JPH0549337B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to synthetic adsorbents. Non-polar or slightly polar cross-linked polymers with developed specific surface area and pore volume are used as synthetic adsorbents, and those based on styrene-divinylbenzene copolymer have a specific surface area of 900.
Some are known to reach m ² /g. For example, they are already manufactured under trademarks such as Diaion HP10, 20, 30, 40, 50 (trademark of Mitsubishi Chemical Industries, Ltd.) and Amberlite XAD2, 4 (registered trademark of Rohm & Haas).
It is commercially available. The adsorption of substances to these synthetic adsorbents is thought to be mainly physical adsorption based on van der Waals forces on the pore surface inside the adsorbent, and therefore, unlike activated carbon, highly polar substances such as methanol, ethanol, and acetone By washing the adsorbent with an organic solvent, it is possible to elute the adsorbed substance from the adsorbent.
In addition, using an alkali as a regenerant for inorganic adsorbents such as zeolite will cause the adsorbent to dissolve, making it difficult to use alkalis, but synthetic adsorbents that are cross-linked polymers are resistant to any solvent. Since it is insoluble, elution with alkali or the like is also possible. Utilizing these properties, synthetic adsorbents are widely used for adsorption purification of pharmaceuticals, fragrances and natural pigments, decolorization of pulp wastewater, adsorption removal of COD components in general wastewater, etc. . However, most of the known conventional synthetic adsorbents are styrene-divinylbenzene (with about 20% ethylvinylbenzene as an impurity).
It is based on a crosslinked polymer (containing ~60%), and its pores, with radius ranging from several angstroms to several thousand angstroms, exist within each particle. As a result of a detailed study of the adsorption behavior of such synthetic adsorbents, the present inventors found that ordinary useful organic compounds, more specifically useful organic compounds with a molecular weight of 2000 or less that have a hydrophobic group and a hydrophilic group in one molecule, such as cephalosporin C. The radius of the pores required to adsorb penicillin G, etc. from water to the synthetic adsorbent is at most several tens of pores.
~300 Å, particularly preferably 20 to 200 Å, and pores of 300 Å or more, particularly 500 Å or more, cause unnecessary irreversible adsorption of large organic molecules with a molecular weight of 10,000 or more, such as proteins and humic acids, and may cause synthetic adsorbents. It was found that there is a large possibility that this is causing organic pollution. It is known that such organic contamination causes clogging of pores after long-term use, which in turn reduces the adsorption capacity of target compounds. Based on this knowledge, the present inventors have intensively studied methods for producing a synthetic adsorbent having few or no pores with a radius of 300 Å or more, and have arrived at the present invention. That is, the gist of the present invention is such that the pore radius occupied by pores with a radius of 300 Å or more is less than 10% of the total pore volume, and the pore volume occupied by pores with a radius of 200 Å or less is 70% or more. A synthetic adsorbent for adsorbing an organic compound with a molecular weight of 2000 or less and having a hydrophobic group and a hydrophilic group in the molecule, which is made of a spherical porous aromatic crosslinked copolymer characterized by having large pores, and a method for producing the same. . The present invention will be explained in detail below. The synthetic adsorbent of the present invention is synthesized by a specific method. That is, a mixture containing a specific proportion of monomers consisting of (a) an aromatic polyvinyl monomer as a crosslinking agent, (b) an aromatic monovinyl monomer, and (c) an aliphatic vinyl monomer represented by the general formula (). It is produced by suspension polymerization in water in the presence of a good solvent and a polymerization initiator that will cause the resulting copolymer to swell well. Divinylbenzene, trivinylbenzene, divinyltoluene, etc. are useful as the aromatic polyvinyl compound (a). Aromatic monovinyl monomers (b) include styrene, ethylvinylbenzene, vinyltriene,
Vinylnaphthalene and the like are useful. The aliphatic vinyl monomer (c) is selected from vinyl monomers represented by the general formula (). General formula () However, R=H, CH ₃ X=COOR', CN R'=H, (-CH ₂ (- _o H (however, n is 1 to 4) _{−CH2CH2OH _} (However, m is 2 to 4) Specifically, for example, monovinyl monomers such as acrylonitrile, methacrylonitrile, methacrylic acid, methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate, n-butyl methacrylate, ethylene glycol dimethacrylate, trimethacrylate, etc. Methylone propane trimethacrylate and the like are useful. Synthetic adsorbents adsorb substances to be adsorbed from water through physical adsorption on their pore surfaces, so the specific surface area should preferably be large, at least 300 m ² /
A specific surface area of g or more is preferred. The composition of the vinyl monomer is important in order to have such a specific surface area and pores with a specific radius aimed at by the present invention. That is, the amount of the aromatic polyvinyl compound (a) is at least 40% by weight or more, preferably 45 to 80% by weight, based on the total vinyl monomers. The main aromatic monovinyl monomer (b) is ethylvinylbenzene, which is contained as an impurity in divinylbenzene.Other examples include styrene, but the amount thereof is 10 to 54% by weight based on the total vinyl monomer. %. The amount of the aliphatic vinyl monomer (c) is important because it controls the pore diameter, and is 1 to 10% by weight based on the total vinyl monomer in order to provide the pore radius targeted by the present invention. The pores of the synthetic adsorbent referred to in the present invention are generated when minute particles of an insoluble crosslinked copolymer formed in polymer droplets during the polymerization process aggregate, and the gaps between them remain as pores. it is conceivable that. Therefore, the factors that determine the pore size include the content of the aromatic polyvinyl monomer that is the crosslinking agent mentioned above, the content of the aromatic monovinyl monomer and aliphatic monovinyl monomer that determines the compatibility of the polymer, and the polymer droplet content. The presence of a polymerizable inert medium is necessary to create an effective interstitial space. Such a medium determines the agglomeration stage of the previously mentioned insoluble microparticles.
