Flocculant and water treatment method

Abstract

Provided is a novel flocculant having exceptional cohesiveness.　The present technology provides a flocculant containing a pseudo-crosslinked body obtained by physical interaction with a linear water-soluble polymer. Because the pseudo-crosslinked body used in the present technology does not require time or energy as in a chemical reaction such as oxidation polymerization or chemical crosslinking, the pseudo-crosslinked body has high producibility as well as a high environmental-load-reducing effect such as recyclability. In the flocculant according to the present technology, the physical interaction may be at least one action selected from intermolecular interaction and surfactant action, and the linear water-soluble polymer may have an annular structure in the main chain.

Description

Flocculant and water treatment method

[0001] The present technology relates to a flocculant, and more particularly to a flocculant using a polymer that has been subjected to a special modification treatment, and a water treatment method using the flocculant.

[0002] Flocculants are used in a variety of fields, including wastewater treatment, water supply and sewerage, the fermentation industry, the paper industry, civil engineering, mining, and semiconductor and circuit board manufacturing. For example, flocculants are used to purify water by flocculating and separating fine particles suspended and dispersed in water, such as factory wastewater. Furthermore, in recent years, efforts have been made to prevent environmental destruction, improve safety, prevent the depletion of fossil resources, and realize a sustainable society, with the aim of developing safe, biodegradable flocculants. For example, Patent Document 1 discloses a technology that uses at least one of molokheiya (Coleoptera olivaceus), its dried product, and its extract as a flocculant, which, compared to conventional flocculants, has superior flocculation properties, a superior deodorizing effect for treated liquids, is safe for humans and the environment, and can contribute significantly to global environmental conservation in terms of resource conservation, reduction of hazardous substances, and effective waste utilization.

[0003] Furthermore, Patent Document 2 discloses a technology that can economically purify the water of a relatively large area such as a swamp or reservoir with a small consumption of coagulant, by disposing a coagulant mixer on the water surface that mixes a biodegradable coagulant mainly composed of cross-linked polyglutamic acid into a water flow, and a preliminary coagulation device that agitates and mixes the water flow containing the coagulant from the coagulant mixer to form coagulates, and introducing the water flow containing the coagulates flowing out of the preliminary coagulation device into a hose with nozzle holes drilled at appropriate intervals, and spraying the water flow containing the coagulates through the hose near the water surface in a purification treatment area.

[0004] Japanese Patent Laid-Open No. 11-114313 Japanese Patent Laid-Open No. 2006-142183

[0005] As mentioned above, various technological developments are underway regarding flocculants that can be used in a variety of fields, and many environmentally friendly initiatives are also being developed, but there is also a need for further development.

[0006] Therefore, the main object of the present technology is to provide a novel flocculant with excellent flocculation properties.

[0007] That is, the present technology first provides a flocculant containing a pseudo-crosslinked product formed by subjecting a linear water-soluble polymer to physical interaction. In the flocculant according to the present technology, the physical interaction may be at least one action selected from intermolecular interaction and surfactant action, and the linear water-soluble polymer may have a cyclic structure in its main chain. In the flocculant according to the present technology, the pseudo-crosslinking due to intermolecular interaction may be pseudo-crosslinking performed using a branched water-soluble polymer. In the flocculant according to the present technology, the pseudo-crosslinking due to surfactant action may be pseudo-crosslinking performed using a reducing agent. In the flocculant according to the present technology, the cyclic structure of the linear water-soluble polymer may be an alicyclic structure. In the flocculant according to the present technology, the linear water-soluble polymer may be a plant-derived linear water-soluble polymer. In this case, the plant-derived linear water-soluble polymer may be a plant-derived water-soluble polysaccharide. The plant-derived water-soluble polysaccharide may be a water-soluble polysaccharide contained in a plant. The plant may be one or more plants selected from mulukhiyah, okra, jute, matsuna, mitsuba, mizuna, spinach, banana, nameko mushroom, yam, okra, and mekabu. In the flocculant according to the present technology, the branched water-soluble polymer may have a cyclic structure in its main chain. In this case, the cyclic structure of the branched water-soluble polymer may be an alicyclic structure. The branched water-soluble polymer may be a thickening polysaccharide. The thickening polysaccharide may be one or more thickening polysaccharides selected from inulin, galactomannan, and glucan. In the flocculant according to the present technology, the reducing agent may be one or more reducing agents selected from hydrogen peroxide, ozone, oxalic acid, oxalates, lithium aluminum hydride, hydrazine, and formic acid.

[0008] Next, the present technology provides a water treatment method that includes a step of adsorbing and precipitating the target substance with a flocculant containing a pseudo-crosslinked body formed by subjecting a linear water-soluble polymer to physical interaction.

