JPH11309448A - Arsenic (iii, v), and fluorine adsorbing filter medium and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an arsenic adsorbing material capable of simultaneously removing both trivalent and pentavalent arsenics and a fluorine adsorbing material that makes adjustment of pH before and after the treatment of waste water and drinking water unnecessary, generates less quantity of sludge, and also is high in the duration, and to provide a production method. SOLUTION: The filter medium is produced by a process for firing soil in the temp. range of 200 to 700 deg.C or a process for adding one or more kinds selected from iron salt to the soil and mixing and later firing in the temp. range of 200 to 700 deg.C or a process for adding one or more kinds selected from the iron salt to the soil, mixing, and later adding acid or alkali so that pH after the firing becomes 4 or more, and also firing in the temp. range of 200 to 700 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to arsenic (III, V) which contributes to water purification by adsorbing and fixing arsenic (III, V) and fluorine in waste water and drinking water and reducing the concentration thereof.
V), a fluorine-adsorbing filtration material and a method for producing the same.

[0002]

[Prior Art] Metal refining, pharmaceuticals, pigments, petroleum industry,
The effluent of the semiconductor manufacturing industry, geothermal power plants and hot springs is rich in arsenic. Some drinking water also contains arsenic.

[0003] As a method of removing arsenic that is generally used at present, there is a coprecipitation method of metal hydroxides such as iron, alumina and magnesium. 0.1 ppm of pentavalent arsenate ion
Although trivalent arsenite ions cannot be coagulated and precipitated, they are oxidized with hydrogen peroxide or the like, changed to pentavalent arsenate ions, and coagulated and precipitated. But,
When treating a large amount of water, disposal of a large amount of sediment becomes a problem.

[0004] In addition, adsorption methods using activated carbon and activated alumina, and ion exchange methods using an anion exchange resin have been studied as alternative treatment methods to the hydroxide coprecipitation method. There is a problem in terms.

[0005] On the other hand, fluorine-containing wastewater is subjected to an aluminum electrolytic refining process, a process of producing phosphate fertilizer, a process of cleaning the surface of a metal plate such as stainless steel, a process of cleaning electronic components such as silicon, and research from a chemical laboratory. Wastewater containing fluorine is often discharged from wastewater. In addition, natural water from volcanic areas and some drinking water sometimes contain a large amount of fluorine.

As a method of treating wastewater containing fluorine, there is a coprecipitation method of calcium salt, alumina and magnesium salt. However, in the treatment of wastewater and drinking water,
Adjustment of the pH before and after the treatment and disposal of the precipitate are problems.

The above method for treating arsenic and fluorine requires a post-treatment for removing the generated suspended substances from the treated water, which increases the number of steps and becomes complicated. Also, a continuous drug injection facility is required.

Further, it is difficult to simultaneously remove trivalent and pentavalent arsenic in drainage water and drinking water and to reach the arsenic and fluorine contents below the reference values. Therefore, there is a need for the development of an arsenic / fluorine-adsorbing filter medium which has high durability and can clear the standard value without post-treatment.

[0009]

In the treatment of waste water and drinking water, it is not necessary to adjust the pH before and after the treatment, the generation of sludge is small, and the arsenic adsorbent which can remove trivalent and pentavalent arsenic with high durability at the same time. It is an object of the present invention to solve the above-mentioned problem by using a fluorine adsorbent.

Accordingly, an object of the present invention is to obtain arsenic (III, V) for water purification and a fluorine-adsorbing filter medium by overcoming the above-mentioned drawbacks, and to provide a method for producing the same.

[0011]

SUMMARY OF THE INVENTION The present invention relates to
The object is solved by an arsenic (III, V) and fluorine-adsorbing filtering material and a method for producing the same, comprising a step of firing at a temperature of up to 700 ° C.

[0012] The present invention also provides a step of adding one or more kinds selected from iron salts to soil and mixing the same.
The object is achieved by an arsenic (III, V) and fluorine-adsorbing filter material and a method for producing the same, which comprises a step of firing at 0 ° C.

[0013] The present invention also relates to a step of adding one or more kinds selected from iron salts to soil and mixing the same, and then the pH after firing.
(III, V), a fluorine-adsorbing filter, and a method for producing the same, which comprises a step of adding an acid or an alkali so that the concentration becomes 4 or more, and a step of baking at 200 to 700 ° C. Is the solution.

[0014] The arsenic (III, V), fluorine-adsorbing filter medium and the method for producing the same according to each of the above-mentioned inventions are provided with a step of mixing soil or sediment with the raw material mixture before molding, and then a step of firing. The object is achieved by the characteristic arsenic and fluorine adsorbents and the method for producing the same.

In the following, each arsenic, fluorine-adsorbing filtration material and its manufacturing method will be described in the above order.
The soil used as a raw material in each invention includes volcanic ash soil, red soil, brown forest soil, or all soils that form the crust, such as sediment and construction surplus soil. These soils can be used alone or as a raw material in combination of two or more kinds such as soils.

