JPH10273793A - Method for removing harmful heavy metal from liquid absorbent containing harmful heavy metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the electrodeposition of a heavy metal on an electrode from a liq. absorbent. SOLUTION: A liq. absorbent 4 contg. the harmful heavy metal transferred from a waste gas 1 when the waste gas 1 is cleaned is introduced into an electrolytic cell 9. The electrolytic cell 9 is divided into a cathode compartment 12 and an anode compartment 14. A potential is applied between a negative electrode 13 set in the cathode compartment 12 and a positive electrode 15 set in the anode compartment 14 to deposit the heavy metal in the liq. absorbent on the negative electrode 13. A surfactant 19 is added to the cathode compartment 12 of the electrolytic cell 9 to facilitate the electrodeposition of the heavy metal on the negative electrode 13, and a dense deposit is obtained on the electrode surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for cleaning exhaust gas from a melting furnace that melts fly ash and incinerated ash generated when incinerating municipal waste, discarded household appliances, shredder dust of automobiles and the like. The present invention relates to a method for removing harmful heavy metals transferred to an absorbing solution from the absorbing solution.

[0002]

2. Description of the Related Art When shredder dust such as municipal waste and discarded household appliances is incinerated in an incinerator, fly ash or incinerated ash discharged from the incinerator contains harmful heavy metals such as lead. Therefore, this is melted in a melting furnace, and the exhaust gas generated when the melting processing is performed in the melting furnace is washed,
It has been practiced to remove and recover harmful heavy metals transferred from exhaust gas into the absorbent used for the washing.

As an example, as shown in FIG. 2, fly ash and incinerated ash a discharged from an incinerator are introduced into a melting furnace b for melting, and exhaust gas c from the melting furnace b is sent to an absorption tower d. Into the circulation tank e together with the absorption liquid, the absorption liquid containing the heavy metal is further introduced into the solid-liquid separator f to perform solid-liquid separation. A part of the absorbing solution is circulated to the spray device g of the absorption tower d, and the absorbing solution containing the heavy metal filtered or separated by the solid-liquid separator f is supplied to an electrolytic cell as a heavy metal separation and recovery device h, +
A method has been proposed in which an ionized heavy metal is recovered by electrodeposition on a negative electrode (Japanese Patent Application No. 7-45967).
issue). Incidentally, i is a sludge transfer means for transferring the sludge collected during filtration by the solid-liquid separator f into the melting furnace b.

[0004]

However, in the heavy metal recovery system proposed above, the heavy metal can be attached to the electrode in an electrolytic cell as a heavy metal separation and recovery apparatus. Is what you can do.

The present invention is intended to take the above-mentioned proposal one step further, and to attempt to finely deposit the heavy metal on the electrode surface from the absorption liquid containing the target heavy metal.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an absorbing solution containing harmful heavy metals transferred from an exhaust gas by washing exhaust gas discharged from a refuse treatment facility by contacting the exhaust gas with the absorbing solution. Is placed in an electrolytic cell, and when a heavy metal is deposited on the negative electrode from the absorbing solution containing the heavy metal by applying a potential between the negative electrode and the positive electrode provided in the electrolytic cell, The method is to add a surfactant.

[0007] When a surfactant is added, the electrodeposition of heavy metals in the absorbing solution to the negative electrode is improved, and dense deposition is obtained on the electrode surface.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. As in the case shown in FIG.
Is put into the absorption tower 2, washed by contacting with the absorbing liquid ejected from the spray device 3, and the absorbing liquid 4 containing harmful heavy metals from the exhaust gas 1 is transferred to the circulation tank 5, A part of the liquid such as a clear liquid is circulated to the spray device 3 by a circulation pump 6 and a circulation line 7, and the absorption liquid 4 is transferred from a circulation tank 5 to a solid-liquid separator 8, where it is filtered or separated. In the configuration in which the absorbent 4 containing the heavy metal is supplied from a supply pipe 10 to an electrolytic cell 9 as a heavy metal separation and recovery device, a porous semipermeable membrane 11 is provided in the electrolytic cell 9. By installing the negative electrode 13 on one side as the cathode chamber 12, installing the positive electrode 15 on the other side as the anode chamber 14, and connecting both electrodes 13 and 15 to a DC power supply 16,
An electric potential is applied between the negative electrode 13 and the positive electrode 15 by power supply, and the cathode chamber 12 in which the negative electrode 13 is installed is further provided.
Is connected to a surfactant supply pipe 17, and the absorbent 4 containing heavy metals from the solid-liquid separator 8 is supplied to the cathode chamber 12 of the electrolytic cell 9.
To the cathode chamber 12 and supply the absorbing solution having no accumulation of heavy metal to the cathode chamber 12.
Then, the liquid is returned to the circulation tank 5 through the return pipe 18 so that the absorbent can be reused in the system.