[0009] A preferred embodiment for implementing the present technology will be described below. The embodiment described below shows an example of a typical embodiment of the present technology, and the scope of the present technology is not narrowly interpreted as being narrowed by this, and each embodiment can be freely combined. The description will be given in the following order: 1. Flocculant (1) Linear water-soluble polymer (2) Pseudo-crosslinked polymer (3) Branched water-soluble polymer (4) Reducing agent (5) Other components (6) Usage form 2. Water treatment method (1) External modification step (2) Flocculant solution and / or dispersion preparation step (3) Adsorption / sedimentation step (4) Separation step

[0010] 1. Flocculant (1) Linear-Chain Water-Soluble Polymer As the linear-chain water-soluble polymer that can be used as a raw material for the flocculant of the present technology, one or more general linear-chain water-soluble polymers can be freely selected and used as long as the action and effect of the present technology are not impaired. The linear-chain water-soluble polymer may be, for example, a linear-chain water-soluble polymer that does not have a cyclic structure in the main chain, such as linear polyacrylamide, a partial hydrolyzate of linear polyacrylamide, or vinyl alcohol. However, in the present technology, it is more preferable to use a linear-chain water-soluble polymer having a cyclic structure. The cyclic structure may be an aromatic ring, but in the present technology, an alicyclic structure is preferred. This is because linear-chain water-soluble polymers having an alicyclic structure are often more biodegradable than linear-chain water-soluble polymers having an aromatic ring, which can contribute to reducing environmental impact.

[0011] As the linear water-soluble polymer having an alicyclic structure, a linear water-soluble polymer derived from a plant can be used. Examples of the linear water-soluble polymer derived from a plant include water-soluble polysaccharides derived from a plant (carrageenan, pectin, etc.). Examples of plants containing water-soluble polysaccharides that can be used in the present technology include mulukhiyah, okra, jute, jute, okra, mekabu, matsuna, mitsuba, mizuna, spinach, banana, nameko mushroom, and yam.

[0012] Although water-soluble polysaccharides can be extracted from these plants and further purified as necessary before use, in the present technology, as shown in the examples described below, these plants can also be used in the form of a paste, or can be used as is after drying, pulverization, etc. In other words, in the present technology, plants containing water-soluble polysaccharides can be used as is, eliminating the need for devices and processes for extraction and purification, and contributing to reductions in cost, time, and energy.

[0013] The linear water-soluble polymer may be externally modified. In the present technology, external modification refers to changes such as cleavage or scission in a part of the polymer structure caused by physical modification, thermal modification, photomodification, etc. As shown in the examples described below, polymers that have been externally modified generally have a reduced molecular weight and often exhibit reduced flocculation performance. However, in the present technology, by subjecting the linear water-soluble polymer to physical interaction to form a pseudo-crosslinked body, it is possible to prevent the reduction in flocculation performance even in the case of an externally modified linear water-soluble polymer. In addition, by using an externally modified linear water-soluble polymer, the dissolution rate of the flocculant using this polymer is improved, and therefore immediate effect can be expected.

[0014] External modification can also be performed on raw materials containing a linear water-soluble polymer. For example, as described above, when using plants containing a linear water-soluble polymer, the effects of the present technology can be fully achieved even if the plants themselves are externally modified. Discarded plants and decayed plants can also be plants in a state where external modification has progressed, and such discarded plants and decayed plants can also be used as raw materials containing a linear water-soluble polymer that has been externally modified. Using discarded plants and decayed plants can also contribute to the realization of a sustainable society.

[0015] The timing of external modification of the linear water-soluble polymer is not particularly limited. For example, as described below, when the flocculant is used in a solution and / or dispersion state, the external modification may be performed either before or after the linear water-soluble polymer is introduced into the solvent. In this technology, it is preferable to externally modify the linear water-soluble polymer before introducing the linear water-soluble polymer into the solvent.

[0016] The content of the linear water-soluble polymer in the flocculant can be freely set depending on the type and amount of the target substance to be flocculated, as long as it does not impair the action and effect of the present technology. When the flocculant is used in a solution and / or dispersion state, the lower limit of the content of the linear water-soluble polymer in the flocculant solution and / or flocculant dispersion is, for example, 0.01 wt% or more, preferably 0.03 wt% or more, and more preferably 0.05 wt% or more. The upper limit of the content of the linear water-soluble polymer in the flocculant solution and / or flocculant dispersion is, for example, 10 wt% or less, preferably 5.0 wt% or less, more preferably 3.0 wt% or less, and even more preferably 1.0 wt% or less. By setting the content of the linear water-soluble polymer in the flocculant solution and / or flocculant dispersion within this range, sufficient flocculation performance can be exhibited.

[0017] (2) Pseudo-crosslinked polymer The flocculant according to the present technology is characterized by containing a pseudo-crosslinked polymer formed by physical interaction with a linear water-soluble polymer. The pseudo-crosslinked polymer used in the present technology is not a crosslinked polymer formed by a chemical reaction, but a crosslinked polymer formed by physical interaction. In other words, the pseudo-crosslinked polymer used in the present technology is a different concept from compounds polymerized by chemical reactions, such as chemical crosslinked polymers, ionic crosslinked polymers, and crosslinked polymers formed by hydrogen bonding. Therefore, the pseudo-crosslinked polymer used in the present technology does not require time or energy, as in chemical reactions such as oxidative polymerization or chemical crosslinking, and therefore has high productivity and is highly effective in reducing environmental impact, such as recyclability.

