A magnesium hydroxide emulsion and its preparation method

Abstract

This application relates to a magnesium hydroxide emulsion and its preparation method, specifically a high-solids-content magnesium hydroxide emulsion with a solids content of 50%-55%, maintaining good fluidity at this content and remaining stable for three months without stratification. The magnesium hydroxide emulsion comprises 30-60 parts by weight of magnesium hydroxide, 20-50 parts by weight of water, 0-2 parts by weight of dispersant, 0-2 parts by weight of thickener, and 0-4 parts by weight of surfactant. In comparison, the magnesium hydroxide suspension prepared by this application maintains high stability, does not stratify after standing for several months, and exhibits good fluidity, allowing for direct use when needed. This application also provides a method for preparing the aforementioned magnesium hydroxide emulsion.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment, specifically to a magnesium hydroxide emulsion for wastewater treatment, its preparation method, and its application in wastewater treatment. Background Technology

[0002] The main hazards of acidic wastewater are corrosion of sewer pipes, hydraulic structures, and factory foundations; its discharge into water bodies harms the reproduction of aquatic animals and affects crop growth; and the harm is even more severe with acidic wastewater containing heavy metals. Therefore, appropriate treatment is essential.

[0003] The main method for treating acidic wastewater is neutralization. Chemical neutralization involves adding alkaline agents to the acidic wastewater to neutralize it. Commonly used neutralizing agents include lime, limestone, sodium hydroxide, ammonium hydroxide, and sodium carbonate. Lime is widely available, inexpensive, and commonly used, but it results in poor working conditions, a large amount of neutralization residue (approximately 2% of the treated water volume), and difficulty in dewatering. Additionally, alkaline wastes such as calcium carbide slag and alkali residue are also good neutralizing agents for treating waste with waste. Sodium hydroxide, sodium carbonate, and ammonium hydroxide produce complete neutralization reactions, are easy to control pH, and do not form precipitates, but they are more expensive and not widely used in China. In chemical neutralization, the use of neutralizing agents increases the salt content of the wastewater. For example, if the wastewater contains sulfuric acid, neutralization with calcium salts will produce insoluble calcium sulfate precipitates, and may also form a surrounding layer on the surface of the agent particles, affecting the continuation of the neutralization reaction.

[0004] Magnesium hydroxide, as an alkaline compound with a cost-effectiveness between sodium hydroxide and lime, is receiving increasing attention in the treatment of acidic wastewater. However, when magnesium hydroxide is used as a powder solid, its neutralization efficiency is low. When used as a suspension, although the efficiency is higher, its easy settling property causes significant problems in storage and transportation. These factors limit the application of magnesium hydroxide in the treatment of acidic wastewater.

[0005] Existing technologies disclose methods for preparing magnesium hydroxide emulsions. For example, Chinese patent document CN01130682.3 describes a reaction at 100-200°C for 2-12 hours to prepare magnesium hydroxide nanoparticles. Chinese patent CN1341694 describes a reaction in a rotating bed with a curing temperature of 80-100°C. Chinese patent CN00135436.1 does not provide details of the reaction process; the surfactant additives used are potassium salt and OP-10, and the resulting product needs to be ground to achieve dispersion. Furthermore, the reported size is the crystal size measured by X-ray diffraction. Chinese patent CN00136739.0 uses a pre-mixed liquid film reactor. Chinese patent CN02133360.2 describes a reaction in a high-speed stirred reactor, proceeding in only one phase, followed by 5 hours of sonication, drying the resulting gel, and then grinding. Chinese patent 201210097004.7 synthesizes magnesium hydroxide suspension in a liquid phase system using anion exchange resin, but the process is complex, and the prepared suspension exhibits significant sedimentation after short-term standing, resulting in poor stability. Chinese patent 202111595456.3 produces a magnesium hydroxide suspension with a solid content of less than 50%, and it exhibits stratification and gelation after eight weeks of standing, indicating an excessively short retention time, which is unfavorable for large-scale industrial application. Chinese patent CN201310002869.5 describes a magnesium hydroxide liquid-phase dispersion with a solid content of 1wt%-50wt%, but due to the use of nano-magnesium hydroxide, prior modification is required, making the process complex and costly.

