KR100950954B1 - Fe0 packed bipolar electrolytic cell for removing nitrate ion from water - Google Patents

Abstract

PURPOSE: A zero-valent iron bipolar electrolytic cell for water purification is provided to effectively eliminate nitrate ion and Escherichia coli from water without inputting an additional drug using conductivity of the zero-valent iron. CONSTITUTION: A zero-valent iron bipolar electrolytic cell for water purification comprises a positive electrode(103), a negative electrode(104), and a filler(105) which is included between the positive electrode and the negative electrode. The filler is manufactured by mixing conductive particles and insulating particles. The conductive particle is the zero-valnet iron. The insulating particle is silica. The conductive particle and the insulating particle is mixed with a ratio of 1:1.5-1.5:1. The positive electrode is niobium(Nb) electrode and the negative electrode is stainless steel electrode. The difference of the voltage applied in the positive electrode and negative electrode is 50-80V. The electrolytic cell includes a water injection hole(107) and a water outlet(108).

Description

Fe0 packed bipolar electrolytic cell for removing nitrate ion from water to remove nitrate nitrogen from water

The present invention relates to an electrolytic cell for water purification to remove nitrate nitrogen in water. More specifically, the electrolytic cell for water purification that has high removal efficiency of nitrate nitrogen and no additional additives is injected, so that the interlocking control is simple and unmanned operation is possible. Relates to a device.

Water is indispensable for a person to survive. Water must not contain more than a certain level of contaminants in order to be used as drinking water for the descent in the form of snow or rain on the ground through circulation. In Korea, rainfall is concentrated due to the region or season, and the shortage of water is intensifying. Therefore, there is a growing need for research on the technology of purifying water containing pollutants and using them as drinking water.

One of the drinking water quality criteria for water to be used as drinking water is the concentration of nitrate nitrogen in water. Conventionally used methods for removing nitrate nitrogen in water include physicochemical treatment and biological treatment.

Physicochemical methods include ion exchange, electrodialysis, reverse osmosis and catalysts. Among them, reverse osmosis and electrodialysis have problems related to Total Dissolved Solid (TDS) and additional contaminants. The problem is that the removal is expensive compared to other methods. Although the ion exchange method is easy to operate, the initial installation cost and maintenance costs are expensive, and since a high concentration of nitrate brine is generated, a brine reprocessing process is required. The catalyst-based method is widely used as a catalyst using a strong reducing agent, Zero Valent Iron (ZVI) as a catalyst, but requires a low pH treatment condition and additionally processes the iron by-products generated. Has

The treatment method using the dependency microorganism, which is a biological treatment method, has a problem that the reaction is slow and incomplete, requires the administration of an external carbon source (methanol, ethanol or acetic acid, etc.) and excessive operating costs due to the generation of excess sludge.

Removal of nitrate nitrogen in water using zero iron as a catalyst can be carried out in neutral conditions or acid conditions with the addition of acid.In the case of neutral conditions, the reaction rate is slow and the treatment rate is slow. It is more advantageous to proceed at low pH. However, since the pH of water is increased in the removal reaction of nitrate nitrogen, continuous acid injection is required to maintain a low pH, the reaction rate is reduced by corrosion and surface modification of ferrous iron, and iron by-products are generated. have. In addition, the low pH conditions have a problem that the total amount of nitrate nitrogen is reduced to ammonia nitrogen to require additional post-treatment for ammonia.

It is also possible to remove the nitrate nitrogen by electrolysis by filling the activated carbon between the electrodes, the water added to the activated carbon is alkaline because there is a problem that pre-treatment through backwashing and pickling due to the pH of the water is increased. In addition, filled with activated carbon, which is a conductive material, between the electrodes, and the activated carbons are electrically connected to each other, so that the electrode area becomes wider, so that the bypass current increases excessively as the applied voltage increases, thereby increasing the total amount of energization. I also have

Drinking water is not only contaminated with nitrate nitrogen, but also by E. coli. E. coli is present in drinking water above a certain concentration can cause food poisoning. Conventional disinfection methods for removing E. coli from water to be used as drinking water are disinfection using ultraviolet rays, ozone disinfection or chlorine gas. UV disinfection or ozone disinfection is easy to maintain the device, but the initial cost of the facility is excessive. Disinfection using chlorine gas is difficult to store and handle toxic gases. When using liquids or solid disinfectants such as NaOCl and CaOCl2, water supply is small and fluctuates so that proper injection is very difficult. The formation of carcinogens such as halomethanes (THMs) is a problem. Therefore, there is a great need for a technology capable of simultaneously removing nitrate nitrogen and E. coli from water to be used as drinking water while solving the above problems.

