WO2018181659A1

WO2018181659A1 - Heavy metal adsorbent

Info

Publication number: WO2018181659A1
Application number: PCT/JP2018/013109
Authority: WO
Inventors: 淳任櫻井; 藤原　隆; 浩司黒崎; 正千代今西; 勇樹藤元
Original assignee: 水澤化学工業株式会社; 大阪ガスケミカル株式会社
Priority date: 2017-03-30
Filing date: 2018-03-29
Publication date: 2018-10-04
Also published as: CN110475608A; KR20190132389A; JP2018167178A; CN110475608B; JP6858055B2; TW201840486A

Abstract

This heavy metal adsorbent comprises silica-magnesia composite particles in which silica and magnesium oxide are integrally combined, wherein a pore volume with a pore diameter of 3.5 to 10.0 nm, measured using a mercury penetration method, is in the range of 0.26 to 0.50 mL/g, the pore volume with a pore diameter of 3.5 to 5000.0 nm is in the range of 1.30 to 2.50 mL/g, and the compressive strength is at least equal to 1.5 MPa. This heavy metal adsorbent is inexpensive, does not contain aluminum, and has good performance for removing heavy metals, in particular lead, from flowing water.

Description

Heavy metal adsorbent

The present invention relates to a heavy metal adsorbent, and more particularly to a heavy metal adsorbent that is excellent in lead adsorptivity and that is suitably used as a water purification material.

Conventionally, amorphous titanosilicate compounds, X-type zeolites, A-type zeolites and the like are known as heavy metal adsorbents that adsorb lead and the like (see Patent Document 1).
In such heavy metal adsorbents, amorphous titanosilicate compounds have a problem that they are quite expensive. On the other hand, zeolite-based materials contain aluminum, so that there is a problem that aluminum is eluted. Therefore, use as a filter of a water purifier is restricted, for example.

In addition, it has been reported that silica magnesia preparations and magnesium surface-treated silica gel particles are excellent in adsorption capacity for heavy metals such as iron (see Patent Documents 2 and 3). The prices of these silica magnesia preparations and the like are very inexpensive, do not contain aluminum, and are excellent in the saturated adsorption amount of heavy metals. However, such adsorbents have the disadvantage that their ability to remove heavy metals in running water is extremely low.

WO2004 / 039494 JP 2005-8676 A JP2015-178064

Accordingly, an object of the present invention is to provide a heavy metal adsorbent that is inexpensive, does not contain aluminum, and has high removal performance for heavy metals, particularly lead, in running water.
Another object of the present invention is to provide a heavy metal adsorbent that has particularly high removal performance and can therefore be suitably used as a filter for a water purifier.
In this specification, unless otherwise specified, the removal performance is the breakthrough life. The breakthrough refers to a state in which the adsorbent is saturated and the adsorption ability is lost, and the adsorption target passes through the adsorbent without being adsorbed. The breakthrough life means a period until breakthrough of a certain ratio or more occurs macroscopically. In this application, it is set as the time of the heavy metal concentration of filtered water exceeding 20% of sample water. When the adsorbent has passed the breakthrough life, its performance deteriorates and heavy metals cannot be sufficiently removed. That is, a long breakthrough life means that the adsorbent removal performance is high.

The present inventors examined the heavy metal adsorption ability of an inexpensive silica magnesia-based preparation. As a result, it was found that by calcining this preparation at a temperature of 300 to 830 ° C., not only the saturated adsorption amount to lead is improved, but also its removal performance is remarkably improved, and the present invention has been completed.

According to the present invention, it is composed of silica magnesia composite particles in which silica and magnesium oxide are integrally combined, and the pore volume at a pore diameter of 3.5 to 10.0 nm measured by mercury porosimetry is 0.26 to 0. A heavy metal adsorbent having a pore volume in the range of 1.30 to 2.50 mL / g at 50 mL / g, 3.5 to 5000.0 nm, and a compressive strength of 1.5 MPa or more. Is provided.

