JP2003190942A - Adsorbent for water cleaner, method for manufacturing the same and water cleaner using the adsorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adsorbent for a water cleaner excellent in the adsorptability of heavy metals, especially lead, to provide a method for manufacturing the same and the water cleaner using the adsorbent. <P>SOLUTION: A powder of an aluminosilicate inorganic ion exchanger and/or a powder of a titanium silicate compound is added to a mixed slurry of a powder of calcium phosphate and water to be mixed therewith and the mixture is dried and granulated to obtain the absorbent for the water cleaner containing the calcium phosphate as a binder and excellent in heavy metal removing capacity. Further, the water cleaner using this adsorbent can develop excellent heavy metal removing capacity over a long period of time. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorbent for a water purifier capable of removing heavy metals, particularly lead, which impairs safety and taste, a method for producing the same, and a water purifier using the same.

[0002]

2. Description of the Related Art There is a water purifier that uses activated carbon to remove residual chlorine, trihalomethane, etc. contained in tap water. If you don't use this type of water purifier for a long time,
It is not preferable because various bacteria are generated in the activated carbon. Therefore, in order to prevent outflow of various bacteria generated in activated carbon, a water purifier using membrane filtration such as a porous membrane has been developed, and recently, this type has become the mainstream.

On the other hand, as a substance which may be eluted from the ground or a water distribution pipe and contained in well water or tap water in the form of ions, harmful substances such as lead, iron, copper, nickel and zinc, There are heavy metals such as chromium and cadmium, and various studies have been made on methods for removing them.

Among the heavy metals, as a lead adsorbent, Japanese Patent Laid-Open No. 7-204630 discloses Na ₂ O / K ₂ O / C.
aO / Al ₂ O ₃ / SiO ₂ = 0.4-1.0 / 0.0-0.0.
Described is an adsorbent for an aluminosilicate-based inorganic ion exchanger, which is an acidic oxide complex having a molar ratio composition of 4 / 0.0 to 0.5 / 1.0 / 1.5 to 3.0. . As this aluminosilicate inorganic ion exchanger, synthetic zeolites of molecular sieve 3A, molecular sieve 4A, molecular sieve 5A, and molecular sieve 13X are described.

In general, these synthetic zeolites are synthesized with microcrystals of several to several tens of μm, and when used as an adsorbent for a water purifier, they cause an increase in pressure loss when passing water, so they cannot be used as they are. difficult. In JP-A-7-204630, the particle size of the aluminosilicate-based inorganic ion exchanger is preferably as small as possible from the viewpoint of adsorption performance, but in consideration of filtration resistance, the particle size is 0.1 to 0.5 mm. The range is described as being preferred. In addition, Japanese Patent Publication No. 6-504714 discloses that heavy metals in an aqueous solution, especially as a lead adsorbent,
Amorphous titanium silicate is described.

As a method for controlling the particle size of fine particles such as synthetic zeolite, there is known a particle size increasing method in which a binder or a binder is used to bond the particles to each other to increase the particle size. JP-A-60-14936 describes bentonite, diatomaceous earth, colloidal silica and the like as inorganic binders, and celluloses and alginates as organic binders. As a method of granulating, clay minerals such as bentonite and kaolin, synthetic zeolite fine particles and water are mixed at a certain mixing ratio, and the mixture is heated to 600 to 800 ° C.
A method of firing at a high temperature is known. At this time, clay minerals such as bentonite play a role of a binder for the synthetic zeolite fine particles by causing a phase change of the crystal structure at around 700 ° C. and being sintered.

Also, in Japanese Patent No. 2756567, Ca type CMC (carboxymethyl cellulose) and / or N is used as a granulation aid together with a binder such as clay.
An a-type CMC is described. In addition, Japanese Patent Laid-Open No. 7-14
Japanese Patent No. 4913 describes an organic polymer emulsion or latex. In addition, a thermofusible resin or a thermosetting resin may be used.

[0008]

However, when the aluminosilicate-based inorganic ion exchanger adsorbent described in JP-A-7-204630 is granulated using a clay mineral such as bentonite as a binder, the temperature of 600 to 800 ° C. Particles having strength sufficient to withstand water flow cannot be obtained without heat treatment at high temperature, but when heat treated at high temperature, in synthetic zeolite, which is an aluminosilicate inorganic ion exchanger,
Part of the crystal structure may be collapsed, and the adsorption performance may be deteriorated.

