KR100698672B1 - Adsorbent and process for producing the same - Google Patents

Abstract

Compared with the conventional adsorbent, boron, arsenic, and fluorine have excellent adsorption performance, and even when their concentration is low, they function effectively, have a long service life, easy maintenance, and no eluent or resin component eluting. It is an object to provide an arsenic adsorbent. The adsorbent is an arsenic adsorbent composed of a rare earth element hydroxide and / or a hydrous oxide and a water-resistant polymer resin covering the surface thereof, wherein the rare earth element hydroxide and / or hydrous oxide has a central cavity and a fine pore around it, and the rare earth A boron, arsenic, and fluorine adsorbent, wherein the polymer resin covering the surface of the elemental hydroxide and / or the hydrous oxide is a porous skin layer.

Description

Adsorbent and its manufacturing method {ADSORBENT AND PROCESS FOR PRODUCING THE SAME}

The present invention relates to an adsorbent for adsorbing at least one harmful substance of the group consisting of boron, arsenic and fluorine contained in water, and a method for producing the same.

Under natural conditions or by plant wastewater, water degradation in lakes, swamps, rivers and groundwater, particularly soils and water pollution caused by harmful boron, arsenic and fluorine compounds, has been recognized.

Boron is widely distributed in the natural world and may be included in seawater, volcanic groundwater, and hot spring water. In addition, it may be contained in wastewater from a factory manufacturing process, waste incinerator seyeon wastewater, geothermal power generation wastewater, and the like.

Recently, boron and fluorine have been added as an environmental standard item regarding the protection of human health regarding water pollution of public waters and groundwater. Boron is an essential element in the growth of plants, but it is known that when excessively present, boron adversely affects the growth of plants. In addition, the human body is not always clear, but even if low concentrations continue to be ingested, it is pointed out that it may cause health problems such as a decrease in reproductive function. Some establishments allow for strict drainage of less than / L.

In addition, in the field of semiconductor manufacturing, with the high integration of semiconductor devices, pure water is required to be greatly purified along with production machines, gases, and chemicals used in the manufacturing process, and ultrapure water, and sometimes ultrapure water. Extremely high-purity water, such as the case called ", is also required.

As a method of treating boron-containing wastewater in the water as described above, a method of removing boron as an insoluble precipitate fixed with boron fixative, a method of adsorbing with an adsorbent such as boron selective chelate resin, or a method of treating by reverse osmosis membrane Etc. are known.

However, both of these methods have problems.

For example, aluminum sulfate, calcined lime, and the like are often used for the boron fixative as a method of removing boron as an insoluble precipitate. However, such boron fixative is poor in boron removal efficiency, and the amount of flocculant added is reduced in order to reduce the boron concentration. It is necessary to increase, which causes a large amount of sludge. Although zirconium is used as a boron fixer, the same problem as the boron fixer mentioned above arises (for example, refer Unexamined-Japanese-Patent No. 10-277563).

In the boron removal method using an ion exchange resin, boron selective chelate resin (registered trademark Amberlite IRA-743, manufactured by Rohm and Haas Corporation, registered diamond diaion CRBO2 manufactured by Mitsubishi Chemical Co., Ltd.) is mixed with a polystyrene carrier which is a synthetic resin. There is a way to remove it. In this method, since the support polystyrene is hydrophobic, boron dissolved in water is difficult to diffuse to the inside of the support, and the adsorption capacity is low and the adsorption rate is low. In addition, when the concentration of boron in water is 5 ppm or less, the anion exchange resin and the chelate resin have a problem that boron selectivity and adsorptivity decrease in a short time, and the heat resistance of the resin is low, so that it cannot be used at a high temperature of 70 ° C.

Also, a weakly basic ion exchanger is prepared by preparing an N-glucamine exchanger and its free base or strong base ion exchanger in salt form to remove boron of pure water and ultrapure water for semiconductor manufacturing. (See, for example, Japanese Unexamined Patent Publication No. 8-238478). However, even in this method, the resin elutes in water, there is an increase in the content of the containing group carbon (TOC), the boron selectivity and the adsorptivity decrease in a short time, and the heat resistance of the resin is low so that it cannot be used at high temperatures.

In addition, in the method of removing boron in water by the reverse osmosis membrane method, since the removal rate with respect to the boron compound of the said membrane | membrane is low, in order to make it below the drainage regulation value, a multistage apparatus is needed, operation becomes complicated and excessive, etc. There is a drawback.

In addition, boron adsorbents containing a hydrous oxide of a rare earth element as a powder or contained in a hydrophilic polymer material (see, for example, Japanese Patent Application Laid-Open No. 3-22238, Japanese Patent Application Laid-Open No. 63-24431), a zirconium compound (See, for example, Japanese Patent Application Laid-Open No. 2002-38038). However, in order to achieve removal of trace boron and even removal of organic matter in the water to be treated, a rare earth element-containing hydrous oxide is contained in a hydrophilic polymer material. In the boron adsorbent, the hydrophilic resin melts or the adsorption property of boron to the hydrous oxide of the rare earth element is not sufficient, and boron cannot be removed efficiently. Even if one of the hydrous zirconium oxides is contained in the polymer material, the adsorption capacity of boron to the zirconium compound is low, and the boron removal ability is insufficient.

That is, the boron adsorbent which has high heat resistance, is hard to deteriorate, and can remove even trace boron has not existed until now.

In addition, arsenic among the causative agents of soil pollution elutes due to rain or infiltration of groundwater, which may cause secondary environmental water pollution. Particularly, arsenic in the ground becomes the five-valent scattering ion and the three-valent arsenic acid ion, and it is easy to elute, and report data "the 2002 groundwater quality measurement result" of the Environment Agency (Ministry of Environment, Environment and Environment Bureau) According to the Soil Environment, Groundwater and Geoenvironmental Office, November 27, 2003), 1.5% of the 5,269 wells surveyed had arsenic concentrations exceeding the groundwater quality standard (0.01 mg / l). Much higher than other pollutants. Arsenic has carcinogenicity and causes chronic poisoning after long-term drinking. In the natural world, arsenic is sometimes detected in hot spring water and mine runoff, or in groundwater and water. The water quality standard is expected to be 0.025 mg / l or less in Canada, and the US Environmental Protection Agency will make 0.050 mg / l or less in 0.01 mg / l or less. At a reference value, arsenic concentration is 0.01 mg / l or less, and when arsenic concentration in water exceeds this, it is necessary to remove arsenic from water.

As a conventional method of removing arsenic in water, a coagulation sedimentation method (coprecipitation method) and adsorption method are mainly mentioned. In the coagulation sedimentation method (coprecipitation method), inorganic coagulants such as aluminum salts and iron salts are added, and the pH is adjusted to neutral to form flocculation flocks of metal hydroxides. Remove it. Suspensions, heavy metal ions, etc. precipitate with this fructo. At this time, arsenic is also collected in the flocculated fructose and precipitated. The precipitate is removed by gravity separation or the like.