[0018] It should be noted that this technology does not intend to completely eliminate crosslinking by chemical reaction, and as long as pseudo-crosslinking by subjecting a linear water-soluble polymer to physical interaction is used in some parts, crosslinking by chemical reaction may be used in combination as long as it does not impair the action and effect of this technology. Furthermore, in addition to pseudo-crosslinking formed by subjecting a linear water-soluble polymer to physical interaction, the flocculant of this technology may also contain compounds polymerized by chemical reaction, such as chemical crosslinkers such as oxidized polymers, ionic crosslinkers, and crosslinkers by hydrogen bonding, as long as it does not impair the action and effect of this technology.

[0019] The physical interaction used in the pseudo-crosslinked body is not particularly limited as long as it is a physical interaction, and one or more physical interactions that can pseudo-crosslink a polymer can be freely selected and used. In the present technology, examples of physical interactions that pseudo-crosslink a linear water-soluble polymer include intermolecular interactions and surfactant effects, and these can also be used in combination.

[0020] (3) Branched Water-Soluble Polymers As a method for pseudo-crosslinking a linear water-soluble polymer by intermolecular interactions, pseudo-crosslinking using another polymer can be mentioned. Specifically, this method involves entanglement of the polymer chains of the linear water-soluble polymer and the other polymer to form pseudo-crosslinks. The other polymer to be pseudo-crosslinked with the linear water-soluble polymer is not particularly limited as long as it is a polymer capable of pseudo-crosslinking, but a branched water-soluble polymer is preferred. Compared to the pseudo-crosslinking between linear polymers, the pseudo-crosslinking between a linear polymer and a branched polymer is higher, which in turn can improve the flocculating effect of the flocculant.

[0021] The branched water-soluble polymer may be a branched water-soluble polymer without a cyclic structure, such as branched polyvinyl alcohol or branched polyacrylamide, but in the present technology, it is preferable to use a branched water-soluble polymer with a cyclic structure. The cyclic structure may be an aromatic ring, but in the present technology, it is preferable to use an alicyclic structure. This is because branched water-soluble polymers with an alicyclic structure often have higher degradability than branched water-soluble polymers with an aromatic ring, and can therefore contribute to reducing environmental load.

[0022] As the branched water-soluble polymer having an alicyclic structure, a plant-derived branched water-soluble polymer can be used, and examples of the plant-derived branched water-soluble polymer include thickening polysaccharides. As the thickening polysaccharide that can be used in the present technology, one or more general thickening polysaccharides can be freely selected and used as long as the action and effect of the present technology are not impaired. Examples of thickening polysaccharides include inulin, galactomannan (guar gum, tara gum, locust bean gum, etc.), glucan (dextrin, glycogen, amylopectin, etc.), etc.

[0023] Examples of plants containing thickening polysaccharides that can be used in the present technology include guar bean, molokheiya, jute, Suizenji mustard greens, banana, jute, mizuna, matsuna, spinach, apple, jute, carrot, citrus, grapefruit, pumpkin, chrysanthemum, shiso leaf, bok choy, butterbur, Chinese cabbage, cabbage, mimosa, cod, sunflower, mango, aloe, okra, and mekabu.

[0024] The content of the branched water-soluble polymer in the flocculant can be freely set depending on the type and amount of the target substance to be flocculated, as long as it does not impair the action and effect of the present technology. When the flocculant is used in a solution and / or dispersion state, the lower limit of the content of the branched water-soluble polymer in the flocculant solution and / or flocculant dispersion is, for example, 0.01 wt% or more, preferably 0.03 wt% or more, and more preferably 0.05 wt% or more. The upper limit of the content of the branched water-soluble polymer in the flocculant solution and / or flocculant dispersion is, for example, 10 wt% or less, preferably 5.0 wt% or less, more preferably 3.0 wt% or less, and even more preferably 1.0 wt% or less. By setting the content of the branched water-soluble polymer in the flocculant solution and / or flocculant dispersion within this range, sufficient flocculation performance can be exhibited.

[0025] Furthermore, the ratio of the linear water-soluble polymer to the branched water-soluble polymer in the flocculant can be freely set depending on the type of linear water-soluble polymer or branched water-soluble polymer used. The ratio of the branched water-soluble polymer to the linear water-soluble polymer 1 is, for example, 0.5 or more, preferably 0.7 or more, and more preferably 0.8 or more. The ratio of the branched water-soluble polymer to the linear water-soluble polymer 1 is, for example, 1.5 or less, preferably 1.3 or less, and more preferably 1.2 or less. By setting the ratio of the linear water-soluble polymer to the branched water-soluble polymer in the flocculant within this range, pseudo-crosslinking between the linear water-soluble polymer and the branched water-soluble polymer can be sufficiently progressed, thereby improving the flocculation performance.

