Hydrotalcite-based hydrogen peroxide bleaching stabilizer and application thereof
By using hydrotalcite material as a bleaching agent, the problem of transition metal ion catalyzing the decomposition of hydrogen peroxide in the prior art is solved, thereby achieving efficient pulp bleaching and environmentally friendly production.
Patent Information
- Application Number
- CN202511000644.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-10-10
AI Technical Summary
In the existing pulp bleaching process, the ineffective decomposition of hydrogen peroxide catalyzed by transition metal ions leads to increased production costs, and traditional stabilizers such as EDTA can cause water pollution and equipment scaling problems.
Hydrotalcite material is used as a hydrogen peroxide bleaching stabilizer. By intercalating silicate ions, it adsorbs heavy metal ions, provides an alkaline environment, reduces the generation of silica scale, and avoids water pollution.
The bleaching efficiency of hydrogen peroxide is improved, the concentration of heavy metal ions in the pulp is reduced, the continuity and environmental protection of the bleaching process are ensured, and water pollution and equipment scaling are avoided.
Smart Images
Figure CN120759150A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of pulping and papermaking, and in particular to a hydrotalcite-based hydrogen peroxide bleaching stabilizer and application thereof. Background Art
[0002] Layered double hydroxide (LDH), also known as hydrotalcite, is a type of two-dimensional anionic clay material. By changing the type and ratio of metal ion elements in the main layer, the size and structure of the guest ions, hydrotalcite materials with the same structure and different functions can be obtained. Precisely because of the diversity of LDH, LDH is widely used in functional materials such as catalysis, adsorption and flame retardants. Magnesium-based and calcium-based hydrotalcites have relatively large specific surface areas, low prices and green and environmentally friendly synthesis processes, making them ideal mineralization materials. At present, there are LDH-based materials for Cu 2+ 、Cd 2+ Reports on materials that can adsorb metal ions.
[0003] Paper plays a vital role in human science, culture, industry, and commerce. The use of paper promotes the dissemination, storage, and exchange of human knowledge. Therefore, the pulp and paper industry is a vital sector related to national livelihoods and holds a crucial position in the national economy. Pulps produced by various pulping methods have varying shades of color, known as natural pulp. This is due to the presence of a certain amount of lignin and other colored substances in pulp. To remove the color and improve paper quality, pulp must be bleached. The purpose of bleaching is to improve the whiteness of the paper by using bleaching agents to destroy and dissolve chromogenic groups and impurities in the pulp, thereby enhancing the quality of the pulp.
[0004] Driven by environmental policies, total chlorine-free (TCF) bleaching technology has become a key industry upgrade. Green bleaching agents, such as hydrogen peroxide (H2O2), leverage their excellent oxidative bleaching properties to not only steadily improve pulp brightness but also, because their decomposition products are exclusively H2O and O2, create a highly efficient, low-energy, and environmentally friendly bleaching system.
[0005] However, there are a small amount of transition metal ions in the pulp, and there is still a problem that the catalysis of transition metal ions will lead to the ineffective decomposition of hydrogen peroxide during the pulp bleaching process, thereby increasing production costs. In the current hydrogen peroxide bleaching system, although sodium silicate (Na2SiO3) can be 2- While complexing transition metals inhibits the ineffective decomposition of H2O2, silica scale deposition can easily lead to equipment loss and production interruptions. EDTA, as a chelating agent, can chelate transition metal ions, rendering them ineffective as catalysts and improving H2O2 utilization efficiency. However, its use can cause water pollution, increasing post-processing costs.
[0006] Therefore, it is a research focus in the pulp bleaching process to find a stabilizer which can effectively prevent or reduce transition metal ion catalysis to inhibit the ineffective decomposition of H2O2, without causing silicon scale damage to equipment and pollution. SUMMARY
[0007] The present application aims to overcome the problems in the prior art and provide a hydrotalcite-based hydrogen peroxide bleaching stabilizer and its application.
[0008] The inventors of the present application have surprisingly found that the application of hydrotalcite materials in the process of bleaching pulp with H2O2 can not only improve the bleaching efficiency of H2O2 and increase the whiteness of paper, but also avoid the problem of scaling affecting continuous production and pollution of water bodies.