Agglomeration sedimentation method (coprecipitation method) which is generally used as a arsenic removal treatment method adds inorganic coagulants such as aluminum salts and iron salts in accordance with the turbidity mass of the water to be treated. Administration of a flocculant is required. In addition, there is a drawback in that it takes a long time to remove the arsenic-collected flocculation floc before settling in the sedimentation basin or sedimentation tank. There is a drawback to the complexity of manipulating. In some cases, a separately prepared polymer flocculant or the like may be added for the purpose of promoting sedimentation, but by adding adjustment of the inorganic flocculant and the polymer flocculant, a bulky sludge amount containing arsenic above the turbidity of the water to be treated is generated. There is a drawback that the processing requires more complicated work. In addition, in the coagulation sedimentation method (coprecipitation method), since trivalent arsenic acid cannot be directly harvested, there is a drawback that it is not possible to harvest it without adding an oxidizing agent such as sodium hypochlorite as a pretreatment and changing the form to pentavalent arsenic acid.

Japanese Patent Application Laid-open No. Hei 8-206663 discloses a treatment method for separating a coagulation fruct composed of a metal hydroxide and arsenic produced by coprecipitation by adding a coagulant to an ultrafiltration membrane or a microfiltration membrane. This method makes it possible to compact the installation area of the treatment plant, while the amount of flocculant input is not changed from the conventional flocculation sedimentation method, but the ultrafiltration membrane or the precision of the sludge containing a large amount of flocculant flocks composed of suspended solids, metal hydroxides and arsenic. In order to filter by a filtration membrane, there exists a fault that it requires frequent washing | cleaning of a filtration membrane. There is also a drawback that requires more complicated operations for the treatment of large amounts of sludge, including arsenic. In addition, in the method for removing arsenic of the invention described in this Japanese Patent Laid-Open Publication, since a large amount of flocculant is used, the flocculation fruct pH shifts to the acidic side, and the flocculation floc causes some hydrolysis to release the arsenic which has been removed. Another drawback is that the arsenic concentration of the filtered water cannot be reduced by easily passing through the ultrafiltration membrane or the microfiltration membrane.

As the adsorption method, a method of removing by contacting treated water containing arsenic with an adsorbent and adsorbing arsenic is generally used. Examples of the adsorbent include natural soil and activated metal compounds such as activated carbon, activated alumina, manganese dioxide, titanic acid, zirconium hydrate, lanthanum, yttrium and cerium, which are used as particulate matter having a diameter of 1.0 to 2.0 mm.

In the adsorption method, when activated metal compounds such as activated alumina, activated carbon, or titanic acid, zirconium hydrate, lanthanum, yttrium, cerium, etc., generally remove the adsorbent due to the arsenic adsorption capacity, the adsorbent is periodically replaced. There is a drawback that the frequency of regeneration is increased.

Among the adsorbents conventionally used, in particular, activated alumina is an adsorbent having a property that residual arsenic in the drainage increases in proportion to the water flow rate, and arsenic leakage starts relatively soon after the adsorption treatment starts. There was a drawback that the frequency of adsorbent replacement or regeneration maintenance was cumbersome.

In addition, in consideration of the arsenic adsorption rate of the adsorbent, it is necessary to increase the contact time with the water to be treated as much as possible, and a special column or an adsorption tank is required, and thus there is a disadvantage that the treatment efficiency of arsenic cannot be increased.

In view of this situation, the invention described in Japanese Patent Application Laid-Open No. 2000-70923 provides a neutralizing means installed downstream of the adsorption tower, an adsorbent and an adsorbent to neutralize the weakly acidic treatment liquid in order to quickly and efficiently remove arsenic in the water to be treated. Although a arsenic removal apparatus has been proposed in which a filter is provided downstream of the neutralizing means for trapping debris, it is difficult to say that the object has been sufficiently achieved because the adsorption capacity of the adsorbent used is weak.

Rare earth-based adsorbents such as lanthanum, which are considered to have a high adsorption amount, have a drawback that when the amount of adsorbed arsenic compounds is influenced by the arsenic concentration in water, the equilibrium adsorption amount decreases rapidly when the arsenic concentration is 1.0 mg / l or less. . Moreover, in activated alumina and activated carbon, there existed a fault that equilibrium adsorption amount was low compared with rare earth type adsorbents, such as lanthanum.

The invention described in Japanese Patent Application Laid-Open No. 2000-24647 proposes a method for adsorbing and removing arsenic, which is characterized by using 5 to 60% by weight of a rare earth metal oxide or hydroxide on an alumina carrier as the adsorbent. The adsorption capacity of was weak, and it was difficult to achieve the purpose sufficiently.

Although the invention described in Japanese Patent Application Laid-Open No. 4-45213 proposes an arsenic adsorbent characterized by using 5 to 50% by weight of a hydride oxide of a rare earth metal on an organic polymer carrier as an adsorbent, an organic polymer carrier Hydrophilic resin was used, and there existed a fault which hydrophilic resin elutes at the time of initial water passage. In addition, although the air column velocity at the time of water passage is assumed to be about 10 l / hr in the Example, when the air column velocity is raised beyond that, there is a drawback that water does not sufficiently penetrate into the adsorbent, resulting in a decrease in the adsorption amount. .

In addition, in the adsorbent of the type using a hydrophilic resin, not only the adsorbent described in Unexamined-Japanese-Patent No. 4-45213, the washing | cleaning process of the adsorbent for removing the low molecular weight component in the resin which is an initial elution | floor part is prepared additionally. In addition, there is a drawback that the final treatment with activated carbon is necessary in addition to the treatment with arsenic adsorbent during actual use in order to use the beverage.

In addition, fluorine refers to wastewater from a semiconductor manufacturing process, wastewater generated from waste incineration plants, ash sewage discharged from a thermal power plant, and sewage wastewater discharged from a floor cleaning waste treatment plant or a waste incineration plant. In many cases, the backwater contains fluorine and other harmful and pollutants.

The fluorine emission standard is currently 8 ppm, but the regulations are being tightened further, such as 0.8 ppm in the most restrictive municipal regulations.

Naturally, it is necessary to separate and remove the harmful substances in these wastewater. Separation and removal of fluorine compounds in the waste water is carried out by neutralizing agglomeration and precipitation by adding calcium compounds as poorly soluble compounds, flocculation and precipitation using iron compounds, using alkaline anion exchange resins, or using aluminum salt chelate resins. Ion-exchange resin method (Japanese Patent Publication No. 57-107287) or ion-exchange resin method using zirconium-supported cation exchange resin (Nihon Chemical Co., No. 379, 1981), a method of adsorbing and separating an activated alumina poorly soluble material (Japan Patent Publication 2002-86160), adsorption methods such as adsorptive separation treatment such as a method of using a hydrated oxide of rare earth elements (Japanese Patent Publication No. 61-187931), a method of using a rare earth metal supporting resin (Japanese Patent Publication No. 61-192340), and the like. Several separation treatment methods have been proposed and implemented.

The method for treating fluorine-containing wastewater, which is aggregated and precipitated by a compound such as quicklime or slaked lime of the calcium compound, in the case of separating high concentrations of dissolved fluorine or heavy metals from the wastewater, depending on the concentration thereof, adds two stages of the flocculant. Although coagulation sedimentation is preferably used, the complexity of the two-stage operation is not avoided, and in addition, if the wastewater for harmful and pollutants such as fluorine is removed to a low concentration (for example, 8 mg / L based on water quality), In addition, by adding subsidiary materials such as aluminum and iron salts, or by circulating the species of calcium fluoride, low-density treatments are carried out, but defects requiring subsidiary materials and a large amount of mud resulting from the separation operation The treatment of sludge is a drawback. In addition, in order to use a calcium compound or an iron compound which is most often used to remove fluorine compounds, a large scale is generated, and there is a drawback that the burden of maintenance operation of the separation device increases. Although the method of using magnesium hydroxide as a method of reducing this sludge dewatering cake is also described in Unexamined-Japanese-Patent No. 2003-47972, there existed a fault which the operation complexity increases further.