On the other hand, when a heat-melting resin, a thermosetting resin, or an organic compound such as a cellulosic resin, an emulsion, or a latex is used as a binder, heat treatment at high temperature is not necessary, but elution of the organic compound or its additive is required. There is a concern that it is not always preferable as a filler for water purifiers.

In view of the above situation, the present inventors have diligently studied an adsorbent for a water purifier, which solves the above-mentioned problems and does not contain heavy metals, particularly lead, and which can obtain safe and delicious water in the long term. As a result of repeating, the present invention was completed.

[0011]

That is, the first gist of the present invention is to provide an aluminosilicate inorganic ion exchanger, or
And a titanium silicate-based compound and a calcium phosphate-based compound, which are adsorbents for water purifiers.

The average particle size of the adsorbent for the water purifier is 20 to 7
When it is 50 μm, the adsorption performance is excellent and water is easily passed, which is preferable. In addition, it is preferable that the content of the calcium phosphate-based compound is 10% by weight or more because granulation can be performed while maintaining high adsorption performance. In addition, the aluminosilicate-based inorganic ion exchanger is a molecular sieve 3
A, molecular sieve 4 A, molecular sieve 5
A, at least one selected from synthetic zeolites of molecular sieve 13X, the specific surface area of the titanium silicate compound is 100 m ² / g or more, the calcium phosphate compound is hydroxyapatite, triphosphate It is more preferable that at least one selected from calcium and tetracalcium phosphate has excellent adsorption performance. It is preferable for the adsorbent for a water purifier to have a lead adsorption amount of 200 mg / g or more and a compression strength of more than 1.0 N / mm ² because both the adsorbent for a water purifier has sufficient strength and lead adsorption performance.

A second gist of the present invention is to add a powder of an aluminosilicate inorganic ion exchanger or / and a powder of titanium silicate compound to a mixed slurry of calcium phosphate compound powder and water, and mix them. After that, it is a method for producing an adsorbent for a water purifier, which is dried. It is preferable that the drying temperature is 80 to 150 ° C. because the production is easy. Further, it is preferable to bake at 300 to 700 ° C. after drying because the strength of the particles becomes high.

The third gist of the present invention is a water purifier using the adsorbent for a water purifier described above.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The aluminosilicate-based inorganic ion exchanger used in the present invention includes molecular sieve 3A and molecular sieve 4
A, molecular sieve 5A, molecular sieve 13
It is preferable that at least one kind of the synthetic zeolite X is used. These synthetic zeolites have high adsorption capacity for heavy metal ions, and especially the molecular sieve 5A is
Excellent in absorbing soluble lead ions.

The titanium silicate compound used in the present invention preferably has a specific surface area of 100 m ² / g or more. Particularly, those having a specific surface area of 300 m ² / g or more are excellent in the selective adsorption performance of heavy metals, especially lead even in the presence of competing ions such as calcium and magnesium.

These aluminosilicate inorganic ion exchangers and titanium silicate compound adsorbents are usually used in an amount of
Since it is produced with a particle size of several tens of μm and contains fine particles of 20 μm or less, it is difficult to use it as an adsorbent for a water purifier as it is. Therefore, the present inventors have found that a calcium phosphate-based compound is used as a binder. Here, the calcium phosphate-based compound is preferably at least one or more of hydroxyapatite, tricalcium phosphate, and tetracalcium phosphate.

The water purifier is usually required to have a flow rate of about 1 to 5 L / min as the amount of water passing by the tap water pressure. Therefore, the adsorbent filled in the water purifier also needs to have a shape in consideration of this flow rate, and a granule having an average particle diameter of 20 to 750 μm is generally used, and more preferably 150 to 500 μm. When the particle size is smaller than 20 μm, filtration resistance increases and water permeability deteriorates. On the other hand, when it is larger than 750 μm, the voids between particles become large, and the removal performance tends to be low.

