Method for producing sodium bentonite from calcium bentonite

Abstract

The invention belongs to the technical field of sodium bentonite, and particularly relates to a method for producing sodium bentonite by using calcium bentonite, which comprises the following steps: S1, preliminary mixing: crushing the calcium bentonite to 90-110 meshes, and then mixing with a composite sodium modifying agent according to the mass ratio of 1: (0.03-0.10); s2, mechanical shearing: treating the mixture obtained in the step S1 in a high-speed shearing machine at the rotating speed of 2000-4000 r / min for 10-40 minutes; s3, sodium modification: adding deionized water of which the mass is 1-1.5 times that of the bentonite after mechanical shearing in the step S2, and stirring and reacting for 1-2 hours at the temperature of 60-80 DEG C; and S4, drying: performing centrifugal dewatering on the sodium modified bentonite in the step S3, drying at 120-150 DEG C, and crushing to 200-300 meshes to obtain the product. According to the method for producing the sodium bentonite from the calcium bentonite, the preparation method is simple, the sodium modification efficiency is high, the reaction time is short, rare earth catalysis, nano intercalation and a bio-based additive are combined for the first time, a traditional sodium modification theory framework is broken through, and the prepared product is good in performance and high in expansion capacity, reaches the standard of bentonite for high-end casting and is suitable for high-end application scenes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium bentonite and specifically relates to a method for producing sodium bentonite from calcium bentonite. BACKGROUND

[0002] The calcium bentonite is mainly montmorillonite, and the exchangeable cation is mainly Ca² + . The natural calcium bentonite is hard in texture, low in water absorption and expansion (about 3-5 times of expansion ratio), poor in dispersibility, and neutral to weakly alkaline in pH value. The calcium bentonite has the advantages of low cost (abundant natural resources and no modification required), good thermal stability, and no cracking at high temperature. The calcium bentonite has moderate adsorption and is suitable for part of industrial needs. However, the calcium bentonite has weak expansion and adhesion, and the application is limited. The sodium modification is required to be used in high-performance fields. The calcium bentonite is mainly used for ordinary sand mold binders, iron ore pellet binders, soil conditioners, fertilizer carriers, and preliminary adsorption of pollutants (higher efficiency after modification).

[0003] The sodium bentonite is mainly montmorillonite, and the exchangeable cation is Na + . The natural sodium bentonite is rare, and is mainly obtained by sodium treatment (alkali modification) of calcium bentonite. The sodium bentonite has strong water absorption and expansion (about 15-30 times of expansion ratio), good dispersibility, high viscosity, and alkaline pH value. The sodium bentonite has the advantages of high expansion, strong adhesion, good colloidal suspension stability, and strong adsorption capacity, and is suitable for high-end applications. However, the sodium bentonite has high cost (processing or dependence on rare natural resources), and may shrink at high temperature. The sodium bentonite is mainly used for mud thickening agents, well wall stabilization, anti-seepage walls, tunnel shield lubrication, wastewater treatment adsorbents, cat litter, skin care thickening agents, and precision casting sand binders.

[0004] The calcium bentonite is economical and suitable for basic industries, but has limited performance and needs modification. The sodium bentonite has high performance and is widely used, but depends on processing or rare resources and has high cost.

[0005] CN110606494A discloses a method for producing sodium bentonite from calcium bentonite. The method is characterized in that the calcium bentonite is dried to have a water content of 13%-18%, 20 kg of alkali is added to 1000 kg of the calcium bentonite, the mixture is uniformly stirred by a stirrer, large blocks are crushed by a crusher, water is added and the mixture is uniformly stirred, the mixture is extruded by an electric heating extruder with a power of more than 300 W and a material temperature of more than 80° for 15-30 minutes, and the sodium bentonite is obtained. The method is mainly used for manually extruding natural calcium bentonite to obtain sodium bentonite. The obtained sodium bentonite is suitable for products such as paint and putty powder and is used as an adhesive. The method has the advantages of simple process, less additives, low cost, and fast processing. However, the performance of the obtained sodium bentonite is still not ideal.

