JPH0326336A - Absorbent for iron and cobalt ion and method for absorbing iron and cobalt ion using same - Google Patents

Abstract

PURPOSE:To effectively remove Fe ions and Co ions in an aqueous solution by constituting the absorbent of ethylene copolymer comprising 40-95wt.% ethylene and 60-5wt.% aminoalkyl acrylate comonomers. CONSTITUTION:The ethylene copolymer is synthesized by high-pressure radical polymn. method. It comprises 40-95wt.% ethylene and 60-5wt.% aminoalkyl acrylate comonomer expressed by formula I (wherein R1 is hydrogen or a methyl group, R2 and R3 are hydrogen or alkyl groups with 1-4 carbons, and n is an integer of 1-4) and has the number average mol.wt. of 5000-50000. This ethylene copolymer is molded into a tube, sheet, film, fiber or cloth as an absorbent. The obtd. absorbent can effectively absorb and remove Fe and Co ions from an aqueous solution which is priority prepared to be <=pH2.1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an absorber having a function of separating and recovering iron and cobalt ions using a functional resin, and an absorption method using the same.

More specifically, it relates to an iron and cobalt ion absorber made of a copolymer of ethylene and an aminoalkyl acrylate comonomer used to separate and recover these metals from an aqueous solution of iron and cobalt salts, and an absorption method using the same. It is.

Conventional technology> Conventionally, aminocarboxylic acid groups, iminodiacetic acid, amidoxime groups, primary amines, secondary amines, tertiary amines, etc. were introduced into resins having nitrile groups or styrene-divinylbenzene copolymer resins. Various types of chelate resins have been proposed for uses such as recovering valuable metals in water and removing metal ions from industrial wastewater, but these are usually in the form of beads or gels, and are used in filters and filtration systems. It is difficult to process it into an absorber with a desirable shape and low resistance.

In addition, there are other known methods for recovering valuable metals and removing metal ions from wastewater, such as separation and concentration using precipitation separation methods and solvent extraction methods, but in the case of low concentrations, There are many problems such as difficulty in separation.

For example, for the recovery of valuable metals, group 3A metals such as yttrium, cerium, and gadolinium (group names are IUPAC
According to the periodic table by nomenclature. Same hereafter) Zirconium,
4A group such as hafnium, 5A group such as niobium and tantalum
group, 6A group such as molybdenum, 7A group such as technetium
The target metals are group 8 metals such as rhodium, palladium, and platinum, group IB metals such as silver and gold, and group 3B metals such as gallium, and chelate resins and precipitation separation methods are being attempted.

On the other hand, in addition to the above metals, chromium, manganese, iron, cobalt, copper, zinc,
Similar chelate resin and precipitation separation methods have been attempted for metals such as tin and lead.

For example, iron is removed because it adversely affects the color and taste of drinking water, and of textiles, laundry, leather, and brewing products from industrial water.

Furthermore, in industrial wastewater, zinc plating, tin plating, steel plate and
The manufacturing industry of wires and rods requires acid cleaning of iron surfaces, so there is acidic wastewater that contains iron, and mine water contains wastewater that contains sulfides and sulfates.

In the case of cobalt, it is often contained in wastewater from wet and dry smelting.

Generally, iron and cobalt are removed by a precipitation separation method in which they are concentrated and converted into hydroxides with an alkaline compound. However, the lower the concentration, the more difficult the separation becomes, so attempts have been made to remove them using ion exchange resins or chelate resins, but all of these existing functional resins are in a gel state with a three-dimensional crosslinked structure. The fact that it could only be tested was a condition that significantly limited the method of industrial use.

The reason why these resins are used as a three-dimensional crosslinked structure is that they have strong hydrophilic properties in order to obtain absorption rates that are sufficient for practical use, or due to the characteristics of the absorption active groups themselves, so they do not swell easily in aqueous solutions. The aim is to prevent it from becoming more complex and eventually collapsing.

However, if this function could be imparted to a one-dimensional thermoplastic polymer, it would be possible to create any shaped product, and by adding an external cross-linking process, it would be possible to improve the absorption rate and reduce pressure loss. This method offers many advantages such as expanding the range of selection and freedom of equipment configuration, and is expected to greatly contribute to improving technology for removing metal ions such as iron and cobalt from industrial wastewater.

A copolymer of ethylene and a dialkylaminoalkylacrylamide comonomer has been proposed as a one-dimensional thermoplastic polymer capable of absorbing metal ions (Japanese Unexamined Patent Publication No. 63-304010), but it is relatively expensive. This is thought to limit its industrial use because it is a common comonomer.

