JPS59449B2 - 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 solutions and to the use of such solutions in water treatment.

In co-pending patent application 35490/74, we describe the process of preparing basic aluminum by reacting an aluminum sulfate solution with calcium chloride and then reacting with a precipitating agent such as calcium carbonate, calcium hydroxide, or calcium oxide. Describes the solution manufacturing method.

We have now discovered that by modifying the above process it is possible to obtain basic aluminum solutions containing phosphate.

According to the invention, an aluminum sulfate solution is reacted with phosphoric acid at an elevated temperature, chloride is introduced by addition of hydrochloric acid or calcium chloride, and calcium oxides and hydroxides are added in order to selectively precipitate calcium sulfate. Alternatively, make the solution basic by adding carbonate, and then make the solution 6
A method for producing a phosphate-containing basic aluminum solution is provided, including the steps of rapidly cooling it to below 0°C.

When such a process is carried out, the loss of aluminum compounds from the solution can be virtually eliminated.

One suitable method of carrying out the first stage of the reaction is to heat phosphoric acid to reflux with an aluminum sulfate solution.

Generally, it is preferred to add the chloride either before or simultaneously with the calcium carbonate, oxide, or hydroxide.

The step of introducing chloride and making the solution basic is at 80°C to 9°C.
It is generally preferred to take place at a temperature in the range of 0°C.

In practice, it is convenient to introduce the chloride as an aqueous calcium chloride solution and the preferred basifying salt, calcium carbonate, as an aqueous slurry.

When a suitable amount of this type of reactant is introduced into an aluminum sulfate/phosphoric acid solution heated under reflux power, the temperature rises from 80°C to 90°C.
There is a tendency to produce temperatures in the range of C, however other means of temperature adjustment into this range may be provided if desired.

After the introduction of the basifying salts, the solution is heated at an elevated temperature, in particular about 60-
It is important to control the length of time held at temperatures above 70°C.

However, it is not recommended to forcefully heat the solution immediately after the introduction of the basifying salts is complete, as this tends to lead to instability of the product.

On a laboratory scale, suitable results may be obtained by allowing the solution to cool naturally immediately after calcium carbonate introduction.

However, for large-scale operations, it is desirable to perform cooling so that the solution temperature drops rapidly to below 60°C.

The temperature of the solution is preferably maintained above about 60° C. for no more than about half an hour after introducing the basifying salt.

Cooling to lower temperatures is believed not to be critical and can be accomplished using any convenient method or apparatus.

By practicing such a method, we have discovered that calcium sulfate precipitates in preference to calcium phosphate.

The molar ratio of phosphate+sulfate to aluminum in the product solution preferably falls within the range of 0.05:1 to 0.3=1.

Particularly useful solutions have substantially all of the sulfate removed and the phosphate to aluminum ratio in the solution is about 0.1.
:1 to 0.15:1.

Desirably sufficient calcium carbonate, oxide, or hydroxide is used to produce a basic aluminum solution having a basicity in the range of 33% to 80%;
5% basicity can be conveniently produced.

Variations in basicity, and therefore in the chloride content of the final solution, are due to calcium chloride and its carbonates, oxides,
Alternatively, it can be obtained by appropriate variation of the amount of hydroxide.

The solution produced by the method according to the invention can be used for water treatment,
That is, it may be used for the treatment of drinking water, sewage or sewage sludge.

Generally, the solution is in fairly dilute form, i.e. Al
It is used in the form of an aluminum content of approximately 1%, calculated as 2O3.

However, for transport and storage purposes it is preferred to produce solutions with an aluminum content in the range 5 to 20%, calculated as M2O3.

In general, a solution prepared by the method according to the invention can be prepared at an M2O3 concentration of 1.0 without substantially compromising its stability.
We have found that it is possible to dilute to -2.0%.

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

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

It is widely known that phosphate ions in solution cause eutrophication, ie, stimulate the growth of plant material and lead to blockage of open canals.

Thus, any treatment of water containing phosphates would be expected to lead to eutrophication problems.

However, we have found that phosphates are generally retained in the flocs that form during water treatment and are therefore not released to any substantial extent into the water supply.

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

Some embodiments according to the invention are described herein in more detail by way of example.

Example 1 In this example, a basic aluminum solution was made by centrifugal heating an aluminum sulfate solution with phosphoric acid at a 0.1:1 molar ratio of phosphoric acid to aluminum for 1.0 hour.