[0009] To achieve the above-mentioned purpose, the present application provides, in a first aspect, the application of a hydrotalcite material as a hydrogen peroxide bleaching stabilizer in pulp bleaching.
[0010] The present application provides, in a second aspect, a hydrogen peroxide bleaching stabilizer, wherein the hydrogen peroxide bleaching stabilizer is a hydrotalcite material.
[0011] Through the above technical solutions, the present application has the following beneficial technical effects:
[0012] (1) The application of hydrotalcite materials as hydrogen peroxide bleaching stabilizers in the process of bleaching pulp can reduce the concentration of heavy metal ions in the pulp, thereby improving the bleaching efficiency;
[0013] (2) No water pollution is caused in the bleaching process, and no complex post-treatment is required;
[0014] (3) When MgAl-SiO3 is used as a hydrogen peroxide bleaching stabilizer, it can also provide an alkaline environment for H2O2, reduce the generation of silicon scale, and ensure the continuity of pulp bleaching. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 XRD patterns of CaAl-NO3, CaAl-Cl, MgAl-CO3, MgAl-NO3 and MgAl-SiO3 prepared in Examples 1-3 of the present application; wherein (a) is the XRD pattern of MgAl-CO3, MgAl-NO3 and MgAl-SiO3; (b) is the XRD pattern of CaAl-NO3 and CaAl-Cl;
[0016] Figure 2SEM images of MgAl-CO3, MgAl-NO3 and MgAl-SiO3 at different proportions; a and d are SEM images of MgAl-CO3; b and e are SEM images of MgAl-NO3; c and f are SEM images of MgAl-SiO3;
[0017] Figure 3 is the pulp brightness value using different types of stabilizers;
[0018] Figure 4 It is the COD value of the filtrate using different types of stabilizers. DETAILED DESCRIPTION
[0019] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.
[0020] A first aspect of the present invention provides a use of a hydrotalcite material as a hydrogen peroxide bleaching stabilizer in pulp bleaching.
[0021] In some embodiments of the present invention, the hydrotalcite material is calcium-based hydrotalcite and / or magnesium-based hydrotalcite, preferably magnesium-based hydrotalcite.
[0022] In some embodiments of the present invention, the intercalated anions in the hydrotalcite material are selected from at least one of nitrate ions, chloride ions, carbonate ions and silicate ions, preferably silicate ions.
[0023] In some embodiments of the present invention, the hydrotalcite material is selected from at least one of CaAl-NO3, CaAl-Cl, MgAl-CO3, MgAl-NO3 and MgAl-SiO3, preferably MgAl-SiO3.
[0024] In some embodiments of the present invention, the hydrotalcite material is prepared by a colloid milling method or a hydrothermal method.
[0025] In some embodiments of the present invention, MgAl-NO3 is stripped and then silicate ion intercalated to obtain MgAl-SiO3.
[0026] The present invention uses intercalation to 2- Ions are inserted between the layers of MgAl-LDH to protect the bleaching equipment from producing silica scale, while also giving full play to the effects of MgAl-LDH and SiO3 2-Advantages of adsorbing heavy metal ions during bleaching process.
[0027] Specifically, MgAl-SiO3 can be prepared by the following steps:
[0028] (1) MgAl-CO3 was synthesized by hydrothermal method using magnesium chloride hexahydrate and aluminum chloride hexahydrate as raw materials;
[0029] (2) mixing the MgAl-CO3 prepared in step (1) with a methanol solution of nitric acid, and performing ion exchange on the interlayer host anions of the flexible hydrotalcite under an inert gas atmosphere at room temperature to obtain MgAl-NO3;
[0030] (3) The product obtained in step (2) is dispersed in a formamide solution and stripped at room temperature under an inert gas atmosphere; sodium silicate solution is then added for ion exchange, and after the reaction, MgAl-SiO3 is obtained by washing and drying.
[0031] In the above preparation process, the carbonate ions between the flexible hydrotalcite layers are first exchanged for nitrate ions. The intercalation of nitrate ions expands the interlayer spacing of the hydrotalcite, thereby making the stability of the binding between nitrate ions and the hydrotalcite layers much lower than the stability of the binding between carbonate ions and the hydrotalcite layers, so as to facilitate the subsequent peeling of the hydrotalcite layers and facilitate the subsequent insertion of silicate ions.
