CN115611357A - Photocatalytic/coagulation integrated water treatment process - Google Patents

Abstract

The invention belongs to the technical field of water treatment, and relates to water treatment, in particular to a photocatalysis/coagulation integrated water treatment process, which includes: introducing the source water to be treated into a photocatalysis/coagulation integrated reaction tank, adding a photocatalyst to make It is fully mixed and stirred with the source water to carry out photocatalytic reaction; after the photocatalytic reaction has been carried out for a period of time, add coagulant, mix well, reduce the stirring speed to flocculate and form floc complex; after the floc complex is completely settled , collect, recycle and regenerate, and reuse the regenerated floc complex to the photocatalyst dosing unit. The present invention combines the characteristics of different processes of photocatalysis and coagulation, and uses coagulation to make up for the problem of insufficient turbidity removal by photocatalysis, so that it can be carried out in the same reactor; the present invention is simple to operate and can significantly increase the settling speed of flocs, Reducing the volume of the hydraulic retention time settling equipment in the drinking water treatment process has guiding significance in practical application.

Description

Photocatalytic/coagulation integrated water treatment process

technical field

The invention belongs to the technical field of water treatment and relates to water treatment, in particular to a photocatalysis/coagulation integrated water treatment process.

Background technique

Natural organic matter (NOM) mainly refers to a type of macromolecular organic matter produced by biochemical reactions of animal and plant residues in the natural circulation process, and the main component is humus. At present, it is found that drinking water contains a variety of disinfection by-products (Disinfection by products, DBPs) related to humic acid (Humic acid, HA) in the world. However, the most widely used disinfection method in waterworks is chlorination, which will react with HA during water treatment to generate various carcinogenic, teratogenic and mutagenic disinfection by-products, such as chloroform and haloacetic acid, which seriously threaten Drinking water is safe. In addition, HA will also interfere with the removal of other pollutants in the water treatment process, promote the growth of microorganisms in the pipe network system and accelerate its corrosion, etc.

As a key link in the water treatment process, coagulation can effectively remove turbidity, color, suspended organic matter and pathogenic bacteria in water, and is widely used in the removal of NOM. Studies have shown that coagulation has a strong removal effect on the hydrophobic components of NOM in natural water bodies, but has a limited removal effect on the hydrophilic components. As an advanced oxidation technology, photocatalysis has obvious removal effect on soluble NOM in water, but the effect of removing NOM only by photocatalysis is limited.

Based on this, combining the characteristics of the coagulation and photocatalysis process, the coagulation and photocatalysis take place in the same reactor, and coagulation is used to make up for the problem of insufficient turbidity removal by photocatalysis. Taking the photocatalyst BiFeO ₃ that responds to visible light as an example, a photocatalytic/coagulation integrated system was established, and its operating efficiency was studied, which provided a theoretical reference for the practical application of the photocatalytic/coagulation integrated process in drinking water plants.

Contents of the invention

Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a method for constructing a photocatalysis/coagulation integrated process, so as to realize the efficient removal of natural organic matter.

Technical solutions

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) Introduce the source water to be treated into the photocatalytic/coagulation integrated reaction tank, add photocatalyst, make it fully mix and stir with the source water to carry out the photocatalytic reaction;

b) After the photocatalytic reaction has been carried out for a period of time, add a coagulant, mix well, reduce the stirring speed to flocculate, and promote the bridging of the coagulant with the help of the characteristics of the easy aggregation of nano photocatalyst particles to form a floc complex. The coagulant is one of polyaluminum chloride, ferric chloride, and polyferric sulfate, and its dosage is the optimal dose when it is used alone to ensure the coagulation effect;

c) After the floc complexes are completely settled, the floc complexes are collected, recycled and regenerated, and the regenerated floc complexes are recycled to the photocatalyst dosing unit.

In the preferred disclosed example of the present invention, the photocatalyst in step a) is a common safe and non-toxic photocatalyst in the field of environmental water treatment, and the amount of addition is generally selected according to the quality of the source water to be treated, preferably bismuth ferrite (BiFeO ₃ ).

In the preferred disclosed example of the present invention, the coagulant in step b) is polyaluminum chloride.

In the preferred disclosed examples of the present invention, the regeneration in step c) is any one of pickling, alkali washing and thermal regeneration.

