JP2002018293A - Cation exchange resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain at novel cation exchange resin excellent in capacity for separating and recovering a least one kind of metal ion from a mixture of many kinds of metal ions. SOLUTION: The cation exchange resin is constituted by introducing a sulfonic acid group into a divinyl monomer/monovinyl monomer copolymer resin, which contains divinyl benzene as a crosslinking agent, as a functional group and at least a part of the monovinyl monomer is a polycyclic aromatic monovinyl monomer and a degree of crosslinking represented by divinyl benzine/ total monomer is 2-70 mol %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cation exchange resin useful for separating and recovering metal ions. More specifically, the present invention relates to a phosphonic acid type ion exchange resin suitable for adsorption and separation of metal ions such as a typical metal element, a transition metal element, a lanthanide element, and an actinide element.

[0002]

2. Description of the Related Art Cation exchange resins have the ability to exchange metal ions with protons of introduced functional groups, and are used for adsorption and separation of metal ions. As the resin, a resin based on a styrene-divinylbenzene copolymer is generally used. As the functional group to be introduced, sulfonic acid is generally used, while phosphonic acid is
High selectivity for metal ions such as typical metal elements, transition metal elements, lanthanide elements, and actinide elements (the pH values at which each metal ion is eluted are separated and easy to separate), so separation and recovery of these metal ions Has attracted attention. However, in the case of a metal ion such as Lu (III), Gd (III), or Al (III), which has remarkably higher adsorption ability than a proton, the pH must be 0.5 to elute the metal ion once adsorbed. It is necessary to treat with the following high-concentration acid, and there is a problem that it is practically difficult to implement from the viewpoint of cost and waste liquid treatment. However, Lu (II
Ion exchange resin which elutes many metal ions such as I), Gd (III) and Al (III) in a commercially practicable pH range of 0.5 or more and has high selectivity for heavy metal ions. Has not been found.

A phosphonic acid type cation exchange resin conventionally used for separation and recovery of metal ions is J. Appl. Po.
lym.Sci., 52 (8), 1153-1164 (1994) and Sep.Sci.Technol.,
32 (6), 1099-1105, (1997) a copolymer of a monovinyl monomer such as styrene and a divinyl monomer such as divinylbenzene having a phosphonic acid group introduced therein, The aromatic compounds constituting the exchange resin were all monocyclic aromatic compounds such as styrene and divinylbenzene.

[0004]

An object of the present invention is to provide a novel phosphonic acid type cation exchange resin. Another object is to provide a phosphonic acid-type cation exchange resin suitable for separating or recovering one or more metal ions from a mixture of various metal ions.
Furthermore, an object of the present invention is to provide Lu (III), Gd (III), A
It is an object of the present invention to provide a cation exchange resin which elutes many metal ions including l (III) and the like in a commercially practicable pH range of 0.5 or more and has high selectivity to heavy metal ions. .

[0005]

Means for Solving the Problems The present inventors have determined that the ion selectivity of an ion exchange resin is not determined solely by the coordination bonding force between a donor atom of a functional group and a metal ion.
Focusing on the involvement of the hydrophilic and hydrophobic properties of the resin phase,
As a result of various studies on the monomers constituting the resin serving as the skeleton, the present inventors have found that the use of a polycyclic aromatic monovinyl monomer as a part of the monomers achieves the above object, and has reached the present invention.

That is, the present invention provides a cation exchange resin in which a phosphonic acid group is introduced as a functional group into a copolymer resin of a divinyl monomer and a monovinyl monomer using divinylbenzene as a crosslinking agent, wherein at least a part of the monovinyl monomer is large. A cyclic aromatic monovinyl monomer having a degree of crosslinking represented by divinylbenzene / total monomer of 2
It is a cation exchange resin characterized by being about 70 mol%. In a preferred embodiment of the present invention, the ratio of the polycyclic aromatic monovinyl monomer is 2% of the monovinyl monomer.
0 to 100% (mol), the polycyclic aromatic monovinyl monomer is vinyl biphenyl or vinyl naphthalene, and the cation exchange resin is used for adsorption or separation of metal ions.

The monovinyl monomer constituting the phosphonic acid type cation exchange resin of the present invention must be at least partially a polycyclic aromatic monovinyl monomer, preferably at least 20 mol%, more preferably at least 50 mol%. The content is more preferably 70 mol% or more. The greater the proportion of polycyclic aromatic monovinyl monomer, the more advantageous the environment inside the ion exchange resin is for the separation or recovery of metal ions.