The present invention has found that iron and cobalt ions in an aqueous solution can be absorbed and removed using a copolymer of ethylene and a relatively inexpensive dialkylaminoalkyl acrylate comonomer, as described below. and is industrially useful.

Problems to be Solved by the Invention The present invention uses a relatively inexpensive copolymer of ethylene and an aminoalkyl acrylate comonomer, which is known to have almost no ability to absorb metal ions, to absorb iron and cobalt. It enables processing from low-concentration solutions, which is a problem when separating, recovering, and removing iron and cobalt from various aqueous solutions or waste liquids containing ions, and is also suitable for increasing the efficiency of processing facilities such as filters. An absorber for iron and cobalt ions that can be applied to a wide variety of recovery technologies that could not be achieved with conventional ion exchange resins or chelate resins by processing the absorber into a certain shape.
The present invention also provides a method for absorbing iron and cobalt ions using the same.

Means for Solving the Problems> From this point of view, the present inventors have conducted intensive research and have found a material that has high absorption properties for iron and cobalt metal ions and that can be processed into a certain shape depending on the application. A copolymer of a specific set of aminoalkyl acrylate comonomers and ethylene was discovered as a new metal absorber that is easy to absorb, leading to the present invention.

That is, the first aspect of the present invention contains 40 to 95% by weight of ethylene, general formula (A) K3 (wherein, R1 is hydrogen or a methyl group, R2 and R3 are an alkyl group having 1 to 4 carbon atoms, and n is a 2. An ethylene copolymer containing 60 to 5% by weight of one or more aminoalkyl acrylate comonomers represented by (indicating an integer from 1 to 4) and a number average molecular weight of 5,000 to 50,000; The present invention relates to an absorber for iron and cobalt ions, which is characterized in that it is used at a pH of 1 or less.

To produce the ethylene copolymer used in the present invention,
Generally, high-pressure radical polymerization methods can be applied, as disclosed in Japanese Patent Publication No. 2-22523 and Japanese Patent Publication No. 49-45307. The conditions are approximately those of current high-pressure polyethylene production processes. Therefore,
This copolymer already has an economical basis for its own production.

In the present invention, the copolymer with ethylene is represented by the general formula (A), and specific examples include aminomethyl acrylate, aminoethyl acrylate, amino normal butyl acrylate, N-methylaminoethyl acrylate, Ethylaminoethyl acrylate, N-ethylaminoisobutyl acrylate, N-isopropylaminomethyl acrylate, N-isopropylaminoethyl acrylate, N-normal butylaminoethyl acrylate, N-tert-butylaminoethyl acrylate, N,N-dimethylaminomethyl Acrylic},
N,N-dimethylaminoethyl acrylate, Ni,N
-dimethylaminoisopropyl acrylate, N,N-
dimethylamino normal butyl acrylate, N-methyl-N-ditylaminoethyl acrylate, N-methyl-N-normal butylaminoethyl acrylate}, N,
N-diethylaminoethyl acrylate}, N,N-diisopropylaminoethyl acrylate, N,N-dinormalpropylaminonormalpropylacrylate}, N
, N-dinormal aminoethyl acrylate, N,N-
Acrylic acid esters such as di-normal butylamino normal propyl acrylate and methacrylic acid esters corresponding thereto can be mentioned. Particularly preferred comonomers include (di)alkylaminoethyl (meth)acrylates in which n is 2, specifically dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylamino-n-butyl acrylate, dimethylamino-n -butyl methacrylate,
Examples include one or more compounds selected from di-n-butylaminoethyl acrylate, di-n-butylaminoethyl methacrylate, methylaminoethyl acrylate, methylaminoethyl methacrylate, aminoethyl acrylate, and aminethyl methacrylate.

The meaning of the various limitations imposed on this copolymer and the method for measuring its physical properties will be described below.

First, in the general formula (A>) representing an aminoalkyl acrylate comonomer, n is 0 or larger than 9 l0 4, and/or comonomers corresponding to R2 and R3 with a carbon number larger than 4 are Not only is it relatively difficult and expensive to combine, but it is also unstable under heating and has too high a viscosity, making it impossible to apply it to the so-called high-pressure ethylene polymerization process.

