Treatment method for removing organic pollutants in water

Abstract

The invention relates to a treatment method for removing organic pollutants in water, which comprises the following steps: introducing ozone into to-be-treated water containing the organic pollutants to enable the initial concentration of the ozone in the to-be-treated water to be 250-550mu M, adding alkali and cyanurate chloride to enable the pH value of the to-be-treated water to be kept at 6-9, and stirring to react until water treatment is finished, wherein the molar ratio of the ozone to the cyanurate chloride in the water to be treated is 1: (0.2-1). According to the method, the pH value of a water system to be treated is adjusted by adding alkali, and the specific adding proportion of ozone and cyanurate chloride is matched, so that ionization of cyanurate chloride, enhancement of ozone decomposition inducing capability and generation of more hydroxyl radicals and active chlorine are facilitated, the utilization rate of ozone is increased, and the degradation effect of 2, 4-D is improved. And the degradation rate of 2, 4-D can reach 90% or above, the cost is low, and the process is simple.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and specifically relates to a method for removing organic pollutants from water. Background Technology

[0002] With the rapid development of modern agriculture, a large amount of agricultural wastewater has been generated. Agricultural wastewater is characterized by its complex composition, high concentration of organic matter, and high salt content, making it difficult to biodegrade. Improving the treatment efficiency of agricultural wastewater is a pressing issue for the water treatment industry. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a phenoxycarboxylic acid herbicide that effectively controls broadleaf weeds in various environments, including crops, lawns, and forests. Its low cost makes it a commonly used herbicide and a common organic pollutant in agricultural wastewater. 2,4-D contains a benzene ring structure, and its degradation under natural conditions is very slow. Currently, advanced oxidation technologies are widely used both domestically and internationally to achieve its degradation.

[0003] Ozone is a strong oxidant frequently used to oxidize and degrade wastewater, and its application in actual wastewater treatment is widespread and technologically mature. Ozone oxidation degrades organic pollutants primarily through the direct oxidation of pollutants by ozone molecules, or through the decomposition of ozone to generate hydroxyl radicals (·OH). These hydroxyl radicals (·OH) directly mineralize pollutants in wastewater into inorganic substances or convert them into low-toxicity, easily biodegradable intermediates. This technology boasts advantages such as rapid oxidation and high degradation efficiency. However, ozone oxidation exhibits selectivity, and due to its low solubility and inherent instability, its utilization rate is not high. Furthermore, ozone generation consumes a significant amount of energy, resulting in relatively high costs for ozone disinfection. In recent years, various catalytic ozonation or ozone coupling technologies have been continuously innovating. The direction of ozone technology development is to generate more and more efficient hydroxyl radicals under the catalysis of catalysts or through coupling with other technologies, while reducing the loss of hydroxyl radicals during the reaction process.

[0004] The literature "Deep Ozone Oxidation Method for Treating 2,4-Dichlorophenoxyacetic Acid Pesticide Wastewater" discloses methods for degrading 2,4-D using ozone / UV irradiation, ozone / hydrogen peroxide, and ozone / hydrogen peroxide / UV light. Among these, the ozone / UV irradiation and ozone / hydrogen peroxide / UV light methods significantly improve the degradation and mineralization rates of 2,4-D compared to ozone degradation alone. However, hydrogen peroxide itself is poorly ionized, resulting in weak ozone-inducing decomposition ability. Furthermore, it consumes a large amount of hydroxyl radicals, leaving significant residues, and its transportation and storage are difficult, limiting the application of ozone / hydrogen peroxide / UV light degradation. Ozone / UV light technology has certain requirements for UV light intensity; insufficient intensity will affect its oxidation effect. In addition, UV oxidation processes require a large amount of energy when treating large volumes of wastewater, resulting in high operating costs and hindering its production application. Summary of the Invention

[0005] The primary objective of this invention is to overcome the shortcomings and deficiencies of existing technologies for treating organic pollutants in water, such as low ozone utilization, unsatisfactory degradation effects, and high process costs, and to provide a method for removing organic pollutants from water.

[0006] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] A method for removing organic pollutants from water, the method comprising the following steps:

[0008] Ozone is introduced into the water to be treated containing organic pollutants to make the initial concentration of ozone in the water 250-550 μM. Alkali and cyanuric chloride are added to maintain the pH of the water to be treated at 6-9. The reaction is stirred until the water treatment is completed.

[0009] The molar ratio of ozone to cyanurate chloride in the water to be treated is 1:0.2 to 1.

