JP2002086139A - Water treating method, water treating agent and regenerating method of water treating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treating method, a water treating agent and a method for regenerating the water treating agent which eliminate restrictions on operations and materials by using no corrosive acid and which have high dephosphorization efficiency. SOLUTION: The water treating method is distinguished by bringing water to be treated in contact with the water treating agent which is produced by blending a mixture containing at least one kind among Si-Al-Ca compound oxides or Si-Fe-Ca compound oxides with an aqueous solution, powder or a suspension of oxide or hydroxide or basic salt of an alkali metal and/or oxide or hydroxide or basic salt of an alkali earth metal. The water treating agent is obtained by blending slug containing at least one kind among Si-Al-Ca compound oxides or Si-Fe-Ca compound oxides generated in a steel blast furnace or in a converter with the aqueous solution, powder or the suspension of oxide or hydroxide or basic salt of the alkali metal and/or oxide or hydroxide or basic salt of the alkali earth metal. The method for regenerating the water treating agent is distinguished by that phosphoric acid in the water to be treated is adsorbed and then is brought into contact with water containing an alkali metal and/or an alkali earth metal to elute the phosphoric acid in the water treating method described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment method, a water treatment agent and a method for regenerating a water treatment agent, and more particularly, to a water treatment method having a high dephosphorization effect, a water treatment agent and a method for regenerating a water treatment agent. .

[0002]

2. Description of the Related Art In recent years, the removal of phosphorus contained in water or seawater in closed water bodies where industrial wastewater, domestic wastewater or eutrophication tends to occur is an important factor for global environmental protection. It has become to.

Conventionally, such phosphorus removal involves reacting phosphorus with a metal salt such as an aluminum salt such as aluminum chloride, aluminum sulfate or aluminum hydroxide, or an iron salt such as iron chloride, iron sulfate or iron hydroxide. By coagulation and precipitation as a poorly soluble phosphate, a method of crystallizing phosphorus in the form of hydroxyapatite on a core substance such as phosphate rock or bone charcoal, and a method of removing activated sludge under anaerobic and / or aerobic conditions. It is performed by using biological methods. However, careful control of the process was necessary to stably remove phosphorus and the like at all times.

In a method of coagulating sedimentation, a method of crystallizing phosphorus in the form of hydroxyapatite, and a biological method, an excessive amount of a coagulant, phosphate rock, or the like must be added in order to reliably obtain a certain capture rate. Therefore, there is a problem that a large amount of sludge such as unreacted additives and sludge is generated.

On the other hand, steel-based slag is used as a dephosphorizing agent and an adsorbent. Iron and steel slag is generated when impurities in ore and additives used for smelting are separated or interact with each other during metal refining, and float on the molten metal.

However, the conventional dephosphorization method using slag is a method of simply mixing slag fine powder into the water to be treated, and has a problem that the dephosphorization efficiency is not sufficient.

[0007] In order to improve the dephosphorization efficiency of the dephosphorization method using such slag, a method of activating the slag surface with an acid has been proposed. In addition to the restrictions on the material, the solubility of the slag in acid and the degree of activation were small, so that the dephosphorization efficiency was not significantly improved.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a water treatment method, a water treatment agent and a water treatment agent having high efficiency of dephosphorization without using corrosive acids, eliminating restrictions on operation and materials. It is an object to provide a reproduction method.

[0009]

The above object is achieved by the following invention.

[0010] 1. In a mixture containing at least one of Si-Al-Ca-based oxide or Si-Fe-Ca-based oxide, an alkali metal oxide, a hydroxide or a basic salt, and / or an alkaline earth metal A water treatment method comprising contacting water to be treated with a water treatment agent obtained by mixing an aqueous solution, powder or suspension of an oxide, hydroxide or basic salt.

2. 2. The water treatment method according to claim 1, wherein the mixture is slag generated in a steel blast furnace or a converter, and is in a powdery and / or massive form. 3.

3. Si-Al-Ca generated in steel blast furnace or converter
Slag containing at least one of oxides based on silicon or Si-Fe-Ca, oxides, hydroxides or basic salts of alkali metals and / or oxides and hydroxides of alkaline earth metals Or a water treatment agent obtained by mixing an aqueous solution, powder or suspension of a basic salt.

4. The water treatment method according to claim 1,
After adsorbing phosphoric acid in the water to be treated, the alkali metal and / or
Alternatively, a method for regenerating a water treatment agent, comprising contacting water containing an alkaline earth metal to elute phosphoric acid.

