JPS5932404B2 - Method for producing basic aluminum solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of basic aluminum-containing solutions and for the treatment of water, more particularly in the treatment of drinking water, sewage or sewage sludge.

Previously, various methods have been described for the production of basic aluminum-containing solutions, in which macromolecules are formed in which aluminum atoms are crosslinked by polyvalent anions such as sulfates. ing.

For example, in British Patent Specification No. 1222561,
A method is described in which a suitable amount of polyvalent anion is added to a basic aluminum chloride solution and the mixture is preferably aged.

However, we have found that when using sulfate anions, the resulting solutions are no more effective in treating drinking water, sewage, or sewage sludge than basic aluminum chloride solutions without the addition of polyvalent anions. was discovered.

This probably means that the sulfate anion cannot attack the basic aluminum chloride in solution under the given conditions, so that the basic aluminum remaining in solution tends to be of the same molecular weight as the original. I can believe it.

Surprisingly, we have found that the use of a mixture of sulfuric and phosphoric acids in the above process can result in a solution that is more effective in sludge dewatering and water treatment than a comparative solution containing only sulfate. I discovered it here.

According to the present invention, a basic aluminum chloride solution is prepared in which the molar ratio of phosphoric acid and sulfuric acid is in the range of 2:1 to 1:2, and the amount of each acid is 1 % aluminum in the basic aluminum chloride.
A method for producing a basic aluminum solution, which comprises mixing with a mixture of phosphoric acid and sulfuric acid mixed such that the total acid amount is at least 0.05 mole per mole and not more than 0.3 mole per mole of aluminum, and aging this mixture. provided.

In general, the molar ratio of phosphoric acid to sulfuric acid can vary over a wide range;
Conveniently, this molar ratio is in the range 2:1 to 1:2.

In theory, basic aluminum chloride solutions can be treated with very small amounts of phosphoric acid and sulfuric acid, but it is preferred to treat them with at least 0.05 mole of each acid per mole of aluminum.

Generally, the total moles of acid to molar ratio of aluminum is 0.
．． No more than 3:1, often 0.1:1 to 0.2
: It is desirable to fall within the range of 1.

Treatment of basic aluminum chloride solution with such amounts of acid provides a product that can be used to effectively treat aqueous media.

Preferably, the aging is carried out at elevated temperatures.

Generally, the period of ripening to achieve the desired result will vary with the temperature at which the ripening is carried out.

Generally speaking, improved capabilities of sludge dewatering and water treatment can be obtained by adopting a longer aging process, but in practice, the improvements obtained are entirely due to the cost of aging at elevated temperatures. You have to match the increase.

Preferably, the heating is continued at substantially reflux temperature for about 1 hour to about 6 hours, especially about 2 to 3 hours.

It should be understood that aging at lower temperatures requires longer times and therefore aging at substantially ambient temperatures is not commercially viable.

The basic aluminum chloride solution can have a basicity ranging from 33% to 83%.

The effect of introducing sulfate and phosphate ions in this solution is to reduce its basicity.

That will be understood.

It is practical to choose the basicity of the basic aluminum chloride solution and the amounts of phosphoric acid and sulfuric acid used such that the basicity of the final solution is in the range 40 to 75%, especially in the range 60 to 75%. is preferable.

Generally, the basic aluminum-containing solutions according to the invention preferably have an aluminum concentration of 5 to 20%, expressed as Al2O3, for storage and processing.

Within such a range, a solution can be obtained that is stable, ie, without precipitation of aluminum salts over a period of several months.

Such solutions also allow A1203 without loss of stability.
It can also be diluted to aluminum concentrations on the order of 1-2%.

The solution according to the invention can be used for the treatment or conditioning of potable water supplies or sewage, and is particularly directed in particular to the conditioning of sewage sludge.

Potable water treated in this way is often stored in storage tanks, the water extracted from the sludge is recycled into the sewage treatment plant, and the overflow from there is usually dumped into a nearby river or canal.

Phosphate ions in solution lead to eutrophication, ie, stimulate the growth of plant matter, which can lead to blockage of static or free-flowing waterways.

