JP5114704B2 - Method for separating metal and method for recovering metal - Google Patents

Description

  The present invention relates to a novel metal separation method for adsorbing mercury in a solution with polythioamide. The present invention also relates to a novel metal recovery method in which mercury adsorbed on the polythioamide is desorbed and recovered by a reducing agent.

  Mercury is a toxic element and when it is released into the environment, it is bioconcentrated via the food chain and can consequently adversely affect human health. Therefore, mercury is strictly regulated from the offices to the environment.

  Currently, functional polymers such as various chelate resins and ion exchange resins are used to remove mercury contained in factory wastewater. However, since such a functional polymer has low selectivity for mercury adsorption, other elements are often adsorbed simultaneously. Further, since mercury adsorbed on the functional polymer is generally difficult to desorb using an eluent or the like, the functional polymer after mercury adsorption is often disposed of in landfills.

  On the other hand, a method is also used in which a functional polymer adsorbed with mercury is heated at a high temperature of 800 ° C. or higher and the adsorbed mercury is recovered as mercury vapor. However, this method has a problem of processing cost, and in addition, it is difficult to reuse the adsorbent.

  As an attempt to overcome the above problem, a reusable functional polymer that can absorb and collect mercury and can elute mercury by using an acidic solution of hydrochloric acid has been prepared (for example, Patent Document 1). . However, it is difficult to recover mercury with high purity because elements other than mercury are adsorbed on the functional polymer and they are eluted together with mercury at the time of elution.

  On the other hand, there has been proposed a technique for recovering mercury as metallic mercury by adding an excessive reducing agent to a solid and liquid mercury-containing waste to form a reducing atmosphere, and reducing and vaporizing the mercury, followed by cooling (for example, Patent Document 2). This technique has an advantage that high-purity mercury can be obtained, but has a problem that the processing efficiency is lowered when the mercury content in the mercury-containing waste is low.

  Therefore, as an improvement, mercury-containing waste is placed in a reducing atmosphere, mercury is reduced and vaporized, collected as a mercury compound by the adsorbed material, and the adsorbed mercury is reduced again and then recovered as metallic mercury by cooling. A technique has been devised (for example, Patent Document 3). However, this technique has a problem that the operation is complicated.

  The inventors have announced the separation and recovery of metals such as palladium using polythioamide (for example, Non-Patent Documents 1 to 8).

JP-A-9-99238 JP 2001-11548 A Japanese Patent Laid-Open No. 2001-140026 Emi Sato, Jin Kawai, Shigehiro Kagaya, Takaki Kanbara, Satoshi Hasegawa, 1PB076 Heavy Metal Adsorption Properties of Polythioamide, The 79th Annual Meeting of the Chemical Society of Japan, March 2001 Emi Sato, Shigehiro Kagaya, Takaki Kanbara, Satoshi Hasegawa, Recovery of precipitation of heavy metals in organic effluent using 2PC-106 polythioamide, The 81st Annual Meeting of the Chemical Society of Japan, March 2002 Shigehiro Kagaya, Tomomi Makusa, Emi Sato, Takaki Kanbara, Satoshi Hasegawa, Development of selective recovery agent for valuable metals in waste liquid, Toyama National College of Technology, 9th Asian International Symposium on Ecotechnology-Toyama (ASET9), December 2002 Shigehiro Kagaya, Tomomi Makusa, Emi Sato, Takaki Kanbara, Satoshi Hasegawa, Recovery of palladium and nickel in organic effluents with 1PB-133 polythioamide, The 83rd Annual Meeting of the Chemical Society of Japan, March 2003 S. Kagaya, E. Sato, I. Masore, K. Hasegawa, and T. Kanbara, Polythioamide as a Collector for Valuable Metals from Aqueous and Organic Solutions, Chemistry Letters, Vol. 32, No. 7, pp. 622-623 (July 2003) Shigehiro Kagaya, Nobuhiro Kawai, Tomomi Makusa, Emi Sato, Takaki Kanbara, Satoshi Hasegawa, Elution of Palladium Adsorbed on P-92 Polythioamide: Application to Separation and Recovery of Palladium in Organic Waste Liquid, Toyama National College of Technology The 10th Asian International Symposium on Ecotechnology-Toyama (ASET10), November 2003 Shigehiro Kagaya, Erika Tanaka, Nobuhiro Kawai, Tomomi Makusa, Emi Sato, Takaki Kanbara, Satoshi Hasegawa, Separation of Palladium from Nickel and Platinum-Containing Solutions Association 4th Takayama Forum, November 26-27, 2004 Shigehiro Kagaya, Erika Tanaka, Nobuhiro Kawai, Tomomi Makusa, Emi Sato, Takaki Kanbara, Satoshi Hasegawa, Separation of Palladium from Organic Solution containing Nickel and Platinum, Toyama National College of Technology 11th Ecotechnology International Symposium on Japan-Toyama (ASET11), December 3-4, 2004