[0010] This invention adjusts the pH of the water system by adding alkali, maintaining it between 6 and 9. This facilitates the ionization of cyanuric chloride, enhances ozone decomposition, and generates more hydroxyl radicals and active chlorine (HClO, ClO). - This increases the utilization rate of ozone, thereby enhancing the degradation effect of 2,4-D.

[0011] This invention selects cyanuric chloride as an auxiliary agent to improve the yield of hydroxyl radicals in ozone production. Cyanuric chloride is a compound with a good balance between hypochlorite and chloramine. When injected into water, it can rapidly hydrolyze and release a large amount of free active chlorine (HClO, ClO). - Furthermore, it has low reactivity with free radicals, thus exhibiting a weaker scavenging effect on free radicals. This can increase the steady-state concentration of ·OH in the ozone water treatment system, thereby better enhancing the degradation effect of organic pollutants. In addition, this invention uses cyanuric chloride coupled with ozone to treat wastewater, which is less costly than using chlorine, hypochlorite, and chloramine, and has practical application value.

[0012] Preferably, the organic pollutant in the water to be treated is 2,4-dichlorophenoxyacetic acid.

[0013] Preferably, the concentration of 2,4-dichlorophenoxyacetic acid in the water to be treated is 180–220 ppm; the pH value of the water to be treated containing 180–220 ppm of 2,4-dichlorophenoxyacetic acid is approximately 3–5.

[0014] Preferably, the alkali is at least one of potassium hydroxide and sodium hydroxide.

[0015] Preferably, the pH value of the water to be treated is 6 to 8.

[0016] Preferably, the chlorocyanurate is at least one of dichloroisocyanurate or trichloroisocyanurate.

[0017] More preferably, the chlorocyanurate is a mixture of dichloroisocyanurate and trichloroisocyanurate, wherein the dichloroisocyanurate is at least one of sodium dichloroisocyanurate and potassium dichloroisocyanurate, and the trichloroisocyanurate is at least one of sodium trichloroisocyanurate and potassium trichloroisocyanurate.

[0018] More preferably, the chlorocyanurate is a mixture obtained by compounding dichloroisocyanurate and trichloroisocyanurate in a molar ratio of 1:1.

[0019] The method of adding cyanuric chloride in this invention can be either direct addition in the form of solid cyanuric chloride or addition in the form of cyanuric chloride solution.

[0020] Preferably, the cyanuric chloride solution is added in this invention.

[0021] Preferably, the concentration of the alkali is 1.5 to 3 mM.

[0022] More preferably, the initial concentration of ozone is 350–550 μM.

[0023] Preferably, the reaction time is 5 to 60 minutes.

[0024] More preferably, the reaction time is 20 to 40 minutes.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] The water treatment method of this invention combines ozone and cyanuric chloride technology. By adding alkali to adjust the pH of the water system to be treated, maintaining the pH between 6 and 9, and with a specific dosage ratio of ozone to cyanuric chloride, it facilitates the ionization of cyanuric chloride, inducing enhanced ozone decomposition and generating more hydroxyl radicals and active chlorine (HClO, ClO). - This increases the utilization rate of ozone, thereby improving the degradation effect of 2,4-D. The water treatment method of the present invention can achieve a degradation rate of over 90% for 2,4-D.

[0027] This invention selects cyanuric chloride as an auxiliary agent to improve the yield of hydroxyl radicals in ozone production. Cyanuric chloride is low in cost, and by adding cyanuric chloride, a 2,4-D degradation effect similar to that of high ozone input can be achieved while reducing the amount of ozone input, thus saving water treatment costs. At the same time, the water treatment method of combining ozone and cyanuric chloride in this invention is simple and has broad application prospects. Detailed Implementation

[0028] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0029] Example 1

[0030] This embodiment provides a method for removing organic pollutants from water, including the following steps: After generating ozone using an ozone generator, ozone is introduced into an ozone contact reactor containing water to be treated with 200 ppm 2,4-D, so that the initial ozone concentration in the water to be treated is 300 μM. Then, 2.3 mM sodium hydroxide and 60 μM cyanurate chloride are added sequentially under stirring to make the pH of the water system to be treated about 6 to 8. Then, the stirring is maintained and the residence time of the water to be treated in the ozone contact reactor is controlled to be 30 min to complete the water treatment process.

[0031] The water to be treated mainly contains 2,4-D, and also contains trace amounts of other organic pollutants;

[0032] The chlorocyanurate is a mixture obtained by compounding dichloroisocyanurate and trichloroisocyanurate in a molar ratio of 1:1.

