JPH03213193A - Electrochemical water treatment - Google Patents

Abstract

PURPOSE:To remove silicon by precipitation without adding chemicals by a method wherein the untreated water contg. at least silicon component is supplied into a treating bath provided with an aluminum-made electrode as at least either anode or cathode and the water is treated electrochemically. CONSTITUTION:An electrochemical treating bath 1 is provided with a plate-like aluminum-made anode 2 and an aluminum-made cathode 3, and supplied and filled with the untreated water contg. the impurities such as manganese ions and iron ions dissolved therein. When both the electrodes 2 and 3 are electrified, an oxidative reaction takes place on the surface of the anode 2, the aluminum is liberated at the aluminum-made anode 2 and dissolved in the water 4 being treated as aluminum ions, suspended in the water 4 in the state of a flock, adsorbs impurity ions such as silicon component and such an absorbate is precipitated or kept in suspension due to the increased density thereof. In this way, a treatment at a higher flocculating rate becomes possible to permit the silicon component to be precipitated with a higher efficiency than by the method of adding chemicals.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electrochemical treatment method for water containing various impurities, and more specifically, to a method for electrochemically treating water containing various impurities, and more specifically for removing turbidity from water to be treated and removing silicon, manganese, and iron. It removes impurity ions such as CO
The present invention relates to an electrochemical treatment method for water that does not require the addition of chemicals and can also contribute to the reduction of D.

(Prior art and its problems) Advanced water treatment technology in various industries is at its ultimate stage, including widespread use and problems related to pollution, and is becoming increasingly important for water treatment under various conditions. It is coming. Electrochemical treatment technology has attracted attention as a field of water treatment, and various results have been reported.

For example, chemicals have been conventionally used to prevent scales made of various minerals such as calcium, magnesium, and silica from adhering to the inner walls of hot water supply piping, drinking water piping, and boiler cooling water circulation piping. However, the chemicals used vary depending on the ion species to be removed, and the treatment conditions also vary. are being processed. For example, in order to remove the turbidity of water to be treated, the turbidity is floc-formed and precipitated by adding chemicals and removed by filtration, and iron ions in the water to be treated are oxidized by aeration and precipitated as oxides, and further manganese ions are formed. COD is removed by reacting manganese sand with sodium hypochlorite and chlorine to precipitate it as a secondary oxide.
is being reduced by the well-known activated sludge method and oxidation method using potassium permanganate.

However, treatment techniques based on this chemical have almost reached their limits due to the toxicity of the chemical itself, adverse effects due to increased salt concentration, and increased processing costs due to the cost of the chemical. Furthermore, the nature of impurities contained in the water to be treated is changing, and recently the content of silica in the water to be treated has increased, and with the recent development of biotechnology, the composition of the water used in this technology has changed. It is reported that the situation is also changing.

Therefore, the processing methods and processing equipment that have been used in the past are
00% operation, and effective iron, manganese, or silica removal cannot be performed, and an effective alternative technology is required.

The present inventors have proposed a method and apparatus for effectively filtering the precipitate generated in the water to be treated (Japanese Patent Application No. 1-21683).
No. 3), this invention is a technology that effectively filters impurities that have already precipitated, and can achieve satisfactory filtration efficiency, but if the impurity ions dissolved in the water to be treated cannot be precipitated, the water to be treated will It is not possible to remove impurities from

(Objective of the Invention) The present invention provides a method for electrochemically treating water containing at least silicon to precipitate and remove silicon from the water to be treated without adding chemicals. With the goal.

(Means for Solving the Problems) The present invention firstly supplies water to be treated containing at least a silicon component to a treatment tank in which an aluminum electrode is installed as at least one of an anode and a cathode. This is an electrochemical treatment method for treated water, in which the second step is to supply treated water containing at least a silicon component to a treatment tank equipped with an aluminum electrode as at least one of an anode and a cathode. After treating the water to be treated, and passing the precipitate dispersed in the water through a solid matter sedimentation accelerator in which a plurality of electrodes are installed approximately parallel to each other at intervals, the water to be treated is is supplied to a filtration tank equipped with a filtration membrane and an electric field is applied to at least a part of the filtration tank, and the precipitated silicon component is filtered and removed by the filtration membrane. This is a processing method.