In the heavy metal adsorbent of the present invention,
(1) A silica component and a magnesia component are represented by the following formula:
R = Sm [mass%] / Mm [mass%]
Where
Sm is the content of the silica component in terms of SiO ₂ ,
Mm is the content of the magnesia component in terms of MgO.
Containing the mass ratio R represented by the formula 1.3 to 3.0,
(2) For a mixture of 3 g of the above heavy metal adsorbent and 50 g of activated carbon, sample water with a lead concentration of 0.05 mg / L was used, and at a filtration flow rate of 3 L / min, in accordance with JIS S-3201 household water purifier test method. When the soluble lead filtration ability test is performed, the amount of filtrate water until the lead concentration of filtrate exceeds 20% of the sample water is 250 L or more per gram of the heavy metal adsorbent,
(3) Be used for water purification materials
Is preferred.

According to the present invention, there is also provided a water purification material characterized in that the heavy metal adsorbent is contained in an amount of 1 to 30 parts by mass per 100 parts by mass of activated carbon.

Further, according to the present invention, there is provided a water purifier characterized by incorporating a water purification material using the heavy metal adsorbent.

Furthermore, according to this invention, the water purifier characterized by incorporating the said water purification material is provided.

The heavy metal adsorbent of the present invention is not only inexpensive, but particularly has high adsorbability for lead. For example, the saturated adsorption amount for lead is equal to or higher than that of conventionally known silica magnesia preparations, but particularly about twice or more higher in breakthrough life.
In addition, the heavy metal adsorbent is composed of silica magnesia composite particles in which silica and magnesium oxide are integrally combined and does not contain aluminum, so there is no problem of aluminum elution.
Furthermore, since this heavy metal adsorbent has a high particle strength, it is difficult for the particles to collapse. Therefore, it is difficult to cause performance degradation due to particle collapse (for example, generation of a short path due to partial blockage of the filter by the collapsed particles), and for example, adsorption performance can be exhibited over a long period even in flowing water.

Therefore, the heavy metal adsorbent of the present invention is particularly suitable as a water purification material used in waterworks and the like. Furthermore, the water purification material obtained by mixing the heavy metal adsorbent of the present invention with another adsorbent is extremely suitable as a filter for a water purifier.

<Heavy metal adsorbent>
The heavy metal adsorbent of the present invention comprises silica magnesia composite particles in which silica and magnesium oxide (magnesia) are integrally combined. In the silica-magnesia composite particle, silica and magnesia are in close contact with each other without a chemical bond involving recombination or exchange of atoms. That is, silica and magnesia are not physically separated, and the silica magnesia composite particles of the present invention are completely different from a simple mixture of silica and magnesia.
In addition, the fact that the silica magnesia composite particles are not a simple mixture of silica and magnesia indicates that the lead adsorption performance of the adsorbent of the present invention is silica (Comparative Example 1) and It is understood that it is far superior to any of magnesia (Comparative Example 2).

The silica magnesia composite particles constituting the heavy metal adsorbent of the present invention have a pore volume of 0.26 to 0.50 mL / g at a pore diameter of 3.5 to 10.0 nm measured by mercury porosimetry, 3.5 The pore volume at ˜5000.0 nm is in the range of 1.30 to 2.50 mL / g. Silica magnesia composite particles having such a pore volume are obtained by integrally combining silica and magnesia by a heat treatment called firing. In this respect, for example, unsintered silica magnesia disclosed in Patent Documents 2 and 3 is clearly different from the silica magnesia composite particles of the present invention. Hereinafter, the silica magnesia composite particles may be referred to as silica magnesia composite fired particles.
For example, the silica magnesia composite fired particles of the present invention have the same pore volume as that of the unfired product when the pore diameter is 3.5 to 5000.0 nm. On the other hand, the pore volume at a pore diameter of 3.5 to 10.0 nm is considerably larger than that of an unfired product.

