JPH05293316A - Material for depositing fine particle in aqueous solution and depositing and recovering method - Google Patents

Abstract

PURPOSE:To deposit fine particles from an aq. soln. contg. the fine particles, to release the deposited fine particles with a release soln. and to concentrate and recover the released particles. CONSTITUTION:An aq. soln. contg. fine particles to be treated is passed through a bed packed with a depositing material obtained by holding the gelled precipitate of a metal hydroxide on the surface of a fibrous substrate to deposit the fine particles on the material. A release soln. is then passed through the packed bed to release, concentrate and recover the particles. The fibrous material such as a ferronickel refining slag fiber, iron manufacturing slag fiber, rook wool, glass fiber, ceramic fiber and org. synthetic fiber and the hydroxide of the alkaline-earth metal element, transition metal element, rare-earth metal, element, etc., are used to prepare the depositing material.

Description

Detailed Description of the Invention

[0001]

[Industrial application] In recent years, interest in the global environment has been increasing. Due to the protection of the water environment, effluent standards have become even more stringent, and it has become common knowledge in factories, etc. to adopt a closed system for industrial water through wastewater treatment.

Further, in the fields of semiconductor industry and pharmaceutical industry, needs for ultrapure water are increasing.

On the other hand, as seen in the popularization of household water purifiers, cleaner and tastier drinking water has been demanded.

Under these circumstances, more economical and sophisticated water treatment technology is desired.

The present invention is applicable not only to the field of environmental protection such as water and sewage treatment, marine pollution treatment, and wastewater treatment of industrial plants and industrial fields such as oil / water separation, solvent extraction and resource recycling, but also to the semiconductor industry, fine ceramics industry, Food industry,
In the industrial field dealing with functional ultrafine particles such as pharmaceutical industry and electronic industry, fine particle-containing aqueous solution, for example, liquid containing fine solid particles or fine liquid particles, and coexisting liquid of fine solid particles and fine liquid particles, especially containing extremely dilute fine particles Liquid
A method for adhering fine particles in an aqueous solution to the filling layer by flowing it through a layer filled with the adhering material according to claim 1 to clean water or the aqueous solution, and peeling the adhering fine particles from the filling layer. The present invention relates to a method for concentrating and recovering fine particles.

[0006]

2. Description of the Related Art Conventionally, in the treatment of a suspension of fine solid particles, a chemical such as a coagulant is added in a sedimentation tank or thickener to form relatively large secondary particles, that is, flocs, and then sedimentation or separation is performed. The so-called coagulation-sedimentation method or coagulation-floatation method for floating separation is generally used.

Flocculants are roughly classified into inorganic type and organic type.
The most common inorganic coagulants are iron sulfate and iron chloride iron salts, and the aluminum salt of sulfuric acid band and polyaluminum chloride, and the organic coagulants include anionic, cationic and nonionic coagulants. Polymers are often used.

Further, the liquid treated by the coagulation sedimentation method or the coagulation flotation method may be further sand-filtered.

On the other hand, there is also a method in which particles are directly filtered and separated by a filter having a sufficiently fine mesh such as a hollow fiber membrane or a ceramic membrane.

In the treatment of an emulsion of fine liquid particles (or fine oil droplets), that is, an emulsion liquid, first, a flocculating agent called an emulsion breaker is added to make the liquid particles hydrophobic, thereby aggregating, coalescing and coarsening. Then, after being made to float on the liquid surface by the difference in specific gravity or the introduction of bubbles, it is common to absorb with an organic compound adsorbent having interfacial hydrophobicity.

Further, the emulsion is first passed through a packed bed of fibrous material to promote coalescence and coarsening of emulsion particles, and then either floated in a separation tank or made of a hydrophobic material such as polypropylene. There is also a method of adsorbing oil components with an organic synthetic fiber packed bed.

However, there has been no technique for simultaneously depositing and separating fine solid particles and fine liquid particles from a liquid in which diluted fine particles and fine liquid particles coexist.

[0013]

However, in the conventional coagulation-sedimentation method or coagulation flotation method, it is necessary to add an excessive coagulant during the treatment of the suspension of solid particles, so that the treatment liquid and the particles are aggregated. There is a problem of being contaminated by the agent.

