JPH11278830A - Production of polyaluminum chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance solubility by mixing and reacting a sulfate with an alkali aluminate at a specified temp. or below and dissolving the resultant aluminum hydroxide gel having a specified concn. of alumina in a basic aluminum chloride. SOLUTION: A sulfate is mixed and reacted with an alkali aluminate at <=50 deg.C and the resultant aluminum hydroxide gel having <=5 wt.% concn. of alumina (expressed in terms of Al2 O3 ) is dissolved in a basic aluminum chloride preferably before the aging of the gel proceeds substantially. The sulfate is, e.g. aluminum sulfate. The alkali aluminate is, e.g. sodium aluminate or potassium aluminate. The basic aluminum chloride is preferably aluminum chloride having a basicity of >0 to <50% represented by the formula Aln (OH)m Cl3n-m .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyaluminum chloride, which is useful as an aggregating agent for river water, mining and industrial effluent, dyeing effluent, water and sewage and the like.

[0002]

2. Description of the Related Art Conventionally, polyaluminum chloride has been produced by a method in which various additives are mixed and reacted with basic aluminum chloride obtained by reacting hydrochloric acid and aluminum hydroxide in order to adjust the alumina concentration and basicity. Have been. For example, a method of dissolving aluminum hydroxide obtained by mixing and reacting aluminum sulfate, sodium carbonate and sodium aluminate in basic aluminum chloride (Japanese Patent Publication No. 63-12645), basic aluminum chloride, carbonate and aluminate A method in which aluminum hydroxide obtained by mixing and reacting an acid-alkali solution is dissolved in basic aluminum chloride, aluminum chloride and sodium aluminate are mixed and reacted, and the aluminum hydroxide obtained by filtration is converted into hydrochloric acid or aluminum chloride. A dissolving method (Japanese Patent Publication No. 2-4534) is known.

The aluminum hydroxide obtained by the above method is easily soluble and can give a highly basic polyaluminum chloride. However, since a carbonate is used, carbon dioxide is generated during mixing. There was a need for ventilation and liquid splash measures. Moreover, the use of carbonates was costly. When the aluminum hydroxide obtained by the above method was dissolved under normal pressure, the solubility of the aluminum hydroxide was insufficient.

[0004]

In view of such circumstances,
The present inventors have conducted intensive studies to find a method for obtaining a readily soluble aluminum hydroxide gel without using a carbonate in a method for producing polyaluminum chloride obtained by dissolving an aluminum hydroxide gel in basic aluminum chloride. As a result, the present inventors have found that an aluminum hydroxide gel having a specific concentration obtained by reacting a sulfate and an alkali aluminate under specific conditions has unprecedented solubility, and completed the present invention.

[0005]

That is, according to the present invention, an alumina concentration (in terms of Al ₂ O ₃ ) of 5% by weight obtained by mixing and reacting a sulfate and an alkali aluminate at a temperature of 50 ° C. or less.
An object of the present invention is to provide a method for producing polyaluminum chloride (hereinafter sometimes referred to as PAC) obtained by dissolving the following aluminum hydroxide gel in basic aluminum chloride (hereinafter sometimes referred to as BAC).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, the sulfate and the alkali aluminate are heated to a temperature of 50
Alumina concentration (in terms of Al ₂ O ₃ )
It is characterized in that an aluminum hydroxide gel of 5% by weight or less is produced.

The sulfate of the present invention is sulfuric acid, aluminum sulfate, polyaluminum chloride and the like. Of course, these two
More than one species may be used in combination. The polyaluminum chloride generally has a composition represented by the formula: Al _n (OH) _m Cl _3n-m (SO ₄ ) _Z , wherein Z is 0.05 to 0.5;
_{The 2} O ₃ concentration is about 10% by weight or less. Preferably Al ₂ O ₃
A concentration of about 8% to about 0.1% by weight, more preferably A
l is ₂ O ₃ concentration of about 4 wt% to about 0.1% by weight of. When the concentration of Al ₂ O _{3 in the} polyaluminum chloride is higher than about 10% by weight, the solubility of the aluminum hydroxide gel decreases. When the polyaluminum chloride is used, it is economical and recommended to use the polyaluminum chloride recovered from the step in the process for producing the polyaluminum chloride of the present invention or other production methods.

The alkali aluminate of the present invention includes conventionally known sodium aluminate, potassium aluminate and the like.