  However, no method for separating and recovering mercury in the solution has been reported.

The present invention has been made in view of such problems, and an object thereof is to provide a novel metal separation method.
Another object of the present invention is to provide a novel metal recovery method.

The separation of the new metal is solved by the following [ 7 ], and the recovery of the new metal is solved by the following [ 13].

[7] Mercury in the solution is adsorbed by the polythioamide represented by Chemical Formula 18, and any one other selected from the group consisting of iron, copper, zinc, manganese, lead, and cadmium is adsorbed in the solution. If metal coexist within the 0.01~5mmol / l If, adsorption rate to the Porichioamido of the other metals, the zinc is 0.2% or less, 0.06% or less in the cadmium The ratio of the adsorption rate of the other metal to the polythioamide to the adsorption rate of the mercury to the polythioamide is 0% for zinc. .002 Ri der below, cadmium is at 0.0006 or less, iron, copper, manganese, and lead is zero, a metal separation methods.

  [13] A metal recovery method in which mercury adsorbed by the polythioamide represented by chemical formula 18 is eliminated by tin (II) chloride.

According to the present invention [ 7 ], a novel metal separation method can be provided.
Further, according to this onset bright [13], it is possible to provide a method for recovering the novel metal.

  Hereinafter, the best mode for carrying out the present invention will be described.

  First, a method for adsorbing mercury in a solution with polythioamide will be described. The polythioamide can be represented by Chemical Formula 13:

Here, R ¹ and R ² represent a bifunctional aromatic unit, a bifunctional heterocyclic unit, or a bifunctional aliphatic hydrocarbon unit. A difunctional aromatic unit represents a difunctional phenylene, naphthylene, phenanthrylene, anthrylene, or biphenyl. It may have a substituent in which one or two hydrogen atoms are replaced with an alkyl group, an alkoxy group, a fluoro group, a chloro group, an ester group, an acyl group, or an amide group. A bifunctional heterocyclic unit represents a bifunctional pyridyldiyl, thienylene, furylene, pyrrolylene, or quinolinediyl. It may have a substituent in which one or two hydrogen atoms are replaced with an alkyl group, an alkoxy group, a fluoro group, a chloro group, an ester group, an acyl group, or an amide group. The bifunctional aliphatic hydrocarbon unit represents a linear or branched bifunctional aliphatic hydrocarbon having 2 to 10 carbon atoms. You may have a hetero atom of an oxygen atom, a sulfur atom, a nitrogen atom, a silicon atom, or a phosphorus atom between the carbon-carbon bonds of a hydrocarbon. A difunctional aromatic unit of phenylene or naphthylene may be included between the carbon-carbon bonds of the hydrocarbon.

Here, R ³ represents a hydrogen atom, an aliphatic hydrocarbon group, an aromatic substituent, or a heterocyclic substituent. The aliphatic hydrocarbon group represents a linear or branched aliphatic substituent having 1 to 8 carbon atoms. The aromatic substituent represents a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, or a biphenyl group. It may have a substituent in which one or two hydrogen atoms are replaced with an alkyl group, an alkoxy group, a fluoro group, a chloro group, an ester group, an acyl group, or an amide group. A heterocyclic substituent represents a pyridyl group, a thienyl group, or a furyl group. It may have a substituent in which one or two hydrogen atoms are replaced with an alkyl group, an alkoxy group, a fluoro group, a chloro group, an ester group, an acyl group, or an amide group.