The silica magnesia composite fired particles have higher removal performance against heavy metals, particularly lead in running water, compared to unfired products. This is presumably because the pores having a diameter of 3.5 to 10.0 nm greatly contribute to lead adsorption. That is, since the pore volume at this pore diameter is large, the saturated adsorption amount for lead is increased. Further, the contact time between the pores having such a size and the liquid containing lead becomes longer, and as a result, the breakthrough life is remarkably improved.

The breakthrough life can be evaluated, for example, as follows. That is, JIS S-3201 household water purifier test method for a mixture obtained by mixing 3 g of the heavy metal adsorbent with 50 g of activated carbon, using sample water having a lead concentration of 0.05 mg / L, and at a filtration flow rate of 3 L / min. The soluble lead filtration ability test is performed according to the above. The amount of filtrate water until the lead concentration of filtrate water that has passed through the mixture exceeds 20% of the sample water is measured. The larger the amount of filtered water, the better the removal performance for heavy metals. The amount of filtered water per 1 g of the heavy metal adsorbent of the present invention is 250 L or more. On the other hand, the amount of filtered water per 1g of unbaked product is about 170L. That is, the breakthrough life of the heavy metal adsorbent of the present invention is significantly longer than that of an unfired product.
Moreover, the saturated adsorption amount with respect to lead of the heavy metal adsorbent of the present invention is 1.7 mmol / g or more in the case of the highest performance, but is about 1.5 mmol / g in the unfired product.

Furthermore, the silica magnesia composite fired particles in the present invention have a compressive strength of 1.5 MPa or more, preferably 2.0 MPa or more, more preferably 2.5 MPa or more, in relation to being a fired product. That is, particle shrinkage occurs by firing, and as a result, compressive strength is improved.
If the compressive strength is 1.5 MPa or less, the particles may collapse. In addition, the filter using the water purification material containing such silica magnesia composite fired particles is partially clogged with the collapsed particles, which may cause differential pressure and uneven adsorption performance, There is a possibility that loss increases and a desired filtration flow rate cannot be obtained.
Incidentally, the compression strength of conventionally known silica magnesia composite unfired particles according to Patent Document 2 and the like is about 1.3 MPa, which is considerably lower than that of the present invention.
On the other hand, an excessively high compressive strength means that firing was performed more than necessary. In this case, the obtained silica magnesia composite fired particles do not exhibit the pore distribution described above, and the adsorption performance such as the saturated adsorption amount and breakthrough life of heavy metals, particularly lead, is lowered. Therefore, in the present invention, it is suitable that this compressive strength is suppressed to 10.0 MPa or less, preferably 5.0 MPa or less, more preferably 4.7 MPa or less.

In the present invention, the fact that the compression strength of the silica magnesia composite fired particles is improved means that the particles are difficult to disintegrate, and the performance degradation of the heavy metal adsorbent due to the disintegration of the particles can be effectively avoided.
As shown in the examples described later, when silica magnesia composite calcined particles are put into a certain amount of water and ultrasonically dispersed, the volume average particle diameter after ultrasonic dispersion (median measured by laser diffraction scattering method) The diameter is about 68% before ultrasonic dispersion when the compressive strength is 2.5 MPa, and about 80% before ultrasonic dispersion when the compressive strength is 4.7 MPa. On the other hand, when the same test is performed on the unsintered particles, the volume average particle size is reduced to about 30% before ultrasonic dispersion. Therefore, in the silica magnesia composite fired particles of the present invention, a decrease in the average particle size is suppressed, that is, particle collapse is effectively suppressed.
Thus, in the present invention, the silica magnesia composite fired particles used as the heavy metal adsorbent are very difficult to disintegrate. Therefore, when the silica magnesia composite fired particles are used by mixing with other adsorbents, it is possible to effectively prevent performance degradation due to particle collapse during the mixing operation. Moreover, even when used in running water, it is possible to effectively avoid performance degradation due to particle collapse, and to stably exhibit heavy metal adsorption performance over a long period of time.