According to the present invention, in addition to the effect of removing and recovering phosphorus from the water to be treated, it is also possible to simultaneously remove substances trapped with phosphorus, for example, organic substances such as heavy metals and humin.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing an example of an apparatus suitable for carrying out the water treatment method of the present invention. In the figure, reference numeral 1 denotes a mixture of water to be treated (raw water) and a water treatment agent to be treated. A mixing tank 2 for adsorbing components such as phosphorus in water is a sedimentation separation tank 2 for separating solids sent from the mixing tank 1 and treated water.

The apparatus for producing a water treatment agent is constituted by at least a slag powder hopper 3, an alkaline tank 4, and an activation tank 5.

The slag powder hopper 3 contains Si (silicon)
-Al (aluminum) -Ca (calcium) -based oxide or
A mixture containing at least one of Si (silicon) -Fe (iron) -Ca (calcium) -based oxide is charged.

This mixture is made of blast furnace slag, converter slag,
Various slags generated in an electric furnace slag and the like can be used, and among them, a steel blast furnace slag or a converter slag is preferable. Such slag is preferable because it can be reused to protect the environment. The slag generated in the steel blast furnace or the converter is preferably in the form of powder and / or lump for easy handling.

As a means for introducing the mixture into the slag powder hopper 3, various powder feeders can be used, and a vibrator may be attached to the hopper for convenience of discharging the powder. .

The alkaline tank 4 contains an aqueous solution, powder or suspension of an alkali metal oxide, hydroxide or basic salt and / or an alkaline earth metal oxide, hydroxide or basic salt. Has been put in. Examples of alkali metal oxides include sodium oxide and potassium oxide, and examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide.Examples of alkali metal basic salts include carbonates. First, a single and / or complex salt exhibiting basicity in contact with water may be mentioned.

Examples of the alkaline earth metal oxide include magnesium oxide and calcium oxide, and examples of the alkaline earth metal hydroxide include magnesium hydroxide and calcium hydroxide. Examples of the basic salt include a carbonate and a simple and / or complex salt exhibiting basicity in contact with water.

The oxides, hydroxides or basic salts of alkali metals may be used alone or as a mixture of two or more. The oxides, hydroxides or basic salts of alkaline earth metals may be used alone or in combination of two or more. These may be used in an aqueous solution, as a powder, or in a suspension.

The activation tank 5 is provided with the slag powder hopper 3 described above.
Is a tank for mixing a powder and / or a lump mixture sent from the above with an aqueous solution, powder or suspension from the alkaline tank 4 to activate the surface of the slag and produce a water treatment agent. A stirrer 50 is provided.

An aqueous solution or suspension of an oxide, hydroxide or basic salt of an alkali metal or alkaline earth metal to be mixed with the mixture (hereinafter also referred to simply as alkaline water).
Is preferably 0.1 to 80% by weight on a dry weight basis, more preferably near a saturated solution.

The amount of the aqueous alkali solution and suspension mixed with the mixture is 50% to 10 times the weight of the mixture (weight ratio).
And more preferably 1 to 3 times. In the case of powder, the mixing amount is preferably at least 1%, more preferably 1%.
0 to 100%.

The water treatment agent produced in the activation tank 5 is sent to the mixing tank 1 by, for example, a metering pump or the like, and is brought into contact with the water to be treated (raw water to be treated). Powders are also mixed into the water to be treated by a quantitative feeder or the like.

The amount of the water treatment agent to be added depends on the concentration of the substance to be removed.
The range is preferably 0 mg / l, more preferably 10 mg / l to 100 m
g / l range.

The contact time of the water treatment agent and the water to be treated in the mixing tank 1 is preferably in the range of several seconds to several hours, more preferably in the range of 10 seconds to 10 minutes.

In the present invention, the water treatment agent activates the slag surface using an alkali, and the activated slag is sent to the mixing tank 1 and comes into contact with the water to be treated, whereby the phosphorus component in the water to be treated is increased. Is adsorbed, and phosphoric acid and the like are efficiently removed.

In the apparatus shown in FIG. 1, the solid content (sludge containing components such as phosphorus) separated in the sedimentation separation tank 2 is drawn out by a drawing means such as a pump, and collected in a recovery tank 6.
Sent to The recovery tank 6 is provided with a stirrer 60.

Alkaline water is supplied from the alkaline tank 4 to the recovery tank 6, and after mixing and stirring, phosphoric acid and the like are recovered in the recovered liquid separation tank 7, and the settled slag is sent to the activation tank 5 again. Reused. The settled slag is dehydrated,
It is also possible to carry it out of the system and use it in another processing system.

Next, another embodiment of the present invention will be described with reference to FIG.

The apparatus shown in FIG.
Are arranged in parallel, and the processing method is the same as that of the apparatus in FIG. In the case shown, the slag packed columns 10, 11,
This is an example in which three 12 are arranged in parallel.

