JP2007117984A - Apparatus for treating heavy metals-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment apparatus for removing heavy metals from drainage efficiently and economically. <P>SOLUTION: In the treatment apparatus having a reactor for mixing heavy metals-containing water with a reducing iron compound to generate a precipitation and a tank for carrying out solid-liquid separation of slurry removed from the reactor, the apparatus for treating the heavy metals-containing water comprises means for providing at least one of the above reactor and the solid-liquid separation tank with a variable magnetic field, accelerating precipitation formation while varying a magnetic field in the reactor and accelerating solid-liquid separation while varying a magnetic field in the solid-liquid separation tank. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an economical processing apparatus that efficiently removes heavy metals from wastewater containing heavy metals. More specifically, the present invention relates to an apparatus for treating heavy metal-containing water that is simple in process, excellent in practicality, and efficient in removing heavy metals contained in wastewater and the like efficiently at room temperature.

Many treatment methods for precipitating or agglomerating and removing heavy metals contained in waste water and the like have been known, and magnetic separation means are known as means for efficiently separating heavy metal aggregates or heavy metal precipitates. . Patent Document 1 describes a means for aggregating heavy metal ions in the waste liquid and a separation means using a magnetic filter that captures particles in the waste liquid by forming a strong magnetic field with a superconducting solenoid magnet.

Patent Document 2 describes a processing method in which ferrous ions are added to heavy metal wastewater to form ferrite sludge, which is separated by a thickener or a magnetic separator. Further, in Patent Document 3, when phosphorus or heavy metals are aggregated or precipitated by the aggregation precipitation method or the ferrite method, an aggregate having enhanced magnetism is formed by adding magnetite particles or the like, and this is magnetically separated. A processing method is described.
JP 2000-117142 A Japanese Patent Laid-Open No. 2001-321781 JP 2001-259657 A

Any of the magnetic separations employed in the above-described conventional processing methods statically applies a magnetic field, and there is a limit to the magnetic separation effect. In particular, sedimentation of heavy metals contained in wastewater, etc., varies depending on the type of heavy metals and the state of sedimentation, and there is a problem that sufficient separation effects cannot be obtained simply by statically applying a fixed magnetic field. is there.

The present invention solves the above-mentioned conventional problems in a processing apparatus for precipitating and separating heavy metals contained in waste water and the like, and is a reaction tank for precipitating heavy metals, or solid-liquid separation for separating the precipitates It is an object of the present invention to provide a processing apparatus that can accelerate precipitation of heavy metals or enhance a solid-liquid separation effect by applying a varying magnetic field to either or both of the tanks.

According to the present invention, a processing apparatus having the following configuration is provided.
(1) In a processing apparatus having a reaction vessel in which heavy metal-containing water and a reducing iron compound are mixed to cause precipitation, and a vessel for solid-liquid separation of the slurry extracted from the reaction vessel, the reaction vessel or the solid-liquid separation. It has means for applying a variable magnetic field to at least one of the tanks, and promotes precipitation generation while changing the magnetic field in the reaction tank, or promotes solid-liquid separation if the magnetic field is changed in the solid-liquid separation tank. Equipment for water containing heavy metals.
(2) In the processing apparatus of (1), the apparatus has a sealed reaction tank that causes precipitation by mixing heavy metal-containing water and a reducing iron compound, and the slurry extracted from the reaction tank is subjected to solid-liquid separation. A tank, a tank for adding alkali to a part or all of the separated precipitate (sludge), and a pipe for returning the alkalinized sludge to the sealed reaction tank, in a non-oxidizing atmosphere in the sealed reaction tank , While producing a reductive iron compound precipitate under alkalinity, the slurry or sludge and the air in any step of the circulation path where the slurry is withdrawn from the sealed reaction tank and returned to the sealed reaction tank through alkali addition. In a device that adjusts contact to suppress oxidation of the iron compound and repeats the above steps to treat heavy metal-containing water, a variable magnetic field is applied to at least one of the reaction tank and the solid-liquid separation tank. Processor of heavy metals-containing water having a stage.
(3) The above-described (1) or (2) above, wherein a magnet is disposed around the reaction tank or in the partition wall of the solid-liquid separation tank, and the magnetic field formed by the magnet is changed by rotating or vibrating the magnet. Wastewater treatment equipment described in 1.
(4) The above-described (1) or (2) above, wherein an electromagnet is disposed around the reaction tank or in the partition wall of the solid-liquid separation tank, and the electric field generated by the electromagnet is controlled by controlling the current of the electromagnet. Wastewater treatment equipment described in 1.
(5) In the processing apparatus according to any one of (1) to (4) above, the reducing iron compound is added to the heavy metal-containing water before the reaction vessel in which the heavy metal-containing water and the reducing iron compound are mixed and reacted. An apparatus for treating heavy metal-containing water having a tank to be used.
(6) In the processing apparatus according to any one of (1) to (5) above, a tank for adding an iron compound or an aluminum compound to the heavy metal-containing water before the tank for adding the reducing iron compound to the heavy metal-containing water And a heavy metal-containing water treatment apparatus provided with a tank for solid-liquid separation of the generated precipitate.
(7) In the processing apparatus of any one of (1) to (6) above, a plurality of reaction vessels are provided in series, and a means for applying a variable magnetic field to any reaction vessel and / or solid-liquid separation vessel is provided. Equipment for water containing heavy metals.
(8) In the processing apparatus according to any one of (1) to (7), the upper part of the reaction tank is covered with a cover material, the cover material has a small hole through which a shaft member of a stirrer is inserted, and The treatment apparatus for treating heavy metal-containing water in which the lid has an upward slope toward the small hole and the inside of the reaction tank is maintained in a non-oxidizing atmosphere with limited communication with outside air through the small hole .