In addition, the ion exchange resin method is commercially available, for example, Uniselect UR3700 manufactured by Unitika, or trade mark Olite F containing zirconium oxide manufactured by Organo, etc. There is a defect that elemental zirconium oxide is eluted and the resin is crushed finely, and there is a defect that the replenishment of resin by the consumption of resin deterioration is necessary in a large amount, and also a defect that requires a specific device, or in order to maintain the adsorption capacity There existed a fault which an exchange frequency becomes high, and a fault which is weak in resin deterioration and acid resistance by the property of resin.

The activated alumina method also has a gel-like aluminum hydroxide, which has a drawback in low adsorption capacity that does not sufficiently adsorb fluorine in the case of low concentration fluorine (20-50 mg / L concentration), and after the adsorption, a treatment recovery operation sludged with a flocculant is performed. There was a flaw in the complexity. In the above method, a rare earth metal supporting resin is promising among them. However, since the rare earth element of the adsorbent in the resin elutes into the wastewater treatment solution, there is a drawback that it becomes an empty shell of the resin and does not adsorb fluorine.

In addition, the adsorbent of Japanese Patent Application Laid-Open No. 2-2612 also has a defect in that a large amount of cerium is eluted in an acidic region, so that fluorine adsorption performance is required, but a large amount of replenishment of resin due to deterioration is required.

In addition, when treating wastewater of a semiconductor or the like using a conventional adsorbent, a redox substance may be mixed in the wastewater. For this reason, although neutralization precipitation sedimentation process is performed for the oxidation reduction substance using sodium hypochlorite etc., a trace amount of sodium hypochlorite will remain in the waste water after separation process.

Since the remaining sodium hypochlorite deteriorates the polymer resin of the previous ion exchange resin, the adsorbent deteriorates and elutes along with the resin deterioration, resulting in a decrease in adsorption capacity. Although rationalization of wastewater treatment containing fluorine has been technically examined from all angles regardless of the type and the magnitude, it has not been possible to suppress all of the aforementioned drawbacks.

Disclosure of the Invention

Under these circumstances, the present invention has excellent adsorption performance of boron, arsenic, and fluorine present in water compared to the conventional adsorbent, and effectively functions even when the concentration is low, and thus has a long service life and easy maintenance. In addition, since no adsorbent or polymer substance is eluted in water, it is an object of the present invention to provide the adsorbent, which is also unnecessary as a secondary purification means for removing them.

The present inventors have diligently researched, by using rare earth element hydroxides and / or hydrous oxides as boron, arsenic, and fluorine adsorbent components, and using them as polymer resins, particularly polymer resins having water resistance. By covering with a thin layer, that is, a skin layer, and having a structure containing a large amount of rare earth element hydroxides and / or hydrous oxides with many voids in the skin layer, a large amount of adsorbent component can be included, The present invention has been found to cause a significant improvement in the adsorption capacity of harmful substances.

That is, this invention relates to (1)-(6) as follows.

(1) An adsorbent containing at least one of the group consisting of rare earth element hydroxides and hydrous oxides which adsorb and remove these harmful substances from water containing at least one harmful substance of the group consisting of boron, arsenic and fluorine. And a porous membrane of a water-resistant polymer resin covering at least one surface of the group consisting of the rare earth element hydroxide and the hydrous oxide, and comprising an assembly having a central cavity and a fine void around it. The adsorbent.

(2) The adsorbent according to (1), wherein the adsorbent according to (1) contains at least one of a group consisting of 600 parts by weight or more of rare earth element hydroxides and hydrous oxides per 100 parts by weight of the water resistant polymer resin.

(3) The adsorbent according to (1) or (2), wherein the polymer resin is a resin selected from a fluororesin and an acetalized polyvinyl alcohol-based resin.
(4) The fluorine adsorbent according to the above (1), wherein at least one of the group consisting of rare earth element hydroxides and hydrous oxides has a crystallite diameter of 50 to 200 kPa.

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(5) At least 1 type of the group which consists of a rare earth element hydroxide and a hydrous oxide adjusted to moisture content 1-30 weight part with respect to 100 weight part of at least 1 type of group which consists of a rare earth element hydroxide and a hydrous oxide is mentioned with water-resistant polymer resin A dispersion is prepared by mixing with an organic solvent that dissolves a resin or by mixing with an organic solvent solution having a water-resistant polymer resin dissolved therein, and water-resistant at least one surface of the group consisting of the rare earth element hydroxide and a hydrous oxide from the dispersion. A method for producing at least one adsorbent of the group consisting of boron and arsenic, wherein the porous membrane of the polymer resin is coated to produce particles having a structure having a central cavity portion and a fine void portion around it.

(6) Rare earth elements having a crystalline diameter of 50 to 200 Pa by heating and maturing at least one kind of the rare earth element hydroxide having a water content of 1 to 40% by weight and a hydrous oxide at 300 ° C to 600 ° C for 1 hour to 10 hours. At least one member of the group consisting of hydroxides and hydrous oxides is mixed with a water-resistant polymer resin, or mixed with an organic solvent solution in which the water-resistant polymer resin is dissolved to prepare a dispersion, and the rare earth element hydroxide and water-containing oxide from the dispersion. A method for producing a fluorine adsorbent, characterized in that the porous membrane of the water-resistant polymer resin covers at least one surface of the group consisting of particles, and the particles are produced in a structure having a central cavity portion and a fine pore portion surrounding them.

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BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the boron adsorption performance of this invention, and is a relationship diagram of a water passage ratio and the processing liquid boron concentration (mg / L) (Example 1, Comparative Example 1).

2 is a relationship diagram between boron adsorption amount (g / g-CeO ₂ ) and liquid phase B concentration (mg / L) (Example 2, Comparative Example 2).

Fig. 3 is a diagram showing the relationship between the water passage ratio and the treatment liquid boron concentration in the presence of ions other than boron of the present invention (Example 3, Comparative Example 3).

4 is a relationship diagram between the liquid boron concentration (mg / L) and the adsorption amount (g / L) (Example 4).

Fig. 5 is a diagram showing the arsenic {As (V)} adsorption performance of the present invention, and is a diagram showing the relationship between the flow rate ratio and the treatment liquid arsenic concentration (mg / l).

Fig. 6 is a diagram showing the arsenic {As (III)} adsorption performance of the present invention, and is a diagram showing the relationship between the flow rate ratio and the treatment liquid arsenic concentration (mg / l).

7 is a relation chart of the water flow magnification and the treatment liquid cerium concentration of the present invention.

Fig. 8 is a relation diagram of liquid arsenic concentration (mg / l) and arsenic adsorption amount (g / l) of the present invention.

9 is a relationship diagram between liquid pH and arsenic adsorption amount (mol / l) of the present invention.

10 is a relationship diagram between SV (l / hr) and arsenic removal rate of the present invention.

11 is a schematic diagram showing the internal structure of the adsorbent of the present invention.

Fig. 12 is a cross-sectional photograph (100 times) of internal ratio of the adsorbent of the present invention.

Best Mode for Carrying Out the Invention

This invention is demonstrated concretely below.