Therefore, the selection of such a medium is very important from the viewpoint of controlling the pore size, and in order to produce the synthetic adsorbent of the present invention, the medium must be a solvent that can favorably swell the produced copolymer. limited to. Solvents particularly useful in the present invention are limited to aromatic hydrocarbons such as toluene, benzene, and ethylbenzene. Other solvents that do not swell the copolymer, such as methyl isobutyl carbinol and isooctane, are not preferred because they provide too large a pore size. Mixtures of these solvents and the aromatic hydrocarbons are also not preferred for the same reason. The amount of such aromatic hydrocarbons is from 70 to 150% by weight, preferably from 80 to 150% by weight, based on the total vinyl monomers. If it is less than 70%, the pore volume and specific surface area are small, making it unsuitable for use as a synthetic adsorbent. 150%
This is not preferable because it gives rise to many pores with a radius of 300 Å or more. In the present invention, the monomer mixture is polymerized by known suspension polymerization techniques. Specifically, 0.1 to 5% by weight of a polymerization initiator is added to the monomer mixture, and polymerization is carried out for 4 to 20 hours while stirring at 60 to 90°C in water containing a suspension stabilizer and an auxiliary agent. It is done by. As the polymerization initiator, known radical polymerization initiators such as benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, and azobisisovaleronitrile can be used. Suspension stabilizers include carboxymethyl cellulose sodium salt, sodium polyacrylate, starch,
Known materials such as polyvinyl alcohol can be used. Examples of the auxiliary agent include water-soluble inorganic salts to prevent the monomer from dissolving in water and finely divided water-insoluble inorganic salts to increase the suspension stabilizing effect, and known ones can be used. After polymerization, residual monomers and inert organic solvents are removed from the obtained spherical porous copolymer by conventional treatment methods, such as washing with water followed by organic solvent washing or azeotroping with water. Thus, the specific surface area targeted by the present invention is 300
m ² /g or more, the pore volume occupied by pores with a pore radius of 300 Å or more is less than 10% of the total pore volume, and the pore volume occupied by pores with a pore radius of 200 Å or less is 70% of the total pore volume. % or more of porous spherical aromatic crosslinked copolymer is obtained. The crosslinked copolymer of the present invention well adsorbs organic compounds having a molecular weight of 2000 or less and having a hydrophobic group and a hydrophilic group in the molecule, while hardly adsorbing large organic compounds such as lignin. Therefore, it is a synthetic adsorbent suitable for adsorbing and separating useful organic compounds such as antibiotics from water. In the present invention, the total pore volume was measured by measuring the water content of the synthetic adsorbent, and the volume of pores with a radius of 300 Å or less was measured by a gas adsorption method. (Reference: "Catalyst Engineering Course Vol. 4, Catalyst Basic Measurement Methods," p. 73, edited by Yukio Yoneda, published by Chijinshokan in 1962) The specific measurement method is as follows. 80 g of vinyl monomer mixture according to the method of the invention
After polymerization, the spherical copolymer was separated, thoroughly washed with water, and then transferred to a column and washed by passing acetone (5) and demineralized water (5) through each column for 2 hours. After measuring the total volume of this resin, accurately weigh out 10 ml of resin and measure 20 cm in diameter.
The adhering moisture was removed by placing the sample in a centrifuge with a basket and centrifuging at 3,000 rpm for 5 minutes. Wet weight PW of the resin containing water in this pore
After measuring, under a pressure of 10mmHg until a constant weight is reached.
It was dried at 80°C for 8 hours and the dry weight Pd was measured.
Furthermore, using this dried resin, the specific surface area and pore physical properties were measured by gas adsorption method. The moisture content, total pore volume, and degree of swelling were calculated as follows. Total pore volume V _T (ml/g) = P _W - P _d / P _W - P _d Moisture (%) = P _W - P _d / P _W ×100 Swelling degree (ml/g) = 10/Pd or less The present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Synthesis Example of Synthetic Adsorbent-1 70.5g of divinylbenzene with a purity of 56.7% (others are ethylvinylbenzene), 4g of methyl methacrylate,
5.5g styrene, 0.8g bezoyl peroxide, toluene
A homogeneous mixed solution consisting of 80 g was added to 700 ml of demineralized water containing 0.4 g of polyvinyl alcohol, and polymerization was carried out by heating at 80° C. for 8 hours under nitrogen while stirring to obtain a spherical copolymer. Examples 2 to 7, 9 to 11 Spherical crosslinked copolymers were obtained in the same manner as in Example 1 except that the binding monomers and organic solvents shown in Table 1 were used.

