JP7190702B2 - dehydration accelerator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dehydration accelerator used for dewatering muddy water such as sludge with high water content and sewage (polluted wastewater).

The bottom sediment of lakes and marshes contaminated with radioactive substances (high water content sludge) and muddy water such as decontaminated water from decontaminated land, roads, and buildings contain solids such as mud containing radioactive substances. there is A flocculant for decontaminating water treatment that removes such solids by flocculation and sedimentation and performs solid-liquid separation has been proposed (see, for example, Patent Document 1). The flocculant described in Patent Document 1 contains binos powder obtained by drying Parachlorella sp.binos.

Flocculants containing gypsum powder have been proposed for settling solids (turbid suspended solids, etc.) in various types of sludge and polluted wastewater (see, for example, Patent Documents 2, 3, and 4). In addition, a flocculant using inorganic natural minerals such as aluminum sulfate, potassium sulfate, and sodium carbonate as main raw materials has been proposed (see, for example, Patent Document 5). The flocculant described in Patent Document 4 forms solid flocs in a short period of time and settles them, and also makes heavy metals, some halogens, metalloid elements, etc. contained in the water to be treated insoluble. be able to.

However, no attention has been paid to the crystal structure of the gypsum powder that has been used as a flocculating agent. Also, the particle size was not specified in particular. There is a demand for a dehydration accelerating material that accelerates dehydration by more quickly settling solids such as mud contained in muddy water, and that can provide highly transparent treated water containing as few solids as possible.

Japanese Unexamined Patent Application Publication No. 2014-1963 JP 2010-172883 A JP 2010-172882 A JP-A-2003-94100 JP-A-2005-95880

An object of the present invention is to provide a dehydration accelerator that is excellent in dispersibility in sludge and polluted wastewater, allows solids to settle efficiently, and can separate water from solids more rapidly.

The dehydration accelerator according to the present invention is a dehydration accelerator containing anhydrite, and the anhydrite has an average particle diameter D50 of 5 to 100 μm, and the peak intensity obtained by X-ray diffraction is (020 ) plane peak intensity (I ₍₀₂₀₎ ) and (102) plane peak intensity (I ₍₁₀₂₎ ) ratio (I ₍₀₂₀₎ /I ₍₁₀₂₎ ) is 5 or more. do.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a dehydration accelerating material which is excellent in dispersibility in sludge/contaminated wastewater, can efficiently settle solid content, and can more quickly separate water from solid content.

1 is a scanning electron microscope (SEM) photograph of the surface of natural anhydrite. It is a SEM photograph of the surface of industrial anhydrite.

Hereinafter, embodiments of the present invention will be described in detail.
The dehydration accelerator of the present invention contains anhydrite, particularly natural anhydrite. In the present invention, for example, natural anhydrite (produced in Thailand) can be used. The physical properties are shown below in comparison with industrial anhydride gypsum (manufactured by Asahi Glass Co., Ltd.).

<Average particle size D50>
The average particle diameter D50 obtained from the wet particle size distribution of each anhydrite is summarized in Table 1 below. Water was used as the dispersion medium, and after pretreatment by ultrasonic dispersion, the particle size distribution was measured using a particle size distribution analyzer (manufactured by Microtrack Bell Co., Ltd.).

It was confirmed that natural anhydrite has a significantly larger average particle size D50 than industrial anhydrite. A large average particle diameter D50 is advantageous in terms of improving dispersibility in muddy water.
If the average particle size D50 of the natural anhydrite is as small as less than 5 μm, it may not disperse well in muddy water, possibly impairing its function as a dehydrating agent. On the other hand, if the average particle size D50 of the natural anhydrite exceeds 100 μm, it is not preferable in that the particle size diverges from that of other components and segregation may occur. Therefore, in the present invention, natural anhydrite having an average particle size D50 of 5 to 100 μm is used. The average particle size D50 of the natural anhydrite is preferably 10-40 μm, more preferably 15-30 μm.

<Dry particle size comparison>
Table 2 below summarizes the dry particle size of each anhydrite. The dry particle size was measured using a 150 μm sieve and a 90 μm sieve.

Natural anhydrite was shown to have a lower percentage of particles on a 150 μm sieve than engineered anhydrite. This result indicates that the particle size of natural anhydrite is more uniform than that of industrial anhydrite. A comparison of the SEM photographs of FIGS. 1 and 2 shows that the natural anhydrite has a larger particle size than the industrial anhydrite.

Table 3 below summarizes the contents of components contained in natural anhydrite and industrial anhydrite. The content of each component was determined by ICP analysis.

The content of CaO can be considered equivalent if it is within the range of 30-50% _, and the content of SO3 can be considered equivalent if it is within the range of 40-60% . Therefore, no clear difference is confirmed between the natural anhydrite and the industrial anhydrite in terms of the components contained. The balance in each anhydrite is impurities and the like.