[0032] Preferably or optionally, in step (2), the amount of nitric acid added is 100-500 μL per 100 mg of hydrotalcite, and the volume of methanol used to dissolve the nitric acid is 10-25 mL.
[0033] Preferably or optionally, in step (2), the reaction time of ion exchange is 6-24 h.
[0034] Preferably or optionally, the mass of the sodium silicate in step (3) is 50-70% of the mass of the product in step (2), and the volume of deionized water used to dissolve the sodium silicate is 25-35 mL.
[0035] Preferably or optionally, in step (3), the reaction time of ion exchange is 6-24 h.
[0036] Preferably or optionally, in step (3), the cleaning process is ultrasonic cleaning using an ethanol solution, and the drying is heating drying.
[0037] In some embodiments of the present invention, when used, the amount of the hydrotalcite material is 1-10% of the mass of the pulp to be treated, preferably 5%.
[0038] In some embodiments of the present invention, the concentration of the pulp to be treated is 8-12%, preferably 10%.
[0039] A second aspect of the present invention provides a hydrogen peroxide bleaching stabilizer, wherein the hydrogen peroxide bleaching stabilizer is a hydrotalcite material.
[0040] In some embodiments of the present invention, the hydrotalcite material is calcium-based hydrotalcite and / or magnesium-based hydrotalcite, preferably magnesium-based hydrotalcite.
[0041] In some embodiments of the present invention, the intercalated anions in the hydrotalcite material are selected from at least one of nitrate ions, chloride ions, carbonate ions and silicate ions, preferably silicate ions.
[0042] In some embodiments of the present invention, the hydrotalcite material is selected from at least one of CaAl-NO3, CaAl-Cl, MgAl-CO3, MgAl-NO3 and MgAl-SiO3, preferably MgAl-SiO3.
[0043] In some embodiments of the present invention, the hydrotalcite material is prepared by a colloid milling method or a hydrothermal method.
[0044] In some embodiments of the present invention, MgAl-NO3 is stripped and then silicate ion intercalated to obtain MgAl-SiO3.
[0045] The present invention will be described in detail below through examples.
[0046] In the following examples and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents and instruments used, if no manufacturer is specified, are commercially available conventional products.
[0047] Preparation Example 1
[0048] This example is used to illustrate the preparation of CaAl-NO3.
[0049] Dissolve 0.018 mol Ca(NO3)2·6H2O and 0.006 mol Al(NO3)3·6H2O in 100 mL of deionized water and sonicate for 5 minutes. Separately, dissolve 0.0024 mol NaOH and 0.024 mol Na2CO3 in 100 mL of deionized water. Pour the two precursor solutions simultaneously into a high-speed colloid mill (3000 rpm) and react for 1 minute to produce a milky white slurry. Centrifuge the mixture to obtain a white paste, the crude CaAl-LDH product. Wash the mixture several times with deionized water until the pH is neutral, then dry it in an oven at 60°C to obtain CaAl-NO3.
[0050] Preparation Example 2
[0051] This example is used to illustrate the preparation of CaAl-Cl.
[0052] Accurately weigh 0.01 mol of AlCl₃·6H₂O (AR grade) and dissolve it in 100 mL of deionized water. Stir magnetically (600 rpm) for 10 minutes, then sonicate for 5 minutes to obtain a clear solution. Weigh 0.04 mol of Ca(OH)₂ (AR grade) and dissolve it in 100 mL of deionized water. Similarly, sonicate to obtain a homogeneous suspension. Simultaneously pour these two precursor solutions into a high-speed colloid mill (3000 rpm) and react for 1 minute. Centrifuge the reaction product to obtain a crude product, wash it several times with deionized water until the pH is neutral, and then dry it in an oven to obtain CaAl-Cl.
[0053] Preparation Example 3
[0054] This example is used to illustrate the preparation of MgAl-CO3, MgAl-NO3, and MgAl-SiO3.
