JP2005082800A - Method for producing biodegradable polymer gel without addition of crosslinking agent and method for removing metal from waste liquid using the product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a biodegradable polymer gel that does not affect the environment as a gel for adsorbing and removing harmful metal polyvalent ions in an aqueous solution such as waste water without using a harmful crosslinking agent. And a method for removing a metal in a waste liquid using a biodegradable polymer gel obtained by the production method thereof.
SOLUTION: A carboxymethyl cellulose sodium (CMCNa) solution having a concentration of 10% or more is irradiated with γ rays of 20 kGy or more to crosslink and gel. The biodegradable polymer gel obtained by this production method is immersed in a waste liquid containing metal ions to adsorb and remove the metal in the waste liquid.
[Selection] Figure 3

Description

  The present invention relates to a method for producing a biodegradable polymer gel without using a cross-linking agent having a lot of harmful substances, and a metal polyvalent ion in a waste liquid using the biodegradable polymer gel obtained by the production method. It is related with the method of adsorbing and removing.

  Metals such as Cr, Mn, Cu, and Fe in waste liquid discharged from factories and the like are generally treated as hydroxides. Most of these metal hydroxides are disposed of in landfills. However, as it is, there is a concern of environmental pollution due to movement into the environment.

On the other hand, it is known that a metal or the like in a liquid is adsorbed and fixed by a gel. For example, using an adsorbent modified with polynuclear metal oxide hydroxide, inorganic phosphate can be selectively adsorbed and removed from protein-containing body fluids such as whole blood, plasma, intestinal fluid and dialysate. It is known (see, for example, Patent Document 1).
JP 7-75669 A

  The gel is a dispersion system composed of two components of a solid (gel-forming substance) and a liquid such as water and organic matter, and the dispersion element does not move macroscopically and is a non-flowable semi-solid as a whole system. The solid portion of the gel's basic structure is often a crosslinked polymer. Examples of the polymer include sodium polyacrylate, sodium alginate, carboxymethyl cellulose Na (CMCNa) aqueous solution, and the like. The product form is mostly in powder form. However, there are many harmful substances in the crosslinking agent added when producing the gel, and there are many problems in treatment after use. The present invention produces a biodegradable polymer gel that does not affect the environment as a gel for adsorbing and removing harmful heavy metal polyvalent ions in an aqueous solution such as wastewater without using a harmful crosslinking agent. It is an object of the present invention to provide a method and a method for removing metal in waste liquid using the biodegradable polymer gel.

  In order to solve the above-mentioned problems, the invention according to claim 1 is the addition of a cross-linking agent that crosslinks and gels by irradiating γ-rays of 20 kGy or more to an aqueous solution of sodium carboxymethylcellulose (CMCNa) having a concentration of 10% or more. This is a method for producing a biodegradable polymer gel.

  The invention according to claim 2 adsorbs and removes the metal in the waste liquid by immersing the biodegradable polymer gel without addition of the crosslinking agent obtained by the production method according to claim 1 in the waste liquid containing metal ions. This is a method for removing metal from the waste liquid.

  According to the present invention, it is possible to provide an inexpensive biodegradable polymer gel that does not affect the environment without using a cross-linking agent that contains many harmful substances.

  According to the second aspect of the present invention, harmful heavy metal multivalent ions in an aqueous solution such as waste water can be adsorbed and removed to contribute to environmental purification.

  In order to solve the technical problems in the invention, the inventors have a biodegradable polymer that is inexpensive, has an ionic molecular chain in the gel, and is easy to adsorb and remove (take out) transition metal polyvalent ions. As a result of investigations to obtain a gel, the present inventors succeeded in obtaining a biodegradable polymer gel by irradiating an aqueous solution of sodium carboxymethylcellulose (CMCNa) with γ-ray irradiation and crosslinking.

  The gel is a swollen body composed of two components of a solvent such as water / organic solvent and a polymer having a three-dimensional network structure insoluble in the solvent. It is classified into hydrogel (hydrogel) and organogel (lipogel) depending on whether the liquid swelling the three-dimensional network structure is water or organic matter. The formation of the three-dimensional network structure may be performed by chemical bonding or by utilizing intermolecular bonding or polymer entanglement.

  Formation of a three-dimensional network structure by intermolecular bonds utilizes hydrogen bonds, electrostatic bonds, and hydrophobic bonds between polymers. When a method for forming a three-dimensional network structure using these bonds or polymer entanglements is used, generally, sol-gel transition is likely to occur due to changes in heat, solution type, ionic strength, pH, etc., and stability is lacking. Therefore, in the present invention, a method of forming by chemical bonding capable of forming a strong and stable three-dimensional network structure is adopted.

