JPS61157344A - Manufacture of metal absorbing material - Google Patents

Abstract

PURPOSE:To facilitate graft polymerization, by reacting a graft polymer, wherein a polymerizable monomer was grafted to the surface or surface layer of a base material, with hydroxylamine and converting the nitrile group in a graft chain to an amidoxim group. CONSTITUTION:After surface treatment due to low temp. plasma treatment was preliminarily applied to a base material comprising polyethylene, a polymer containing a nitrile group is reached with hydroxylamine. The reaction product is contacted with one or more of a polymerizable monomer capable of altering a nitrile group to an amidoxim group to prepare a graft polymer wherein the polymerizable monomer is grafted to the surface or surface layer of the base material. Subsequently, this graft polymer is reacted with hydroxylamine to convert the nitrile group in a graft chain to an amidoxim group to obtain a metal adsorbing material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an adsorbent having an amidoxime group that selectively adsorbs metals, particularly uranium, dissolved in trace amounts in an aqueous solution.

In the separation and recovery of trace amounts of heavy metals present in aqueous solutions, such as purification and reuse of industrial wastewater or recovery of useful substances, adsorption separation methods using compounds that form complexes with the metal ions are applied. For example, JP-A-5
3-126088 describes that a resin having an amidoxime group exhibits good adsorption ability as an adsorbent for uranium dissolved in seawater.

However, in this adsorbent, the distribution of hydrophilic amidoxime groups extends to the center of the base resin, which causes the entire resin to swell, resulting in problems such as a decrease in mechanical strength and insufficient durability for repeated adsorption and desorption. It had been.

As a method to improve these problems, for example, Japanese Patent Application Laid-Open No. 58-20553 proposes a uranium adsorbent in which amidoxime groups are localized on the surface or surface layer of a base material by a radiation grafting method, and a method for producing the same. has been done. In addition, JP-A-58-2055-44 discloses a uranium adsorbent based on the coexistence of amidoxime groups and cation exchange groups using the radiation rat method, and JP-A-58-205545 discloses an amidoxime adsorbent based on the radiation grafting method. A uranium adsorbent in which a neutral hydrophilic group and a neutral hydrophilic group coexist has been proposed.

However, although these uranium adsorbents do not swell with seawater, they are manufactured by graft polymerization using radiation, and in order to localize the amidoxime groups on the surface or surface layer of the base material, it is necessary to is limited to gas phase grafting reactions by

Problems to be Solved by the Invention The present invention provides a method for easily producing a metal adsorbent in which an amidoxime group is graft-polymerized on the surface or surface layer of a base material made of polyolefin, without being subject to the above-mentioned limitations. The purpose is to provide.

Means to solve problems The present inventors converted amidoxime groups into polyolefins.

As a result of various studies on improving the method of graft polymerization on the surface or surface layer of a base material consisting of
The present invention was completed based on the discovery that the object can be achieved by performing graft polymerization after previously subjecting the surface of the base material to low-temperature plasma treatment.

That is, in the present invention, after a base material made of polyolefin is previously subjected to surface treatment by low-temperature plasma treatment, the nitrile group is converted into amidoxime by reacting the polymer with hydroxylamine. After producing a graft polymer in which one or more convertible polymerizable monomers are brought into contact and the polymerizable monomer is grafted onto the surface or surface layer of the base material, the graft polymer is By reacting with hydroxylamine, the 0°)9′ group in the graft chain was converted to 7°1″ AfiK.
This is a method for producing a metal adsorbent characterized by the following.

The polyolefin used in the present invention is an olefin homopolymer, a copolymer, or a halogenated polyolefin, and its molecular weight ranges from normal to ultra-high molecular weight of 1×10 6 or more. Examples include polyethylene, ethylene-propylene copolymer, polyglopylene/propylene-ethylene copolymer, propylene-butylene/copolymer, polybutene, poly-4-methylpentene, and the like.

Further, the shape of the base material is not particularly limited, and any shape can be selected depending on the purpose.