In particular, in the case of a suspension of dilute and fine particles, the flocculation rate is extremely slow, so that the effective cross-sectional area of the sedimentation tank or thickener is remarkably increased, or the precipitation rate is increased in order to accelerate the flocculation rate. It is necessary to circulate a part of it and to add an aggregating aid such as bentonite or kaolin, which not only increases the processing cost but also makes it difficult to perform advanced processing.

In the direct filtration method, since the particles are fine and the filtration resistance is large, it is unavoidable to use a filter aid, a pressure filtration method or a vacuum filtration method, and often cause clogging to cause frequent reverse filtration. Since it requires washing, the concentration ratio of particles in the backwash solution is low, and there are drawbacks such as the necessity of reprocessing a large amount of backwash solution, and the processing cost is often high.

Similarly, when treating an emulsion of dilute fine liquid particles, it is unavoidable that the treatment liquid is contaminated by the addition of a coagulant.

Further, since the coagulant and the organic compound adsorbent are relatively expensive, the processing cost is high.

In particular, for the advanced treatment of a liquid containing extremely dilute fine particles, the treatment has been extremely difficult with the prior art.

In order to solve the above-mentioned problems of the prior art, the present invention provides a simple, highly efficient and low cost processing method.

[0020]

The present invention provides (1) an adhering material for fine particles in an aqueous solution, characterized in that a metal hydroxide is held on the surface of a base material of a fibrous material,

(2) The fine particles are adhered to the adhesive material by forming the adhesive material according to (1) into a packed layer and allowing an aqueous solution containing fine particles to be treated to flow through the packed layer. A method of attaching fine particles in an aqueous solution to

(3) The packed bed to which the fine particles have been attached by the method described in (2) is impregnated with a solution of an aqueous solution of an acid, an alkali or a chelate compound as a stripping solution, and allowed to flow through and held on the fiber surface. A method for recovering fine particles in an aqueous solution, characterized in that the adhered particles are separated from the packed bed and recovered by dissolving the metal hydroxide.

The present invention will be described in detail below along with the operation.

Usually, fine suspended particles in muddy water are
The surface thereof is positively or negatively charged by adsorption of H or a specific component, but in a neutral region, it generally has a negative potential and repels each other to maintain a stable dispersion system in many cases.

In the prior art using an inorganic flocculant, a coagulant containing a polyvalent heavy metal cation such as an iron salt or an aluminum salt is added thereto to lower the surface potential of the particles, whereby the particles coagulate with each other. In addition, a large floc is formed by the cross-linking action of the hydrolysis product of the heavy metal cation,
It will settle easily.

Hydrolysis products of heavy metal cations (eg
Al³⁺In the case of, Al (OH )²⁺・ (H₂O)_Five, Al (O
H)⁺ ₂・ (H₂O)_Four, Al (OH)₃・ (H₂O)₃Na
Etc. generally have a positive potential and the polymer is crosslinked.
It is considered to have an action.

In order to solve the problems of the prior art, the inventors of the present invention have hitherto disclosed in Japanese Patent Application No. 3-276273, SiO ₂
And MgO, CaO, Al ₂ O ₃ , FeO, TiO ₂ , M
One or two of nO, Cr ₂ O ₃ , Na ₂ O and K ₂ O
The present invention has invented a method for treating an aqueous solution containing fine particles, in which a packed bed filled with fibers or granules containing at least one kind of the above as a main ingredient is applied.

Like the suspended particles, the adhering material has its surface charged positively or negatively depending on the pH of the treatment liquid and the like.

Then, when treating the aqueous solution containing fine particles, if the pH of the treatment liquid is adjusted so that the particle surface and the surface of the adhering material have potentials having opposite signs, and the solution is passed through the packed bed,
Electric attraction between suspended particles and adherent and van der
Suspended particles can be attached to the surface of the adhering material and water or an aqueous solution can be cleaned by the cohesive force of the waals attraction.

However, in this packed bed flow-through treatment method, it is necessary to greatly adjust the pH of the treatment liquid depending on the treatment object.
There was a limit that the adhesion volume of suspended particles was small.

Therefore, in order to overcome the above-mentioned limitations of the packed bed liquid-flowing treatment method, the present inventors have focused on the characteristics of metal hydroxides having a positive surface potential and a crosslinking action. The invention relating to a method for treating fine particles in an aqueous solution using a fiber having a gel precipitate of hydroxide on its surface as an adhering material has been completed.