Therefore, it is expected that any treatment of water containing phosphates may result in eutrophication problems.

However, phosphates are generally retained in the flocs formed during water treatment and thus are not released to a substantial extent into the water supply.

In fact, we have discovered that treatment with basic aluminum solutions according to the present invention generally leads to a reduction in phosphate levels in the treated water.

Some embodiments according to the invention are for reference purposes only:
This will be explained in more detail below.

Example 1 In this example, a basic aluminum chloride solution was treated with sulfuric acid and sulfuric acid at a molar ratio of sulfate to phosphate to aluminum (expressed as Al) of 0.1:0.2:1.0. Mixed with phosphoric acid.

The mixture is heated to reflux for 1 hour and then allowed to cool.

The product has an aluminum content of 12.8% by weight (A120
3) and had a basicity of 45.2%.

Stability testing showed that the product was stable for at least 5 months.

Example 2 In this example, the same procedure as above was carried out, but
The molar ratio of sulfate to phosphate to aluminum is o, i:o,
1:1, the mixture was heated to reflux for 2 hours, and the product had an alumina content of 13.2% and a basicity of 48.6%.

The product was also stable for at least 5 months.

Example 3 In this example, the same procedure as in Example 2 was carried out, but
However, the mixture was heated under reflux for 6 hours, and the final product was 14.8
% alumina content and basicity of 47.7%.

This product was also stable for at least 5 months.

Example 4 In this example, Example 1 in sewage sludge dewatering
The effectiveness of products 3 to 3 was determined by John's filtration test.

Sludges A through E were obtained from sewage treatment plants that treat mixed domestic and industrial sewage.

Sludge A and B were samples taken from the same treatment plant but at different times.

The specific resistance (SR) of the P liquid in the sludge is 4. OX
1012m/kg and 3. The product input required to reduce OX to 1012 m/kg is indicated in Tables 1 and 2 in terms of weight % alumina addition to sewage sludge dry solids content.The lower the input, the more dehydrated the product is. Sometimes it is more effective.

F indicates that SR could not be reached when using that product.

The same sludges A through E were dewatered using comparative products CI and C2.

C1 is a commercially available solution of basic aluminum chloride with a basicity of about 60% and C2 is a solution of alumina
It is a polyaluminum chloride solution containing 0.2% by weight and having a basicity of 50% and is sold in Japan by Taki Hijo ■.

The results are also summarized in Tables 1 and 2.

It can be seen from Tables 1 and 2 that, in general, the products of Examples 1-3 exhibit substantially better performance than the comparative product CI.

Furthermore, in many cases, particularly, the products of Examples 2 and 3 were found to outperform comparative product C2 in the John's p-pass test, or were substantially the same within error.

Claims (1)

[Claims] 1. A method comprising the steps of: 1 mixing a basic aluminum chloride solution with an acid precursor of a polyanionic acid; and aging this mixture;
In a method for producing a basic aluminum solution containing 1 to 20% by weight of aluminum expressed as Al2O3 and polyvalent anions, suitable for water treatment or sewage treatment, the molar ratio of phosphoric acid to sulfuric acid is 2:1 to 1: 2, and the amount of each acid is at least 0.205 moles per mole of aluminum in basic aluminum chloride and the total amount of acid is not more than 0.3 mole per mole of aluminum. The above-mentioned method for producing a basic aluminum solution, characterized in that the acid precursor is used as the acid precursor. 2. Process according to claim 1, characterized in that the basic aluminum chloride solution is treated with an acid containing from 11 to 0.2 moles of O per mole of aluminum. 3. A method according to claim 1 or 2, wherein the mixture is aged at substantially reflux temperature. 4. Claim 3, wherein the mixture is aged for 2 to 3 hours.
The method described in section. 5. Any one of claims 1 to 4, wherein the basicity of the basic aluminum solution and the amounts of phosphoric acid and sulfuric acid used are selected such that the resulting product has a basicity of 40 to 75%. The method described in Section 1.