[0055] (1) Accurately weigh 4.066 g of magnesium chloride hexahydrate (MgCl2·6H2O, AR grade), 2.414 g of aluminum chloride hexahydrate (AlCl3·6H2O, AR grade) and 8.408 g of urea (CO(NH2)2, AR grade) and place them in a 100 mL beaker, and add 100 mL of deionized water; stir at 600 rpm on a magnetic stirrer for 5 min until they are completely dissolved to form a homogeneous transparent solution; transfer the above mixed solution to a 100 mL polytetrafluoroethylene-lined container and seal it in a stainless steel hydrothermal reactor; place the hydrothermal reactor in a forced air drying oven preheated to 120°C, and react at this temperature for 12 hours. Then, wash and dry the product to obtain MgAl-CO3.
[0056] (2) Take 500 mg of MgAl-CO3 and dissolve it in 45 mL of methanol, transfer it to a three-necked flask, and stir it for 6 hours under a nitrogen atmosphere; dissolve concentrated nitric acid in 5 mL of methanol, quickly add it to the three-necked flask and continue stirring for 6 hours. After obtaining the product, wash and centrifuge it, and dry it to obtain MgAl-NO3.
[0057] (3) 1.5 g of MgAl-NO3 was added to 150 mL of formamide solution and stirred under a nitrogen atmosphere for 48 h to exfoliate and form an LDH nanosheet solution with Tyndall effect; then 0.75 g of Na2SiO3 was dissolved in 25 mL of deionized water and added to the LDH nanosheet solution, stirred for 10 min, and the product was centrifuged, washed, and dried to obtain MgAl-SiO3.
[0058] Application Examples
[0059] The hydrotalcite materials prepared in Examples 1-3 were used as hydrogen peroxide bleaching stabilizers for pulp bleaching.
[0060] The bleaching process is as follows: Unbleached softwood pulp is used as the pulp material. A hydrogen peroxide stabilizer (5% by weight of the pulp) is added to a 10% concentration of an absolute dry pulp aqueous solution. The mixed pulp is placed in a sealed polyethylene film bag preheated to 80°C in a constant temperature water bath. The bag is then manually kneaded for 1 minute to ensure thorough mixing. A 3% hydrogen peroxide (H2O2) solution is added and kneaded again for 1 minute to ensure a uniform reaction system. During the constant temperature reaction, the film bag must be completely sealed and manually kneaded every 15 minutes to ensure uniform reaction. The reaction is completed after 2 hours.
[0061] The bleached pulp system is placed in a pulper and water is added to disperse the pulp evenly. The dispersed pulp is placed in a papermaking machine for filtration and drying to form paper. The details are as follows:
[0062] (1) Add tap water to 5L;
[0063] (2) Pneumatic stirring for 30 seconds;
[0064] (3) Rapid drainage;
[0065] (4) Vacuum dehydration for 30 seconds;
[0066] (5) Place the filtered paper in a drying area and dry it at 100°C for 6 minutes under high pressure. The resulting paper is used to measure pulp brightness.
[0067] Test Example 1
[0068] Depend on Figure 1 From the XRD spectrum analysis, it can be seen that in the XRD spectrum of MgAl-CO3, the XRD spectrum of CaA1-Cl and the XRD spectrum of CaAl-NO3, all the diffraction peaks of the synthesized samples match well with the standard spectrum of MgAl-CO3 (JPCDS card number 35-0964), the standard spectrum of CaAl-Cl (JPCDS card number 35-0105) and the standard spectrum of CaAl-NO3 (JPCDS card number 54-0849), respectively, indicating that MgAl-CO3, CaAl-Cl and CaAl-NO3 were successfully prepared.
[0069] Depend on Figure 1(a) It can be seen that the characteristic peaks of MgAl-LDH of carbonate intercalation in the XRD spectrum of MgAl-NO3 have all disappeared, and new peaks appear at 9.9°, 19.9° and 34.73°, which correspond to the (003), (006) and (012) crystal planes of nitrate intercalation LDH respectively. Since the (003) crystal plane diffraction peak appears at 9.9°, the Bragg equation shows that the interlayer spacing of MgAl-NO3 is 0.89nm. After MgAl-NO3 was stripped in formamide solution for 48h, the intercalation anion SiO3 was obtained after adding sodium silicate. 2- The diffraction peak corresponding to (003) of MgAl-SiO3 shifts forward to 7.6°. According to the Bragg equation, the interlayer spacing increases to 1.15nm.