The calcium phosphate compound can be synthesized by reacting a phosphate aqueous solution with a calcium salt aqueous solution. In particular, hydroxyapatite can be obtained as a slurry on the market. The granulated product produced by drying the synthesized calcium phosphate compound is characterized by having a strong binding force and being difficult to disperse easily in water. Therefore, it can be used as an aluminosilicate inorganic ion exchanger or / and When used as a binder for a titanium silicate compound adsorbent, the obtained granulated product is not damaged during passage of water and can be suitably used as an adsorbent for a water purifier.

As the granulation method of the adsorbent of the present invention, powder of an aluminosilicate inorganic ion exchanger or / and powder of titanium silicate compound is added to a mixed slurry of calcium phosphate compound and water, It can be produced by mixing and then drying. The particle size can be adjusted by classifying with a sieve.
Alternatively, a slurry obtained by adding powder of an aluminosilicate-based inorganic ion exchanger or / and powder of a titanium silicate-based compound to a slurry of a calcium phosphate-based compound,
Granulation can also be performed by spray drying.
Alternatively, the mixed slurry can be extruded and cut into a predetermined size to form pellets.

The calcium phosphate compound is preferably used in an amount of 10% by weight or more based on the weight of the aluminosilicate inorganic ion exchanger or / and the titanium silicate compound for granulation. If it is 10% by weight or less, the force for binding the fine particles to each other becomes insufficient. The content of the calcium phosphate-based compound is 95% by weight in order to maintain the adsorption performance.
The amount is preferably below, and more preferably 90% by weight or less. When the amount of lead adsorbed on the adsorbent for a water purifier of the present invention is 200 mg / g or more and the compression strength is larger than 1.0 N / mm ² , it has sufficient strength when used in a water purifier,
Therefore, it is preferable that it is not destroyed by water flow and has a good lead adsorption performance.

The lead adsorption amount (mg / g) means the amount of lead adsorbed by 1 g of the water purifier adsorbent when the water purifier adsorbent is immersed in an aqueous solution containing lead for 24 hours. . Specifically, for example, a lead nitrate aqueous solution is used to obtain a lead concentration of 200 m.
200 ml in Erlenmeyer flask prepared to be g / L
The amount of adsorbed lead can be determined by collecting 50 mg of the adsorbent for a water purifier, shaking the mixture, and filtering after 24 hours with a filter, and measuring the residual lead concentration in the filtrate water. Adsorption amount of lead of adsorbent for water purifier is 220mg
/ G or more is more preferable, and 250 mg / g or more is still more preferable.

The compressive strength (N / mm ² ) means Hiramatsu, Oka, Kiyama: Journal of the Japan Mining Industry Association, 81, 10, 24 (19).
It is obtained from the weight applied to the adsorbent for a water purifier when the adsorbent for a water purifier is compressed with a flat plate by referring to the method of 65), and the compressive strength: St (N / mm ² ), P; load (N) , D; St = 2.8 when the particle diameter (mm) is used.
It is calculated from the equation P / πd ² . The compressive strength of the adsorbent for a water purifier is more preferably 1.3 N / mm ² or more, 1.5 N
/ Mm ² or more is more preferable.

In the above-mentioned mixed slurry, when the proportion of the calcium phosphate compound is large and the amount of water added is small, the granulated product is simply dried at about 80 to 150 ° C., and the granulated product has such a particle strength as not to be destroyed by water passage. Is obtained. The drying temperature is preferably 100 to 130 ° C, most preferably about 110 ° C. On the other hand, when the proportion of the calcium phosphate compound is 10% by weight or less, or when the amount of water added is large, 1
There is a tendency that the production rate of the granulated product is lowered and the particle strength is lowered only by drying at about 10 ° C. In that case, in order to increase the particle strength of the granulated product, after granulation, 300 to 70 is further added.
It is also possible to bake at 0 ° C.

In this case, the calcium phosphate compound sinters and exerts an action of strongly binding the fine particles. But,
Synthetic zeolite, which is an aluminosilicate-based inorganic ion exchanger, causes a decrease in adsorption performance due to calcination.
Calcination at a high temperature of 0 ° C. or higher is not preferable, and also at a high temperature of 500 ° C. or higher, the specific surface area of the calcium phosphate-based compound starts to decrease, and at the same time, the adsorption performance is also lowered, which is not preferable. Therefore, the firing of the granulated product is 300 to 500.
C is more preferred.

