阅读说明：本技术 一种酸性硅溶胶的制备方法及酸性硅溶胶 (Preparation method of acidic silica sol and acidic silica sol ) 是由 于明江 赵玉奇 王相明 苗建建 吴丹丹 李新波 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种酸性硅溶胶的制备方法及酸性硅溶胶,制备方法包括以下步骤：(1)制备活性硅酸溶液；(2)将纯水作为底水,加热,通入活性硅酸溶液和碱溶液,控制pH并保温,获得稀硅溶胶作为晶种；然后持续滴加活性硅酸溶液,经超滤浓缩,制得高浓度碱性硅溶胶；(3)将高浓度碱性硅溶胶加入酸性交换罐中进行交换,搅拌,获得酸性硅溶胶。本发明的制备方法制备的酸性硅溶胶粒径大、浓度高、均一性好,稳定性高,能够长时间存储。(The invention discloses a preparation method of acidic silica sol and the acidic silica sol, wherein the preparation method comprises the following steps: (1) preparing an active silicic acid solution; (2) heating pure water serving as bottom water, introducing an active silicic acid solution and an alkali solution, controlling the pH value and preserving the temperature to obtain diluted silica sol serving as seed crystals; then continuously dropwise adding an active silicic acid solution, and carrying out ultrafiltration concentration to prepare high-concentration alkaline silica sol; (3) and adding the high-concentration alkaline silica sol into an acid exchange tank for exchange, and stirring to obtain the acid silica sol. The acidic silica sol prepared by the preparation method has the advantages of large particle size, high concentration, good uniformity and high stability, and can be stored for a long time.)

1. A preparation method of acidic silica sol is characterized by comprising the following steps:

(1) preparing an active silicic acid solution;

(2) heating pure water serving as bottom water, introducing an active silicic acid solution and an alkali solution, controlling the pH value and preserving the temperature to obtain diluted silica sol serving as seed crystals; then continuously dropwise adding an active silicic acid solution, and carrying out ultrafiltration concentration to prepare high-concentration alkaline silica sol;

(3) and adding the high-concentration alkaline silica sol into an acid exchange tank for exchange, and stirring to obtain the acid silica sol.

2. The method according to claim 1, wherein in the step (3), the stirring speed is 180-220 rpm;

preferably, the rotation speed of the stirring is 200 rpm.

3. The method according to claim 1 or 2, wherein the pH of the acidic silica sol obtained in step (3) is 2.5 to 2.7.

4. The method for preparing an acidic silica sol according to any one of claims 1 to 3, wherein in the step (3), the cation exchange resin is added to the acidic exchange tank, and dilute hydrochloric acid is added for regeneration; then pure water is introduced to wash the hydrochloric acid, and the washing is repeated for a plurality of times;

preferably, stirring is carried out when pure water is introduced to wash the hydrochloric acid, the stirring speed is 160-200rpm, and the pure water is discharged after stirring for 5-10 min; the above process was repeated for a number of washes.

5. The method as claimed in claim 4, wherein the high concentration acidic silica sol is obtained by washing hydrochloric acid with pure water for several times, introducing exchange bottom water into the acidic exchange tank, stirring at 160-200rpm for 5-10min, sampling to detect that the pH of the exchange bottom water is not less than 3.0, draining the water from the acidic exchange tank, adding the high concentration alkaline silica sol prepared in step (2), and stirring.

6. The method for producing an acidic silica sol according to any one of claims 1 to 5, wherein the high-concentration basic silica sol obtained in the step (2) has a silica mass fraction of 41 to 45%.

7. The method for producing an acidic silica sol according to any one of claims 1 to 6, wherein the high-concentration acidic silica sol obtained in the step (3) has a silica mass fraction of 41 to 45%.