In the present invention, a nonionic surfactant is used as the surfactant 19 supplied to the electrolytic cell 9 through the surfactant supply pipe 17, and a polyoxyalkylene condensate is particularly preferable. Examples thereof include polyethylene glycol, polyethylene glycol / polypropylene glycol block polymer, fatty acid alcohol / alkylene oxide ether, aromatic alcohol / alkylene oxide ether, and aliphatic amine / alkylene oxide adduct. Also, using a carbon electrode for the positive electrode 15 and a stainless steel plate for the negative electrode 13,
Electrolysis is performed at 0.5 to 5 A / dm ² .

Now, the absorbing solution 4 containing the heavy metal from the solid-liquid separator 8 is supplied to the cathode chamber 12 in the electrolytic cell 9 and the negative electrode 13 is supplied.
When a potential is applied between the negative electrode 13 and the positive electrode 15, the + ionized heavy metal is electrodeposited on the surface of the negative electrode 13. At this time, when a nonionic surfactant 19 is added as an organic additive from the supply pipe 17 to the absorbing solution in the cathode chamber 12 of the electrolytic cell 9, the nonelectrolytic surfactant 19 can be densely electrodeposited on the surface of the negative electrode 13.
It can be collected as a metal film on the surface of the negative electrode 13.

When the potential applied between the negative electrode 13 and the positive electrode 15 is changed, a heavy metal corresponding to the potential can be selectively deposited on the negative electrode 13 and adhered thereto. By adding the agent 19, the adhesion of the heavy metal to the negative electrode 13 can be improved.

When an aqueous solution containing a dilute concentration of metal ions is electrolyzed to deposit a metal on the negative electrode, the voltage required for the electrolysis depends on the type of the metal deposited on the negative electrode. The reference potential is 0.0
The deposition potentials of various metals at 0 V are as follows.

Cr: −0.74 V Fe: −0.44 V Ni: −0.25 V Pb: −0.13 V H ₂ : 0.00 V Cu: 0.34 V Metal deposition is a reaction on the negative electrode 13. Therefore, the smaller the potential is (the more negative the potential is), the higher the potential is required for electrolysis. Therefore, when only the intended heavy metal is to be selectively deposited on the negative electrode, by changing the potential, only the heavy metal having the potential can be sequentially deposited.

[0015]

EXAMPLES The results of experiments conducted by the present inventors on the effect of adding a surfactant will be described below. When the surfactant was not added to the electrolytic bath containing the halogen component, the metal deposited on the negative electrode was coarse. On the other hand, as a result of adding about 1 to 2% of the surfactant, dense precipitation was obtained on the surface of the negative electrode 13.

In the above experiment, the negative electrode was formed by using an alkanesulfonic acid such as methanesulfonic acid or alkanolsulfonic acid such as phenolsulfonic acid as a representative of an inorganic acid such as sulfuric acid or an organic acid. The surface of the deposited metal became dense.

[0017]

As described above, according to the method for removing harmful heavy metals from the harmful heavy metal-containing absorbing solution of the present invention, the absorbing solution containing heavy metals is put into the electrolytic cell, and the surfactant is added to the electrolytic cell. By applying a potential between the negative electrode and the positive electrode, heavy metals in the absorbing solution can be precipitated and collected on the negative electrode in the electrolytic cell, and at this time, are precipitated by the addition of a surfactant. Heavy metals can be densely electrodeposited on the electrode surface, and the commercial value can be increased.By changing the potential sequentially, only the target metal can be removed in order from the absorbing solution containing multiple types of metals. An excellent effect that it can be selectively deposited can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing conventional treatment of exhaust gas and removal of heavy metals from an absorbent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust gas 2 Absorption tower 4 Absorbing liquid 9 Electrolysis tank 11 Porous semipermeable membrane 13 Negative electrode 15 Positive electrode 19 Surfactant

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junya Nishino 1st place, Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawashima Harima Heavy Industries, Ltd. (72) Inventor Toshiyuki Suzuki 2-1-1 Toyosu, Koto-ku, Tokyo No. 1 Ishikawajima Harima Heavy Industries, Ltd., Tokyo No. 1 Factory (72) Inventor Takeyuki Miura 1178-3, Shimacho, Omiya City, Saitama Prefecture (72) Inventor Yu Seita 1-146-5 Inamachi Sakae Kita Adachi-gun, Saitama Prefecture

Claims (2)

[Claims] 1. An exhaust solution discharged from a refuse treatment facility, which is brought into contact with an absorbent and washed by bringing the exhaust gas into contact with the absorbent and containing a harmful heavy metal transferred from the exhaust gas into an electrolytic cell, and a negative electrode installed in the electrolytic cell. A harmful heavy metal-containing absorbing solution, wherein a surfactant is added to the electrolytic cell when a heavy metal is deposited on the negative electrode from the absorbing solution containing the heavy metal by applying a potential between the negative electrode and the positive electrode. Of hazardous heavy metals from wastewater. 2. An electrolytic cell partitioned by a porous semipermeable membrane,
The method for removing harmful heavy metals from a harmful heavy metal-containing absorption solution according to claim 1, wherein a surfactant is added to the absorption solution on the negative electrode installation side.