JP2636203B2 - Preparation method of acid-resistant calcium silicate filter aid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The acid-resistant calcium silicate of the present invention is obtained by subjecting hard-to-filter slurry or dilute slurry to body-feed filtration or pre-coat filtration to separate solid-liquid and high-clarity filtrate. Recovery can be performed efficiently. The amount of CaO eluted from calcium silicate is controlled by controlling the raw material composition, the degree of carbonation, and the heat treatment temperature, and fatty acids, dyes, etc. in the solution are controlled by binding to Ca ²⁺ ions. It can also be used in food-related applications such as removal and immobilization. Further, it can be used for a wide range of purposes such as treatment and immobilization of heavy metal ion-containing waste liquid.

[0002]

2. Description of the Related Art Solid-liquid separation in the case where filter particles are clogged due to the sticky nature of dispersed particles in a slurry, and improvement of filtration speed and separation of a clarified filtrate when the dispersed particles are fine and low in concentration. Diatomaceous earth filter aid has been used for recovery. However, since the particle size and crystal form differ depending on the type of diatom, there is also a considerable difference in the properties as a filter aid, and there is a problem in quality control in a filter aid manufacturing process such as pulverization or classification. Furthermore, there are technical and economic disadvantages in Japan, such as a lack of high-grade diatomite deposits with abundant ore reserves and problems with stable supply.

[0003]

Calcium silicate granules obtained by hydrothermal synthesis are porous like diatomaceous earth, and have a particle diameter and crystal form without being ground or classified according to the purpose. It has many advantages as a filter aid, such as controllability and stable supply. However, it also has the disadvantage that the range of use is limited due to poor acid resistance. Therefore, development of a technique for imparting acid resistance without impairing the advantages of calcium silicate has been a problem.

[0004]

Means for Solving the Problems The present inventors have made intensive studies on methods for solving the conventional problems, and as a result, the silica raw material and the lime raw material have a Ca / Si molar ratio in the range of 0.2 to 1.2. Mix and use an autoclave to
Hydrothermal reaction in a 0.01 to 1.0 N KOH solution, followed by carbonation of the calcium silicate followed by treatment in an acidic solution or in an acidic solution, followed by further heat treatment at 800 to 1400 ° C. The present invention has found a method for preparing an acid-resistant calcium silicate filter aid which has excellent acid resistance and markedly improved filtration characteristics without impairing the crystal shape, and has led to the present invention.

As the silica raw material, various silica-containing materials such as silicate raw materials such as quartz and rice ash and aluminum silicate raw materials such as fly ash and shirasu can be effectively used. As the lime raw material, quick lime, slaked lime and the like can be used.

If the Ca / Si molar ratio of the mixture of the silica raw material and the lime raw material is low, the formation of calcium silicate is insufficient and the effect as a filter aid is not exhibited. On the other hand, when the molar ratio of Ca / Si becomes high, unreacted lime raw material remains as it is, and at the same time, calcium silicate with high crystallinity cannot be obtained.Therefore, the mixing ratio of the silica raw material and the lime raw material has an appropriate range. The suitable range is 0.2 to 1.2 in a Ca / Si molar ratio.

The reason why the mixture of the silica raw material and the lime raw material is hydrothermally reacted in a KOH solution is to change the crystal form of calcium silicate and at the same time promote the hydrothermal reaction. When the concentration of the KOH solution is low, the effect of adding KOH is not exhibited. On the other hand, when the concentration of the KOH solution increases, there is a change in the crystal form and an effect of promoting the reaction, but there is no effect of improving the filtration characteristics corresponding to the increase in the KOH solution concentration, and the suitable range of the KOH solution concentration is 0.01 to 1.0 N. is there.

[0008] The acid treatment after the carbonation of calcium silicate is performed by removing CaO as CaCO ₃ from calcium silicate without changing the crystal shape of calcium silicate by the carbonation treatment. This is because CaCO ₃ is dissolved and removed from the slurry by acid treatment.

The heat treatment of calcium silicate is for changing the crystal structure and further improving the insolubility in an acid solution. When the heat treatment temperature of calcium silicate is low, there is no further insoluble effect of calcium silicate in the acid solution due to the heat treatment. On the other hand, when the heat treatment temperature is high, the insolubility effect of calcium silicate in the acid solution is large, but the calcium silicate shrinks and changes the crystal morphology before heat treatment, so that it has properties as a filter aid. Therefore, the heat treatment temperature of calcium silicate has an appropriate range, and the appropriate temperature range is 800 to 1400 ° C.