[Table] Example 8 4 g of methacrylic acid was used instead of methyl methacrylate in Example-1, and 56 g was added to the polymerization bath.
A spherical crosslinked copolymer was obtained in the same manner as in Example 1, except that 100% of common salt was added. Comparative Examples 1 to 5 Spherical crosslinked copolymers were obtained in the same manner as in Example 1 using the respective components shown in Table 2 below.

[Table] The specific surface area, total pore volume, pore distribution, etc. of the resins obtained in the above Examples and Comparative Examples were measured according to the methods described above. Furthermore, the polymerization yield was calculated from the total volume of the polymerized resin. The results are shown in Tables 3 and 4.

【table】

[Table] * Evaluation of adsorption performance of commercially available resins (1) Example of adsorption of low molecular weight useful compounds Comparison of adsorption performance of cephalosporin C (molecular weight 414) 2000 ppm solution of cephalosporin C (with hydrochloric acid)
Add 5.00ml of synthetic adsorbent to 100ml (adjusted to pH 2.5),
After incubating at 25℃ for 5 hours, collect the upper orange liquid and make a 260mμ
The absorbance was measured. The concentration of cephalosporin (A) in the orange solution was determined from a calibration curve that was separately prepared by varying the concentration of cephalosporin C and measuring the absorbance. In the same manner, the cephalosporin C concentration (AO) in the cephalosporin C 2000 ppm solution used as a data was also accurately determined. From these values, the adsorption amount g of cefrosporin C per resin was determined using the following formula. Cephalosporin C adsorption amount (g/) = (AO-A) x 0.1/5.0 Since the equilibrium concentration differs in each case, this value was determined from an isothermal adsorption diagram separately created by changing the concentration of Cephalosporin C at 2000ppm
The equilibrium adsorption amount was determined. The results are summarized in Table 5. In addition, a 1 cm quartz cell was used for absorbance measurement, and a double beam spectrophotometer Model 200-20 (Hitachi, Ltd.) was used.

【table】

[Table] (2) Example of non-adsorption of high molecular weight wastes Adsorption experiment of lignin (estimated average molecular weight 20,000 to 100,000) Aqueous solution containing 100 ppm lignin (pH=
10.0) Add 5.00 ml of the adsorbent contained in 250 ml, and after stirring at room temperature for 12 hours, the upper orange solution was taken and the absorbance A at 350 mμ was measured. Separately, the absorbance (AO) of the stock solution was determined. From these values, the adsorption rate (%) of lignin was determined using the following formula. The results are shown in Table 6. Lignin adsorption amount (%) = (AO-A/AO) x 100

【table】

【table】

Claims (1)

[Claims] 1. The pore volume occupied by pores with a pore radius of 300 Å or more is less than 10% of the total pore volume, and the pore volume occupied by pores with a pore radius of 200 Å or less is 70% of the total pore volume. % or more and a specific surface area of 300 m ² /g or more, an organic compound with a molecular weight of 2000 or less and having a hydrophobic group and a hydrophilic group in the molecule. Synthetic adsorbent for adsorption. 2 (a) aromatic polyvinyl monomer, (b) aromatic monovinyl monomer, and (c) aliphatic vinyl monomer represented by the following formula () (In the formula, R represents a hydrogen atom or a methyl group, and
represents a COOP' group or a CN group. R' is a hydrogen atom, (-CH ₂ (- _o H group [however, n is 1 to 4], -CH _2
CH2OH group, base or (a) = 40 to 80, (b) = 10 to 54, and (c)
= 1 to 10, an aromatic hydrocarbon which is a good solvent for the copolymer to be produced is 70 to 10.
The pore volume occupied by pores with a pore radius of 300 Å or more is 10% of the total pore volume, which is characterized by carrying out suspension polymerization in water in the presence of 150% by weight (based on the total vinyl monomer) and a polymerization initiator. The pore radius is less than 200
The pore volume occupied by pores smaller than Å is 70% of the total pore volume.
It has pores with a specific surface area of 300 m ² /g or more.
It is a porous spherical aromatic crosslinked copolymer with a molecular weight of 2000 and has a hydrophobic group and a hydrophilic group in the molecule.
Method 3 for producing a synthetic adsorbent that adsorbs the following organic compounds In the method for producing a synthetic adsorbent according to claim 2, the composition of the vinyl monomer is (a) = 45% by weight based on the total vinyl monomer. ~80, (b)
= 10 to 54, (c) = 1 to 10, and the aromatic hydrocarbon that is a good solvent for the copolymer to be produced is 80 to 150.
% by weight (based on total vinyl monomer).