The polycyclic aromatic monovinyl monomer used in the present invention includes condensed aromatic hydrocarbons such as naphthalene, anthracene and phenanthrene, and non-condensed aromatic hydrocarbons such as biphenyl and terphenyl to which a ring is directly bonded. And compounds having two or more aromatic rings such as aromatic-substituted aliphatic hydrocarbons such as diphenylmethane and diphenylethane, in which one vinyl group is substituted, and the substitution position may be any position. . Suitable polycyclic aromatic monovinyl monomers include 4-vinylbiphenyl, 3
Those mainly containing -vinylbiphenyl, 2-vinylbiphenyl, 1- or 2-vinylnaphthalene. The monovinyl monomer used as a raw material may be a pure product, but may contain a small amount of another vinyl compound.

Monovinyl monomers other than polycyclic aromatic monovinyl monomers include styrene, vinyl toluene,
Examples thereof include α-methylstyrene, ethylvinylbenzene, vinylchlorobenzene, and chloromethylstyrene, and are preferably styrene or a combination of styrene and another monovinyl monocyclic aromatic monomer. In addition to the monovinyl aromatic monomer, it is also possible to use a non-aromatic monovinyl monomer in combination for the purpose of modification.

The divinyl monomer as a crosslinking agent is generally divinylbenzene. If the degree of crosslinking represented by divinylbenzene / total monomer is too low, the strength of the ion exchange resin decreases. Speed decreases. Therefore, the degree of crosslinking needs to be in the range of 2 to 70 mol%, preferably 3 to 30 mol%.

Examples of the divinyl monomer other than divinylbenzene include divinyltoluene, ethylene glycol dimethacrylate, bisphenol A dimethacrylate, and the like. Preferred is divinylbenzene or a combination of divinylbenzene and another divinyl monomer. As the divinyl monomer as a crosslinking agent, a polycyclic aromatic compound such as divinyl biphenyl and divinyl naphthalene can be used if necessary.
% Or less, preferably 5% or less.

The copolymerization of a divinyl monomer and a monovinyl monomer can be carried out by a known method, and by adjusting the polymerization conditions or the degree of crosslinking, a copolymer of gel type, porous type or macroporous type can be obtained. Coalescence can be obtained. As a preferred copolymerization method, a polymerization initiator such as peroxides is added to the monomer,
Solution or suspension polymerization. In order to obtain a bead-shaped resin, it is preferable to use suspension polymerization. In this case, a dispersion stabilizer such as polyvinyl alcohol and a salting-out agent such as sodium chloride may be added to the aqueous phase. Polymerization temperature is 50 ~
The appropriate polymerization time is about 90 ° C. and the polymerization time is about 1 to 12 hours. At this time, a diluent such as heptane or methanol may be present in the polymerization system in order to obtain a giant network structure, and a diluent such as heptane or methanol is included in the polymerization system in order to obtain a gel-type resin. And a method in which no substantial diluent is present. The cation exchange resin of the present invention may be any of a gel type, a porous type and a macroporous type, but preferably has a gel type in which the degree of crosslinking represented by divinyl monomer / total monomer is 2 to 10 mol%. If it is 10 mol% or more, it is preferable to use the porous type and the macroporous type.

[0013] Phosphonation of the copolymer resin thus obtained can be carried out by a known method. Specifically, for example, a copolymer resin is reacted with chloromethyl ether or the like in the presence of anhydrous aluminum chloride to introduce a halomethyl group into an aromatic ring, and phosphorus trichloride and anhydrous aluminum chloride are added thereto, followed by a hydrolysis reaction. And a method in which phosphorus trichloride and anhydrous aluminum chloride are added to the copolymer to cause a reaction, a phosphinic acid group is introduced into the aromatic ring, and then the phosphinic acid group is oxidized with nitric acid to form a phosphonic acid group. Two methods are typical. The cation exchange resin of the present invention thus obtained has an exchange capacity of
It is preferably in the range of about ^{2 to 20} m equivalent / g and specific surface area of about 5 to 100 m ² / g.

[0014] The cation exchange resin of the present invention comprises a waste liquid treatment,
It is effective not only for water treatment such as recovery of valuable metals, but also for pure water for boiler water used in thermal power plants and nuclear power plants.
In addition to these, it can be widely used in the field of pharmaceutical foods for manufacturing various industrial products and for refining chemicals and shochu.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The cation exchange resin of the present invention can be suitably used for adsorption or separation of metal ions. Hereinafter, this embodiment will be described. Since phosphonic acid type cation exchange resin has hydrogen ion, when it comes into contact with metal ion, exchange reaction between hydrogen ion and metal ion occurs, and metal ion is ion-bonded to phosphonic acid group in cation exchange resin. Adsorbed. At this time, the adsorbed metal is more stably adsorbed by the coordination bond between the phosphonic acid group and the oxygen atom. At this time, the metal ion adsorption power differs depending on the valence, atomic radius, and pH of the metal, so that the metal can be separated and recovered.

