KR950009705B1 - Fluorine adsorbent and its method of manufacture - Google Patents

Abstract

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Description

[Name of invention]

Fluorine Adsorbents and Methods for Making the Same

Detailed description of the invention

The present invention relates to a fluorine adsorbent material and a method for producing the same. More specifically, the present invention relates to materials capable of quickly and effectively adsorbing fluorine contaminants using a minimum amount of material independent of fluorine concentration.

Fluorine exists in its natural state as one of the constituents of fluorspar, cryolite, apatite, etc., its presence not only in groundwater throughout the mining district, but also, for example, in uranium refining, copper refining, lead refining, aluminum alloy production, electronics The release of these minerals from industrial wastewater discharged from product manufacturing, precision instrumentation, plating, air conditioning refrigeration instrument manufacturing, dry-laundry and many other processes can be detected.

In the mine districts mentioned above, groundwater was not available for drinking water supply. Because there was no way to remove fluorine in groundwater. Likewise, in the above-mentioned processes, it is necessary to remove fluorine contaminants at or below environmentally defined concentrations to an extent equivalent to removing other contaminants prior to treating the wastewater.

A number of treatment methods have been proposed to remove fluorine contained in industrial wastewater, and these methods include calcium fluoride treatment, synthetic resin ion exchange, basic treatment by mixing sulfuric acid into the wastewater, or the addition of bottled water to the wastewater. Methods such as dilution by

The calcium fluoride treatment method is effective against flocculation sedimentation, but at high concentrations of fluorine components in water (about 500 mg / l), this method can only remove about half of the fluorine content. The synthetic resin ion exchange method requires pretreatment for ion exchange, which can remove fluorine to such an extent that the concentration of fluorine is reduced to about 20 to 30 mg / l.

It is an object of the present invention to provide an efficient and economical fluorine adsorbent material for removing fluorine from water, thereby overcoming the disadvantages of the prior art.

It is also an object of the present invention to provide a process for preparing such adsorbents. Adsorption materials as described above, provided by the present invention, are based on a predetermined amount of aluminum and silicon and other agents listed herein. As a starting material, allophane can be used and the purification process of converting it to a suitable fluorine adsorbent material can be carried out to meet the above-mentioned purpose. In one embodiment of the invention, the adsorbent material is characterized in that it has the following content (weight).

Al: 15-30%

Si: 15-30%

Fe: 1-2%

Mg, Ca ┐

0.01-0.1% each

Alkali ┘

Remaining components, impurities (inert).

In one embodiment of the invention, the process for preparing the adsorbent begins with pulverizing the starting material allophane, followed by classification, iron removal, dehydration and heat treatment in a closed atmosphere.

As described above, the adsorbent of the present invention is mainly composed of Al and Si, alkali metals such as Fe, Mg and Ca, Na or K, and very low concentrations (0.01 to 0.1% by weight) of S, Te, Sr, Other substances such as Zr and Ba are minor components. Residual impurities include Mn, Cu, Zn, Br, Rb, Sn, Pb, or Sr, each 0.01 to 0.1% by weight. When the concentrations of the other materials are greater than the concentrations indicated, the efficiency of Al and Si that can be actually obtained in the present invention may be impaired.

The required amount of adsorbent depends on the concentration of fluorine. In the case of wastewater having a concentration of fluorine of 50 mg / l, it is preferable to use an adsorbent in an amount ranging from 0.02 to 0.2% by weight relative to the wastewater at a pH condition of about 8 or less.

In addition, the adsorbent of the present invention can be used in either powder or solid pellet form. In both cases, the amount of use is the same regardless of the form, but the adsorption rate in the form of powder is about 10 times faster than that of the solid pellets. For example, for wastewater with a fluorine concentration of 50 mg / l, it takes one minute using powder to lower the fluorine concentration to 1.0 mg / l or less, but 10 minutes using solid pellets.

In addition, the adsorbent of the present invention may be prepared by sintering after mixing each component in a solid state, but it is preferable to prepare by using allophane as a starting material and continuously performing the above-described series of treatment processes.

The starting material allofane is a non-crystalline clay mineral of ash. The allopine is preferably Kanuma-Tuchi earth, which is commonly used in the horticultural field, and is used as an adsorbent and desiccant, i.e., a material for treating organic or inorganic odor emitting elements, and a material for producing heat-resistant insulating materials. Used. Kanuma-Tuchi is a substance found in the Kanuma region of Japan, about 100 km north of Tokyo. Similar earths produced elsewhere may be used in the method of the present invention.