8. The process according to any one of claims 1 to 7, wherein in the step (2), pure water is used as a bottom water, the temperature is raised to 95 to 98 ℃, and 5 to 8m of pure water is added to the reaction system³Adding active silicic acid at 0.001-0.05m³Dropping inorganic base at a speed of/h, controlling the pH of the system to be between 9 and 10, and preserving heat for 1 to 5 hours after the feeding is finished.

9. The method for preparing acidic silica sol according to claim 8, wherein in the step (2), the volume of the bottom water is 20-30% of the feeding amount of the active silicic acid solution.

10. An acidic silica sol prepared by the method according to any one of claims 1 to 9, wherein the acidic silica sol has a pH of 2.5 to 2.7, a silica mass fraction of 41 to 45%, and an average silica particle diameter of 35 to 45 nm.

Technical Field

The invention belongs to the field of chemical industry, and particularly relates to a preparation method of acidic silica sol and the acidic silica sol.

Background

Silica sols are dispersions of nanoscale silica particles in water or a solvent. Due to SiO in the silica sol₂Contains a large amount of water and hydroxyl groups, so that the silica sol can also be expressed as mSiO₂.nH₂And O. There are different approaches to the preparation of silica sol, the most common methods being ion exchange, one-step hydrolysis of silica powder, silane hydrolysis, etc.

Silica sols are classified into alkaline silica sols and acidic silica sols, depending on the pH value of the silica sols. They are important fine chemicals with different important uses: for example, the alkaline silica sol is applied to the fields of precision casting, exterior wall coating and the like; the acidic silica sol is applied to the technologies of color kinescope, colloid lead-acid accumulator, electrostatic flocking, etc. Wherein, the stability of the alkaline silica sol is higher, and the room temperature storage is generally more than two years. The stability of the acidic silica sol is poor, the storage time at room temperature is generally 3-6 months or even shorter, and the low stability of the acidic silica sol limits the concentration of the acidic silica sol. The problem to be solved in the field is to search for a method for preparing the silica sol with large particle size, good stability and high concentration.

Chinese patent with application number CN201610324627.1 discloses an acidic silica sol and a preparation method thereof, wherein the preparation method comprises the following steps of 1) diluting water glass with deionized water and then sequentially passing through a strong acid cation exchange column and a strong base anion exchange column; 2) then adjusting the pH of the solution to be more than 7.0 by using alkali liquor to prepare an active silicic acid solution; 3) taking a certain volume of the active silicic acid solution in a reaction container, and heating for a certain time to prepare seed crystals; 4) continuously dripping an active silicic acid solution into the seed crystal by adopting a constant liquid level heating concentration method to prepare alkaline silica sol; 5) and (3) passing the alkaline silica sol through a strong-acid cation exchange column to prepare the acidic silica sol. According to the technical scheme, the alkaline silica sol is made into the acidic silica sol through a static strong acid type cation exchange column, when the cation exchange column is used initially and loses effectiveness quickly, the pH value and the property of the obtained acidic silica sol product have certain difference, so that the quality of the same batch of products has difference, the silica sol is not uniform, and the stability is influenced. In addition, when the ion exchange column is regenerated, the ion exchange column needs to be manually raised, and a large amount of resources and labor are consumed.

The present invention has been made in view of this situation.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a preparation method of acidic silica sol. The acidic silica sol prepared by the preparation method has the advantages of good uniformity, good stability, high concentration and large particle size.

In order to solve the technical problems, the invention adopts the technical scheme that:

the first purpose of the invention is to provide a preparation method of acidic silica sol, which comprises the following steps:

(1) preparing an active silicic acid solution;

(2) heating pure water serving as bottom water, introducing an active silicic acid solution and an alkali solution, controlling the pH value and preserving the temperature to obtain diluted silica sol serving as seed crystals; then continuously dropwise adding an active silicic acid solution, and carrying out ultrafiltration concentration to prepare high-concentration alkaline silica sol;

(3) and adding the high-concentration alkaline silica sol into an acid exchange tank for exchange, and stirring to obtain the acid silica sol.

