JP2001070708A - Production of flocculant for water treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce a flocculant having an effective component ratio optimum to target water by a proper amt. on the water treatment spot. SOLUTION: A strong acidic silicic acid aq.soln. with a pH of 1-2 is heated to 50-80 deg.C under stirring in a stirring polymn. tank 6 having a heater 11 to be polymerized and a ferric chloride soln. is added to this polymerized soln. to set the concn. of silicon(Si) in the acidic silicic acid soln. to about 2.5-3.5 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a coagulant for water treatment for removing impurities from water.

[0002]

2. Description of the Related Art In recent years, the contamination of water sources with organic matter has been progressing, and a high-performance flocculant for coagulating and removing pollutants has been demanded. However, polyaluminum chloride widely used in Japan has been demanded. It has been pointed out that aluminum-based flocculants such as (PAC) and aluminum sulfate may cause nervous system diseases such as Alzheimer's disease when remaining in treated water. In addition, the use of an inorganic coagulant containing a metal other than aluminum, such as ferric chloride or ferric sulfate, is also expected, but has a disadvantage that the coagulation effect is inferior to PAC.

On the other hand, a method of improving the coagulation effect by using a synthetic organic polymer flocculant such as polyacrylamide in combination with an iron salt coagulant has been considered, but the monomer contained in the synthetic organic polymer coagulant is toxic. Currently, use in water supply is not permitted in Japan.

The present applicant has already proposed a coagulant containing polymerized silicic acid and an iron salt as an inorganic polymer coagulant having no effect on safety and having a high coagulation effect (Patent No. 1).
No. 873473, Patent No. 273,067 and Patent No. 2
No. 759853), and the technology according to these patents is of great interest also from the viewpoint of the advantage of utilizing the silicon-containing resources available everywhere on the earth.

[0005]

In the technology proposed in each of the above patents, the coagulant tends to be in an unstable state by nature, so that the coagulant is transported between a manufacturing place and a use place. From the viewpoint of storage or mass production,
The problem remains.

That is, if the concentration of an active ingredient such as Si is increased to make the coagulation effect of the coagulant the same as that of PAC, the storage period in a stable state becomes relatively short. In each case, there is a possibility that it must be manufactured at a remote manufacturing plant and immediately transported to a water treatment site. On the other hand, if the active ingredient concentration is lowered so that it can be stored for a relatively long time at the water treatment site, the amount of the produced flocculant will increase significantly, increasing the transportation cost and constructing a very large storage tank at the water treatment site. There is a possibility that it is necessary to keep it.

[0007] In the above-mentioned Patent No. 2759853, a coagulant having a high concentration and high stability is proposed. However, since it is necessary to perform a treatment using an ion exchange resin in the production process, the production cost may be increased. was there. Further, as a problem in mass production, generally, in order to perform a polymerization treatment so that the raw material does not gel during the production of a flocculant using a silicic acid solution, it is necessary to always maintain an appropriate pH value.
In the case of mass production, strict control of the pH value may not always be easy.

Further, the optimum content ratio of both (silicon and iron) in the flocculant composed of polymerized silicic acid and iron salt varies depending on the properties and properties of the water to be treated. Therefore, the coagulant produced at a manufacturing plant with the ratio of both being constant may not always produce the best coagulation effect on the water to be treated at the site of use.

[0009] The present invention avoids the above-mentioned difficulties in the prior art, and produces a coagulant for water treatment so that a coagulant having the best effect on the water to be used can be obtained even at the site of use. The aim is to provide a method.

[0010]

SUMMARY OF THE INVENTION In the present invention, having a low pH value, which is usually treated as a non-polymerized zone,
A means is used in which a strongly acidic silicic acid solution having a pH of 1 or 2 is heated to 50 ° C. to 80 ° C., which is significantly higher than room temperature, and is stirred in that state to polymerize. That is, in the method of the present invention, an acidic silicic acid solution having a pH value of about 1.0 to 2.0 is stirred under heating at about 50 ° C. to 80 ° C. to obtain polymerized silicic acid.
This is a method for producing a coagulant for water treatment, comprising adding ferric chloride thereto (Claim 1). In the above-mentioned method, the concentration of silicon (Si) in the acidic silicic acid solution is reduced. A method for producing a coagulant for water treatment, wherein the content is about 2.5 to 3.5% by weight (Claim 2).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventionally, when a silicic acid solution is polymerized into a flocculant, it has been considered how to set the Si concentration and the pH value at normal temperature to perform the polymerization operation. However, in the present invention, while maintaining a low pH value, which was considered to be unsuitable for the polymerization treatment, the polymerization is carried out in a state where it is heated to a temperature significantly higher than room temperature, from a conventional preconception. The use of surprising means has made it possible to install production equipment with an easy polymerization operation at the water treatment site, so that the coagulant with the optimal specifications can always be produced and used immediately. enable.