Furthermore, the silica magnesia composite fired particles used as a heavy metal adsorbent generally have a silica component and a magnesia component represented by the following formula:
R = Sm [mass%] / Mm [mass%]
Where
Sm is the content of the silica component in terms of SiO ₂ ,
Mm is the content of the magnesia component in terms of MgO.
Is contained in the range of 0.1 to 50, 1.3 to 3.0, more preferably 1.5 to 2.5, This is preferable in that the degree of integration of silica and magnesia is high and particle collapse is suppressed. That is, when the mass ratio of silica and magnesia is in the above range, both components are distributed in a balanced manner and are combined and integrated, and stable and homogeneous adsorption performance can be exerted on heavy metals.

Unlike the zeolite, the silica magnesia composite fired particles do not contain aluminum. Therefore, when this is used as a water purification material, the problem of aluminum elution does not occur.
Moreover, the ignition loss (1000 degreeC x 30 minutes, 150 degreeC drying reference | standard) is 10 mass% or less in connection with being a baked product.
The ignition loss corresponds to the amount of SiOH groups, and the larger the ignition loss, the more SiOH groups remain in the silica magnesia composite fired particles. As will be described later, since it is presumed that the pore distribution and compressive strength of the particles change with the dehydration condensation of SiOH groups by firing, the ignition loss is an index indicating the degree of firing. Therefore, the mass ratio R described above indicates that the pore distribution of the silica magnesia composite fired particles is in the above-described range and is fired under conditions (for example, a firing temperature and a firing time) with high compressive strength. Depending on the above conditions, the ignition loss is preferably 4.0 to 8.2% by mass, more preferably 4.5 to 7.6% by mass.

<Manufacture of heavy metal adsorbent (silica magnesia composite fired particles)>
The silica magnesia composite calcined particles described above are prepared by mixing (A) silica (silicon dioxide) and (B) magnesia (magnesium oxide) or magnesia hydrate homogeneously in the presence of moisture to prepare an aqueous slurry. Next, aging is performed, and further, moisture is removed, followed by firing.

That is, (A) silica, which is one of the raw materials, is finely divided into colloidal particles or fine aggregated particles (primary or secondary particles) by homogeneous mixing in water, for example, in water. When (B) magnesia which is the other raw material is put into water and stirred or pulverized, it hardly dissolves. However, due to partial hydration on the surface of the magnesia particles, crystals (or newly formed hydrates) At least a part of the crystal) is disintegrated or exfoliated to form fine particles made of magnesia and / or magnesia hydrate and dispersed in water (fine particles).

In the aging step, when water is removed from the aqueous slurry in which these fine particles are uniformly dispersed and the solid concentration increases, (A) silica particles and (B) magnesia particles gradually or rapidly. To the integrated form without chemical bonding such as exchange of atoms and recombination (completion of integration). That is, the silica magnesia composite fired particles of the present invention have an integrated structure so as not to be separated by physical means.

In order to produce the heavy metal adsorbent of the present invention described above, (A) silica and (B) magnesia or magnesia hydrate are used as raw materials. All of these are approved in Japan as filter aids or adsorbents for food production. Therefore, the use as a food refining is not limited by these uses.

When, for example, magnesium hydroxide, magnesium chloride, magnesium sulfate, magnesium nitrate, or the like is used as a raw material instead of (B) magnesia particles, sufficient fine particles cannot be formed. Furthermore, when (A) the silica particles and the magnesium component are contacted in water and / or when calcination is performed, chemical bonds such as (A) exchange of atoms and recombination with the silica particles occur. May occur. In the case of such a chemical bond in the (B) magnesia particles that are the raw material of the present invention, since a pore structure peculiar to the heavy metal adsorbent of the present invention may not be formed, magnesium oxide is used in particular. It is preferable to do.

