JPS5848488B2 - Silica sol manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an acidic silicate sol by mixing sodium silicate or a mixture of sodium silicate and potassium silicate with an acidic substance as a coagulation treatment agent for sludge or sludge-like substances. It is something.

In such a method, for example, 10% of sulfuric acid (98% concentration)
When a 2-fold diluted solution and a 2-fold diluted solution of sodium silicate (equivalent to J I 83) are stirred and mixed, the mixture gradually gels and then completely gels in the neutralization region.

It has a neutral pH of 7. 5, the shortest (about 10
This is because it gels in seconds).

When gelatinized in this way, problems occur in removal from the reaction tank (mixing tank) and subsequent use.

Therefore, the present invention provides a method for producing silica sol that can be transferred to a solubilized sol region by passing through a neutralization region in a short period of time, and one embodiment thereof will be described below with reference to the drawings.

That is, in the present invention, an amount of acid necessary for producing silica sol is supplied into the reaction tank 1 from the acid liquid tank 2 via the acid supply pump 3, and then the acid supply pump 3 is stopped.

Next, the stirring device 4 is operated to set the stirring blade 5 at a circumferential speed of 1.
Rotate at 0 m/sec or more to keep the acid in a stirring state.

At this time, the circulation pump 6 is also operated to prevent stagnation in the reaction tank 1.

After reaching this state, the sodium silicate supply pump 7 is operated, and the sodium silicate solution in the sodium silicate solution tank 8 is added dropwise to the stirring blade 5 in an appropriate diameter (lm or less). let

In this way, sodium silicate, which is a strong alkali, will be reduced to 0.
It shifts to the strong acid side in less than 1 second.

This is the condition for stability of the silica sol liquid.

By continuing the above-mentioned dropwise addition, the desired silica sol solution can be produced, starting from the lower sodium silicate concentration and gradually increasing the concentration.

If the order of addition of both solutions is reversed, i.e., if an acid solution is added to a sodium silicate solution, no matter how thorough the stirring is, the acid will not diffuse but will react with the sodium silicate solution. It forms a gel and precipitates, resulting in a stable substance that is useless as silica crane.

Therefore, production cannot be performed unless the order of addition is followed.

That is, if a sodium silicate solution is used for gelation with an acid, the solution may be added in either direction, but there is an order of addition in order to make a sol solution.

Furthermore, if insufficient stirring occurs in the reaction tank 1, the silica sol solution will accumulate at the bottom of the reaction tank 1, so it must be constantly circulated by the circulation pump 6.

A large amount of silica sol can be produced by circulating and forcibly stirring the mixture to achieve the desired pH of 1.0 to 2.0.

This silica sol liquid is supplied to a tank (not shown) of the processing equipment by a supply pump 9.

Next, the significance and effects of circulation and stirring will be described.

A. The reaction formula when an acidic substance is added to sodium silicate without stirring or with gentle stirring is Na2 0 . nSt 02 + H2 S 04
"'-"Na2S 04+ nH2 Si 03→
Na2 S 04 + H20 + ( S t 02
).

As a result, a stable gel is generated, making it unsuitable for use as the intended coagulant.

B. The reaction formula when silicate is added little by little into an acidic substance by forced stirring is: 2H2SO4+Na20' nsi02 →H2SO4+Na2SO4+(SiO2)aq+H2
0→Na2 S 04 + H2 0 + S i (
OH)2S04, and the main component of silica sol (
S i (OH)2 804 ), which is completely different from the substance f), can be produced.

After stirring the material produced by this process into sludge or sludge, the mixture is stirred and neutralized with a strong alkaline solution or sodium silicate to generate a stable gelling substance, which can be used as the main agent for sludge treatment. Become.

When gelling sludge or sludge-like substances using the acidic silicic acid sol (silica sol) produced as described above, even if the acidic silicic acid sol is added to the sludge and neutralized after mixing, or the sludge is converted into an alkanoic material. Even if the acidic silicic acid sol is added, stirred, and then neutralized, a good solidified product can be obtained regardless of the order of addition.

According to the method of the present invention described above, an acidic solution is placed in a reaction tank and rapidly stirred by a stirring blade, and at the same time, the acidic solution in the reaction tank is circulated by a circulation pump to prevent stagnation. When a solution prepared by diluting and dissolving a mixture of potassium silicate and potassium silicate is added dropwise to the acidic solution, it can be shifted to the strong acid side in an extremely short time.

Therefore, it is possible to obtain an acidic silicic acid sol that can be easily taken out from the reaction tank, and since sufficient time is allowed for subsequent gelation, it can be advantageously employed as a main agent for sludge treatment.

[Brief explanation of the drawing]

The drawing is a flow sheet diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction tank, 2... Acid liquid tank, 3... Acid supply tank, 4... Stirring device, 5... Stirring blade, 6...
- Circulation pump, 7... Sodium silicate supply pump, 8゜゜゛Sodium silicate solution tank, 9... Supply pump.

Claims (1)

[Claims] 1. In a method of producing acidic silicic acid sol by mixing sodium silicate or a mixture of sodium silicate and potassium silicate with an acidic substance as a coagulation treatment agent for sludge or sludge-like substances, an acidic solution is placed in a reaction tank. Rapid stirring is performed using a stirring blade, and the acidic solution in the reaction tank is circulated using a circulation pump to prevent stagnation. A method for producing silica sol, characterized by adding dropwise a solution having an appropriate diameter.