  When forming a three-dimensional network structure by chemical bonding, energy such as heat, light, radiation, plasma, or the like can be used. The formation of a three-dimensional network structure by chemical bonding includes a method of crosslinking simultaneously with polymerization and a method of first forming a linear polymer and then crosslinking by a chemical reaction. The method of crosslinking simultaneously with the polymerization generally has a difficulty that it is difficult to obtain a uniform network structure, but has an advantage that a wide variety of monomer types can be targeted. On the other hand, the method of forming a linear polymer first and then crosslinking has the advantage that a uniform three-dimensional network structure can be formed by narrowing down the monomer species and degree of polymerization. Thus, in the present invention, the monomer species is specified to be inexpensive and biodegradable sodium carboxymethyl cellulose (CMCNa), and a method for forming a three-dimensional network structure in which the polymer chain is crosslinked later is employed.

  As a method of first forming a linear polymer and then crosslinking, there is a method of crosslinking by (a) chemical reaction (b) radiation irradiation (c) light (d) plasma irradiation. (A) The method of crosslinking by a chemical reaction is generally a method for obtaining a polymer having a hydroxyl group such as cellulose or PVA (polyvinyl alcohol) by using a crosslinking agent such as an N-methylol compound, a dicarboxylic acid, or a bisepoxide. is there. (B) According to the crosslinking method by irradiation, a gel having a three-dimensional network structure can be obtained without using a crosslinking agent having a lot of harmful substances, as will be described later. (C) The crosslinking method using light is used for the purpose of image formation and photocuring. It is suitable for obtaining an organogel having a high degree of crosslinking and low swelling. (D) The crosslinking method by plasma irradiation is performed by bringing polyethylene, polyfluoroethylene, nylon, polyvinyl fluoride, or the like into contact with an inert gas such as helium or neon excited using high-frequency discharge. Are cross-linked. In general, it is suitable for obtaining a hard gel with low solvent affinity.

  In the present invention, in order to obtain a gel having a three-dimensional network structure without using a cross-linking agent containing many harmful substances, a method is used in which a polymer straight chain is irradiated with γ rays for crosslinking. The crosslinking method by radiation irradiation is a crosslinking method used for radial tires, cables, electric wires, foamed plastics, and the like. This crosslinking method by radiation irradiation is also used for gel formation of polyethylene, styrene, polyacrylate, polyvinyl alcohol and the like.

  FIG. 1 shows the relationship between the gel fraction of a PVDF (polyvinyl denfluoride) film irradiated with γ rays and the irradiation γ dose. As is apparent from FIG. 1, the gel fraction of the film irradiated with γ-rays in a vacuum increases with almost the same tendency as the γ dose increases regardless of the film thickness.

  On the other hand, progress in research on gels is remarkable, and many hydrogels with new functions and excellent functions have appeared. However, research on hydrogels that harmonize with the environment has not progressed much. In order to maintain a favorable environment, plastic materials are considered to be recyclable material designs and use of biodegradable materials is difficult to collect. Such research and results are also desired for hydrogels.

  According to the method for producing a biodegradable polymer gel without a cross-linking agent and the method for removing metal from waste water using the product of the present invention, a desired metal can be selectively adsorbed and fixed using a chelating reagent. Is possible. Recovered metals can be separated by amortization without detrimental generation of dioxins due to the absence of chlorine in CMC molecules for storage or reuse in place. Can also be separated.

Preparation of gel Reagents used
carboxymethyl cellulose sodium salt: manufactured by Wako Pure Chemical Industries, Ltd. CuCl ₂ · 2H ₂ O: 99.0%: manufactured by Katayama Chemical Industry Co., Ltd. (1) A predetermined amount of sodium carboxymethyl cellulose (CMCNa) is mixed with pure water, A CMCNa aqueous solution having a concentration of 2% by mass, 2% by mass, 3% by mass, 4% by mass, 6% by mass, 7% by mass, 8% by mass, 10% by mass, 15% by mass, and 20% by mass, A total of 440 g for 40 g was produced. This CMCNa aqueous solution was put into a container with a lid made of polypropylene, and ⁶⁰ Co-γ-ray irradiation (20 kGy) was performed at the Japan Isotope Association Koka Laboratory.
(2) A predetermined amount of sodium carboxymethylcellulose (CMCNa) is mixed with pure water at 90 ° C., and 40 g of 10%, 12%, 15%, and 20% strength by weight CMCNa aqueous solution is added in each of 16 pieces, for a total of 16 This CMCNa aqueous solution was put into a container with a lid made of polypropylene and subjected to ⁶⁰ Co-γ radiation at doses of 20 kGy, 30 kGy, 40 kGy, and 50 kGy for each concentration level at the Japan Isotope Association Koka Laboratory. It was.