The boron, arsenic and fluorine adsorbents of the present invention are a mixture of a water-resistant polymer resin, a rare earth element hydroxide and / or a hydrous oxide.

The mixture contains rare earth element hydroxide and / or hydrous oxide in a proportion of 600 parts by weight or more per 100 parts by weight of the polymer resin. If the rare earth element content is less than 600 parts by weight, the adsorption amount of boron, arsenic, and fluorine is insufficient. On the other hand, the upper limit is basically not limited from the viewpoint of the adsorption capacity of the adsorbent, and the higher the amount of the rare earth element hydroxide and / or the hydrous oxide, the better. However, from the standpoint of the durability of the adsorbents of boron, arsenic, and fluorine, 5000 parts by weight or less are preferred, more preferably 3000 parts by weight or less, still more preferably 1000 parts by weight or less, and still more preferably 800 parts by weight or less. .

In the adsorbent of the present invention, the porous membrane of the water-resistant polymer resin covers the rare earth element hydroxide and / or the hydrous oxide, and the rare earth element hydroxide and / or the hydrous oxide therein have a central cavity and a fine void around it.

The shape of the mixture may be in the form of particles, or may be a shaped body in which water can pass. What is necessary is just a structural form which can use these mixtures, without damaging a water supply. Even if it is a network shaped molded object, what is necessary is just to meet a target subject. Moreover, as long as it is a substantially uniform round particle shape, an average particle diameter of 0.2 mm-5.0 mm is used preferably. More preferable particle diameter is 0.5 mm-2.5 mm. When the particle diameter is 0.2 mm or less, the filling density is high and the water resistance is high, and workability tends to be inferior. When the particle size is 5.0 mm or more, the contact area per unit time of the arsenic-containing water and the particulate matter is likely to decrease, resulting in boron and arsenic. The adsorption capacity of fluorine tends to be low.

The granular molded body was obtained by pouring a mixed liquid obtained by dispersing a powder of a rare earth element hydroxide and / or a hydrous oxide and a high molecular resin in a solvent in a drier into a particle maker. The obtained granular molded body was washed with water until the elution of the solvent was not allowed.

As the water-resistant polymer resin used for the adsorbent of the present invention, an organic polymer polymer resin or a derivative of these resins having water resistance that is more heat resistant than anion exchange resin or chelate resin and does not elute in water, and the number average molecular weight is 500 or more Preferably it is 2000 or more. A water-soluble hydrophilic resin is not preferable from the point of eluting, and elution becomes large and there is also no heat resistance at high temperature.

Examples of the polymer resin used in the present invention include organic polymers, natural polymers and derivatives thereof which are excellent in synthetic or natural water resistance.

Here, the water resistance means that the polymer resin does not elute in the treated water even at the initial stage of water passage to the adsorbent, or at least there is no elution such as a problem that occurs for the beverage.

Therefore, general resin which is excellent in water resistance, such as olefin resin, such as polyethylene resin, vinyl chloride resin, vinylidene chloride resin, styrene resin, and polysulfone resin, can be used.

Particularly preferred polymer resins include fluorine resins and acetalized polyvinyl alcohol resins.

Specific examples thereof include polyvinylidene fluoride resin, vinylidene fluoride-6-propylene propylene copolymer resin, polytetrafluoroethylene resin, polyvinyl butyral resin and the like. Such a polymer resin is easy to contain a rare earth element hydroxide and / or hydrous oxide in high concentration, and is excellent in water resistance and chemical resistance, and can be said to be especially preferable resin.

The rare earth element hydroxide and / or hydrous oxide used in the adsorbent of the present invention is a rare earth element of group 3 (3A) according to the periodic table of the elements of 1991, and includes scandium Sc, yttrium Y, lanthanoid element, lanthanum La, and Ce Ce. Praseodymium Pr, Neodymium Nd, Promethium Pm, Samarium Sm, Europium Eu, Gadolinium Gd, Terbium Tb, Dysprosium Dy, Holmium Ho, Erbium Er, Thulium Tm, Ytterbium Yb, Lutetium Lu, and / or hydrous oxides. Among them, the preferred element consistent with the object of the present invention is Ce, and tetravalent Ce is preferable. Mixtures of these rare earth element hydroxides and / or hydrous oxides are also useful. Especially, it is preferable to contain 5 weight% or less of Ywp in Ce.

The rare earth element hydroxide and / or hydrous oxide used in the present invention is particularly preferably excellent in acid resistance in the fluorine adsorbent. Acid resistance here means that 1 L of aqueous solution containing 50 mg / L of fluorine ions is previously adjusted to pH 3.2, 100 mg of rare earth element hydroxide and / or hydrous oxide are added and stirred at pH 3.0 for 4 hours, and then the cerium concentration in the liquid is adjusted. Expressed by measuring using ICP. Acid resistance in this invention makes cerium concentration 7.5 mg / L or less favorable.

In addition, in the boron and arsenic adsorbent of the present invention, the rare earth element hydroxide to be used is always preferable if it contains water, and its water content is 1 to 30 parts by weight of water, preferably 5 to 18 to 100 parts by weight of Ce hydroxide. It is 5 weight part, More preferably, it is 5-15 weight part. Because of this water content, the rare earth element hydroxide and / or has a high content which cannot be considered at a conventional level (400 parts by weight per 100 parts by weight of resin) which is considered to be impossible, and 600 parts by weight or more per 100 parts by weight of the polymer resin. Adsorbents containing hydrous oxides can be made, and in particular, the adsorption capacity of 2-4 times that of boron and arsenic adsorption can be obtained. The adsorbent of this invention shows the adsorption amount which the saturation adsorption amount (equilibrium adsorption amount) could not achieve by the prior art as shown in FIG. 4, FIG.

Although the reason is not clear, the water function improves the fluidity of the rare earth element hydroxide and / or the hydrous oxide, so that proper mixing with the resin is performed, and the surface of the rare earth element hydroxide and / or the hydrous oxide particles as shown in Figs. By forming the porous skin layer of the polymer resin, the rare earth element hydroxide and / or the hydrous oxide are kept inside the particles without flowing out, and the rare earth element hydroxide and / or the hydrous oxide secondary to water aggregation are suitable particles. It is presumed to increase the boron and arsenic adsorption capacity as a result of the action of diameter, the formation of voids of the secondary particles to enable proper contact with boron and arsenic-containing water, and the prevention of hydroxide from returning to the oxide. .

In the method for measuring the water content, the resin is mixed with the resin mixed particles with a resin dissolving agent, followed by volatilization or fractional removal of the solvent, and the remaining hydrous rare earth element hydroxide and / or hydrous oxide are left at 800 ° C. for 1 hour. The value obtained by subtracting the evaporated fraction from the hydrous rare earth element hydroxide and / or the hydrous oxide is expressed by the moisture content.