For example, it is possible to obtain adsorbents in the form of particles, spheres, membranes, tubes, fibers, as well as fabrics, nets, and mats obtained by processing these materials. , a microporous membrane, a particulate form, etc. are preferable. Also,
Among these, fibers or microporous membranes made of ultra-high molecular weight polyolefins with a weight average molecular weight of lX10' or more can be made into high strength, high elasticity, and extremely thin films by stretching.
This is a more desirable base material.

High-strength, high-elasticity fibers made of ultra-high molecular weight polyolefins can be obtained, for example, by the method described in JP-A-58-5228. Further, a microporous membrane made of ultra-high molecular weight polyolefin can be obtained, for example, by the following method.

An ultra-high molecular weight polyolefin is thermally dissolved from 1 to 15 weight x weight in a solvent such as liquid paraffin to form a homogeneous solution. A sheet is formed from this solution and rapidly cooled to form a gel-like sheet. The amount of solvent contained in this gel-like sheet is adjusted to 10-90% by treatment with a volatile solvent such as methylene chloride. This gel-like sheet is heated at a temperature below the melting point of the polyolefin and stretched to an areal magnification of 10 times or more. The solvent contained in this stretched film is extracted and removed with a volatile solvent such as methidichloride, and then dried. By such a method, thickness CLI ~1Gpm porosity 5O-95X,
Average pore diameter α1-4 pm and breaking strength 200 kg/-
The above microporous membrane can be obtained.

It is important that the base material made of polyolefin in the present invention is previously subjected to surface treatment by low temperature plasma treatment. This makes it possible to limit the target portion to which the amidoxime group is grafted to the surface or surface layer of the base material. Furthermore, unlike grafting by radiation treatment, there is no need to carry out the grafting reaction in the gas phase.

Low-temperature plasma treatment uses a low-pressure oxidizing gas, such as oxygen or nitrogen, using high-frequency discharge or microwave discharge.
An active gas is generated by exciting a gas mixed with air, argon, helium, etc., and the active gas is brought into contact with the base material. The processing conditions include a pressure of 11 to 10 torr and a processing time of 15 seconds or more, preferably 20 to 40 seconds. In addition,
The processing conditions include plasma processing equipment, graft reaction conditions,
The ratio of the adsorbed layer of amidoxime groups to the non-adsorbed layer of the final adsorbent is 1:10 to 10, although K is selected appropriately depending on the degree of formation of active sites in the base material and the characteristics of the polymerizable monomer. 20
: It is preferable to set it as the range of 1G.

In the present invention, the polymerizable monomer containing a nitrile group and which can be converted into a diamidoxime group by reacting the polymer with hydroxylamine includes, for example, acrylonitrile, vinylidene cyanide, crotonitrile, methacrylaterile, and chloracrylonitrile. , 2-cyanoethyl acrylate, 2-cyanoethyl methacrylate, etc., and these can be used alone or in combination of two or more.

In the graft polymerization of the above-mentioned nitrile group-containing polymerizable monomer onto the base material made of polyolefin y in the present invention, the substrate surface-treated by low-temperature plasma treatment is treated with the nitrile group-containing polymerizable monomer. Immerse in the solution or diluted solution for 30 minutes to 2 hours at a reaction temperature below the boiling point of the polymerizable monomer.
This can be achieved by carrying out the reaction for 4 hours.

The conversion of the nitrile group in the graft chain into an amidoxime group in the present invention can be carried out by a known method using hydroxylamine. That is, the graft polymer obtained by the above method is immersed in a solution of 1-hydroxylamine salt, and the reaction temperature is 40 to 80°C for 30 minutes to 100 minutes.
Allow time to react. Examples of the solvent at this time include water, dimethylformamide, dimethylsulfoxide t-alcohols, and tetrahydro-7-alcohol, and these may be used alone or in a mixture of two or more. In addition, as hydroxylamine, hydrochloride, sulfate, acetate, etc. are used, and the concentration thereof is 1 to 10 weight X, preferably 3
~6 weight X.