That is, a gel-like precipitate of metal hydroxide is produced by a hydrolysis reaction, the precipitate is retained on the surface of the fiber, and the thus-prepared material is used as an adhering material for fine particles in an aqueous solution.

By using the above-mentioned adhesive material as a packed bed and passing the aqueous solution containing fine particles to be treated through the packed bed,
Fine particles in an aqueous solution are attached to an adhesive material to clean water or an aqueous solution.

Then, a solution of an acid, an alkali or a chelate compound is impregnated into the adhering material or the packed bed to which the fine particles are adhered and allowed to flow through to dissolve the gelled precipitate of the metal hydroxide to thereby remove the adhered particles. The fiber is reused for the preparation of the adhering material while being concentrated and recovered in the solution.

Here, as the metal element of the metal hydroxide, an alkaline earth metal element, a transition metal element, a rare earth metal element or the like can be used.

Specific examples include magnesium, iron, aluminum, zinc, copper, cerium, etc., but it is desirable to use a metal element that has a low solubility in a treatment aqueous solution, is inexpensive, and has low toxicity.

Therefore, the pH range is the second at pH 4 to 10.
Iron, aluminum at pH 5 to 8 and magnesium at pH 10 or higher are preferable.

As the salt of the metal element used for producing the metal hydroxide, a sulfate, a chloride, a nitrate, a phosphate, a fatty acid salt, or a double salt thereof can be used.

Further, in the case of iron, aluminum, etc.,
Polychlorides and polysulfates are preferred.

The fibrous substance used as the base material may be chemically stable with respect to the treatment aqueous solution. For example, rock wool, slag wool, glass fibers, inorganic fibers such as various ceramic fibers, steel wool, stainless fibers, etc. Such as metal fibers, polyamino fibers, polyurethane fibers, polypropylene, polyester and other organic synthetic fibers,
Natural fibers such as cotton and asbestos, as well as cellulose and fibrous activated carbon can be used.

However, in view of the chemical resistance, hydrophilicity, price, etc. of the fiber, it can be said that the inorganic fiber is a more desirable material for the present invention. The diameter of the fiber is 0.5
The range of up to 100 μm is desirable.

There are various possible methods for preparing the adhesive material,
Two methods are described here as methods that can be easily prepared.

One is to dissolve a predetermined amount of metal salt to be used in a volume of water which is four times or more the volume of a predetermined amount of fiber to be used,
The fiber is impregnated with the solution by adding a predetermined amount of the fiber used in the solution.

Then, an alkali solution is added to a pH at which the metal ions are completely hydrolyzed, and excess liquid other than the fiber impregnating liquid is separated and removed to obtain an adhesive material.

The other is that a predetermined amount of fibers is first packed in a packed bed at a specified packing density, and the volume of each packed bed is 0.
An adhesive material characterized in that a gel-like precipitate of metal hydroxide is retained on the surface of the fiber by alternately impregnating a small amount of a metal salt solution having a volume of 5 times or more and an alkaline solution little by little and letting it flow through. This is the method of preparation.

Here, as the alkali, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammonium hydroxide or the like can be used.

The acid of the stripping solution used for stripping the particles adhered from the packed bed according to the present invention is sulfuric acid, hydrochloric acid,
As the chelate compound such as nitric acid and hydrofluoric acid, sodium citrate, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid and the like can be used.

The optimum packing density of the packed bed packed with the adhesive material according to the present invention is determined by the kind of the fiber used and the property of the aqueous solution to be treated, but in general, the packing density as a fiber is 50 to 500 g / dm ^3. Is preferable, and
The packing density as a metal hydroxide is 10 to 15 as a metal.
A range of 0 mMol / dm ³ is preferred. In addition, the thickness of the filling layer is preferably in the range of 2 to 100 cm.

The adhesive material according to the present invention can use a granular substance as a base material for holding the metal hydroxide in addition to the fibrous substance.

However, when a fibrous substance is used, the packing density of the packed bed can be lowered to reduce the filtration resistance of the packed bed, the contact area between the adhering material and the treatment liquid can be remarkably increased, and the adhesion of particles. It is clear that fibrous materials are preferred substrates over particulate materials, due to their advantages such as large capacity and low risk of metal hydroxide erosion from the packed bed.

