JP4872073B2 - Adsorbent with selective adsorptivity to silver and lead ions - Google Patents

Description

  The present invention relates to an adsorbent exhibiting selective adsorptivity to silver ions and lead ions. More specifically, the present invention relates to an adsorbent that selectively adsorbs silver ions and lead ions having a structure in which organic quaternary ammonium ions are intercalated into layered manganese oxide.

  It is important to collect metals discharged as a result of industrial activities from the viewpoint of environmental conservation and effective use of resources.

  For example, the regulation of silver contained in wastewater discharged from industrial fields such as the photographic industry and the plating industry has become increasingly stringent in recent years, and a technology for efficiently recovering silver from wastewater is desired. ing.

  Lead is a heavy metal that causes various damages to the human body including the brain and nerves, and in addition to industrial wastewater and environmental water, contamination of drinking water by lead eluted from the lead pipe of waterworks has become a problem.

  Various techniques have been developed for silver recovery. For example, Patent Document 1 uses a compound containing silicon as a silver ion or sodium ion adsorbent, and Patent Document 2 uses a polymer having a sulfur atom that can coordinate with silver. Patent Document 3 describes electrolytic treatment of a photographic developer.

Various techniques have also been developed for the recovery of lead. For example, Patent Document 4 and Patent Document 5 disclose that the lead is precipitated and separated on the water phase side using an oil / water phase separation phenomenon, and Patent Document 6 discloses that a solution containing lead ions is a phosphate group, a phosphine group. And / or contacting with a chelating ion exchange resin having a phosphonic group to adsorb lead ions to the resin.
JP 2001-205080 A Japanese Patent Laid-Open No. 7-60243 Japanese Unexamined Patent Publication No. 7-97696 JP-A-10-175915 Japanese Patent Laid-Open No. 10-347302 Japanese Patent Laid-Open No. 8-10863

  In the adsorbent described in Patent Document 1, sodium ions contained in normal water such as tap water are adsorbed at the same time, and there is a difficulty in increasing the adsorption efficiency of silver ions. The same applies to the adsorbent described in Patent Document 2, and a metal having an affinity for sulfur atoms is adsorbed simultaneously. In the electrolytic treatment described in Patent Document 3, the apparatus becomes large, and the recovery conditions must be controlled by the potential or the like.

  In the methods described in Patent Document 4 and Patent Document 5, it is necessary to separate the oil phase and the water phase, and to further remove lead as a solid content by centrifugation or the like. In the method described in Patent Document 6, an expensive chelating ion exchange resin is required.

  The inventors of the present invention manufactured a layered manganese oxide thin film intercalated with the organic quaternary ammonium ion by electrochemically oxidizing a divalent manganese compound in the presence of the organic quaternary ammonium ion. The invention of the method has been made and a patent application has been filed as Japanese Patent Application No. 2004-265681. According to the invention of Japanese Patent Application No. 2004-265681, a layered manganese oxide thin film intercalated with organic quaternary ammonium ions can be easily produced without requiring a complicated process.

The inventors of the present invention, was further continued research, layered manganese oxide quaternary ammonium ion intercalated organic, as well as obtaining the knowledge that a selective adsorption for a particular metal ion, Based on the above-mentioned actual situation regarding the recovery of silver and lead, the present invention was devised as a result of earnest research. Waste water containing silver, which is a precious metal and useful, waste water and tap water containing lead harmful to the human body From the above, it is an object to provide an adsorbent capable of selectively adsorbing silver and lead without adsorbing sodium, calcium and the like usually mixed in waste water containing silver and lead.

In order to solve the above problem, an adsorbent exhibiting selective adsorption property to silver ions and lead ions of the present invention, the constitution of the following (1) to (4).

(1) A layered manganese oxide obtained by intercalating polydiallyldimethylammonium on the anode by electrochemical oxidation using an electrolytic solution containing a divalent manganese compound and polydiallyldimethylammonium cation. Is an adsorbent exhibiting selective adsorptivity to silver ions and lead ions.