The present invention will be explained in detail below.

In the present invention, water to be treated which contains at least a silicon component such as silica, and which usually contains manganese ions, iron ions, etc., and which may further become cloudy and may contain humic acid-like substances, is applied to at least one electrode. This is an electrochemical treatment method that uses electrodes made of aluminum. In addition, in the present invention, precipitation is performed while applying an electric field, or a solid matter sedimentation accelerating device in which a plurality of electrodes are installed approximately parallel to each other at intervals [for example, Hydrotreater (trade name: Hydrotreater (trade name) manufactured by Hydrodorito Inc. for Texas, USA) )] can be used in combination to further improve processing efficiency.

When the water to be treated is treated by the method of the present invention, it is possible to perform treatment with a higher flocculation rate than the method of adding chemicals, although it depends on the conditions of the electrochemical treatment. The silicon component etc. can be precipitated with high efficiency, and the reason for this can be inferred as follows.

When electricity is applied using an aluminum electrode as an anode, aluminum, which has a high ionization tendency, is oxidized according to the following formula and is dissolved in the electrolyte as aluminum ions.

Aj! -+ An" + 3eThe aluminum ions thus generated become flocs and float in the water to be treated in the treatment tank, and the silicon contained in the water to be treated and, if present, other manganese ions and iron. Ions, etc. are strongly adsorbed to the floc-like aluminum ions and precipitate alone or co-precipitate.In this case, the type of impurity ions basically does not depend on the type of impurity ions or the liquid properties of the water to be treated. Each impurity metal ion is adsorbed by flocculated aluminum ions without being removed, and each impurity metal ion ultimately reacts with hydroxide ions generated by electrolysis, precipitates as hydroxide, and is removed. There is no need to change the type of additive agent depending on the type of ion to be treated or to perform the treatment multiple times, which greatly simplifies the treatment operation.The aluminum ions generated by the electrolysis are ultimately converted into water. It reacts with acid ions and is converted to aluminum hydroxide, resulting in the hydrolysis of aluminum.

Both electrodes used in this electrochemical treatment are preferably made of aluminum. As the aluminum anode dissolves in the water to be treated and its volume decreases as the treatment progresses, if both electrodes are made of aluminum and the anode and cathode are reversed during the treatment operation while energized, the volume reduction of both electrodes will be kept almost constant. I can do it. The reversal time is not particularly limited, but is preferably set at intervals of 1 to 5 minutes, and if necessary, an alternating current may be applied to reverse the reversal several thousand times per second. Furthermore, when electricity is applied to an aluminum anode, an oxide film is formed on the surface of the anode due to an oxidation reaction, making it difficult for further dissolution reactions to proceed. Therefore, if the electrodes are reversed at regular intervals, the oxide film on the electrode that functions as a cathode will be removed. Because it is dissolved and removed by the reduction reaction at the cathode, the treatment operation can be performed with high activity without substantially forming an oxide film.
1! You can continue.

The shape of the aluminum electrode used is not particularly limited, and can be, for example, plate-shaped, rod-shaped, or porous plate-shaped, and because it melts according to the treatment, it can be made relatively large in volume and used for a long time. desirable. Furthermore, the treatment tank used is not particularly limited, and conventional electrochemical treatment tanks such as box-shaped or cylindrical-shaped can be used.

Other processing conditions, such as voltage values and current values, are not particularly limited and may be set in the same manner as in the prior art.

By such electrochemical treatment, silicon components etc. are maintained in a precipitated or suspended state, and when the above-mentioned suspended solid sedimentation accelerator is used, the sedimentation rate is high and a dense precipitate is obtained, which is then processed by filtration etc. separated from the water to be treated by a separation operation,
Impurity ions can be removed from the water to be treated.

However, since the silicon components suspended or precipitated by the above operation contain hydration water and viscous substances, they are difficult to filter using normal filtration methods, and the filter cloth is clogged and clogged. Efficiency is often very poor. Therefore, in the present invention, it is possible to further process the silicon components etc. generated by the energization treatment so that they can be easily filtered.