The content of the aminoalkyl acrylate comonomer in the ethylene copolymer in the present invention is 60 to 5% by weight,
Preferably it is 55 to 15% by weight. More preferably, it is 50 to 20% by weight. If the aminoalkyl acrylate comonomer is less than 5% by weight, the iron and cobalt ion absorption capacity is too low, and if it exceeds 60% by weight,
The copolymer cannot be used as it is because the acid absorption capacity increases and the resin swells in the acidic solution, sometimes causing shape destruction. The acid absorption ability of the copolymer is thought to be due to the basicity of the amino groups, but the swelling of the copolymer is due to this absorption ability and the strength of the three-dimensional structure formed by the polyethylene microcrystals formed by the ethylene chains in the molecule. seems to be strongly related to. It can be inferred from the plot of the melting point (Tm) versus the amount of comonomer in Figure 2 of Japanese Patent Publication No. 53-61.94 that the polyethylene microcrystals decrease at an accelerated rate as the amount of comonomer increases.

Presumably, if the amount of comonomer exceeds 60% by weight, there will be almost no microcrystals. Therefore, in order to suppress the swelling of the copolymer to an industrially optimum level, crosslinking may be necessary. (Even when there are sufficient microcrystals, crosslinking can be carried out for the purpose of adjusting the swelling degree of the copolymer, reinforcing it, etc.) In addition to the chemical crosslinking method, the copolymer used in the present invention can be crosslinked. However, this copolymer with a comonomer content of more than 60% by weight has the advantage of being able to perform physical crosslinking, that is, electron beam crosslinking or radiation crosslinking.This is because the physical crosslinking of polyethylene is generally of the curing type. cross-linking methods are an unexplored field. Physical crosslinking is the most suitable method for crosslinking without damaging chemically active groups, but there are many points that require consideration regarding the behavior of the present copolymer in this case.

In producing the ethylene copolymer of the present invention, the purpose is to facilitate the continuous and stable supply of the aminoalkyl acrylate comonomer to the high-pressure polymerization system by pump, and to For the purpose of increasing flexibility, at least one other ethylenically unsaturated comonomer copolymerizable with ethylene can be combined as necessary. The polymerized units of the ethylenically unsaturated comonomer used in this case are 0 to 20% by weight,
Preferably it is 0 to 15% by weight. Preferred specific examples of the ethylenically unsaturated comonomer include methyl acrylate, ethyl acrylate, methyl methacrylate, and vinyl acetate.

The average molecular weight of the ethylene copolymer in the present invention is 13
The value of intrinsic viscosity determined from a tetralin solution at 5℃ is 0.1~
It is good if it falls within the range of 4 J/g. In terms of number average molecular weight, it is 5,000 to 50,000, and the melting index (JIs
K-6760. 190℃), 1,0
00 to Ig/10 min, preferably number average molecular weight of 8,000 to 40,000, melting index of 500 to 5
A range of 0 g/10 minutes is suitable. This range of intrinsic viscosity, number average molecular weight, or melting index is a necessary constraint when carrying out certain mold processing industrially.

Since this copolymer mainly has an ethylene structure, it can be processed in the same way as polyethylene when shaped into an absorber, making it industrially more useful.

The shape of the absorber made of this copolymer is tube,
Examples include sheets, films, rods, fibers, nonwoven fabrics, woven fabrics, and hollow fibers.These can be freely shaped into shapes, and they can also be easily processed into filters, pipes, etc. made of fibers and hollow fibers. can.

In addition to fibers made from this copolymer alone,
For the purpose of improving fiber strength, it can also be used as a fiber that is blended with a polyα-olefin resin such as polypropylene, a polyamide resin, a polyester resin, etc. and spun.

Furthermore, parallel type or core-sheath type composite yarns having a sheath of a poly-α-olefin resin such as polypropylene, polyamide resin, polyester resin, etc. and the present copolymer, and core-sheath type composite yarns having a sheath of the 13 14 polymer, and yarns made from the composite yarns are also available. Non-woven fabrics, woven fabrics, filters, etc., which are made of woven fabrics, can also be suitably used.

In addition, this copolymer can be applied not only alone but also as a composite material with other polymers, metal materials, glass, wood, and other inorganic materials. When used as a composite material, it is common for the present copolymer to share the functionality and for other materials to share the role as a structural material. In this case, the fact that the present copolymer is composed of nonpolar ethylene and polar aminoalkyl acrylate comonomers allows a wide range of materials to be selected as other materials due to their affinity.

The absorber according to the present invention has a pt{ (hydrogen ion index) of 2
．． Used below 1.

The second aspect of the present invention relates to a method for absorbing iron and cobalt ions, characterized in that the present copolymer is used as an absorber for iron and cobalt ions at a pl{ of 2.1 or less.

That is, the ability of the present copolymer to absorb iron and cobalt ions is thought to be due to the chelating ability or cationic nature of the comonomer, and is strongly controlled by pH.