[0006] Due to the aforementioned problems, readily available high-solids-content magnesium hydroxide emulsions are particularly important. However, if magnesium hydroxide particles are simply dispersed naturally in water, they will quickly agglomerate and settle. Furthermore, the larger the particle size of magnesium hydroxide, the faster it settles, and over time, it will clump together. To avoid clumping, the only way is to continuously stir the magnesium hydroxide emulsion throughout the process. However, this is extremely inconvenient to use and consumes a lot of energy, severely limiting the application of magnesium hydroxide emulsions. Summary of the Invention

[0007] To address the aforementioned technical problems, this application proposes a high-solids-content magnesium hydroxide emulsion, its preparation method, and its application in wastewater treatment. The magnesium hydroxide emulsion prepared using this method can achieve a solids content of 50wt%-70wt%, while still maintaining good fluidity and stability. It can be stored for ten months without showing stratification or gelation, and its properties remain consistently stable. Furthermore, the preparation method is simple to operate, has low energy consumption, high reproducibility, good product quality, and is easy to scale up.

[0008] The first inventive point of this application is to provide a magnesium hydroxide emulsion with a high solids content.

[0009] Furthermore, the magnesium hydroxide emulsion comprises magnesium hydroxide particles and a liquid phase medium, wherein the magnesium hydroxide particles are uniformly dispersed in the liquid phase medium.

[0010] Furthermore, the solid content in the liquid dispersion is 50wt%-70wt%.

[0011] Preferably, the solid content in the liquid dispersion is 50wt%-60wt%; more preferably, the solid content in the liquid dispersion is 50wt%-55wt%.

[0012] Furthermore, the liquid medium is water, an organic solvent, or a mixture of water and an organic solvent.

[0013] Preferably, the liquid medium is water.

[0014] Furthermore, the magnesium hydroxide emulsion also includes dispersants, thickeners, and surfactants.

[0015] Furthermore, the mass fractions of each component in the magnesium hydroxide emulsion are: 30-60 parts magnesium hydroxide, 20-50 parts water, 0-2 parts dispersant, 0-2 parts thickener and 0-4 parts surfactant.

[0016] Preferably, the magnesium hydroxide is present in 40-70 parts by mass; more preferably, the magnesium hydroxide is present in 40-55 parts by mass.

[0017] Furthermore, the dispersant is a polymeric compound, including but not limited to polycarboxylate and polycarboxylate ester.

[0018] Furthermore, the thickener is a polysaccharide compound, including but not limited to polydextrose, chitosan, cellulose, xanthan gum, and guar gum.

[0019] Furthermore, the surfactant is an amphiphilic compound, including but not limited to Span 80, Tween, polyoxyethylene ethers, and benzenesulfonates.

[0020] The second inventive point of this application is to provide a method for preparing the magnesium hydroxide emulsion.

[0021] Furthermore, the method includes:

[0022] S1. Ball mill dispersed powder: The mixture of magnesium hydroxide and water is placed in a ball mill and dispersed to obtain a magnesium hydroxide dispersion;

[0023] S2. Preparation of magnesium emulsion: Add dispersant, thickener and surfactant to the dispersion obtained in step S1, and stir for 2 hours to obtain magnesium emulsion;

[0024] Further, in step S1, the ball mill is a planetary ball mill with a rotation speed of 600-900 rpm, a ball milling time of 30-60 minutes, and a ball-to-material ratio of (3-5):1.

[0025] Furthermore, the mass concentration of the magnesium hydroxide dispersion obtained in step S1 is 40%-70%.

[0026] Preferably, the mass concentration of the magnesium hydroxide dispersion is 50%-60%.

[0027] Further, in step S2, the mass ratio of the magnesium hydroxide dispersion, dispersant, thickener and surfactant is (30-60):(0-2):(0-2):(0-4).

[0028] Furthermore, in step S2, the stirring time is 1-5 hours and the stirring speed is 100-200 rpm.

[0029] The third inventive point of this application is to provide the application of the magnesium hydroxide emulsion in wastewater treatment.

[0030] The magnesium hydroxide emulsion can be applied in fields such as acidic gas absorption and industrial acidic wastewater treatment, and can be used as an alkaline reagent for treating acidic wastewater.

[0031] This application has the following beneficial effects:

[0032] 1. The high-solids-content magnesium hydroxide emulsion of this application has a solids content of 50%-70%, and still maintains good fluidity at this high content. Furthermore, the fluid dispersion does not exhibit stratification even after prolonged standing, achieving a balance between fluidity and stability. In contrast, existing similar suspensions or dispersions have complex preparation processes, high solids content, poor fluidity, or exhibit significant sedimentation and poor stability after short periods of standing.

