JP5213515B2 - Method for producing iron-silica water treatment flocculant - Google Patents

Description

  The present invention relates to a novel method for producing an iron-silica water treatment flocculant. More specifically, the present invention relates to a method capable of easily producing an iron-silica water treatment flocculant having excellent storage stability even at a high iron concentration.

  A water treatment method in which a flocculant is injected into the water or wastewater to agglomerate and precipitate to remove the suspended solids and other impurities from various water and wastewater. As the flocculant for this purpose, aluminum sulfate, polyaluminum chloride, ferric chloride and the like are used.

  Among the above flocculants, aluminum sulfate or polyaluminum chloride is widely used. When these flocculants are used, the amount of flocculant added must be increased when the water temperature decreases or the amount of organic matter in the water, such as algae, increases. However, since aluminum is an amphoteric metal, it becomes soluble aluminum, There is a problem that it remains in the treated water. In addition, the aluminum-based flocculant has a drawback in that the amount of the aluminum-based flocculant increases because the aggregating property decreases at a low water temperature.

  In order to solve the above problems, an iron-silica water treatment flocculant in which an iron salt is added to polymerized silicic acid (silica sol) has recently attracted attention because of its high flocculation performance and the ability to reduce the generated agglomerates to the soil. ing.

Such an iron-silica water treatment flocculant is obtained by adding an aqueous silicate solution to an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid in a container to obtain a silica sol having a SiO ₂ concentration of about 1 to 6% by mass, and then the silicic acid solution. Can be obtained by advancing polymerization while stirring for several hours, and then adding an iron salt thereto (see Patent Documents 1 and 2).

  However, in order to obtain a flocculant having good performance by the methods described in Patent Documents 1 and 2, the polymerized silicic acid (silica sol) must be heated to about 60 ° C. and polymerized while stirring for several hours. For this reason, an apparatus for heating is required, and a long time is required for production, which causes a problem in industrial implementation.

  On the other hand, a method for producing an iron-silica water treatment flocculant by an industrially simple method has also been proposed. For example, a method for producing an iron-silica water treatment flocculant that does not require a polymerization tank is proposed in which a silica sol is polymerized simultaneously with the reaction between iron and silica by adding an aqueous silicate solution directly to an aqueous iron chloride solution. (See Patent Document 3).

However, according to this method, since the aqueous silicate solution is added to the aqueous iron chloride solution, the concentration of iron chloride, silica, etc. is constantly changing. Stirring or a long reaction time may be required. As a result of a further trial by the present inventors, when an SiO ₂ concentration of the silicate aqueous solution to be added is 76 g / L or more, 1 L of sodium silicate is added in order not to gel the silica sol during the reaction. It took more than an hour. Moreover, even if the aqueous silicate solution is gradually added, there is a case in which the gelation trouble of silica is caused by the state of stirring, and stable production cannot be performed, and there is room for improvement.

Japanese Examined Patent Publication No. 4-75796 Japanese Patent No. 2732067 Japanese Patent No. 3700892 JP 2003-38908 A

  Accordingly, an object of the present invention is to provide a method for producing an iron-silica water treatment flocculant which simply shows high agglomeration performance in a short time. Another object of the present invention is to provide a method for producing an iron-silica water treatment flocculant having a high iron concentration and excellent storage stability in the above production method.

  The present inventors diligently studied to solve the above problems. As a result, in the method for producing an iron-silica water treatment flocculant using a silicate aqueous solution and a ferric salt aqueous solution as raw materials, the total amount of the silicate aqueous solution used for the production of the water treatment flocculant Then, at least a part of the ferric salt aqueous solution is collided and mixed in advance, and the resultant reaction liquid, or the ferric salt aqueous solution is further added to the reaction liquid in a conventional mixing method, for example, in a conventional container. It is possible to stably obtain an iron-silica water treatment flocculant that maintains high agglomeration performance in a short time without gelation trouble of the silica even when performing an operation of mixing by stirring and mixing. The headline and the present invention were completed.

That is, the present invention provides an aqueous solution of silicate used for the production of the iron-silica water treatment flocculant when the iron-silica water treatment flocculant is produced by the reaction of the silicate aqueous solution and the ferric salt aqueous solution. look including the total amount and impingement mixing step of impingement mixing in a tubular reactor and at least a portion of the ferric salt solution, and the reactor of the so two solutions collide with either 5 m / sec or faster It is a manufacturing method of the iron-silica water treatment flocculant characterized by supplying to a raw material supply pipe .