Further, as the silica (A) and magnesia or magnesia hydrate (B), it is preferable to select those that facilitate the above-mentioned fine particle formation.
For example, as the silica, amorphous water-containing silica is suitable, and it may be produced by either gel method or precipitation method. The silica particles preferably have small primary particles, and the specific surface area is preferably 40 m ² / g or more, particularly 140 m ² / g or more.
Further, as magnesia or magnesia hydrate, those having small crystallites and not progressing carbonation with time are preferable. For example, a magnesia powder having a specific surface area of 2 m ² / g or more, preferably 20 m ² / g or more, particularly preferably 50 m ² / g or more is used.

In the preparation of the above aqueous slurry, the amount of (A) silica and (B) magnesia or magnesia hydrate used is set so that the aforementioned mass ratio R falls within a predetermined range.

The degree of integration is different depending on the mass ratio R of the silica component and the magnesia component in the adsorbent. For example, a mass ratio of about 2 and preferably 1.3 to 3.0 is suitable for integrally combining a silica component and a magnesia component. Therefore, as shown in the examples described later, it is possible to obtain silica magnesia composite fired particles having a very high degree of integration and high removal performance against heavy metals, particularly lead, in running water.

In the preparation of the aqueous slurry, there is no restriction on the raw materials (A), (B), the order of water, etc., but when the aggregation or gelation phenomenon (thickening) occurs, the above-mentioned fine particle formation or integral composite Progress may be hindered. For this reason, the one where the solid content concentration of an aqueous slurry is low is preferable. On the other hand, it is better that the solid content concentration is high from the viewpoint of productivity and economy. Accordingly, the solid content concentration is preferably 3 to 15% by mass, particularly 8 to 13% by mass.

In addition, the preparation of the aqueous slurry by the above homogeneous mixing and the subsequent aging are generally carried out with stirring in a stirring vessel equipped with a stirring blade, but are carried out under pulverization or dispersion with a wet ball mill or a colloid mill. Can also be done.
In addition, such homogeneous mixing and aging is preferably performed under heating in order to complete integration of particles in a short time. However, when the heating temperature is high, gelation occurs and the composite particles become inhomogeneous. Cheap. Therefore, this heating temperature is usually 100 ° C. or less, preferably 50 to 97 ° C., particularly preferably 50 to 79 ° C. Further, for example, an aqueous solution containing a granular material in which silica particles and magnesia particles are integrally combined by performing homogeneous mixing and aging for 0.5 hours or more, particularly 1 to 24 hours, more preferably about 3 to 10 hours. A slurry is obtained.

Water removal after aging can be performed by evaporation drying using a spray dryer or a slurry dryer. Moreover, after performing a certain amount of dehydration by means such as filtration or centrifugation, drying may be performed using a box dryer, a band dryer, a fluidized bed dryer or the like. Drying is preferably performed at a temperature in the range of 110 to 200 ° C. At this time, (B) magnesia hydrate is dehydrated, and part or all of the hydrated water is removed.

As described above, silica magnesia composite particles having a water content of 10% by mass or less, in which at least a part of silica particles and magnesia particles are intimately integrated by dehydration, for example, are granular, powdery, cake-like or nodules. Obtained in the form. If necessary, these are pulverized, classified, or molded, and then fired in a firing furnace to obtain composite fired particles in which silica particles and magnesia particles are integrally combined.

The above pulverization can be performed by a known dry pulverization method. For example, an impact pulverizer such as an atomizer, a dry ball mill, a roller mill, or a jet mill can be used.
The classification is performed by gravity classification, centrifugal classification, inertia classification, or the like using an ordinary dry classifier.
By such pulverization and classification, silica magnesia composite particles that are not subjected to heat treatment by firing, for example, in the form of a powder having a fine particle content of less than 5 μm of 20% by volume or less are obtained.