On the other hand, in the fluorine adsorbent of the present invention, a rare earth element hydroxide and / or a hydrous oxide having a crystallite diameter of 50 to 200 kPa is particularly preferable. The rare earth element hydroxide and / or the hydrous oxide having a crystallite diameter of 50 to 200 kPa of the present invention is a high-temperature heating aging solution of rare earth element hydroxide and / or hydrous oxide having a water content of 1 to 40% by weight as defined below. It is made by heating and maturing at -600 ° C for 1 to 10 hours. At this time, in consideration of workability, in order to obtain a rare earth element hydroxide and / or a hydrous oxide having a large crystallite diameter in a short time, the rare earth element hydroxide and / or are heated and aged for 2 to 10 hours under conditions of 350 ° C to 420 ° C in the air. It is good to obtain a hydrous oxide. If it is less than 300 degreeC, the crystallite diameter of a rare earth element hydroxide and / or a hydrous oxide cannot satisfy | fill the requirements of this invention, it is inferior to acid resistance, and the elution of a rare earth element increases. Moreover, when it exceeds 600 degreeC, it will become a some oxide and fluorine treatment capacity will fall.

This high temperature aging surprisingly showed that the adsorbent of the present invention was suppressed in the amount of the rare earth element compound dissolved in water to an amount less than half of the conventional fluorine adsorbent. Thus, the rare earth element compound for fluorine adsorption which suppressed the elution amount is not known conventionally. For example, it is surprising that a rare earth element oxide having a heat loss of 5 to 30% by weight as described in Japanese Patent Application Laid-Open No. 2-17220, but not a hydrous oxide having a specific crystallite diameter of the present invention, is surprising. Rare earth element hydroxides and / or hydrous oxides and rare earth element oxides have different thermal properties and exhibit different absorption bands in infrared analysis.

On the other hand, the high temperature aged rare earth element hydroxide and / or hydrous oxide of the present invention preferably has a water content of 0.1 to 20% by weight, more preferably 0.1 to 5.0% by weight. When the water content exceeds 20% by weight, the elution of the rare earth element, which is one of the effects of the present invention, tends to be large. In the method of measuring this moisture content, it is left to stand at 800 degreeC high temperature for 1 hour, and the value (heat loss) which subtracted the evaporate from the hydrous rare earth element hydroxide and / or hydrous oxide is represented by moisture content.

Although the rare earth element-based fluorine adsorbent of the prior art has a high water content and a small crystallite diameter of 20 to 40 kPa, the mixed state with the polymer resin is not good and the rare earth element hydroxide and / or the hydrous oxide are easily eluated. The crystal form of the rare earth element hydroxide and / or hydrous oxide of the present invention has a low crystalline water content due to this high temperature heating aging, but crystallization is progressing, and the crystalline rare earth having a good crystalline diameter of 50 to 200 kPa, preferably 60 to 200 kPa Elemental hydroxides and / or hydrous oxides. As a result, it is hard to elute in aqueous solution, and can maintain fluorine adsorption property and can obtain the outstanding fluorine adsorbent.

The thickness of the skin layer of the polymer resin in the boron, arsenic, and fluorine adsorbent of the present invention is preferably 0.01 to 2 m, preferably 0.1 to 0.5 m. If the thickness is less than 0.01 µm, rare earth elements may elute, and if the thickness exceeds 2 µm, water may be less likely to penetrate into the adsorbent at the time of water passage.

Moreover, the inside of the said polymer resin skin layer has a center cavity part and the micro void part around it, as shown to FIG. 11, FIG. The bulk density of this adsorbent has a bulk density of 0.4 to 2.0 g / cm ³ .

The secondary particles of the rare earth element hydroxide and / or the hydrous oxide are aggregates of primary particles having an average particle diameter of 0.01 to 0.1 µm, and the average particles of the secondary particles are preferably 0.2 to 25 µm, and in the boron adsorbent, 0.5 to 10.0 micrometers is preferable, and 1-6 micrometers is preferable in an arsenic adsorbent. Moreover, in a fluorine adsorbent, 0.1-25 micrometers is preferable and 0.5-10.0 micrometers is more preferable. If it is 0.2 micrometer or less, it may be surrounded by resin mixture, and the contact with these harmful substance containing water may be inadequate, and when it is 25 micrometers or more, mixing with resin may not be good.

Next, the manufacturing conditions of the boron and arsenic adsorbent of this invention are demonstrated.

The rare earth element hydroxide and / or hydrous oxide used for the boron and arsenic adsorbent of the present case adjust its water content to 1 to 30 parts by weight based on 100 parts by weight of the rare earth element hydroxide and / or the hydrous oxide (dry matter). The rare earth element hydroxide and / or hydrous oxide are oxidized by adding an oxidizing agent such as hydrogen peroxide after the operation such as solvent extraction and the like, and neutralizing the chlorinated rare earth compound into a hydroxide and / or a hydrous oxide, and the purified product is purified with pure water. The cake may be washed or shaped into a cake or commercially available hydroxide cake. Since the cake-like rare earth element hydroxide and / or the hydrous oxide contain excess water, the rare earth element hydroxide is treated at a low temperature of 50 to 70 ° C. using a conventional heating apparatus in order to obtain a specific moisture content of the present invention. And / or 1 to 30 parts by weight of water based on the hydrous oxide.

The rare earth element hydroxide and / or hydrous oxide containing a specific amount of water obtained as described above can then be mixed with the polymer resin to obtain the boron, arsenic, and fluorine adsorbents of the present invention.

The mixing may be performed by adding a solution in which a polymer resin having a weight of 6 times or more dissolved in a solvent is added to the rare earth element hydroxide and / or the hydrous oxide containing a certain amount of water, or the rare earth element hydroxide and / or the hydrous oxide is combined with the polymer resin. The dispersion obtained by mixing the resin with a solvent for dissolving the resin, and the obtained dispersion has an average particle diameter of 0.2 mm to 5.0 mm and a water content of a rare earth element hydroxide and / or a hydrous oxide using a conventional particle maker. 1-30 weight part of the boron and arsenic adsorbents of this invention can be obtained. The fluorine adsorbent can also be produced by the same operation using a hydrous oxide which has undergone the above heating aging and has a predetermined crystallite diameter. On the other hand, when preparing the dispersion, the polymer resin may be mixed in the organic solvent together with the rare earth element hydroxide and / or the hydrous oxide without dissolving the polymer resin in advance in the organic solvent.

On the other hand, the solvent is not particularly limited as long as it can dissolve the polymer resin.

The rare earth element hydroxide and / or the hydrous oxide can be obtained by neutralizing the rare earth element nitrate with a hydroxyl group. However, if the pH at the reaction is on the acidic side, the unreacted rare earth element nitrate is the rare earth element hydroxide and / or the hydrous oxide. A small amount remains in the. Although the specific reason is not clear, when 1-10 weight part of rare earth element nitrates remain per 100 weight part of rare earth element hydroxides and / or hydrous oxides, as shown in Table 2, 4, the knowledge that it has a higher boron and arsenic adsorption performance is known. Found in the course of development, it has been found to be preferable in solving the object problem of the present invention.

The arsenic {As (V) and As (III)}-containing water of a predetermined concentration is filled with the particulate arsenic adsorbent of the present invention in a water capacity of 1 to 20,000 times the capacity of the adsorbent. In this case, the arsenic concentration of the contained water passed through is maintained at 0.01 mg / l or less. Moreover, even if the air column speed at the time of water passage is 100-200 l / hr which is far exceeding the conventional level of 10 l / hr, it has sufficient adsorption performance. On the other hand, in this case, the pH of the arsenic-containing water used for passing water is preferably 4 to 10 to activate and maintain the adsorption capacity of the adsorbent. In the case of a boron adsorbent, suitable pH is 7-9.