[0026] (4) Reducing Agent As a method for pseudo-crosslinking a linear water-soluble polymer by surfactant action, for example, a method for pseudo-crosslinking by interacting the linear water-soluble polymer with bubbles (foam) can be mentioned. Bubbles can be generated physically in the flocculant solution and / or flocculant dispersion, for example, but in this technology, it is preferable to generate bubbles using a reducing agent.

[0027] The reducing agent that can be used in the flocculant of the present technology can be one or more commonly used reducing agents that can be freely selected and used as long as the action and effect of the present technology are not impaired. Examples of reducing agents include hydrogen peroxide, ozone, oxalic acid, oxalates, lithium aluminum hydride, hydrazine, and formic acid.

[0028] The content of the reducing agent in the flocculant can be freely set depending on the type and amount of the target substance to be flocculated, as long as it does not impair the action and effect of the present technology. When the flocculant is used in a solution and / or dispersion state, the lower limit of the content of the reducing agent in the flocculant solution and / or flocculant dispersion is, for example, 0.01 wt% or more, preferably 0.03 wt% or more, more preferably 0.05 wt% or more, and even more preferably 0.1 wt% or more. The upper limit of the content of the reducing agent in the flocculant solution and / or flocculant dispersion is, for example, 10 wt% or less, preferably 5.0 wt% or less, and more preferably 3.0 wt% or less. By setting the content of the reducing agent in the flocculant solution and / or flocculant dispersion within this range, sufficient flocculation performance can be exhibited.

[0029] Furthermore, the ratio of the linear water-soluble polymer to the reducing agent in the flocculant can be freely set depending on the type of linear water-soluble polymer and reducing agent used. The ratio of the reducing agent to the linear water-soluble polymer 1 is, for example, 0.5 or more, preferably 0.7 or more, more preferably 0.8 or more, and even more preferably 1.0 or more. The ratio of the reducing agent to the linear water-soluble polymer 1 is, for example, 5.0 or less, preferably 4.0 or less, and more preferably 3.0 or less. By setting the ratio of the linear water-soluble polymer to the reducing agent in the flocculant within this range, pseudo-crosslinking due to the surfactant action of the linear water-soluble polymer can be sufficiently promoted, thereby improving the flocculation performance.

[0030] (5) Other Components The flocculant according to the present technology can be used in combination with other components as long as the action and effect of the present technology are not impaired. Examples of other components that can be used include excipients, pH adjusters, disintegrants, stabilizers, enzymes, and other components that are commonly used in formulations. Other components with flocculating effects can also be used in combination. Furthermore, components with known or future functions can also be used in combination as appropriate, depending on the purpose.

[0031] (6) Form of Use The form of use of the flocculant according to the present technology is not particularly limited, and it can be used in an appropriate form depending on the purpose of use of the flocculant. For example, when the flocculant according to the present technology is used in the water treatment described below, each component used in the flocculant according to the present technology may be added to the water to be treated in its solid state, or may be used in the form of a solution and / or dispersion dissolved and / or dispersed in a solvent. Furthermore, each component used in the flocculant according to the present technology may be used in a state where a portion of the component is dissolved in a solvent and the remaining portion is dispersed, that is, a solution and a dispersion are mixed. Furthermore, each component used in the flocculant according to the present technology may be added to a solvent in a state where some or all of them are mixed together in advance, or each component can be added to a solvent separately.

[0032] As described above, the flocculant according to the present technology described above can use synthetic polymers derived from petroleum as the linear water-soluble polymer and / or branched water-soluble polymer, but as shown in the examples described below, it can also exhibit excellent flocculation performance when using water-soluble polymers derived from plants. Using water-soluble polymers derived from plants as the linear water-soluble polymer and / or branched water-soluble polymer not only improves safety but also prevents the depletion of fossil resources, thereby contributing to the realization of a sustainable society.

[0033] This technology may be related to Goal 6 "Clean Water and Sanitation" and Goal 3 "Good Health and Well-Being" of the Sustainable Development Goals (SDGs) adopted at the United Nations Summit in 2015.

[0034] In the past, to achieve a high flocculation effect, it was necessary to select a flocculant made from petroleum-derived materials. However, the flocculant developed with this technology, despite being made from plant-derived materials, is able to exhibit flocculation performance equal to or better than that of flocculants made from petroleum-derived materials. Therefore, it is possible to improve safety for the environment and human health in various applications of flocculants, such as wastewater treatment. Furthermore, water treatment methods using this technology can achieve wastewater treatment that is highly safe for the environment and human health in a wide range of fields, including water supply and sewerage, the fermentation industry, the paper industry, the wood construction industry, and the mining industry, and can contribute to returning water resources to the water cycle within acceptable environmental impacts.

[0035] Furthermore, by using a plant-derived material as the flocculant according to the present technology, the presence of water-insoluble fibers and the like between the flocs can contribute to improving the filtration rate, as will be shown in the examples described later.

[0036] 2. Water Treatment Method The water treatment method according to the present technology is a method that involves at least adsorption and sedimentation. In addition, if necessary, an external modification step, a flocculant solution and / or flocculant dispersion preparation step, a separation step, etc., can be performed. Each step will be explained below in chronological order.

