JP2005211776A - Method and apparatus for recovering anion surfactant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for recovering an anion surfactant of high purity and high concentration reusable also for the initial purpose of use, from industrial waste water which is arisen from industries where the consumption of the surfactant is large, or industrial waste water, or the like, having a low concentration of surfactant content but a high exhaust quantity which is produced in emulsion polymerization, or the like. <P>SOLUTION: The recyclable anion surfactant of high purity and high concentration can be recovered from anion surfactant-containing waste water by a series of following processes; a separation process of adding a coagulant to the anion surfactant-containing waste water while mixing both, coagulating the anion surfactant in an aqueous solution and separating/recovering the sediment: a concentration process of subjecting the recovered sediment to water dispersion treatment under an acidic environment and increasing the content of the anion surface active agent in the sediment: a refining process of rinsing the concentrated sediment: a recovery process of adding an eluant to the rinsed sediment while mixing and stirring both, eluting the anion surfactant to an eluent phase and recovering the surfactant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for recovering an anionic surfactant from an aqueous solution containing an anionic surfactant. More particularly, the present invention relates to a method and an apparatus for recovering an anionic surfactant that can be reused in an original use of a surfactant with a high concentration and high purity from an aqueous solution containing an anionic surfactant such as industrial wastewater.

Methods for removing (separating) the surfactant from the aqueous solution containing an anionic surfactant have been studied from the viewpoint of the influence of domestic wastewater on the environment. For example, biological treatment, oxidative decomposition, foam separation, coagulation separation, extraction method, Various methods such as an adsorption method, an ion exchange method, and membrane filtration are known (Non-Patent Documents 1, 2, etc.). However, since these methods are not intended to reuse the separated and recovered surfactant, the method for regenerating the surfactant is not specified, and it is extremely difficult to reuse the surfactant as it is. In addition, a device for recovering a surfactant from wastewater from a washing machine or a dishwasher has been proposed (Patent Documents 1, 2, etc.). However, these are those utilizing the adsorptivity of the surfactant to the foam, and application to industrial wastewater with a large amount of wastewater is impractical because the yield is low instead of the scale of the device. Moreover, although the recovery method of the surfactant from a papermaking process is also proposed by the same collection | recovery principle (patent document 3), there exists a preferable density | concentration with 400-700 ppm, and the density | concentration which makes surfactant micelle, For example, concentration by bubbles to 0.2% or more is almost difficult. Furthermore, the concentration for storage is too low to recover and reuse, and a large storage volume is required, or it is inconvenient to dilute and reuse. In addition, a wastewater treatment device that separates and reuses the emulsion by ultrafiltration membrane device has also been proposed (Patent Document 4). However, in the treatment of industrial wastewater that has a large amount of wastewater and contains many components, facility costs and equipment maintenance are also required. In addition, the wastewater containing water-soluble or acidic substances similar to the surfactant in the behavior of the ultrafiltration membrane is not preferable because impurities are concentrated together with the surfactant by repeated treatment. Moreover, although the usage method of the collect | recovered material collect | recovered by the process is also proposed (patent document 5), it is not the use of the surfactant used with the mold release agent which is the original purpose, It is described that it can be separated and dehydrated as aggregates and used as aggregates for concrete and mortar, and there are limitations on the use of recovered materials, including the original purpose of use of surfactants, surface active properties It is not a reusable collection for the purpose of using.
JP-A-6-178985 JP-A-8-24839 JP 5-140886 JP-A-6-39375 JP 2001-137863 A Oil Chemistry (Vol. 24, No. 11 (1975) P757) Water treatment technology (Vol.6, No.9, 1965, P7)

  Surfactant-containing aqueous wastewater is often found in domestic wastewater and industrial wastewater, and is one of the environmental problems. In particular, the industry that produces a large amount of wastewater is implementing measures to reduce the burden on the natural world through wastewater treatment as a countermeasure. For example, industrial wastewater containing surfactants partially coagulates and separates surfactants with coagulating sedimentation agents, and the remaining surfactants that could not be separated in the coagulation sedimentation process are treated with activated sludge treatment. It is discharged into the natural world through purification processes such as reducing the concentration of the activator. However, on the other hand, agglomerates due to the coagulating sediments generated during wastewater treatment and sludge separated by activated sludge treatment are also an environmental problem because a large amount of discharge to the natural environment at once is a heavy load, and as a result, it is an effective land for cultivation. The use of soil as a soil improvement material has been studied in part, but incineration disposal has become a practical treatment method because most of them have quality problems. However, if it can be reused without incineration, especially if it can be reused for the original purpose, eco-friendly economic activities are possible, such as reducing the supplement of new surfactants while maintaining the current industrial activities. It becomes. For this purpose, it is necessary to establish a technique for recovering surfactants with low impurities that can be reused, and it is also necessary to newly develop equipment for recovery.

  Therefore, the present invention can be applied to industrial wastewater discharged from industries where surfactants are frequently used, for example, from industrial wastewater containing a small amount of surfactant-containing concentration generated by emulsion polymerization, etc. An object of the present invention is to provide a method and an apparatus for recovering a high concentration of anionic surfactant that satisfies reusable purity.

  The inventors have (1) a step of selectively adsorbing a target anionic surfactant component from an aqueous solution having a low surfactant concentration to separate it as a precipitate, and then (2) an anion in the separated precipitate. A step of further increasing the concentration of the surfactant and concentrating; and (3) a step of washing and purifying because the precipitate contains unnecessary components, and (4) a precipitate separated by purification. Combined with a series of methods consisting of an elution step for eluting and recovering the desired anionic surfactant, and an apparatus therefor, it can be reused from an aqueous solution containing an anionic surfactant in high concentration and high purity. A recovery method and a recovery apparatus for a possible anionic surfactant have been found, and the above object has been achieved.