In the present invention, the fine particles have a diameter of 10 μm.
The following fine solid particles or fine liquid particles (or fine oil droplets) are referred to, and the fine particle-containing aqueous solution is a suspension of fine solid particles, or an emulsion of fine liquid particles and the suspension and emulsion. An aqueous solution containing both at the same time.

In the present invention, the fine particles are attached to and separated from the adhering material by passing the fine particle-containing aqueous solution to be treated through the packed bed. The flow-through method may be a downward flow, an upward flow or a side flow. Either may be used, and in general, an upward flow is preferable in the case of an aqueous solution containing solid fine particles, and a downward flow is preferable in the case of an aqueous solution containing liquid particles.

The present invention relates to an adhering material for fine particles in an aqueous solution and a method for adhering and collecting the fine particles. Depending on the adhering material and the adhering method, some of the dissolved components in the aqueous solution, for example, harmful metals such as cadmium, arsenic and mercury. It is also possible to adsorb ions or polymer flocculants.

Further, by combining the packed bed according to the present invention with the packed bed of activated carbon or zeolite, fine particles and dissolved components in the aqueous solution can be completely removed and separated at the same time, and the service life of the packed bed of activated carbon or the packed bed of zeolite can be improved. It can be extended significantly.

The greatest feature of the present invention is that, as will be shown in the examples below, ultrafine solid particles of up to 0.009 μm and oil emulsion particles can be directly attached and separated, and only 10
A relatively large flow velocity of 1 to 7 m / H can be obtained at a low flow pressure of 200 mmH ₂ O.

A specific example of the processing method according to the present invention will be described below.

[0057]

[Example 1] The main components of airborne solid fine particles (generally referred to as SS) contained in industrial wastewater or river water are generally
In many cases, Fe ₂ O ₃ , SiO ₂ , Al ₂ O _{3 and the} like are used.

Here, 5 L of each suspension of various ultrafine solid particles shown in Table 1 was prepared to be treated raw water.

Slag fibers mainly made of iron blast furnace slag were used as a base material for the adhesive material. The main components of the slag fiber are SiO ₂ : 48.10 wt%, MgO: 8.42 wt.
%, CaO: 31.07 wt%, Al ₂ O ₃ : 16.05
wt%, total Mn: 0.24 wt%, total Fe: 1.78w
t%, S: 1.0 wt%, and the average fiber diameter is 4 μm.

Ferric hydroxide was used as the metal hydroxide of the adhering material. The preparation of the adhesive material and the packed layer is carried out by first dissolving ferric sulfate in water with a beaker, adding the above slag fiber to the solution to impregnate the solution, and then ferric iron is completely hydrolyzed. A 1N sodium hydroxide solution was added to pH 8 with stirring.

The adhesive material prepared in this manner was used to prepare an inner diameter of 70 m.
It was packed in an acrylic column having a height of m and a height of 1 m.

A 12-mesh support screen and a cock are attached to the bottom of the column. The column was used also in Examples 2, 3 and 4 described later.

The treated raw water was sequentially passed through the packed bed. The packed bed conditions and the flow-through conditions here are summarized as follows.

Test conditions: Thickness of packed layer: 50 mm Packing density: 270 g / dm as slag fiber³  100 mMol / dm as ferric iron³ Overflow pressure: 70 mmH₂O 2 flow rate: 8 cm / min.

Each treated water was collected and analyzed, and the analysis results are shown in Table 1.

As shown in Table 1, polluted water or an aqueous solution containing fine solid particles, that is, a suspension of fine solid particles, can be easily and highly treated by the method of the present invention.

Then, 400 ml of 0.5N hydrochloric acid (twice the volume of the packed bed) was added to the packed bed to which the fine solid particles were attached at 2 cm / min. When it was passed through at a rate of, the ferric hydroxide of the adhering material was dissolved, and the adhering particles were separated from the packed bed.

The particles thus adhered can be concentrated and recovered, and the fiber as the base material of the adhering material can be reused for the preparation of the adhering material.

However, since the slag fiber has a high basicity, the pH of the treated water tends to be higher than that of the raw water,
Further, since the sulfur content is relatively high, hydrogen sulfide was generated when the stripping operation was performed with hydrochloric acid.