The photocatalysis/coagulation integration process disclosed in the present invention can promote the bridging effect of the coagulant through the characteristics that the nano photocatalyst particles are easy to agglomerate, that is, the photocatalyst acts as the flocculation nucleus in the initial stage of coagulation, and the The continuously produced floc particles are stacked on the interlayer structure of the photocatalyst and attached to the surface of the photocatalyst, which can significantly increase the specific gravity of the floc, form a floc complex, and achieve rapid settlement after the coagulation stage is completed. . Therefore, the photocatalytic/coagulation integrated process can significantly increase the settling velocity of flocs, thereby speeding up the settling process and reducing the hydraulic retention time and the volume of settling equipment in drinking water treatment.

The features of the present invention are:

(1) Disinfection by-products are a type of secondary pollutants with potential health risks generated during the disinfection of drinking water, and their concentration levels are generally in the range of ng·L ^-1 ~μg·L ^-1 , photocatalytic/coagulation integrated The chemical system can further improve the quality of effluent water, and effectively reduce the generation of disinfection by-products at the level of μg·L ^-1 ;

(2) In the photocatalytic/coagulation integrated system, as the coagulation reaction progresses, the floc particles produced continue to attach to the flocculation nuclei, which can significantly increase the specific gravity of the flocs, making the floc complex Rapid settlement can be achieved after the stage is completed, which can greatly reduce the hydraulic retention time and the volume of the settlement equipment in the drinking water treatment process;

(3) The reaction of the photocatalytic/coagulation integrated system occurs in the same reactor. Compared with the combination process where the reaction occurs in more than two different reactors, no additional structures are required, the operation is simple, and the existing process is easy to modify And easy to promote.

Beneficial effect

The invention discloses a photocatalysis/coagulation integrated water treatment process, combining the characteristics of different processes of photocatalysis and coagulation, using coagulation to make up for the problem of insufficient photocatalysis to remove turbidity, so that it can be carried out in the same reactor , the nano-photocatalyst can be used as the floc particles produced by the flocculation nucleus to increase the specific gravity and density of the flocs, generate floc complexes, and realize rapid sedimentation and efficient removal of NOM. In addition, the photocatalytic/coagulation integrated process is simple to operate, can significantly increase the settling velocity of the flocs, and reduce the volume of the hydraulic retention time settling equipment in the drinking water treatment process, which has guiding significance in the practical application of drinking water plants.

Description of drawings

Figure 1. Scanning electron microscope pictures of the floc complex growing at 5min (a), 7min (b), 9min (c), 11min (d), and 15min (e);

Figure 2. FTIR spectra of floc complexes at different growth times;

Figure 3. XRD patterns of floc complexes at different growth times;

Figure 4. Process flow diagram of the integrated photocatalysis/coagulation system.

detailed description

The present invention will be described in detail below in conjunction with the examples, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following examples.

Unless otherwise defined, terms (including technical and technical terms) used herein should be interpreted as having the same meaning as commonly understood by those skilled in the art to which this invention belongs. It will also be understood that the terms used herein should be interpreted to have a meaning consistent with their meanings in the context of this specification and related art, and should not be interpreted in an idealized or over-the-top form, unless expressly so defined herein .

Example 1

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) The influent water quality of a certain source water was detected as UV ₂₅₄ of 0.180 and turbidity of 14.7NTU;

b) According to the quality of the treated water, add 0.4g/L bismuth ferrite to the photocatalytic/coagulation integrated reaction tank, and use mechanical stirring to stir rapidly at a stirring speed of 200r/min, so that it can be fully mixed with the source water for photocatalysis. Catalytic reaction;

c) After the photocatalytic reaction in the reaction tank is carried out for 3 minutes, add polyaluminum chloride with a content of 20mg/L to the reaction tank, and after the coagulant is fully mixed in the photocatalytic/coagulation integrated reaction tank, reduce the stirring Stir at a slow speed of 40r/min for 12min to carry out the flocculation process;

d) Complete settlement was achieved after 10 minutes of precipitation, and the water quality of the effluent was determined to be 0.025 for UV ₂₅₄ , and the removal rate of UV ₂₅₄ reached 86%; the turbidity was 2.32 NTU, and the turbidity removal rate reached 84%;

e) Collect the floc complex produced in the photocatalytic/coagulation integrated reaction tank, regenerate it by pickling, and reuse it in the photocatalyst dosing unit. After recycling 4 times, the UV ₂₅₄ removal rate still reaches 80% .