  That is, the present invention is a method of recovering an anionic surfactant from an aqueous solution containing an anionic surfactant, and (1) adding and mixing an aggregation precipitant to the aqueous solution to coagulate and precipitate the anionic surfactant in the aqueous solution. (2) a concentration step for increasing the content of the anionic surfactant in the precipitate by subjecting the precipitate thus separated and recovered to water dispersion under acidic conditions; 3) a purification step of washing the concentrated precipitate with water, and (4) a recovery step of adding an eluent to the water-washed precipitate and mixing and stirring to elute and recover the anionic surfactant in the eluent phase. A method for recovering an anionic surfactant characterized by comprising (Invention 1).

  The method for recovering an anionic surfactant according to the first aspect of the present invention, wherein a pH treatment with hydrochloric acid is performed during the acidic water dispersion treatment (the second aspect of the present invention).

  In the first and second aspects of the present invention, the method for recovering an anionic surfactant in which the coagulating precipitant is an aluminum-based coagulant (Invention 3).

  In the first to third aspects of the invention, after the purification step is concentrated by increasing the content of the anionic surfactant in the concentration step, the precipitate separated by solid-liquid separation has a conductivity of washing water after washing of 100 mS / A method for recovering an anionic surfactant, which is washed with deionized water until m or less (Invention 4).

  In the present inventions 1 to 4, a method for recovering an anionic surfactant using an alkaline aqueous solution as an eluent in the recovery step (invention 5).

  In the present inventions 1 to 5, the anionic surfactant is eluted in the elution liquid phase in the recovery step, the eluent is added to the precipitate after solid-liquid separation and recovery, and the mixture is stirred and mixed. A method for recovering an anionic surfactant comprising a re-recovery step for eluting and recovering a surfactant (present invention 6).

  In the present invention 6, the separation liquid containing the anionic surfactant recovered by eluting the anionic surfactant from the precipitate in the re-recovery step is circulated to the recovery step and washed with water in the purification step. A method for recovering an anionic surfactant used as an eluent for eluting an anionic surfactant from a product (present invention 7).

  An agglomeration reaction tank for aggregating and precipitating an anionic surfactant in the aqueous solution by adding and mixing an agglomeration precipitating agent to an aqueous solution containing an anionic surfactant, and solid-liquid separation for separating the precipitate prepared in the agglomeration reaction tank An acid treatment tank for adding an acid to the precipitate separated and recovered by the solid-liquid separation tank and increasing the content of the anionic surfactant in the precipitate by subjecting the precipitate to water dispersion treatment under acidity; , A first solid-liquid separation means for solid-liquid separation of the water dispersion treatment liquid, a purification tank for washing the precipitate separated by the first solid-liquid separation means, and a precipitate washed with water in the purification tank A second solid-liquid separation means for separating water, and an eluent added to the precipitate separated by the second solid-liquid separation means, mixed and stirred to obtain a sludge dispersion, and elution of the sludge dispersion Elution tank for eluting an anionic surfactant in the liquid phase And a third solid-liquid separation means for recovering an aqueous solution of the anionic surfactant by solid-liquid separation of the sludge dispersion containing the anionic surfactant eluted in the elution tank. An apparatus for recovering an anionic surfactant from an aqueous solution containing a surfactant (Invention 8).

In the present invention 8, the anionic surfactant is eluted in the elution liquid phase in the elution tank, and the eluent is added to the precipitate after solid-liquid separation and recovery, followed by mixing and stirring to obtain a sludge dispersion and elution A re-elution tank for eluting the anionic surfactant in the liquid phase and a sludge dispersion containing the anionic surfactant eluted in the re-elution tank are separated into solid and liquid to recover an anionic surfactant-containing water volume. And an apparatus for recovering an anionic surfactant comprising the solid-liquid separation means (invention 9).
The sludge dispersion liquid containing the anionic surfactant eluted in the re-elution tank is transferred again to the third solid-liquid separation means, so that the third solid-liquid separation means is changed to the fourth solid-liquid separation means. It can also be used as a solid-liquid separation means.

  In the present invention 9, in the re-elution tank, an anionic surfactant is eluted from the precipitate, and the anionic surfactant aqueous solution recovered by solid-liquid separation is circulated to the elution tank and used as an eluent. An anionic surfactant recovery device (Invention 10).

In the present invention 8 or 9, the anionic surfactant recovery device using the centrifuge as the solid-liquid separation means (present invention 11).
A centrifuge can also be used as the fourth solid-liquid separation means in the ninth aspect of the present invention.

  According to the recovery method and the recovery apparatus of the present invention, a high-concentration surfactant having a practically satisfactory purity can be recovered from a used anionic surfactant-containing aqueous solution, and the recovered anion interface can be recovered. The activator can be recycled for use in the original application field. Therefore, since the amount of surfactant consumed can be reduced, the load of wastewater treatment can be reduced, and costs such as raw material costs and wastewater treatment costs in business activities can be expected.

  In the present invention, the precipitate containing the anionic surfactant coagulated and precipitated with the coagulating precipitant in the separation step is subjected to an aqueous dispersion treatment under acidic conditions. By this acid treatment, excess aggregated precipitant in the precipitate is eluted, the content of the anionic surfactant is increased, the subsequent anionic surfactant recovery operation is facilitated, and the recovery rate is also improved.

  According to the second aspect of the present invention, when the pH treatment is performed with hydrochloric acid during the acidic water dispersion treatment, the yield of the anionic surfactant is improved and the separation property of the precipitate is improved.

  According to the third aspect of the present invention, the aluminum content is limited as in the case of using the recovered anionic surfactant as an emulsifier for emulsion polymerization, for example, by using an aluminum-based flocculant as the flocculant precipitant. It can also be used for applications.

  According to the present invention 4, in the purification step, the concentration of the anionic surfactant in the concentration step is increased and concentrated, and then the solid-liquid separated precipitate has a conductivity of 100 mS / m after washing. By washing with deionized water until it becomes below, it is possible to recover a high purity anionic surfactant with few impurities.

