CN115028233B - Method for degrading microcystin in water - Google Patents

Abstract

The invention discloses a method for degrading microcystins in water, which specifically comprises using a 222nm excimer ultraviolet lamp to irradiate water samples to be treated to degrade the microcystins in the water samples to be treated. The invention adopts 222 nm excimer ultraviolet light to photolyze the microcystins in water, which has high degradation efficiency and higher photolysis rate; at the same time, the excimer ultraviolet lamp has a smaller size and saves land occupation; Mercury light source will not cause secondary pollution to the environment. The method adopted in the present invention does not require the input of oxidants, does not require additional protective measures while reducing costs, avoids the risk of environmental pollution, can be upgraded and reconstructed through the existing disinfection unit, has strong compatibility with the existing water treatment process, and can Water disinfection can be performed while degrading algal toxins, which is suitable for large-scale industrial application.

Description

A method for degrading microcystin in water

technical field

The invention relates to the field of water supply treatment, in particular to a method for degrading microcystins in water.

Background technique

In summer and autumn when the temperature is suitable, blue-green algae will grow in large numbers in nutrient-rich freshwater water bodies, becoming the dominant population in the water body, plundering nutrients and oxygen, and threatening the survival and reproduction of other aquatic organisms. This phenomenon is called algae bloom. Freshwater blooms are mainly caused by cyanobacteria, which produce secondary metabolites - cyanotoxins, which can endanger aquatic organisms and human health. Among them, microcystins are the most common and most toxic algal toxins. As a class of pollutants that have attracted much attention, the water treatment control technology of microcystins has also become a research hotspot in the field of environment in recent years. At present, traditional physical, chemical, biological and other water treatment methods have limitations in varying degrees in removing algae toxins from water. Therefore, it is particularly critical to develop new green and efficient water treatment technologies to deal with this problem.

Ultraviolet light is generally considered as an environmentally friendly water treatment technology. Because ultraviolet light has the advantages of high sterilization efficiency, easy operation and high safety, ultraviolet light irradiation technology has many application tests in the field of water treatment, and has been used in water supply It is used in the disinfection process of the treatment plant. Ultraviolet light technology can also be divided into ultraviolet photocatalysis and ultraviolet photodegradation. With the continuous development and promotion of ultraviolet equipment and technology, these two branches have also received more and more attention in recent years. However, the former has problems such as catalyst deactivation and high price. In comparison, ultraviolet photodegradation has better practical application space and development prospects. The removal mechanism of organic matter by ultraviolet light mainly includes direct photolysis and free radical oxidation. As for the ultraviolet light source used in water treatment, low-pressure ultraviolet (Low pressure UV, LPUV) lamps are mainly used commercially at present, and low-pressure ultraviolet lamps mainly emit monochromatic light at 254 nm. However, the low-pressure ultraviolet lamp contains mercury, which will cause secondary pollution to the environment. At the same time, its size is large and it needs to occupy a larger site; in order to increase its degradation effect, it is often necessary to add oxidants such as peracetic acid to assist, but these Oxidants are dangerous, and additional protective measures are required during storage and transportation, which also increases the cost of the process. At the same time, these oxidants have the risk of deteriorating the growth of biofilm in the water supply network and endangering the safety of water supply.

Contents of the invention

Therefore, the technical problem to be solved by the present invention is that the existing low-pressure ultraviolet lamps have poor degradation effect on microcystins and are prone to pollution, so as to provide a method for degrading microcystins in water.

For this reason, the present invention adopts following technical scheme:

The invention provides a method for degrading microcystins in water. A 222nm excimer ultraviolet lamp is used to irradiate the water samples to be treated to degrade the microcystins in the water samples to be treated.

Further, the irradiation dose of the excimer ultraviolet lamp is 200 mJ/cm ² -500 mJ/cm ² .

The average light intensity of the excimer ultraviolet lamp is ≥0.13 mW/cm ² , and the temperature of the irradiation can be room temperature.

Adjust the pH of the water sample to be treated to 5-9 before irradiation, preferably with sulfuric acid or sodium hydroxide.

Further, the microcystin is microcystin-LR.