At pH above 2.1, its absorption capacity decreases significantly. Since the absorption capacity also depends on the concentration of iron and cobalt ions in the aqueous solution, by finding the optimum hydrogen ion concentration conditions within the pH range showing acidity of 2.1 or less,
Although it is possible to achieve a favorable absorption separation, the type and concentration of the counter ion to the hydrogen ion is also considered to be an important factor.

Thus, the strong (pH-dependent) absorption ability of this copolymer is due to the fact that the amine group in the comonomer is chelated with at least one ligand or the amino group is quaternized and becomes an ionic bonding point. This suggests that

Here, the absorption of metal ions refers to not only the adsorption of metal ions into the absorber made of this copolymer, but also the precipitation of metal salts caused by pH changes in the absorber or on the surface of the absorber. It also includes the uptake or adhesion of metal ions from an aqueous solution into the absorber or onto the absorber surface due to precipitation.

15 l6 The process of absorbing and separating iron and cobalt ions from an aqueous solution using the present ethylene copolymer can be carried out using, for example, a fixed bed filled with beads or pellets of this tree to the required height, or a filter cloth made of fiber mat non-woven fabric or woven fabric. Alternatively, the aqueous solution to be treated is passed continuously through a filter having a structure in which a required number of stages are stacked with filters equipped with various shapes such as cylindrical filters. At this time, by selecting the size and shape of the packing or the mesh structure of the filter cloth, it is possible to create a variety of designs with emphasis placed on, for example, the effective absorption capacity of pressure loss, the absorption rate, and the method of replacing the packing. It is. These possibilities include, of course, continuous operation using moving bed or fluidized bed systems.

When the absorption amount of this copolymer reaches a breakthrough point, prompt regeneration or replacement operations should be carried out. For regeneration, elution can be achieved relatively easily by simply washing with water adjusted with alkali or mineral acid so that the pH is outside the proper absorption pH range exceeding 2.1.

This ease of elution is also an advantageous feature of the present invention.

In addition, if there is no need to recover iron and cobalt ions and the purpose is simply to separate them from an aqueous solution, or if multiple metal ions are mixed and recovery is not economical, it is possible to absorb metal ions. It is preferable to incinerate the copolymer in this state to further reduce its volume, and then dispose of the ashes by an appropriate method.

Furthermore, when recovering the absorbed metal, a method of incineration and recovery may also be considered.

In that case, since the present copolymer does not contain sulfur, it will not generate sulfur trioxide from itself upon incineration.

Therefore, if the treated wastewater does not contain sulfuric acid radicals or other sulfur compounds, corrosion problems, which are the most important accident in incinerators, can be avoided. Even if wastewater contains sulfur compounds, it is relatively easy to replace them, so the above-mentioned advantages can be utilized by adding some processes. This is another advantageous aspect of the l7 l8 process using the ethylene copolymer absorber according to the present invention.

<Examples> The present invention will be described below with reference to Examples, but the present invention is not limited thereto.

Example 1 A copolymer of ethylene and NN-dimethylaminoethyl methacrylate was obtained by a high-pressure radical continuous copolymerization method.

The composition is 58% by weight of ethylene and 42% by weight of the remainder.
is the comonomer N,N-dimethylaminoethyl methacrylate. The number average molecular weight is 2, OXIO', and the melting index is 110 g/
The time was 10 minutes (measured at 190°C). This was processed into cylindrical pellets of 2mmφx3+n+++L using an extruder and pelletizer, and then processed at 130℃ and 50kg/c.
n! A 0.5 mm thick sheet was prepared by hot pressing under the following conditions, and a 25 mm x 40 mm sample sheet (
0. 5g) was cut out. The sample sheet was immersed in an aqueous solution of ferric oxide (FeC13) at a concentration shown in Table 1 and a pH adjusted with hydrochloric acid.
After being kept at a temperature of 19°C for 4 hours, the sample was taken out and the adhering aqueous solution was removed using a filter paper and weighed to determine the weight increase.

In both cases, the sheet-like morphology was maintained even after absorption at high magnification.

Comparative Example 1 Using the same sample sheet as in Example 1, an absorption test was conducted in the same manner as in Example 1 by immersing it in an aqueous solution 50 whose pH was not adjusted at the ferric chloride concentration shown in Table 1. Ta.

If the pH is not adjusted, no absorption occurs.