  According to the fifth aspect of the present invention, the processing cost can be suppressed by using a relatively inexpensive alkaline aqueous solution as the eluent in the recovery step.

  In the recovery step, the anionic surfactant that can be reused is still contained in the precipitate (sludge) after elution of the anionic surfactant into the eluent phase and solid-liquid separation. Therefore, as in the present invention 6 and the present invention 9, the anionic surfactant is eluted in the eluent phase in the recovery step, and the eluent is added to the precipitate (sludge) collected by solid-liquid separation and mixed. Although the concentration of the recovered anionic surfactant is reduced compared to the first recovery step by providing a re-recovery step of stirring and eluting the anionic surfactant into the eluent phase to recover the surfactant, The anionic surfactant can be recovered by elution separation in the added eluent phase, and the recovery rate of the anionic surfactant can be improved.

  Further, as in the present invention 7 and the present invention 10, an eluent (separate) containing an anionic surfactant recovered by eluting the anionic surfactant from the precipitate in the re-recovery step is recovered in the recovery step. The concentration of the anionic surfactant recovered in the recovery step can be increased by using it as an eluent for elution of the anionic surfactant from the precipitate obtained in the purification step.

  In addition, solid-liquid separation of cohesive aggregated precipitates is clogged with filter medium filtration, and filter medium replacement becomes frequent and the separation work becomes complicated. In the recovery apparatus of the present invention 11, acid treatment is performed. After that, by using a centrifuge as a means for solid-liquid separation of the precipitate after washing and elution of the anionic surfactant, the solid-liquid separation can be performed continuously, making it easy to automate the recovery device and introducing the equipment. There is also an advantage that can be made compact equipment.

  Hereinafter, the present invention will be described in detail. Examples of the aqueous solution (raw water) containing an anionic surfactant to which the present invention can be applied include synthesis of an anionic surfactant and waste water from an application industry or a joint integrated waste water treatment facility. Examples of the anionic surfactant that can be recovered from the waste water according to the present invention include, for example, one or more of a carboxyl group, a sulfate group, a sulfonate group, or a phosphate group as an anionic hydrophilic group in the molecule. In addition to the saturated aliphatic or unsaturated aliphatic higher alkyl group having 6 to 24 carbon atoms as the lipophilic group, a fluorocarbon in which part or all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms, Or the thing containing the naphthalene group etc. which are obtained through the alkylallyl group which aromatic hydrocarbon couple | bonded, formalin condensation, etc. are mentioned, However, It is not limited to these. Of course, even if the surfactant molecule contains an amide group, a carboxylic acid ester, an ether bond, a hydroxyl group, an amino group, etc. in addition to the hydrophilic group or lipophilic group as described above, It does not inhibit the recovery of these surfactants. Among these anionic surfactants, those to which the present invention can be suitably applied include higher alkyl carboxylates (particularly sodium salts) such as sodium dodecanoate, sodium tetradecanoate, sodium hexadecanoate, and sodium octadecanoate; Sulfate esters of higher alcohols (especially sodium salts) such as sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium hexdecyl sulfate, sodium octadecyl sulfate; sodium dodecylbenzenesulfonate, sodium tetradecylbenzenesulfonate, sodium hexadecylbenzenesulfonate, octadecyl Higher alkyl benzene sulfonates (particularly sodium salts) such as sodium benzene sulfonate. Among these, the present invention is also effective for the higher alkylbenzene sulfonates that are difficult to separate and collect by the activated sludge method. In addition, 2 or more types of these anionic surfactants may be contained in raw | natural waters, such as the said waste_water | drain, which collect | recovers anionic surfactants.

  The aqueous solution containing an anionic surfactant such as waste water has a concentration of an anionic surfactant in the aqueous solution of 3% or less, usually 2 to 0.001%, due to the use of the anionic surfactant or the circumstances of drainage. In many cases, impurities are mixed in the aqueous solution, or the concentration of the anionic surfactant is too thin, so that it cannot be reused as it is. Therefore, in order to recover the target anionic surfactant from the aqueous solution, it is necessary to remove impurities and separate the anionic surfactant component. In particular, when an oil component is contained in the aqueous solution as an impurity, when the anionic surfactant is recovered from the aqueous solution, before the aggregation precipitation operation is performed in the separation step described later, the oil solution is previously used in the aqueous solution. It is important to remove the oil.

  FIG. 1 is a process explanatory diagram of a method for recovering an anionic surfactant according to the present invention. As shown in FIG. 1, the method for recovering an anionic surfactant according to the present invention includes (1) adding and mixing an aggregating precipitant to an aqueous solution containing the anionic surfactant to coagulate and precipitate the anionic surfactant in the aqueous solution. (2) a concentration step for increasing the concentration of the anionic surfactant in the precipitate to concentrate it by subjecting the precipitate thus separated and recovered to water dispersion under acidic conditions; 3) Purification step of washing the concentrated precipitate with water, and (4) Adding an eluent to the washed precipitate, mixing and stirring, and eluting the anionic surfactant into the eluent phase to recover the surfactant. It consists of a recovery process. In addition, (5) the anionic surfactant is eluted in the eluent phase in the recovery step, the eluent is added to the precipitate (sludge) after solid-liquid separation and recovery, and the mixture is stirred, and the anion surfactant is added to the eluent phase. A re-recovery step of eluting and recovering the surfactant can also be provided. Further, the eluent (separate) containing the anionic surfactant recovered by eluting the anionic surfactant from the precipitate (sludge) in the re-recovery step is circulated to the recovery step and washed with water in the purification step. It can also be used as an eluent when eluting the anionic surfactant from the subsequent precipitate. Hereafter, each said process is demonstrated in detail.