The treatment apparatus of the present invention is a reaction for precipitating heavy metals in a treatment apparatus for adding heavy irons to water containing heavy metals to precipitate heavy metals and then separating the precipitates into solid and liquid to remove heavy metals. A means for applying a variable magnetic field to at least one of the tank and the solid-liquid separation tank for separating the precipitate, and promotes precipitation of heavy metals while fluctuating the magnetic field, or promotes separation of precipitation of heavy metals. The removal effect can be enhanced.

Further, in the treatment apparatus of the present invention, an apparatus having a circulation system for returning alkalinized sludge by adding alkali to a part or all of the separated sludge is a non-oxidizing atmosphere in the reaction tank. , Reacting under alkaline conditions to produce a reductive iron compound precipitate, so that iron ferritization can proceed at room temperature, forming compacted and compact starch, good dehydration, and removal of heavy metals The effect is also high.

Furthermore, in the treatment apparatus of the present invention, in the case where an iron compound or an aluminum compound is added in advance to heavy metal-containing water, this pretreatment removes in advance the cause of inhibition of ferritization such as silicate ions, aluminum ions, and trace organic substances. Therefore, the processing effect can be further enhanced.

The processing apparatus of the present invention is a processing apparatus comprising: a reaction tank that mixes heavy metal-containing water and a reducing iron compound to cause precipitation; and a tank that solid-liquid separates a slurry extracted from the reaction tank. Alternatively, it has means for applying a varying magnetic field to at least one of the solid-liquid separation tanks, and promotes precipitation generation while changing the magnetic field in the reaction tank, or promotes solid-liquid separation if the magnetic field is changed in the solid-liquid separation tank. It is the processing apparatus of the heavy metal containing water characterized by the above-mentioned.

The treatment apparatus of the present invention preferably has a sealed reaction tank that causes precipitation by mixing heavy metal-containing water and a reducing iron compound, and a tank for solid-liquid separation of the slurry extracted from the reaction tank, A tank for adding alkali to a part or all of the separated sediment (sludge), a pipe for returning the alkalinized sludge to the sealed reaction tank, and in the sealed reaction tank, alkaline in a non-oxidizing atmosphere The reductive iron compound precipitate is generated under the condition, while the slurry or sludge is brought into contact with the air in any step of the circulation path in which the slurry is extracted from the sealed reaction tank and returned to the sealed reaction tank through alkali addition. In a device that adjusts to suppress oxidation of the iron compound and repeats the above steps to treat heavy metal-containing water, a method of applying a varying magnetic field to at least one of the reaction tank and the solid-liquid separation tank A processing apparatus of heavy metals containing water have.