[0009] The reaction temperature of the present invention is about 50 ° C or less, preferably about 10 ° C to about 40 ° C. If the temperature is higher than about 50 ° C., the solubility of the aluminum hydroxide gel in basic aluminum chloride decreases.

The aluminum hydroxide gel of the present invention has an alumina concentration (in terms of Al ₂ O ₃ ) of about 5% by weight or less, preferably about 2.5% by weight to about 4.5% by weight. If the alumina concentration is higher than about 5% by weight, the solubility of the aluminum hydroxide gel in basic aluminum chloride decreases. Although there is no particular lower limit for the alumina concentration, the amount of aluminum hydroxide gel necessary for adjusting the basicity increases as the concentration decreases. The basicity is usually about 20% or more.

In carrying out the present invention, the aluminum hydroxide gel has an alumina concentration (in terms of Al ₂ O ₃ ) of about 5% by weight.
Hereinafter, the mixing amount of the sulfate and the alkali aluminate is appropriately selected so as to be preferably about 2.5% by weight to about 4.5% by weight, and a conventionally known apparatus such as a batch reactor or a continuous reactor is used. And an aluminum hydroxide gel is produced by the mixing reaction. The method of mixing is preferably a method in which an alkali aluminate is added dropwise to a sulfate while stirring. Usually, the dropping time is about 1 minute to about 1 hour, preferably about 1 hour.
Minutes to about 30 minutes.

The present invention is characterized in that the obtained aluminum hydroxide gel is then dissolved in BAC to obtain PAC.

The BAC of the present invention is not particularly limited,
The basicity represented by the formula Al _n (OH) _m Cl _3n-m [(m / 3
n) × 100] is more than 0 and less than 50%, preferably more than 30% and less than 50%. BAC
May be prepared by a conventionally known method, for example, a method of reacting hydrochloric acid and aluminum hydroxide.

In practicing the present invention, dissolution may be performed by any method such as a method of adding BAC to aluminum hydroxide gel and a method of adding aluminum hydroxide gel to BAC. The addition and mixing of the aluminum hydroxide gel and the basic aluminum chloride are preferably performed substantially before the aging of the aluminum hydroxide gel proceeds.
As the aging proceeds, the solubility of the aluminum hydroxide gel decreases. The retention time during which the aging of the aluminum hydroxide does not substantially proceed depends on the basicity and temperature of the aluminum hydroxide gel, and is not unique, but is generally not limited to a hydroxide having a basicity of about 20% to about 70% or less. In the case of an aluminum gel, the aluminum hydroxide gel is formed within about 2 hours, preferably within about 1 hour, more preferably about 20 hours.
Within minutes. In the case of an aluminum hydroxide gel having a basicity of more than about 70%, the time is within about 30 minutes, preferably about 10 minutes, and more preferably 1 minute after the formation of the aluminum hydroxide gel. That is, the reaction is carried out in such a manner that the time from the mixing reaction of the sulfate and the alkali aluminate to the formation (precipitation) of the aluminum hydroxide gel until the mixing with the BAC is within the above-mentioned holding time. still,
BAC is usually used while being heated to about 50 ° C to about 85 ° C.

[0015]

As described in detail above, according to the present invention, in a method for producing polyaluminum chloride obtained by dissolving aluminum hydroxide gel in basic aluminum chloride,
The use of expensive sodium carbonate can be stopped because a readily soluble aluminum hydroxide gel can be obtained without the use of carbonates, and a ventilator that removes carbon dioxide generated during mixing and undissolved water Since the production equipment such as a solid-liquid separation device that removes aluminum oxide gel can be downsized, it is economical in terms of operation and equipment.
Its industrial value is enormous.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the scope of the present invention is not limited by these examples.

Alumina (Al ₂ O ₃ ) concentration [% by weight]: JI
According to the S K1475 ^-1996.

Basicity [%]: JIS K1475
^-According to ¹⁹⁹⁶ .

Soda (Na ₂ O) concentration [% by weight]: JIS
According to the K1201 ^-1950.

Sulfate ion (SO ₄ ²⁻ ) concentration [% by weight]: Gravimetric method based on the production of barium sulfate.

Undissolved gel amount [% by weight]: 500 g sample
Was filtered through a filter paper (5A, manufactured by Advantech Toyo Co., Ltd.), and determined from the residual weight on the filter paper.