  Moreover, this invention confirmed the preferable minimum amount of the ferric-salt aqueous solution made to collision-mix with respect to silicate aqueous solution in the said collision mixing process.

  That is, according to the present invention, in the collision mixing step, the mixing amount of the ferric salt aqueous solution to be collision mixed is the elemental silicon in the total amount of the silicate aqueous solution used for the production of the iron-silica water treatment flocculant ( The method for producing an iron-silica water treatment flocculant according to claim 1, wherein the amount of iron element (Fe) is 0.5 times mol or more with respect to (Si).

Furthermore, as a result of examining conditions with higher storage stability for the obtained iron-silica water treatment flocculant using the above method, the following ranges are effective for SiO ₂ concentration, iron concentration and pH. I found out.

That is, according to the present invention, the iron-silica water treatment flocculant has a pH of 0.3 to 1.5, an iron element concentration (Fe) of 20 g / L to 120 g / L, and a SiO ₂ concentration of 10 g / L to A method for producing the iron-silica water treatment flocculant, which is 50 g / L and has a Si / Fe molar ratio of 1 or less, is also provided.

  Furthermore, in the method for producing the iron-silica water treatment flocculant of the present invention, the following aspect is included as an aspect of adjusting the obtained iron-silica water treatment flocculant to the above conditions.

  (1) In the collision mixing step, the total amount of the silicate aqueous solution to be used and a part of the ferric salt aqueous solution are collided and mixed to obtain a partial mixed solution, and the remaining ferric salt aqueous solution is added to the partial mixed solution. The aspect which obtains the target iron-silica water treatment flocculent by mixing by arbitrary methods.

  (2) The aspect which obtains the target iron-silica water treatment flocculant by carrying out collision mixing of the whole quantity of the silicate aqueous solution to be used, and the whole quantity of ferric salt aqueous solution in a collision mixing process.

  (3) In the above-described aspects (1) and (2), the target iron-silica water treatment flocculant is obtained by adjusting the pH by adding a mineral acid in the collision mixing step.

  (4) A mode in which, in (1) and (2) above, the target iron-silica water treatment flocculant is obtained by adjusting the pH by adding a mineral acid after collision mixing.

  According to the present invention, by the collision step, the total amount of the silicate aqueous solution used for the production of the iron-silica water treatment flocculant and at least a part of the ferric salt aqueous solution are collided and mixed, so that the aggregation performance is improved. A high iron-silica water treatment flocculant can be produced stably in a short time.

  In particular, in the above method, the pH of the obtained iron-silica water treatment flocculant, the iron and silicon concentrations, and the molar ratio between the iron and silicon are produced in a specific range, thereby ensuring long-term storage stability. Can be obtained.

In the present invention, the silicate used as a raw material is not particularly limited as long as it can be used for an ordinary silica sol and iron-silica water treatment flocculant. Acid soda, potassium silicate and the like can be used. Among these, it is preferable to use sodium silicate in consideration of the cost of the raw materials. When using sodium silicate, the molar ratio of SiO ₂ and Na ₂ O is not particularly limited, but a molar ratio of 2.5 to 4.0 is preferable.

In the present invention, the concentration of the aqueous solution containing the silicate is the pH of the aqueous ferric salt solution (or the aqueous solution containing mineral acid), the concentration of iron or the like, and the desired iron-silica water. the pH of the treatment coagulant, iron, but do it appropriately determined depending on the silica concentration, the iron by impingement mixing detailed below - to produce the silica water treatment coagulant, SiO ₂ concentration of 20 g / • L ^ It is preferable to use the one of 130 g / L. That is, by satisfying this range, an iron-silica water treatment flocculant having a high concentration in a short period of time, without generating a gelled product instantly and having excellent cohesiveness, and excellent storage stability. An iron-silica water treatment flocculant can also be easily produced.

In particular, according to the present invention, as described later, it was difficult to use a conventional manufacturing method in which an aqueous silicate solution was added while stirring a ferric salt solution. For example, the SiO ₂ concentration was 76 g / L or more. A silicate aqueous solution can also be used as a raw material. Therefore, this invention can manufacture a high concentration iron-silica water treatment flocculant in a short time. Therefore, a high concentration iron-silica water treatment flocculant can improve production efficiency and is advantageous in terms of storage and transportation. In use, it can be diluted to a required concentration, and the aggregation ability can be adjusted depending on the concentration, and its industrial utility value is extremely high.