In addition, the particulate fluorine adsorbent of the present invention is filled into a predetermined container, and when the fluorine-containing water having a predetermined concentration is passed 1 to 400 times the weight of the adsorbent, it is referred to as the water passing through. The fluorine concentration is kept at a low concentration (eg 2 mg / L or less). On the other hand, in this case, the pH of the fluorine-containing water used for passing water is preferably adjusted to 3 to 6, so that the adsorption capacity of the adsorbent can be activated and maintained. This pH can be adjusted with hydrochloric acid or caustic soda.

In addition, when the adsorption capacity of the present invention decreases due to prolonged use, the adsorbent can be regenerated by a known method (for example, by a method described in Japanese Patent Laid-Open No. 2000-140626) to restore the adsorption capacity. have.

The Example and the comparative example of this invention are shown below.

SV in the sentence is the air column velocity (space velocity), which is the amount of water passed through the adsorbent, and the water flow rate per liter of the adsorbent. For example, if it is 20 times the speed | rate of an adsorbent per hour, it means what passed through 20 liter / hr.

In addition, the water flow rate means how many times the water flowed per adsorbent capacity, For example, when the water flow rate 200 with 1 L of adsorbent, it means that 200 liters of water flowed.

Saturated adsorption amount is a value which shows how much it can adsorb | suck at the time of making it adsorb | suck to an adsorbent with the boron, arsenic, and fluorine aqueous solution of a specific density | concentration, and changes with the said concentration.

Example 1 and Comparative Example 1

H ₃ BO ₃ reagent grade 1 was dissolved in tap water to prepare a liquid having an initial concentration of 20.17 mg / L, and pH 8.5 was confirmed. Hereinafter, this is called tap water-containing liquid. In addition, first grade H ₃ BO ₃ reagent was dissolved in pure water to prepare a liquid having an initial concentration of 20.72 mg / L, and pH 8.5 was confirmed. This is hereinafter referred to as pure water boron-containing liquid. Separately, cerium hydroxide was made into a moisture content 20 weight% with a 70 degreeC low temperature dryer, and the hydrous cerium oxide powder was obtained. This powder, vinylidene fluoride, and propylene hexafluoropropylene copolymer resin were mixed and dispersed in the solvent N-methyl-2-pyrrolidone to obtain a dispersion liquid. Subsequently, the dispersion was produced in a particle manufacturing machine and washed with water to obtain particles having a circular average particle diameter of 0.70 mm, which was a ratio of 700 parts by weight of cerium oxide based on 100 parts by weight of the resin. Hereinafter, this particle is called READ-B.

Apart from this READ-B, examples of commercially available boron-selective chelate resins (registered trademark of Mitsubishi Chemical Co., Ltd.) dia ion CRBO2 (conditioning; sulfuric acid immersion, caustic soda multiplexing) and Japanese Patent Application Laid-Open No. 63-24431 An adsorbent A (a particle was prepared using a polyacrylonitrile resin, which was prepared based on the description of 27), was prepared, which corresponds to 400 parts by weight of cerium oxide hydrous based on 100 parts by weight of the resin.

The column top was filled with 15 ml of READ-B, 15 ml of CRBO2, and 15 ml of Adsorbent A, respectively, in the column water boron-containing and pure water-boron-containing solutions, respectively. Under the condition of, the water permeation ratio (the water permeation capacity per charged particle capacity) was varied and tested, and the boron concentration (mg / L) (treatment liquid boron concentration) and total organic carbon (hereinafter referred to as TOC) in the water passed through were referred to as TOC. ) Was measured. The TOC measurement and analysis apparatus uses a Shimazu Seisakusho TOC-VCSH type apparatus, and the sampling method is taken with pure water boron containing liquid at 200 times the water magnification, and the value of TOC is obtained from pure water boron containing liquid of water. Obtained from the car. The results are shown in Figure 1 and Table 1.

From Table 1, the adsorbent of the present invention can be clearly prevented from elution of the dissolved substance in water (Oppb in Example 1) even in the comparison of Comparative Example 1, and there is no problem for drinks and ultrapure water, In FIG. 1, it can be seen that the adsorption of boron in water is poor, the adsorption rate is slow, the adsorption short time is decreased, and the heat resistance is low. In addition, there is no need for a multi-stage large apparatus, and there is no complicated operation, and since there is no settling to powder, there is no problem of adsorbed precipitate sludge.

Table 1

   TOC concentration   READ-B     0 ppb   CRBO2     5 ppb   Adsorbent A    30 ppb

Example  2, Comparative example  2

H ₃ BO ₃ reagent grade 1 was dissolved in tap water to prepare a liquid having a (initial) B concentration of 200 mg / L, and a liquid of pH 9.0 was prepared by containing 8,000 mg / L of Na ₂ SO ₄ . To 1 L of this preparation solution, boron adsorbent READ-B of hydrous cerium oxide prepared in Example 1 and the commercially available CRBO2 were added and stirred for 70 hours. The relationship between the liquid phase B concentration (mg / L) and the boron adsorption amount (g / g-CeO ₂ ) of the liquid after stirring was observed. In addition, the measurement was performed by changing the usage-amount of a boron adsorbent. As a result, as shown in Figure 2, the READ-B, it was found that the amount of boron adsorption (g / g-CeO ₂ ) throughout the entire liquid B concentration (mg / L) compared to the commercial resin CRBO2.

Example 3, Comparative Example 3

Example 1 and Comparative Example 1 are pure water boron-containing liquid (initial) B concentration of very high 203.0mg / L (H ₃ BO ₃ ), and other ions SO ₄ 5,000mg / L, Cl other than 10,000mg containing / L, S O _{2 6} to 300mg / L, Mg to 300mg / L, the whole operation was similarly. The result is shown in FIG.

As can be seen from FIG. 3, the adsorbent of the present invention reliably adsorbs B even in the presence of ions that inhibit B adsorption, and thus has excellent adsorption properties of boron in water, which is much superior to commercial resins, fast adsorption rate, and short time adsorption properties. It turned out that the performance is shown without deterioration with time.

Example 4

READ-B of Example 1 was added (initial) B concentration {mg / L (H ₃ BO ₃ )} to 1 L of pure water boron-containing liquid whose pH was adjusted to 8.5 at 15 mg / L, and stirred for 72 hours. In addition, the measurement was performed by changing the usage-amount of a boron adsorbent. The result is shown in FIG. It is understood that the adsorbent of the present invention is effectively adsorbed from low concentration to high concentration.

Example 5

16 g of cerium hydroxide powders having different residual nitric acid concentrations were dispersed in 1 l of pure water boron-containing liquid ((initial) B concentration 200 mg / l) of Example 2, and the pH was measured, and then adjusted to pH = 8.4-8.6. Stir for 20 hours. After completion of stirring, the filtrate was filtered by ICP (inductively coupled plasma), and the boron adsorption amount was calculated from the measured values. The results are shown in Table 2.

TABLE 2

  Sample Number    A    B    C    D    E    F  Ce hydroxide hydroxide content (%)   17.98   16.11   17.25   16.53   17.04   16.38  PH before adjustment    3.18    3.56    4.55    4.93    6.48   11.66  Residual Nitrate Concentration (mg / g-Ce)   65.6   48.7   39.3   30.2   13.25    0.33  Boron adsorption performance (mg / g-Ce)   23.35   22.12   21.36   20.64   19.86   17.36

It can be seen from Table 2 that the higher the residual nitric acid concentration in cerium hydroxide can have higher boron adsorption performance.