[0033] 2. The surfactant forms a coating layer on the surface of magnesium hydroxide particles, which is beneficial for the formation of monodisperse magnesium hydroxide particles in the aqueous or organic phase. The magnesium hydroxide surface has a large number of hydroxyl groups, which react with the surfactant. Furthermore, the large organic groups provided by the surfactant coating on the magnesium hydroxide surface create significant steric hindrance, making it difficult for particles to aggregate.

[0034] 3. The use of dispersants greatly improves the hydration efficiency and water dispersibility of magnesium hydroxide, giving magnesium hydroxide emulsions advantages such as high solid content, resistance to agglomeration, high stability, high fluidity, and low viscosity, making them convenient for transportation and storage. Due to their excellent dispersibility and stability, the application range of magnesium hydroxide emulsions has been expanded.

[0035] 4. In the preparation of magnesium hydroxide emulsion, the selection of suitable surfactants, thickeners, and dispersants is crucial. Simultaneously, controlling the ratio of surfactants and raw materials, reaction rates, and time are all technical challenges that need to be addressed. Ultimately, by determining the appropriate process parameters, the prepared magnesium hydroxide emulsion achieved a solid content of 50%-60% while maintaining good fluidity, a stability time exceeding 12 months, and a simple, easy-to-operate, highly reproducible process with good product quality and easy scale-up. Attached Figure Description

[0036] Figure 1 The magnesium emulsion prepared in this application.

[0037] Figure 2 : Figure 1 The image shows the state of the magnesium emulsion after 18 months of storage. Detailed Implementation

[0038] The following detailed description is provided to make the objectives, technical solutions, and advantages of this application clearer. However, it should be understood that the description herein is merely for explaining this application and is not intended to limit the scope of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. All reagents and instruments used herein are commercially available, and the characterization methods involved can be found in relevant descriptions in the prior art, and will not be repeated here.

[0040] The present application will now be described in further detail with reference to the preferred embodiments.

[0041] Example 1

[0042] The first inventive point of this application is to provide a magnesium hydroxide emulsion with a high solids content.

[0043] The magnesium hydroxide emulsion of this application comprises magnesium hydroxide particles and a liquid phase medium, wherein the magnesium hydroxide particles are uniformly dispersed in the liquid phase medium.

[0044] The solid content in the liquid dispersion is 50wt%-70wt%.

[0045] As a further preferred embodiment, the solid content in the liquid dispersion is 50wt%-60wt%.

[0046] In some embodiments, the solid content in the liquid dispersion is 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, or 60 wt%.

[0047] Furthermore, the liquid medium is water, an organic solvent, or a mixture of an organic solvent miscible with water and water.

[0048] As a further preferred embodiment, the liquid medium is water.

[0049] Furthermore, the magnesium hydroxide emulsion comprises magnesium hydroxide, water, dispersant, thickener, and surfactant.

[0050] Furthermore, the mass fractions of each component in the magnesium hydroxide emulsion are: 30-60 parts magnesium hydroxide, 20-50 parts water, 0-2 parts dispersant, 0-2 parts thickener and 0-4 parts surfactant.

[0051] As a further preferred embodiment, the magnesium hydroxide emulsion contains the following components in parts by mass: 40-55 parts magnesium hydroxide, 35-45 parts water, 0.5-1.5 parts dispersant, 0.5-1.5 parts thickener, and 1-2 parts surfactant.

[0052] As a further preferred embodiment, the magnesium hydroxide emulsion comprises the following components in parts by mass: 48-52 parts magnesium hydroxide, 38-44 parts water, 1-1.2 parts dispersant, 0.8-1.2 parts thickener, and 1.5-2 parts surfactant.

[0053] Furthermore, the dispersant is a polymeric compound, including but not limited to polycarboxylate and polycarboxylate ester.

[0054] As a further preferred embodiment, the dispersant is sodium polyacrylate, polyethylene glycol polyacrylate, sodium lignosulfonate, or any combination of the above components.

[0055] Furthermore, the thickener is a polysaccharide compound.

[0056] As a further preferred embodiment, the thickener may be polydextrose, chitosan, cellulose, xanthan gum, guar gum, or any combination of the above components.

[0057] As a further preferred embodiment, the thickener is polyacrylamide or xanthan gum.