Further, when R ² and R ³ are formed from an aliphatic hydrocarbon unit, they may be combined to form a cyclic compound.

  The polythioamide can be specifically represented by the chemical formula 14.

Here, R ¹ and R ² may be a bifunctional unit represented by Chemical Formula 15. N represents an integer of 2 to 10.

Here, R ³ includes a hydrogen atom or a substituent represented by Chemical Formula 16. N represents an integer of 0 to 7.

Further, when R ² and R ³ are bonded, a unit represented by Chemical Formula 17 in which a cyclic structure is formed can be mentioned.

  The addition amount of polythioamide is preferably in the range of 2 to 20000 mmol-unit / mmol-Hg as the amount of polythioamide unit (mmol-unit) per mercury amount (mmol-Hg). The addition amount of polythioamide is more preferably in the range of 20 to 2000 mmol-unit / mmol-Hg. When the addition amount is 2 mmol-unit / mmol-Hg or more, there is an advantage that 100% of mercury contained in the solution can be adsorbed. When the addition amount is 20 mmol-unit / mmol-Hg or more, this effect becomes more remarkable, and the time to reach 100% adsorption is also shortened. When the addition amount is 20000 mmol-unit / mmol-Hg or less, there is an advantage that it is economical. When the addition amount is 2000 mmol-unit / mmol-Hg or less, this effect becomes more remarkable.

  The pH of the solution is preferably in the range of 0.5-14. Further, the pH is more preferably in the range of 1.7 to 10.1. When the pH is 0.5 or more, there is an advantage that mercury can be adsorbed efficiently. When the pH is 1.7 or more, this effect becomes more remarkable. There exists an advantage that adsorption | suction of the other heavy metals which coexist can be suppressed as pH is 14 or less. When the pH is 10.1 or less, this effect becomes more remarkable.

  The stirring time of the solution is preferably in the range of 1 minute to 24 hours. The stirring time is more preferably in the range of 10 minutes to 2 hours. When the stirring time is 1 minute or more, there is an advantage that 70% or more of mercury in the solution can be adsorbed. This effect becomes more remarkable when the stirring time is 10 minutes or more. When the stirring time is 24 hours or less, there is an advantage that the mercury adsorption and collection time can be shortened. This effect becomes more remarkable when the stirring time is 2 hours or less.

  The concentration of mercury is preferably in the range of 0.0005 to 5 mmol / l. Further, the mercury concentration is more preferably in the range of 0.001 to 0.1 mmol / l. When the concentration of mercury is 0.0005 mmol / l or more, there is an advantage that mercury in the solution can be quickly adsorbed and recovered. This effect becomes more remarkable when the concentration of mercury is 0.001 mmol / l or more. When the concentration of mercury is 5 mmol / l or less, there is an advantage that mercury can be rapidly adsorbed and collected. This effect becomes more remarkable when the concentration of mercury is 0.1 mmol / l or less.

  The metal separation method of the present invention can be applied when a metal other than mercury coexists. Examples of other metals include copper, iron, zinc, manganese, lead, cadmium, chromium, cobalt, nickel, sodium, potassium, magnesium, and calcium.

  The molar ratio of other metals to mercury in the solution is preferably in the range of 0.1 to 1000. The molar ratio of the other metal to mercury is more preferably in the range of 1 to 500. When the molar ratio of the other metal is 0.1 or more, there is an advantage that the efficiency in separation of mercury and the other metal is improved and only mercury can be separated without mixing with the other metal. When the molar ratio of other metals is 1 or more, this effect becomes more remarkable. When the molar ratio of the other metal is 1000 or less, it is possible to prevent a decrease in the adsorption rate of mercury, and there is an advantage that mercury can be separated by suppressing mixing of other metals in a practical range. When the molar ratio of other metals is 500 or less, this effect becomes more remarkable.

  The adsorption of mercury in solution by polythioamide is due to the coordination ability of the thiocarbonyl unit of the thioamide group.

  In the method for recovering mercury adsorbed on polythioamide, it is preferable to add a tin (II) compound to a solution containing polythioamide. Examples of the tin (II) compound include tin (II) chloride, tin (II) bromide, and tin (II) fluoride. In particular, tin (II) chloride is preferable, and for example, tin (II) chloride dihydrate is easily available and preferable.