(2) In the above (1), the polydiallyldimethylammonium cation is an adsorbent that exhibits selective adsorptivity to silver ions and lead ions having a molecular weight of 400,000 to 500,000.

(3) The concentration of the divalent manganese compound present in the electrolytic solution is 0.1 mmol to 1 mol, and the polydiallyldimethylammonium cation is 0.1 mmol to 1 mol as the nitrogen atom concentration. It is an adsorbent exhibiting selective adsorptivity to silver ions and lead ions described in 1) or (2).

(4) The electrochemical oxidation is performed at a voltage of 0.8 to 1.2 volts with respect to the silver / silver chloride reference electrode, according to any one of (1) to (3) above It is an adsorbent that exhibits selective adsorptivity to silver ions and lead ions.

  Since the present invention is configured as described above, the following effects can be obtained.

  That is, since the adsorbent of the present invention exhibits high selective adsorptivity to silver ions and lead ions, waste water containing silver, which is a noble metal and useful, waste water containing tap water harmful to human bodies, tap water, etc. Therefore, silver ions and lead ions can be adsorbed without adsorbing sodium ions, calcium ions, etc. normally mixed in waste water containing silver ions and lead ions.

  Manganese is abundant in nature, has low toxicity and is safe, is rich in divalent manganese compounds as raw materials, has low toxicity and is inexpensive, and is involved in the production of the adsorbent of the present invention. There is little risk of harming the surrounding environment. The adsorbent of the present invention can be produced by electrochemically oxidizing a divalent manganese compound in the presence of organic quaternary ammonium ions, and the electrochemical oxidation is easily performed at room temperature. The manufacturing cost is low and the unit price of the adsorbent can be reduced.

  Since the adsorbent of the present invention is in the form of a thin film, it is compact and not bulky, and can be formed as a thin film on the electrode. By selecting the size of the electrode, a thin-film adsorbent having a desired size is obtained. be able to.

  In addition, silver ions and lead ions recovered by the adsorbent of the present invention formed as a thin film on the electrode can be electrochemically reduced as silver particles and lead particles by energizing the electrode. It is also easy. And the waste water from which silver ions and lead ions are recovered can be discharged as it is or by applying an appropriate treatment.

  As described above, according to the adsorbent of the present invention, silver ions and lead ions can be easily and efficiently recovered from waste water discharged as a result of industrial activities. The collected wastewater can be discharged, which is useful for environmental conservation and resource reuse.

  Further, according to the adsorbent of the present invention, the same can be said for selective recovery of silver ions and lead ions contained in environmental water.

  And, by bringing the adsorbent of the present invention into contact with tap water, minerals such as sodium, potassium, magnesium and calcium are not adsorbed from tap water that people drink every day, and lead ions can be easily and efficiently produced at low cost. It is possible to remove the harmful effects caused by the accumulation of lead in the human body.

  The best mode for carrying out the invention will be described below, and the present invention will be described in more detail. Of course, the present invention is not limited to the following embodiments.

First, an organic quaternary ammonium ion used in the present invention, in particular , an electrolytic solution containing a polydiallyldimethylammonium cation and a divalent manganese compound is electrochemically oxidized, and the organic quaternary ammonium ion is intercalated. The principle of forming the layered manganese oxide will be described.

When electrochemically deposited manganese oxide of submicron to micron order is deposited on the electrode substrate by anodic oxidation of Mn ²⁺ ions in the presence of organic quaternary ammonium, the deposited manganese is in the form of manganic acid and is negative. The organic quaternary ammonium ions coexist in a thin layer. Next, precipitation of manganese oxide occurs again on the manganese oxide whose surface is covered with organic quaternary ammonium ions, and a layered manganese oxide covered with manganese oxide and intercalated with organic quaternary ammonium ions is formed. It is formed. The thickness of the layered manganese oxide can be controlled by the amount of electricity passing through.