[Separation process]
In order to efficiently recover the anionic surfactant from the aqueous solution containing the anionic surfactant, it is necessary to selectively separate the anionic surfactant. As the method, it is preferable that in the separation step, an inorganic coagulating precipitant is added to the aqueous solution to coagulate and precipitate, and the anionic surfactant is adsorbed on the coagulating precipitant and separated from the aqueous solution. As the coagulating precipitant used in this case, commercially available aluminum-based and iron-based coagulating precipitants can be applied, but there is a limit to the iron content when reusing the recovered anionic surfactant. In this case, for example, when the recovered anionic surfactant is used as an emulsifier for emulsion polymerization, it is preferable to use an aluminum-based coagulating precipitant. The addition amount of the coagulating precipitant is preferably 1/100 to 100 times, more preferably 1/10 to 10 times the weight of the anionic surfactant in the raw water solution. If it is less than 1/100, the absolute amount of the recovered amount of the anionic surfactant is decreased. As a result, recovery from the raw water, that is, the recovery rate in the separation step is lowered, which is not preferable. In addition, if it exceeds 100 times, not only the amount of acid used in the acid treatment in the subsequent purification step increases, but also the content of the anionic surfactant in the precipitate is lowered, so that in the recovered liquid in the subsequent recovery step This leads to a decrease in the concentration and recovery rate of the anionic surfactant.

  The aggregated precipitate containing the anionic surfactant aggregated by the inorganic aggregated precipitant has a very high moisture content as it is, so the recovery concentration obtained by the elution operation of the anionic surfactant in the recovery step described later is the drainage concentration. There are limits to what can be enhanced. However, if the dehydration operation is forcibly performed on the aggregated precipitate for the purpose of reducing the water content of the aggregated precipitate, the filterability is poor in filter medium filtration because the precipitate particle size is small and the precipitation floc strength is weak. Centrifugation generally requires a great deal of time and centrifugal acceleration for separation. Therefore, in the separation process of the present invention, it is possible to separate by adding and mixing a water-soluble anionic polymer generally used as a water treatment agent in order to increase the floc strength of the precipitate and to perform the separation in a short time. Since it becomes easy to do, it is preferable. Examples of the anionic polymer used herein include derivatives derived from acrylamide homopolymers and copolymers, and polymers having a carboxyl group typified by sodium polyacrylate homopolymers and copolymers or sodium alginate. Sulfonic acid group-containing monomers and copolymers including vinyl sulfonic acid, styrene sulfonic acid or salts thereof; and sulfonic acid group-containing polymers found in polyacrylamide sulfomethylation products, etc. Although known, it is not limited to these.

  In order to separate and collect the aggregated precipitate having a high concentration of anionic surfactant that has been aggregated and precipitated as described above, a general solid-liquid separation apparatus can be applied. For example, it is possible to apply a device that requires some ingenuity in setting conditions, such as collecting cake by reducing the thickness of the cake in a filter, or increasing the pressure difference in the case of a pressure type. It is relatively easy to separate. From the viewpoint of installation area, workability of equipment, and maintenance, a centrifugal separation type is a preferable separation device. Of course, these separation devices may be used in combination.

[Concentration process]
In order to further increase the concentration of the anionic surfactant in the precipitate containing the anionic surfactant separated and recovered using the aluminum or iron-based precipitation flocculant in the separation step, acid treatment is performed. In addition, by this acid treatment, excess aggregated precipitant is eluted and removed, and the separability of the aggregated precipitate is improved. As a result, the content of the anionic surfactant in the solid-liquid separated precipitate is increased. As a result, the separation apparatus can be downsized and the equipment introduction conditions are advantageous.

  As an acid used for the acid treatment in the concentration step, an inorganic strong acid is generally preferable because of its large effect, and hydrochloric acid is preferable from the viewpoint of yield and separability of precipitates. The acidic pH is particularly preferably adjusted to 2 to 5, more preferably 2.5 to 4.5, and even more preferably 2.8 to 4.0. When the pH is less than 2, there is a drawback that the reconstitution of the precipitated flocculant becomes remarkable and the collected precipitate is reduced, and the elution of the anionic surfactant is increased and the recovery rate is lowered. When the pH exceeds 5, the ratio of the flocculant in the precipitate increases, so that not only the treatment scale of the solid-liquid separation apparatus after acid treatment increases, but also the anionic surface activity from the separated precipitate in the recovery step described later. This is inefficient and unpreferable because it increases the amount of precipitate treated when the agent is eluted and the amount of the alkali pH adjusting agent increases. Thus, after performing an acid treatment by a concentration process, a solid-liquid separation process is performed, and the isolate | separated solid substance (precipitate) is transferred to the refinement | purification process which is a post process.

[Purification process]
The precipitate containing the anionic surfactant acid-treated in the concentration step is purified by washing with water to remove impurities in the purification step. The water used for this washing is preferably pure water or deionized water subjected to ion exchange treatment. In washing with water, the precipitate is stirred and dispersed in water, and solid-liquid separation is performed again. In this case, a centrifuge can be used as the solid-liquid separation means. As a measure of washing with water, the washing liquid after washing, that is, the separation liquid is conducted until the conductivity becomes 100 mS / m or less, preferably 50 mS / m or less, more preferably 30 mS / m or less. The fact that the conductivity of the separation liquid exceeds 100 mS / m means that not only a large amount of ionic substances other than the eluted anionic surfactant but also non-ionic water-soluble substances are included. Therefore, so much of these impurities remain in the precipitate. Impurities in these precipitates are inconvenient for recycling the recovered surfactant. By washing with water until the conductivity of the separation liquid reaches the above value and removing impurities from the precipitate as much as possible, it is possible to recover the highly pure anionic surfactant.