Although calcium phosphate compounds are inferior to aluminosilicate inorganic ion exchangers and titanium silicate compounds, it is already known that they have an action of adsorbing heavy metal ions such as cadmium and lead. In particular, hydroxyapatite has excellent calcium ion / lead ion exchange performance, and has good lead removal performance.

The aluminosilicate inorganic ion exchanger of the present invention and / or the titanium silicate compound have an average particle size of 20 using the calcium phosphate compound as a binder.
The adsorbent for water purifiers, which are granulated into granules of ~ 750 μm,
Good lead adsorption performance is obtained as compared with the case of using the calcium phosphate-based compound having the same particle size alone.

Further, even when compared with an aluminosilicate inorganic ion exchanger or / and a titanium silicate compound calcined using an inorganic binder such as bentonite, the water purifier adsorbent of the present invention has a high temperature. Since it does not need to be fired at 1, the adsorption performance of the aluminosilicate inorganic ion exchanger and / or the titanium silicate compound does not decrease significantly. Furthermore, since the calcium phosphate-based compound itself is an adsorbent for heavy metals, especially lead, it exhibits good adsorption performance.

The water purifier using the adsorbent for a water purifier of the present invention described above can efficiently remove heavy metals.
Further, in order to efficiently remove residual chlorine, trihalomethane and the like, it is preferable to use activated carbon in addition to the adsorbent for a water purifier of the present invention. Although activated carbon has a low removal ability, it also adsorbs heavy metals and contributes to prolonging the adsorption performance of the adsorbent, so it is more preferably used in combination with activated carbon.

The activated carbon is not particularly limited as long as it has a performance that meets the purpose of removing residual chlorine, trihalomethane, etc., and its shape is powdery, fibrous,
Alternatively, a granular material or the like can be used. Further, the type of activated carbon is not necessarily limited, and natural activated carbon such as coconut shell activated carbon, bone charcoal, charcoal, pitch type, petroleum coke type,
A burning activator such as resin or rubber or a chemical activator can be used, but the substances to be removed are often those having a relatively small molecular weight such as trihalomethane, and when considering the economical efficiency, steam activated coconut shell activated carbon is also considered. Is most practically used. Furthermore, in order to impart antibacterial properties,
You may attach silver etc.

In addition to the adsorbent for a water purifier of the present invention and activated carbon,
It is more preferable to use a porous film because solid substances such as iron rust and bacteria can be removed. As the porous membrane, a flat membrane, a hollow fiber membrane, a tubular membrane or the like can be used, but it is more preferable to use a hollow fiber membrane having high volume efficiency. Examples of the hollow fiber membrane include cellulose-based, polyolefin-based (polyethylene, polypropylene), polyvinyl alcohol-based, ethylene-vinyl alcohol copolymer, polyether-based, polymethyl methacrylate (PMMA) -based, polysulfone-based, polyacrylonitrile. Materials made of various materials such as a series, a polyfluorinated ethylene (Teflon (registered trademark)) series, a polycarbonate series, a polyester series, a polyamide series, and an aromatic polyamide series can be preferably used. Of these, polyoolefin-based hollow fiber membranes such as polyethylene and polypropylene are preferable in consideration of the strength and elongation of the membrane, the bending resistance, the washability, the handleability and the high chemical resistance. Also, although not particularly limited, the outer diameter of the hollow fiber is 20 to 2
000 μm, pore diameter 0.01 to 2 μm, porosity 20 to
It is preferably 90% and the film thickness is 5 to 300 μm.

When the porous membrane is used in the water purifier of the present invention, if another filter medium is provided at the final stage after the water has passed, the fear of reverse bacterial contamination from the water purification outlet can be minimized. preferable. The adsorbent for a water purifier and the activated carbon of the present invention may be used in any order, or may be used as a mixture of the two. Further, in addition to the activated carbon, other components such as an ion exchange resin, calcium sulfite, coral sand, barley stone, meio stone, tourmaline may be used together.

The adsorbent for a water purifier, activated carbon and porous membrane of the present invention may be contained in one container or a combination of a plurality of containers. Further, it is preferable to use a primary filter in addition to the above combination so that coarse dust can be removed in advance.