[0006] There are three technical bottlenecks in the traditional sodiumization process: (1) low ion replacement efficiency: the combination of calcium ions and montmorillonite lattice can reach 158 kJ / mol, and it is difficult for conventional sodiumizing agent to achieve deep replacement. Dry process needs long time calcination, resulting in high energy consumption and lattice damage. (2) Reaction kinetics limitation: although wet process can improve the reaction activity, the diffusion of sodium ions is hindered, and calcium-based bentonite expands to form a gel layer when it comes into contact with water, which hinders the diffusion of sodium ions to the inside of the crystal layer. (3) Unstable product performance: although semi-dry process can shorten the reaction time, the incomplete sodiumization in local area caused by uneven mixing. Therefore, a new method for producing sodium-based bentonite from calcium-based bentonite is needed. SUMMARY

[0007] To solve the above technical problems, the present application provides a method for producing sodium-based bentonite from calcium-based bentonite, comprising the following steps:

[0008] S1. Preliminary mixing: crushing the calcium-based bentonite to 90-110 mesh, and then mixing with the composite sodiumizing agent at a mass ratio of 1:(0.03-0.10);

[0009] S2. Mechanical shearing: treating the mixture obtained in step S1 in a high-speed shearing machine at a speed of 2000-4000 r / min for 10-40 min;

[0010] S3. Sodiumization: adding 1-1.5 times the mass of deionized water to the bentonite after mechanical shearing in step S2, and stirring and reacting at a temperature of 60-80℃ for 2-4 h;

[0011] S4. Drying: centrifugal dewatering, drying at 120-150℃, and crushing to 200-300 mesh to obtain the product.

[0012] Further, the composite sodiumizing agent in step S1 is a mixture of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide. Sodium carbonate is the main sodiumizing agent, which provides the main Na + replacement Ca² + ; sodium polyacrylate is an anionic polyelectrolyte, which produces electrostatic repulsion by adsorbing on the particle surface to prevent agglomeration; sodium silicate: hydrolysis generates SiO 2- and OH - , forming an alkaline environment to promote CaCO3 precipitation, while SiO 2- inserts into the interlayer to enhance the structural stability; montmorillonite nanosheet expands the interlayer spacing through intercalation and exfoliation effect, providing a fast diffusion channel for Na + , shortening the ion replacement path and accelerating the replacement rate; rare earth ions replace Ca² +Forming [La-Ca-O] transition state complex, reducing substitution activation energy, increasing reaction rate. The composite sodium agent forms a multi-component composite system, and the montmorillonite nanosheet and lanthanum oxide synergistically act on the structure to significantly increase the sodiumization rate.

[0013] Further, the mass ratio of the sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide is 10:2:0.8:0.2:0.01.

[0014] Further, the mechanical shearing process in the step S2 is: first, treating at a rotating speed of 2000 r / min for 15 min, and then increasing the rotating speed to 3500 r / min for 10 min. In the first stage shearing process (2000 r / min), the van der Waals force between particles is broken, and the sodiumizing agent is preliminarily dispersed; in the second stage (3500 r / min), high shear force is generated to reduce the particle size from 50 μm to 8 μm, and increase the specific surface area.

[0015] Further, 0.6wt% of an auxiliary agent is added to the deionized water in the step S3, and the auxiliary agent is a mixture of trisodium citrate. Trisodium citrate, as a chelating agent, can chelate Ca² + Forming a stable complex, moving the substitution reaction equilibrium to the product direction, and improving the sodiumization rate.

[0016] Further, 0.6wt% of an auxiliary agent is added to the deionized water in the step S3, and the auxiliary agent is a mixture of trisodium citrate. Trisodium citrate, as a chelating agent, can chelate Ca² + Chelating, and simultaneously inhibiting recalcification by anchoring in the interlayer of montmorillonite through hydrogen bonds; the cationic characteristics of the quaternary ammonium salt of chitosan neutralize the negative charge on the particle surface, and promote flocculation and dewatering.

[0017] Further, before adding water in the step S3, the mixture is subjected to microwave action at a frequency of 2.45 GHz and a power of 500 W for 5 min, and then subjected to ultrasonic action at a frequency of 20 kHz and a power of 100 W for 10 min. The microwave heat effect selectively heats polar molecules, generates local hot spots, and accelerates the desorption of interlayer water molecules. The ultrasonic wave generates micro-jet impact on the particle surface, and the increased surface porosity is beneficial to the sodiumization reaction.