Therefore, the problem to be solved by the present invention is to provide an electrolytic cell device for water purification that can effectively remove the nitrate nitrogen and E. coli in the water without the addition of additional chemicals, easy to interlock control.

The present invention includes a positive electrode, a negative electrode and a filler formed between the positive electrode and the negative electrode to achieve the above object, the filler provides an electrolytic cell device for water purification, characterized in that the conductive particles and insulating particles are mixed.

According to one embodiment of the present invention, the conductive particles may be electrically separated by insulating particles.

According to another embodiment of the present invention, the conductive particles may be zero iron.

According to another embodiment of the present invention, the insulating particles may be silica sand.

According to another embodiment of the present invention, the mixing ratio of the conductive particles and the insulating particles is preferably 1: 1.5 to 1.5: 1.

According to another embodiment of the present invention, the positive electrode is a niobium electrode coated with platinum, the negative electrode is preferably a stainless electrode.

According to another embodiment of the present invention, the difference between the voltage applied to the positive electrode and the negative electrode is preferably 50 to 80V.

According to another embodiment of the present invention, the electrolytic cell apparatus further includes a water inlet and a water outlet, the water inlet may be formed at a lower position than the water outlet.

According to another embodiment of the present invention, the mixing ratio of the conductive particles forming the filler to the insulating particles is preferably lowered toward the water outlet from the water inlet.

According to another embodiment of the present invention, a mesh layer is formed between the fillers and the fillers are separated into a plurality of groups, and at least one of the plurality of groups has a mixing ratio of the other group, the conductive particles, and the insulating particles. Can be different.

The electrolytic cell apparatus according to the present invention generates a microcurrent at a high voltage of the conductive particles induced by the voltage applied to the electrode to remove nitrate nitrogen, so that a low pH condition is not required, as in the case of using ductile iron as a catalyst. Therefore, it does not need additional input of drugs such as acids. This effect allows the water purification apparatus to operate unattended, thereby reducing the operating cost of the purification apparatus. In addition, since the conductive particles filled between the electrodes are electrically separated by the insulating particles, each conductive particle behaves as if it were one electrolytic cell, so that the moving distance of the contaminants is shortened. It is possible to process a low electrolyte solution, each particle in the entire electrolytic cell to form a micro-current bypass current is reduced, so that when the high voltage is applied to form a low current can lower the amount of current.

In the electrolytic cell apparatus according to the present invention, since the treatment is performed at a relatively high pH condition as compared to the conventional treatment method using a ductile iron as a catalyst, ammonia nitrogen converted from nitrate nitrogen can be degassed in a gaseous state. In addition, it has the effect of electro-disinfection (ED), which does not cause disinfection by-products, which has been a problem in the conventional disinfection method by chlorine gas, and it is possible to operate unattended operation simply because of interlocking control. Can also be represented.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The electrolyzer device of the present invention comprises a positive electrode, a negative electrode and a filler formed between the positive electrode and the negative electrode, the filler is characterized in that the conductive particles and the insulating particles are mixed, the conductive particles are electrically separated by the insulating particles.

1 shows an electrolytic cell apparatus of the present invention. Referring to FIG. 1, an electrolyzer device 100 includes a water supply device including a water storage container 101 and a feed water pump 102, and an electrolytic cell including a positive electrode 103, a negative electrode 104, and a filler 105. And a power supply unit 106 for applying a voltage to the positive electrode 103 and the negative electrode 104. The water supplied to the water inlet 107 passes through the electrolyzer and exits to the water outlet 108 to remove nitrate nitrogen and E. coli in the water. At this time, the water inlet 107 is advantageously formed at a position lower than the water outlet 108, if the water inlet 107 is formed at a position higher than the water outlet 108, the water is moved by gravity because the passage of water This is because there is a limit in controlling the speed.

2 is a view for separately explaining the electrolytic cell portion in the electrolytic cell device for water purification of the present invention. Referring to FIG. 2, the electrolytic cell includes a positive electrode 103 and a negative electrode 104, and a filler in which conductive particles 105a and insulating particles 105b are mixed is filled therebetween. The electroconductive particle 105a is electrically isolate | separated by the insulating particle 105b. The meaning that the conductive particles 105a are electrically separated means that insulating particles are positioned between the conductive particles, thereby preventing contact between the conductive particles. In the present specification, when at least 10% of the entire conductive particles do not come into contact with other conductive particles, the conductive particles are electrically separated.