[0070]

[Table 1]

[0071]

[Example 2] The activated sludge method, which is the most general treatment method for wastewater containing organic pollutants such as domestic sewage, is a fine activated sludge called bulking phenomenon depending on the treatment conditions such as water temperature in the final sedimentation tank after aeration treatment. There is a problem that the water quality of the discharged water deteriorates due to the floating phenomenon.

Here, the discharged water after the final treatment at a certain urban sewage treatment plant was used as the treated raw water.

The main components of slag fiber (manufactured by Taiheiyo Metal Co., Ltd.) produced by preparing ferronickel smelting slag as components are SiO ₂ 52.8 wt%, MgO 26.6 wt%,
Al ₂ O ₃ 13.6 wt%, CaO 0.5 wt%, total Fe 2.4 wt%, total Cr 0.5 wt%, S 0.0
At 4 wt%, the average fiber diameter is 4 μm.

The ferronickel slag fiber was used in Example 1.
Compared to the blast furnace slag fiber described in 1, the basicity is close to neutral,
Further, since the sulfur content is very small, it is chemically stable and is excellent as a base material for the adhesive material.

Here, an adhesive and a filling layer were prepared in the same manner as in Example 1 using the ferronickel slag fiber and polyaluminum chloride. The test conditions for packed bed conditions and flow-through conditions are as follows.

Test conditions: Thickness of filling layer: 200 mm Filling density: 180 g / dm as slag fiber³  150 mMol / dm as aluminum³ Overflow pressure: 200 mmH₂O 2 flow rate: 11 cm / min.

Under the above conditions, 100 L of the treated raw water was passed through the filling tank, the treated water was sampled in 20 L fractions, and the water quality was analyzed. The analysis results are shown in Table 2.

As shown in Table 2, the quality of the treated water was not only the SS decreased to 1/10 of the raw water but also the BO quality.
D and E. coli were reduced to less than half each.

As described above, the quality of the discharged water of the municipal sewage can be greatly improved by the treatment method of the present invention.

Next, in order to separate the adhered suspended solids from the packed bed, 1.5 L of 0.5N sulfuric acid (twice the volume of the packed bed) was applied to the packed bed at 2 cm / min. When it was made to flow through at a flow rate of, the aluminum hydroxide of the adhering material was dissolved and the adhering particles were separated from the packed bed.

In this case, hydrogen sulfide was scarcely generated during the peeling operation.

[0082]

[Table 2]

[0083]

Example 3 Emulsified oil-containing wastewater is extremely difficult to treat by the conventional techniques. Here, an emulsion of kerosene, B-heavy oil, and salad oil, which are often found in industrial wastewater or domestic wastewater, was treated raw water.

The emulsion was prepared by adding 1000 PPM of oil.
In the water contained, straight chain sodium dodecylbenzene sulfonate (S
DBS) is added as an emulsifier at 50 PPM, and 15,000
Strongly stir under the conditions of rpm and 30 seconds to form a stable and fine emulsion for a long time. 2 L of each oil emulsion thus prepared was used as treated raw water.

Here, an adhesive and a filling layer were prepared in the same manner as in Example 1 using glass fibers having an average diameter of 10 μm and aluminum sulfate. The test conditions of packed bed condition and flow-through condition are as follows.

Test conditions: Thickness of filling layer: 100 mm Filling density: 300 g / dm as glass fiber³  150 mMol / dm as aluminum³ Overflow pressure: 200 mmH₂O 2 flow rate: 3 cm / min.

Table 3 shows the residual oil concentration and pH of the treated water obtained by sequentially passing the various emulsions through the packed bed.

As described above, in any of the emulsions, the residual oil concentration in the treated water was as low as 10 PPM or less.

Then, in order to separate the adhered oil emulsion particles from the packed bed, 0.8 L of 1N sodium hydroxide was added.
(2 times the volume of the packed bed) to the packed bed at 2 cm / min. When it was passed through at a flow rate of, the aluminum hydroxide of the adhering material was dissolved and the adhered oil was separated from the packed bed.

[0090]

[Table 3]

[0091]

[Example 4] An alkaline degreasing liquid is generally used as a cleaning agent for surface oils and fats of semiconductors and metals. The oil degreased by cleaning gradually accumulates as emulsified particles in the degreasing liquid, resulting in a concentration of oil accumulation. When the above progresses, the degreasing liquid loses its degreasing ability.