[Recovery process]
Next, the precipitate recovered after solid-liquid separation after purification is mixed and stirred using an alkaline aqueous solution, a lower-boiling organic solvent such as lower alcohol or acetone as the eluent, and sludge in the precipitate is dispersed in the eluent. On the other hand, the anionic surfactant in the precipitate is eluted in the eluent phase and separated from the precipitate (sludge) and recovered. The amount of the eluent to be added depends on the water content of the collected precipitate, the stirring / mixing ability of the apparatus used in the collection step, the eluent separation ability, etc., but it is 0.5 to 20 times the weight of the precipitate. The amount is more preferably 0.8 to 3 times. If the amount is less than 0.5 times, the flowability of the precipitate dispersion is lowered, so that stirring and mixing properties are poor, and pH adjustment is difficult, which is not preferable. In addition, if the amount exceeds 20 times, the amount of separation of the eluent increases, so that a device having a large separation treatment capacity is required, the concentration of the anionic surfactant in the recovered liquid is reduced, and the container for storing the recovered liquid Is also not preferable because a larger one is required.

  The eluent is preferably an alkaline aqueous solution that requires less processing costs. The alkalinity of the elution system is an alkali metal hydroxide represented by sodium hydroxide or potassium hydroxide, or an alkali metal borate represented by sodium carbonate, sodium tetraborate, trisodium phosphate or sodium silicate. , Phosphate or silicate, quick lime or slaked lime can be used, but sodium hydroxide is preferred. The preferred pH of the elution system is 8-13, more preferably 9-12. If the pH is less than 8, the elution amount of the anionic surfactant from the precipitate is small and the recovery becomes inefficient, and if it exceeds 13, the anionic surfactant that has been eluted and separated in the eluent is altered, or the flocculant The aluminum used as an aluminate is not preferable because it becomes an aluminate and is mixed into the liquid phase and becomes an impurity.

  In the recovery step, the temperature at which the anionic surfactant is eluted from the precipitate into the eluent phase is preferably 10 ° C. or higher. In particular, when an alkaline aqueous solution is used as the eluent, the temperature is preferably 20 to 90 ° C, more preferably 30 to 80 ° C. When the alkaline aqueous solution is used at a temperature lower than 10 ° C., it cannot be recovered as a high-concentration solution due to the solubility of the anionic surfactant, and the shape of the whole treatment phase becomes a whipped cream in stirring during the elution operation, resulting in large stirring. Not only does it require power, it is difficult to adjust the pH, and there are drawbacks associated with difficulties in the subsequent solid-liquid separation operation. On the other hand, the upper limit of the temperature is not particularly troubled even at the boiling point under atmospheric pressure, but it is preferably 90 ° C. or lower because coloring of the aqueous solution containing the anionic surfactant gradually proceeds at a high temperature. More preferably, it is 80 degrees C or less.

  The eluent (separate) containing the anionic surfactant thus eluted can be reused as it is for the intended use.

[Re-collection process]
As described above, the precipitate (sludge) after elution of the anionic surfactant into the elution system and solid-liquid separation still contains a reusable anionic surfactant. Therefore, in the re-recovery step, the same eluent as above is added to the precipitate (sludge) after the anionic surfactant is recovered, and mixed and stirred, so that it is recovered compared to the first recovery step. Although the concentration of the anionic surfactant is reduced, the anionic surfactant remaining in the sludge is recovered by elution and separation in the added eluent phase, thereby improving the recovery rate of the anionic surfactant. Furthermore, repeated operations such as re-elution from the precipitate (sludge) separated by re-elution are also possible. The anionic surfactant-containing aqueous solution re-eluted in this manner can be reused as it is for the intended use.

  Furthermore, in order to increase the concentration of the anionic surfactant recovered from the raw water, the free liquid (anionic surfactant-containing aqueous solution) obtained by re-recovering the anionic surfactant as described above is recirculated to the recovery step and purified. It can also be used as an eluent when the anionic surfactant is recovered in the recovery step from the precipitate recovered by washing with water and solid-liquid separation.

  The apparatus for recovering an anionic surfactant according to the present invention for carrying out the method for recovering an anionic surfactant as described above is a coagulating precipitant in an aqueous solution containing an anionic surfactant such as industrial waste water as raw water. An agglomeration reaction tank for aggregating and precipitating the anionic surfactant in the aqueous solution by adding and mixing, a solid-liquid separation tank for separating flocs prepared in the agglomeration reaction tank and separating the precipitate, and the solid-liquid separation An acid is added to and mixed with the precipitate separated and recovered by the tank, and the precipitate is water-dispersed under acidity to increase the content of the anionic surfactant in the precipitate, and the water-dispersed liquid is A first solid-liquid separation means for solid-liquid separation; a purification tank for washing the precipitate separated by the first solid-liquid separation means; a second for separating the precipitate washed with water and the washing water in the purification tank; Solid-liquid separation means and the second solid-liquid separation means. An eluent is added to the precipitate separated by the separation means, mixed and stirred to obtain a sludge dispersion, and an anionic surfactant is eluted in the eluent phase of the sludge dispersion (elution system), and the elution And a third solid-liquid separation means for recovering the anionic surfactant aqueous solution by solid-liquid separation of the sludge dispersion containing the anionic surfactant eluted in the tank.