Moreover, the said shaping | molding can be performed by arbitrary methods, such as rolling granulation, fluidized bed granulation, stirring granulation, crushing granulation, compression granulation, extrusion granulation. In general, it is preferable to form the particles so that the particles do not become too hard and do not easily powder.
By such molding, for example, a spherical unfired silica having a spherical shape having a diameter of 5 μm to 5 mm, an elliptical spherical shape having a major axis of 5 μm to 5 mm, or a cylinder having a diameter of 0.5 mm or more and an axial length of 50 mm or less. Magnesia composite particles are obtained.

Examples of silica magnesia composite particles that have not been subjected to heat treatment by firing are commercially available from Mizusawa Chemical Co., Ltd. under the trade name “Mizuka Life”. In the present invention, for example, silica magnesia composite fired particles can be obtained by firing “Mizuka Life” manufactured by Mizusawa Chemical Industry Co., Ltd. as shown in the examples described later.

In the present invention, in order to use the silica magnesia composite calcined particles as a heavy metal adsorbent, the above calcining is performed at 300 to 830 ° C., preferably 400 to 800 ° C., more preferably 400 to 750 ° C., particularly preferably 550 to 550 ° C. It is important to carry out at a temperature of 750 ° C. By firing at such a temperature, silica magnesia composite fired particles having the above-described pore distribution and compressive strength can be obtained. That is, such firing probably causes partial dehydration condensation of SiOH groups present inside the unfired particles, resulting in fluctuations in pore diameter, resulting in pore diameter contributing to adsorption of heavy metals (particularly lead). It seems that the pore volume of 3.5-10.0 nm increases to the above-mentioned range. Further, as a result of the shrinkage of the particles due to firing, the compressive strength is increased to the above-described range.

For the calcined particles having a calcining temperature lower than the above range, the pore volume at a pore diameter of 3.5 to 10.0 nm is lower than the aforementioned range. As a result, the fired particles obtained do not exhibit the adsorption performance for lead as in the present invention, have a low compressive strength, and are easily collapsed. The same applies to the unsintered particles that are simply removed by drying.
When the firing temperature is higher than the above range, the degree of particle shrinkage is large, so that the compressive strength is higher and particle collapse is suppressed. On the other hand, as a result of crushing the pores, the pore volume, especially the pore volume with a pore diameter of 3.5-10.0 nm, is reduced, resulting in a decrease in saturated adsorption amount and shortened breakthrough life. Decrease.

In the present invention, the firing as described above is performed so that the pore volume at a pore diameter of 3.5 to 10.0 nm falls within the above-described range. For example, the baking may be performed at the above temperature for 0.5 to 5 hours, preferably 2 to 4 hours.

The composite calcined particles thus obtained (that is, the heavy metal adsorbent of the present invention) are obtained in the form of granules, powders, cakes or nodules, and are granulated into particles of an appropriate size to adsorb heavy metals. Used as an agent.
As granulation means, it can carry out by publicly known means, such as spray granulation and rolling granulation. When a large load is applied to the particles, the pore distribution may be out of the above-mentioned range, and thus means that do not apply the load as much as possible, for example, spray granulation is particularly suitable.

In the present invention, the silica magnesia composite calcined particles have a silica component and a magnesia component that are not separated from each other and are closely integrated, so that the pH of the suspension is usually 6.0 to 10.0. It is in the range.

In the present invention, the BET specific surface area measured by the nitrogen adsorption method is 100 m ² / g or more, more preferably 400 m ² / g or more, particularly 500 m ² in that the silica magnesia composite fired particles can stably adsorb heavy metals. / G or more is preferred.

The heavy metal adsorbent of the present invention is excellent in adsorption performance for heavy metals such as lead, manganese, chromium, nickel, vanadium, copper and iron, particularly lead. Furthermore, since aluminum is not contained, there is no problem of aluminum elution. Therefore, it is suitably used as a water purification material.