Accelerated stability test: A sample was placed in a glass container, sealed, and left standing in a 50 ° C. constant temperature water bath to continue observation.
The time until precipitation occurred was measured.

Example 1 3450 parts by weight of polyaluminum chloride (Al ₂ O ₃ concentration 3.5% by weight, basicity 50%, SO ₄ ^2-9 % by weight) and aluminum sulfate (Al ₂ O ₃ concentration 8% by weight) 1430 parts by weight, and then sodium aluminate (Al ₂ O ₃ concentration 3.6% by weight, Na ₂ O concentration 3.7% by weight) 2450
Parts by weight were mixed dropwise over 12 minutes, and aluminum hydroxide gel (Al ₂ O ₃ concentration: 4.4% by weight, basicity: 61.7%)
I got Mixing was performed at a temperature of 32 ° C.

After the obtained aluminum hydroxide gel was kept for 15 minutes while stirring, the aluminum hydroxide gel was subjected to basic aluminum chloride (Al ₂ O ₃ concentration: 19.degree. C.) at 65 ° C.
5700 parts by weight (3% by weight, basicity 48%) were dropped and mixed over 6 minutes, and the obtained polyaluminum chloride was kept for 1 hour while stirring. The undissolved gel amount at this time was 0.8% by weight. The amount of undissolved gel when the stirring was stopped and allowed to stand for 16 hours was 0.2% by weight. After adding 1060 parts by weight of water to polyaluminum chloride to adjust the Al ₂ O ₃ concentration to 10.1% by weight and the basicity to 51%, the stability over time was examined. 5
As a result of the 0 ° C. accelerated stability test, it was stable for 13 days. The coagulation performance was good.

Examples 2 to 6 In Example 1, the charged amount of aluminum sulfate, the charged amount of polyaluminum chloride, the charged amount of sodium aluminate, the dropping time of sodium aluminate, the temperature at the time of dropping, and the holding time of aluminum hydroxide gel Table 1 shows the BAC drop time.
The procedure was performed in the same manner except that the conditions were changed. In order to adjust the concentration of Al ₂ O _{3 in the} aluminum hydroxide gel, water was mixed with sodium aluminate before dropping and mixing sodium aluminate as necessary. Table 1 shows the Al ₂ O ₃ concentration and basicity of the aluminum hydroxide gel and the solubility of the product polyaluminum chloride.

Example 7 Table 1 shows the test conditions and results. As a result of the 50 ° C. accelerated stability test, it was stable for 9 days. The coagulation performance was good.

Example 8 Table 1 shows the test conditions and results. As a result of the 50 ° C. accelerated stability test, it was stable for 13 days. The coagulation performance was good.

Comparative Examples 1 and 2 In Example 1, the charged amount of aluminum sulfate, the charged amount of polyaluminum chloride, the charged amount of sodium aluminate, the dropping time of sodium aluminate, the temperature during dropping, and the holding time of aluminum hydroxide gel Table 1 shows the BAC drop time.
The procedure was performed in the same manner except that the conditions were changed. In order to adjust the concentration of Al ₂ O _{3 in the} aluminum hydroxide gel, water was mixed with sodium aluminate before dropping and mixing sodium aluminate as necessary. Table 1 shows the Al ₂ O ₃ concentration and basicity of the aluminum hydroxide gel and the solubility of the product polyaluminum chloride.

[0029]

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuyoshi Shimada 4-1-2, Shigino Nishi, Joto-ku, Osaka Asahi Chemical Industry Co., Ltd. No. Asahi Chemical Industry Co., Ltd. (72) Inventor Hiroshi Takahashi 5-1 Sokaicho, Niihama-shi, Ehime

Claims (3)

[Claims] 1. Sulfate and alkali aluminate at a temperature of 50
Alumina concentration (Al ₂
The O ₃ conversion) 5 wt% or less of aluminum hydroxide gel,
A method for producing polyaluminum chloride dissolved in basic aluminum chloride. 2. The method according to claim 1, wherein the aluminum hydroxide gel is dissolved in basic aluminum chloride before the aging of the aluminum hydroxide gel substantially proceeds.
The method for producing polyaluminum chloride according to the above. 3. The method for producing polyaluminum chloride according to claim 1, wherein the sulfate is aluminum sulfate and / or polyaluminum chloride, and the alkali aluminate is sodium aluminate.