  In the present invention, the ferric salt as the other raw material is not particularly limited as long as it can be used for a normal iron-silica water treatment flocculant, and ferric chloride, ferric sulfate, Ferric nitrate or the like can be used.

  In the present invention, the iron concentration in the aqueous ferric salt solution is not particularly limited, and may be determined as appropriate according to the iron concentration of the desired iron-silica water treatment flocculant. The concentration of ferric chloride in the aqueous ferric salt solution suitably employed in the present invention is preferably 180 g / L to 600 g / L.

  A feature of the present invention is that in the method for producing an iron-silica water treatment flocculant using a silicate aqueous solution and a ferric salt aqueous solution as raw materials, the silicate aqueous solution used for producing the water treatment flocculant There is a collision mixing step in which at least a part of the ferric salt aqueous solution is subjected to collision mixing with respect to the total amount.

  In the reaction between the silicate aqueous solution and the ferric salt aqueous solution, the step of collision mixing is employed for the first time in the present invention. This makes it possible to stabilize the iron-silica water treatment flocculant that maintains high agglomeration performance in a short time without the gelation trouble of silica that occurs in the conventional production method of stirring and mixing these aqueous solutions in the reaction vessel. Can be obtained.

  Here, it is important that the total amount of the silicate aqueous solution is reacted with the ferric salt aqueous solution by collision mixing. That is, when the silicate aqueous solution collides with the ferric salt aqueous solution, the reaction with the ferric salt aqueous solution changes the silica component in the silicate aqueous solution into a form in which gelation is difficult to occur. It is presumed that the subsequent generation of gel due to the reaction with the ferric salt aqueous solution is prevented.

  Accordingly, in the present invention, the amount of the ferric salt aqueous solution to be reacted with the total amount of the silicate aqueous solution by collision mixing may be a part or the total amount.

  In the collision mixing step, when a part of the ferric salt aqueous solution is collided with the silicate aqueous solution, the amount of the ferric salt aqueous solution to be collided is determined by the amount of silica used in the production of the iron-silica water treatment flocculant. It is preferable that the amount of iron element (Fe) is 0.5 times mol or more, particularly 0.8 to 5.0 times mol with respect to silicon element (Si) in the total amount of the acid salt aqueous solution.

  In the present invention, the collision mixing is a reaction in which the aqueous solution of ferric salt containing the above raw material and the aqueous solution of silicate collide with each other and are mixed at the same time. Specifically, a tubular reactor (Y-tube type, T-tube type reactor, etc.) in which two raw material supply pipes merge and are connected to one discharge pipe at the confluence of the raw material supply pipes By using this, both raw material aqueous solutions can be collision-mixed at the above-mentioned junction. Among these tubular reactors, in consideration of stability such as discharge, it is preferable to use a Y-shaped reactor, for example, a reactor described in JP-A No. 2003-221222. FIG. 1 shows an example of a Y-tube reactor that can be used in the present invention.

  In the Y-tube reactor shown in FIG. 1, a throttle is provided in the middle of each raw material supply pipe. By appropriately adjusting the diameter of the throttle portion and the amount of the raw material aqueous solution supplied from the pump, it is possible to set the collision speed during the collision mixing.

  In the Y-tube reactor, the angle formed by the two raw material supply pipes is 30 to 180 degrees, preferably 45 to 150 degrees, and more preferably 60 to 120 degrees.

  When such an apparatus is used, the raw materials are so arranged that both aqueous solutions collide at a speed of 5 m / sec or more, preferably 7 m / sec or more, more preferably 10 m / sec or more in the reaction section serving as the merging section. It is preferable to supply both aqueous solutions to the supply pipe 4. The upper limit of the supply speed is not particularly limited, but the effect tends to reach its peak even if the supply speed is increased to about 20 m / second or more.

  The reactant is preferably discharged from the discharge pipe 6 at a speed of 1 m / second or more, preferably 1.3 m / second or more, more preferably 1.5 m / second or more. If the discharge pipe is made thinner, the discharge speed can be increased. On the other hand, if the discharge pipe is made thicker, the discharge speed becomes slower.