As described above, according to the method of the present invention, amidoxime groups can be easily grafted onto the surface or surface layer of a base material made of polyolefin by a liquid phase reaction. Also, low temperature plasma treatment is easier to handle than conventional radiation graft polymerization.

Moreover, the obtained adsorbent has only amidoxime groups and is highly effective. Furthermore, since the base material is polyolefin, it has excellent acid resistance, alkali resistance, and seawater resistance.
It is also inexpensive.

Due to the above-mentioned excellent properties, the adsorbent obtained by the method of the present invention is capable of adsorbing metals that occur in trace amounts in aqueous solutions, such as uranium, cadmium, silver, mercury, magnesium, and vanadate. Although it can be used as a material, it is particularly suitable as a uranium adsorbent in seawater.

However, these do not limit the scope of the present invention. Incidentally, the grafting rate was determined using the following formula.

Liquid paraffin (64cs) containing 4.0% by weight of high density polyethylene with weight average molecular weight (7w) 2
t/40°C) 100 parts by weight of mixed solution 1c 0.125 parts by weight of 2,6-di-t-butyl-P-cresol and tetrakis(methylene-5-(3,5-di-t-phthyl-4)
-Hydroxyphenyl)-Probionate 3F2F12
5 parts by weight of antioxidant were added and mixed. This mixed solution was filled into an autoclave equipped with a stirrer, and heated and stirred to 200° C. to obtain a homogeneous solution.

This solution was filled into a heated mold and rapidly cooled to 15° C. to form a gel-like sheet. This gel-like sheet was immersed in methylene chloride, and then evaporated and dried while attached to a smooth plate to obtain a gel-like sheet with a liquid paraffin content of 590% by weight.

The obtained sheet was subjected to simultaneous biaxial stretching at a temperature of 130° C., a speed of 306/min, and a magnification of 10×1 G. The resulting stretched film was washed with methylene to extract and remove the remaining liquid paraffin, and dried to form a microporous film with a thickness of 1.0 pm, tensile strength of 1550 kg/st, porosity of 6 & OX, and average pore diameter of 2.0 μm. A membrane was obtained.

Example 1゜The microporous membrane made of ultra-high molecular weight high-density polyethylene obtained in the reference example was treated with a microwave plasma treatment device (manufactured by Toshiba,
Product name TMZ-2032 type, 2450MHz* Output 1kw) was used, and air was used as the gas at a reaction pressure of 1.
Plasma was irradiated for 50 seconds at 0 torr.

Next, this membrane was mixed with 50 weight of acrylonitrile in an aqueous solution (
The membrane was immersed in Mohr's salt IX (containing 10-'' mOL/L) and reacted at 50°C for 60 minutes to obtain a grafted membrane with a graft ratio of 15 x by weight.

Next, this graft membrane was mixed with 3 weights of hydroxylamine hydrochloride neutralized with potassium hydroxide and water-ethanol (1:
1 weight ratio) and reacted at 80° C. for 6 hours to obtain an adsorbent with an anion exchange amount of 1.5 meq/l. 1 liter of the obtained adsorbent was mixed with cupric chloride CLO
5mot7t to sodium acetate to mot/L
and acetic acid 1. 500 m of copper solution of Omot/l was added and stirred at 25°C for 60 hours to adsorb copper on the adsorbent. Thereafter, the distribution of copper was observed by measuring the characteristic X-ray intensity of copper using an X-ray microanalyzer (XMA). As a result, it was found that no amidoxime (group) was present in the center of the base material.

This adsorbent (LIN) was immersed in 500 ml of seawater that had been adjusted to a uranium concentration of 1 my/t by adding uranyl nitrate, and was shaken at 30°C for 1 hour to adsorb uranium.The amount of uranium adsorbed was 15μII7'a 1 N-adsorbent.