[0033] Example 2

[0034] This embodiment provides a treatment method for removing organic pollutants from water. The treatment steps are basically the same as those in Example 1, except that the amount of cyanuric chloride added is 150 μM and the molar ratio of ozone to cyanuric chloride is 1:0.5.

[0035] Example 3

[0036] This embodiment provides a treatment method for removing organic pollutants from water. The treatment steps are basically the same as those in Embodiment 1, except that the amount of cyanuric chloride added is 300 μM and the molar ratio of ozone to cyanuric chloride is 1:1.

[0037] Example 4

[0038] This embodiment provides a method for removing organic pollutants from water, including the following steps: After generating ozone using an ozone generator, ozone is introduced into an ozone contact reactor containing water to be treated with 200 ppm 2,4-D, so that the initial ozone concentration in the water to be treated is 400 μM. Then, 2.3 mM sodium hydroxide and 80 μM cyanurate chloride are added sequentially under stirring to make the pH of the water system to be treated about 6 to 8. Then, the stirring is maintained and the residence time of the water to be treated in the ozone contact reactor is controlled to be 30 min to complete the water treatment process.

[0039] The water to be treated mainly contains 2,4-D, and also contains trace amounts of other organic pollutants;

[0040] The chlorocyanurate is a mixture obtained by compounding dichloroisocyanurate and trichloroisocyanurate in a molar ratio of 1:1.

[0041] Example 5

[0042] This embodiment provides a treatment method for removing organic pollutants from water. The treatment steps are basically the same as those in Embodiment 4, except that the amount of cyanuric chloride added is 200 μM and the molar ratio of ozone to cyanuric chloride is 1:0.5.

[0043] Example 6

[0044] This embodiment provides a treatment method for removing organic pollutants from water. The treatment steps are basically the same as those in Example 4, except that the amount of cyanuric chloride added is 400 μM and the molar ratio of ozone to cyanuric chloride is 1:1.

[0045] Example 7

[0046] This embodiment provides a method for removing organic pollutants from water, including the following steps: After generating ozone using an ozone generator, ozone is introduced into an ozone contact reactor containing water to be treated with 200 ppm 2,4-D, so that the initial ozone concentration in the water to be treated is 500 μM. Then, 2.3 mM sodium hydroxide and 100 μM cyanurate chloride are added sequentially under stirring to make the pH of the water system to be treated about 6 to 8. Then, the stirring is maintained and the residence time of the water to be treated in the ozone contact reactor is controlled to be 30 min to complete the water treatment process.

[0047] The water to be treated mainly contains 2,4-D, and also contains trace amounts of other organic pollutants;

[0048] The chlorocyanurate is a mixture obtained by compounding dichloroisocyanurate and trichloroisocyanurate in a molar ratio of 1:1.

[0049] Example 8

[0050] This embodiment provides a treatment method for removing organic pollutants from water. The treatment steps are basically the same as those in Embodiment 7, except that the amount of cyanuric chloride added is 250 μM and the molar ratio of ozone to cyanuric chloride is 1:0.5.

[0051] Example 9

[0052] This embodiment provides a treatment method for removing organic pollutants from water. The treatment steps are basically the same as those in Embodiment 7, except that the amount of cyanuric chloride added is 500 μM and the molar ratio of ozone to cyanuric chloride is 1:1.

[0053] Comparative Example 1

[0054] This comparative example provides a method for ozone treatment of water, comprising the following steps: after preparing ozone using an ozone generator, ozone is introduced into an ozone contact reactor containing water to be treated containing 200 ppm 2,4-D, so that the initial ozone concentration in the water to be treated is 300 μM. 2.3 mM sodium hydroxide is added sequentially under stirring to make the pH of the water system to be treated about 6 to 8. Then, the stirring is maintained and the residence time of the water to be treated in the ozone contact reactor is controlled to be 30 min to complete the water treatment process.

[0055] The water to be treated mainly contains 2,4-D, and also contains trace amounts of other organic pollutants.

[0056] Comparative Example 2

[0057] This comparative example provides a method for treating water with ozone. The treatment steps are basically the same as those in Comparative Example 1, except that the initial concentration of ozone in the water to be treated is 400 μM.

[0058] Comparative Example 3

[0059] This comparative example provides a method for treating water with ozone. The treatment steps are basically the same as those in Comparative Example 1, except that the initial concentration of ozone in the water to be treated is 500 μM.

[0060] Comparative Example 4

[0061] This comparative example provides a method for treating water with cyanuric chloride, comprising the following steps:

[0062] Under stirring, 2.3 mM sodium hydroxide and 100 μM cyanurate chloride were added sequentially to the water to be treated containing 200 ppm 2,4-D to make the pH of the water system about 6 to 8. Then, the stirring was maintained for 30 minutes to complete the water treatment process.