[0018] The method for preparing sodium-based bentonite from calcium-based bentonite prepared by the method has the advantages of simple preparation method, high sodiumization efficiency, short reaction time, combination of rare earth catalysis, nano intercalation and biological-based auxiliary agent, breaking through the traditional sodiumization theoretical framework, good product performance, high swelling capacity, reaching the high-end casting bentonite standard, and being suitable for high-end application scenarios. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear and explicit, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0020] Embodiment 1

[0021] A method for producing sodium-based bentonite from calcium-based bentonite, comprising the following steps:

[0022] S1. Preliminary mixing: 10 kg of calcium-based bentonite is crushed to 90-110 mesh, and then mixed with 600 g of composite sodium agent;

[0023] S2. Mechanical shearing: the mixture obtained in step S1 is first treated at a speed of 2000 r / min for 15 min, and then treated at a speed of 3500 r / min for 10 min in a high-speed shearing machine;

[0024] S3. Sodiumization: the bentonite after mechanical shearing in step S2 is added with 12 kg of deionized water in terms of mass, and stirred and reacted at a temperature of 70-80℃ for 1.8 h;

[0025] S4. Drying: the bentonite after sodiumization in step S3 is centrifuged, dehydrated, dried at 140-150℃, and crushed to 200-300 mesh to obtain the product.

[0026] The composite sodium agent in step S1 is a mixture of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide, and the mass of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide is 461.18 g, 92.24 g, 36.89 g, 9.22 g and 0.46 g, respectively.

[0027] The bentonite prepared by the above preparation method meets the high-end casting bentonite standard and is suitable for high-end application scenarios.

[0028] Embodiment 2

[0029] A method for producing sodium-based bentonite from calcium-based bentonite, comprising the following steps:

[0030] S1. Preliminary mixing: 10 kg of calcium-based bentonite is crushed to 90-110 mesh, and then mixed with 600 g of composite sodium agent;

[0031] S2. Mechanical shearing: the mixture obtained in step S1 is first treated at a speed of 2000 r / min for 15 min, and then treated at a speed of 3500 r / min for 10 min in a high-speed shearing machine;

[0032] S3. Sodiumization: the bentonite after mechanical shearing in step S2 is subjected to microwave action for 5 min at a frequency of 2.45 GHz and a power of 500 W, and then subjected to ultrasonic action for 10 min at a frequency of 20 kHz and a power of 100 W, and then 12 kg of deionized water is added, and stirred and reacted at a temperature of 70-80°C for 1.6 h;

[0033] S4. Drying: the bentonite after sodiumization in step S3 is centrifuged, dehydrated, dried at 140-150°C, and crushed to 200-300 mesh to obtain the product.

[0034] The composite sodiumizing agent in step S1 is a mixture of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide, and the mass of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide is 461.18 g, 92.24 g, 36.89 g, 9.22 g and 0.46 g respectively.

[0035] The bentonite prepared by the above preparation method meets the high-end casting bentonite standard and is suitable for high-end application scenarios.

[0036] Example 3

[0037] A method for producing sodium-based bentonite from calcium-based bentonite, comprising the following steps:

[0038] S1. Preliminary mixing: 10 kg of calcium-based bentonite is crushed to 90-110 mesh, and then mixed with 600 g of composite sodiumizing agent;

[0039] S2. Mechanical shearing: the mixture obtained in step S1 is first treated in a high-speed shearing machine at a speed of 2000 r / min for 15 min, and then the speed is increased to 3500 r / min for 10 min;

[0040] S3. Sodiumization: the bentonite after mechanical shearing in step S2 is subjected to microwave action for 5 min at a frequency of 2.45 GHz and a power of 500 W, and then subjected to ultrasonic action for 10 min at a frequency of 20 kHz and a power of 100 W, and then 12 kg of deionized water is added, and stirred and reacted at a temperature of 70-80°C for 1.6 h, and 72 g of trisodium citrate is added to the deionized water;

[0041] S4. Drying: the bentonite after sodiumization in step S3 is centrifuged, dehydrated, dried at 140-150°C, and crushed to 200-300 mesh to obtain the product.

[0042] The composite sodiumizing agent in step S1 is a mixture of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide, and the mass of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide is 461.18 g, 92.24 g, 36.89 g, 9.22 g and 0.46 g respectively.

[0043] The bentonite prepared by the preparation method meets the high-end casting bentonite standard and is suitable for high-end application scenarios.