In other words, the water to be treated in which silicon components and the like have been precipitated or suspended using an aluminum electrode is allowed to stand as necessary to further sufficiently precipitate the silicon components, and then the water to be treated is The precipitated silicon component can be removed by supplying the solution to a filtration tank equipped with a filtration membrane and having an electric field applied to at least a portion of the filtration tank.

When an electric field is applied to a solid-liquid dispersion system or a liquid-liquid dispersion system such as an emulsion in which suspended particles such as the silicon component are suspended, the suspended particles move toward the cathode or anode depending on the charge they have. However, a potential difference occurs between each particle, disrupting the equilibrium. This causes each particle to release hydration water and viscous substances,
This promotes sedimentation separation and increases the separation speed by electrophoresis, leading to a state in which particles are easily separated. In other words, if the particle size of the suspended particles is small, the electrophoretic velocity will be greater than the gravitational sedimentation rate, and they will be separated from other particles, and if the particle size is large, the gravitational sedimentation rate will be greater, making it easier to form a precipitate. .

Therefore, when the treated water containing suspended matter treated with the aluminum electrode is filtered through a filtration membrane without applying an electric field, the suspended matter in the treated water becomes positively and negatively charged due to the electric field. Depending on the particle size, the particles move toward the cathode or anode, releasing the contained hydrates and viscous substances, lowering the viscosity, changing from a suspended state to a floating state, and depending on the particle size, they precipitate or move toward the electrodes by electrophoresis. Moving. The suspended particles have their viscous substances removed in this way and become a smooth powder or granule, which can be easily isolated and recovered as a solid on the filtration membrane by passing it through the filtration membrane. In particular, in electroosmotic filtration, osmotic pressure plays the role of mechanical pressurization, so pressure loss can be further reduced.

Furthermore, the water to be treated of the present invention often contains inorganic substances that easily generate scale, and in that case, a plurality of electrodes are installed approximately parallel to each other at intervals before or after the treatment tank having the aluminum electrodes. A solid matter sedimentation accelerating device may be provided, and the water to be treated may be supplied to the device to perform treatment and suppress the formation of scale (Japanese Patent Publication No. 57-3).
(See No. 2640).

By this operation, the inorganic substances that tend to generate scale in the pipes and the like are precipitated and filtered, thereby suppressing the generation of scale in the pipes. Note that this solid matter sedimentation accelerator may be installed either before or after the aluminum electrode electrolytic cell of the present invention.

The method of the present invention includes filtration of industrial process water that handles inorganic substances such as the photographic industry, plating industry, cement industry, and iron smelting industry.
Filtration of various liquids in industries that mainly handle organic substances such as food industry, food processing industry, pharmaceutical industry, cosmetics industry, cleaning industry, painting industry, printing industry, etc., cleaning in electronic industry, precision machinery industry, solid matter removal in cooling water, Filtration of solids in process water and circulating water in fish farming-related industries, filtration of swimming pools, inns, bathhouses, hot springs, etc., removal of pollutants in various types of water in buildings and condominiums, separation and removal of solids in wastewater treatment processes. It can be applied to a very wide range of fields such as

Next, an example of the method of the present invention will be explained based on the accompanying drawings, but the present invention is not limited thereto.

The drawing is a flow sheet illustrating one embodiment of the invention.

A box-shaped electrochemical treatment tank 1 is equipped with a plate-shaped aluminum anode 2 and an aluminum cathode 3.
As shown by the arrows, water to be treated in which impurities such as silicon components, manganese ions, and iron ions are dissolved is supplied to fill the treatment tank 1 . When electricity is applied between the two electrodes 2.3, an oxidation reaction occurs on the surface of the anode 2, and the aluminum constituting the anode 2 is dissolved in the water to be treated 4 as aluminum ions. The aluminum ions float in the water to be treated 4 in the form of flocs, adsorb impurity ions such as silicon components, manganese and iron, oxides thereof, or ions dissolved in the water 4 to be treated, and become densified. The substance may be precipitated or maintained in suspension.

As energization continues, the amount of anode 2 dissolved increases and its volume decreases, but if the direction of energization is reversed at certain intervals, for example every 5 minutes, the aluminum electrode that was functioning as a cathode will function as an anode and will similarly dissolve. Therefore, without affecting the removal of impurities from the water to be treated, the volume reductions of the anode and cathode electrodes can be made almost equal, and fluctuations in conditions such as changes in current density can be minimized. Further, an oxide is formed on the surface of the anode 2 due to anodic oxidation and becomes passivated, but by reversing the current direction, the oxide can be reduced and dissolved, and the active treatment of the water to be treated can be continued.