The present invention will be specifically described below based on examples. <Example 1> Molecular sieve 5A (manufactured by Union Showa Co., Ltd.) and hydroxyapatite 35% slurry (manufactured by Ube Materials Co., Ltd.) were mixed so that molecular sieve 5A: hydroxyapatite = 90: 10% by weight, and 110 After drying at 0 ° C for 2 hours, the particles were classified to 150 to 500 µm and further fired at 500 ° C for 2 hours to increase the particle strength to obtain an adsorbent for a water purifier.

A lead adsorption test was carried out as follows using this adsorbent for a water purifier. Lead nitrate solution with a lead concentration of 200 m
Prepare to be g / L, and add 200 ml to an Erlenmeyer flask.
I collected it. Next, 50 mg of a water purifier adsorbent was added and shaken, and after 24 hours, the mixture was filtered through a cellulose filter having a pore size of 0.22 μm, and the residual lead concentration in the filtrate water was measured. The results are shown in Table 1.

<Example 2> An adsorbent for a water purifier was used in the same manner as in Example 1 except that the molecular sieve 5A: hydroxyapatite was adjusted to 10: 90% by weight, and no calcination was performed at 500 ° C. It was created and a lead adsorption test was carried out under the same conditions as in Example 1. The results are shown in Table 1.
Shown in.

Example 3 Titanium silicate (manufactured by Engelhard) was used in place of the molecular sieve 5A, and titanium silicate: hydroxyapatite = 10:
An adsorbent for a water purifier was prepared in the same manner as in Example 1 except that the content was adjusted to 90% by weight, and the firing at 500 ° C. was not performed, and a lead adsorption test was performed under the same conditions as in Example 1. did. The results are shown in Table 1.

Example 4 With respect to a water purifier using the adsorbent for a water purifier prepared in the same manner as in Example 1, the lead removal ability was evaluated by the following water flow test. In the water purifier shown in FIG. 1, resin frames 3 and 5 to which a 150-mesh nylon net was pasted were installed from the primary side to the first water purification tank 2, and Example 1
The adsorbent laminate 4 in which 80 g of the adsorbent for a water purifier used in the above and 450 g of activated carbon were mixed was prevented from flowing out. Second
In the water purification tank 7 of No. 1, the hydrophilic hollow polyethylene porous hollow fiber membrane 8 is fixed with a two-component polyurethane resin, and one end is cut and opened. The first water purification tank 2 and the second water purification tank The flow sensor 9 was installed in the middle of the water pipe 12 connecting the seven. Then, add lead nitrate to tap water,
Water flow rate 4L adjusted to 50μg / L as lead concentration
Water was passed through the inlet 6 at a flow rate of 1 / min. The pH of the water that was passed was set to the range of 6.6 to 7.4. 8 from the beginning of water flow
The lead concentration in the outflow water was measured when m ³ was passed. The results are shown in Table 2.
Shown in.

<Example 5> Using the adsorbent for a water purifier prepared in the same manner as in Example 2, a water purifier was prepared in the same manner as in Example 4,
The lead removal ability was evaluated by the same water flow test as in Example 4. The results are shown in Table 2.

<Example 6> Using the adsorbent for a water purifier prepared in the same manner as in Example 3, a water purifier was prepared in the same manner as in Example 4,
The lead removal ability was evaluated by the same water flow test as in Example 4. The results are shown in Table 2.

<Comparative Example 1> Molecular sieve 5A (manufactured by Union Showa Co., Ltd.) and bentonite were mixed so that the molecular sieve 5A: bentonite = 90: 10% by weight, water was sprayed and granulated at 110 ° C. After drying for 2 hours, classify to 150-500 μm and then 70
Firing was performed at 0 ° C. for 2 hours to obtain an adsorbent for a water purifier. A lead adsorption test was conducted on the water purifier adsorbent under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Example 2 Hydroxyapatite 35
% Slurry (manufactured by Ube Materials) at 110 ° C for 2
After drying for an hour, it was classified to 150 to 500 μm to obtain an adsorbent for a water purifier. A lead adsorption test was conducted on the water purifier adsorbent under the same conditions as in Example 1. The results are shown in Table 1.