Example 2

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) The influent water quality of a certain source water is tested as UV ₂₅₄ is 0.190 and turbidity is 16.3NTU;

b) According to the treated water quality, add 1.6g/L bismuth ferrite to the photocatalytic/coagulation integrated reaction tank, and use mechanical stirring to stir rapidly at a stirring speed of 200r/min, so that it can be fully mixed with the source water for photocatalysis Catalytic reaction;

c) After the photocatalytic reaction in the reaction tank is carried out for 3 minutes, add polyaluminum chloride with a content of 20mg/L to the reaction tank, and after the coagulant is fully mixed in the photocatalytic/coagulation integrated reaction tank, reduce the stirring Stir at a slow speed of 40r/min for 12min to carry out the flocculation process;

d) Complete settlement was achieved after 10 minutes of precipitation, and the water quality of the effluent was determined to be 0.021 for UV ₂₅₄ , and the removal rate of UV ₂₅₄ reached 89%; the turbidity was 2.85 NTU, and the turbidity removal rate reached 83%;

e) Collect the floc complex produced in the photocatalytic/coagulation integrated reaction tank, regenerate it by alkali washing, and reuse it in the photocatalyst dosing unit. After recycling 4 times, the UV ₂₅₄ removal rate still reaches 82% ;

Example 3

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) The influent water quality of a certain source water is tested as UV ₂₅₄ is 0.181 and turbidity is 15.2NTU;

b) According to the quality of the treated water, add 0.4g/L bismuth ferrite to the photocatalytic/coagulation integrated reaction tank, and use mechanical stirring to stir rapidly at a stirring speed of 200r/min, so that it can be fully mixed with the source water for photocatalysis. Catalytic reaction;

c) After the photocatalytic reaction in the reaction tank is carried out for 3 minutes, add polyaluminum chloride with a content of 20mg/L to the reaction tank, and after the coagulant is fully mixed in the photocatalytic/coagulation integrated reaction tank, reduce the stirring Stir at a slow speed of 40r/min for 12min to carry out the flocculation process;

d) Complete settlement was achieved after 10 minutes of precipitation, and the water quality of the effluent was determined to be 0.023 for UV ₂₅₄ , and the removal rate of UV ₂₅₄ reached 87%; the turbidity was 2.70 NTU, and the turbidity removal rate reached 82%;

e) Collect the floc complex produced in the photocatalytic/coagulation integrated reaction tank, use the thermal regeneration method to regenerate, and recycle it to the photocatalyst dosing unit after calcination at 500°C for 2 hours, and the UV ₂₅₄ removal rate after reuse 4 times Still at 78%.

The microscopic structure of BiFeO ₃ is petal-like. As the growth time of the floc complex increases, the floc particles gradually occupy the pores in the interlayer structure of the photocatalyst, and then attach to its surface. After about 8 minutes of growth, a relatively stable and Petal-like BiFeO ₃ cored floc composites. The XRD pattern shows that the absorption peak intensity of the floc particles is weakened when they are attached and stacked on the interlayer or surface of BiFeO ₃ , but the crystal structure is not destroyed. The functional groups of the floc complexes were analyzed by FTIR spectrum. The presence of metal ions in the photocatalyst chelated with some -OH or -COOH in the organic matter and adsorbed on the corresponding chemical bonds. At the same time, the Al ³⁺ in the coagulant The interaction with organic matter produces floc particles, which are attached and stacked on the interlayer structure and surface of BiFeO ₃ .

Example 4

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) The influent water quality of a certain source water was detected as UV254 of 0.472 and turbidity of 56.4NTU;

b) According to the treated water quality, add 0.4g/L Fe-doped MoS ₂ /Bi ₂ WO ₆ to the photocatalytic/coagulation integrated reaction tank, and use mechanical stirring to stir rapidly at a stirring speed of 200r/min to make it with The source water is fully mixed and stirred for photocatalytic reaction;

c) After the photocatalytic reaction in the reaction tank was carried out for 5 minutes, polyaluminum chloride with a content of 20 mg/L was added to the reaction tank, and the coagulant was fully mixed in the photocatalytic/coagulation integrated reaction tank, and the agitation was reduced. Stir at a slow speed of 40r/min for 12min to carry out the flocculation process;

d) Complete settlement was achieved after 10 minutes of precipitation, and the quality of the effluent water was determined to be 0.009 for UV254, and the UV254 removal rate reached 98%; the turbidity was 10.70 NTU, and the turbidity removal rate reached 81%.