The water to be treated containing suspended or precipitated impurity particles that has been treated in the treatment tank 1 is taken out from the treatment tank 1, and in the diagram of the plurality of adjacent pairs, the two pairs of sedimentation anodes 5 and cathodes 6 are approximately A cylindrical slope whose adjacent lower end protrudes downward in a conical manner is supplied to a solid matter settling accelerator device 7 installed in parallel with each other, and after settling the suspended solid matter by passing through the device. Static sedimentation tank with plate 8 (or thickener)
will be introduced in The sedimentation tank 8 is for allowing the water to be treated 4'' to stand still so that suspended particles in the water to be treated 4'' can further settle.

The water to be treated containing impurity particles that has settled in the sedimentation tank 8 is then introduced into the adjacent filtration tank 9 as shown by the arrow. The filter tank 9 has a cylindrical main body 10 whose lower end protrudes downward in a conical shape, and a bag-shaped bag made of a synthetic resin such as polypropylene, which is arranged along the inner wall of the main body 10 and has almost the same shape as the main body 10. An anode 12 and a cathode 13 for forming an electric field are disposed on both sides of the main body 10. When the to-be-treated water was supplied to the filtration tank 9 while energizing the two poles 12 and 13 to form an electric field, the equilibrium between suspended particles in the to-be-treated water was disrupted as described above, and the viscosity of each particle decreased. Change into particles. When filtration pressure is applied in this state, for example, if the particles are sucked from the lower part of the filtration tank 9, the particles will be sucked in, but they will not be able to pass through the mesh of the filtration membrane 11, and will not block the mesh because of their low viscosity. It is accumulated in the filter membrane 11. Therefore, after the filtration operation is completed, the filtered impurity particles are collected in the filtration membrane 11, and a clarified filtrate can be obtained.

(Example) Examples of electrochemical treatment of water to be treated according to the present invention will be described below, but the examples are not intended to limit the present invention.

Suzuma U Juice Water to be treated was treated using the treatment tank, sedimentation tank, and filtration tank shown in the flow sheet shown above. The processing tank is made of synthetic resin and has a box shape with a length of 60 cm, a width of 30 cm, and a depth of 50 cm. Inside the processing tank, an anode and a cathode each having a length of 22 cm are placed.
, 11 tanks were constructed in which flat aluminum electrodes each having a width of 50 cm and a thickness of 0.5 cm were installed.

In this treatment tank, 100mg/12 of silica and 100mg/12 of iron were added.
mg/j! and manganese 0.8mg/j! Contains
COD is 3,5mg/I! Well water having the following properties was supplied as water to be treated at a rate of 801/min, and the water to be treated was treated while applying a voltage of 65 V between the two electrodes.

Next, the treated water was introduced into a sedimentation tank having an inner diameter of 100 cm, a depth of 200 cm, and a lower end inclined toward the center at a rate of 80 β/min, and left to stand for about 20 minutes.

Next, the water to be treated was introduced into a filtration tank having an inner diameter of 22 cm and a depth of 100 cm, the lower end of which was inclined toward the center, and a bag-shaped filtration membrane made of polypropylene having approximately the same shape as the main body was attached along the inner wall of the tank. A plate-shaped anode made of titanium and a cathode made of nickel are installed on both sides of the filter tank.
The treated water was filtered through the filtration membrane while applying an electric field of V/Cm, and the impurity concentration in the filtered water was measured. Silica 12a + g/ff,
Iron 0.05mg/l and manganese 0.01mg/12
The COD was reduced to 5 mg/l.

The water to be treated was filtered in the same manner as in the example except that no treatment tank was installed.

The impurity contents in the water to be treated after treatment were 95 mg/l of silica, 1 kg/l of iron, and 0.81 g/l of manganese, and the COD was reduced to 27 g/l.