Example 6, Comparative Example 4, Comparative Example 5

Dissolved dihydrogen bisodium hexahydrate (Na ₂ HAsO ₄ · 7H ₂ O) in tap water to prepare a liquid with (initial) As (V) concentration of 1 mg / l to check pH 7.0. It is called liquid. Separately, the cerium nitrate aqueous solution and the sodium hydroxide aqueous solution were neutralized, purified and dehydrated to obtain a hydrous cerium oxide powder having a water content of 30 to 40% by weight. Subsequently, the powder was dried with a 70 ° C. low temperature dryer to obtain a hydrous cerium oxide powder having a water content of 16% by weight. 833 parts by weight of this powder and 100 parts by weight of polyvinyl butyral resin were dispersed in 700 parts by weight of solvent N-methyl-2-pyrrolidone to obtain a dispersion. Subsequently, this dispersion liquid was put into a particle manufacturing machine, and the particle | grains of the circular average particle diameter of 0.70 mm used as the ratio of 700 weight part of cerium oxides with respect to 100 weight part of resin were obtained. When the cross section of this particle | grain was seen under a microscope, it is as FIG. 11 and FIG. Hereinafter, this particle is called adsorbent A.

Apart from this adsorbent A, an arsenic adsorbent (trade name: Hisokyu) manufactured by Japanese Patent Application Laid-Open No. 61-18793 was prepared as a comparative example.

15 ml of this particle adsorbent A and 15 ml of histokyu were charged to the column column, respectively, and the water content of tap water scattered in front of the column was kept at an air column speed (space velocity; SV) of 10 l / hr. The experiment was carried out by changing the time of day, and As (V) concentration (mg / l) (treatment solution arsenic concentration) in the water passed through was measured. The results are shown in FIG.

In addition to the adsorbent A, as a comparative example, the total organic carbon TOC of the present applicant's prior art product (adsorbent B) carrying ethylene vinyl alcohol copolymer resin as a carrier and carrying cerium hydroxide was measured. The TOC measurement and analysis apparatus used a TOC-VCSH type apparatus manufactured by Shimadzu Seisakusho, and the sampling method was taken with pure water arsenic content at the time of 200 times the water magnification. The measurement results are shown in Table 3.

TABLE 3

 Measurement Sample    TOC concentration  Adsorbent A     0 ppb  Adsorbent B    20 ppb

The TOC density | concentration of the adsorbent B of Table 3 is a value of the initial stage of water passage, and the eluate dissolves after a while after water passage. Therefore, if the adsorbent is washed with water in advance and the treated water is further treated with activated carbon, there is no problem in actual use, but it is thought that eluting itself should be improved. With regard to the adsorbent of the present invention, it is apparent from Table 2 that easiness of elution of the dissolved substance in water can be prevented and there is no problem for beverages. It has been found that the lowering has been solved and the high adsorption performance is maintained.

Example 7

Dissolution of diarsenic trioxide anhydride (As ₂ O ₃ ) in tap water to prepare a liquid (initial) As (III) concentration of 1mg / l to confirm the pH 7.0. 15 ml of the adsorbent A of Example 6 packed with the liquid column was tested under varying days of water passage under the condition of SV = 101 / hr, and the concentration of As (III) in the water passed through was measured. In addition, after the adsorbent A after the passage of water was regenerated with sodium hydroxide, the As (III) concentration was measured under the conditions of passing water. The recycled water was cycled twice. As a result, as shown in FIG. 6, it was also found that trivalent arsenic acid, which cannot be collected by the coagulation sedimentation method (coprecipitation method), is adsorbed, and the adsorption performance after the regeneration treatment does not decrease.

Example 8

A water passage test was conducted under the same conditions as in Example 6, and the As (V) concentration and the cerium (Ce) concentration in the water passed through were measured. The result is shown in FIG.

From Fig. 7, it was found that even if arsenic adsorption reached breakthrough, the elution amount of cerium was extremely low.

Example 9

Dissolved dihydrogen dihydrogen dihydrate (Na ₂ HAsO ₄ .7H ₂ O) in pure water to prepare a liquid (initial) with an As (V) concentration of 100 mg / l, pH 7.0 was confirmed.

In addition, a liquid having a (initial) As (III) concentration of 100 mg / l was prepared by dissolving arsenic trioxide anhydride (As ₂ O ₃ ) in pure water to confirm pH 7.0. 2 ml of the adsorbent A of Example 6 was added to 1 liter of each of the arsenic-containing liquids described above, followed by stirring for 48 hours. The result is shown in FIG. It was found that the adsorbent of the present invention effectively adsorbs arsenic from low to high concentrations.

Example 10

2 ml of Adsorbent A of Example 6 was added to 1 liter of As (V) -containing liquid and As (III) -containing liquid each having adjusted pH in the range of 5-12 at (initial) concentration of 2 mmol / l for 48 hours. Stirred. The result is shown in FIG. It was found that the adsorptivity of the adsorbent of the present invention, in particular, the adsorption to As (III), was less affected by pH.

Example 11

By diluting the tap water-containing liquid of Example 6 {(initial) As (V) concentration 1mg / l} to prepare a liquid of (initial) As (V) concentration 0.5mg / l and 0.1mg / l, respectively, pH 7.0 was confirmed. The conditions other than SV were carried out similarly to Example 1, the SV was changed, the water flow test was performed, and the arsenic removal rate was computed from the As (V) concentration in the said water flow. The result is shown in FIG.

From Fig. 10, even in the high SV region of SV = 100 L / hr or more, about 70% or more of arsenic is removed, and particularly about lean solution of (initial) As (V) concentration of 0.5 mg / l or less is about 80% or more. Arsenic was removed at a high rate.

Example 12

By changing the concentration of the aqueous sodium hydroxide solution added to the aqueous solution of cerium nitrate, the pH during the neutralization reaction was adjusted to obtain a hydrous cerium oxide powder having different concentrations of residual cerium nitrate.

The water-containing cerium oxide powder was dispersed in 1.5 g of 1 g of pure water fly ash-containing liquid {(initial) As (V) concentration of 100 mg / l} in Example 9, adjusted to pH 6.5-7.0, and stirred for 20 hours. After completion of stirring, the filtrate was filtered by ICP (inductively coupled plasma), and arsenic adsorption performance was calculated from the measured values. The results are shown in Table 4.

Table 4

  Sample Number    A    B    C    D    E    F  Ce content rate (%)   17.98   16.11   17.25   16.53   17.04   16.38  Reaction pH    3.18    3.56    4.55    4.93    6.48   11.66  Residual Nitrate Ce Concentration (mg / g-Ce)   65.6   48.7   39.3   30.2   13.25    0.33  Arsenic adsorption performance (mg / g-Ce)   59.1   56.5   53.8   51.7    49.3    44.6

From Table 4, it was found that the higher the concentration of residual cerium nitrate in the hydrous cerium oxide has the higher arsenic adsorption performance.

From the results of Examples 6 to 12, it is clear that the adsorbent of the present invention is significantly improved in the adsorption performance of arsenic as compared with the conventional adsorbent. That is, it is possible to purify a large amount of water contaminated with arsenic on the highway, and to efficiently purify the treated water including low concentration of arsenic, and also to maintain the adsorption activity for a long time, so that the maintenance is easy. In addition, an adsorbent and a resin component do not elute.