[0058] Furthermore, the surfactant is an amphiphilic compound.

[0059] As a further preferred embodiment, the surfactant may be Span 80, Tween, polyoxyethylene ether, benzenesulfonate, or any combination of the above components.

[0060] As a further preferred embodiment, the surfactant is Tween.

[0061] In existing technologies, surface modification agents are often used to modify magnesium hydroxide particles, which leads to increased hydrophobicity, poor dispersion in aqueous phase, and the introduction of impurities. This application does not use surface modifiers. Instead, it relies on selecting suitable surfactants, thickeners, and dispersants, and determining the optimal surfactant and the ratio between each raw material, to ensure stable dispersion of magnesium hydroxide particles in the aqueous phase. This effectively avoids particle agglomeration, overcomes the biggest difficulty in existing technologies, and greatly expands its application range.

[0062] Example 2

[0063] This embodiment details the preparation method of the magnesium hydroxide emulsion of this application, which includes:

[0064] S1. Preparation of magnesium hydroxide dispersion:

[0065] Magnesium hydroxide is mixed with a liquid medium and then dispersed to obtain a magnesium hydroxide dispersion.

[0066] As a further preferred embodiment, the liquid medium is water.

[0067] As a further preferred embodiment, magnesium hydroxide particles and water are mixed in a ball mill, which is a planetary ball mill, and the mixing speed is 600-900 rpm, such as 600 rpm, 700 rpm, 800 rpm or 900 rpm.

[0068] The ball milling time is 30-60 minutes, and the ball-to-material ratio is (3-5):1, such as 3:1, 4:1 or 5:1.

[0069] As a further preferred embodiment, the mass concentration of the magnesium hydroxide dispersion obtained after ball milling is 30%-60%.

[0070] As a further preferred embodiment, the mass concentration of the magnesium hydroxide dispersion is 40%-60%, such as 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, or 60%.

[0071] S2. Add the dispersant, thickener and surfactant to the magnesium hydroxide dispersion obtained in step S1, and mix to obtain the magnesium hydroxide emulsion.

[0072] The mass ratio of the dispersant, the thickener, and the surfactant in the magnesium hydroxide dispersion is (30-60):(0-2):(0-2):(0-4).

[0073] As a further preferred embodiment, the mass ratio of the dispersant, the thickener and the surfactant in the magnesium hydroxide dispersion is (40-60):(0.8-1.2):(0.7-1.2):(1-3).

[0074] In step S2, the stirring time is 1-5 hours and the stirring speed is 100-200 rpm.

[0075] As a further preferred embodiment, the stirring time is 2-3 hours and the stirring speed is 120-160 rpm.

[0076] Controlling the ratio of surfactants and raw materials, reaction rate, and time are all technical challenges that need to be addressed. This embodiment, by controlling process parameters such as reactant ratio, reaction rate, and time, prepares a magnesium hydroxide emulsion with a solid content of 50%-60% while maintaining good fluidity and a stability time exceeding 12 months. Furthermore, the process is simple, easy to operate, highly repeatable, produces high-quality products, and is easily scaled up.

[0077] Example 3

[0078] This embodiment provides a magnesium hydroxide emulsion and its preparation method, the method comprising the following steps:

[0079] S1. Ball mill dispersion of powder: Magnesium hydroxide with a mass concentration of 50% and water are dispersed in a ball mill;

[0080] S2. Preparation of magnesium emulsion: 0.2% sodium polyacrylate, 0.5% guar gum, and 1% oleamide were added to the dispersion obtained in step S1, and the mixture was stirred for 2 hours to obtain the magnesium hydroxide emulsion.

[0081] Results: The obtained magnesium hydroxide emulsion had a solid content of 58%, a viscosity of 350 cps, and no sedimentation after standing for 12 months.

[0082] Example 4

[0083] This embodiment provides a magnesium hydroxide emulsion and its preparation method, the method comprising the following steps:

[0084] S1. Ball mill dispersion of powder: A mixture of 60% magnesium hydroxide and water is placed in a ball mill and dispersed.

[0085] S2. Preparation of magnesium emulsion: Add 0.8% polyacrylate, 0.8% gelatin, and 1% sodium dodecyl sulfate to the dispersion obtained in step S1, and stir for 2 hours to obtain magnesium emulsion;

[0086] Results: The obtained magnesium hydroxide emulsion was as follows Figure 1 As shown, its solid content is 60%, the emulsion viscosity is 250 cps, and it stabilizes after 18 months as follows. Figure 2 As shown, there is no stratification or settlement phenomenon.