Example 2 By high-pressure radical continuous copolymerization method, 57% by weight of ethylene and N,N-dimethylaminoethyl methacrylate 43
% by weight of ethylene copolymer was obtained. The number average molecular weight is IJ
XIO', melting index is based on JIS K-6760,
It was 230g/10 minutes (measured at 190°C). In the same manner as in Example 1, this was processed into cylindrical pellets of 2 mm diameter x 3 ml IIL.

0.5 g of this copolymer pellet was placed in an aqueous solution of ferric chloride at room temperature with an adjusted concentration of hydrochloric acid, and stirred with a stirrer for 16 hours. Iron in the aqueous solution before and after the experiment was measured using a plasma emission spectrometer (Seiko Electronics Industries, IPCAES sps-).
7000) to calculate the metal ion absorption rate by this copolymer. The results are shown in Table 2. If the concentration of iron ions is very low, it will be absorbed better if it is made strongly acidic.

Table 2 1) ptl=0.1 Example 3 Using the same copolymer sheet as in Example 1, an aqueous solution 50 was prepared with the ferrous chloride (FE!'Cl2) concentration shown in Table 3 and the pll was adjusted with hydrochloric acid. An absorption test was conducted in the same manner as in Example 1 by immersing the sample in a liquid solution. The results are shown in Table 3. All 21 and 22 retained their sheet-like shapes.

Comparative Example 2 Table 3 shows the results of an absorption test conducted in the same manner as in Example 3, except that p}l was adjusted to 3 with hydrochloric acid and the pH was not adjusted. Almost no iron ions were absorbed.

Example 4 Using the same copolymer sheet as in Example 1, 50 ml of an aqueous solution in which pi{ was adjusted with hydrochloric acid or sulfuric acid at the metal salt concentration shown in Table 4 was prepared.
l! An absorption test was conducted in the same manner as in Example 1. The results are shown in Table 4. In both cases, the sheet-like form was maintained.

Comparative Example 3 Table 4 shows the results of an absorption test conducted in the same manner as in Example 4, except that the pH was adjusted to a high level and the pH was not adjusted. Absorbed no metal ions.

Example 5 The same copolymer pellets as in Example 1 were heated at 130°C and weighed 50 kg.
/cI+! After hot pressing to form a press sheet with a thickness of 1 mm, a sample sheet of 3 Q mm x 4 Q mm was cut out and used as a metal ion absorber. A sample sheet was immersed in a 100% aqueous metal salt solution whose pH was adjusted with an acid and allowed to absorb at 60° C. for 3 hours. The results are shown in Table 5. In both cases, the sheet-like form was maintained.

Comparative Example 4 Table 5 shows the results of an absorption test carried out in the same manner as in Example 5, except that the pH was not adjusted. Almost no absorption.

Effects of the Invention As described above, according to the present invention, a copolymer of ethylene and an aminoalkyl acrylate comonomer can be freely processed into shapes and can be used in various forms. By adjusting the pH to 2.1 or less using an iron and cobalt ion absorber, iron and cobalt ions in the aqueous solution can be easily absorbed and removed.

27 (complete)

Claims (3)

[Claims] (1) 40 to 95% by weight of ethylene, general formula (A) ▲ Numerical formula, chemical formula, table, etc. ▼ (A) (In the formula, R_1 is hydrogen or a methyl group, R_2 and R
_3 contains 60 to 5% by weight of one or more aminoalkyl acrylate comonomers represented by hydrogen or an alkyl group having 1 to 4 carbon atoms, and n is an integer from 1 to 4, and has a number average molecular weight. An absorber for iron and cobalt ions, comprising an ethylene copolymer having a pH of 5,000 to 50,000 and used at a pH of 2.1 or less. (2) Aminoalkyl acrylate comonomer (A)
are dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylamino-n-butyl acrylate, dimethylamino-n-butyl methacrylate, di-n-butylaminoethyl acrylate, di-
The iron and cobalt ion absorber according to claim 1, which is one or more compounds selected from n-butylaminoethyl methacrylate, methylaminoethyl acrylate, methylaminoethyl methacrylate, aminoethyl acrylate, and aminoethyl methacrylate. (3) 40 to 95% by weight of ethylene, general formula (A) ▲ Numerical formula, chemical formula, table, etc. ▼ (A) (In the formula, R_1 is hydrogen or a methyl group, R_2 and R
_3 is an alkyl group having 1 to 4 carbon atoms, n is an integer from 1 to 4), contains 60 to 5% by weight of an aminoalkyl acrylate comonomer, and has a number average molecular weight of 5,000 to 50, A method for absorbing iron and cobalt ions, characterized in that an ethylene copolymer having a pH of 0.000 is used as an absorber for iron and cobalt ions at a pH of 2.1 or less.