  A preferred embodiment using the Y-tube reactor will be described with reference to FIG.

  First, a ferrous salt aqueous solution storage tank 1, a silicate aqueous solution storage tank 2, and a ferric salt aqueous solution (or ferric salt and mineral acid) respectively stored in the storage tank 1 and the storage tank 2 And an aqueous silicate solution are supplied to the raw material supply pipe 4 (or raw material supply pipe 4 ′) of the Y-tube reactor 3, and both aqueous solutions are collided and reacted in the reaction section 5. And an iron-silica water treatment flocculant can be manufactured by taking out a reaction material from the reaction part 5 through the discharge pipe 6. FIG.

  In the present invention, the ratio of the silicate aqueous solution and the ferric salt aqueous solution used for the production of the iron-silica water treatment flocculant is not particularly limited, and a known ratio can be adopted without limitation. The method of the invention can be produced without problems even in a composition having a high ratio of iron to silicon.

  As described above, among the silicate aqueous solution and the ferric salt aqueous solution used in the above ratio, the ferric salt aqueous solution may be at least partly mixed by collision mixing, and the remainder is usually For example, mixing can be performed by a mixing method using a mixing apparatus such as a reaction tank with a stirrer or a tube-type mixing apparatus with a baffle plate.

  As described above, when only a part of the ferric salt aqueous solution is collided with the silicate aqueous solution, the ferric salt aqueous solution having an Fe / Si molar ratio of 0.5 or more is used. It is preferable.

  Accordingly, the present invention includes the following aspects as described above.

  (1) In the collision mixing step, the total amount of the silicate aqueous solution to be used and a part of the ferric salt aqueous solution are collided and mixed to obtain a partial mixed solution, and the remaining ferric salt aqueous solution is added to the partial mixed solution. The aspect which obtains the target iron-silica water treatment flocculent by mixing by arbitrary methods.

  (2) The aspect which obtains the target iron-silica water treatment flocculant by carrying out collision mixing of the whole quantity of the silicate aqueous solution to be used, and the whole quantity of ferric salt aqueous solution in a collision mixing process.

  According to the method of the present invention, by providing a collision mixing step in which the ferric chloride aqueous solution and at least a part of the silicate aqueous solution are reacted by the collision mixing, the coagulation performance is excellent in a short time. An iron-silica water treatment flocculant can be produced.

Further, an iron-silica water treatment flocculant having a high SiO ₂ concentration of 10 g / L to 60 g / L and excellent aggregation performance can be produced in an amount of 2 L or more in one minute. Therefore, after the polymerization of polymerized silicic acid (silica sol), which is the conventional technique described above, is proceeded, a ferric salt aqueous solution is added, or in a reaction vessel, a silicate aqueous solution is added to an iron chloride aqueous solution. Compared with the method of adding, it can manufacture in a very short time, suppressing the gelatinization of a silica, and can exhibit the aggregation performance equivalent to or more than these prior art.

  Further surprisingly, the iron-silica water treatment flocculant produced by the impingement mixing of the present invention has a longer storage stability than the iron-silica water treatment flocculant produced by the prior art. Yes.

In order to maintain the long-term stability while maintaining the excellent aggregation performance of the iron-silica water treatment flocculant obtained by the method of the present invention, the obtained iron-silica water treatment flocculant has a pH of 0.00. 3 to 1.5, preferably less than 1.3 and 0.4 or more, and the iron concentration is 20 g / L to 120 g / L, preferably 20 g / L to 100 g / L, and the SiO ₂ concentration is 10 to 10. 50 g / L, preferably 10 g / L to 50 g / L.

  Incidentally, the iron-silica water treatment flocculant obtained by adjusting to the above conditions has a gelled product at 30 ° C. for 30 days or more and a maximum of 80 days as shown in the examples below. It is also possible to save without occurring. In addition, since it is a high concentration iron-silica water treatment flocculant, transportation costs can be reduced and it is economically advantageous. In actual use, it can be diluted to an arbitrary concentration on site.

  In the present invention, since the ferric salt aqueous solution exhibits acidity, it can be used as a pH adjuster for lowering the pH of the obtained iron-silica water treatment flocculant. When it is desired to lower the iron concentration without changing it, a mineral acid may be used in combination. Such mineral acid is not particularly limited, but sulfuric acid and hydrochloric acid are preferably used.