In addition, since particle strength is high and particle disintegration is unlikely to occur, even when used in admixture with activated carbon and / or other adsorbents, performance does not deteriorate due to particle disintegration, and adsorption performance is stable. Demonstrated. Therefore, it is suitable for the use which arrange | positions and uses in running water as a water purification material. In particular, it is most preferable to use a mixture with activated carbon and / or other adsorbents having excellent adsorptivity to various organic substances and halides.

Thus, when mixed with activated carbon and used as a water purification material, the heavy metal adsorbent of the present invention is generally used in an amount of 1 to 30 parts by mass per 100 parts by mass of activated carbon. In particular, since the heavy metal adsorbent of the present invention is inexpensive, it can be used effectively as a water purification material, and the water purification material using the heavy metal adsorbent of the present invention or a combination of such heavy metal adsorbent and activated carbon, It is suitable as a cartridge type filter for a water purifier, particularly a household water purifier.

Other adsorbents are not particularly limited, but include, for example, titanosilicate compounds, various silicates such as magnesium silicate; various zeolites such as A-type zeolite and X-type zeolite; sepiolite, attapulgite, dosonite, montmorillonite, Various clays such as hydrotalcite; various ion exchange resins;

As described above, the heavy metal adsorbent of the present invention is composed of silica magnesia composite particles in which silica and magnesia approved as food additives are integrally combined, and can be effectively applied to food refining applications. For example, it can be used for the purpose of removing the heavy metal from the oil pump which has deteriorated by repeated use and has increased the content of heavy metals such as copper and iron. Similarly, by removing heavy metals from raw materials and boiled juice of concentrated seasonings such as fish shellfish extract and meat extract that contain a lot of heavy metals, the browning reaction (Maillard reaction) during heating and concentration is suppressed, and flavor and nutritional value of It is effectively used for various purposes such as the purpose of preventing the decrease. It can also be used effectively for the purpose of purification by adsorption and removal of heavy metals as impurities from widely useful liquids other than food.

The heavy metal adsorbent of the present invention has a high saturated adsorption amount and is excellent in suppressing elution after heavy metal adsorption. For this reason, it is also effective to use the heavy metal adsorbent of the present invention as a heavy metal insolubilizing material for an object to be treated contaminated with heavy metals such as incineration ash, sewage sludge, and soil.

The excellent effect of the present invention will be explained by the following experimental example.

(1) Pore volume It measured by the mercury intrusion method using AutoPore IV 9500 by Micromeritics. The pore volume when the pore diameter is 3.5 to 10.0 nm is obtained from the indentation amount of 20000 to 60000 psia, and the pore volume when the pore diameter is 3.5 to 5000.0 nm is obtained from the indentation amount of 30 to 60000 psia. It was.

(2) Compressive strength The compressive strength of 20 particles of each heavy metal adsorbent was measured using a micro compression tester MCT-510 manufactured by Shimadzu Corporation, and the median value was defined as the compressive strength of the heavy metal adsorbent.

(3) Saturated adsorption amount Sample water (lead nitrate (II) aqueous solution) having a lead concentration of 2000 ppm was prepared. 2.5 g of a heavy metal adsorbent was added to 1 L of this sample water, and the pH was adjusted to 4-5 with a nitric acid solution. The resulting mixture was stirred overnight and the heavy metal adsorbent was removed by filtration. The lead concentration of the filtrate was measured by flame atomic absorption spectrometry using ZA3000 manufactured by Hitachi High-Tech Science Co., Ltd. The amount of heavy metal adsorption was calculated from the lead concentration before and after the test, and was used as the saturated adsorption amount.

(4) Breakthrough life 3 g of heavy metal adsorbent and 50 g of activated carbon were mixed to prepare a water purification material and incorporated into a water purifier. Based on JIS S-3201 (Household water purifier test method-Dissolvable lead filtration ability test), sample water (lead nitrate (II) nitrate aqueous solution) with a lead concentration of 0.05 mg / L was prepared, and the above water purifier was I passed water. The flow rate of the sample water was 3 L / min (linear velocity LV = 2.5 cm / s). The amount of filtered water (L / g) required until the lead concentration of the filtered water exceeded 20% of the sample water was determined, and the breakthrough life was evaluated.