[0012]

EXAMPLE A flocculant was produced using the apparatus shown in the flow sheet of FIG. In FIG. 1, 1 is a water glass storage tank (1
00l), 2 is hydrochloric acid storage tank (50l), 3 is ferric chloride storage tank (100l), 4 is dilution water storage tank (100l)
l), 5 is a flocculant dilution storage tank (300 l), 6 is a stirred polymerization reaction tank (75 l internal volume). In the initial stage, all the valves V1 to V9 are closed, the metering pumps P1 to P6 are stopped, the stirrers 7 and 8 are stopped, and the heater 10 is stopped. Chemical or tap water is full.

The valves V1 and V4 are opened, and the discharge rates of the metering pumps P1 and P4 are respectively adjusted to 605 ml / m
The in-line mixer 9 is operated for 10 minutes simultaneously with in and 1140 ml / min, and the diluted hydrochloric acid solution stirred and mixed is transferred to the stirred polymerization reaction tank 6. After transfer, valve V1
And V4 are closed, and the operation of the stirrer 7 of the stirred polymerization reaction tank 6 is started.

Next, the valves V2 and V5 are opened,
The discharge rates of the metering pumps P2 and P4 are set to 110
It was operated at 292 ml / min and 292 ml / min, and stirred and mixed with the in-line mixer 10 to reduce the Si concentration to 4.6.
% Of the diluted water glass solution is added dropwise to the stirred 10% hydrochloric acid in the stirred polymerization reaction tank 6 at a rate of 402 ml / min for 120 minutes. After the dropping, the operation of the metering pumps P2 and P4 is stopped, and the valves V2 and V5 are closed. After the completion of the dropping, the content is pH 1.3 to 1.5, Si
It was an acidic silicic acid solution having a concentration of about 3.4%.

Next, the stirring polymerization reaction tank 6 was heated to 60 ° C. by the heater 11 while continuing stirring, and the state was continued for 90 minutes to promote polymerization, thereby preparing polymerized silicic acid.

After completion of the polymerization, the heating by the heater 11 is stopped, the valve V3 is opened, and 9.38 liters of the ferric chloride solution is charged into the stirred polymerization reaction tank 6 using the metering pump P3.
After the ferric chloride dissolution is completed, the metering pump P3 is stopped, the valve V3 is closed, and the polymerized silicic acid solution and the ferric chloride aqueous solution are sufficiently stirred and mixed to obtain a flocculant, and the flocculant production is completed. Thereafter, the operation of the stirrer was stopped. The coagulant manufactured here had a Si concentration of 2.9% and an iron concentration of 1.9% (as F).
e), the molar ratio was 3: 1 (Si: Fe), the intrinsic viscosity was 0.38 (100 ml / g), and it had high coagulation performance.

When the produced flocculant is used as it is, the valve V6 is opened, and a predetermined amount is poured into raw water by a constant-rate pouring pump P5 to perform flocculation treatment. When the manufactured flocculant is to be temporarily stored, the valve V7 is opened and the flocculant is transferred to the flocculant dilution storage tank 5 by the metering injection pump P5.
Next, the valve 8 is opened, and tap water of twice the amount of the flocculant is injected by the metering infusion pump 4 and stirred to dilute the flocculant to a concentration of 1/3. If necessary, the valve V9 is opened to quantify the flocculant. A predetermined amount is injected into the raw water to be treated by the injection pump P6.

[0018]

According to the production method of the present invention, a coagulant for water treatment containing polymerized silicic acid and an iron salt, which has high safety and high coagulation effect, and whose raw material is easily available, has a strict pH value. It can be manufactured in large quantities while avoiding the cumbersome operation of simple control, so that the flocculant can be manufactured by a simple device installed at the water treatment site, thereby always providing the component specifications suitable for the water to be treated. This makes it possible to produce the required amount of flocculant.

[Brief description of the drawings]

FIG. 1 is a flow sheet of one embodiment of the method of the present invention.

[Explanation of symbols]

 1 ・ ・ ・ ・ ・ Water glass storage tank 2 ・ ・ ・ ・ ・ ・ ・ Hydrochloric acid storage tank 3 ・ ・ ・ ・ ・ ・ ・ Ferric chloride storage tank 4 ・ ・ ・ ・ ・ ・ ・ Water storage tank for dilution 5 ・ ・ ・ ・ ・ ・ ・ Coagulant dilution Storage tank 6. Stirred polymerization reaction tank 7.8 Stirrer 9.10 Inline mixer 11 Heater V1-V9 {Valve P1-P6} Metering pump M1. M2 motor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Fumio Shirato 1-11-9 Rinma, Yamato-shi, Kanagawa F-term (reference) 4D015 BA03 BA09 BA10 BB05 CA14 DA13 DA35 4D062 BA03 BA09 BA10 BB05 CA14 DA13 DA35

Claims (2)

[Claims] 1. An acidic silicic acid solution having a pH of 1 to 2 is added to 50
A method for producing a coagulant for water treatment, characterized in that a polymerized silicic acid is obtained by stirring under heating at a temperature of from 80 ° C. to 80 ° C., and ferric chloride is added thereto. 2. The method for producing a coagulant for water treatment according to claim 1, wherein the silicon concentration (Si concentration) in the acidic silicic acid solution is 2.5 to 3.5%.