydrolysis reaction is 25-90°C.

[0135] The pH value of the hydrolysis slurry is 8.0.

[0136] The type of the aluminum-containing acidic solution is an aluminum nitrate solution.

[0137] Example 4

[0138] Compared with Example 1, the differences of Example 4 are as follows, and the rest are the same:

[0139] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline washing solution satisfy: n1:n2 = 1.25:3.5.

[0140] The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy: V1:V2 = 1:25.

[0141] The solid-phase concentration of the aluminum-containing acidic solution is 80 g / L, calculated based on aluminum oxide as the solid-phase substance; the temperature of the aluminum-containing acidic solution is 50°C.

[0142] The solid-phase concentration of the carbonate-containing alkaline washing solution is 8 g / L, calculated based on sodium oxide as the solid-phase substance; the pH value of the carbonate-containing alkaline washing solution is 11.3; and the temperature of the carbonate-containing alkaline washing solution is 50°C.

[0143] The temperature of the double hydrolysis reaction is 50°C.

[0144] The pH value of the hydrolysis slurry is 7.0.

[0145] The type of the aluminum-containing acidic solution is an aluminum sulfate solution.

[0146] Example 5

[0147] Compared with Example 1, the differences of Example 5 are as follows, and the rest are the same:

[0148] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline washing solution satisfy: n1:n2 = 1.5:4.

[0149] The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy: V1:V2 = 1:20.

[0150] The solid-phase concentration of the aluminum-containing acidic solution is 70 g / L, calculated based on aluminum oxide as the solid-phase substance; the temperature of the aluminum-containing acidic solution is 40°C.

[0151] The solid phase concentration of the carbonate-containing alkaline cleaning solution is 8.5 g / L, calculated based on sodium oxide as the solid phase; the pH value of the carbonate-containing alkaline cleaning solution is 11.4; and the temperature of the carbonate-containing alkaline cleaning solution is 60 DEG C.

[0152] The temperature of the double hydrolysis reaction is 40 DEG C.

[0153] The pH value of the hydrolysis slurry is 7.5.

[0154] The type of the aluminum-containing acidic solution is aluminum nitrate solution.

[0155] Comparative Example 1

[0156] Comparative Example 1 is different from Example 1 in the following aspects, and the rest are the same:

[0157] The carbonate-containing alkaline cleaning solution is directly subjected to membrane separation without using the aluminum-containing acidic solution.

[0158] Comparative Example 2

[0159] Comparative Example 2 is different from Example 1 in the following aspects, and the rest are the same:

[0160] The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline cleaning solution satisfy V1:V2 = 1:40.

[0161] Comparative Example 3

[0162] Comparative Example 3 is different from Example 1 in the following aspects, and the rest are the same:

[0163] The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline cleaning solution satisfy V1:V2 = 1:10.

[0164] Comparative Example 4

[0165] Comparative Example 4 is different from Example 1 in the following aspects, and the rest are the same:

[0166] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline cleaning solution satisfy n1:n2 = 0.2:2.

[0167] Comparative Example 5

[0168] Comparative Example 5 is different from Example 1 in the following aspects, and the rest are the same:

[0169] The amount of substance n1 of aluminum ions in the aluminum-containing acidic solution and the amount of substance n2 of carbonate ions in the carbonate-containing alkaline cleaning solution satisfy n1:n2 = 3:2.

[0170] Comparative Example 6

[0171] The difference between Comparative Example 6 and Example 1 is as follows, and the rest is the same:

[0172] The temperature of the double hydrolysis reaction is 20°C.

[0173] Comparative Example 7

[0174] The difference between Comparative Example 7 and Example 1 is as follows, and the rest is the same:

[0175] The temperature of the double hydrolysis reaction is 100°C.

[0176] Related experiments and effect data:

[0177] The conductivities of the sodium-containing solutions and the soft water of each example and comparative example are collected respectively, and the proportion of the soft water that can be recycled is counted, and the results are shown in Table 1.

[0178] Table 1: Conductivity of sodium-containing solution and soft water of each example and comparative example and proportion of recycled soft water

[0179]

[0180] As can be seen from Table 1, the treatment method of the carbonate-containing alkaline cleaning solution provided by the embodiments of the application reduces the content of salt (especially carbonate) in the alkaline cleaning solution through chemical reaction combined with physical separation, and finally produces soft water with a conductivity of 10 μS / cm to 50 μS / cm, and the recycled soft water accounts for 65% to 85% of the total volume of the soft water.

[0181] Compared with Example 1, Comparative Example 1 does not use an aluminum-containing acidic solution for double hydrolysis reaction treatment, and directly separates the carbonate-containing alkaline cleaning solution by membrane separation. This not only makes it difficult to obtain a sodium-containing solution with low solid phase concentration, but also affects the recycling of the subsequent soft water and causes the blocking of the membrane separation equipment.