  In order to obtain uniform manganese oxide precipitation, a voltage of 0.8 to 1.2 volts, preferably 0.95 to 1.05 volts, is maintained with respect to the silver / silver chloride reference electrode. It is necessary to perform voltage control. As a result, it is expected that divalent manganese is oxidized and precipitated as trivalent and tetravalent manganese mainly by the following reaction at the anode.

（但し、Ａ^＋は有機第４アンモニウムイオン）
マンガン酸化物薄層と有機第４アンモニウムイオンの薄層の交互の形成が繰り返されることにより、マンガン酸化物薄層と有機第４アンモニウムイオン薄層との繰り返し構造物、すなわち、積層物を得ることができる。

(However, A ⁺ is an organic quaternary ammonium ion)
By repeating the alternate formation of the manganese oxide thin layer and the organic quaternary ammonium ion thin layer, a repetitive structure of the manganese oxide thin layer and the organic quaternary ammonium ion thin layer, that is, a laminate is obtained. Can do.

Each layer of the layered manganese oxide intercalated with the obtained organic quaternary ammonium ions is generally submicron to micron order because the thin layer of organic quaternary ammonium ions generally formed is a monomolecular layer. The interlayer distance can be controlled by the size of the organic quaternary ammonium ions. Organic quaternary ammonium ions are intercalated between the layered manganese oxides in the order of sub-nanometers to nanometers, and the organic quaternary ammonium cations are fixed by ionic bonds with the manganese oxides. It is. The general explanation has been given as the organic quaternary ammonium ion, but the same applies to polydiallyldimethylammonium.

  The form of the electrolytic cell used for electrolytic oxidation is not particularly limited, and various types of electrolytic cells conventionally used for electrolytic oxidation are used.

  When the manganese oxide obtained by electrolytic oxidation is peeled off from the anode of the electrolytic cell and used, there is no particular problem as long as the anode is a conductive substance, but platinum or nickel is generally preferable.

  Further, there is no particular problem if the counter electrode (cathode) is also a conductive material, but generally iron, copper, nickel, platinum or the like is used.

  The size of the anode or the like is determined as necessary.

  In general, electrolysis is preferably performed at room temperature to about 40 ° C. By setting the electrolysis temperature to 60 to 80 ° C., the deposition rate can be increased, but if it is too high, the precipitation surface of the manganese oxide becomes rough, which is not preferable. In addition, heat energy is required to maintain the electrolysis temperature.

  In addition, the number of stacks can be increased by increasing the electrolysis time. However, if the electrolysis time is too long, the thickness of the manganese oxide increases and the stacked state tends to be disturbed.

  The divalent manganese compound used in the present invention is not particularly limited as long as it is a divalent manganese compound that is soluble in the electrolytic solution and is electrolytically oxidized, but generally, a salt of an inorganic acid. For example, manganese sulfate, manganese chloride, manganese nitrate, manganese carbonate and the like. Organic manganese compounds such as manganese ammonium oxalate and potassium manganese oxalate can also be used. Manganese sulfate is preferred because of its availability.

  The concentration of divalent manganese in the electrolytic solution is not particularly limited, but is generally 0.1 to 1 mol, preferably 1 to 100 mmol. If it is less than 0.1 mmol, the electric resistance of the electrolytic solution is increased due to its dilution, and undesirable phenomena such as electrolysis of other components such as water increase. On the other hand, when the amount exceeds 1 mol, the precipitation of manganese oxide on the anode is lacking in uniformity.

Lupo lysine diallyldimethylammonium cation put to the present invention is a structure shown in Chemical Formula 2.

ポリジアリルジメチルアンモニウムカチオンの対イオンは、水酸化物であってもよいが、塩化物、硝酸塩、硫酸塩等の可溶性化合物として用いられる。

The counter ion of the polydiallyldimethylammonium cation may be a hydroxide, but is used as a soluble compound such as chloride, nitrate, sulfate.

  The molecular weight of the polydiallyldimethylammonium cation is preferably 400,000 to 500,000, but is not limited thereto.