In this embodiment, the slag packed column 1
Raw water can be simultaneously passed through 0, 11, and 12, but is not limited thereto.

For example, an operation method in which raw water is not passed is also possible by setting one of the slag packed columns 12 as a spare. In that case, the treatment is performed on slag packed columns 10 and 1
This is performed with two groups of 1. When regenerating the slag of the slag packed columns 10 and 11, raw water is passed through the slag packed column 12. This is preferable because the phosphorus removal treatment of raw water can be performed continuously even when the regeneration treatment is being performed. Note that, in FIG. 2, the portions denoted by the same reference numerals as those in FIG.

According to the treating agent and treating method of the present invention, the adsorption efficiency of phosphorus is improved, but in addition, the removing efficiency of heavy metals such as arsenic and organic substances such as humin is improved as compared with the conventional method.

[0038]

According to the present invention, it is possible to provide a water treatment method, a water treatment agent, and a method for regenerating a water treatment agent having high adsorption efficiency of phosphorus, arsenic, and the like.

[0039]

The present invention will be described in more detail with reference to the following examples. The present invention is not limited by the embodiments.

Example 1 Using a granulated granulated blast furnace slag, an adsorption and elution test of phosphoric acid in an aqueous solution of sodium hydrogen phosphate was performed. The properties of the granulated blast furnace slag used in the test are as follows.

(Properties of granulated blast furnace slag) (1) Chemical composition (main component) SiO ₂ : 36 wt% Al ₂ O ₃ : 13 to 15 wt% CaO: 38 to 42 wt% MgO: 6 wt% or less (subcomponent element) Ti, K, Mn, S, Na, Fe (trace element) Cr, Zn, Mo, Ni, V

(2) Crystal State X-ray diffraction analysis of the crystal is highly amorphous, and no clear diffraction peak can be observed. When this was heated to 200 to 300 ° C. for several minutes, diffraction peaks such as calcium and / or aluminum silicate appeared.

(3) Particle Size and Pore Distribution The particle size of the present powder is as large as 200 μm to 300 μm,
Fine ones vary greatly by several μm.

The average surface area determined by the BET specific surface area measurement method was about 10 m ² g ⁻¹ .

Further, the pore distribution by the mercury porosimeter was found in the range of 10 ³ to 10 ⁵ ° centered around 10 ⁴ °.

(4) Zeta potential In the vicinity of neutral (pH 7), the zeta potential shows a value of about -20 mV,
The isoelectric point was found between pH 5 and 6. In contrast to the aggregate of polyaluminum chloride having an isoelectric point near pH 8 and having a positive zeta potential near neutrality.

However, active silica used as a coagulation aid has an isoelectric point of pH 5 or less and has a substantially negative zeta potential in ordinary water.

The present powder was considered to have an intermediate behavior between the activated silica aggregate and the polyaluminum chloride aggregate.

(Test) Blast furnace slag fine powder 1 having the above properties
g was tested for supplementing phosphoric acid by the following treatment methods.

(Comparative treatment 1) The solution was directly administered to the water to be treated.

(Comparative treatment 2) 10N sulfuric acid was added, and the mixture was kneaded and administered to the water to be treated.

Example 1 A 15N aqueous sodium hydroxide solution was added, and the mixture was kneaded and administered to the water to be treated.

As the water to be treated, 0.01, 10 mg / l
Aqueous solution of sodium dihydrogen phosphate adjusted to -P concentration 1
One liter was used.

After the administration, the mixture was stirred and allowed to stand, and the concentration of phosphoric acid in the supernatant water was quantified by the phosphomolybdenum blue method (absorptiometry). The suspended part was filtered with 5C filter paper.

In the operation of Example 1, the sodium hydroxide solution was added to the precipitation portion, and the mixture was heated to 50 ° C.
After kneading and standing, the concentration of phosphoric acid in the supernatant water portion was determined. This precipitation part was added again to the water to be treated, and the phosphoric acid trapping property was confirmed.

The above series of tests were performed at room temperature (about 18 ° C.).

Also, in the test of Example 1, before mixing the sodium hydroxide, the slag powder was administered to the water to be treated, and then the recovered slag powder, and then the slag when remixed with sodium hydroxide. After washing the powder with water and drying,
Observation with a scanning electron microscope (SEM)
Surface analysis was performed with PMA.

Table 1 shows the above results.

[0059]

[Table 1]

From the results shown in Table 1, it was clarified that the blast furnace slag powder kneaded with the aqueous solution of sodium hydroxide had excellent phosphoric acid removal performance as compared with the others.

In Comparative Processing 1, no change was observed in the SEM image before and after the slag powder was administered to the water to be treated. It was considered that the slag powder itself without any treatment did not have a function of strongly adsorbing phosphoric acid.