In addition, as a method for recovering mercury, there is a method of adding a borohydride compound instead of a tin (II) compound to a solution containing polythioamide.
be able to.

  The number of times the polythioamide is reused is preferably in the range of 100 times or less. When the number of reuses is 100 or less, there is an advantage that mercury can be separated and recovered with high efficiency, and polythioamide can be recycled as a mercury scavenger in a practical range.

  EXAMPLES Hereinafter, the present invention will be described by way of examples. However, the present invention is not construed as being limited thereto, and various modifications and changes can be made based on the knowledge of those skilled in the art without departing from the scope of the present invention. Modifications and improvements can be added.

Reference Example 1 [Synthesis of polythioamide]
Here, polythioamide was synthesized based on the method described in the following references.

  References: T. Kanbara, Y. Kawai, K. Hasegawa, H. Morita, T. Yamamoto, J. Polym. Sci.: PartA: Polym. Chem. Vol. 39, 3739-3750 (2001)

Hexamethylenediamine 0.2324 g (2 mmol) and sulfur 0.1601 g (5 mmol) were placed in a 50 ml Schlenk tube under a nitrogen atmosphere, DMAc (dehydrated) 10 ml was added, and the mixture was stirred at room temperature for 10 minutes. To this reaction solution, 0.2683 g (2 mmol) of isophthalaldehyde was added and stirred at 115 ° C. for 6 hours. The reaction solution was added to an Erlenmeyer flask containing 300 ml of methanol and washed. The produced precipitate was collected by suction filtration, redissolved in 10 ml of DMAc, and washed again with 300 ml of methanol. Thereafter, the precipitate collected by suction filtration was dissolved in 5 ml of DMF. This solution was passed through a glass filter to remove unreacted sulfur, and then the DMF solution was concentrated to about 3 ml. After concentration, this DMF solution was reprecipitated in 300 ml of methanol, and the precipitate was collected by suction filtration. This precipitate was redissolved in 5 ml of DMF, concentrated to about 3 ml, and then reprecipitated in 300 ml of methanol. The produced precipitate was collected by suction filtration and then dried under vacuum to obtain the desired polythioamidated compound 18. The target compound was beige and was obtained in a yield of 0.373 g and a yield of 67%.
The polythioamide unit amount per 1 g of polythioamide is 3.591 (mmol-unit / g). The polythioamide unit amount is the number of repeating units contained in 1 g of polymer expressed in terms of the number of molecules (mole unit) when the repeating unit constituting the polythioamide is regarded as one molecule.

Example 1 [Effect of pH on mercury adsorption]
Mercury (Hg (II)) solutions (2 mg / l) with different pH were prepared by adding 1 M NaOH and 1 M HNO ₃ to the mercury nitrate solution. The pH value of each solution was in the range of 1.7 to 10.1. 5 ml of each solution was collected, 5 mg of polythioamide was added, and the mixture was stirred at room temperature for 1 hour. Thereafter, the mixture was filtered using a disposable filter having a pore size of 0.2 μm, and the residual mercury concentration in the filtrate was measured by reductive vaporization-atomic absorption analysis to determine the residual concentration. The adsorption rate of Hg (II) was determined from the residual concentration and the initial concentration before stirring. As a result, as shown in FIG. 1, 100% of Hg (II) could be adsorbed from any pH solution. Therefore, polythioamide can collect mercury without being affected by pH. The adsorption rate is a percentage of the amount of mercury adsorbed on the polythioamide with respect to the amount of mercury contained in the solution before adsorption.

Example 2 [Influence of stirring time]
5 mg of polythioamide was added to 5 ml of 1-10 mg / l mercury nitrate solution and stirred at room temperature. After stirring, the mixture was filtered using a disposable filter having a pore size of 0.2 μm, and the residual mercury concentration in the filtrate was measured by reduction vaporization-atomic absorption analysis. The results are shown in Table 1. From these results, the polythioamide of the present invention can adsorb mercury at 76% or more 1 minute after starting stirring and 100% after 60 minutes at any concentration.