First, the invention described in claim 1 (hereinafter referred to as "first invention" for convenience) will be described. The first step is a step of firing the soil into a desired shape for the purpose of facilitating the arsenic and fluorine adsorption of the soil. A desired shape may be obtained by performing a forming step before performing the firing step or firing without passing through the forming step and crushing it. In the molding step and the mixing operation leading to the molding step, a necessary amount of water can be appropriately added in order to facilitate their workability.

The firing conditions are 200-700 ° C., 2-6
0 minutes, preferably 300 to 500 ° C
For 5 to 20 minutes.

Next, the invention according to claim 2 will be described. First, the first step is a step of adding and mixing one or more kinds selected from iron salts to soil. The addition amount of these iron salts is 1 to 100 parts by weight (in terms of dry weight).
Preferably it is 30 parts by weight. Examples of the iron salt used in this step include ferrous sulfate, ferric sulfate, ferrous chloride, and ferric chloride. Of these, ferrous sulfate is preferable.

The second step is a firing step. The processing in this step can be performed in the same manner as in the first step of the first invention.

Next, the invention according to claim 3 will be described. First, the first step is a step of adding and mixing one or more kinds selected from iron salts to soil. The addition amount of these iron salts is 1 to 100 parts by weight (in terms of dry weight).
Preferably it is 30 parts by weight.

The second step is a step of adding and mixing an alkali metal or alkaline earth metal oxide or hydroxide so that the pH after calcination becomes 4 to 8 or more, preferably 5 to 7. Examples of the oxide or hydroxide of an alkali metal or alkaline earth metal used in this step include oxides or hydroxides of sodium, potassium, calcium, magnesium and the like, and among these, oxides of calcium Or a hydroxide is preferable. The amount of the alkali metal or alkaline earth metal oxide or hydroxide added,
It is an amount that can make the pH after firing 4 or more. If the addition amount is small and the pH becomes less than 4, iron ions are eluted into the water to be treated, and the persistence of arsenic and fluorine adsorption power is undesirably reduced. The second step can be performed simultaneously with the first step.

The third step is a firing step. The processing in this step can be performed in the same manner as in the first step of the first invention.

The shape and size of the arsenic / fluorine-adsorbing filtration material obtained by each of the production methods are not particularly limited, and can be appropriately selected according to the method of use. Usually, in order to increase the ease of handling and the contact area with water, it is preferable that the particles have a particle size of 0.5 to 5 mm. In order to further increase the contact area with water, it is preferable that the porous material has a total porosity in the range of 60 to 80%.

The arsenic / fluorine-adsorbing filtration material obtained by the production method of the present invention can be used as it is as a water purification material, and may be filled in an appropriate container or supported on a carrier as necessary. Can also be used. Furthermore, the present arsenic and fluorine-adsorbing filter medium can also be used as a flocculant for suspended substances in water.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Examples 1 to 10 and Comparative Example 1 Volcanic ash soil was kneaded with a mixer and extruded to a diameter of 3.
A cylindrical body having a length of 0 mm and a length of about 5 mm was prepared. After drying,
100-1000 in a thermostatic electric furnace
Baking for 20 minutes at ° C. The adsorption filter material thus obtained is a porous granular material.

Next, using the obtained adsorbent, arsenic (II
I, V) adsorption rate test was performed. Table 1 shows the results. The test method for the arsenic adsorption ability is as follows.
g in a 250 ml Erlenmeyer flask and add 16.74 ppm arsenous acid and 20.08 pp to the two flasks.
A 100 ml aqueous solution of m-arsenic acid was added, and the mixture was shaken at 25 ° C for 24 hours. Thereafter, the solution was filtered through a dry filter paper, and the filtrate was measured using an atomic absorption spectrophotometer. The arsenic adsorption rate was determined from the measured values. The test method of fluorine adsorption capacity is as follows: 1 g of the obtained adsorbent is placed in a 250 ml Erlenmeyer flask, and 10 ppm
100 ml of aqueous sodium fluoride solution was added,
Shake for 4 hours. Thereafter, the mixture was filtered with a dry filter paper, and the filtrate was measured using ion chromatography. The fluorine adsorption rate was determined from the measured values.

[0028]

[Table 1]

As is clear from Table 1, the arsenic (III) adsorption rate of the volcanic ash soil was highest at the firing temperature of 300 ° C.
The arsenic (V) adsorption rate was highest at a firing temperature of 500 ° C.
The fluorine adsorption rate was highest at a firing temperature of 500 ° C.

Examples 11 to 20 and Comparative Example 2 Red earth was kneaded with a mixer and extruded to a diameter of 3.0.
A cylindrical body having a length of about 5 mm and a length of about 5 mm was prepared. After drying, in an automatic temperature controlled electric furnace, 100-1000 ° C
For 20 minutes. The adsorption filter material thus obtained is a porous granular material.

Next, using the obtained adsorbent, arsenic (II
I, V) and a fluorine adsorption rate test were performed. Table 2 shows the results. The test method for arsenic and fluorine adsorption capacity is the same as described above.

[0032]

[Table 2]

As apparent from Table 2, the arsenic (III, V) adsorption rate of the red soil was highest at the firing temperature of 300 ° C. The fluorine adsorption rate was highest at a firing temperature of 300 ° C.