<Crystallite measurement>
Crystallites of natural anhydrite (produced in Thailand) and industrial anhydrite (produced by Asahi Glass Co., Ltd.) were measured using a fully automatic multipurpose X-ray interpretation device (D8 ADVANCE, manufactured by Bruker Aix). The measurement conditions were as follows.
・Tube voltage, tube current: 40 kV, 40 mA
・Scanning range: 20 to 50° ・Step width: 0.02° ・Measurement time: 1 S/step ・Divergence slit, light receiving slit: both 0.3°
The crystallite was calculated from the peak of the (020) plane by Scherrer's formula. Crystallites are calculated automatically by the device.
D=Kλ/(B cos θ)
(D: crystallite size, K: Scherrer constant (0.9), λ: X-ray wavelength B: peak half-width, θ: Bragg angle)
The results obtained are summarized in Table 4 below.

Natural anhydrite was confirmed to have higher peak intensity and crystallite than industrial anhydrite. Therefore, it can be seen that the natural anhydrite has a higher orientation than the industrial anhydrite.
Since natural anhydrite has a higher orientation than industrial anhydrite, it is presumed to have a fibrous shape growing in the length direction. Table 5 below shows the intensity ratio between the (020) plane and the (102) plane.

Based on the results shown in the table above, the peak intensity ratio of the natural anhydrite is, among the peak intensities obtained by X-ray diffraction, the peak intensity of the (020) plane (I ₍₀₂₀₎ ) and the peak intensity of the (102) plane. The ratio (I ₍₀₂₀₎ /I ₍₁₀₂₎ ) to the peak intensity (I ₍₁₀₂₎ ) was defined to be 5 or more. The ratio (I ₍₀₂₀₎ /I ₍₁₀₂₎ ) is preferably 50 or less, more preferably 10-40, most preferably 15-30.
If the ratio (I ₍₀₂₀₎ /I ₍₁₀₂₎ ) is too small, the orientation is not high and the fiber does not grow in the longitudinal direction, which is considered to have an adverse effect on the dispersibility in muddy water. . It was found that by setting the ratio (I ₍₀₂₀₎ /I ₍₁₀₂₎ ) to 5 or more, the dispersibility in muddy water is improved. Considering the range of intensity ratios that can be easily measured, the upper limit of the ratio (I ₍₀₂₀₎ /I ₍₁₀₂₎ ) can be about 50.

As shown in the above results, natural anhydrite has a significantly larger average particle diameter D50 than industrial anhydrite, and also has high crystallinity and high orientation. Natural anhydrite is produced in nature over a long period of time, whereas industrial anhydrite, for example phospho gypsum, requires a short period of time to produce phosphoric acid by reacting phosphate rock with sulfuric acid. generated between It is speculated that the difference in properties between natural anhydrite and industrial anhydrite is based on the difference in crystal formation rate. Due to these physical properties, the dehydration accelerator containing natural anhydrite has better dispersibility in water than industrial anhydrite, and is presumed to act effectively as a nucleus when contaminant suspended matter agglomerates.

<Dehydration accelerator>
The dehydration promoting material of the present invention can be prepared by mixing the above-described natural anhydrite with a polymer. The polymer imparts the effect of enlarging flocs by aggregation. If the amount of polymer is too small, the desired effect cannot be sufficiently obtained. On the other hand, even if the polymer is excessively blended, the effect is not significantly improved. It is preferable to use the polymer in a proportion of 10 to 15 parts by mass with respect to 100 parts by mass of natural anhydrite.

Both synthetic polymers and natural polymers may be used as the polymer. As the synthetic polymer, it is preferable to use a combination of a low anionic low molecular weight polymer having a weight average molecular weight (Mw) of about 6 million to 12 million and a strong anionic high molecular weight polymer having an Mw of about 13 million to 16 million. Low-molecular-weight polymers and high-molecular-weight polymers can be used in any ratio. For example, the mass ratio (low-molecular-weight polymer:high-molecular-weight polymer) can be about 80:20 to 40:60.

Conventionally known materials can be used as the material used as the synthetic polymer. For example, carboxylate-based polymers such as sodium acrylate, copolymers of carboxylate and acrylamide, copolymers of sulfonate and acrylamide, copolymers of alkylaminoacrylate salt and acrylamide, alkyl Copolymers of amino methacrylate salts and acrylamide and the like are included. Among these, polycarboxylate-based substances, that is, carboxylate polymers and copolymers of carboxylate and acrylamide are preferred.

Examples of the polycarboxylic acid in the copolymer of carboxylate and acrylamide include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and carboxymethylcellulose.
Examples of the sulfonic acid in the copolymer of sulfonate and acrylamide include acrylamide 2-methylpropanesulfonic acid, vinylsulfonic acid, and styrenesulfonic acid.