[0037] (1) External modification process The external modification process is a process of externally modifying the linear water-soluble polymer used in the flocculant of the present technology. Although the external modification process is not an essential process in the present technology, performing the external modification process can achieve both high flocculation performance and immediate effect.

[0038] The timing of the external modification step is not particularly limited as long as it is performed before the adsorption / sedimentation step, and the external modification step can be performed before or after the step of preparing a flocculant solution and / or a flocculant dispersion, which will be described later, or simultaneously with the step of preparing a flocculant solution and / or a flocculant dispersion, or can be performed multiple times. In the present technology, the external modification step is preferably performed before the step of preparing a flocculant solution and / or a flocculant dispersion.

[0039] Other details of the external modification are the same as those described above, and therefore will not be described here.

[0040] (2) Flocculant Solution and / or Flocculant Dispersion Preparation Step In the flocculant solution and / or flocculant dispersion preparation step, the flocculant according to the present technology described above may be used as is or in the form of a paste, or may be dissolved and / or dispersed in any solvent to prepare a solution and / or dispersion. The flocculant solution and / or flocculant dispersion preparation step is not an essential step in the present technology, and the flocculant can be directly subjected to the adsorption / sedimentation step described later, or a preparation formulation that has been prepared in advance as a flocculant solution and / or flocculant dispersion can be used.

[0041] The method for preparing the flocculant solution and / or flocculant dispersion can be one or more general preparation methods, as long as the action and effect of the present technology are not impaired. A specific method includes, for example, adding the flocculant according to the present technology to any solvent and mixing it. When mixing, heating, pressurization, cooling, etc. may be performed as necessary. When adding the flocculant according to the present technology to the solvent, the components used in the flocculant according to the present technology may be mixed in part or all and then added to the solvent, or each may be added to the solvent separately.

[0042] The solvent that can be used in this technology can be selected appropriately depending on the type of components used in the flocculant, etc. In this technology, for example, purified water or tap water can be used as the solvent.

[0043] The contents of the components used in the flocculant according to the present technology in the flocculant solution and / or flocculant dispersion and other details are as described above, and therefore will not be described here.

[0044] (3) Adsorption / Sedimentation Process The adsorption process is a process in which the target substances are adsorbed and precipitated by the flocculant according to the present technology in the water to be treated. The flocculant according to the present technology is not limited to pollutants, harmful substances, unnecessary substances, etc. as the target substances to be adsorbed, but can also adsorb useful substances depending on the purpose.

[0045] In the adsorption and sedimentation process, the flocculant according to the present technology, and a flocculant solution and / or flocculant dispersion prepared as necessary, are added to the water to be treated. When the flocculant according to the present technology is added directly to the water to be treated, the components used in the flocculant according to the present technology may be mixed in part or all and then added to the water to be treated, or each component may be added separately to the water to be treated. When the prepared flocculant solution and / or flocculant dispersion is added to the water to be treated, it may be added all at once or in multiple batches.

[0046] The amount of flocculant added to the water to be treated can be freely set depending on the type and amount of target substance in the water to be treated, as long as it does not impair the function and effect of the present technology. In this technology, the lower limit of the amount of flocculant (solute part in the case of a flocculant solution and / or flocculant dispersion) added to the water to be treated is, for example, 0.1 ppm or more, preferably 0.5 ppm or more, more preferably 1.0 ppm or more, and even more preferably 1.5 ppm or more. The upper limit of the amount of flocculant (solute part in the case of a flocculant solution and / or flocculant dispersion) added to the water to be treated is, for example, 10.0 ppm or less, preferably 8.0 ppm or less, and more preferably 7.0 ppm or less. By setting the amount of flocculant added to the water to be treated within this range, sufficient flocculation performance can be achieved.

[0047] As the adsorption and sedimentation method, one or more adsorption and sedimentation methods using common flocculants can be used freely, as long as they do not impair the action and effect of the present technology. Specific methods include, for example, a method in which the flocculant according to the present technology, a flocculant solution and / or a flocculant dispersion prepared as needed, are introduced into the water to be treated, mixed, and left to stand for a certain period of time. When mixing and / or leaving, heating, pressurization, cooling, etc. may be performed as necessary.

[0048] (4) Separation step The separation step is a step of separating the flocculants formed in the adsorption and sedimentation steps from the treated water. Although the separation step is not an essential step in this technology, performing the separation step can improve the safety of the supernatant water when it is discharged, and can also enable the reuse of the supernatant water and the flocculants.

[0049] As the separation method, one or more common separation methods can be freely used as long as they do not impair the functions and effects of the present technology. Examples include methods using a filter press, a vacuum dehydrator, a belt press dehydrator, a centrifugal dehydrator, a screw press, etc.

[0050] As mentioned above, the flocculant of this technology can use plant-derived polymers, so the flocculants generated after water treatment are safe and reusable, and can be safely and biodegradably disposed of in landfills, converted into fuel, or composted, contributing to environmental conservation and the realization of a renewable society.