As can be seen from Tables 1 and 2, arsenic (II
I, V), since the fluorine adsorption rate is higher than red soil,
Volcanic ash soil is desirable as a raw material for arsenic (III, V) and fluorine adsorbents.

Examples 21 to 22 and Comparative Examples 3 and 4 10 g of ferrous sulfate was added to 37.5 g of each soil and kneaded. Next, it was extruded to form a columnar body having a diameter of 3.0 mm and a length of about 5 mm.
Baking at 0 ° C. for 20 minutes. The firing temperature of the fluorine adsorbent was 400 ° C. The adsorptive filter material thus obtained was a porous granular material, and the total porosity was 73%.

Next, an arsenic (III, V) and fluorine adsorption rate test was conducted in the same manner as in Example 1 using the obtained adsorption filter material. Table 3 shows the results.

[0037]

[Table 3]

As shown in Table 3, the adsorption rates of arsenic (III, V) and fluorine in Examples 21 to 22 were higher than those in Comparative Examples 3 and 4. Particularly, as in Example 22, sulfuric acid in red-yellow soil was The addition of ferrous iron significantly increased the arsenic (III, V) and fluorine adsorption rates.

Examples 23 to 24 and Comparative Examples 5 and 6 10 g of ferrous sulfate was added to 37.5 g of each soil, and then 2.5 g of calcium hydroxide was added, followed by kneading. Next, it was extruded to form a columnar body having a diameter of 3.0 mm and a length of about 5 mm.
Baking at 0 ° C. for 20 minutes. The firing temperature of the fluorine adsorbent was 400 ° C. The adsorptive filter material thus obtained is a porous granular material (pH = 6, pH value when 10 g of the adsorptive filter material is suspended in 25 ml of pure water), and the total porosity is 73%. Was.

Next, a test for the arsenic (III, V) and fluorine adsorption rates was performed in the same manner as in Example 1 using the obtained adsorbent. Table 4 shows the results.

[0041]

[Table 4]

As shown in Table 4, the arsenic (III, V) and fluorine adsorption rates in Examples 23 to 24 were higher than those in Comparative Examples 5 and 6, and in particular, the arsenic (III, V) and fluorine The adsorption rate was further increased than in Example 22 by the addition of calcium hydroxide.

Examples 25 to 26 Using the adsorbent prepared in Example 23, an adsorption sustainability test of arsenic (III) was conducted in a column experiment. 10 g of the adsorbent was put into the column 1, and a 0.50 ppm arsenic (III) solution was continuously injected using a metering pump, and the arsenic concentration of the inflow water and the outflow water was measured every day. In addition, the space inflow velocity (SV is the ratio of the volume of the effluent per hour to the volume of the adsorption filter material per hour) was 0.1. 10 g of the adsorbent was placed in column 2 and 5.00 ppm of arsenic (II
I) The solution was continuously injected, and the arsenic concentration of the inflow and outflow water was measured every day. The space inflow velocity (SV) is 0.2
Met. Table 5 shows the results.

The test method for arsenic was measured by atomic absorption spectrophotometry.

[0045]

[Table 5]

As shown in Table 5, the arsenic (III) adsorption capacity of the adsorbent prepared in Example 23 was remarkably high at both low and high concentrations, and it was found that the adsorbent was capable of adsorbing for a long time. Also, it was able to clear the arsenic concentration of drinking water specified by Japan of 0.01 ppm.

Examples 27 to 28 Using the adsorbent prepared in Example 23, a fluorine adsorption test was conducted. 1.0 ppm, 10.0 ppm in 1 g of adsorbent
Was added and shaken for 10 minutes.
Then, it filtered and measured the fluorine concentration. Table 6 shows the results.

The test method for fluorine is described in JIS K0102.
The method was performed according to the ion electrode method.

[0049]

[Table 6]

As shown in Table 6, it was found that the adsorption capacity of fluorine in Examples 27 to 28 was high at both low and high concentrations, and that the adsorption was possible in a short time.

[0051]

The arsenic (II) produced from the soil according to the present invention
I, V), fluorine adsorption filter media, arsenic, fluorine adsorption,
It has excellent fixing ability and can be used as a filtering agent and a flocculant. Further, the adsorption filter material does not disintegrate or suspend in water due to firing. In addition, the effect lasts for a long time, and is very useful as a water purification material for drainage water and drinking water.

Claims (3)

[Claims] 1. An arsenic (III, V), fluorine-adsorbing filter and a method for producing the same, comprising a step of firing the soil at 200 to 700 ° C. 2. An arsenic (III, V), fluorine adsorption filtration comprising a step of adding and mixing at least one selected from iron salts to soil, and a step of firing at 200 to 700 ° C. Material and its manufacturing method. 3. A step of adding and mixing one or more kinds selected from iron salts to soil, a step of adding an acid or an alkali so that the pH after firing becomes 4 or more, and a step of adding 200 to 7
An arsenic (III, V), fluorine-adsorbing filter and a method for producing the same, comprising a step of firing at 00 ° C.