  That is, the present invention includes the following aspects as described above.

  (3) In the above-described aspects (1) and (2), the target iron-silica water treatment flocculant is obtained by adjusting the pH by adding a mineral acid in the collision mixing step.

  (4) In the above (1) and (2), an aspect of obtaining a target iron-silica water treatment flocculant by adjusting pH by adding a mineral acid after collision mixing.

  In the above aspect (3), the mineral acid may be added in any way in the collision mixing step, but the most recommended one is premixed in the aqueous ferric salt solution and this and the aqueous silicate solution. And collision mixing. In the above embodiment, it is of course possible to add the mineral acid at both the impact mixing step and after the impact mixing.

  The iron-silica water treatment flocculant obtained by the method of the present invention can be effectively used as it is or as a water treatment agent for various wastewaters after being diluted to an appropriate concentration.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(1) Collision mixing device (iron-silica water treatment flocculant manufacturing device)
In the Y-tube reactor shown in FIG. 1, a sodium silicate aqueous solution having a diameter (inner diameter) of 1.4 mm × length of 10 mm is used as a raw material supply pipe 4, and the diameter (inner diameter) of the throttle part is 1.2 mm. X A ferric chloride aqueous solution having a length of 10 mm is supplied from the raw material supply pipe 4 ′, collided and mixed in the reaction section 5, and the mixed liquid is taken out from the discharge pipe 6 (tube diameter (inner diameter) 6 mm × length 30 mm). We used what was made. The angle formed by the two raw material supply pipes 4 and 4 ′ of the Y-tube reactor was 90 degrees.

(2) Viscosity Measurement The viscosity was measured at 30 ° C. using an A & D tuning fork type vibration viscometer.

(3) Evaluation of flocculation performance Kaolin (1000 degrees of turbidity standard solution for water quality test manufactured by Wako Pure Chemical Industries, Ltd.) was added to tap water, and jar test was performed using the turbidity adjusted to 20 as test water. To 1000 ml of test water, a flocculant is added so that Fe is equivalent to 5 mg with respect to 1 L of water, stirred for 5 minutes at a stirring speed of 150 rpm, then stirred for 10 minutes at a stirring speed of 50 rpm, and further allowed to stand for 10 minutes. After that, 50 ml of the supernatant was collected. By the method of measuring turbidity, the performance of the iron-silica water treatment flocculant obtained by the present invention for water treatment was examined.

(4) Evaluation of storage stability Stability is evaluated by the number of days until precipitation or gelation occurs by leaving the iron-silica water treatment flocculant to stand at 30 ° C., visually determining the degree of precipitation or gelation. did.

Example 1
Commercially available sodium silicate (silicate aqueous solution: SiO ₂ concentration 28 mass%, SiO ₂ / Na ₂ O molar ratio 3.15) was diluted with water to obtain an aqueous solution having a SiO ₂ concentration of 70 g / L. On the other hand, a commercially available 39 mass% ferric chloride solution (ferric salt aqueous solution) was diluted with water to obtain an aqueous solution having a ferric chloride concentration of 190 g / L. Using the total amount of each of these aqueous solutions, the flow rate of the sodium silicate aqueous solution from the raw material supply pipe 4 was 1.0 L / min, and the flow rate of the ferric chloride aqueous solution from the raw material supply pipe 4 ′ was 0.9 L / min. Then, the reaction part 5 was collided and mixed and taken out from the discharge pipe 6. 5 L of an iron-silica water treatment flocculant was obtained in about 2 minutes and 40 seconds.

  At this time, the flow rates of the aqueous sodium silicate solution and the aqueous ferric chloride solution supplied to the reaction unit 5 were 10.8 m / s and 13.3 m / s, respectively, in the longitudinal direction of the raw material supply pipe. The flow rate at which the water treatment flocculant was discharged from the discharge pipe 6 was 1.1 m / s.

The obtained iron-silica water treatment flocculent was a yellowish-brown transparent liquid without silica gelation. This water treatment flocculant had a SiO ₂ concentration of 37 g / L, an iron concentration of 31 g / L, a Si / Fe molar ratio of 1.11, and a pH of 1.54.