  The embodiment of the recovery device of the present invention will be described with reference to FIG. 2, which is a typical flow chart of recovering an anionic surfactant from an aqueous solution containing an anionic surfactant such as industrial wastewater. In FIG. 2, the reference numeral 1 indicates an anionic surfactant-containing aqueous solution to be raw water, and the reference numeral 5 indicates an agglomeration reaction tank. In this aggregation reaction tank 5, the raw water 1 and the acidic aluminum-based flocculant 3 are mixed. After mixing, the aqueous sodium hydroxide solution 2 is added and mixed to make the pH of the raw water (anionic surfactant-containing aqueous solution) 1 almost neutral, and then the anionic polymer 4 which is a polyacrylamide copolymer is added and mixed. To form a flock. In this agglomeration reaction tank 5, the tanks may be divided for each of the above-described drug addition facilities. What is shown by the code | symbol 7 is a solid-liquid separation tank for carrying out precipitation separation by using the floc in the raw water prepared by the aggregation reaction tank 5 as a precipitation phase. Reference numeral 8 denotes an acid treatment tank in which the precipitate 22 separated as a precipitation phase in the solid-liquid separation tank 7 and an inorganic acid (for example, hydrochloric acid) 9 are added and mixed to adjust the acidity. What is indicated by reference numeral 12A is a centrifuge (decanter type) as a first solid-liquid separation means for forcibly performing solid-liquid separation after acid treatment in the acid treatment tank 8. What is shown by the code | symbol 14 is the refinement | purification tank which wash | cleans the deposit 25 isolate | separated with the centrifuge 12A and collect | recovered with the deionized water 13 after the said acid treatment. Further, what is denoted by reference numeral 18 is a mixture obtained by washing and purifying with a purification tank 14 and purifying and mixing and stirring an eluent such as an alkaline aqueous solution into a purified precipitate 28 separated by a centrifugal separator 12B as a second solid-liquid separation means. , An elution tank for eluting the target anionic surfactant from the precipitate 28. And what is shown by the code | symbol 20 is the separation liquid (anionic surfactant aqueous solution) isolate | separated by the centrifuge 12C which is a 3rd solid-liquid separation means from the sludge dispersion liquid containing the alkaline surfactant eluted in the elution tank 18. ) And a container for receiving the separated precipitate (sludge) 31 generated during the recovery of the anionic surfactant.

  Embodiments of an anionic surfactant recovery method and recovery apparatus according to the present invention will be described below with reference to the drawings. In addition, the measured value in an Example was measured with the following method.

Anionic surfactant concentration: Determined by Epton method. The anionic surfactant concentration in the precipitate was measured by adding sulfuric acid to sludge as a pretreatment to adjust the pH to 1, and filtering through filter paper No. 5C (manufactured by Toyo Roshi Kaisha, Ltd.) at a liquid temperature of 40 ° C. The concentration of the anionic surfactant in the liquid was measured and determined.
Petroleum ether soluble content: Measured according to JIS K 3362.
Ethanol soluble matter: Measured according to JIS K 3362.
pH: Measured using a glass electrode type hydrogen ion concentration indicator Model HM-21 (Toa DKK Corporation).
Conductivity: Measured using a conductivity meter ES-51 (manufactured by Horiba, Ltd.).

  It is obtained by emulsion polymerization using monomers acrylonitrile, vinyl chloride and sodium styrenesulfonate as main raw materials, using a redox catalyst consisting of ammonium persulfate, ferrous sulfate, sulfur dioxide and sodium hydrogen sulfite and using sodium dodecyl sulfate as an emulsifier. The latex was salted out with sodium chloride to separate and recover the polymer, and the polymer was washed with water. The waste water from which the latex was salted out to separate the polymer and the water drained from the polymer that was separated and recovered after salting were collected together, the pH was preliminarily adjusted to 10, and the raw water as an aqueous solution containing an anionic surfactant It was. Incidentally, this raw water contained 750 ppm of sodium dodecyl sulfate.

  From this raw water, sodium dodecyl sulfate was recovered based on the recovery flow shown in FIG. First, in a flocculation reaction tank 5 equipped with a stirrer 6A, an aluminum chloride-based flocculant 3 (trade name; PAC, manufactured by Asada Chemical Industry Co., Ltd.) is added to raw water 1 and mixed so as to be 130 ppm relative to the raw water in terms of aluminum. Further, sodium hydroxide 2 was added and mixed to adjust the pH to 7, and then an anionic polymer 4 composed of an acrylamide polymer (trade name; Cliff Rock PA-331, manufactured by Kurita Kogyo Co., Ltd.) was added to the raw water. Flock was formed by adding and mixing to 2 ppm. This treated water 21 was sent to the solid-liquid separation tank 7 and separated into a supernatant 23 and a sedimented sediment 22. The supernatant liquid 23 was collected in the stock container 11 and the precipitate 9,600 L was transferred to the acid treatment tank 8 equipped with the stirrer 6B and the pH meter 10A. Incidentally, when this precipitate 22 was sampled and the sodium dodecyl sulfate concentration was measured, it was 8,000 ppm. In the acid treatment tank 8, the dispersion liquid 24 adjusted to pH 3.4 by adding hydrochloric acid 9 to the precipitate 22 was dispersed and the decanter-type centrifuge 12A (Z1LLCE-V-BS2 type, Tanabe) at 1,500 L / Hr. Solid-liquid separation was performed at 4,400 rpm (centrifugal effect 2,500) using Wiltec Co., Ltd. The obtained separated precipitate 25 had a sodium dodecyl sulfate concentration of 10% and a yield of 760 kg. The acid-treated separation liquid 26 is recovered in a container 35, and the entire amount of the separated precipitate 25 is transferred to a purification tank 14 equipped with a stirrer 6C, and deionized water 13 is added to the mixture and stirred and washed with water. The solid content was separated with a decanter centrifuge 12B of the same type as that of 12A with a centrifugal effect 2500 under the same conditions as described above. The separation liquid 29 is recovered in the stock container 11, and the water-washed precipitate 28a is returned to the purification tank 14, and deionized water is added again until the conductivity of the separation liquid 29 becomes 20 mS / m or less. Stirring and washing operations were repeated. When the conductivity of the separation liquid 29 decreased to 20 mS / m, the recovered water-washed precipitate 28a was transferred as a purified precipitate 28 to an elution tank 18 equipped with a stirrer 6D, a pH meter 10B, and a heater 17A. The purified precipitate 28 at this time had a sodium dodecyl sulfate concentration of 24% and a yield of 310 kg. Deionized water 13 was added to the elution tank 18, sodium hydroxide 2 was further added to adjust the pH to 10 to 620 L, and the mixture was heated to 45 ° C. with a heater 17A and stirred and dispersed. Next, the dispersion 30 is separated into solids by a decanter centrifuge 12C of the same type as described above and the centrifugal effect 2500 under the same conditions as described above, and the separated sediment (sludge) 31 is recovered in the separated sediment receiving container 19. The separation liquid 32 was recovered in a separation liquid receiving container (tank) 20. The amount of the collected separation liquid 32 (anionic surfactant-containing aqueous solution) was 390 L. The concentration of sodium dodecyl sulfate after the sulfuric acid 15 was adjusted to pH 7 by adding sulfuric acid 15 to the recovered separated liquid was 13%. Therefore, the anionic surfactant was recovered in a state of being concentrated about 170 times the concentration of the anionic surfactant in the raw water 1. The recovered liquid containing sodium dodecyl sulfate has a petroleum ether soluble content of 0.25% and an alcohol insoluble content of 0.40%, and the chloride ion determined by capillary electrophoresis is 100 ppm or less. The sulfate ion content was 400 ppm. In the measurement method by capillary electrophoresis, the lower limit of quantification is 100 ppm for each. Furthermore, according to dry ashing-ICP emission analysis, the aluminum content was 120 ppm and the iron content was 0.3 ppm. The lower limit of quantification at this time by dry ashing-ICP emission analysis is 0.1 ppm for each.