[0051] The present technology may also have the following configurations: (1) A flocculant containing a pseudo-crosslinked product formed by subjecting a linear water-soluble polymer to physical interaction. (2) The flocculant according to (1), wherein the physical interaction is at least one action selected from intermolecular interaction and surfactant action, and wherein the linear water-soluble polymer has a cyclic structure in its main chain. (3) The flocculant according to (1) or (2), wherein the physical interaction is an intermolecular interaction. (4) The flocculant according to (2) or (3), wherein the pseudo-crosslinking due to intermolecular interaction is performed using a branched water-soluble polymer. (5) The flocculant according to (2), wherein the pseudo-crosslinking due to surfactant action is performed using a reducing agent. (6) The flocculant according to any one of (2) to (5), wherein the cyclic structure of the linear water-soluble polymer is an alicyclic structure. (7) The flocculant according to (6), wherein the linear water-soluble polymer is a plant-derived linear water-soluble polymer. (8) The flocculant according to (7), wherein the plant-derived linear water-soluble polymer is a plant-derived water-soluble polysaccharide. (9) The flocculant according to (8), wherein the plant-derived water-soluble polysaccharide is a water-soluble polysaccharide contained in a plant. (10) The flocculant according to (9), wherein the plant is one or more plants selected from mulukhiyah, okra, long-chain jute, jute, matsuna (Japanese mustard spinach), mitsuba (Japanese mitsuba), mizuna (potherb mustard greens), spinach, banana, nameko mushroom, Japanese yam, okra, and mekabu (wheat bran). (11) The flocculant according to any one of (4) to (10), wherein the branched water-soluble polymer has a cyclic structure in its main chain. (12) The flocculant according to (11), wherein the cyclic structure of the branched water-soluble polymer is an alicyclic structure. (13) The flocculant according to (12), wherein the branched water-soluble polymer is a thickening polysaccharide. (14) The flocculant according to (13), wherein the thickening polysaccharide is one or more thickening polysaccharides selected from inulin, galactomannan, and glucan. (15) The flocculant according to any one of (5) to (10), wherein the reducing agent is one or more reducing agents selected from hydrogen peroxide, ozone, oxalic acid, oxalate, lithium aluminum hydride, hydrazine, and formic acid. (16) The flocculant according to any one of (1) to (16), wherein the linear water-soluble polymer is an externally modified polymer.(17) The flocculant according to (16), wherein the external modification is one or more modifications selected from physical modification, photomodification, and thermal modification. (18) A water treatment method comprising a step of adsorbing and precipitating a target substance to a flocculant containing a pseudo-crosslinked body obtained by subjecting a linear water-soluble polymer to physical interaction. (19) A water treatment method comprising a step of adsorbing and precipitating a target substance to the flocculant according to any one of (1) to (17). (20) The water treatment method according to (18) or (19), wherein an external modification step of externally modifying the linear water-soluble polymer is carried out before the adsorption and precipitating step.

[0052] The present technology will be described in more detail below based on examples. Note that the examples described below are examples of typical examples of the present technology, and the scope of the present technology should not be construed as being narrow.

[0053] <Raw Materials> The raw materials used in the examples are shown in Table 1 below. In each experimental example, the following raw materials were used unless otherwise specified.

[0054]

[0055] Experimental Example 1 In Experimental Example 1, a study was conducted to examine the difference in the flocculating effect due to differences in the materials used for the flocculant.

[0056] (1) Preparation of Flocculant The materials shown in Tables 2 and 3 below were measured and mixed to prepare aqueous flocculant solutions according to the examples and comparative examples.

[0057] (2) Viscosity measurement and calculation of specific viscosity The viscosity of each of the prepared aqueous flocculant solutions was measured using a vibration viscometer (VM-10A manufactured by Sekonic Corporation). The aqueous solution 6 hours after preparation of each aqueous flocculant solution was designated as aqueous solution A, and the aqueous solution 30 minutes after preparation of each aqueous flocculant solution was designated as aqueous solution B, with the specific viscosity of aqueous solution A being designated as specific viscosity A and the specific viscosity of aqueous solution B being designated as specific viscosity B. Each specific viscosity was calculated by subtracting the viscosity of the solvent from the viscosity of each aqueous solution at room temperature and dividing the value by the viscosity of the solvent.

[0058] (3) Evaluation of Viscosity Increase Rate The increase or decrease from the theoretical value calculated from the specific viscosity of each aqueous solution was evaluated.

[0059] (4) Evaluation of coagulation properties Calcium fluoride dispersion (pH 7.8) 100 cm ３ The resulting solution was placed in a settling tube, and 590 ppm of aluminum sulfate was added. Each of the prepared flocculant aqueous solutions was added so that the solute content was 2.4 ppm, and the rate at which the settling interface decreased was evaluated as the settling velocity (cm / s). The settling velocity when aqueous solution A was used was settling velocity A.