Alkylaminoacrylate salts in copolymers of alkylaminoacrylate salts and acrylamide include dimethylaminoethyl acrylate, dimethylaminopropylacrylamide, acryloyloxyethyltrimethylammonium chloride, acryloylaminopropyltrimethylammonium chloride and acryloyl 2-hydroxypropylide. etc. can be mentioned.

Examples of alkylamino methacrylate salts in copolymers of alkylamino methacrylate salts and acrylamide include dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide, methacryloyloxyethyltrimethylammonium chloride, methacryloylaminopropyltrimethylammonium chloride, methacryloyl 2-Hydroxypropylide and the like can be mentioned. Although the synthetic polymer used in the present invention has been described, its configuration can be changed as appropriate without departing from its effects.

Examples of natural polymers include seed polysaccharides such as guar gum, roasted gua gum, and roasted bingham; resin polysaccharides such as arabinogalactan gum and gum arabic; seaweed polysaccharides such as alginic acid and chitosan; and fruit polysaccharides such as pectin and psyllium gum. , starch, rhizome polysaccharides such as konnyaku, fibrous polysaccharides such as cellulose, microbial xanthan gum, xanquat, xanflo, curdlan, succinoglucan, and animal gelatin, casein, albumin, and shellac. Starch derivatives, guar gum derivatives, roasted guar gum derivatives obtained by subjecting starch, guar gum, roasted guar gum, cellulose, alginic acid, etc. to treatments such as oxidation, methylation, carboxymethylation, hydroxyethylation, phosphorylation, cationization, etc. , cellulose derivatives, alginic acid derivatives and the like may also be used. Although the natural polymer used in the present invention has been described, its configuration can be changed as appropriate without departing from its effects.

<Other ingredients>
The dehydration accelerator of the present invention may contain aluminum sulfate, soda ash, powdered aluminum chloride (PAC), diatomaceous earth (P1200), and the like. These components are preferably used in the following ratios, respectively, with respect to 100 parts by mass of natural anhydrite.
Aluminum sulfate: 15 to 30 parts by mass
Alginic acid: 1 to 10 parts by mass
Soda ash: 10 to 20 parts by mass
Powder PAC: 0.5 to 10 parts by mass
Diatomaceous earth: 5 to 20 parts by mass

<Production method>
The dehydration accelerator of the present invention can be produced by blending natural anhydride gypsum with a predetermined amount of polymer and components such as aluminum sulfate and mixing them using a powder mixer or the like.

Specific examples of the present invention are shown below, but they are not intended to limit the present invention.
<Selection of gypsum to be used>
First, the dehydration performance of natural anhydrite and industrial anhydrite was confirmed. Specifically, natural anhydrite and industrial anhydrite were each added to the sediment of the reservoir, and a floc formation test and a sedimentation test were conducted.

(Preparation of sample)
475 g of water was added to 25 g of bottom sediment to prepare 500 g of muddy water. 0.3 g each of natural anhydride gypsum (produced in Thailand) and industrial anhydride gypsum (manufactured by Asahi Glass Co., Ltd.) were added to the resulting muddy water to prepare samples.
(Examination content)
Floc formation test: The prepared mud containing natural anhydrite and the prepared mud containing industrial anhydrite were each stirred at a mixing speed of 200 rpm using a general-purpose agitator (general-purpose agitator BL300 manufactured by Shinto Kagaku Co., Ltd.). After 1 minute, the muddy water was filtered through a sieve (850 μm sieve mesh), and the mass of the amount remaining on the sieve was measured. The measurement results are shown in Table 6 below.

As shown in the above table, the samples using natural anhydrite are larger than the samples using industrial anhydrite in both the total mass remaining on the sieve and the dry mass after water is removed from the total mass. This is because samples to which natural anhydrite is added form flocs more favorably than samples using industrial anhydrite, and a larger amount of solid content (materials contained in the dry mass) in the mud is incorporated into the flocs. , is based on suppressing solids in the mud from passing through the sieve. That is, natural anhydrite acts more effectively as a nucleus when polluted suspended matter agglomerates than industrial anhydrite, and tends to form large flocs.

Sedimentation test: The same sample prepared in the flocculation test was stirred in the same manner as in the flocculation test, then placed in a 500 ml graduated cylinder and allowed to stand, and the amount of sedimentation was measured. In this test, raw water (muddy water without gypsum) was also measured. The measurement results are shown in Table 7 below.

As shown in the above table, about 70% of the sample using natural anhydrite settled in just over 10 seconds, and 80% settled in 1 minute. On the other hand, the sample using industrial anhydride gypsum took more than 30 seconds for 70% settling and 5 minutes for 80% settling. Samples using natural anhydrite can coagulate and settle solids in muddy water earlier than industrial anhydrite. This is based on the fact that natural anhydrite has better dispersibility in water than industrial anhydrite and can form large flocs. That is, since natural anhydrite can form flocs earlier than industrial anhydrite, it is understood that it promotes floc formation in the mud.