The technical solution of the present invention has the following advantages:

(1) The present invention uses 222 nm excimer ultraviolet light to photolyze microcystins in water. Microcystins absorb ultraviolet energy and break down. Accompanied by the generation of free radicals, algal toxin molecules are directly photolyzed and indirectly freed by ultraviolet rays. degraded by attack. Its degradation efficiency is high, and its treatment mechanism is different from the principle that low-pressure ultraviolet rays mainly target DNA, and it has a significant effect on the treatment of microcystins; on the other hand, it has an absorption peak near 222 nm for MC-LR, and its absorption coefficient is significantly higher than that of low-pressure ultraviolet rays. The wavelength of the ultraviolet light has a higher photolysis rate when 222 nm excimer ultraviolet light is irradiated.

(2) The present invention is aimed at water samples to be treated with different pH, and can be processed by adjusting the pH, which has a wide range of applications.

(3) The present invention uses 222 nm excimer ultraviolet light, and the excimer ultraviolet lamp has a smaller size, which saves land occupation; the excimer lamp is a mercury-free light source and will not cause secondary pollution to the environment.

(4) The present invention does not require the input of an oxidant, reduces the cost and does not require additional protective measures, and avoids the risk of environmental pollution.

(5) The excimer ultraviolet technology used in the present invention has a promising application in the field of municipal water disinfection in my country. It can be upgraded through existing disinfection units, and it has a strong ability to fit with existing water treatment processes and is suitable for large-scale industrial applications.

(6) Excimer ultraviolet rays can also degrade algae toxins while disinfecting water. Therefore, the technology of the present invention has broad engineering application prospects.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

Fig. 1 is the effect diagram of degrading microcystin-LR in test example 1 of the present invention;

Fig. 2 is an effect diagram of microcystin-LR degradation in Test Example 2 of the present invention.

Detailed ways

The following examples are provided in order to further understand the present invention better, are not limited to the best implementation mode, and do not limit the content and protection scope of the present invention, anyone under the inspiration of the present invention or use the present invention Any product identical or similar to the present invention obtained by combining features of other prior art falls within the protection scope of the present invention.

If no specific experimental steps or conditions are indicated in the examples, it can be carried out according to the operation or conditions of the conventional experimental steps described in the literature in this field.

The 222 nm excimer ultraviolet lamp is placed in the designed multi-adaptive integrated ultraviolet parallel static experimental device, that is, the lamp tube is placed in a stainless steel box and fixed, and there are multiple steel plates that can be inserted to facilitate the change of the position of the steel plate To simulate different process operating conditions. Open the ventilation and cooling system and close the box door during the ultraviolet operation, and close the orifice plate to end the irradiation at the end of the operation. After testing, the petri coefficient of the lamp in the device can reach more than 0.9 to ensure the concentration and scientificity of ultraviolet irradiation. sex.

Example 1

This example provides a method for degrading microcystins. The concentration of microcystin-LR in the water sample to be treated is 100 μg/L, and the pH is 10. The specific method is as follows:

At room temperature, take 20 mL of the water sample to be treated, adjust the pH of the water sample to pH = 7 with sulfuric acid, turn on the 222 nm excimer ultraviolet lamp and wait for it to stabilize, pour the above water sample into 20 mL of ultraviolet photochemical reaction In the instrument, set the irradiation dose of 222 nm excimer ultraviolet light to 500 mJ/cm ² . Among them, the ultraviolet dose is the product of the average ultraviolet light intensity and time. Therefore, according to the measured average UV light intensity of 0.132 mW/cm ² and the set UV dose of 500 mJ/cm ² , the reaction time can be calculated to be 71 min 4 s. After the reaction, the content of microcystin-LR in the treated water was determined to be below the detection limit (0.1 μg/L), and the degradation rate of microcystin-LR exceeded 99.9%.

Example 2

This example provides a method for degrading microcystins. The concentration of microcystin-LR in the water sample to be treated is 100 μg/L, and the pH is 4. The specific method is as follows:

At room temperature, take 20 mL of the water sample to be treated, adjust the pH of the water sample to pH=6 with sodium hydroxide, turn on the 222 nm excimer ultraviolet lamp, and pour the above water sample to be treated into a 20 mL ultraviolet photochemical reactor , set the irradiation dose of 222 nm excimer ultraviolet light to 300 mJ/cm ² , according to the measured average ultraviolet light intensity of 0.132 mW/cm ² and the set ultraviolet dose of 300 mJ/cm ² , the reaction time can be calculated as 42 Minutes and 38 seconds. After the reaction, the content of Microcystin-LR in the treated water was determined to be 1.8 μg/L, and the degradation rate of Microcystin-LR exceeded 98%.