Comparative Example 1 The microporous membrane used in Example 1 was applied with an accelerating voltage of 165 KeV.
, irradiated with an electron beam of 15 Mrad at a current value of 8 mA,
This membrane was immersed in an aqueous solution of 50 wt.
A graft membrane with a weight of 5X was obtained. This graft membrane was reacted with hydroxylamine hydrochloride in the same manner as in Example 1 to obtain an adsorbent with an anion exchange capacity of 17 meq/JF.

As a result of adsorbing uranium in the same manner as in Example 1, the amount of adsorption was 7wy/αl11-adsorbent.

In addition, the graft layer was distributed over the entire cross-section of the membrane.

Example 2 A strong system made of high-density polyethylene with a weight average force of 2×10· (thickness 355 denier, tensile modulus 557.1)
g/d1 strong 55.611/6. Nodule strength 14.211
/d) Ic, the same plasma treatment as in Example 1 was performed.

Bubble this thread with nitrogen gas in advance to increase the dissolved oxygen concentration by α1.
Soaked in acrylonitrile with a concentration of 25 ppm or less
A graft thread with a graft ratio of 25X was obtained by reacting at ℃ for 5 hours.

This graft yarn was reacted with hydroxylamine hydrochloride in the same manner as in Example 1 to give an anion exchange capacity of 2.5 meq/
An adsorbent of fI was obtained.

As a result of adsorbing uranium in the same manner as in Example 1, the amount of adsorption was 2.1 μm//αllll-adsorbent. Also,
The graft layer was only on the surface of the yarn.

Comparative Example 2 The strong yarn used in Example 2 was subjected to electron beam irradiation in the same manner as in Comparative Example 1, and this yarn was immersed in the same acrylonitrile as in Example 2 and reacted at 25°C for 5 hours. A Graf 2 graft yarn with a graft ratio of 25 N was obtained.This graft yarn was reacted with hydroxylamine hydrochloride in the same manner as in Example 2 to obtain an adsorbent having an anion exchange capacity of 1.7 meq/jl.

As a result of adsorbing uranium in the same manner as in Example 1, the amount of adsorption was 1.6 μg/g-adsorbent. In addition, the graft layer was distributed throughout the cross-section of the yarn.

Example 5 A polypropylene nonwoven fabric (weighing 15,171 g?)
The same plasma treatment as in Example 1 was performed.

This nonwoven fabric was immersed in a 50 weight acrylonitrile x methanol solution and reacted at 25°C for 6 hours to achieve a grafting rate of 2.
A 0% by weight nonwoven fabric was obtained. This nonwoven fabric was reacted with hydroxylamine hydrochloride in the same manner as in Example 1 to obtain an adsorbent having an anion exchange amount of 10 meq/g.

As a result of adsorbing uranium in the same manner as in Example 1, the adsorption was 2.0 μI//I/− adsorbent.

Moreover, the graft layer was only on the surface of the fiber.

Comparative Example 5 Compared to the polypropylene nonwoven fabric used in Example 5, Comparative Example 1
The same electron beam irradiation as in Example 3 was performed, and the nonwoven fabric was immersed in the same acrylonitrile as in Example 3, and reacted at 25° C. for 8 hours to obtain a nonwoven fabric with a graft ratio of 20×@X. This nonwoven fabric was reacted with hydroxylamine hydrochloride in the same manner as in Example 5 to obtain an adsorbent having an anion exchange capacity of 1.7 meq/#.

As a result of adsorbing uranium in the same manner as in Example 1, the amount of adsorption was 1.7 μji, Ql-adsorbent.

In addition, the graft layer was distributed throughout the entire cross-section of the fiber.

Claims (1)

[Claims] (1) After a base material made of polyolefin is previously surface-treated by low-temperature plasma treatment, the nitrile group is converted to amidoxime by reacting the polymer with hydroxylamine. One or more types of polymerizable monomers to be obtained are brought into contact to produce a graft polymer in which the polymerizable monomer is grafted onto the surface or surface layer of a base material, and then the graft polymer and hydroxylamine are combined. A method for producing a metal adsorbent, which comprises converting a nitrile group in a graft chain into an amidoxime group by reaction.