[0070] Figure 2 a and d are SEM images of MgAl-CO3, b and e are SEM images of MgAl-NO3, and c and f are SEM images of MgAl-SiO3, indicating that MgAl-CO3, MgAl-NO3 and MgAl-SiO3 are all two-dimensional sheet materials with layered stacking. Since MgAl-SiO3 is obtained by exfoliation, compared with MgAl-CO3 and MgAl-NO3, MgAl-SiO3 has more defects, which is beneficial to improving the adsorption capacity of the adsorbent.
[0071] Test Example 2
[0072] The effects of the five hydrotalcite materials prepared in Examples 1-3 and EDTA as a stabilizer on the pulp brightness during the H2O2 bleaching process were evaluated.
[0073] The following is an analysis of the effect after bleaching.
[0074] Through analysis Figure 3 It can be seen that layered double hydroxide (LDH) as a stabilizer shows significant advantages over EDTA in improving paper whiteness. Among them, magnesium-based hydrotalcite has a particularly outstanding whiteness improvement effect, which is significantly better than calcium-based hydrotalcite. Specifically, MgAl-SiO3 performs best among magnesium-based hydrotalcites. The whiteness of the paper is measured by a whiteness meter and the whiteness of the paper is increased to 59.88%. Figure 4 The data shows that the chemical oxygen demand (COD) of the filtrate produced by EDTA during the pulp bleaching process is significantly higher than that of the LDH system, indicating that the filtrate pollution load of the LDH bleaching process is lower, has better ecological and environmental protection characteristics, and meets the development needs of green papermaking.
[0075] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.
Claims
1. Application of hydrotalcite as hydrogen peroxide bleaching stabilizer in pulp bleaching.
2. The use according to claim 1, wherein The hydrotalcite material is calcium-based hydrotalcite and / or magnesium-based hydrotalcite, preferably magnesium-based hydrotalcite; Preferably, the intercalated anions in the hydrotalcite material are selected from at least one of nitrate ions, chloride ions, carbonate ions and silicate ions, preferably silicate ions.
3. The use according to claim 1 or 2, wherein: The hydrotalcite material is selected from at least one of CaAl-NO3, CaAl-Cl, MgAl-CO3, MgAl-NO3 and MgAl-SiO3, preferably MgAl-SiO3.
4. The use according to any one of claims 1 to 3, wherein The hydrotalcite material is prepared by a colloid milling method or a hydrothermal method.
5. The use according to any one of claims 1 to 4, wherein MgAl-NO3 is stripped and then silicate ion intercalated to obtain MgAl-SiO3.
6. The use according to any one of claims 1 to 5, wherein When used, the amount of the hydrotalcite material is 1-10% of the mass of the pulp to be treated, preferably 5%; Preferably, the consistency of the pulp to be treated is 8-12%, preferably 10%.
7. A hydrogen peroxide bleaching stabilizer, characterized in that The hydrogen peroxide bleaching stabilizer is a hydrotalcite material.
8. The hydrogen peroxide bleaching stabilizer according to claim 7, wherein The hydrotalcite material is calcium-based hydrotalcite and / or magnesium-based hydrotalcite, preferably magnesium-based hydrotalcite; Preferably, the intercalated anions in the hydrotalcite material are selected from at least one of nitrate ions, chloride ions, carbonate ions and silicate ions, preferably silicate ions.
9. The hydrogen peroxide bleaching stabilizer according to claim 7 or 8, wherein The hydrotalcite material is selected from at least one of CaAl-NO3, CaAl-Cl, MgAl-CO3, MgAl-NO3 and MgAl-SiO3, preferably MgAl-SiO3.
10. The hydrogen peroxide bleaching stabilizer according to any one of claims 7 to 9, wherein The hydrotalcite material is prepared by a colloid milling method or a hydrothermal method; Preferably, MgAl-NO3 is stripped and then silicate ion intercalated to obtain MgAl-SiO3.