  With respect to the water treatment flocculant thus obtained, the flocculation performance was confirmed according to the above method, and the storage stability at 30 ° C. was observed. These results are shown in Table 1.

Example 2
Sulfuric acid was added to the iron-silica water treatment flocculant obtained in Example 1 to adjust the pH of the flocculant to 1.05. The time from the addition of sulfuric acid to the final iron-silica water treatment flocculant was about 4 minutes from the start of impingement mixing. Table 1 shows the aggregation performance and storage stability of this water treatment flocculant.

Example 3
The iron-silica water treatment flocculant obtained in Example 1 was diluted with water, a ferric chloride aqueous solution and sulfuric acid were added, and the SiO ₂ concentration of the water treatment flocculant was 16 g / L, the iron concentration was 60 g / L, The Si / Fe molar ratio was 0.25, and the pH was 0.85. The time from dilution with water, addition of an aqueous iron chloride solution and sulfuric acid to a final iron-silica water treatment flocculant was about 5 minutes from the start of impingement mixing. Table 1 shows the aggregation performance and storage stability of the flocculant.

Example 4
As the sodium silicate aqueous solution, a commercially available sodium silicate (SiO ₂ concentration 28 mass%, SiO ₂ / Na ₂ O molar ratio 3.2) was diluted with water to obtain an aqueous solution having a SiO ₂ concentration of 110 g / L. The aqueous solution containing ferric chloride and mineral acid was prepared by diluting a commercially available 38% by mass ferric chloride aqueous solution with water, adding 48% by mass sulfuric acid, and containing sulfuric acid at a concentration of 44 g / L. / L ferric chloride aqueous solution. Using these aqueous solutions, the flow rate of the sodium silicate aqueous solution from the raw material supply pipe 4 ′ is 1.0 L / min, and the flow rate of the sulfuric acid-containing ferric chloride mixed aqueous solution from the raw material supply pipe 4 is 0.9 L / min. Then, the reaction part 5 was collided and mixed and taken out from the discharge pipe 6.

  5 L of a reaction solution (this is also referred to as “partial mixed solution”) of about 2 minutes and 40 minutes of the total amount of the aqueous silicate solution used for the production of the iron-silica water treatment flocculant and a part of the aqueous ferric salt solution. Got in seconds. At this time, the flow rates of the sodium silicate aqueous solution and the sulfuric acid-containing ferric chloride mixed aqueous solution supplied to the reaction section 5 were 10.8 m / s and 13.3 m / s, respectively.

  In the collision mixing step, the mixing amount of the ferric salt aqueous solution to be collision-mixed is iron with respect to silicon element (Si) in the total amount of the silicate aqueous solution used for producing the iron-silica water treatment flocculant. The amount of the element (Fe) was 0.78 times mol.

The obtained partial mixed solution was a yellowish-brown transparent liquid without any gelled silica. This partial mixture had a SiO ₂ concentration of 58 g / L, an iron concentration of 42 g / L, a Si / Fe molar ratio of 1.28, and a pH of 1.08.

500 ml of this partial mixed solution is put into a container, and 875 ml of water and 460 ml of 38 mass% ferric chloride aqueous solution are added to this with stirring, and the SiO ₂ concentration is 16 g / L, the iron concentration is 60 g / L, and the Si / Fe molar ratio is 0.00. 25, 1835 ml of an iron-silica water treatment flocculant having a pH of 0.82. The iron-silica water treatment flocculant could be produced in about 5 minutes from the start of collision mixing. Table 1 shows the aggregation performance and storage stability of this water treatment flocculant.

Example 5
The same reaction as in Example 4 was conducted except that the SiO ₂ concentration of the sodium silicate aqueous solution was 90 g / L, the ferric chloride concentration of the sulfuric acid-containing ferric chloride aqueous solution was 264 g / L and the sulfuric acid concentration 20 g / L. Then, 5 L of a yellowish-brown transparent partial mixture without silica gel was obtained in about 2 minutes and 40 seconds.
This partial mixed solution had a SiO ₂ concentration of 47 g / L, an iron concentration of 43 g / L, a Si / Fe molar ratio of 1.02, and a pH of 1.58.

  In the collision mixing step, the mixing amount of the ferric chloride aqueous solution to be collision-mixed is iron relative to silicon element (Si) in the total amount of the silicate aqueous solution used for the production of the iron-silica water treatment flocculant. The amount of the element (Fe) was 0.98 times mol.