The invention prepares and obtains high-concentration large-particle-size high-quality alkaline silica sol by controlling process conditions, and then exchanges the high-concentration alkaline silica sol by stirring in an acid exchange tank, so that the acid silica sol with uniform quality, pH controlled between 2.5 and 2.7 and good stability can be prepared.

In a further embodiment, the pH of the acidic silica sol obtained in step (3) is from 2.5 to 2.7.

The main factors affecting the stability of the colloid are pH, particle size distribution, electrolyte, etc., in addition to charge distribution, SiO₂Concentration is also an important factor affecting colloidal stability. Wherein, the pH value has direct relation with the stability of the high-purity silica sol. When the pH value of the high-purity silica sol is between 2 and 10, the zeta potential of the particles is a negative value; when the pH value is below 2, the zeta potential of the particles is a positive value; at a pH value of 2 is "0 "potential. The pH value is in the range of 8.5-10, and is a stable area; when the pH value is more than 10, the silica sol particles are dissolved into silicate; a metastable zone is below pH 4; the pH value was 2, the highest metastable state was obtained. According to the characteristics of the prepared high-purity silica sol, the pH value of the silica sol is adjusted to be about 2.5, the sol can be kept in a high-dielectric-stability state, and the silica sol can be stored for a long time at room temperature without gelation. In the prior art, when the acidic silica sol is prepared by adopting an ion exchange column, the pH of an acidic gel finished product obtained at the beginning is 2.5, the pH of the acidic gel finished product is 3.0 when the acidic gel finished product loses efficacy quickly, and the pH difference between the front and the rear is large, so that the quality of the same batch of products is different, the quality is not uniform, and the stability is influenced. In the invention, a stirring exchange mode is adopted in the acid exchange tank, and the pH of the acidic silica sol product obtained in each tank can be controlled to be between 2.5 and 2.7, more preferably between 2.5 and 2.6 by controlling parameter conditions such as stirring speed, stirring time, adding speed, reaction time and the like, so that the pH difference of the obtained product is very small, the uniformity is good, and the stability is improved.

The alkaline solution used in the invention can be inorganic alkali such as sodium hydroxide, and the mass concentration of the sodium hydroxide is 5-32%.

In the step (3), the rotation speed of stirring is 180-220rpm when the exchange is performed;

preferably, the rotation speed of the stirring is 200 rpm.

During the exchange process, the stirring speed influences the quality of the acidic silica sol generated by the exchange. If the stirring speed is too low, the stirring is not uniform easily, and the uniformity of the obtained silica sol product is influenced; if the stirring speed is too high, the generated acting force is too high, and the viscosity of the sol is influenced. When the stirring speed is controlled at 180-220rpm, the effect is best, the stirring effect can be ensured, and uniform acidic silica sol with the pH value of 2.5-2.7 can be obtained.

In the step (3), adding cation exchange resin into an acid exchange tank, and firstly adding dilute hydrochloric acid for regeneration; then pure water is introduced to wash the hydrochloric acid, and the washing is repeated for a plurality of times;

preferably, stirring is carried out when pure water is introduced to wash the hydrochloric acid, the stirring speed is 160-200rpm, and the pure water is discharged after stirring for 5-10 min; the above process was repeated for a number of washes.

The cation exchange resin is added into the acid exchange tank, and the cation exchange resin can be gel type strong acid styrene ion exchange resin (001 × 7 type cation exchange resin) or other suitable ion exchange resin.

Adding dilute hydrochloric acid into cation exchange resin in an acid exchange tank for regeneration, wherein the volume ratio of the cation exchange resin to the dilute hydrochloric acid is 3: 2, the regeneration time is not less than 25 min. Then opening a valve at the bottom of the exchange tank to drain the hydrochloric acid, closing the valve, starting to wash the hydrochloric acid by pure water, and repeating the washing for at least four times. When the pure water is adopted to wash the hydrochloric acid each time, the stirring is started, so that the pure water can be fully contacted with the resin, chloride ions are taken away, and the stability of the product is ensured.