[0087] Example 5

[0088] This embodiment provides a magnesium hydroxide emulsion and its preparation method, the method comprising the following steps:

[0089] S1. Ball mill dispersion of powder: A mixture of 40% magnesium hydroxide and water is placed in a ball mill and dispersed.

[0090] S2. Preparation of magnesium emulsion: Add 2% sodium polymaleate, 1% xanthan gum, and 1% Tween to the dispersion obtained in step S1, and stir for 2 hours;

[0091] Results: The obtained magnesium hydroxide emulsion had a solid content of 60%, a viscosity of 200 cps, and a stability time of 12 months.

[0092] Example 6

[0093] This embodiment provides a magnesium hydroxide emulsion and its preparation method, the method comprising the following steps:

[0094] S1. Ball mill dispersion of powder: A mixture of 53% magnesium hydroxide and water is placed in a ball mill and dispersed.

[0095] S2. Preparation of magnesium emulsion: Add 2% polyacrylate, 1% xanthan gum, and 2% triethanolamine oleate to the dispersion obtained in step S1, and stir for 2 hours;

[0096] Results: The obtained magnesium hydroxide emulsion had a solid content of 55%, a viscosity of 180 cps, and a stability time of 13 months.

[0097] Example 7

[0098] This embodiment provides a magnesium hydroxide emulsion and its preparation method, the method comprising the following steps:

[0099] S1. Ball mill dispersion of powder: A mixture of 43% magnesium hydroxide and water is placed in a ball mill and dispersed.

[0100] S2. Preparation of magnesium emulsion: Add 3% polyacrylate, 1% polyacrylamide, and 2% Tween to the dispersion obtained in step S1, and stir for 3 hours;

[0101] Results: The obtained magnesium hydroxide emulsion had a solid content of 55%, a viscosity of 320 cps, and a stability time of 15 months.

Claims

1. A magnesium hydroxide emulsion, characterized in that, The magnesium hydroxide emulsion comprises magnesium hydroxide particles and water, wherein the magnesium hydroxide particles are uniformly dispersed in the water, and the solid content of the magnesium hydroxide emulsion is 50wt%-60wt%. The magnesium hydroxide emulsion further comprises a dispersant, a thickener, and a surfactant. The magnesium hydroxide emulsion comprises 48-52 parts by weight of magnesium hydroxide, 38-44 parts by weight of water, 1-1.2 parts by weight of dispersant, 0.8-1.2 parts by weight of thickener, and 1.5-2 parts by weight of surfactant. The dispersant is a polymer compound; the thickener is a polysaccharide compound; and the surfactant is an amphiphilic compound.

2. The magnesium hydroxide emulsion according to claim 1, characterized in that, The dispersants include, but are not limited to, polycarboxylate salts and polycarboxylate esters; the thickeners include, but are not limited to, polydextrose, chitosan, cellulose, xanthan gum, and guar gum.

3. The magnesium hydroxide emulsion according to claim 1, characterized in that, The surfactants include, but are not limited to, Span 80, Tween, polyoxyethylene ethers, and benzenesulfonates.

4. A method for preparing a magnesium hydroxide emulsion as described in any one of claims 1-3, characterized in that, Includes the following steps: S1, magnesium hydroxide particles and water are mixed to obtain a magnesium hydroxide dispersion; S2, add the dispersant, thickener and surfactant to the magnesium hydroxide dispersion obtained in step S1 to obtain magnesium hydroxide emulsion.

5. The preparation method according to claim 4, characterized in that, In step S1, the magnesium hydroxide particles and water are mixed and then placed in a ball mill for mixing. The ball mill is a planetary ball mill with a rotation speed of 600-900 rpm and a milling time of 30-60 minutes. The ball-to-material ratio is (3-5):1, and the mass concentration of the magnesium hydroxide dispersion is 40%-70%.

6. The preparation method according to claim 4, characterized in that, In step S2, the stirring time is 1-5 hours and the stirring speed is 100-200 rpm.

7. The application of a magnesium hydroxide emulsion as described in any one of claims 1-3 or the magnesium hydroxide emulsion obtained by the preparation method described in any one of claims 4-6 in wastewater treatment.

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