Example 3 [Influence of coexisting elements]
To 5 ml of a solution (pH 1-3) containing mercury (A: 2 mg / l = 0.01 mmol / l) and copper, iron, zinc, manganese, lead or cadmium (B: 0.01-5.0 mmol / l) 5 mg of polythioamide was added and stirred at room temperature for 1 hour. Then, it filtered using the disposable filter with the hole diameter of 0.2 micrometer, and the mercury residual density | concentration in a filtrate was measured by the reductive vaporization-atomic absorption analysis. The results are shown in Table 2. Even when any of the elements coexisted, polythioamide adsorbed 100% of mercury. Further, the adsorption rate of the coexisting element to the polythioamide is 0.2% for the coexisting element Zn (initial concentration 1 mmol / l and 5 mmol / l), and 0.06 for the coexisting element Cd (initial concentration 5 mmol / l). % Was 0% for all coexisting elements except for%. From these results, the polythioamide of the present invention can collect mercury even if these elements coexist.

Example 4 [Reduction Vaporization Desorption Experiment of Hg (II) Adsorbed on Polythioamide]
5 mg of polythioamide was added to 5 ml of a 5 mg / l mercury nitrate solution and stirred for 1 hour. After standing, the supernatant was collected, and the residual mercury concentration was measured by reductive vaporization-atomic absorption analysis. Next, 5 ml of a 15% w / v tin (II) chloride solution (0.5 MH ₂ SO ₄ ) was added to the solution containing the polythioamide that was allowed to stand, and the adsorbed mercury was reduced and vaporized by aeration for 1 hour. The vaporized mercury was collected with a permanganic acid solution, and after the reduction, the mercury concentration in the permanganic acid solution was measured by reduction vaporization-atomic absorption analysis.
As a result, the adsorption rates were all 100%, and the recovery rate of mercury that had been reduced, desorbed and desorbed was 108 ± 10% (expressed as an average value ± standard deviation in five experiments). The reason why the recovery rate exceeds 100% is due to a measurement error or the like. Therefore, by this operation, mercury adsorbed on the polythioamide of the present invention can be reductively vaporized and desorbed. The recovery rate is the percentage of mercury recovered by reductive vaporization with respect to the amount of mercury contained in the solution before adsorption.

Example 5 [Recyclability of polythioamide]
In the same manner as in Example 4, a mercury adsorption rate and a recovery rate by reduction vaporization were determined using a 1 mg / l mercury nitrate solution. The polythioamide after reductive vaporization was recovered using a disposable filter having a pore size of 0.2 μm and vacuum-dried. Thereafter, the dried polythioamide was placed in a sample bottle and weighed. Using this polythioamide, adsorption and desorption experiments were performed again. This operation was repeated. The results are shown in Table 3. In at least 5 repetitive uses, the polythioamide of the present invention produced mercury with an adsorption rate of 100% and a recovery rate of 94 to 126% by reductive vaporization desorption. In some results, the recovery rate was found to exceed 100%. This was due to elution of mercury remaining on the polythioamide in the elution step, measurement errors, and the like.

  From the above, according to this example, even in a solution in which other heavy metals coexist with mercury, only mercury can be adsorbed and collected quantitatively and quantitatively separated with a tin (II) chloride solution. It can be recovered.

  According to the present invention, mercury can be efficiently and selectively separated from mercury waste liquor in which heavy metals coexist. Moreover, it can collect | recover after isolate | separating.

It is a figure shown about the influence of pH which acts on mercury adsorption.

Claims (2)

The polythioamide represented by Chemical Formula 1 adsorbs mercury in the solution,
Wherein the solution, iron, copper, zinc, manganese, if lead or any of one other metal selected from the group consisting of cadmium, coexist within the 0.01~5mmol / l,
The adsorption rate of the other metal to the polythioamide is 0.2% or less for zinc, 0.06% or less for cadmium, and 0% for iron, copper, manganese, and lead.
And, for the adsorption rate to the Porichioamido of the mercury, the ratio of the adsorption rate to the Porichioamido of the other metals state, and are 0.002 or less in the zinc, the cadmium is at 0.0006 or less, iron Separation of metals that are zero for copper, manganese, and lead .

A method for recovering a metal, wherein mercury adsorbed by the polythioamide represented by Chemical Formula 2 is eliminated by tin (II) chloride.

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