First, the starting material allopine is ground until the product ground with a suitable mill, for example a roller mill, passes through 100-200 mesh sorting. The ground material is then classified to a size of 125 to 150 mesh using a cyclone classifier, for example. The classified product is washed with bottled water to remove sand. At the same time, mucus components are precipitated and removed. Flow with suspended solids to remove contaminant impurities. After that the iron is removed. Iron, the main form of magnetite, is removed using an electromagnetic separator. Thereafter, a dehydration process using a hydraulic press is performed to prepare a cake having a water content of about 50%. The mineral is extruded to a predetermined diameter (e.g. 3.5 mm) with a hydraulic extruder to produce a molded product which is then cut into a predetermined length (e.g. 10 mm). Thereafter, the extrudate is preheated at a temperature of about 200 ° C. for 4 hours. The heat treatment is then carried out in a closed atmosphere. The heat treatment process may be performed in an electric furnace for maintaining the temperature at 1420 to 1480 ° C. for 1 to 2 minutes by adjusting the temperature by, for example, plasma discharge in a sealed atmosphere. The heat-treated product is then cooled in air. In the case of non-molded (powdered) products, on the other hand, the compacted cake is dehydrated and preheated before being ground to the desired size (eg 40-100 μm), which is then milled to a closed atmosphere as described above. Heat treatment.

Each variable is preferably kept within its associated range, specifically within the range of maintaining the heating temperature in the aforementioned heat treatment process. To obtain a high quality product, temperature control must be observed.

In the case of preparing the adsorbent by mixing the aforementioned components, it is preferable to first perform the same steps as described above, starting with dehydration by the hydraulic press after mixing the respective components to form a slurry.

In the aqueous solution, the adsorbent prepared according to the present invention is added, for example, to the wastewater to be treated in an amount of 0.02 to 0.2% by weight, as described above, under normal or ambient temperature, and filtered as necessary. Fluorine can be removed. In the case of treating gas, fluorine can be removed by filtration through an adsorption tower packed with the adsorbent of the present invention.

The effective fluorine removal function of the adsorbents of the present invention is due to the fact that these adsorbents have pores smaller than the diameter of the fluoride molecules. Therefore, fluorine ion sorption occurs due to molecular sieve development, and aluminum fluoride (AlF ₃ ) is produced. When comparing the powder form (diameter 40-100 micrometer) with the extruded form (3.54 mm x 10 mm), there is no difference in fluorine adsorption efficiency. Fluorine is retained in its adsorption bed at room temperature and desorbs by heating.

Hereinafter, the present invention will be described based on some embodiments of the adsorbent prepared by the present invention.

Example 1

100 kg of allophane (composition: 16.12% ignition loss, 37% Al ₂ O ₃ , 38.10% SiO ₂ , 2.67% Fe ₂ O ₃ , CaO 1.81%, MgO 1.12%, alkali 1.02%) did. It was ground until granule size passed through a 100-200 mesh sorter and sorted to a granule diameter of 125-150 mesh. The product was then washed in bottled water at normal ambient temperature. The suspended solids, contaminating impurities and sand were separated and removed, followed by iron removal treatment by magnetic filtration. A dehydration step was performed with a hydraulic press to prepare a cake containing about 50% moisture. The cake was then extruded into 10 mm long pellets under extrusion pressure 10 ton / cm ² . This was heat treated in an electric (plasma discharge) furnace with a temperature controlled from 1420 ° C. to 1450 ° C. for 1 to 2 minutes to yield 60 kg of adsorbent product.

Example 2

Fluoric acid was added to the tap water to prepare 250 mg of sample solution in which the amount of fluorine ion (F ⁻ ) was 1.5 mg / L. Next, 5 g of the adsorbent prepared by the method of Example 1 was added. The treatment method was carried out by stirring for 10 minutes. Thereafter, the concentration of fluorine ions in the filtrate was measured and the results are shown in Table 1 below.

EXAMPLES 3 AND 4

Except that the immersion time was set to 20 minutes (Example 3) and 30 minutes (Example 4), each of the fluorine ion residual concentration was measured after performing the same treatment method as in Example 2. The results are shown in Table 1 below.

Example 5

The same treatment method as in Example 2 was carried out except that the amount of the adsorbent was increased to 10 g. The fluorine solution formed was stirred for 10 minutes and then the fluorine ion concentration in the filtrate was measured. The results are shown in Table 1 below.