In the comparative treatment 2, it was clear from the SEM image and the EPM that calcium sulfate crystals grew on the surface of the slag powder by sulfuric acid and adsorption of phosphoric acid was hindered.

Example 2 Particles of granulated blast furnace slag of several mm were packed in a packed tower (column), and an experiment for removing phosphoric acid was performed. The chemical composition of the slag used is the same as in Example 1.

The following packing columns were prepared.

Comparative packed tower 1: Untreated granulated blast furnace slag was packed.

Comparative packed tower 2: 10N sulfuric acid was added to the column and kneaded.

Example 2 A 15N aqueous sodium hydroxide solution was kneaded in a column.

An aqueous solution of 10 μg-P / l sodium dihydrogen phosphate was allowed to flow from the upper end of the column into the above column, and the concentration of phosphoric acid in the effluent was determined. Table 2 shows the results of the quantification.

A regeneration experiment was conducted for the case of the second embodiment.

As a result, when a 15N-NaOH aqueous solution was allowed to flow through a column of slag which had been kneaded with alkali (kneaded with a 15N aqueous sodium hydroxide solution), which was considered to have adsorbed phosphoric acid, phosphoric acid was detected from the effluent.

[0071]

[Table 2]

Example 3 A calcium hydroxide suspension was kneaded into a column filled with granulated blast furnace slag and converter slag having the properties shown in Table 3 and mixed with 10 m
A mixture of g / l commercially available kaolin fine powder and 1 mg / l sodium dihydrogen phosphate (dihydrate) was allowed to flow down from the top of the column, and the effluent kaolin turbidity (turbidimetric method) and phosphoric acid concentration (molybdenum) Blue method) and aluminum concentration (IPC-
AES) was quantified.

Table 4 shows the results.

It should be noted that about 5 N
Elution with an aqueous solution of -Ca (OH) ₂ was confirmed.

[0075]

[Table 3]

[0076]

[Table 4]

From the above table, it was found that elution of aluminum did not occur in the converter slag.

Example 4 A 5N aqueous sodium hydroxide solution was added to the converter slag having the composition used in Example 3, kneaded, and packed in a column.

On the other hand, sodium arsenate was added as a test solution to prepare tap water having a concentration of 0.52 ppm as an arsenic element.

The test solution was poured onto a converter slag column,
The arsenic concentration in the effluent was determined. The arsenic concentration in the effluent is 0.01 mg / l-As or less, and about 10 liters of liquid per 1 g of converter slag is treated (outlet As concentration 1 mg / l or less) with respect to the arsenic concentration of the test solution. It was possible.

The converter slag after adsorption of arsenic can desorb arsenic by pouring an acid or alkali solution.
Again, the 5N-sodium hydroxide aqueous solution was poured to recover the arsenic adsorption ability.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus suitable for carrying out a water treatment method of the present invention.

FIG. 2 is a diagram showing another example of an apparatus suitable for carrying out the water treatment method of the present invention.

[Description of Signs] 1: Mixing tank 2: Sedimentation separation tank 3: Slag powder hopper 4: Alkaline tank 5: Activation tank 6: Recovery tank 60: Stirrer 7: Recovery liquid separation tank 10, 11, 12: Slag packed column

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Hamamoto 5-6-4 Tsukiji, Chuo-ku, Tokyo Mitsui Engineering & Shipbuilding Co., Ltd. (72) Inventor Masahiro Saito 5-6-4 Tsukiji, Chuo-ku, Tokyo Mitsui F-term (reference) in Shipbuilding Co., Ltd.

Claims (4)

[Claims] A mixture containing at least one of a Si-Al-Ca-based oxide and a Si-Fe-Ca-based oxide is mixed with an alkali metal oxide, hydroxide or basic salt, and / or A water treatment method comprising contacting water to be treated with a water treatment agent obtained by mixing an aqueous solution, powder or suspension of an oxide, hydroxide or basic salt of an alkaline earth metal. 2. The water treatment method according to claim 1, wherein the mixture is slag generated in a steel blast furnace or a converter, and is in a powdery and / or massive form. 3. A slag containing at least one of a Si-Al-Ca-based oxide or a Si-Fe-Ca-based oxide generated in a steel blast furnace or a converter, wherein an alkali metal oxide, hydroxide or A water treatment agent obtained by mixing an aqueous solution, powder or suspension of a basic salt and / or an alkaline earth metal oxide, hydroxide or basic salt. 4. The water treatment method according to claim 1, wherein the phosphoric acid in the water to be treated is adsorbed, and then contacted with water containing an alkali metal and / or an alkaline earth metal to elute the phosphoric acid. A method for regenerating a water treatment agent.