3 is a view for explaining the effect that the conductive particles are electrically separated. In the drawings, the insulating particles are not shown for convenience of description, and the size of the conductive particles is also exaggerated than the actual size and drawn large. Referring to FIG. 3, when a voltage is applied to the positive electrode and the negative electrode to form an electric field therebetween, both ends of the filled conductive particles serve as an anode and a cathode, and an electrolysis reaction may occur at individual anodes and cathodes. The electrolysis reaction occurs at both ends of the conductive particles so that each conductive particle behaves as if it were a single electrolyzer, and electrolysis of water may occur in a large number of fine electrolyzers. In this case, since the size of each electrolytic cell made of conductive particles is small, the moving distance of the contaminants to be removed by electrolysis is shortened, so that the treatment of water with low concentration of reactant and low electrical conductivity becomes possible. In addition, since each particle forms a fine current in the entire electrolytic cell, the bypass current is reduced, thereby forming a low current when high voltage is applied, thereby lowering the amount of energization.

In the present invention, as the conductive particles, zero iron may be used. Young iron is a substance used as a catalyst for removing nitrate nitrogen in water, and in the present invention, it is used as a particle electrode using the conductivity of zero iron. Reactions for removing nitrate nitrogen using zero iron as a catalyst and for removing nitrate nitrogen by electrolysis as in the present invention are shown in Schemes 1 and 2, respectively.

Scheme 1

_{^{NO 3 - + 4Fe 0 + 10H}} + -> 4Fe 2 + + NH 4 + + 3H 2 O

Scheme 2

^{_{NO 3 - + 7H 2 O +}} 8e → NH 4 + + 10OH - ( cathode reaction)

As shown in Scheme 1, since a low pH is required in the catalytic reaction using iron ions, additional acid injection is required, and most of the nitrate nitrogen is converted into ammonia and is present in water. On the contrary, when the nitrate nitrogen is treated in the water using the electrolytic cell apparatus of the present invention, the reaction may occur at a high pH as in Scheme 2, so that the produced ammonia is degassed into the atmosphere to maintain a low ammonia concentration in the water. The need for additional acid injection in the present invention can prevent the environmental pollution and bring about the beneficial effect of unmanned operation without human effort in the operation of the device, automatic ammonia degassing can omit the additional ammonia removal process. It has an effect. However, it is also possible to add an air stripping process for the removal of some of the ammonia that may remain after the treatment, but the amount of ammonia to be removed will be much smaller than in the catalytic reaction with zero iron.

In the present invention, the insulating particles may be silica sand. Silica sand is an insulating particle that can be obtained most easily as sand particles having a main component such as oxidized Sicon. In addition to the silica sand, various inorganic particles or polymer particles may be used as the insulating particles, and germanium particles may be used in order to elute minerals beneficial to the human body in drinking water. In the present invention, it is possible to control the sizes of the conductive particles and the insulating particles, in order to maximize the effect that the conductive particles are separated from the electrical size of the insulating particles is calculated in consideration of the sedimentation rate of the law of Stock of the conductive particles. This is because the specific gravity of the nonferrous iron used as the conductive particles is larger than the insulating particles, so that they settle down the electrolyzer over time. At this time, the size of the insulating particles is calculated in consideration of the sedimentation rate of the law of Stock of the conductive particles. In the present invention, the treatment efficiency of nitrate nitrogen is also related to the mixing ratio of the conductive particles and the insulating particles. Treatment of nitrate nitrogen is effective when the mixing ratio of the conductive particles and the insulating particles is 1: 1.5 to 1.5: 1. If the mixing ratio is less than 1: 1.5, the number of the conductive particles is insufficient, so that the processing speed of nitrate nitrogen is low. If the mixing ratio is more than 1.5: 1, the probability that the conductive particles are in contact with each other increases, so that the treatment effect of the nitrate nitrogen is lowered.

Platinum coated niobium electrode may be used as the positive electrode used in the electrolytic cell apparatus of the present invention. Platinum coated niobium electrode is an insoluble electrode made of a material several hundred times better corrosion resistance than stainless steel can improve the durability of the electrolytic cell. In addition, a stainless steel electrode may be used as the negative electrode, since the oxidation reaction does not occur in the negative electrode like the positive electrode, because it is advantageous to use a relatively inexpensive stainless steel electrode.

The voltage applied between the anode and the cathode of the electrolyzer should be properly adjusted depending on the amount of water supplied, the concentration of nitrate nitrogen contained in the water, and the like. Preferably, the applied voltage is 50V to 80V. If the applied voltage is less than 50V, no current flows, and if the applied voltage exceeds 80V, the reduction and removal rate of nitrate nitrogen is faster, but the amount of electricity increases, which is disadvantageous in terms of maintenance.