Then an aqueous solution containing 0.7 mole of calcium chloride per mole of aluminum and 0.8 mole of calcium chloride per mole of aluminum.
An aqueous slurry containing molar calcium carbonate was added to the solution at the same time, at a temperature of 80-90°G.

The solution was cooled with stirring for 2 L hours and then filtered.

The basic aluminum solution "e" produced (A12031
0.4%, basic 45.5%) was stable even when diluted to a concentration of 2.0% A1203.

Example 2 In this example, the same procedure as in Example 1 was followed, but
However, the mixture of aluminum sulfate and phosphoric acid was heated centrifugally for 6.0 hours.

After addition of calcium chloride and calcium carbonate and cooling with stirring, calcium sulfate precipitated and was furnaced after the solution had cooled to recycle temperature.

The produced basic aluminum solution (A120311.3
%, basicity 46.1%) was stable on its own as well as upon dilution.

Comparative Example 1 In this comparative example, the same procedure as in Example 1 was adopted, except that the phosphoric acid was heated under reflux with aluminum sulfate for 1 hour and the mixture after addition of calcium chloride and calcium carbonate was It was heated under reflux for an additional 5 hours.

The resulting solution was unstable and precipitation of aluminum compounds occurred.

Example 4 The effectiveness of the solutions prepared in Examples 1 and 2 was tested for sewage sludge dewatering using the Johns sludge test.

Sludges A, B and C were from different treatment plants treating mixed domestic and industrial sewage.

A. Coarse sludge activated excess sludge with a solids content of 5.6%.

B. Crude sludge activated excess sludge with a solids content of 48%.

C coarse sludge + humus sludge with a solids content of 3.4%.

The specific resistance (SR,) for sludge filtration is 4, OX
1012m/kg and 3. The amount of regulator required for the respective reduction to a value of OX 1012 m/kg is given in weight percent aluminum, calculated as Al2O3, added to the dry solids content of the sludge.

In the case of sludge from factory C, SR for the comparative example
The value is 3. OX 1012m/kg- and 2. OX10
It was 12m/kg.

The lower the amount of regulator required, the more effective the product is in dehydration.

F indicates Kokichi, which SR could not reach using this product.

Comparative Example 2 The procedure of Example 4 was carried out, except that the modifier used was basic aluminum chloride, 38.3% Al2O3, 630% basic, which was dissolved in water to
A solution containing approximately 15% of 3 was obtained.

Comparative Example 3 The procedure adopted in Example 4 was carried out, except that the regulator was polyaluminum chloride, commercially available from Tahon Fertilizer Manufacturing Company, Japan, with a basicity of 49.4%.

The results of Examples 1 and 2 and Comparative Examples 2 and 3 are shown below.

Tables 1, 2, and 3 show that the products of Examples 1 and 2 performed as well or better than Comparative Example Products C2 and C3 within the margin of error in the John's Filtration Test. can be seen.

Claims (1)

[Claims] 1. Calcium oxide, The solution is made basic by addition of calcium hydroxide or calcium carbonate, and then the solution is
A process for producing a basic aluminum solution, comprising the formation of a phosphate-containing basic aluminum chloride, characterized by rapid cooling to below 0°C. 2. A process according to claim 1, characterized in that the phosphoric acid and the aluminum sulfate solution are heated under reflux together in the first step. 3. Process according to claim 1 or 2, characterized in that the chloride is introduced into the solution at a temperature of 80-90°C. 4 Calcium carbonate, oxide or hydroxide at 80%
A method according to claim 1, 2 and 3, characterized in that the method is introduced into a solution at a temperature of from 90°C to 90°C. 5. Any one of claims 1, 2, 3, and 4, characterized in that calcium carbonate, oxide, or hydroxide is introduced before or simultaneously with chloride. Method by term. 6 Claims 1, 2, 3, and 4, characterized in that the solution is maintained at a temperature of 60°C or higher for less than half an hour after the introduction of the basifying salt is completed. and the method according to any one of Clause 5. 7 Add sufficient calcium salt to obtain a product solution free of substantially all sulfate and containing phosphate to aluminum in a molar ratio ranging from 0.1:1 to 0.15:1. Claims 1, 2, 3, 4, 5 and 6 are characterized in that
Method according to any one of the paragraphs. 8. Claims 1, 2, 3, 4, 5, 6 and 7, characterized in that the produced solution has a basicity of 40-75%. Method according to any one of the above.