As shown in the above results, natural anhydrite has higher dehydration performance than industrial anhydrite, and can accelerate dehydration at an early stage. Next, a dehydration promoting material is produced using natural anhydrite.

<Preparation of dehydration promoting material>
Polymer, aluminum sulfate, alginic acid (coarse powder), soda ash, powdered polyaluminum chloride (PAC), and diatomaceous earth (P1200) are blended in the parts by mass shown in Table 8 below with respect to 100 parts by mass of natural anhydrite. Dehydration accelerators of Examples 1 to 10 were produced.

For comparison, a dehydration promoting material of a comparative example was produced in the same formulation as in Example 3, except that natural anhydrite was changed to industrial anhydrite.

<Sample evaluation>
In order to evaluate the dehydration-promoting materials of Examples 1 to 10 and the dehydration-promoting materials of Comparative Examples produced as described above, 25 g of bottom soil collected from a predetermined reservoir in Fukushima Prefecture and 475 g of tap water were mixed. to prepare 500 g of sewage. The samples were added to the sewage to form flocs, and the flocculation rate, floc size, pH of the drinking water, and clarity of the drinking water were investigated.
The muddy water was placed in a 1-liter glass beaker, and 0.3 g (0.06% by mass) of a dehydration accelerator was added to each. Using a general-purpose stirrer (BL300 manufactured by Shinto Kagaku Co., Ltd.), the dehydration accelerating agent and sewage were mixed by stirring at a rotation speed of 200 rpm while visually observing.
Visual observation of the state of dispersion of the dehydration accelerators in the sewage confirmed that the dehydration accelerators of Examples 1 to 10 were better dispersed than the dehydration accelerators of the comparative examples.

<Flock formation speed>
The time (t _F ) from the start of mixing to the formation of flocs was measured, and the flocculation rate was evaluated as follows.
◎: t _F ≤ 30 sec
○: 30 sec < _tF ≤ 60 sec
△: 60 sec < _tF ≤ 120 sec
×: _tF > 120 sec
The flocculation rate was also marked as "x" when flocculation was not formed.
As for the flocculation rate, "Δ", "○", and "⊚" are acceptable.

<Size of flock>
Wastewater containing flocs was separated using a circular sieve with an opening of 850 μm, and the size of the flocs remaining on the sieve was measured. The size of flocs refers to the size of flocs formed in muddy water, and was obtained by visual observation and measurement from the outside of the beaker. If the size of the floc is 5 mm or more and 10 mm or less, it is defined as "large", and if it is 1 mm or more and less than 5 mm, it is defined as "small".

<Evaluation of Moisture Under Sieve>
The pH of the moisture under the sieve was measured with a desktop pH meter. The pH is preferably about 5-9, more preferably about 5.8-8.6.
The transparency of the moisture under the sieve was visually examined and evaluated according to the following criteria.
◎: No floating matter is seen, and the water becomes transparent.
○: There are some floating substances, but the water is almost transparent.
△: There are some floating substances, and the water is slightly turbid
×: Suspended matter and turbidity in the water Excellent transparency corresponds to sedimentation of polluted suspended matter in the sewage.

The floc formation rate, floc size, pH of the tap water, and transparency of the tap water are summarized in Table 9 below together with the overall evaluation. The overall evaluation was obtained by comprehensively judging mainly the flocculation rate and the size of the flocs, and subordinately the transparency and pH of the tap water.

As shown in Table 9 above, the dehydration accelerators of Examples 1 to 10 containing natural anhydrite produced flocs in 120 seconds or less, and had excellent water transparency. From these results, it was confirmed that the performance of the dehydration accelerator was improved by blending natural anhydrite.

Claims (3)

A dehydration accelerator containing anhydrite,
The anhydrite is a natural anhydrite (produced in Thailand) having an average particle diameter D50 of 5 to 100 μm as determined from the wet particle size distribution ,
Of the peak intensities obtained by X-ray diffraction, the ratio (I _{( 020 )} /I _{( 102)} ) is 5 or more ,
As a result of dry particle size measurement using a sieve, less than 0.1% of particles do not pass through a sieve with an opening of 150 μm, and 98.7% or more of particles pass through a sieve with an opening of 90 μm. dehydration promoting material. 2. The dehydration accelerating material according to claim 1, wherein the ratio (I ₍₀₂₀₎ /I ₍₁₀₂₎ ) is 50 or less. 3. The dehydration accelerator according to claim 1, wherein 10 to 15 parts by mass of the polymer is blended with 100 parts by mass of the anhydrite.

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