Here, a test was conducted for the purpose of removing the rolling oil and suspended solid fine particles and regenerating the alkaline degreasing liquid, using the strong alkaline degreasing waste liquid containing the actual rolling oil as the processing stock solution.

Here, ceramic fiber was used as the base material of the adhesive material. The main components of the ceramic fiber are SiO ₂ 53.2 wt% and Al ₂ O ₃ 46.2w.
At t%, the fiber diameter is 2.8 μm. Magnesium hydroxide was used as the metal hydroxide of the adhering material.

For the preparation of the adhesive and the packed bed, 60 g of the ceramic fiber was uniformly packed in the column described in Example 1 to a height of 70 mm.

Next, 120 mMol /
125 mL of L magnesium chloride solution and 250 mMo
Alternately, 125 mL of 1 / L sodium hydroxide solution was impregnated into the ceramic fiber layers, 10 mL each. The test results of the packed bed conditions and the flow-through conditions thus prepared are shown below.

Test conditions: Thickness of packed bed: 70 mm Packing density: 223 g / dm as ceramic fiber
³  60 mMol / dm as magnesium³ Overflow pressure: 100 mmH₂O 2 flow rate: 5 cm / min.

10 L of the strong alkaline degreasing waste liquid was passed through the packed bed. As shown in Table 4 of the treatment results, it was possible to regenerate the strong alkaline degreasing waste liquid by effectively removing the rolling oil and fine solid particles from the strong alkaline degreasing waste liquid by the adhesive material and the packed layer thereof.

Then, in order to separate the adhered oil emulsion particles from the packed bed, 0.6 L of 0.5N nitric acid (twice the volume of the packed bed) was applied to the packed bed at 2 cm / min. When it was passed through at a flow rate of 1, the magnesium hydroxide of the adhering material was dissolved and the adhering rolling oil and fine solid particles were separated from the packed bed.

In addition, in order to compare the above-mentioned treatment results with the case where the metal hydroxide (magnesium hydroxide in this case) is not retained and the treatment is performed with a packed bed of only fibers, magnesium hydroxide is not retained. The strong alkaline degreasing waste liquid was treated under the same conditions as the above test conditions, and the treatment results are also shown in Table 4. As can be seen from Table 4, in the case of a packed layer containing only ceramic fibers without retaining magnesium hydroxide, the rolling oil concentration in the treatment liquid could not be significantly reduced.

As described above, it is clear that holding the metal hydroxide on the fiber base material has a great effect.

[0101]

[Table 4]

[0102]

According to the present invention, a suspension of fine solid particles or an emulsion of fine liquid particles or an aqueous solution containing both fine solid particles and fine liquid particles at the same time, that is, fine particles in the aqueous solution In the treatment of the aqueous solution for the purpose of removing or concentrating and separating, the aqueous solution is simply passed through the layer filled with the adhering material according to claim 1, and the fine particles in the aqueous solution are very few PPM to PPM. Can be reduced to very low concentration levels.

Further, the fine particles are peeled from the packed bed only by passing the peeling solution through the packed bed to which the fine particles are attached.
While being concentrated and recovered, the fiber that is the base material of the adhesive material can be reused for the preparation of the adhesive material.

In particular, the treatment method of the present invention is extremely effective in the advanced treatment of an aqueous solution in which solid particles and liquid particles, which are extremely dilute and extremely fine, coexist, while the conventional techniques are very difficult. It is possible with a single treatment according to the invention to pass the difficult drainage standards. As described above, the processing method of the present invention is characterized by being simple and having high processing efficiency.

Claims (3)

[Claims] 1. A material for adhering fine particles in an aqueous solution, characterized in that a metal hydroxide is held on the surface of a fibrous base material. 2. A filling layer comprising the adhesive material according to claim 1,
A method for adhering fine particles in an aqueous solution, which comprises adhering the fine particles to an adhering material by causing an aqueous solution containing fine particles to be treated to flow through the packed bed. 3. The filling layer to which the fine particles are attached by the method according to claim 2, is impregnated with a solution containing an aqueous solution of an acid or an alkali or a chelate compound as a stripping solution and allowed to flow through to be retained on the surface of the fiber. By dissolving the metal hydroxide
A method for recovering fine particles in an aqueous solution, characterized in that the adhered particles are separated from the packed bed and recovered.