<Comparative Example 3> Using the adsorbent for a water purifier prepared in the same manner as in Comparative Example 1, a water purifier was prepared in the same manner as in Example 4.
The lead removal ability was evaluated by the same water flow test as in Example 4. The results are shown in Table 2.

<Comparative Example 4> Using the adsorbent for a water purifier prepared in the same manner as in Comparative Example 2, a water purifier was prepared in the same manner as in Example 4,
The lead removal ability was evaluated by the same water flow test as in Example 4. The results are shown in Table 2.

[0045]

[Table 1]

[Table 2]

From the above Examples and Comparative Examples, it can be seen that the adsorbent for water purifiers of the present invention exhibits high lead adsorption performance, and also has high lead removal performance as a water purifier.

[0047]

The adsorbent for water purifiers of the present invention comprises aluminosilicate-based inorganic ion exchangers and / or titanium silicate-based compounds which are granulated using a calcium phosphate-based compound as a binder. High lead adsorption performance. Further, the method for producing an adsorbent for a water purifier of the present invention is a method in which a powder of an aluminosilicate inorganic ion exchanger or / and a powder of a titanium silicate compound is added to a mixed slurry of calcium phosphate compound powder and water. Since the mixture is mixed and then dried and granulated, the performance of the adsorbent is not deteriorated. Furthermore, the water purifier of the present invention uses an adsorbent for a water purifier in which an aluminosilicate-based inorganic ion exchanger or / and a titanium silicate-based compound are granulated using a calcium phosphate-based compound as a binder. It is possible to exert a heavy metal removing performance for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an apparatus preferably used in an embodiment of the present invention.

[Explanation of symbols]

1 outer container 2 first water purification tank 3 resin frame 4 Adsorbent laminate 5 resin frame 6 entrance 7 second water purification tank 8 Porous hollow fiber membrane 9 Flow sensor 10 Flow rate display and control unit 11 outlet 12 water pipes

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 20/30 B01J 20/30 F term (reference) 4D024 AA02 AB11 AB16 BA02 BA05 BA07 BB01 BB06 CA13 DA03 DA04 DA05 DB05 DB26 DB27 4G066 AA30A AA30B AA50A AA61A AA61B BA20 BA26 BA35 CA46 DA07 EA20 FA22 FA27 FA28 FA34

Claims (11)

[Claims] 1. An aluminosilicate inorganic ion exchanger,
Or / and an adsorbent for a water purifier obtained by granulating a titanium silicate compound and a calcium phosphate compound. 2. The adsorbent for a water purifier according to claim 1, which has an average particle size of 20 to 750 μm. 3. The adsorbent for a water purifier according to claim 1, wherein the content of the calcium phosphate-based compound is 10% by weight or more. 4. The aluminosilicate-based inorganic ion exchanger comprises a molecular sieve 3A and a molecular sieve 4.
A, molecular sieve 5A, molecular sieve 13
The adsorbent for a water purifier according to any one of claims 1 to 3, which is at least one kind selected from synthetic zeolite X. 5. The adsorbent for a water purifier according to claim 1, wherein the titanium silicate compound has a specific surface area of 100 m ² / g or more. 6. The adsorbent for a water purifier according to claim 1, wherein the calcium phosphate compound is at least one selected from hydroxyapatite, tricalcium phosphate and tetracalcium phosphate. 7. The lead adsorption amount of the water purifier adsorbent is 200.
The adsorbent for a water purifier according to any one of claims 1 to 6, which has a compressive strength of not less than mg / g and greater than 1.0 N / mm ² . 8. A water purifier for adding powder of an aluminosilicate-based inorganic ion exchanger or / and powder of a titanium silicate-based compound to a mixed slurry of calcium phosphate-based compound powder and water, mixing and drying the mixture. Adsorbent manufacturing method. 9. The method for producing an adsorbent for a water purifier according to claim 8, wherein the drying temperature is 80 to 150 ° C. 10. The method for producing an adsorbent for a water purifier according to claim 8, which is dried and then calcined at 300 to 700 ° C. 11. A water purifier using the adsorbent for a water purifier according to claim 1.