Water treatment method based on non-free radical oxidation

Abstract

The invention relates to the technical field of sewage treatment, in particular to a water treatment method based on non-free radical oxidation. The water treatment method comprises the following steps: adding soluble carbonate into sewage containing calcium ions to obtain calcium carbonate crystals, and then introducing ozone to oxidize the sewage to obtain purified water. According to the water treatment method provided by the invention, calcium carbonate can be generated in situ in the sewage, ozone is catalyzed by the calcium carbonate to be decomposed on the surface of the sewage to generate high-activity atomic oxygen, and efficient oxidative degradation of pollutants is realized through a direct electron transfer mechanism between the atomic oxygen and organic pollutant molecules. The method breaks through the limitation of a traditional free radical path, avoids the problem of hydroxyl free radical quenching, has the advantages of high catalytic efficiency, good stability, environmental friendliness and no need of additional addition of a catalyst carrier, can realize efficient removal of calcium ions in sewage, and can be widely applied to water treatment and deep treatment of refractory organic wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a water treatment method based on non-radical oxidation. Background Technology

[0002] Ozone, with its high oxidation potential (2.07 V), is widely considered an effective means of treating electron-rich organic pollutants. However, the direct oxidation of ozone molecules (O3) suffers from selectivity limitations and low removal efficiency. Therefore, catalytic ozone oxidation technology, which promotes the decomposition of ozone to generate reactive oxygen species (ROS) to enhance the degradation of organic pollutants, has become an important research direction.

[0003] During the catalytic process, the catalyst significantly enhances the degradation efficiency of ozone-resistant pollutants by driving the conversion of O3 into reactive oxygen species (including free radicals and non-free radicals). The free radical pathway mainly relies on hydroxyl radicals (•OH) and superoxide radicals (•O2). - However, it is susceptible to common impurities in water (such as Cl). - HCO3 - H2PO4 - The quenching of singlet oxygen severely limits its application in complex real-world water bodies. Therefore, based on singlet oxygen (… 1 The non-radical pathways of O2 and surface reactive oxygen species (*O) have received considerable attention in recent years. Similar to O3, 1 O2 tends to selectively oxidize electron-rich organic matter, and its contribution to the overall removal of pollutants is limited. On the other hand, surface atomic oxygen (*O), as a non-radical active oxygen, has a higher oxidation potential (2.43 V) and can achieve extensive degradation of organic matter through oxidation mechanisms such as addition reactions, hydrogen extraction and electron transfer.

[0004] Currently, the generation of *O mainly relies on synthetic catalysts, which involve complex preparation processes and limited applications. Therefore, there is an urgent need to develop new, efficient, and simple *O catalytic strategies. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a water treatment method based on non-radical oxidation. This method generates calcium carbonate in situ in wastewater, utilizes the calcium carbonate to catalyze the decomposition of ozone on its surface to generate highly reactive atomic oxygen (*O), and achieves efficient oxidative degradation of pollutants through a direct electron transfer mechanism between atomic oxygen and organic pollutant molecules. This method overcomes the limitations of traditional free radical pathways, avoids the quenching problem of hydroxyl radicals, and has the advantages of high catalytic efficiency, good stability, environmental friendliness, and no need for additional catalyst carriers. Simultaneously, it can achieve efficient removal of calcium ions from wastewater and can be widely applied to water treatment and the deep treatment of recalcitrant organic wastewater.

[0006] In a first aspect, the present invention provides a water treatment method based on non-radical oxidation, the water treatment method comprising: Soluble carbonates are added to wastewater containing calcium ions to obtain calcium carbonate crystals. Then, ozone is introduced to oxidize the wastewater and obtain purified water.

[0007] The water treatment method provided by this invention can utilize calcium ions in wastewater to generate calcium carbonate in situ. Then, calcium carbonate catalyzes the decomposition of ozone on its surface to generate highly reactive atomic oxygen (*O). The method achieves efficient oxidative degradation of pollutants through a direct electron transfer mechanism between atomic oxygen and organic pollutant molecules. This method overcomes the limitations of traditional free radical pathways, avoids the quenching problem of hydroxyl radicals, and has the advantages of high catalytic efficiency, good stability, environmental friendliness, and no need for additional catalyst carriers. Simultaneously, it can achieve efficient removal of calcium ions from wastewater and can be widely applied to water treatment and the deep treatment of recalcitrant organic wastewater.

[0008] The reaction principle of the water treatment method of this invention is as follows: carbonate ions, as crystallizing agents, react with calcium ions in situ to generate calcium carbonate crystals in water. Ozone is then rapidly introduced. The generated calcium carbonate crystals can improve the utilization efficiency of ozone and catalyze the formation of atomic oxygen on the surface of ozone, forming *O-CaCO3. *O-CaCO3 has a higher oxidation potential than ozone and can undergo stronger electron transfer with organic matter, thereby achieving efficient oxidative degradation of pollutants.

[0009] As a preferred embodiment of the present invention, the soluble carbonate includes any one or more of sodium carbonate, potassium carbonate, and ammonium carbonate.

[0010] As a preferred embodiment of the present invention, the amount of soluble carbonate used is such that its concentration in the wastewater is 5-100 mmol / L, for example, 5 mmol / L, 10 mmol / L, 30 mmol / L, 50 mmol / L, 80 mmol / L, 100 mmol / L, etc.