And (3) further adopting the scheme that after the hydrochloric acid is washed by pure water for multiple times, exchange bottom water is introduced into the acid exchange tank, stirring is started, the stirring speed is 160-200rpm, after stirring is carried out for 5-10min, sampling is carried out, the pH value of the exchange bottom water is detected to be not less than 3.0, the water in the acid exchange tank is drained, the high-concentration alkaline silica sol prepared in the step (2) is added, and stirring is carried out, so that the high-concentration acidic silica sol is obtained.

In the scheme, the exchange bottom water is pure water.

In a further scheme, the mass fraction of the silicon dioxide of the high-concentration alkaline silica sol obtained in the step (2) is 41-45%.

In a further scheme, the mass fraction of the silica in the acidic silica sol obtained in the step (3) is 41-45%.

In the further scheme, in the step (2), pure water is used as bottom water, the temperature is heated to 95-98 ℃, and 5-8m of pure water is added into a reaction system³Adding active silicic acid at 0.001-0.05m³Dropping inorganic base at a speed of/h, controlling the pH of the system to be 9-10, and preserving heat for 2h after feeding is finished to obtain diluted silica sol as seed crystal.

In the invention, the diluted silica sol is obtained as the seed crystal by controlling the adding speed of the active silicic acid and the inorganic alkali, the pH of the system between 9 and 10 and the heat preservation time. The growth of particles on the basis of seed crystals to form silica sols is a very critical process of reaction. And performing long-particle-size operation in the same manner as the above steps, repeating the steps, and continuously growing the particle size of the diluted silica sol to obtain the diluted silica sol with the particle size of 35nm-50nm, and performing ultrafiltration and concentration on the diluted silica sol to obtain the high-concentration acidic raw material gel with the mass fraction of the silicon dioxide of 41-45%.

In a further scheme, in the step (2), the volume of the bottom water is 20-30% of the feeding amount of the active silicic acid solution.

In a further embodiment, the step of preparing the active silicic acid solution specifically comprises:

(1) the resin is regenerated by using 5-15% of dilute hydrochloric acid: adding dilute hydrochloric acid into the cation exchange resin for regeneration, wherein the volume ratio of the cation exchange resin to the dilute hydrochloric acid is 3: 2, the regeneration time is not less than 25 min. Then opening a valve at the bottom of the exchange tank to drain the hydrochloric acid, closing the valve, starting to wash the hydrochloric acid by pure water, and repeating the washing for at least four times. When the pure water is adopted to wash the hydrochloric acid each time, the stirring is started, so that the pure water can be fully contacted with the resin, chloride ions are taken away, and the stability of the product is ensured.

After the hydrochloric acid is washed by pure water for many times, introducing exchange bottom water into the acid exchange tank, starting stirring at the stirring speed of 160-200rpm, sampling and detecting that the pH value of the exchange bottom water is not lower than 3.0 after stirring for 5-10min, draining the water in the acid exchange tank,

(2) washing hydrochloric acid with pure water until pH of water is above 3.0, adding exchange bottom water, stirring, adding 14-20% diluted sodium silicate into the exchange tank at a certain flow rate, and stirring for 5-10min after feeding is finished to obtain active silicic acid.

A second object of the present invention is to provide an acidic silica sol prepared by any one of the above-mentioned preparation methods, wherein the acidic silica sol has a pH of 2.5 to 2.7, a silica mass fraction of 41 to 45%, and an average silica particle diameter of 35 to 45 nm.

After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. the invention prepares and obtains high-concentration large-particle-size high-quality alkaline silica sol by controlling process conditions, and then exchanges the high-concentration alkaline silica sol by stirring in an acid exchange tank, so that the acid silica sol with uniform quality, pH controlled between 2.5 and 2.7 and good stability can be prepared.

