CN1125782C - Suspension and photocatalytic oxidization process and equipment combined with membrane separator for treating water - Google Patents

Abstract

The invention belongs to the technical field of water treatment using photocatalyst, and relates to a suspended photocatalytic oxidation water treatment method and a device thereof combined with membrane separation equipment. It includes a reactor equipped with forced circulation means, the reactor is divided into two areas, a plurality of ultraviolet lamps are set in a certain area of the reactor, and another area inside the reactor is equipped with a membrane separation device, the The reactor is provided with a water inlet and a water outlet, and the water outlet is connected with a membrane separation device. The invention has the advantages of high reaction rate, large treatment capacity, easy operation, recyclable catalyst and continuous operation, and can be a practical device for industrial sewage treatment.

Description

Suspension photocatalytic oxidation water treatment method and its device combined with membrane separation equipment

technical field

The invention belongs to the technical field of water treatment methods and devices using photocatalysts, and in particular relates to photocatalytic oxidation treatment methods and devices suitable for water containing refractory organic matter.

Background technique

In recent years, with the development of industry and economy, many discharged water containing toxic and harmful substances that are difficult to biodegrade have continuously entered the environment, causing great harm to industrial and agricultural production, people's lives and human health. How to effectively dispose of these polluted water has become a hot spot in the field of environment. Photocatalytic oxidation technology is a newly emerging advanced oxidation technology, because it has (1) the ability to completely mineralize organic matter into CO ₂ , H ₂ O and mineral acids that are almost harmless to the environment; (2) there is almost no choice (3) The reaction conditions are mild, and there are some advantages such as no special requirements on the reaction temperature and pH value, so that its application in the environmental field has a very bright future.

In general, the main difference in the application of photocatalytic oxidation technology in sewage treatment lies in the type of reactor: one is a flat-plate reactor that uses natural light (sunlight) as the light source and adopts catalyst immobilization technology; One is a suspension system photocatalytic oxidation reactor that uses artificial light sources (ultraviolet lamps) as irradiation light sources and powder catalysts.

At present, domestic literature such as Wang Yi-zhong, et al (Journal of Environmental Sciences, Vol.10, No.3, pp.291-295, 1998) reports on photocatalytic oxidation reactors are all first-type reactors. The schematic diagram of the structure is shown in FIG. 1 , which is composed of a plate reactor 101 , a water outlet tank 102 , a water tank 103 , a circulation pump 104 , a flow meter 105 and a stirrer 106 . The reactor is a batch reactor, and when the concentration of pollutants in the water tank reaches the discharge standard, a reaction cycle ends.

There are following defects in the above-mentioned reactor: (1) this reactor is a batch reactor, and it is very inconvenient to operate; (2) a feature of the plate reactor is exactly that the catalyst is fixed on the surface of the plate, which greatly reduces the available The specific surface area of the catalyst used in the catalytic reaction greatly reduces the removal rate of pollutants in the reactor; (3) the flat-plate reactor mostly uses the sun light source, because the intensity of the sun light varies significantly with seasons, weather and time, giving the reaction (4) The proportion of ultraviolet rays that can trigger photocatalytic oxidation reactions in sunlight is very low (about 4%), which greatly limits the speed of the reaction.

For the second type of reactor, because the catalyst is in a suspended state, (1) the catalyst particles can be as small as possible and contain pores, which increases the specific surface area of the particles; (2) increases the utilization efficiency of the catalyst particle surface; ( 3) The probability of contacting the surface of catalyst particles with pollutants is increased, and the reaction rate is much higher than that of the first type of reactor. However, the important reason why it cannot be popularized is the separation and continuous operation of the catalyst. In some studies, coagulation and precipitation methods have been tried to separate the powder catalyst from the treated water, but this method is cumbersome to operate, and the catalyst is difficult to recover and reuse. For example, in the technique disclosed in JP-A-9-174067, a polymer coagulant is added to the treated solution to separate the powdery photocatalyst from the treated water. Due to the above reasons, the practical application of photocatalytic oxidation technology has been greatly restricted.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to propose a suspension photocatalytic oxidation water treatment method and its device, which have the advantages of high reaction rate, large processing capacity, easy operation and catalyst can be recycled and reused. The advantage of continuous operation can become a practical device for industrial sewage treatment.