An example of the processing apparatus according to the present invention is shown in FIGS. FIG. 1 is an example of an apparatus having a circulation system that returns alkali to a reaction tank by adding alkali to a part or all of the separated sludge, and FIG. 2 is an example of an apparatus having a pretreatment step.

1 includes a tank 10 for adding a reducing iron compound to heavy metal-containing water, a closed reaction tank 30 in a non-oxidizing atmosphere that reacts the reducing iron compound with heavy metals to form a precipitate, and the reaction tank. A tank 40 for solid-liquid separation of the slurry extracted from 30, a tank 20 for adding alkali to the separated sludge (precipitate), a pipe for returning alkaline sludge to the reaction tank 30, and a pipe for connecting these tanks A means 50 for providing a varying magnetic field to at least one of the reaction tank 30 and the solid-liquid separation tank 40 is provided.

The means 50 for applying a varying magnetic field is provided, for example, by providing a rotatable support frame (not shown) on the outer periphery of the reaction vessel 30 and providing a magnet (not shown) around the reaction vessel 30 on the support frame. A magnetic field including the inside of the reaction vessel can be formed, and a structure in which the magnetic field is rotationally changed by rotating the support frame can be formed. Alternatively, a structure in which a support frame that vibrates up and down is used instead of a rotatable support frame and the support frame on which the magnet is mounted is moved up and down to vibrate the magnetic field up and down may be used. Moreover, the structure which changes a magnetic field electrically by switching the electricity supply to an electromagnet using a some electromagnet may be sufficient. Ferritization proceeds in the reaction tank, and a magnetic precipitate is formed. Therefore, the ferrite formation is further promoted by applying a variable magnetic field.

In addition to the above structure, the magnetic field changing means 50 of the solid-liquid separation tank 40 is provided with, for example, a support frame (not shown) surrounding the central portion in the tank, and an electromagnet or the like provided on the support frame. The magnetic field may be changed by intermittently forming the magnetic field by switching the energization to the electromagnet. By forming a magnetic field, the precipitation of the magnetic precipitate proceeds, and by turning off the magnetic field, the sedimentation of the aggregate is promoted.

Examples of magnetic field fluctuations using electromagnets are shown in FIGS. As shown in FIG. 3, a plurality of electromagnets 81 are mounted on the outer periphery of the thickener 82. The plurality of electromagnets 81 may be provided at the bottom of the thickener 82 as shown in FIG. These electromagnets 81 are connected to the control unit 80, and the current of each electromagnet 81 is controlled by the control unit 80.

By introducing the slurry, convection as shown in the figure is generated inside the thickener 82, and fine starch particles float along the tank wall, become suspended, overflow, and flow out of the system. In order to prevent such outflow of starch particles, the electromagnet is energized to form a magnetic field in the range including the thickener, thereby suppressing the starch particles from floating. Since the starch particles are ferritic, they are attracted to the wall surface of the thickener by the formation of a magnetic field and adhere to the wall surface. When the energization of the electromagnet is stopped after a predetermined time and the magnetic field is eliminated, the starch particles adhering to the thickener wall surface settle to the bottom of the thickener due to the disappearance of the magnetic force and are discharged out of the system through the discharge port. The same applies to the structure shown in FIG. 4. The starch particles gather at the bottom of the thickener by the formation of the magnetic field, and are discharged out of the system from the discharge port by eliminating the magnetic field.

5 and 6 show examples in which an electromagnet 81 is attached to a reaction vessel (reaction vessel) 90. FIG. As shown in the drawing, a plurality of electromagnets 81 are attached to the tank wall of the reaction vessel 90 at equal intervals, and each electromagnet is connected to a control unit (not shown). The current of each electromagnet 81 is controlled by the control unit. Specifically, for example, the magnetic field formed by the electromagnet 81 is rotated by switching the current alternately on and off in order clockwise or counterclockwise. Preferably, the magnetic field is rotated in the direction opposite to the rotation direction (liquid flow direction in the drawing) of a stirrer (not shown) provided in the center of the reaction tank 90. As a result, the moving direction of the solid particles (starch particles) by the magnetic field and the liquid flow direction are opposite to each other, so that the relative linear velocity between the liquid and the starch particles is increased, and the reaction efficiency of starch ferrite formation is improved. .