500 ml of this partial mixed solution is taken in a container, and 330 ml of water, 350 ml of 38 mass% ferric chloride aqueous solution, and 4.0 ml of 50 mass% sulfuric acid are added with stirring to a SiO ₂ concentration of 20 g / L and an iron concentration of 75 g / L. 1184 ml of an iron-silica water treatment flocculant having a Si / Fe molar ratio of 0.25 and a pH of 0.73 was obtained. The iron-silica water treatment flocculant could be produced in about 5 minutes from the start of collision mixing. In addition, Table 1 shows the aggregation performance and storage stability of this iron-silica water treatment flocculant.

Example 6
In Example 5, 500 ml of a partial mixture of SiO ₂ concentration 47 g / L, iron concentration 43 g / L, Si / Fe molar ratio 1.02, pH 1.58 produced by impact mixing was added to 310 ml of water and 40% by mass of second chloride chloride. 350 ml of an aqueous iron solution and 20 ml of 50% by mass sulfuric acid were added to obtain 1180 ml of an iron-silica water treatment flocculant having a SiO ₂ concentration of 20 g / L, an iron concentration of 75 g / L, a Si / Fe molar ratio of 0.25, and a pH of 0.18. The iron-silica water treatment flocculant could be produced in about 5 minutes from the start of collision mixing. Table 1 shows the aggregation performance and storage stability of this water treatment flocculant.

Example 7
In Example 5, 500 ml of a partial mixture prepared by impact mixing and having a SiO ₂ concentration of 47 g / L, an iron concentration of 43 g / L, an Si / Fe molar ratio of 1.02, and a pH of 1.58 was placed in a container, and 330 ml of water was added thereto. , 42 mass% ferric chloride aqueous solution 110 ml, 50 mass% sulfuric acid 6.5 ml, SiO ₂ concentration 25 g / L, iron concentration 47 g / L, Si / Fe molar ratio 0.5, pH 0.98 iron-silica 946 ml of water treatment flocculant was obtained. The iron-silica water treatment flocculant could be produced in about 5 minutes from the start of collision mixing. Table 1 shows the aggregation performance and storage stability of this water treatment flocculant.

Reference example 1
Commercially available sodium silicate (SiO ₂ concentration 28 wt%, SiO ₂ / Na ₂ O molar ratio 3.15) is diluted with water, and 1 L of diluted sodium silicate solution with SiO ₂ concentration of 80 g / L is sulfuric acid concentration 50 g / L. Was introduced into 1 L of diluted sulfuric acid with stirring for 1 hour to obtain ₂ L of a silica sol solution having a SiO ₂ concentration of 40 g / L and a pH of 2.0. An alkali was added to the silica sol solution to adjust to pH 4, and then aged at room temperature for 3 hours.

Take 200 ml of this silica sol solution, add 50 ml of water and 150 ml of 39.5 mass% ferric chloride solution, and have an SiO ₂ concentration of 20 g / L, an iron concentration of 75 g / L, an Si / Fe molar ratio of 0.25, and a pH of 0.42. 400 ml of an iron-silica water treatment flocculant was obtained. This iron-silica water treatment flocculant required 4 hours and 20 minutes from the start of dripping of sodium silicate to the production. Table 1 shows the aggregation performance and storage stability of this water treatment flocculant.

Examples 8 and 9
In Example 5, the mixing amount of the ferric chloride aqueous solution in the impingement mixing was changed from the amount of iron element (Fe) to the amount of silicon element (Si) in the total amount of the silicate aqueous solution used for the production of the iron-silica water treatment flocculant. ) And the amount of addition of the remaining ferric chloride aqueous solution was adjusted to be the same as in Example 5 to obtain an iron-silica water treatment flocculant. . Table 2 shows the aggregation performance and storage stability of the obtained water treatment flocculant.

Example 10
The same reaction as in Example 4 was conducted except that the SiO ₂ concentration of the sodium silicate aqueous solution was 90 g / L, the ferric chloride concentration of the sulfuric acid-containing ferric chloride aqueous solution was 270 g / L, and the sulfuric acid concentration was 31 g / L. And 5 L of a yellowish brown transparent intermediate mixture without silica gel was obtained in about 2 minutes and 40 seconds. This partially mixed solution had a SiO ₂ concentration of 47 g / L, an iron concentration of 44 g / L, a Si / Fe molar ratio of 1.00, and a pH of 1.17.