After adding PAC at a rate of 250 mg/l for silica removal and sedimentation, iron and manganese removal to the treated water of the Beibai Coal Plant Example and treating it according to the conventional method, the concentration of impurity components in the treated water was When measured, each contained 98 m of silica.
g/11, iron 0.75 mg/l and manganese 0.
8 mg/It, and the COD had decreased to 30 mg/f.

Comparing Comparative Example 1 and Comparative Example 2 with Examples, it is found that in the method of Example, the amount of impurities present in the water to be treated after treatment is small, and there is no need to use chemicals as in Comparative Example 2, so there is no toxicity. It can be seen that there is no need to consider this method, and it is advantageous in terms of cost.

(Effects of the Invention) The present invention supplies water to be treated containing a small amount of silicon components to a treatment tank equipped with an aluminum electrode as at least one of an anode and a cathode, thereby increasing the adsorption power of dissolved aluminum ions. This is a method for electrochemically treating water to be treated using the method of treating the water to be treated (claim 1).

When water to be treated containing silicon components etc. is treated by the method of the present invention, aluminum serving as an electrode is dissolved in the water to be treated as aluminum ions during electrolysis. The aluminum floats or suspends in the water to be treated as flocs and strongly adsorbs impurities such as silicon components in the water to be treated, resulting in an increase in the diameter of the flocs and the tendency to settle. Therefore, subsequent filtration operations etc. can be easily performed. Furthermore, since no chemicals are used, there is no need to consider pollution or carcinogenicity, and the water to be treated can be treated at low cost. Furthermore, since the separation is by adsorption, impurities other than silicon components can be removed from the water to be treated regardless of their type, so it is a very effective method for treating water to be treated.

Further, both the anode and the cathode are made of aluminum, and the water to be treated is treated while reversing the polarity.
), since almost equal amounts of both electrodes are dissolved in the water to be treated, there is no large difference in current density between the two electrodes, and furthermore, the oxide film formed on the anode surface by anodization can be removed by cathodic reduction reaction. Therefore, it is possible to avoid all the inconveniences caused by using an aluminum electrode, and the activated electrode surface can be continuously brought into contact with the liquid.

Further, after the treatment according to claim 1 and the treatment using a solid matter sedimentation accelerator before or after the treatment, the water to be treated is supplied to a filtration tank equipped with a filtration membrane and at least a part of which is applied with an electric field. It is also possible to filter and remove the precipitated silicon component using the filter membrane (Claim 3).

By installing a solid matter sedimentation accelerator in which a plurality of electrodes are installed approximately parallel to each other at intervals before and after the treatment tank, it is possible to sediment inorganic substances that tend to generate scale and obtain a dense sediment. By applying electric field treatment to the sediment generated in this way, the flocs release hydrates and viscous substances to lower the viscosity, further improving the filtration efficiency of the water to be treated and increasing the treatment capacity of the treatment method of the present invention. It can be greatly improved.

[Brief explanation of drawings]

The drawing is a flow sheet showing one aspect of treatment of water containing impurities according to the present invention. Electrochemical treatment tank cathode 4.4゛... Anode for sedimentation 6... Solid matter sedimentation promotion device filtration tank 10... Main body filtration membrane 12... Anode for electric field formation Cathode for electric field formation 2... Anode Treated water/sedimentation cathode 8...sedimentation tank

Claims (3)

[Claims] (1) Electrochemical treatment of water to be treated, in which water to be treated containing at least a silicon component is supplied to a treatment tank equipped with an aluminum electrode as at least one of an anode and a cathode, and the water to be treated is treated. Method. (2) Both the anode and cathode are aluminum electrodes,
2. The electrochemical treatment method according to claim 1, wherein the treatment is carried out while reversing the polarities of both poles. (3) Treating the water to be treated by supplying the water to be treated containing at least a silicon component to a treatment tank equipped with an aluminum electrode as at least one of an anode and a cathode, and dispersing it in the water to be treated. After the precipitate is passed through a suspended solids sedimentation accelerator in which a plurality of electrodes are installed approximately parallel to each other at intervals, the water to be treated is fitted with a filtration membrane and an electric field is applied to at least a portion of the water. A method for electrochemically treating water to be treated, the method comprising: supplying the water to a filtration tank, and filtering and removing the precipitated silicon component through the filtration membrane.