Adsorption / fixation of metal A certain amount of the gel prepared in this manner was taken and immersed in a 10 mM aqueous solution of Cu (II) (100 ml) prepared from a reagent for 120 hours to remove the gel sufficiently adsorbing the metal, and the remaining aqueous solution The Cu (II) concentration in the sample was quantified by atomic absorption spectrometry, and the amount of metal adsorbed on the gel (Cu (II)) was determined by calculation.

Regarding the preparation of the gel, in the sample having a sodium carboxymethyl cellulose (CMCNa) concentration of 1% by mass to 6% by mass, no particular change was observed as compared to before ⁶⁰ Co-γ irradiation. In the sample having a CMCNa concentration of 7% by mass to 8% by mass, a fluffy product was generated inside after irradiation with ⁶⁰ Co-γ rays, but it remained liquid as a whole.

For CMCNa concentration of 10% by mass to 20% ^samples, 60 Co-gamma ray prior to irradiation has been a liquid body of very high ^viscosity, 60 Co-gamma ray after the irradiation has been generated inside the mass It was. From these facts, it is considered that a concentration region having a CMCNa concentration of about 10% by mass to 20% by mass is appropriate for obtaining a gel from a CMCNa aqueous solution by γ-ray irradiation.

On the other hand, a predetermined amount of CMCNa was mixed with pure water at 90 ° C., and 40 g of 10%, 12%, 15%, and 20% by weight CMCNa aqueous solutions were prepared in total, 16 pieces each. An aqueous solution was put in a container with a lid made of polypropylene, and a gel obtained by performing ⁶⁰ Co-γ irradiation at a dose of 20 kGy, 30 kGy, 40 kGy, and 50 kGy for each concentration level at the Japan Society of Isotopes Koka Laboratory. A part was cut out and dried at a temperature of 100 ° C.

FIG. 2 shows the results of measuring the mass of the gel after drying and calculating the ratio of the skeletal component to the entire gel from the mass of the gel before drying. As is clear from FIG. 2, when the CMCNa concentration in the CMCNa aqueous solution is shifted to a high level, the ratio of the skeletal component in the entire gel increases, and the ratio of the skeletal component increases as the ⁶⁰ Co-γ-ray irradiation dose increases. ing. On the other hand, when the produced gel was cut out and swelled by immersing it in pure water, the higher the CMCNa concentration, the higher the ⁶⁰ Co-γ-ray irradiation dose, and the higher the water absorption.

  A certain amount of the gel obtained in the above example was immersed in an aqueous Cu (II) solution for 120 hours to sufficiently adsorb Cu (II) to the gel. Thereafter, the gel was removed from the Cu (II) aqueous solution, and the amount of metal adsorbed on the gel was calculated based on the volume of the remaining aqueous solution and the Cu (II) concentration. The result is shown in FIG.

  As is clear from FIG. 3, the amount of metal adsorbed on the gel increases as the CMCNa concentration increases and the amount of γ-irradiated increases. This indicates that the higher the CMCNa concentration, the greater the portion of the network that takes in the metal in the gel, and the higher the probability that the gel surrounds the metal ions and the ionic bond between the gel skeleton component cellulose and metal ions. . In addition, it is considered that the amount of adsorbed metal increases because the degree of crosslinking increases as the irradiation γ dose increases, and the proportion of the meshes taking a more complicated three-dimensional network structure increases.

A graph showing the relationship between the amount of γ-ray irradiation and the gelation rate of PVDF film Graph showing the relationship between the γ-ray irradiation intensity (kGy) to the CMCNa aqueous solution and the ratio of the gel skeleton component, with the CMCNa concentration as a parameter A graph showing the relationship between the γ-ray irradiation intensity (kGy) to the CMCNa aqueous solution and the amount of adsorbed Cu (II) (g), with the CMCNa concentration as a parameter

Claims (2)

Concentration: A method for producing a biodegradable polymer gel without addition of a crosslinking agent, comprising irradiating a carboxymethyl cellulose sodium (CMCNa) aqueous solution having a concentration of 10% or more with γ rays of 20 kGy or more to cause crosslinking and gelation. The biodegradable polymer gel without a crosslinking agent obtained by the production method according to claim 1 is immersed in a waste liquid containing metal ions to adsorb and remove the metal in the waste liquid. Method for removing metal from waste liquid.

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