[0063] The water to be treated mainly contains 2,4-D, and also contains trace amounts of other organic pollutants;

[0064] The chlorocyanurate is a mixture obtained by compounding dichloroisocyanurate and trichloroisocyanurate in a molar ratio of 1:1.

[0065] Comparative Example 5

[0066] This comparative example provides a method for treating water with cyanuric chloride, and the treatment steps are basically the same as those in Comparative Example 4, except that the amount of cyanuric chloride added is 200 μM.

[0067] Comparative Example 6

[0068] This comparative example provides a method for treating water with cyanuric chloride, and the treatment steps are basically the same as those in Comparative Example 4, except that the amount of cyanuric chloride added is 300 μM.

[0069] Comparative Example 7

[0070] This comparative example provides a method for treating water with cyanuric chloride, and the treatment steps are basically the same as those in Comparative Example 4, except that the amount of cyanuric chloride added is 400 μM.

[0071] Comparative Example 8

[0072] This comparative example provides a method for treating water with cyanuric chloride, and the treatment steps are basically the same as those in Comparative Example 4, except that the amount of cyanuric chloride added is 500 μM.

[0073] Comparative Example 9

[0074] This comparative example provides a method for removing organic pollutants from water. The treatment steps are basically the same as those in Example 1, except that the amount of cyanuric chloride added is 1500 μM and the molar ratio of ozone to cyanuric chloride is 1:5.

[0075] Comparative Example 10

[0076] This comparative example provides a method for removing organic pollutants from water. The treatment steps are basically the same as those in Example 4, except that the amount of cyanuric chloride added is 2000 μM and the molar ratio of ozone to cyanuric chloride is 1:5.

[0077] Comparative Example 11

[0078] This comparative example provides a method for removing organic pollutants from water. The treatment steps are basically the same as those in Example 7, except that the amount of cyanuric chloride added is 2500 μM and the molar ratio of ozone to cyanuric chloride is 1:5.

[0079] The 2,4-D degradation rate of the water treated in Examples 1-9 and Comparative Examples 1-11 was tested, and the test results are shown in Table 1.

[0080] Table 1. Test results of 2,4-D degradation rate of Examples 1-9 and Comparative Examples 1-11

[0081]

[0082]

[0083] Table 2. Test results of 2,4-D degradation rate of water treated with different molar ratios of ozone and cyanurate chloride in the examples and comparative examples.

[0084]

[0085] As can be seen from the data in Tables 1 and 2, cyanuric chloride itself has a poor degradation effect on 2,4-D. The water treatment method of the present invention can achieve a better 2,4-D degradation effect than ozone oxidation alone under a specific ozone to cyanuric chloride molar ratio, and the degradation rate of 2,4-D can reach more than 90%.

[0086] As shown in Table 2, under the same ozone input, the addition of low concentration of cyanuric chloride can significantly improve the degradation effect of 2,4-D. Within a certain range, the more cyanuric chloride is added, the better the degradation rate of 2,4-D is improved. However, when the amount of cyanuric chloride added is too high, it will be detrimental to the degradation of 2,4-D.

[0087] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A treatment method for removing organic contaminants from water, characterized by, The method comprises the following steps: ozone is introduced into the water containing organic pollutants to be treated, so that the initial concentration of ozone in the water to be treated is 250-550 μM, alkali and chlorinated cyanurate are added, the pH of the water to be treated is kept at 6-9, and the reaction is stirred until the water treatment is completed; wherein the molar ratio of ozone to chlorinated cyanurate in the water to be treated is 1:0.2-1.

2. The process of claim 1 wherein, The organic pollutants in the water to be treated are 2,4-dichlorophenoxyacetic acid.

3. The process of claim 2 wherein, The concentration of 2,4-dichlorophenoxyacetic acid in the water to be treated is 180-220 ppm.

4. The method of claim 1 wherein, The alkali is at least one of potassium hydroxide and sodium hydroxide.

5. The method of claim 1 wherein, The concentration of the alkali is 1.5-3 mM.

6. The process of claim 1 wherein, The chlorinated cyanurate is at least one of dichloroisocyanurate and trichloroisocyanurate.

7. The method of claim 1 wherein, The chlorinated cyanurate is a mixture of dichloroisocyanurate and trichloroisocyanurate.

8. The method of claim 1 wherein, The initial concentration of ozone is 350-550 μM.

9. The method of claim 1 wherein, The reaction time is 5-60 min.

10. The method of claim 1 wherein, The reaction time is 20-40 min.

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