Examples 13, 14, and Comparative Examples 6-11

Instead of drainage, NaF (Reagent Express) was dissolved in pure water to prepare a liquid having an initial fluorine concentration of 50 mg / L, and an aqueous solution adjusted to pH 3.0 by adding hydrochloric acid was obtained.

Cerium hydroxide having a water content of 50% by weight was aged in the air under the conditions shown in Table 1 in an electric furnace to obtain a hydrous cerium oxide powder having a large crystallite diameter in Table 5. Heat loss weight% of this hydrous cerium oxide (The heat loss (%) at the time of an electric furnace at 800 degreeC for 1 hour); Moisture content} was measured, the moisture content weight% was the value in Table 5.

To 100 parts by weight of this hydrous cerium oxide, a solution in which 12 parts by weight of a polyvinylidene fluoride resin was dissolved in solvent N-methyl-2-pyrrolidone was mixed to form a slurry, and the voids were dispersed by dispersing the slurry in an aqueous solution. A powder granular body having a bulk density of 2.0 g / cm ³ and an average particle diameter of 0.7 mm was obtained.

As a comparative example, it operated similarly to Example 13 except having carried out the heating temperature at 70-300 degreeC for 1 to 4 hours, and made the weight loss weight% (water content%; Ig-loss) of the crystallite diameter of Table 5 the same. Powdery granules were obtained.

100 mg of the powder granules as CeO ₂ was added to 1 L of the fluorine-containing aqueous solution prepared above, followed by stirring for 4 hours while adjusting the liquid pH to 3.2. The fluorine concentration and cerium concentration of the treatment solution were measured. The measurement of fluorine concentration was carried out using an F-23 apparatus manufactured by Horiba Seisakusho, the cerium concentration was performed by an inductively coupled high-frequency plasma (ICP) apparatus, and the apparatus was used by a Rigaku CIROS 120 EOP apparatus. The results are shown in Table 6. Acid resistance makes this cerium concentration 7.5 mg / L or less favorable.

From Tables 5 and 6, the hydrous cerium oxide adsorbent of the present invention, as is clear even in comparison with Comparative Examples 6, 7, and 9, has no problem in treating fluorine, and can prevent elution of cerium in water, resulting in durability. The poor acid resistance of the comparative example concerned is solved.

Table 5

        Heating condition  Crystalline diameter (Å)   Heat loss (%)   Heating temperature (℃)   Heating time (hours)  Example 13     550      3     98     1.1  Example 14     450      5     64     2.4  Comparative Example 6     250      4     39     5.7  Comparative Example 7     200      2     34     7.5  Comparative Example 8     150      2     25    10.2  Comparative Example 9     120      3     28    17.2  Comparative Example 10     100      4     29    20.3  Comparative Example 11      70      4     25    30.3

As the crystallite diameter, the average size of the crystallite was determined from the sample factor half-value width FW (S) of any one peak in the diffraction pattern, using the Scherrer equation shown below.

Crystallite Size (A) = K × Wavelength / FW (S) × COS (θ)

(θ) is the position of the peak, K is the shape factor of the average determinant

Table 6

  Fluorine Concentration (mg / L)    Ce concentration (mg / L)   Ce leaching amount (%)   Example 13     43     2.4     2.9   Example 14     43     3.2     3.9   Comparative Example 6     43     8.2    10.1   Comparative Example 7     43    15.6    19.2   Comparative Example 9     43    17.1    21.0

The Ce dissolution rate is calculated by the following formula for the amount of cerium in the unused cerium oxide.

Collection amount × (cerium atomic weight / cerium oxide molecular weight)

Amount of collected cerium: 100 × (140/172) = 81.38mg

The Ce dissolution rate can be obtained from the following formula from the amount of cerium in unused cerium oxide and the concentration of cerium in the treatment liquid.

Dissolution rate (%) = Cerium concentration measurement value / amount of collected cerium × 100

On the other hand, the said Example is described as the main idea which shows that the fluorine adsorbent of this invention is acid resistant and the elution rate of cerium is remarkably suppressed. In particular, in order to further reduce the fluorine concentration, the amount of the adsorbent may be increased.

Since the boron, arsenic, and fluorine adsorbents of the present invention are made of a porous polymer resin as a skin layer, the boron, arsenic, and fluorine adsorbents may contain a large amount of rare earth metal hydroxides and / or hydrous oxides with many voids therein, so that these harmful adsorbents have a conventional adsorbent. Outstandingly superior to In addition, contaminated water having a low concentration of these harmful substances can be efficiently purified. For example, fluorine functions effectively at about 20 to 50 mg / L. In addition, since the adsorption activity can be maintained for a long time, maintenance is also easy. Furthermore, since there is no elution of the adsorbent component into the treated water and no initial elution of the polymer resin, the water treatment step of the adsorbent as this countermeasure and the final treatment with activated carbon are not required in the treated water after these harmful substances adsorption treatment.

Claims (7)

An adsorbent containing at least one of the group consisting of rare earth element hydroxides and hydrous oxides which adsorb and remove these harmful substances from water containing at least one harmful substance of the group consisting of boron, arsenic and fluorine, wherein the rare earth The adsorbent described above, wherein the porous membrane of the water-resistant polymer resin covers at least one surface of the group consisting of elemental hydroxides and hydrous oxides, and comprises a granulated body having a central cavity portion and a fine void portion around the porous membrane. The adsorbent of Claim 1 containing at least 1 sort (s) of the group which consists of 600 weight part or more of a rare earth element hydroxide and a hydrous oxide per 100 weight part of said water resistant polymer resins. The adsorbent according to claim 1 or 2, wherein the polymer resin is a resin selected from a fluororesin and an acetalized polyvinyl alcohol-based resin. The fluorine adsorbent according to claim 1, wherein at least one of the group consisting of rare earth element hydroxides and hydrous oxides has a crystallite diameter of 50 to 200 kPa. At least one of the group consisting of the rare earth element hydroxide and the hydrous oxide whose water content is adjusted to 1 to 30 parts by weight relative to at least one 100 parts by weight of the group consisting of the rare earth element hydroxide and the hydrous oxide is selected from the above resin together with the water resistant polymer resin. A dispersion is prepared by mixing with a dissolving organic solvent or by mixing with a solution of an organic solvent in which a water-resistant polymer resin is dissolved, and at least one surface of the group consisting of the rare earth element hydroxide and a hydrous oxide is dispersed from the dispersion. A method for producing at least one adsorbent of the group consisting of boron and arsenic, wherein the porous membrane is coated to produce particles having a structure having a central cavity portion and a fine void portion surrounding the porous membrane. Rare earth element hydroxide having a water content of 1 to 40% by weight and rare earth element hydroxide having a crystallite diameter of 50 to 200 kPa by heating and aging at least one kind of the group consisting of rare earth element hydroxide and hydrous oxide at 300 ° C to 600 ° C for 1 hour to 10 hours. At least one member of the group consisting of oxides is mixed with a water-resistant polymer resin, or mixed with an organic solvent solution in which the water-resistant polymer resin is dissolved to prepare a dispersion, and the group consisting of the rare earth element hydroxide and a hydrous oxide from the dispersion. A method for producing a fluorine adsorbent, characterized in that the porous membrane of a water-resistant polymer resin coats at least one surface of the particles with a structure having a central cavity portion and a fine pore portion surrounding it. delete

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