(5) Retention rate of average particle diameter The disintegration property in water by ultrasonic dispersion was evaluated using a laser diffraction scattering type particle size distribution measuring instrument master sizer 3000 with an ultrasonic dispersion function manufactured by Malvern. Retention rate of average particle diameter from the median diameter Dn measured as the ultrasonic intensity 0% (no ultrasonic dispersion) and the median diameter Dus measured as the ultrasonic intensity 100% in the dispersion before dispersion (dispersion time 180 seconds) (%) The following formula:
ΔD = Dus / Dn × 100
Where
ΔD: Retention rate of average particle diameter Dus: Volume average particle diameter after ultrasonic dispersion Dn: Calculated by volume average particle diameter before ultrasonic dispersion.

(6) Loss on ignition Loss on ignition (mass%) is obtained by calcining a heavy metal adsorbent dried at 150 ° C. for 2 hours at 1000 ° C. for 30 minutes and then allowing it to cool. Based on.

Table 1 shows the physical properties and heavy metal adsorption test results of the heavy metal adsorbents shown in the following Examples and Comparative Examples.

(Comparative Example 1)
Mizusawa Chemical Industry Co., Ltd. silicon dioxide Mizukasorb C-1 was used as a heavy metal adsorbent.

(Comparative Example 2)
Magnesium oxide Starmag U manufactured by Kamishima Chemical Industry Co., Ltd. was used as a heavy metal adsorbent.

(Comparative Example 3)
Mizuka Life F-1G (R = 2.1) was used as a heavy metal adsorbent.

Example 1
The silica magnesia preparation used in Comparative Example 3 was calcined at 550 ° C. for 4 hours and used as a heavy metal adsorbent.

(Example 2)
The silica magnesia preparation used in Comparative Example 3 was calcined at 750 ° C. for 2 hours and used as a heavy metal adsorbent.

(Comparative Example 4)
The silica magnesia preparation used in Comparative Example 3 was calcined at 900 ° C. for 2 hours and used as a heavy metal adsorbent.

Claims

It is composed of silica magnesia composite particles in which silica and magnesium oxide are integrally combined, and the pore volume at a pore diameter of 3.5 to 10.0 nm measured by mercury porosimetry is 0.26 to 0.50 mL / g, 3 A heavy metal adsorbent having a pore volume in the range of 1.30 to 2.50 mL / g and a compressive strength of 1.5 MPa or more at 0.5 to 5000.0 nm.
The silica component and the magnesia component are represented by the following formula:
R = Sm [mass%] / Mm [mass%]
Where
Sm is the content of the silica component in terms of SiO 2 ,
Mm is the content of the magnesia component in terms of MgO.
The heavy metal adsorbent according to claim 1, which is contained in a range where the mass ratio R represented by
A mixture of 3 g of the heavy metal adsorbent and 50 g of activated carbon was dissolved in accordance with JIS S-3201 household water purifier test method at a filtration flow rate of 3 L / min using sample water with a lead concentration of 0.05 mg / L. 2. The heavy metal adsorbent according to claim 1, wherein when a lead filtration ability test is performed, the amount of filtrate water until the lead concentration of filtrate exceeds 20% of the sample water is 250 L or more per 1 g of the heavy metal adsorbent.
The heavy metal adsorbent according to claim 1, which is used as a water purification material.
A water purification material comprising the heavy metal adsorbent according to claim 4 in an amount of 1 to 30 parts by mass per 100 parts by mass of activated carbon.
A water purifier incorporating a water purification material using the heavy metal adsorbent according to claim 4.
A water purifier incorporating the water purification material according to claim 5.