A suspension photocatalytic oxidation water treatment method combined with membrane separation equipment proposed by the present invention is characterized in that:

1) Mixing porous structure, powdery catalyst particles and water to be treated to form a mixed solution of suspended catalyst;

2) sending said mixed solution into the reactor, and carrying out forced circulation to the mixed solution, to enhance mass transfer efficiency;

3) Put the ultraviolet lamp directly into the reactor, and the light generated by it can be effectively used by the catalyst;

4) A membrane separation device is installed inside the reactor to separate the treated water from the catalyst particles, and the treated water is filtered out of the reactor after being filtered by the membrane separation device, and the catalyst is retained in the reactor for recycling, and the water treatment process realizes continuous run.

The suspension photocatalytic oxidation water treatment device combined with the membrane separation equipment proposed by the present invention is characterized in that it includes a reactor equipped with a forced circulation device, the reactor is divided into two areas, a plurality of ultraviolet The lamp is arranged in a certain area inside the reactor, and another area inside the reactor is provided with a membrane separation device. The reactor is also provided with a water inlet and a water outlet, and the water outlet is connected with the membrane separation device.

Said forced circulation device can be an air supply device arranged at the bottom of the reactor and a flow guiding device arranged inside the reactor; it can also be an agitator arranged at the bottom of the reactor and a flow guiding device arranged inside the reactor.

The deflector can be a deflector, which divides the reactor into inner and outer regions; it is also a deflector, which divides the reactor into left and right regions. , right two areas. A plurality of swirl plates can also be arranged on the said deflector.

The shell of the reactor can be cylindrical or cuboid.

The water treatment method and device using the photocatalyst of the present invention have the following effects.

(1) In the outer shell of the reactor, the mixed solution of raw water containing organic matter and powdery photocatalyst is forced to circulate, and irradiated with ultraviolet light, so that the powdery photocatalyst and organic matter are evenly stirred, and the organic matter and photocatalyst are effectively realized. surface contact. In this way, organic matter can be effectively oxidized and decomposed, shortening the treatment time of raw water and correspondingly increasing the amount of treated water.

(2) The mixed liquid is forced to circulate in the form of swirling flow, and the photocatalyst and organic matter can be stirred more uniformly, so that the organic matter can be oxidized and decomposed more efficiently. The photocatalyst is a porous particle, and the surface area of the photocatalyst is larger than that of ordinary particles. In this way, the chance of contact between the organic matter and the surface of the photocatalyst increases, and the organic matter can be oxidized and decomposed more effectively.

Description of drawings

Fig. 1 is a schematic diagram of the formation of a flat photocatalytic oxidation reactor in the prior art.

Fig. 2 is a schematic diagram of the composition of Embodiment 1 of the present invention, wherein (a) is a side view, and (b) is a sectional view along line A-A.

Fig. 3 is a schematic diagram of the structure of Embodiment 2 of the present invention, wherein (a) is a side view, and (b) is a B-B line sectional view.

Fig. 4 is a schematic diagram of the third embodiment of the present invention, wherein (a) is a side view, and (b) is a C-C sectional view.

Detailed ways

Embodiments of the photocatalytic oxidation water treatment method and device related to the present invention are described in detail below in conjunction with the accompanying drawings.

Embodiment one

Fig. 2 shows the composition of the water treatment device of embodiment one, and this device is by cylindrical reactor shell 1A, air supply device (aeration device) 2, guide tube 3A, swirl plate 4, ultraviolet lamp 5, membrane module 6 and outlet pipe 7 form. In the figure, the outer casing 1A of the reactor is a hollow cylindrical structure, and its axis is perpendicular to the horizontal plane. A water inlet 1a is provided on the upper side of the outer shell of the cylindrical reactor, and a gas inlet 1c from the air supply device is provided in the center of the bottom. A cylindrical guide tube 3A is set in the middle of the device to divide the interior of the device into a central area Kt and a peripheral area Kg. The inner wall of the housing 1A and the inner and outer walls of the guide tube 3A are equipped with a plurality of swirls. The plate 4 and a plurality of ultraviolet lamps 5 are evenly arranged in the peripheral area Kg, the membrane module 6 is arranged in the center of the central area Kt, and the outlet pipe 7 communicates with the upper end of the membrane module 6 .

The structure of the present embodiment is described in detail as follows in conjunction with Fig. 2:

The raw water flowing in from 1a is mixed with the photocatalyst P to become a mixed liquid X, which is distributed in the cylindrical reactor shell 1A. After photocatalytic oxidation, the treated water is separated through the membrane module 6 and discharged from the outlet pipe 7 . Wastewater contains various organic matter U including refractory organic matter. There are many micropores on the surface of photocatalyst P (such as powdery titanium dioxide TiO2). The air supply device 2 supplies compressed air at a certain pressure to the above-mentioned gas inlet 1c, and the mixed liquid X in the cylindrical reactor shell 1A is forced to circulate with this compressed air. As shown in Figure 2(b), the guide tube 3A is also a bottomless hollow cylindrical structure, its diameter is smaller than that of the cylindrical reactor shell 1A, and its axis is consistent with the central axis of the cylindrical reactor shell 1A. The draft tube 3A divides the cylindrical reactor shell 1A into a central area Kt and a peripheral area Kg.