In the prior art, when the acidic silica sol is prepared by adopting an ion exchange column, the pH of an acidic gel finished product obtained at the beginning is 2.5, the pH of the acidic gel finished product is 3.0 when the acidic gel finished product loses efficacy quickly, and the pH difference between the front and the rear is large, so that the quality of the same batch of products is different, the quality is not uniform, and the stability is influenced. In the invention, a stirring exchange mode is adopted in the acid exchange tank, and the pH of the acidic silica sol product obtained in each tank can be controlled to be between 2.5 and 2.7, more preferably between 2.5 and 2.6 by controlling parameter conditions such as stirring speed, stirring time, adding speed, reaction time and the like, so that the pH difference of the obtained product is very small, the uniformity is good, and the stability is improved.

2. The invention controls the stirring speed during exchange to be 180-220rpm, and the effect is best, and the uniform acidic silica sol with the pH value of 2.5-2.7 is obtained. Particularly, pure water is introduced to wash hydrochloric acid and exchange bottom water, the stirring speed is controlled to be 160rpm, the stirring speed is controlled to be 200rpm when alkaline silica sol is added for exchange, the effect is best, and the stability of the acidic silica sol is best.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below, and the following embodiments are used for illustrating the present invention and are not used for limiting the scope of the present invention.

Example one

(1) Preparing an active silicic acid solution; adding 10m into the exchange tank³And dilute hydrochloric acid with the mass fraction of 5 percent is regenerated for 30min, then the dilute hydrochloric acid is discharged, and 10m of dilute hydrochloric acid is added each time³Washing hydrochloric acid with pure water, repeating for 4 times, and adding 10m into the exchange tank³Taking pure water as exchange bottom water, stirring for 5min, and stirring at a speed of 5m³Adding 18% by mass of the mixture into the exchange tank at a speed of/hLiquid sodium silicate, add 5m in total³And (3) diluting sodium silicate, and stirring for 10min after the addition of the sodium silicate is finished to obtain active silicic acid for later use.

(2) Pure water as bottom water, stirring and heating to 98 deg.C, adding 6m³H adding active silicic acid, and adding 0.03m of active silicic acid into the system³Dropping inorganic base at a speed of/h, keeping the pH of the system between 9 and 10, keeping the temperature for 2h after the feeding is finished, wherein the volume of bottom water accounts for 25 percent of the feeding amount of the active silicic acid, and obtaining diluted silica sol as seed crystal;

continuing to use the prepared diluted silica sol as a seed crystal, continuing to introduce active silicic acid for long-particle-size operation, repeating the steps, and continuously growing the particle size of the diluted silica sol to obtain diluted silica sol with the particle size of 35nm, and performing ultrafiltration and concentration on the diluted silica sol to obtain high-concentration acidic raw material gel with the mass fraction of silicon dioxide of 43 percent, namely high-concentration alkaline silica sol;

(3) adding 3m into an acid exchange tank³001 x 7 type cation exchange resin, adding 2m³Regenerating dilute hydrochloric acid for not less than 25min, opening a valve at the bottom of the exchange tank to drain hydrochloric acid, closing the valve, washing hydrochloric acid with pure water, and adding pure water 2m each time³And starting stirring at the rotating speed of 180rpm, draining pure water after stirring for 10min each time, and closing a valve. After washing was repeated four times, exchange bottom water (pure water) 1m was added³After stirring at the rotating speed of 180rpm for 10min, sampling and detecting the pH of the exchange bottom water, wherein the pH of the bottom water is required to be not lower than 3.0, opening a bottom valve to completely discharge pure water after the detection is qualified, and closing the bottom valve. Then start at 20m³Slowly adding 4m at a speed of/h³And (3) continuously stirring the acidic raw material gel for 10min at the rotating speed of 220rpm after the addition of the acidic raw material gel is finished, so as to obtain the finished product of the acidic silica sol.