In the present invention, the efficiency of separation and recovery of metal ions by a phosphonic acid-type cation exchange resin is evaluated by experimentally measuring a half-extraction pH derived by the following theory. Since phosphonic acid is a diprotic acid, when the cation exchange resin adsorbs metal ions, the formula (1)
Two kinds of chemical equilibrium represented by (2) hold,
At this time, the equilibrium constants K 1 and K 2 are given by the following equations (3),
(4), and the distribution ratio D is represented by equation (5).

[0017]

Embedded image _{K 1 = [(RPO 3 H} ) n M] [H +] n / [RPO 3 H 2] n [M n +] (3) K2 = [(RPO 3 H) n / 2 M] [H +] n / [RPO ₃ H ₂ ] ^{n / 2} [M ^{n +} ] (4) D = [[(RPO ₃ H) _n M] + [(RPO ₃ H) _{n / 2} M]] / [M ^{n +} ] = [K1 [RPO ₃ H ₂ ] ⁿ + K 2 [RPO ₃ H ₂ ] ^{n / 2} ] / [H ⁺ ] ⁿ (5) ( Where [RPO ₃ H ₂ ] is the equilibrium concentration of the phosphonate group,
[M ^{n +} ] represents the equilibrium concentration of the metal ion, and [(RPO ₃ H) _n M] and [(RPO ₃ H) _{n / 2} M] represent the concentration of the metal ion adsorbed on the ion exchange resin.

Here, K1 and K2 are constants, and [RPO ₃ H ₂ ] can be regarded as constant under the actual adsorption conditions since the total number of moles of phosphonic acid groups is much larger than the number of moles of metal ions. Equation (6) is obtained. D = Const / [H ⁺ ] ⁿ (6) When the logarithm of both sides is taken, logD = npH + logConst., And the distribution ratio D depends on the pH and the valence of the metal. Therefore, the higher the pH, the more easily the metal ions are adsorbed on the ion exchange resin, and the higher the valence of the metal, the more easily the metal ions are adsorbed on the ion exchange resin. Here, 50 of the metal ions in the measurement system
The pH at which% is adsorbed on the ion exchange resin (semi-extraction pH) is used as an index of the adsorption power of metal ions to the ion exchange resin.

The actual separation operation of metal ions is performed by continuously passing an aqueous solution of a mixture of metal ions from the top of a column filled with a phosphonic acid-type cation exchange resin under the condition of pH 4 to 5 to temporarily remove all the metal ions. After adsorbing ions, pH
Two or less acidic aqueous solutions are continuously passed from the top of the column, and the metal ions desorbed and distilled off due to the difference in adsorption power with the ion exchange resin are collected. In this case, a metal having a higher half-extraction pH has a weaker adsorbing power to the ion exchange resin, and thus flows out by passing a small amount of an acidic aqueous solution. Further, since divalent metal ions have weaker adsorption power to the ion exchange resin than trivalent metals, they flow out through a small amount of acidic aqueous solution. As described above, it is possible to separate and recover from the metal ion mixture by the difference between the half extraction pH of the metal ion and the valence of the metal. The acidic aqueous solution used at this time is suitably an inorganic acid having a strong acidity such as nitric acid, sulfuric acid, and hydrochloric acid.

In general, in the case of a mixture of various kinds of metal ions, it is desirable that the respective half extraction pHs are as different as possible.
The above difference is preferred. In addition, when a metal having a half extraction pH of 0.5 or less is adsorbed, desorption becomes difficult even when an acidic aqueous solution of about 1N is passed. It is preferable that the acid concentration used in the desorption is as low as possible from the viewpoint of economy and environmental protection. Therefore, it is desirable that the semi-extraction pH be as high as possible.

In a conventional phosphonic acid type cation exchange resin composed of only a monocyclic monovinyl monomer such as styrene, the half-extraction pH was sometimes less than 0.2. In the case of the phosphonic cation exchange resin in which the raw material monovinyl monomer is composed of a polycyclic aromatic monovinyl monomer, almost all of such materials have a half-extraction pH of 0.2 or more, thereby enabling selective recovery of metal ions. In the case of conventional phosphonic acid-type cation exchange resins, half-extracted pH is used for some metal ions with extremely strong adsorptive power.
Was 0.5 or less, and recovery was sometimes difficult. However, when the phosphonic acid type cation exchange resin of the present invention was used, most of such substances had a half-extraction pH of 0.5 or more and appropriate adsorption. Since it has power, it can be collected.