The mixing ratio of the conductive particles and the insulating particles of the filler used in the electrolytic cell device for water purification of the present invention may be set differently at the water inlet and outlet. 4 shows an electrolytic cell in which the mixing ratio of the conductive particles and the insulating particles is spatially differently controlled. Referring to FIG. 4, the relative ratio of the conductive particles to the insulating particles decreases from the water inlet side to the water outlet side. The concentration of nitrate nitrogen in the water is lowered toward the water outlet from the water inlet, because the water flowing into the positive electrode of the electrolytic cell is converted to ammonia nitrogen by electrolysis and the concentration of nitrate nitrogen decreases as it moves toward the negative electrode. Therefore, the mixing ratio of the conductive particles in the water inlet side with a relatively high nitrate nitrogen concentration is controlled to be high to increase the amount of nitrate nitrogen removed, and the mixing ratio of the conductive particles in the water outlet side with the relatively low concentration of nitrate nitrogen is determined. Adjusting to lower the removal of nitrate nitrogen can increase the overall water treatment efficiency.

5 shows a means for spatially controlling the mixing ratio of the conductive particles in the fill. Referring to FIG. 5, a mesh layer 110 is formed between the fillings 105a and 105b of the electrolytic cell. The mesh layer 110 is a means for spatially controlling the mixing ratio of the conductive particles in the filler. The method of forming the fillers 105a and 105b between the electrodes using the mesh layer 110 is as follows. First, the filling material having the highest mixing ratio of the conductive particles is filled on the positive electrode 103, the mesh layer 110 is formed thereon, and the filling material having the mixing ratio of the conductive particles is filled therein, and the mesh layer 110 is again placed thereon. After forming, the negative electrode 104 is formed after filling the filler having the lowest mixing ratio of the conductive particles. When the filler is filled in the electrolytic cell in this manner, it is easy to fill the filler so that the mixing ratio of the conductive particles is different, and it is possible to prevent the conductive particles from moving to other regions by the flow of water. The mesh layer may be made of a metal material or a polymer material, and it is more preferable that the individual conductive particles are made of a polymer material which is an insulator for the particle electrodes to function.

The electrolytic cell device for water purification of the present invention also has a disinfecting effect of removing E. coli present in water. Disinfection by electrolysis is accomplished by hydroxy radicals (OH ·) produced at the anode. Disinfection using hydroxide radicals can reduce the production of disinfection by-products, which are a problem in disinfection by chlorine, and enables unmanned operation because the interlocking control is simple.

Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

Example  One

An electrolytic cell device for water purification was prepared in the following manner. A positive electrode and a negative electrode made of platinum and niobium coated with niobium and stainless steel, respectively, are installed on the upper and lower acrylic structures each having a volume of 320 mL, a width of 4 cm, a height of 8 cm, and a height of 10 cm. The mixed filler was filled, and a water inlet was formed at the bottom of the acrylic structure, and a water outlet was formed at the top. A power supply was applied to the positive electrode and the negative electrode, and water was supplied to the water inlet through the feed water pump.

Example  2

An electrolytic cell device for water purification was prepared in the same manner as in Example 1, except that the duct iron and silica were mixed 1: 2.

Example  3

An electrolytic cell device for water purification was prepared in the same manner as in Example 1, except that the duct iron and silica were mixed 2: 1.

Example  4

An electrolytic cell device for water purification was prepared in the same manner as in Example 1 except that the ferrous iron and the silica were mixed at 4: 1.

Experimental Example  One

The electrolytic cell apparatus for water purification according to Examples 1 to 4 was treated with water containing nitrate nitrogen. The initial concentration of nitrate nitrogen in water was 25 mg / L NO ₃ ^-- N, the electrolytic voltage was 50V, the electrolysis temperature was 20 ± 1 ℃, the electrolysis time was 180 minutes. 6 compares the concentration change of nitrate nitrogen over time. In Example 1, the treatment time of nitrate nitrogen was the shortest, and after 1 hour, the concentration was lower than the drinking water quality standard (10 mg / L), and after 90 minutes, 92% of the initial concentration was removed. . Table 1 compares the time to reach lower than the drinking water quality standard (5 mg / L) when treated with water containing nitrogen nitrate using the electrolytic cell device of Examples 1 to 4.