[0182] In Comparative Example 2, the amount of carbonate-containing alkaline cleaning solution added is too much, although this makes the double hydrolysis reaction proceed fully, but the soft water obtained contains a large amount of alkaline substances, which is difficult to recycle effectively. In Comparative Example 3, the amount of aluminum-containing acidic solution added is too much, although this makes the double hydrolysis reaction proceed fully, but the impurity ion content in the sodium-containing solution is too much, making the conductivity too large, and ultimately affecting the recycling of the soft water.

[0183] Compared with Example 1, Comparative Example 4 uses less aluminum ions, which makes it difficult for the double hydrolysis reaction to proceed fully, resulting in a large amount of alkaline substances in the soft water, which is difficult to recycle effectively. In Comparative Example 5, more aluminum ions are used, although the double hydrolysis reaction can proceed fully, but the impurity ion content in the sodium-containing solution is too much, making the conductivity too large, and ultimately affecting the recycling of the soft water.

[0184] Compared with Example 1, the lower temperature of the double hydrolysis reaction is used in Comparative Example 6, although the solid phase concentration and conductivity of the sodium-containing solution are not much different from those of Example 1, the low-temperature double hydrolysis reaction can affect the growth of the aluminum hydroxide crystal nucleus and reduce the service life of the subsequent membrane separation; at the same time, the double hydrolysis reaction is difficult to complete, which affects the recycling of the soft water. The higher temperature of the double hydrolysis reaction is used in Comparative Example 7, which makes the carbon dioxide generated by the double hydrolysis reaction escape from the hydrolysis slurry to form bubbles, resulting in a too high water content of the filter cake obtained in the subsequent solid-liquid separation stage, causing the loss of soft water.

[0185] In summary, the processing method of the carbonate-containing alkaline washing solution provided in the embodiments of the present application uses an aluminum-containing acidic solution and a carbonate-containing alkaline washing solution as raw materials, combines chemical reaction (conversion and consumption of main salt) and physical separation (removal of solids and deep desalination), and efficiently reduces the salt content in the alkaline washing solution,

[0186] In addition, the processing method of the carbonate-containing alkaline washing solution provided in the embodiments of the present application replaces the traditional strong acid neutralization process with a double hydrolysis reaction of an aluminum-containing acidic solution and a carbonate-containing alkaline washing solution, which not only avoids the equipment corrosion problem caused by the addition of a large amount of strong acid, avoids the consumption of excess strong acid and the subsequent equipment maintenance cost, but also can promote the aggregation of aluminum hydroxide nanocolloids and the precipitation of aluminum hydroxide by adjusting the pH value of the hydrolysis slurry, significantly improve the stability of the membrane treatment system operation of the membrane separation, and achieve the synergistic goal of efficient treatment of the carbonate-containing alkaline washing solution and recycling of the soft water resource.

[0187] In addition, the processing method of the carbonate-containing alkaline washing solution provided in the embodiments of the present application can stabilize the pH value and ion concentration of the sodium-containing solution, reduce the salt fluctuation of the sodium-containing solution, and effectively improve the service life of the treatment membrane in the membrane separation stage.

[0188] The above only describes specific embodiments of the present application, so that those skilled in the art can understand or implement the present application. Various modifications of these embodiments will be apparent to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features claimed in the present application.

Claims

1. A method for treating an alkaline washing solution containing carbonates, characterized in that, The processing method includes: A carbonate-containing alkaline washing solution and an aluminum-containing acidic solution are subjected to a double hydrolysis reaction to obtain a hydrolyzed slurry; wherein, under the condition of the same cation, the solubility of the compound salt formed by the aluminum-containing acidic solution in the double hydrolysis reaction is greater than the solubility of the carbonate in the carbonate-containing alkaline washing solution, and the pH value of the hydrolyzed slurry is 6.0 to 8.0; The hydrolyzed slurry was subjected to solid-liquid separation to obtain a sodium-containing solution and aluminum hydroxide precipitate; The aluminum hydroxide precipitate was purified to obtain boehmite. The sodium-containing solution was subjected to membrane separation to obtain soft water; The amount of aluminum ions n1 in the aluminum-containing acidic solution and the amount of carbonate ions n2 in the carbonate-containing alkaline washing solution satisfy the following: n1:n2 = (0.5 to 1.5):(2 to 4). The conductivity of the sodium-containing solution is from 10,000 μS / cm to 15,000 μS / cm; The electrical conductivity of the soft water is from 10 μS / cm to 50 μS / cm; The alkaline washing solution containing carbonates contains pseudoboehmite nanoparticles with a particle size of <100nm. The aluminum-containing acidic solution is at least one of aluminum sulfate solution, aluminum nitrate solution, or aluminum chloride solution; The volume V1 of the aluminum-containing acidic solution and the volume V2 of the carbonate-containing alkaline washing solution satisfy the following: V1:V2=1:(15 to 30). Based on alumina as the solid phase, the solid concentration of the aluminum-containing acidic solution is from 50 g / L to 110 g / L. Based on sodium oxide as the solid phase, the solid concentration of the carbonate-containing alkaline washing solution is 7 g / L to 9 g / L.

2. The processing method according to claim 1, characterized in that, The temperature for the double hydrolysis reaction is between 25°C and 90°C.

Images