[0022]

EXAMPLE 1 500 ml of distilled water and 2 g of polyvinyl alcohol were dissolved in a 1000 ml three-neck separable flask equipped with a stirrer and a condenser. To this, 3.5 g of divinylbenzene solution (55% of divinylbenzene, 45% of ethylvinylbenzene) and 26.5 g of vinylbiphenyl, 2,2,2
A mixed solution of 25 ml of 4-trimethylpentane and 0.45 g of azobisisobutyronitrile was added, and the mixture was reacted at 80 ° C. for 10 hours with stirring while introducing nitrogen gas into the system. From this, the copolymer resin was recovered by filtration and immersed in 150 ml of toluene at 25 ° C. for 8 hours. Thereafter, the copolymer was taken out, immersed in 150 ml of methanol at 25 ° C. for 8 hours, filtered and air-dried to obtain 29.5 g of a copolymer resin.

In a 100 ml flask equipped with a reflux condenser, 2 g of the copolymer tree and anhydrous aluminum chloride 1
0.4 g and phosphorus trichloride (30 ml) were added and reacted at 80 ° C. for 6 hours. After the reaction, the resin was transferred to an ice-water bath to decompose unreacted substances and introduce phosphinic acid groups into the copolymer. The resin was washed with ion-exchanged water until the washing solution became neutral, and air-dried. 1 g of phosphinic acid-introduced resin and 30 ml of concentrated nitric acid
Was placed in a 50 ml flask and stirred at 40 ° C. for 10 hours to oxidize phosphinic acid groups to phosphonic acid groups. Wash the resin with ion-exchanged water until the washing solution is neutral,
A phosphonic acid type cation exchange resin was obtained. The surface area of this cation exchange resin is 20 m ² / g, and the exchange capacity is 7.
It was 6 meq / g.

1 g of the cation exchange resin was placed in a 1000 ml Erlenmeyer flask, and lutetium (L) having a metal ion concentration of 0.1 mmol / l was adjusted to pH 0.1 to 4.0 with hydrochloric acid.
u), chromium (Cr), lead (Pb), cadmium (C
d), an aqueous nickel (Ni) solution was added and the mixture was stirred at 30 ° C. for 24 hours to adsorb the metal to the cation exchange resin. The distribution ratio was determined by measuring the metal ion concentration of the aqueous solution before and after the adsorption operation, and at the same time, the pH at which 50% of the metal ions were adsorbed (half extraction pH) was measured. Table 1 shows the results.

Examples 2 to 3 The same procedures as in Example 1 were carried out except that part of vinyl biphenyl was changed to styrene. Example 4 The procedure of Example 1 was repeated, except that vinyl naphthalene was used instead of vinyl biphenyl. Examples 5 to 6 Same as Example 1 except that a part of vinyl naphthalene was styrene.

Comparative Example 1 The procedure of Example 1 was repeated except that vinyl biphenyl was entirely styrene. Table 1 shows the results together with the results of Examples 1 to 4.

[0027]

[Table 1]

[0028]

The cation exchange resin of the present invention has excellent ability to separate and recover one or more metal ions from a mixture of various metal ions.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J100 AB00P AB02R AB03R AB04R AB08R AB15Q AB16Q AL60Q AL62Q BA02H BA02P BA65H BA65P BA67H BA67P BB01H BB01P BC43Q CA04 CA05 CA31 HA08 HA61 HB30 HB44 HB57 HC13 JA16

Claims (4)

[Claims] 1. A cation exchange resin in which a phosphonic acid group is introduced as a functional group into a copolymer resin of a divinyl monomer and a monovinyl monomer using divinylbenzene as a crosslinking agent, wherein at least a part of the monovinyl monomer is a polycyclic aromatic monovinyl resin. Monomer and divinylbenzene /
A cation exchange resin having a degree of crosslinking represented by all monomers of 2 to 70 mol%. 2. The cation-type ion exchange resin according to claim 1, wherein the proportion of the polycyclic aromatic monovinyl monomer is 20 to 100% (mol) of the monovinyl monomer. 3. The polycyclic aromatic monovinyl monomer is vinyl biphenyl or vinyl naphthalene.
A cation exchange resin as described. 4. The cation exchange resin according to claim 1, which is used for adsorption or separation of metal ions.