TABLE 1

Example 1 Example 2 Example 3 Example 4 Processing time (H) 0.4 One 3 More than 3

Experimental Example  2

The electrolyzer device for water purification according to Example 1 was treated with water containing nitrate nitrogen under the same conditions as in Experimental Example 1, and this was compared with the result of removing nitrate nitrogen using zero iron as a catalyst. Figure 7 (a) is the result of the treatment of water with the electrolytic cell device of the embodiment, Figure 7 (b) shows the result of the treatment of water using a zero iron as a catalyst. 7 (a) and 7 (b), when water is treated with the electrolytic cell apparatus of the present invention, the rate of the concentration of nitrate nitrogen decreases over time as compared with the case of using iron-based iron as a catalyst. It can be seen that the fast final concentration is lower, and the pH is maintained, so that deaeration of ammonia occurs and the concentration of ammonia in water is kept low.

Experimental Example  3

In order to confirm the effect of E. coli disinfection of the electrolytic cell device for purification of water of Example 1, E. coli was injected and cultured in water to evaluate the difference before and after treatment. Petnifilm (petnifilm) was inoculated in an amount of 1mL and incubated at 35 ℃ for 24 to 48 hours. As shown in (a) of FIG. 8, the untreated water in the electrolytic cell was confirmed as E. coli by gas bubbles in the red cells, and bubbles in the blue cells were confirmed in E. coli. However, in the water treated with the electrolytic cell of Example 1, the E. coli group was not detected as shown in FIG.

Experimental Example  4

The removal rate of nitrogen nitrate and the amount of current flowing through the electrolytic apparatus were measured by varying the voltage applied to the positive electrode and the negative electrode using the electrolytic cell device for water purification of Example 1. 9 (a) and 9 (b) set the applied voltages between the electrodes to 50 V, 100 V, and 150 V in the electrolytic cell for water purification of Example 1, and measured the current and the removal rate of nitrate nitrogen. Referring to FIG. 9A, the amount of current increases as the applied voltage is increased. This is considered to be because the amount of the bypassed current increases as the applied voltage increases, and when the applied voltage is less than 50 V, no current flows and the electrolytic apparatus did not operate. Referring to Figure 9 (b), it can be seen that as the applied voltage is increased the removal rate of nitrate nitrogen is faster. As the applied voltage of the electrolytic device increases, the removal rate of nitrate nitrogen increases, but the amount of electricity consumed increases (7 to 10 times 50V for 100V and 25 to 30 times 50V for 150V). In terms of efficiency and maintenance of the electrolytic device, the voltage applied is preferably in the range of 50 to 80V.

1 shows an electrolytic cell apparatus of the present invention.

2 is a view for separately explaining the electrolytic cell portion in the electrolytic cell apparatus of the present invention.

3 is a view for explaining the effect that the conductive particles are electrically separated.

4 shows an electrolytic cell in which the mixing ratio of the conductive particles and the insulating particles is spatially differently controlled.

5 shows a means for spatially controlling the mixing ratio of the conductive particles in the fill.

6 compares the concentration change of nitrate nitrogen over time.

FIG. 7 (a) shows the result of treating water with the electrolytic cell apparatus of Example 1, and FIG. 7 (b) shows the result of treating water using zero iron as a catalyst.

Figure 8 shows the results of disinfecting E. coli in the electrolytic cell device of the present invention.

9 (a) and 9 (b) set the applied voltages between the electrodes to 50 V, 100 V, and 150 V in the zero-ferrous bipolar electrolytic apparatus of Example 1, and measured the current and the removal rate of nitrate nitrogen.

Claims (10)

Positive electrode; Negative electrode; And And a filler formed between the positive electrode and the negative electrode, wherein the filler is a mixture of zero-ferrous iron particles and insulating particles. delete delete The method of claim 1, The insulating particle is an electrolytic cell for water purification, characterized in that the silica sand. The method of claim 1, The mixing ratio of the electroconductive particle and insulating particle is 1: 1.5 to 1.5: 1, the electrolytic cell device for water purification. The method of claim 1, The positive electrode is a niobium electrode, the negative electrode is a water purification electrolytic cell, characterized in that the stainless steel electrode. The method of claim 1, Electrolytic device for water purification, characterized in that the difference between the voltage applied to the positive electrode and the negative electrode is 50 to 80V. The method of claim 1, The electrolyzer device further includes a water inlet and a water outlet, wherein the water inlet is formed at a lower position than the water outlet. The method of claim 8, Electrolytic apparatus for water purification, characterized in that the mixing ratio of the conductive particles forming the filler to the insulating particles is lowered toward the water outlet from the water inlet. The method of claim 1, The mesh layer is formed between the fillers and the fillers are separated into a plurality of groups, wherein at least one group of the plurality of groups has a different mixing ratio between the other group and the conductive particles and the insulating particles.

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