Since the air inlet 1c is set in the center of the bottom, the compressed air entering the reactor makes the mixed liquid X in the central area Kt form an upward flow from bottom to top, and in the peripheral area Kg form a top-to-bottom downward flow. That is, the mixed solution X in the cylindrical reactor shell 1A circulates between the central region Kt formed by the draft tube 3A and the peripheral region Kg as indicated by the arrows.

Several swirl plates 4 with certain directions are installed on the inside and outside of the guide tube 3A and the inner wall of the cylindrical reactor shell 1A, the purpose of which is to generate a swirl flow in the mixed liquid X circulating between the central area Kt and the peripheral area Kg . For example, in this figure, the rotating plate 4 installed inside the guide tube 3A is inclined at a certain angle to the right side of the normal line of the guide tube 3A, so that the mixed liquid X can circulate in a clockwise swirling flow from bottom to top in the central area Kt. And in the outer area Kg, since the rotating plate 4 is inclined at a certain angle to the right side relative to the normal line of the inner wall of the cylindrical reactor shell 1A, and is inclined at a certain angle to the left side with respect to the normal line of the outer wall of the draft tube 3A, the mixed liquid X is The counterclockwise swirl circulates from top to bottom.

A plurality of ultraviolet lamps are installed in the outer area Kg to irradiate the mixed liquid X containing the organic matter U and the powdery photocatalyst P. The irradiation of ultraviolet rays can excite the photocatalyst P to catalyze the oxidation and decomposition of organic matter U. The membrane module is arranged in the center of the central area Kt for separating the mixed liquid X and the powder catalyst. The membrane module adopts inorganic ceramic membrane or organic membrane such as hollow fiber membrane and flat membrane.

The working principle of this embodiment is described in detail as follows:

In the water treatment device of the present embodiment, the raw water to be treated flows into the cylindrical reactor outer shell 1A sequentially and continuously from the raw water inlet 1a on the top of the cylindrical reactor outer shell 1A, and in the reactor outer shell, the waste water and The powdery photocatalyst P is mixed to form the mixed liquid X. The wastewater that has been fully oxidized and decomposed is filtered through the membrane module 6 and becomes treated water, which is discharged from the outlet pipe 7 . During the period from inflow to discharge, the raw water is treated as follows:

Because the cylindrical reactor shell 1A is provided with a guide tube 3A, the mixed liquid X located in the central area Kt becomes an upward flow due to the action of compressed air entering from the gas inlet 1c, and then flows along the outer peripheral area Kg as a downward flow. Descends, is then reflected by the bottom surface of the cylindrical reactor shell 1A and rises again along the central region Kt due to the action of the compressed air. That is, the mixed liquid X circulates repeatedly between the central area Kt and the outer peripheral area Kg partitioned by the draft tube 3A.

During circulation, the above-mentioned ascending flow becomes a swirling flow rotating clockwise along the forward direction due to the inner and outer sides of the deflector 3 or the swirl plate 4 arranged on the inner wall of the cylindrical reactor shell 1A; A swirl that rotates counterclockwise in the forward direction. In this way, the mixed liquid X circulates and swirls in the cylindrical reactor shell 1A, and the organic matter U and the photocatalyst P are stirred uniformly, and the chance of contacting the surface of the photocatalyst P with the organic matter U increases. In addition, the photocatalyst P is a porous particle having a large number of micropores, and has a larger surface area than normal particles, so that the surface of the photocatalyst P is more likely to contact organic substances.

Thus, in a state where the organic matter can better contact with the photocatalyst, the ultraviolet light emitted by the ultraviolet lamp 5 irradiates the photocatalyst P to excite the photocatalyst P to oxidize the organic matter U in the wastewater.

The fully oxidatively decomposed mixed solution X is filtered through the membrane module 6 to intercept the photocatalyst P, and then discharged through the outlet pipe 7 as treated water.

Using this embodiment, not only the mixed solution X can be efficiently oxidized and decomposed in a short period of time, but also the components other than the photocatalyst can be selectively separated from the mixed solution X by using the membrane module 6, so the outer shell of the cylindrical reactor The amount of photocatalyst P in 1A can be guaranteed to be maintained at the original level. The amount of photocatalyst is easy to manage.