The pH value of the obtained acidic silica sol was 2.7, the mass fraction of silica was 43%, and the average particle diameter of silica was 35 nm.

Example two

(1) Preparation of an active silicic acid solution: adding 10m into the exchange tank³And dilute hydrochloric acid with the mass fraction of 5 percent is regenerated for 30min, then the dilute hydrochloric acid is discharged, and 10m of dilute hydrochloric acid is added each time³Washing with pure water, repeating for 4 timesThen adding 10m into the exchange tank³Taking pure water as exchange bottom water, stirring for 5min, and stirring at a speed of 5m³Adding 18 percent liquid sodium silicate into the exchange tank at a speed of/h, and adding 5m in total³And (3) diluting sodium silicate, and stirring for 10min after the addition of the sodium silicate is finished to obtain active silicic acid for later use.

(2) Pure water as bottom water, stirring and heating to 95 deg.C, adding 5m³Adding active silicic acid, and adding into the system at 0.02m³Dropping inorganic base at a speed of/h, keeping the pH of the system between 9 and 10, keeping the temperature for 1h after the feeding is finished, and obtaining diluted silica sol as seed crystal, wherein the volume of bottom water accounts for 20 percent of the feeding amount of the active silicic acid;

continuing to use the prepared diluted silica sol as a seed crystal, continuing to introduce active silicic acid for long-particle-size operation, repeating the steps, and continuously growing the particle size of the diluted silica sol to obtain diluted silica sol with the particle size of 40nm, and performing ultrafiltration and concentration on the diluted silica sol to obtain high-concentration acidic raw material gel with the mass fraction of silicon dioxide of 41 percent, namely high-concentration alkaline silica sol;

(3) adding 3m into an acid exchange tank³001 x 7 type cation exchange resin, adding 2m³Regenerating dilute hydrochloric acid for not less than 25min, opening a valve at the bottom of the exchange tank to drain hydrochloric acid, closing the valve, washing hydrochloric acid with pure water, and adding pure water 2m each time³And (4) starting stirring, wherein the rotating speed of the stirrer is 200rpm, discharging the pure water after stirring for 10min each time, and closing a valve. After repeating the step for four times, adding exchange bottom water 1m³Starting stirring, stirring at 200rpm for 10min, sampling, detecting and exchanging bottom water pH, requiring the bottom water pH not to be lower than 3.0, opening a bottom valve to clean pure water after qualified detection, closing the bottom valve, and starting to use 20m³Slowly adding 4m at a speed of/h³And (3) continuously stirring the acidic raw material gel for 2min at the rotating speed of 180rpm after the addition of the acidic raw material gel is finished, thus obtaining the finished product of the acidic silica sol.

The pH value of the obtained acidic silica sol was 2.6, the mass fraction of silica was 41%, and the average particle diameter of silica was 45 nm.

EXAMPLE III

(1) Preparation of active silicic acid solutionLiquid; adding 10m into the exchange tank³And dilute hydrochloric acid with the mass fraction of 5 percent is regenerated for 30min, then the dilute hydrochloric acid is discharged, and 10m of dilute hydrochloric acid is added each time³Washing hydrochloric acid with pure water, repeating for 4 times, and adding 10m into the exchange tank³Taking pure water as exchange bottom water, stirring for 5min, and stirring at a speed of 5m³Adding 18 percent liquid sodium silicate into the exchange tank at a speed of/h, and adding 5m in total³And (3) diluting sodium silicate, and stirring for 10min after the addition of the sodium silicate is finished to obtain active silicic acid for later use.