Test example 1

This test example compares the degradation rate of microcystins in water under the irradiation of low-pressure ultraviolet rays, LED lamp ultraviolet rays and 222 nm excimer ultraviolet rays. The wavelength of low-pressure ultraviolet rays alone is 254nm, and the wavelength of LED lamp ultraviolet rays is 285nm.

The specific method is as follows:

(1) At room temperature, prepare 100 μg/L MC-LR solution, stir well, and adjust the initial pH of the solution to 7.

(2) After turning on the 222 nm excimer ultraviolet lamp and waiting for it to stabilize, pour the water sample to be treated into a 20 mL ultraviolet photochemical reactor. The dose of ultraviolet radiation is 0 mJ/cm ² ~ 500 mJ/cm ² The reaction time was calculated from the ultraviolet dose, and 1 mL of water sample was taken according to the set reaction time and added to the sample bottle of liquid chromatography, and the same method was used to conduct experiments with low-pressure ultraviolet lamps and LED lamp ultraviolet rays.

(3) The concentration of MC-LR in water samples before and after treatment was determined by liquid chromatography-mass spectrometry.

The degradation effects of low-pressure ultraviolet rays, LED lamp ultraviolet rays, and 222 nm excimer ultraviolet rays on MC-LR in water are shown in Table 1, and the degradation effect changes with ultraviolet doses are shown in Figure 1.

Table 1 Degradation effect of different ultraviolet rays on MC-LR in water

UV dose (mJ/cm2) Low pressure UV photodegradation (%) UV degradation of LED lamps (%) Excimer UV degradation (%) 0 0 0 0 100 37 0 65 200 47 6.1 90 300 54 5.1 97 500 61 8.2 99.9

It can be seen from Table 1 and Figure 1 that the ultraviolet degradation effect of LED lamps is extremely poor, and the degradation effect of low-voltage ultraviolet light on MC-LR is not strong. Relatively, 222 nm excimer ultraviolet light significantly improves the degradation effect, and at 500 mJ/cm ² Under the UV dose, the removal rate of MC-LR can reach 99.9%. This test example proves that the 222 nm excimer ultraviolet light used in the present invention has significantly better degradation effect on MC-LR than conventional ultraviolet light.

Test example 2

This test example compares the degradation effect of microcystin in water by 222 nm excimer ultraviolet irradiation alone and 222 nm ultraviolet activated peracetic acid method.

The specific method is as follows:

The test was carried out according to the test procedure of Test Example 1, in which the concentration of MC-LR in the water sample to be treated was 100 μg/L, the concentration of peracetic acid added was 10 mg/L, and the dose of ultraviolet radiation was 0 mJ/cm ² ~ 500 mJ/cm ² , the test was carried out under the condition that the initial pH of the water sample was adjusted to 7. The effect of adding peracetic acid on the degradation effect of MC-LR in water is shown in Table 2, and the degradation effect with the UV dose is shown in Figure 2, where UV alone represents excimer ultraviolet rays, and UV/PAA represents excimer ultraviolet rays Activate peracetic acid.

Whether or not to add peracetic acid in table 2 affects the degradation effect of MC-LR in water

Radiation dose (mJ/cm2) UV degradation rate of 222 nm excimer alone (%) 222 nm excimer UV/peracetic acid degradation rate (%) 0 0 0 100 65 76 200 90 92 300 97 97 500 99.9 99.9

As can be seen from the above table and Figure 2, the experimental results show that the 222 nm excimer ultraviolet degradation alone can achieve a removal rate of more than 90% at a radiation meter of 200 mJ/cm ² , while the enhanced process of 222 nm ultraviolet combined with other oxidants The effect is not improved much. This test example proves that the effect of the direct photolysis provided by the present invention by utilizing the 222 nm excimer ultraviolet lamp is not inferior to the effect of the ultraviolet-based advanced oxidation process.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (1)

1. A method for degrading microcystins in water, characterized in that, use 220nm excimer ultraviolet light to irradiate the water samples to be treated, and degrade the microcystins in the water samples to be treated; The irradiation dose of the excimer ultraviolet lamp is 200 mJ/cm ² ~500 mJ/cm ² ; The average light intensity of the excimer ultraviolet lamp is ≥0.13 mW/cm ² ; Adjust the pH of the water sample to be treated to 5-9 before irradiation; The microcystin is microcystin-LR; The method does not require the input of an oxidizing agent.

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