  In the collision mixing step, the mixing amount of the ferric chloride aqueous solution to be collision-mixed is iron relative to silicon element (Si) in the total amount of the silicate aqueous solution used for the production of the iron-silica water treatment flocculant. The amount of the element (Fe) was 1.00 times mol.

500 ml of this partial mixed solution is taken, and 563 ml of water, 118 ml of 39 mass% ferric chloride aqueous solution and 4.4 ml of 50 mass% sulfuric acid are added thereto, SiO ₂ concentration 20 g / L, iron concentration 37 g / L, Si / Fe mole 1184 ml of an iron-silica water treatment flocculant having a ratio of 0.5 and a pH of 1.01 was obtained. The iron-silica water treatment flocculant could be produced in about 5 minutes from the start of collision mixing. Table 2 shows the aggregation performance and storage stability of this iron-silica water treatment flocculant.

[Comparative Reference Examples 1 and 2]
Comparative Reference Examples 1 and 2 shown in Table 2 are data disclosed in Patent Document 3 (Patent No. 3700892), and sodium silicate is added thereto while stirring a mixed aqueous solution of iron chloride and sulfuric acid. Is a flocculant property and performance of an iron-silica water treatment flocculant produced by the method described above. The water treatment flocculant obtained in Example 10 mentioned above has a slightly lower concentration and a slightly higher concentration than the silica concentration. The iron concentration and pH are equivalent to the water treatment flocculant obtained in Example 10.

  Comparing these data with the performance of the water treatment flocculant obtained in Example 10, the water treatment flocculant obtained in Example 10 was compared with either the silica concentration slightly lower or the higher concentration. However, better (long-term) storage stability is obtained.

  Furthermore, the temperature condition of 30 ° C. for storage stability evaluation in Example 10 is a stricter condition than room temperature, which is the temperature condition for storage stability evaluation in Comparative Reference Example. Therefore, when comparing the storage stability under the same temperature condition, the difference in the storable days is more clearly observed between the iron-silica water treatment flocculant obtained by the production method of the present invention and the water treatment flocculant in the comparative reference example. Expected to occur.

Schematic of a reactor that can be suitably used in the production method of the present invention (the Y-tube reactor portion is a cross-sectional view).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Storage tank of ferric salt aqueous solution (or aqueous solution containing ferric salt and mineral acid) 2 Storage tank of silicate aqueous solution 3 Y-shaped reactor 4 Raw material supply pipe 4 ′ Raw material supply pipe 5 Reaction section 6 Discharge tube

Claims (5)

When the iron-silica water treatment flocculant is produced by the reaction of the silicate aqueous solution and the ferric salt aqueous solution, the total amount of the silicate aqueous solution used for the production of the iron-silica water treatment flocculant and the ferric salt look including the impingement mixing step of impinging mixing at least a portion of the aqueous solution in a tubular reactor, and supplying the raw material supply pipe of the reactor as two solutions collide with either 5 m / sec or faster A method for producing an iron-silica water treatment flocculant characterized by the above.   In the collision mixing step, the mixing amount of the ferric salt aqueous solution to be subjected to the collision mixing is such that the iron element (Si) with respect to the silicon element (Si) in the total amount of the silicate aqueous solution used for the production of the iron-silica water treatment flocculant. The method for producing an iron-silica water treatment flocculant according to claim 1, wherein the amount is 0.5 mol or more by Fe). The obtained iron-silica water treatment flocculant has a pH of 0.3 to 1.5, an iron element concentration (Fe) of 20 g / L to 120 g / L, and a SiO ₂ concentration of 10 g / L to 50 g / L. And the manufacturing method of the iron-silica water treatment flocculent of Claim 1 or 2 whose Si / Fe molar ratio is 1 or less.   The method for producing an iron-silica water treatment flocculant according to any one of claims 1 to 3, further comprising a step of adding the remainder of the aqueous ferric salt solution to the mixture obtained in the collision mixing step.   The iron-silica water treatment flocculant according to any one of claims 1 to 3, comprising a step of adding the remainder of the ferric salt aqueous solution and a mineral acid to the mixture obtained in the collision mixing step. Production method.

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