(2) Pure water as bottom water, stirring and heating to 98 deg.C, adding 8m³Adding active silicic acid, and adding into the system at 0.05m³Dropping inorganic base at a speed of/h, keeping the pH of the system between 9 and 10, keeping the temperature for 5h after the feeding is finished, wherein the volume of bottom water accounts for 30 percent of the feeding amount of the active silicic acid, and obtaining diluted silica sol as seed crystal;

continuing to use the prepared diluted silica sol as a seed crystal, continuing to introduce active silicic acid for long-particle-size operation, repeating the steps, and continuously growing the particle size of the diluted silica sol to obtain diluted silica sol with the particle size of 40nm, and performing ultrafiltration and concentration on the diluted silica sol to obtain high-concentration acidic raw material gel with the mass fraction of silicon dioxide of 45%, namely high-concentration alkaline silica sol;

(3) adding 3m into an acid exchange tank³001 x 7 type cation exchange resin, adding 2m³Regenerating dilute hydrochloric acid for not less than 25min, opening a valve at the bottom of the exchange tank to drain hydrochloric acid, closing the valve, washing hydrochloric acid with pure water, and adding pure water 2m each time³And (4) starting stirring, wherein the rotating speed of the stirrer is 160rpm, discharging the pure water after stirring for 10min each time, and closing a valve. After repeating the step for four times, adding exchange bottom water 1m³Starting stirring, wherein the rotating speed of a stirrer is 160rpm, sampling and detecting the pH of the exchanged bottom water after 10min, wherein the pH of the bottom water is required to be not less than 3.0, opening a bottom valve to completely discharge pure water after the detection is qualified, closing the bottom valve, and starting to discharge the pure water by 20m³Slowly adding 4m at a speed of/h³And (3) continuously stirring the acidic raw material gel for 2min at the rotating speed of 200rpm after the addition of the acidic raw material gel is finished, thus obtaining the finished product of the acidic silica sol.

The pH value of the obtained acidic silica sol is 2.5, the mass fraction of the silica is 45 percent, and the average particle size of the silica is 40 nm.

Comparative example 1

The comparative example differs from the first example in that: the method for passing the high-concentration alkaline silica sol obtained in the step (3) through a cation exchange column is specifically as follows:

(1) adding evaporated and cooled alkaline silica sol into a static strong acid type cation exchange column, and controlling the liquid level to be 5cm higher than the resin surface.

(2) After the liquid at the bottom of the column flows out, the pH value is tested by using pH test paper, when the pH value meets the process requirement, the density of the discharged liquid is measured, and when the density is also in a specified range, the exchange liquid is filled into a barrel.

During the exchange process, the pH value of the effluent is detected by a pH test paper at any time, and when the pH value is in a range of 3.5-4.0, the column is disabled and is ready for treatment.

Regeneration treatment of spent resins

(1) Process conditions

End point of water washing after exchange: the PH value is 6.5-7.0;

end point of washing after acid treatment: PH is 2.5-3.5;

the acid treatment time is more than or equal to 1 hour;

(2) operating procedures

After the used dead cation resin is positively washed by tap water for 5-10min, the resin is evenly blasted by vacuum and back washed until the pH value is 6.5-7.0. Discharging water in the column, pressing dilute hydrochloric acid for regeneration, keeping the liquid level 5cm higher than the resin surface, uniformly blowing the resin by vacuum when the pH value of a water outlet is detected to be 1-2, pressing acid once if necessary, uniformly blowing the resin by vacuum, and standing and soaking for 1 hour or more. After the acid is completely soaked, the acid is discharged, the water is positively washed for 5 to 10 minutes by tap water, then the water is uniformly blown by vacuum and back-washed until the pH value is between 2.5 and 3.5, and the water is uniformly blown and exchanged.

Test example 1 stability examination

The acidic silica sol prepared in examples 1-3 and comparative example 1 was placed at 0-40 deg.C, and the test example was placed at 25 + -2 deg.C, and samples were taken at month 6, month 12, and month 24 after lofting to test the parameters of each product, and the results are shown in Table 1.

TABLE 1

As can be seen from Table 1 above, the acidic silica sols obtained in examples 1 to 3, which were subjected to agitation exchange in an acidic exchange tank, had better stability than those obtained in comparative example 1, which was subjected to ion column chromatography.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.