[0044] Example 4

[0045] A method for producing sodium-based bentonite from calcium-based bentonite, comprising the following steps:

[0046] S1. Preliminary mixing: 10 kg of calcium-based bentonite is crushed to 90-110 mesh, and then mixed with 600 g of composite sodium agent;

[0047] S2. Mechanical shearing: the mixture obtained in step S1 is first treated in a high-speed shearing machine at a speed of 2000 r / min for 15 min, and then the speed is increased to 3500 r / min for 10 min;

[0048] S3. Sodiumization: the bentonite after mechanical shearing in step S2 is subjected to microwave action at a frequency of 2.45 GHz and a power of 500 W for 5 min, and then subjected to ultrasonic action at a frequency of 20 kHz and a power of 100 W for 10 min, and then 12 kg of deionized water is added, and stirred and reacted at a temperature of 70-80 ℃ for 1.6 h, 36 g of polyaspartic acid sodium and 36 g of chitosan quaternary ammonium salt are added to the deionized water;

[0049] S4. Drying: the sodiumized bentonite in step S3 is centrifuged, dried at 140-150 ℃, and crushed to 200-300 mesh to obtain the product.

[0050] The composite sodium agent in step S1 is a mixture of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide, and the mass of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheet and lanthanum oxide is 461.18 g, 92.24 g, 36.89 g, 9.22 g and 0.46 g, respectively.

[0051] The bentonite prepared by the preparation method meets the high-end casting bentonite standard and is suitable for high-end application scenarios.

[0052] Comparative Example 1

[0053] In Example 1, the components of montmorillonite nanosheet 9.22 g and lanthanum oxide 0.46 g are removed, and the others are the same as Example 1, which will not be repeated.

[0054] Comparative Example 2

[0055] In Example 1, the component of sodium silicate 36.89 g is removed, and the others are the same as Example 1, which will not be repeated.

[0056] The sodium-based bentonite prepared in the above examples and comparative examples is subjected to performance test, and the results are shown in Table 1.

[0057] Table 1

[0058]

[0059] As can be seen from the data in the above table, the data of Examples 1 to 3 show that the sodium bentonite prepared by the present invention has a swelling capacity greater than 50 mL / g, and Ca² + The replacement rate is greater than 97%, and the sodiumization time is less than 2 hours. The product performance can be improved by microwave light wave treatment and the addition of additives. The data of comparative example 1 show that montmorillonite nanosheets and lanthanum oxide can significantly improve Ca² + Replacement rate and sodium time, the data of comparative example 2 show that sodium silicate can increase Ca² to a certain extent + Replacement rate and sodiumization time.

Claims

1. A method for producing sodium bentonite from calcium bentonite, characterized in that: The following steps are involved: S1. Preliminary mixing: crush the calcium bentonite into 90-110 mesh, and then mix it with the composite sodium agent at a mass ratio of 1: (0.03-0.10); S2 mechanical shearing: The mixture obtained in step S1 was processed in a high-speed shearing machine at a speed of 2000~4000r / min for 10~40min; S3 sodium: the bentonite after mechanical shearing in step S2, add 1 to 1.5 times its mass of deionized water, stirring the reaction at a temperature of 60 to 80 ℃ for 1 to 2h; S4. Drying: The bentonite after sodiumization in step S3 is centrifuged and dehydrated, dried at 120-150°C, and crushed to 200-300 mesh to obtain the product.

2. The method for producing sodium bentonite from calcium bentonite according to claim 1, wherein: The composite sodium agent in step S1 is a mixture of sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheets and lanthanum oxide.

3. The method for producing sodium bentonite from calcium bentonite according to claim 2, wherein: The mass ratio of the sodium carbonate, sodium polyacrylate, sodium silicate, montmorillonite nanosheets and lanthanum oxide is 10:2:0.8:0.2:0.

01.

4. The method for producing sodium bentonite from calcium bentonite according to claim 1, wherein: The mechanical shearing process in step S2 is: firstly, the rotation speed is 2000 r / min for 15 minutes, and then the rotation speed is increased to 3500 r / min for 10 minutes.

5. The method for producing sodium bentonite from calcium bentonite according to claim 1, wherein: In step S3, 0.6 wt% of an auxiliary agent is added to the deionized water, wherein the auxiliary agent is trisodium citrate.

6. The method for producing sodium bentonite from calcium bentonite according to claim 1, wherein: In the step S3, 0.6 wt% of an auxiliary agent is added to the deionized water, wherein the auxiliary agent is a mixture of sodium polyaspartate and chitosan quaternary ammonium salt, and the mass ratio of sodium polyaspartate to chitosan quaternary ammonium salt is 1:

1.

7. The method for producing sodium bentonite from calcium bentonite according to claim 1, wherein: In step S3, before adding water, the mixture is first subjected to microwave treatment at a frequency of 2.45 GHz and a power of 500 W for 5 minutes, and then subjected to ultrasonic treatment at a frequency of 20 kHz and a power of 100 W for 10 minutes.

Images