The polydiallyldimethylammonium cation used in the present invention is generally used in a range of 0.1 to 1 mol, preferably 1 to 100 mmol, as a nitrogen atom concentration in the electrolyte, but is not limited thereto. .
(Example)
Next, examples of the present invention will be described together with comparative examples to explain in more detail.

50 mL of an aqueous solution containing 5.6 mM polydiallyldimethylammonium chloride (PDDACl: (C8H16N ⁺ Cl ⁻ ) n; molecular weight of about 400,000 to 500,000) and manganese sulfate (MnSO 4) 2 mM is placed in a beaker-type cell. The electrolyte was used. The electrolytic solution was made a nitrogen atmosphere by bubbling nitrogen gas. The liquid temperature was 25 ° C. A platinum plate (1 cm × 1 cm × 0.5 mm thickness) was used as a working electrode, and a potential of +1.0 V (expressed as a potential with respect to a silver / silver chloride electrode) was applied to the platinum plate. The electrolysis time was 60 minutes. A platinum plate was used for the counter electrode.

  By this operation, a brown thin film was formed on the platinum plate. The platinum plate covered with the brown thin film was taken out of the electrolytic solution, washed with distilled water, and then vacuum-dried. FIG. 1 is an X-ray photoelectron spectroscopy (XPS) spectrum of a thin film formed on a platinum plate. Peaks due to electronic transitions of Mn2p, O1s, N1s, and C1s were observed near 650, 530, 400, and 280 eV, respectively. Here, the C1s peak is usually not considered because of the contribution of hydrocarbon contamination in the XPS apparatus. The Mn2p and O1s peaks are derived from manganese oxide. The N1s peak was attributed to the ammonium group of PDDA (polydiallyldimethylammonium), and it was found that the obtained thin film was a complex of manganese oxide and PDDA. Note that manganese in the thin film from XPS was in a trivalent and tetravalent mixed valence state. Further, no chlorine was detected in the XPS spectrum, and it was found that PDDA exists as a cation, not a chloride. In other words, a negatively charged manganese oxide layer due to the presence of trivalent manganese and a positively charged PDDA ion form an ion pair by electrostatic interaction.

  FIG. 2 is an X-ray diffraction (XRD) pattern of a PDDA / manganese oxide thin film formed on a platinum plate. In addition to the diffraction peak due to platinum as a substrate, diffraction peaks peculiar to the layer structure appear at 2θ = 9.1, 18.2, and 27.3 °, and from the diffraction peak 2θ = 9.1 from the 001 plane, Bragg Using the equation (nλ = 2dsinθ), the layer spacing was calculated to be 0.97 nm.

  The observed layer spacing corresponds to a structure intercalated so that the polymer chain of PDDA is parallel to the surface of the manganese oxide sheet.

  The brown thin film formed on the platinum plate electrode in Example 1 was immersed in a 0.1 M silver nitrate aqueous solution for 12 hours. Thereafter, the platinum plate was taken out from the solution, washed with distilled water, dried in vacuum, and the XPS spectrum was measured. The results are shown in FIG. In FIG. 3, the peak derived from silver appears, while the N1s peak derived from the ammonium group of PDDA has completely disappeared. This indicates that the silver ions in the aqueous solution are replaced with the PDDA ions in the layer and are collected in the thin film.

The brown thin film formed on the platinum plate electrode in Example 1 was immersed in a 0.1 M lead nitrate aqueous solution for 12 hours. Thereafter, the platinum plate was taken out from the solution, washed with distilled water, dried in vacuum, and the XPS spectrum was measured. The results are shown in FIG. In FIG. 4, a peak derived from lead appears, while an N1s peak derived from the ammonium group of PDDA has completely disappeared. This indicates that the lead ions in the aqueous solution are replaced with the PDDA ions in the layer and are collected in the thin film.
[Comparative Example 1]