[0010]

The test results of Examples and Comparative Examples of the present invention are shown below.

(Embodiment 1) Silica raw material and lime raw material were Ca / S
A 20-fold weight ratio of water was added to the mixed powder adjusted to 0.8 in an i molar ratio, and a hydrothermal reaction was performed while stirring and stirring the stirred slurry at 180 ° C for 8 hours in an autoclave. Thus, a calcium silicate slurry was obtained. Carbon dioxide gas was blown into this calcium silicate slurry, and the pH of the slurry in which the carbonation rate of CaO in the calcium silicate became 53% was adjusted to pH 1.5 with HCl, and the mixture was stirred for 10 minutes. The calcium silicate was filtered, dehydrated and dried at 120 ° C. for 8 hours to obtain an acid-resistant calcium silicate filter aid.

(Example 2) Silica raw material and lime raw material were Ca / S
A 20-fold weight ratio of water was added to the mixed powder adjusted to 0.6 in an i molar ratio, and a hydrothermal reaction was performed while stirring and mixing the stirred slurry at 180 ° C. for 8 hours in an autoclave. Thus, a calcium silicate slurry was obtained. Carbon dioxide gas was blown into this calcium silicate slurry, and the slurry in which the carbonation ratio of CaO in the calcium silicate was 5% was adjusted to pH 1.5 with HCl, and then stirred for 10 minutes. The calcium silicate was filtered, dehydrated and dried at 120 ° C. for 8 hours to obtain an acid-resistant calcium silicate filter aid.

(Example 3) Silica raw material and lime raw material were Ca / S
A 20-fold weight ratio of water was added to the mixed powder adjusted to 0.6 in an i molar ratio, and a hydrothermal reaction was performed while stirring and mixing the stirred slurry at 180 ° C. for 8 hours in an autoclave. Thus, a calcium silicate slurry was obtained. Carbon dioxide gas was blown into this calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate was 3% was adjusted to pH 1.5 with HCl, and stirred there for 10 minutes. The calcium silicate was filtered, dehydrated and dried at 120 ° C. for 8 hours to obtain an acid-resistant calcium silicate filter aid.

(Example 4) The raw material of silica and the raw material of lime were Ca / S
A 20-fold weight ratio of water was added to the mixed powder adjusted to 0.6 in an i molar ratio, and a hydrothermal reaction was performed while stirring and mixing the stirred slurry at 180 ° C. for 8 hours in an autoclave. Thus, a calcium silicate slurry was obtained. Carbon dioxide gas was blown into this calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate became 96% was adjusted to pH 1.5 with HCl, and the mixture was stirred for 10 minutes. The calcium silicate was filtered, dehydrated and dried at 120 ° C. for 8 hours to obtain an acid-resistant calcium silicate filter aid.

(Example 5) Silica raw material and lime raw material were Ca / S
To the mixed powder whose molar ratio was adjusted to 0.6, a 0.1N-KOH solution at a 20-fold weight ratio was added, and the slurry was mixed and stirred at 180.
A hydrothermal reaction was carried out while stirring in an autoclave at 8 ° C. for 8 hours to obtain a calcium silicate slurry. Carbon dioxide gas is blown into this calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate has become 5% is H
The pH was adjusted to 1.5 with Cl, where it was stirred for 10 minutes. The calcium silicate was filtered, dehydrated and dried at 120 ° C. for 8 hours to obtain an acid-resistant calcium silicate filter aid.