Embodiment two

Fig. 3 shows the composition of the suspended photocatalytic oxidation water treatment device of the second embodiment, and this device is made of cylindrical reactor shell 1B, air supply device (aeration device) 2, guide plate 3B, ultraviolet lamp 5, membrane assembly 6 and outlet pipe 7 form.

In Fig. 3, the outer casing 1B of the reactor is a hollow cylindrical structure, and its axis is perpendicular to the horizontal plane. A water inlet 1a' is provided on the upper side of the outer shell of the cylindrical reactor, and a gas inlet 1c' from the air supply device is provided in the center of the bottom. The inside of the device is vertically provided with a flat deflector 3B to divide the inside of the device into a reaction zone K1 and a recovery zone K2. A plurality of ultraviolet lamps 5 are uniformly arranged in the reaction zone K1, and a membrane module 6 is arranged in the recovery zone K2. At the central position, the water outlet pipe 7 communicates with the upper end of the membrane module 6 . In this cylindrical reactor outer shell 1B, the raw water to be treated flows in from the raw water inflow port 1a' provided on the upper side, and after being mixed with the photocatalyst P, it becomes a mixed liquid X, which is distributed in the cylindrical reactor outer shell 1B, and after treatment After being filtered by the membrane module 6, it is discharged from the drain pipe 7, which is similar to the cylindrical reactor shell 1A in the first embodiment described above. However, as shown in the figure, the interior of the reactor is divided into two parts by a flat guide plate 3B, namely: a reaction zone K1 and a recovery zone K2.

In the central portion of the above-mentioned reaction zone K1, several ultraviolet lamps 5 are arranged parallel to the central axis of the cylindrical reactor outer shell 1B. In the central part of the recovery area K2, a membrane module is installed. The gas inlet 1c' is located below the membrane module 6, and the compressed air is supplied by the air supply device 2.

In this embodiment, as shown by the arrow in the figure, the mixed liquid X circulates between the reaction zone K1 and the recovery zone K2 under the action of compressed air. Through such circulation, the photocatalyst P in the mixed solution X is uniformly stirred, and the organic matter U is oxidized and decomposed by ultraviolet radiation in the reaction zone K1. Then, the fully oxidized and decomposed mixed liquid X passes through the membrane module 6 installed in the recovery area K2 to filter and intercept the photocatalyst, and is discharged through the water distribution pipe 7 as treated water.

This embodiment is suitable for small-scale wastewater treatment equipment. The volume of the cylindrical reactor outer casing 1B is smaller than that of the above-mentioned cylindrical reactor outer casing 1A. However, the mixed liquid X is used as a circulating flow to stir evenly with the photocatalyst P, so that the surface of the photocatalyst P and the organic matter U can be easily contacted, the reaction time can also be shortened, and the oxidative decomposition efficiency of the organic matter can be improved. In addition, by using the membrane filter module 6 to ensure that the amount of the photocatalyst P in the cylindrical reactor outer casing 1B can be kept in the original state, the amount of photocatalyst can be easily managed.

Embodiment three

Fig. 4 shows the composition of the suspended photocatalytic oxidation water treatment device of the third embodiment, this device is made of cuboid reactor shell 1C, air supply device (aeration device) 2, guide plate 3C, ultraviolet lamp 5, membrane assembly 6 and outlet pipe 7 form.

In Fig. 4, the outer casing 1C of the reactor is a hollow cuboid structure, and its axis is perpendicular to the horizontal plane. The upper side of the cuboid reactor shell 1C is provided with a water inlet 1a", the center of the bottom is provided with a gas inlet 1c" from the air supply device, and a membrane module 6 is provided at the center. A flat deflector 3C is vertically arranged inside the device to divide the inside of the device into a reaction area M1 and a recovery area M2. A plurality of ultraviolet lamps 5 are uniformly arranged in the reaction area M1, and a membrane module 6 is arranged in the recovery area M2. In this rectangular parallelepiped reactor shell 1C, the raw water to be treated flows in from the raw water inlet 1a" provided on the upper side, mixes with the photocatalyst P and becomes a mixed liquid X, which is distributed in the cylindrical reactor shell 1C, and after treatment After being filtered by the membrane module 6, it is discharged from the drain pipe 7, which is similar to the cylindrical reactor shell 1B of the above-mentioned second embodiment. Equally, the inside of the reactor is divided into two parts by the flat deflector 3C , That is: reaction zone M1 and recovery zone M2.But unlike the second embodiment, the cuboid reactor shell 1C is a cuboid structure, and the reaction zone M1 and recovery zone M2 are also cuboid structures.