[0060] (5) Evaluation of Clarity After the evaluation of aggregation using aqueous solution A, the clarity of each supernatant was visually evaluated after a predetermined time had elapsed based on the following evaluation criteria: ○: No turbidity at all △: Slight turbidity but within the acceptable range ×: Turbidity

[0061] (6) Results The results of the Examples are shown in Table 2, and the results of the Comparative Examples are shown in Table 3. Reference Example 1 was an example in which only a solvent was used without using a flocculant.

[0062]

[0063]

[0064] (7) Discussion Comparing Examples 1 to 4 in Table 2 with Comparative Examples 1 and 2 in Table 3, it was found that Examples 1 to 4, in which the linear water-soluble polymer A was used in combination with the branched water-soluble polymer H, I, or J, had a higher sedimentation rate than Comparative Examples 1 and 2, in which only the linear water-soluble polymer A was used. Similarly, comparing Example 5 in Table 2 with Comparative Example 3 in Table 3, Examples 6 and 7 in Table 2 with Comparative Example 4 in Table 3, Example 8 in Table 2 with Comparative Example 5 in Table 3, Example 9 in Table 2 with Comparative Example 6 in Table 3, Examples 10 and 11 in Table 2 with Comparative Example 7 in Table 3, and Example 12 in Table 2 with Comparative Example 8 in Table 3, it was found that Examples 5 and 9 to 12, in which the linear water-soluble polymer and the branched water-soluble polymer were used in combination, had a higher sedimentation rate than Comparative Examples 3 to 8, in which only the linear water-soluble polymer was used.

[0065] Furthermore, it was found that Examples 1, 2, 5, 6, 8 to 10, 12, and 19, in which branched water-soluble polymer H was used in combination with any of linear water-soluble polymers A to G, had a higher sedimentation rate than Comparative Example 9, in which branched water-soluble polymer H was used alone. Similarly, it was found that Examples 3, 7, and 11, in which branched water-soluble polymer I was used in combination with linear water-soluble polymers A, C, or F, had a higher sedimentation rate than Comparative Example 10, in which branched water-soluble polymer I was used alone, and that Example 4, in which branched water-soluble polymer J was used in combination with linear water-soluble polymer A, had a higher sedimentation rate than Comparative Example 11, in which branched water-soluble polymer J was used alone.

[0066] Furthermore, it was found that Example 13, in which synthetic linear water-soluble polymer K was used in combination with plant-derived branched water-soluble polymer H, had a higher sedimentation rate than Comparative Example 15, in which only synthetic linear water-soluble polymer K was used, despite the use of a smaller amount of synthetic polymer, which is considered to be more effective. Similarly, it was found that Example 14, in which synthetic linear water-soluble polymer L and plant-derived branched water-soluble polymer H were used in combination, had a higher sedimentation rate than Comparative Example 16, in which only synthetic linear water-soluble polymer L was used, and that Example 15, in which synthetic branched water-soluble polymer M and plant-derived linear water-soluble polymer F were used in combination, had a higher sedimentation rate than Comparative Example 17, in which only synthetic branched water-soluble polymer M was used.

[0067] In addition, it was found that the sedimentation rate was faster in Examples 16 and 17, in which the linear water-soluble polymer A was used in combination with reducing agent α or β, than in Comparative Example 1, in which only the linear water-soluble polymer A was used. Similarly, it was found that the sedimentation rate was faster in Example 18, in which the linear water-soluble polymer C was used in combination with reducing agent α, than in Comparative Example 4, in which only the linear water-soluble polymer C was used.

[0068] From these results, it was considered that the flocculation property and sedimentation rate were improved by the linear water-soluble polymer being pseudo-crosslinked by the branched water-soluble polymer or the reducing agent.

[0069] Experimental Example 2 In Experimental Example 2, the effect of flocculation when a linear water-soluble polymer used as a flocculant is externally modified was examined.

[0070] (1) External Modification As external modification of the linear water-soluble polymer, physical modification, photo-modification, or thermal modification was carried out under the following conditions before preparing the aqueous flocculant solution.

[0071] [Physical Modification] The linear water-soluble polymer was treated by applying shear force to it using a mill (SG-10BKJ manufactured by Cuisinart) at a rotation speed of 22,000 r / min for 40 seconds.

[0072] [Photo-modification] The linear water-soluble polymer was treated using a metal weather exposure tester (KW-R5TP-A manufactured by Daipla Wintes Co., Ltd.) so as to achieve the radiation exposure dose (300 to 400 nm) shown in Table 4 below.

[0073] [Thermal Modification 1] A linear water-soluble polymer was treated at 60°C for 24 hours.

[0074] [Thermal Modification 2] The linear water-soluble polymer was treated at 120°C for 6 hours.

[0075] (2) Preparation of Flocculant The materials shown in Table 4 below were measured and mixed to prepare aqueous flocculant solutions according to the examples and comparative examples.

[0076] (3) Measurement of Viscosity and Calculation of Specific Viscosity Using the same method as in Experimental Example 1, the viscosity of each of the aqueous flocculant solutions prepared above was measured and the specific viscosity was calculated.

[0077] (4) Calculation of dissolution rate For each of the prepared flocculant aqueous solutions, the specific viscosity B was calculated by dividing the specific viscosity A. The closer to "1", the higher the dissolution rate, i.e., the shorter the pretreatment time in industrial terms.