The said processing apparatus has the outstanding heavy metal removal effect about heavy metal containing water. In the present invention, heavy metal containing water broadly means water containing heavy metals, and includes various wastewater and wastewater generated naturally and artificially, for example, industrial wastewater and sewage, seawater, river water, This refers to water from marshes and lakes, surface pools, rivers and other dams, underground running water and pools, underdrains, etc. that contain heavy metals. In the following description, these waters may be referred to as waste water, and the heavy metal containing water may be referred to as waste water containing heavy metals.

In the present invention, heavy metals refer to heavy metal elements such as selenium, cadmium, hexavalent chromium, lead, zinc, copper, nickel, arsenic, and antimony, and metal elements. The treatment system of the present invention has an excellent removal effect with respect to any one or more of the heavy metals that are the sources of contamination contained in the waste water and the like.

The heavy metal-containing water is introduced into the addition tank 10 and the reducing iron compound is added. As the reducing iron compound, a ferrous compound such as ferrous sulfate (FeSO ₄ ) or ferrous chloride (FeCl ₂ ) can be used. The addition amount of the ferrous compound is appropriate such that the Fe ²⁺ ion concentration is 400 to 600 mg / L. Waste water to which the reducing iron compound is added is introduced into the reaction tank 30.

The reaction tank 30 is mixed with the alkaline metal sludge returned from the solid-liquid separation step together with the heavy metal-containing water to which the reducing iron compound is added. This alkaline sludge is adjusted to pH 11 to 13 by adding alkali to a part or all of the precipitate (sludge) separated into solid and liquid in the subsequent step. As the alkaline substance to be added, slaked lime, quick lime, sodium hydroxide or the like can be used. By mixing the alkaline sludge, the pH of the reaction tank 30 is adjusted to 8.5 to 11, preferably pH 9.0 to 10.

In the reaction tank 30, heavy metal-containing water to which a reducing iron compound is added and alkaline return sludge are mixed and reacted in a non-oxidizing atmosphere to generate a reducing iron compound precipitate. This iron compound precipitate is a mixture of green last and iron ferrite and is a reductive precipitate.

Green last is a blue-green substance in which a hydroxide of ferrous iron and ferric iron forms a layer, and has a structure in which an anion of heavy metals is incorporated between layers, and is represented by, for example, the following formula (1).
_{^{[Fe II (6-x) Fe}} III x (OH) 12 ] ^{x +} [A _x / n · yH ₂ O] ^x- ... (1)
(0.9 <x <4.2, Fe ²⁺ / total Fe = 0.3 to 0.85).

Moreover, iron ferrites are Fe ^II iron (III) salt, but mainly of magnetite _{^{(Fe II Fe III 2 O 4}} ), or those containing ferrate heavy metals in a part. In the reducing iron compound precipitate of the present invention, for example, heavy metal ions are taken in between the layers of the green last, and iron ferrite is formed in a state in which heavy metals are partially included. Specifically, for example, hexavalent selenium (SeO ₄ ²⁻ ) is reduced by a ferrous compound to tetravalent selenium (SeO ₃ ²⁻ ) and elemental selenium, which are taken in between the layers of green last. It precipitates in the state.

The reaction tank 30 is a sealed reaction tank in which the inflow of air is blocked in order to generate the reducible iron compound precipitate. In the reaction tank 30, the reaction is carried out in a non-oxidizing atmosphere under alkaline conditions of pH 8.5-11, preferably pH 9.0-10. The liquid temperature may be about 10 ° C. to 30 ° C. and does not need to be heated. The reaction time may be about 30 minutes to 3 hours. In addition, if the reaction vessel is not sealed and is not in a non-oxidizing atmosphere, or if the alkali is weak, precipitates having the above reducing power will not be generated, and the same effect as this treatment apparatus can be obtained. I can't.

In any step of the circulation path in which the slurry is extracted from the sealed reaction tank and returned to the sealed reaction tank again after alkali addition, the contact of the slurry or sludge with air is adjusted to suppress oxidation of the iron compound. preferable. Specifically, for example, a solid-liquid separation tank having an open top or an alkali addition tank having an upper opening is used, and in the solid-liquid separation, the precipitate slurry and air are brought into contact with each other, or alkali is added to the separated sludge. What is necessary is just to adjust the contact time, the contact area, etc. while making sludge and air contact when adding.