[0011] As a preferred embodiment of the present invention, the concentration of calcium ions in the wastewater is 5-100 mmol / L, such as 5 mmol / L, 10 mmol / L, 30 mmol / L, 50 mmol / L, 80 mmol / L, 100 mmol / L, etc.

[0012] As a preferred embodiment of the present invention, the ozone injection rate is 0.2-10 mg / min, for example 0.2 mg / min, 1 mg / min, 2 mg / min, 5 mg / min, 8 mg / min, or 10 mg / min.

[0013] As a preferred embodiment of the present invention, the oxidation treatment time is 20-60 min, for example 20 min, 30 min, 40 min, 50 min, 60 min, etc.

[0014] As a preferred embodiment of the present invention, the COD value of the wastewater is 200-10000 mg / L, such as 200 mg / L, 500 mg / L, 1000 mg / L, 3000 mg / L, 5000 mg / L, 8000 mg / L, 10000 mg / L, etc.

[0015] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: The water treatment method provided by this invention can generate calcium carbonate in situ in wastewater. Calcium carbonate catalyzes the decomposition of ozone on its surface to generate highly reactive atomic oxygen. The efficient oxidative degradation of pollutants is achieved through a direct electron transfer mechanism between atomic oxygen and organic pollutant molecules. This method overcomes the limitations of traditional free radical pathways, avoids the quenching problem of hydroxyl radicals, and has the advantages of high catalytic efficiency, good stability, environmental friendliness, and no need for additional catalyst carriers. Simultaneously, it can achieve efficient removal of calcium ions from wastewater and can be widely applied to water treatment and the deep treatment of recalcitrant organic wastewater. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the reaction principle of the water treatment method described in Embodiment 1 of the present invention. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0021] Example 1 This embodiment provides a water treatment method based on non-radical oxidation, and its reaction principle diagram is shown below. Figure 1 As shown, the water treatment method includes: Using 1L of fracturing flowback fluid from an oil well as the wastewater to be treated, the concentration of calcium ions was 67.4 mmol / L, COD was 3254 mg / L, and UV was... 254 It is 1.032 cm. -1 Sodium carbonate was added to wastewater, resulting in a concentration of 67.4 mmol / L, to obtain calcium carbonate crystals. Ozone was then introduced at a dosage of 1.5 mg / min for 40 min. After treatment, the calcium ion concentration was 0.4 mmol / L, COD decreased to 1764 mg / L, and UV radiation decreased. 254 It decreased to 0.394 cm. -1 .

[0022] Example 2 This embodiment provides a water treatment method based on non-radical oxidation, the water treatment method comprising: Using 1L of fracturing flowback fluid from an oil well as the wastewater to be treated, the concentration of calcium ions was 67.4 mmol / L, COD was 3254 mg / L, and UV was... 254 It is 1.032 cm. -1 Potassium carbonate was added to wastewater, resulting in a concentration of 67.4 mmol / L, to obtain calcium carbonate crystals. Ozone was then introduced at a dosage of 1.5 mg / min for 60 min. After treatment, the calcium ion concentration was 0.4 mmol / L, COD decreased to 1032 mg / L, and UV radiation... 254 It decreased to 0.295 cm. -1 .

[0023] Comparative Example 1 This comparative example provides a wastewater treatment method, which is the same as that in Example 1, except that ozone gas is not introduced in this comparative example. After treatment, the calcium ion concentration is 1 mmol / L, COD decreases to 2566 mg / L, and UV... 254 Decreased to 0.66 cm -1 .

[0024] Comparative Example 2 This comparative example provides a wastewater treatment method, which is the same as that in Example 1, except that sodium carbonate is not added. After treatment, the calcium ion concentration was 62.55 mmol / L, COD decreased to 3001 mg / L, and UV... 254 Decreased to 0.47 cm-1 .

[0025] A comparison of Example 1 and Comparative Examples 1-2 reveals that the water treatment method based on non-radical oxidation provided by the present invention can achieve efficient oxidative degradation of pollutants in wastewater and efficient removal of calcium ions.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0027] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A water treatment method based on non-radical oxidation, characterized in that, The water treatment method includes: Soluble carbonates are added to wastewater containing calcium ions to obtain calcium carbonate crystals. Then, ozone is introduced to oxidize the wastewater and obtain purified water.

2. The water treatment method according to claim 1, characterized in that, The soluble carbonate includes any one or more of sodium carbonate, potassium carbonate, and ammonium carbonate.

3. The water treatment method according to claim 1 or 2, characterized in that, The amount of the soluble carbonate used is such that its concentration in the wastewater is 5-100 mmol / L.

4. The water treatment method according to any one of claims 1-3, characterized in that, The concentration of calcium ions in the wastewater is 5-100 mmol / L.

5. The water treatment method according to any one of claims 1-4, characterized in that, The ozone injection rate is 0.2-10 mg / min.

6. The water treatment method according to any one of claims 1-5, characterized in that, The oxidation treatment time is 20-60 min.

7. The water treatment method according to any one of claims 1-6, characterized in that, The COD value of the wastewater is 200-10000 mg / L.

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