Example 5

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) The influent water quality of a certain source water was detected as UV254 of 0.472 and turbidity of 56.4NTU;

b) According to the quality of the treated water, add 0.4g/L Fe@TiO ₂ to the photocatalytic/coagulation integrated reaction tank, and use mechanical stirring to stir rapidly at a stirring speed of 200r/min to fully mix and stir with the source water. photocatalytic reaction;

c) After the photocatalytic reaction in the reaction tank was carried out for 5 minutes, polyaluminum chloride with a content of 20 mg/L was added to the reaction tank, and the coagulant was fully mixed in the photocatalytic/coagulation integrated reaction tank, and the agitation was reduced. Stir at a slow speed of 40r/min for 12min to carry out the flocculation process;

d) After settling for 10 minutes, complete settlement was achieved. The water quality of the effluent was determined to be 0.008 for UV254, and the UV254 removal rate reached 98%; the turbidity was 12.90 NTU, and the turbidity removal rate reached 77%.

Example 6

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) The influent water quality of a certain source water was detected as UV254 of 0.229 and turbidity of 28.3NTU;

b) According to the treated water quality, add 0.4g/L Fe-doped MoS ₂ /Bi ₂ WO ₆ to the photocatalytic/coagulation integrated reaction tank, and use mechanical stirring to stir rapidly at a stirring speed of 200r/min to make it with The source water is fully mixed and stirred for photocatalytic reaction;

c) After the photocatalytic reaction in the reaction tank was carried out for 5 minutes, polyaluminum chloride with a content of 20 mg/L was added to the reaction tank, and the coagulant was fully mixed in the photocatalytic/coagulation integrated reaction tank, and the agitation was reduced. Stir at a slow speed of 40r/min for 12min to carry out the flocculation process;

d) After settling for 10 minutes, complete settlement was achieved. The water quality of the effluent was determined to be 0.007 for UV254, and the UV254 removal rate reached 97%; the turbidity was 5.20 NTU, and the turbidity removal rate reached 82%.

Example 7

A photocatalytic/coagulation integrated water treatment process, comprising the following steps:

a) The influent water quality of a certain source water was detected as UV254 of 0.229 and turbidity of 28.3NTU;

b) According to the quality of the treated water, add 0.4g/L Fe@TiO ₂ to the photocatalytic/coagulation integrated reaction tank, and use mechanical stirring to stir rapidly at a stirring speed of 200r/min to fully mix and stir with the source water. photocatalytic reaction;

c) After the photocatalytic reaction in the reaction tank was carried out for 5 minutes, polyaluminum chloride with a content of 20 mg/L was added to the reaction tank, and the coagulant was fully mixed in the photocatalytic/coagulation integrated reaction tank, and the agitation was reduced. Stir at a slow speed of 40r/min for 12min to carry out the flocculation process;

d) After settling for 10 minutes, complete settlement was achieved, and the quality of the effluent was determined to be 0.006 for UV254, and the UV254 removal rate reached 97%; the turbidity was 5.60 NTU, and the turbidity removal rate reached 80%.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by the description of the present invention, or directly or indirectly used in other related technical fields, shall be the same as The theory is included in the patent protection scope of the present invention.

Claims (5)

1. A photocatalytic/coagulation integrated water treatment process, is characterized in that, comprises the steps: a) The source water to be treated is introduced into the photocatalytic/coagulation integrated reaction tank, and the photocatalyst is added to fully mix and stir with the source water to carry out the photocatalytic reaction; b) After the photocatalytic reaction has been carried out for a period of time, add a coagulant, mix well, reduce the stirring speed to flocculate, and promote the bridging of the coagulant with the help of the characteristics of the easy aggregation of nano photocatalyst particles to form a floc complex. Described coagulant is any one in polyaluminum chloride, ferric chloride, polyferric sulfate; c) After the floc complexes are completely settled, collect the floc complexes, recycle and regenerate them, and reuse the regenerated floc complexes to the photocatalyst dosing unit. 2. The photocatalytic/coagulation integrated water treatment process according to claim 1, characterized in that: the photocatalyst in step a) is a common safe and non-toxic photocatalyst in the field of environmental water treatment, and the amount added depends on the Routine selection of source water quality. 3. The photocatalytic/coagulation integrated water treatment process according to claim 1, characterized in that the photocatalyst in step a) is bismuth ferrite. 4. The photocatalytic/coagulation integrated water treatment process according to claim 1, characterized in that: the coagulant in step b) is polyaluminum chloride. 5. The photocatalytic/coagulation integrated water treatment process according to claim 1, characterized in that: the regeneration in step c) is any one of pickling, alkali washing and thermal regeneration.

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