In the treatment apparatus of the present invention, the ratio of the divalent iron ions to the total iron ions [Fe ²⁺ / Fe (T )] Is preferably 0.4 to 0.8, and the iron ion ratio is more preferably controlled to 0.55 to 0.65. When this ratio is out of the above range, the reduction of heavy metals becomes insufficient, or the sedimentation property of starch deteriorates, which is not preferable. By producing the reducible iron compound precipitate, heavy metals contained in the waste water and the like are reduced and easily taken into the precipitate.

By repeating the return of alkaline sludge to the reaction tank 30 and repeating the reaction with wastewater to which a reducing iron compound is added, the green rust is gradually oxidized to iron ferrite by the precipitation that was initially deep blue-green. Changes to black. Since the reducibility is lost when most of the green rust becomes iron ferrite, the reducibility can be reduced by controlling the ratio of divalent iron ions to total iron ions [Fe2 + / Fe (T)] within the above range. To produce a precipitate.

In the treatment apparatus of the present invention, the reducing sludge (iron compound precipitation) is separated, and part or all of the reduced sludge is alkalinized and returned to the reaction vessel, reacted in a non-oxidizing atmosphere, and the reducing sludge is precipitated again. By repeating this process, iron ferrite is formed while maintaining the reducibility of the sludge (precipitation), so that the consolidation of the precipitation proceeds and the concentration of the starch is remarkably increased, thereby improving the effect of removing heavy metals. Incidentally, precipitation (sludge) mainly composed of iron hydroxide is bulky and has a heavy dehydration burden. Further, in the processing apparatus of the present invention, the iron ferrite forming the precipitate is magnetized because it is mainly composed of magnetite. By applying a variable magnetic field to the reaction vessel, ferritization is promoted, and solid-liquid separation is performed. By applying a fluctuating magnetic field to the tank, aggregation of the precipitate can be promoted and the separation effect can be enhanced.

The slurry discharged from the reaction tank 30 is guided to a solid-liquid separation means such as a thickener, for example, and sludge is settled on the tank bottom to be separated. The starch can be solid-liquid separated to remove heavy metals. Moreover, as already stated, an alkali is added to part or all of sludge, it adjusts to pH 11-13, and it returns to the reaction tank 30, The precipitation production | generation reaction is repeated in the reaction tank 30. If the ratio of sludge to be returned (circulation ratio of returned sludge) is determined so that the ratio [Fe2 + / Fe (T)] of the divalent iron ions and total iron ions in the precipitate generated in the reaction tank 30 is within the above range. Good. The treatment method of the present invention can be carried out in either a batch type or a continuous type.

The processing apparatus shown in FIG. 2 includes a tank 60 for adding an iron compound or an aluminum compound to heavy metal-containing water to form a precipitate before the reducing iron compound adding tank 10 and a solid-liquid separation for removing the precipitate. A pretreatment process provided by the tank 70 is formed. In the pretreatment step, an iron compound is added to heavy metal-containing water, an alkali is added, and an iron hydroxide is generated under alkalinity, whereby at least one of silicate ions, aluminum ions, and trace organic substances is added to the iron water. It precipitates with the oxide precipitate, which is removed by solid-liquid separation. A ferric compound such as ferric chloride is preferred as the iron compound. An aluminum compound may be used in place of the iron compound. An aluminum compound is added, an alkali is added, and an aluminum hydroxide is precipitated under alkalinity. Since silicate ions and trace organic substances are taken into the precipitate and precipitated, it can be solid-liquid separated and removed from the waste water.

Silicate ions, aluminum ions, and trace amounts of organic substances in the wastewater cause the ferritization in the reaction tank, so by removing them in advance in the pretreatment process, the ferritization is facilitated and heavy metals are removed. The processing effect can be enhanced.

Moreover, the said reaction tank 30 is good to provide a some tank in series, and to advance the ferrite formation reaction by transferring the produced | generated slurry in steps. The variable magnetic field means 50 may be provided in any reaction tank. Further, the upper part of the reaction tank is preferably covered with a cover material, and the cover material is provided with a small hole through which the shaft member of the stirrer is inserted and has a shape having an upward slope toward the small hole.