The brown thin film formed on the platinum plate electrode in Example 1 was immersed in a 0.1 M nitric acid aqueous solution for 12 hours. Thereafter, the platinum plate was taken out from the solution, washed with distilled water, dried in vacuum, and the XPS spectrum was measured. The results are shown in FIG.
[Comparative Example 2]

The brown thin film formed on the platinum plate electrode in Example 1 was immersed in a 0.1 M aqueous potassium chloride solution for 12 hours. Thereafter, the platinum plate was taken out from the solution, washed with distilled water, dried in vacuum, and the XPS spectrum was measured. The results are shown in FIG.
[Comparative Example 3]

The brown thin film formed on the platinum plate electrode in Example 1 was immersed in a 0.1 M cobalt nitrate aqueous solution for 12 hours. Thereafter, the platinum plate was taken out from the solution, washed with distilled water, dried in vacuum, and the XPS spectrum was measured. The results are shown in FIG.
[Comparative Example 4]

  The brown thin film formed on the platinum plate electrode in Example 1 was immersed in a 0.1 M magnesium nitrate aqueous solution for 12 hours. Thereafter, the platinum plate was taken out from the solution, washed with distilled water, dried in vacuum, and the XPS spectrum was measured. The results are shown in FIG.

The intensity of the N1s peak in FIG. 5 was substantially the same as that before dipping in the aqueous solutions of Comparative Examples 1 to 4. In addition, no peak derived from the corresponding cation (H ⁺ , K ⁺ , Co ²⁺ , Mg ²⁺ ) was observed. This indicates that in Comparative Examples 1 to 4, each cation in the aqueous solution is not substituted with the PDDA ions in the layer and is not adsorbed in the thin film.

From Examples 2 and 3 and Comparative Examples 1 to 4, the PDDA / manganese oxide thin film prepared in Example 1 does not adsorb H ⁺ , K ⁺ , Co ²⁺ , Mg ^2+, etc. in the aqueous solution, This indicates that lead ions can be recovered with high selectivity, and is judged to be effective as an adsorbent exhibiting selective adsorptivity to silver ions and lead ions.

2 is an X-ray photoelectron spectroscopy (XPS) spectrum of a thin film formed on a platinum plate in Example 1. FIG. 2 is an X-ray diffraction (XRD) pattern of a thin film formed on a platinum plate in Example 1. FIG. It is an X-ray photoelectron spectroscopy (XPS) spectrum after the thin film formed on the platinum plate in Example 1 was immersed in a 0.1 M silver nitrate aqueous solution. It is an X-ray photoelectron spectroscopy (XPS) spectrum after the thin film formed on the platinum plate in Example 1 was immersed in a 0.1M lead nitrate aqueous solution. The thin film formed on the platinum plate in Example 1 was (a) 0.1 M nitric acid aqueous solution, (b) 0.1 M potassium chloride aqueous solution, (c) 0.1 M cobalt nitrate aqueous solution, (d) 0.1 M magnesium nitrate. It is a X-ray photoelectron spectroscopy (XPS) spectrum of each thin film after being immersed in an aqueous solution.

Claims (4)

It is characterized by comprising a layered manganese oxide obtained by intercalating polydiallyldimethylammonium on an anode by electrochemical oxidation using an electrolytic solution containing a divalent manganese compound and polydiallyldimethylammonium cation. Adsorbent that selectively absorbs silver and lead ions. The adsorbent having a selective adsorptivity to silver ions and lead ions according to claim 1 , wherein the polydiallyldimethylammonium cation has a molecular weight of 400,000 to 500,000 . The concentration of the divalent manganese compound present in the electrolyte is 0.1 mmol to 1 mol, and the polydiallyldimethylammonium cation is 0.1 mmol to 1 mol as the nitrogen atom concentration. Adsorbent that selectively adsorbs silver and lead ions. 4. The silver ion and lead ion according to claim 1, wherein the electrochemical oxidation is performed at a voltage of 0.8 to 1.2 volts with respect to a silver / silver chloride reference electrode. 5. An adsorbent that exhibits selective adsorption properties.

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