EXAMPLES 6 AND 7

The same treatment method as in Example 5 was carried out except that the time for which the adsorbent was immersed in the solution was increased to 20 minutes (Example 6) and 30 minutes (Example 7). Thereafter, the concentration of fluorine ions in the filtrate was measured. The results are shown in Table 1 below.

Example 8

The same treatment method as in Example 2 was carried out except that the fluorine ion concentration was increased to 50 mg / L. After 5 g of adsorbent was added and stirred for 10 minutes, the water was filtered and the fluorine ion concentration was measured. The results are shown in Table 1 below.

[Examples 9 and 10]

The same treatment method as in Example 8 was carried out except that the immersion time was increased to 20 minutes (Example 9) and 30 minutes (Example 10). Thereafter, the concentration of fluorine ions in the filtered water was measured, and the results are shown in Table 1 below.

Example 11

The same treatment method as in Example 8 was carried out except that the amount of the adsorbent substance added to the water was increased to 10 g. After the resulting solution was stirred for 10 minutes, the concentration of fluorine ions was measured. The results are shown in Table 1 below.

[Examples 12 and 13]

The same treatment method as in Example 11 was carried out except that the immersion time was increased to 20 minutes (Example 12) and 30 minutes (Example 13). Thereafter, the respective fluorine ion concentrations were measured. The results are shown in Table 1 below.

TABLE 1

Comparative Example

The method according to Example 2 was carried out except that 100 g of calcium carbonate was added instead of the adsorbent of the present invention. The mixture was stirred for 72 hours. However, this method could not reduce the fluorine ion concentration to 30 mg / L or less.

Comparative Example 2

The method according to Comparative Example 1 was carried out except that 200 g of calcium was added to the same solution as in Example 8, and the solution was stirred for 72 hours. Also in this example, the fluorine ion concentration could not be lowered to about 30 mg / l or less.

The adsorbents of the present invention, consisting of Al, Si, Fe and other elements in the amounts recited herein, are capable of removing fluorine-from high to low concentrations over a wide range of fluorine concentrations. As can be seen from the foregoing, the adsorbent preparation method of the present invention using allophane as a starting material is simpler.

The adsorbents of the present invention have a high capacity for fluorine sorption and have an almost immediate effect such that the adsorption rate is measured in minutes. This substance does not dissolve or soften even when immersed in water for a long time and does not leach into water. Since the adsorbent of the present invention can be used in powder or pellet form, this material can be included as a filler in a suitable cartridge or bag. With this material, the water treatment device can be made small but of high capacity. Despite all these advantages, the cost of the adsorbent of the present invention is low.

The adsorbent of the present invention is nontoxic and environmentally safe, and can be used to satisfy the prescribed water quality (Japan Health and Welfare Regulation 56). Therefore, after removing fluorine, groundwater can be used as a safe drink.

While the present invention has been described in terms of several embodiments, the invention is not limited to these embodiments. Various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention as defined in the appended claims.

Claims (11)

15 to 30% by weight of Al, 15 to 30% by weight of Si, 1 to 2% by weight of Fe, 0.01 to 0.1% by weight of Mg, Ca, and an alkali metal, and the remaining components as impurities Fluorine adsorbent composition. The composition according to claim 1, wherein the composition is composed mainly of Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ , CaO, MgO, and one or both of K and Na. The composition of claim 1 in the form of a powder. The composition of claim 1 in the form of extruded pellets. Starting with an allophane containing Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ , CaO, MgO, and an alkali metal, pulverizing the allopein material and classifying it into a granule size of 125 to 150 mesh; Washing the ground and classified material in water; Removing at least most of the Fe ₂ O ₃ ; Dewatering the washed and iron-removed material; And heat treating the dehydrated material. 6. The method of claim 5, wherein the starting material is a canuma tooth type earth or a material equivalent thereto. The method of claim 5, wherein the Fe ₂ O ₃ is magnetically removed. 6. The method of claim 5 wherein the dehydrated material is extruded into pellets prior to heat treatment. 6. The method of claim 5, wherein the dehydrated material is ground into powder prior to heat treatment. The method of claim 5, wherein said heat treating step comprises maintaining the material at a controlled temperature within a range of 1420 ° C. to 1480 ° C. for about 1-2 minutes. 6. The method of claim 5 wherein said heat treating step is performed by plasma discharge in a closed atmosphere.