  Using the sodium dodecyl sulfate-containing separation liquid recovered as described above, emulsion polymerization of a monomer mixture consisting of acrylonitrile, vinyl chloride and sodium styrenesulfonate was carried out for copolymerization. Copolymer obtained by emulsion polymerization, appearance of copolymer latex, copolymer composition ratio, ηsp indicating one of the indicators of polymerization degree, copolymer resin whiteness, acetone solubility of copolymer and solution There was no substantial difference in quality such as viscosity, and the possibility of reuse was confirmed.

  Based on the flow of the anionic surfactant recovery method shown in FIG. 3, the anionic surfactant was recovered. In the flow shown in FIG. 3, in the flow of Example 1 shown in FIG. 2, in addition to the separated sediment receiving container 19, the dispersion liquid 30 in the elution tank 18 is received as the precipitate 31 separated by the centrifuge 12 </ b> C. In addition, a re-elution tank 33 equipped with a stirrer 6E, a pH meter 10C and a heater 17B is provided. Further, as the fourth solid-liquid separation means for recovering the anionic surfactant by solid-liquid separation of the sludge dispersion 34 containing the anionic surfactant eluted in the re-elution tank 33, the third solid-liquid separation means is used. A decanter type centrifuge 12C, which is a separation means, is used.

  Each process is performed under the same conditions as in Example 1, and an anionic polymer 4 composed of an aluminum chloride-based flocculant 3, sodium hydroxide 2 and an acrylamide derivative is added to and mixed with raw water 1 in a flocculation reaction tank 5 to form a floc. After the treatment, the precipitate 22 is agglomerated and precipitated in the solid-liquid separation tank 7, and the precipitated precipitate 22 is acid-treated in the acid treatment tank 8, and then purified in the purification tank 14, and the dispersion 30 prepared in the elution tank 18 is centrifuged 12C. 280 kg of the precipitate 31 obtained by centrifugal separation is put into a re-elution tank 33 shown in FIG. 3, and deionized water 13 is added to make 480 L, and the mixture is heated to 50 ° C. with a heater 17B, and stirred and dispersed. went. This dispersion liquid 34 was sent to the decanter type centrifugal separator 12C, and the solid content was separated by the same centrifugal effect 2500 as described above to obtain 260 L of the separated liquid 16. The concentration of sodium dodecyl sulfate in the separated liquid 16 was measured and found to be 6.7%.

  Next, each process is performed under the same conditions as in Example 1. In an agglomeration reaction tank 5, an anionic polymer 4 composed of an aluminum chloride-based flocculant 3, sodium hydroxide 2 and an acrylamide derivative is added to and mixed with raw water 1. The flocs are formed and processed, and are agglomerated and precipitated in the solid-liquid separation tank 7. The precipitated precipitate 22 is acid-treated in the acid treatment tank 8 and then purified in the purification tank 14 to obtain 300 kg of the precipitate 28. In the elution tank 18, the entire amount of the separation liquid 16 was added, deionized water 13 was further added, and the pH was adjusted to 10 with sodium hydroxide 2 to prepare a precipitate dispersion 620L. This precipitate dispersion liquid 37 was sent to the decanter-type centrifuge 12C and subjected to solid-liquid separation with a centrifugal effect 2500 to obtain 380 L of the separated liquid 36. After adjusting this separated liquid 36 to pH 7 with sulfuric acid 15, the concentration of sodium dodecyl sulfate was measured and found to be 18%. This means that the concentration of sodium dodecyl sulfate in raw water 1 is approximately 240 times the concentration, and by using the separation liquid obtained by the re-elution treatment, a higher concentration sodium dodecyl sulfate aqueous solution is recovered. It was.

  According to the present invention, it becomes possible to recover the anionic surfactant in the waste water as a highly concentrated anionic surfactant-containing aqueous solution having a purity satisfying practicality. It can be used not only for reuse in the field used for the purpose but also for other purposes. In addition, as a result of the expected reuse of the recovered anionic surfactant, the amount of newly added anionic surfactant can be reduced and the amount of anionic surfactant in industrial wastewater can be reduced. It is also possible to use a branched alkyl group-containing anionic surfactant which has been refrained from use due to the difficulty of biological treatment. Furthermore, as a result of the reduction of industrial waste related to anionic surfactants, it can be expected to reduce the burden of biological treatment or chemical treatment of industrial wastewater treatment facilities and wastewater, and miniaturization of related facilities becomes possible. .

It is process explanatory drawing of the collection | recovery method of the anionic surfactant which concerns on this invention. It is a flowchart of the anionic surfactant collection method of Example 1 of this invention. It is a flowchart of the anionic surfactant collection method of Example 2 of this invention.