In the central part of the above-mentioned reaction area M1, several ultraviolet lamps 5 are arranged perpendicular to the bottom surface of the cuboid reactor shell 1C. In the central part of the recovery area M2, a membrane module is installed. The gas inlet 1c" is located below the membrane module 6, and the compressed air is supplied by the air supply device 2.

In this embodiment, as indicated by the arrow, the mixed liquid X circulates between the reaction zone M1 and the recovery zone M2 under the action of compressed air. Through such circulation, the photocatalyst P in the mixed solution X is uniformly stirred, and the organic matter U is oxidized and decomposed by ultraviolet radiation in the reaction region M1. Then, the fully oxidized and decomposed mixed solution X passes through the membrane module 6 installed in the recovery area M2 to filter and intercept the photocatalyst, and is discharged through the water distribution pipe 7 as treated water.

This embodiment is suitable for small-scale drainage treatment equipment. The volume of the cuboid reactor outer casing 1C is smaller than that of the cylindrical reactor outer casing 1A in the first embodiment. However, the mixed liquid X is used as a circulating flow to stir evenly with the photocatalyst P, so that the surface of the photocatalyst P and the organic matter U can be easily contacted, and the reaction time can also be shortened, and the oxidative decomposition efficiency of the organic matter can be improved. In addition, the use of the membrane filter assembly 6 ensures that the amount of photocatalyst P in the outer casing 1C of the cuboid reactor can be kept at the original state, and the amount of photocatalyst is easy to manage.

The present invention is not limited to the structures of the above-mentioned embodiments, and the following changes are also conceivable.

(1) In addition to the air supply device 2 as the circulation means in the above-mentioned embodiments, devices such as a stirrer can also be used to force the mixed liquid X to circulate.

(2) In addition to using the deflector 3 as the swirl means in the above-mentioned second and third embodiments, a swirl plate or the like may also be provided on the deflector 3 to turn the mixed liquid X in the central area Kt into a swirl flow.

Claims (10)

1. A suspended photocatalytic oxidation water treatment method combined with membrane separation equipment, characterized in that: 1) Mixing porous structure, powdery catalyst particles and water to be treated to form a mixed solution of suspended catalyst; 2) sending said mixed solution into the reactor, and carrying out forced circulation to the mixed solution, to enhance mass transfer efficiency; 3) Put the ultraviolet lamp directly into the reactor, and the light generated by it can be effectively used by the catalyst; 4) A membrane separation device is installed inside the reactor to separate the treated water from the catalyst particles, and the treated water is filtered out of the reactor after being filtered by the membrane separation device, and the catalyst is retained in the reactor for recycling, and the water treatment process realizes continuous run. 2. The suspended photocatalytic oxidation water treatment device combined with the membrane separation equipment adopting the method as claimed in claim 1, characterized in that it comprises a reactor equipped with forced circulation means, and the reactor is divided into two areas, A plurality of ultraviolet lamps are installed in a certain area of the reactor, another area inside the reactor is equipped with a membrane separation device, the reactor is provided with a water inlet and a water outlet, and the said water outlet is connected to the membrane separation device . 3. The suspended photocatalytic oxidation water treatment device according to claim 2, wherein said forced circulation means is an air supply device arranged at the bottom of the reactor and a diversion device arranged inside the reactor, the diversion The device divides the reactor into two zones. 4. The suspended photocatalytic oxidation water treatment device as claimed in claim 2, characterized in that, said forced circulation means is a stirrer arranged at the bottom of the reactor and a flow guiding device arranged inside the reactor, and the flow guiding device The reactor was divided into two zones. 5. The suspended photocatalytic oxidation water treatment device as claimed in claim 3 or 4, characterized in that, the said diversion device is a diversion cylinder, and the diversion cylinder separates the said reactor into inner and outer two. area. 6. The suspended photocatalytic oxidation water treatment device as claimed in claim 3 or 4, characterized in that, said deflector is a deflector, and the deflector separates said reactor into left and right two area. 7. The suspended photocatalytic oxidation water treatment device according to claim 5, characterized in that a plurality of swirl plates are arranged on the flow guiding device. 8. The suspended photocatalytic oxidation water treatment device according to claim 6, characterized in that a plurality of swirl plates are arranged on the flow guiding device. 9. The suspended photocatalytic oxidation water treatment device as claimed in claim 2, characterized in that the shell of the reactor is in the shape of a cylinder. 10. The suspended photocatalytic oxidation water treatment device according to claim 2, characterized in that, the shell of the reactor is a cuboid.

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