By making the reaction vessel in the above shape, the inside of the reaction vessel is kept in a non-oxidizing atmosphere with limited communication with outside air through the small holes, and the gas generated in the reaction vessel is reduced along the inclination of the lid. It is guided to the hole and can be pulled out through a slight gap around the shaft member.

1 and FIG. 2 relates to a treatment process for producing a reduced iron compound precipitate using a closed reaction vessel, but the present invention can also be applied to the case of using an open reaction vessel with an open top. it can.

Schematic diagram showing the processing apparatus of the present invention The schematic diagram which shows the processing apparatus containing the pre-processing process of this invention In the processing system of this invention, the conceptual diagram of the structural example which attached the electromagnet to the thickener In the processing system of this invention, the conceptual diagram of the structural example which attached the electromagnet to the thickener In the processing system of this invention, the conceptual diagram of the example of a structure which attached the electromagnet to the reaction tank Conceptual perspective view of the configuration example of FIG.

Explanation of symbols

10-reducing iron compound addition tank, 20-alkali addition tank, 30-reaction tank, 40-solid-liquid separation tank, 50-variable magnetic field means, 60-precipitation tank, 70-solid-liquid separation tank, 80-control unit , 81—electromagnet, 82—thickener, 90—reaction vessel (reaction vessel).

Claims (8)

In a processing tank having a reaction tank that mixes heavy metal-containing water and a reducible iron compound to cause precipitation, and a tank that solid-liquid separates the slurry extracted from the reaction tank, at least one of the reaction tank or the solid-liquid separation tank Heavy metals having means for applying a variable magnetic field to any of them, promoting precipitation generation while changing the magnetic field in the reaction tank, or promoting solid-liquid separation if the magnetic field is changed in the solid-liquid separation tank Water treatment equipment.
The treatment apparatus according to claim 1, further comprising: a sealed reaction tank for mixing the heavy metal-containing water and the reducing iron compound to cause precipitation, and a tank for solid-liquid separation of the slurry extracted from the reaction tank. A tank for adding alkali to part or all of the precipitate (sludge), a pipe for returning the alkaliized sludge to the closed reaction tank, and in the closed reaction tank under a non-oxidizing atmosphere and under alkaline conditions While the reductive iron compound precipitate is generated, the contact between the slurry or sludge and air is adjusted in any step of the circulation path in which the slurry is extracted from the sealed reaction tank and returned to the sealed reaction tank through alkali addition. In the apparatus for suppressing oxidation of the iron compound and treating the heavy metal-containing water by repeating the above steps, means for applying a varying magnetic field to at least one of the reaction tank and the solid-liquid separation tank Heavy metals containing water processing apparatus.
The wastewater treatment apparatus according to claim 1 or 2, wherein a magnet is disposed around the reaction tank or in a partition wall of the solid-liquid separation tank, and the magnetic field formed by the magnet is changed by rotating or vibrating the magnet. .
The wastewater treatment apparatus according to claim 1 or 2, wherein an electromagnet is disposed around the reaction tank or in a partition wall of the solid-liquid separation tank, and the electric field of the electromagnet is controlled to vary the magnetic field formed by the electromagnet. .
In the processing apparatus in any one of Claims 1-4, the heavy metals which have a tank which adds a reducing iron compound to heavy metal containing water before the reaction tank which carries out the mixing reaction of heavy metal containing water and a reducing iron compound Water treatment equipment.
In the processing apparatus of any one of Claims 1-5, the tank which adds an iron compound or an aluminum compound to heavy metal containing water before the tank which adds a reducing iron compound to heavy metal containing water, and produced | generated precipitation An apparatus for treating heavy metal-containing water provided with a tank for solid-liquid separation.
The processing apparatus according to any one of claims 1 to 6, wherein a plurality of reaction tanks are provided in series, and a means for applying a variable magnetic field to any reaction tank and / or solid-liquid separation tank is provided. Processing equipment.
The processing apparatus according to any one of claims 1 to 7, wherein an upper portion of the reaction tank is covered with a lid member, the lid member has a small hole through which a shaft member of a stirrer is inserted, and the lid is the small hole. The apparatus for treating heavy metal-containing water, which has an upward slope toward the inside and the inside of the reaction tank is kept in a non-oxidizing atmosphere with limited communication with outside air through the small holes.

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