Explanation of symbols

1 Raw water (anionic surfactant-containing aqueous solution)
2 Sodium hydroxide 3 Aluminum-based flocculant 4 Anionic polymer 5 Aggregation reaction tank 6A-6E Stirrer 7 Solid-liquid separation tank 8 Acid treatment tank 9 Inorganic acid (hydrochloric acid)
10A to 10C pH meter 11 Stock container 12A to 12C Decanter centrifuge 13 Deionized water 14 Purification tank 15 Sulfuric acid 16 (derived from re-elution tank dispersion) Separation liquid 17A, B Heater 18 Elution tank 19 (Elution tank dispersion) Liquid-derived) Separated sediment receiving container 20 (Derived from elution tank dispersion) Separated liquid receiving container 21 (Aggregation reaction treatment) Treated water 22 Precipitate 23 Supernatant liquid 24 (Derived from acid treatment tank) Dispersion liquid 25 (Acid treatment tank dispersed) Liquid-derived) Separated precipitate 26 (Derived from acid treatment tank dispersion) Separated liquid 27 (Derived from purification tank) Precipitate dispersion 28 (Derived from purified tank dispersion) Purified precipitate 28a (Derived from purified tank dispersion) Washed precipitate 29 (Derived from refinery tank dispersion) Separation liquid 30 (Derived from elution tank) Dispersion liquid 31 (Derived from elution tank dispersion) Separated precipitate (sludge)
32 (Elution tank derived) Separation liquid 33 Re-elution tank 34 (Re-elution tank derived) Dispersion liquid 35 Acid-treated separation liquid container 36 Separation liquid derived from the elution tank dispersion using the separation liquid 16 as a part of the elution liquid 37 Elution tank dispersion using separation liquid 16 as part of eluent

Claims (11)

A method of recovering an anionic surfactant from an aqueous solution containing an anionic surfactant,
(1) A separation step of adding and mixing a coagulating precipitant to the aqueous solution to coagulate and precipitate the anionic surfactant in the aqueous solution, and separating and recovering the precipitate;
(2) a concentration step in which the separated and collected precipitate is subjected to an aqueous dispersion treatment in an acidic manner to increase the concentration of the anionic surfactant in the precipitate and to concentrate,
(3) a purification step of washing the concentrated precipitate with water;
(4) a recovery step of adding an eluent to the washed precipitate, mixing and stirring, and eluting and recovering the anionic surfactant in the eluent phase;
A method for recovering an anionic surfactant, comprising:   2. The method for recovering an anionic surfactant according to claim 1, wherein pH treatment with hydrochloric acid is performed in the acidic water dispersion treatment.   The method for recovering an anionic surfactant according to claim 1 or 2, wherein the coagulating precipitant is an aluminum coagulant.   After the purification step is concentrated by increasing the content of the anionic surfactant in the concentration step, the solid-liquid separated precipitate is deionized water until the conductivity of the wash water after washing becomes 100 mS / m or less. The method for recovering an anionic surfactant according to any one of claims 1 to 3, wherein the anionic surfactant is washed with water.   The method for recovering an anionic surfactant according to any one of claims 1 to 4, wherein an alkaline aqueous solution is used as an eluent in the recovery step.   In the recovery step, the anionic surfactant is eluted in the eluent phase, and after solid-liquid separation and recovery, the eluent is added to the precipitate, mixed and stirred, and the anionic surfactant is eluted in the eluent phase and recovered. The method for recovering an anionic surfactant according to any one of claims 1 to 5, further comprising a re-recovery step.   The separation liquid containing the anionic surfactant recovered by eluting the anionic surfactant from the precipitate in the re-recovery step is circulated to the recovery step, and the anionic surfactant is removed from the precipitate after washing in the purification step. The method for recovering an anionic surfactant according to claim 6, wherein the anionic surfactant is used as an eluent for eluting. An agglomeration reaction tank for aggregating and precipitating the anionic surfactant in the aqueous solution by adding and aggregating the aggregating precipitation agent to the aqueous solution containing the anionic surfactant;
A solid-liquid separation tank for separating the precipitate prepared in the aggregation reaction tank;
An acid treatment tank for adding an acid to the precipitate separated and recovered by the solid-liquid separation tank and increasing the content of the anionic surfactant in the precipitate by subjecting the precipitate to water dispersion treatment under acidity;
First solid-liquid separation means for solid-liquid separation of the aqueous dispersion treatment liquid;
A purification tank for washing the precipitate separated by the first solid-liquid separation means,
A second solid-liquid separation means for separating the precipitate washed with water in the purification tank and the washing water;
An elution tank for adding an eluent to the precipitate separated by the second solid-liquid separation means, mixing and stirring to form a sludge dispersion, and eluting an anionic surfactant in the eluent phase of the sludge dispersion;
A third solid-liquid separation means for solid-liquid separation of the sludge dispersion containing the anionic surfactant eluted in the elution tank and recovering the aqueous anionic surfactant solution;
An apparatus for recovering an anionic surfactant from an aqueous solution containing an anionic surfactant, comprising:   In the elution tank, the anionic surfactant is eluted in the eluent phase, and after adding the eluent to the precipitate after solid-liquid separation and recovery, the mixture is stirred to form a sludge dispersion and an anionic surfactant in the eluent phase. A re-elution tank for eluting the agent, and a fourth solid-liquid separation means for recovering the anionic surfactant by solid-liquid separation of the sludge dispersion containing the anionic surfactant eluted in the re-elution tank. The anionic surfactant recovery device according to claim 8.   The anion according to claim 9, wherein the anion surfactant aqueous solution recovered by solid-liquid separation by eluting the anionic surfactant from the precipitate in the re-elution tank is recirculated to the elution tank and used as an eluent. Surfactant recovery device. The anionic surfactant recovery apparatus according to claim 8 or 9, wherein a centrifuge is used as the first to third solid-liquid separation means.

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