[0078] (5) Evaluation of Coagulation Properties In the same manner as in Experimental Example 1, the settling velocity when aqueous solution B of each of the prepared aqueous coagulant solutions was used was taken as settling velocity B.

[0079] (6) Results The results are shown in Table 4.

[0080]

[0081] (7) Discussion As shown in Table 4, Comparative Example 29, which used a synthetic linear water-soluble polymer, had a very high specific viscosity A but a low dissolution rate. In other words, the wastewater purification performance was high, but the immediate effect was poor. In contrast, when Comparative Examples 19 to 23, 24 to 26, and 27 and 28 were compared, it was found that external modification of the plant-derived linear water-soluble polymer improved the dissolution rate of the flocculant using this polymer, but reduced the specific viscosity A. In other words, it was found that the immediate effect was improved, but the wastewater purification performance was reduced.

[0082] On the other hand, as shown by the results of Examples 20 to 29, it was found that by using this technology in which a linear water-soluble polymer is pseudo-crosslinked with a branched water-soluble polymer or a reducing agent, and by externally modifying the plant-derived linear water-soluble polymer, it is possible to improve the dissolution rate of the flocculant using this polymer while preventing a decrease in the specific viscosity A. In other words, it was shown that by combining this technology in which a linear water-soluble polymer is pseudo-crosslinked with a branched water-soluble polymer or a reducing agent with the technology of external modification, it is possible to achieve both immediate effectiveness and high wastewater purification performance.

[0083] Experimental Example 3 In Experimental Example 3, the effects on the settling velocity and filtration rate in the treatment of actual industrial wastewater were examined.

[0084] (1) Raw Materials The raw materials used in Experimental Example 3 are shown in Table 5 below.

[0085]

[0086] (2) Test method: The test liquid was placed in a 100 mL sedimentation tube, and the settling velocity was measured when 7.2 ppm of each material shown in Table 6 below was added. The floc liquid formed after measuring the settling velocity was filtered using filter paper (Toyo Roshi Kaisha, Ltd., "No. 5C", diameter: 185 mm). The filtration velocity was calculated from the amount of filtrate after 5 minutes.

[0087] (3) Results The results are shown in Table 6 below.

[0088]

[0089] (4) Discussion As shown in Table 6, the mixture of a linear water-soluble polymer and a branched water-soluble polymer exhibited a sedimentation rate equivalent to that of a commercially available polymer flocculant. Meanwhile, the filtration rate of the mixture of a linear water-soluble polymer and a branched water-soluble polymer was higher than that of the commercially available polymer flocculant. These results confirmed that the use of plant-derived raw materials as the flocculant of the present technology provides high flocculation performance and high filtration performance.

Claims

1. A flocculant containing a pseudo-crosslinked substance formed by physical interaction with a linear water-soluble polymer.

2. The flocculant according to claim 1, wherein the physical interaction is at least one action selected from the group consisting of intermolecular interaction and surfactant action, and the linear water-soluble polymer has a cyclic structure in its main chain.

3. The flocculant according to claim 1, wherein the physical interaction is an intermolecular interaction.

4. The flocculant according to claim 2, wherein the pseudo-crosslinking due to intermolecular interactions is performed using a branched water-soluble polymer.

5. The flocculant according to claim 2, wherein the pseudo-crosslinking due to surfactant action is pseudo-crosslinking performed using a reducing agent.

6. The flocculant according to claim 2, wherein the cyclic structure of the linear water-soluble polymer is an alicyclic structure.

7. The flocculant according to claim 6, wherein the linear water-soluble polymer is a plant-derived linear water-soluble polymer.

8. The flocculant according to claim 7, wherein the plant-derived linear water-soluble polymer is a plant-derived water-soluble polysaccharide.

9. The flocculant according to claim 8, wherein the plant-derived water-soluble polysaccharide is a water-soluble polysaccharide contained in a plant.

10. The flocculant according to claim 9, wherein the plant is one or more plants selected from molokheiya, okra, jute, matsuna, mitsuba, mizuna, spinach, banana, nameko mushroom, yam, okra, and mekabu.

11. The flocculant according to claim 4, wherein the branched water-soluble polymer has a cyclic structure in the main chain.

12. The flocculant according to claim 11, wherein the cyclic structure of the branched water-soluble polymer is an alicyclic structure.

13. The flocculant according to claim 12, wherein the branched water-soluble polymer is a thickening polysaccharide.

14. The flocculant according to claim 13, wherein the thickening polysaccharide is one or more thickening polysaccharides selected from inulin, galactomannan, and glucan.

15. The flocculating agent of claim 5, wherein the reducing agent is one or more selected from hydrogen peroxide, ozone, oxalic acid, oxalates, lithium aluminum hydride, hydrazine, and formic acid.

16. A water treatment method comprising a step of adsorbing and precipitating a target substance using a flocculant containing a pseudo-crosslinked substance formed by subjecting a linear water-soluble polymer to physical interaction.

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