(Example 6) Silica raw material and lime raw material were Ca / S
A 20-fold weight ratio of water was added to the mixed powder adjusted to 0.6 in an i molar ratio, and a hydrothermal reaction was performed while stirring and mixing the stirred slurry at 180 ° C. for 8 hours in an autoclave. Thus, a calcium silicate slurry was obtained. Carbon dioxide gas was blown into this calcium silicate slurry, and the pH of the slurry in which the carbonation rate of CaO in the calcium silicate became 53% was adjusted to pH 1.5 with HCl, and the mixture was stirred for 10 minutes. The calcium silicate is filtered, dehydrated, dried at 120 ° C for 8 hours, and put in an electric furnace.
Heat treatment was performed at 1100 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

(Example 7) Silica raw material and lime raw material were Ca / S
A 20-fold weight ratio of water was added to the mixed powder adjusted to 0.6 in an i molar ratio, and a hydrothermal reaction was performed while stirring and mixing the stirred slurry at 180 ° C. for 8 hours in an autoclave. Thus, a calcium silicate slurry was obtained. Carbon dioxide gas was blown into this calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate was 3% was adjusted to pH 1.5 with HCl, and stirred there for 10 minutes. The calcium silicate is filtered, dehydrated, dried at 120 ° C for 8 hours, and put in an electric furnace.
Heat treatment was performed at 1100 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

(Example 8) Silica raw material and lime raw material were Ca / S
A 20-fold weight ratio of water was added to the mixed powder adjusted to 0.6 in an i molar ratio, and a hydrothermal reaction was performed while stirring and mixing the stirred slurry at 180 ° C. for 8 hours in an autoclave. Thus, a calcium silicate slurry was obtained. Carbon dioxide gas was blown into this calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate became 96% was adjusted to pH 1.5 with HCl, and the mixture was stirred for 10 minutes. The calcium silicate is filtered, dehydrated, dried at 120 ° C for 8 hours, and put in an electric furnace.
Heat treatment was performed at 1100 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

(Example 9) Silica raw material and lime raw material were Ca / S
To the mixed powder whose molar ratio was adjusted to 0.6, a 0.1N-KOH solution at a 20-fold weight ratio was added, and the slurry was mixed and stirred at 180.
A hydrothermal reaction was carried out while stirring in an autoclave at 8 ° C. for 8 hours to obtain a calcium silicate slurry. Carbon dioxide gas is blown into this calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate has become 5% is H
The pH was adjusted to 1.5 with Cl, where it was stirred for 10 minutes. The calcium silicate was filtered, dehydrated, dried at 120 ° C. for 8 hours, and then heated in an electric furnace at 1100 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

Example 10 A silica raw material and a lime raw material were converted to Ca
/ Si molar ratio of mixed powder adjusted to 0.6, 20 by weight
Water was added, mixed and stirred, and the slurry was stirred at 180 ° C. for 8 hours in an autoclave to carry out a hydrothermal reaction to obtain a calcium silicate slurry. Carbon dioxide gas is blown into the calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate is 53% is adjusted to pH 1.5 with HCl.
And then stirred for 10 minutes. The calcium silicate was filtered, dehydrated, dried at 120 ° C. for 8 hours, and then heated in an electric furnace at 1100 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

(Example 11) Silica raw material and lime raw material were Ca
/ Si molar ratio of mixed powder adjusted to 0.6, 20 by weight
Water was added, mixed and stirred, and the slurry was stirred at 180 ° C. for 8 hours in an autoclave to carry out a hydrothermal reaction to obtain a calcium silicate slurry. Carbon dioxide gas is blown into this calcium silicate slurry, and the slurry in which the carbonation rate of CaO in the calcium silicate has become 3% is adjusted to pH 1.5 with HCl.
And then stirred for 10 minutes. The calcium silicate was filtered, dehydrated, dried at 120 ° C. for 8 hours, and then heated in an electric furnace at 1100 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

(Example 12) Silica raw material and lime raw material were Ca
/ Si molar ratio of mixed powder adjusted to 0.6, 20 by weight
Water was added, mixed and stirred, and the slurry was stirred at 180 ° C. for 8 hours in an autoclave to carry out a hydrothermal reaction to obtain a calcium silicate slurry. Carbon dioxide gas is blown into this calcium silicate slurry, and the slurry in which the carbonation ratio of CaO in the calcium silicate is 96% is adjusted to pH 1.5 with HCl.
And then stirred for 10 minutes. The calcium silicate was filtered, dehydrated, dried at 120 ° C. for 8 hours, and then heated in an electric furnace at 1100 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

The acid-resistant calcium silicate filter aid obtained by the above Examples and, as a comparative example, the acid resistance, the constant filtration coefficient of loose and the clarity of the filtrate of a commercially available heat-treated diatomaceous earth filter aid. It is shown in Table 1. The acid resistance, the constant pressure filtration coefficient of the loose and the clarity of the filtrate were measured as follows.

[0024]

[Table 1]

The acid resistance is adjusted using a constant temperature water bath adjusted to 30 ° C.
0.15 g of the sample is immersed in 200 ml of a solution adjusted to pH 2 with HCl.
After stirring and mixing for 1 hour, solid-liquid separation was performed using a centrifugal separator, and then SiO ₂ and CaO in the filtrate were measured using a spectrophotometer and an atomic absorption spectrophotometer. of
Evaluation was made based on the elution amounts of SiO ₂ and CaO.

The filtration experiment was carried out using a pressure filter having a filtration area of 19.3 cm ² , and various filter aids were body-fed to the clay clay slurry to obtain Ruth's constant pressure filtration coefficient K ₂₀ [Ruth]. cm ²
/ sec] (K value at a slurry temperature of 20 ° C.). The filtration pressure at that time is 0.5 kg / cm ² , the slurry concentration is 0.005, F / C
The volume mixing ratio of (filtering aid / Frogme clay) was 0.3 and 0.5. Heal - scan constant pressure filtration coefficient K ₂₀ of show that higher filtration rates the number, the greater is fast.

The clarity of the filtrate was measured by using the transmittance measurement of a spectrophotometer. The clarity was defined as 0 when the transmittance was set to 0 and the clarity was set to 100 when the transmittance of distilled water was 100. Was regarded as 100, and the clarity of the filtrate after the filtration experiment was evaluated. For the measurement of the clarity of the filtrate, the filtration pressure was 0.5 kg / cm ² and the slurry was
The concentration was 0.005, the volume mixing ratio of F / C was 0.5, and the filtrate one minute after the start of the filtration experiment was used.

[0028]

EFFECT OF THE INVENTION The solubility of the acid-resistant calcium silicate filter aid obtained by the present invention is greatly suppressed, comparable to that of the existing diatomaceous earth filter aid, and the constant pressure filtration coefficient of the loose and the filtrate. Is also superior to diatomaceous earth filter aid in terms of filtration characteristics such as clarity. Also, unlike the diatomaceous earth filter aid, pulverization, classification and the like are not required, and by appropriately adjusting the reaction conditions, it is possible to easily and stably supply a filter aid having a particle diameter and a crystal form according to the purpose. It is possible and has high industrial value. further,
The amount of CaO eluted can be controlled by changing the raw material composition and the heat treatment temperature, and it can be widely used for removing and fixing fatty acids, dyes, heavy metal ions, and the like in the solution by bonding with Ca ²⁺ ions.

Claims (4)

(57) [Claims] 1. A silica raw material and a lime raw material in a Ca / Si molar ratio.
An acid-resistant mixture characterized by mixing in the range of 0.2 to 1.2, causing a hydrothermal reaction in an aqueous solution using an autoclave, then subjecting the calcium silicate to a carbonation treatment, and further treating the calcium silicate in an acidic solution. Adjustment method of basic calcium silicate filter aid. 2. A silica raw material and a lime raw material in a Ca / Si molar ratio.
Mix in the range of 0.2-1.2 and use an autoclave to reach 0.1.
A method for preparing an acid-resistant calcium silicate filter aid, which comprises a hydrothermal reaction in a KOH solution of 01 to 1.0 N, a carbonation treatment of the calcium silicate, and a treatment in an acidic solution. 3. A silica raw material and a lime raw material in a Ca / Si molar ratio.
The mixture is mixed in the range of 0.2 to 1.2, hydrothermally reacted in an aqueous solution using an autoclave, and then the calcium silicate is subjected to a carbonation treatment, followed by treatment in an acidic solution, and further to 800 to 140
A method for preparing an acid-resistant calcium silicate filter aid, characterized by heating at 0 ° C. 4. A raw material of silica and a raw material of lime at a Ca / Si molar ratio.
Mix in the range of 0.2-1.2 and use an autoclave to reach 0.1.
Hydrothermal reaction in a KOH solution of 01-1.0 N, then carbonation of the calcium silicate followed by treatment in an acidic solution,
A method for preparing an acid-resistant calcium silicate filter aid, which further comprises heating at 800 to 1400 ° C.