Method for removing pollutants in sewage

Abstract

The invention discloses a method for removing pollutants in sewage. The method comprises the following steps: S1, mixing sewage, a ferric iron-containing compound and peracetic acid to obtain a mixed solution; s2, irradiating the mixed solution with 222-230nm ultraviolet light to react to remove pollutants; the pollutants comprise at least one of carbamazepine, sulfamethoxazole, benzodiazole and trimethoprim. According to the method, far ultraviolet light (FUV, 222-230 nm) is introduced to strengthen Fe (III) to activate PAA, so that the problem of insufficient reaction activity of a Fe (III) / PAA system is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly to a method for removing pollutants from sewage. Background Art

[0002] The widespread presence of emerging organic pollutants in water bodies has become an important environmental pollution problem. These pollutants include pharmaceutical residues, pesticides, industrial chemicals, etc. Due to their persistence and bioaccumulation, traditional water treatment processes (such as coagulation, sedimentation, biological treatment, etc.) are difficult to effectively remove. Therefore, the development of efficient and environmentally friendly new water treatment technologies has become a current research hotspot. In recent years, the advanced oxidation process based on peracetic acid (PAA) has received extensive attention due to its high efficiency and environmental friendliness. PAA is a strong oxidant, and after activation, it can generate organic free radicals (such as CH3C(O)OO·) and hydroxyl radicals (·OH), which can efficiently degrade various organic pollutants. However, the activation of PAA requires efficient activation means, such as transition metals or ultraviolet light. Among them, Fe(II), as a green transition metal, is widely used to activate PAA to generate free radicals for degrading pollutants.

[0003] However, the Fe(II) / PAA process has significant problems in practical applications: Fe(II) is easily oxidized to Fe(III) during the reaction, resulting in a slow iron cycling rate and insufficient continuous reaction ability, thereby reducing the pollutant removal efficiency. To improve the iron cycling efficiency, existing research mostly uses ultraviolet light activation technology. However, traditional ultraviolet activation technologies mainly use medium ultraviolet (UV-C, 254 nm) or near-ultraviolet light sources, which have limited reduction ability for Fe(III) and do not form a synergistic effect with PAA activation.

[0004] To solve the above problems, it is urgent to develop an activation technology that can remove emerging organic pollutants from water bodies. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a method for removing pollutants from sewage.

[0006] According to a first aspect of the present invention, there is provided a method for removing pollutants from sewage, the method comprising the following steps:

[0007] S1. Mix sewage, a compound containing ferric iron, and peracetic acid to obtain a mixed solution;

[0008] S2. Irradiate the mixed solution with ultraviolet light at 222 - 230 nm to react and remove pollutants;

[0009] The pollutants include at least one of carbamazepine, sulfamethoxazole, atrazine, and bisphenol A.

[0010] The present invention solves the problem of insufficient reactivity of the Fe(III) / PAA system by introducing far ultraviolet light (FUV, 222 - 230 nm) to enhance the activation of PAA by Fe(III). The photochemical effects of FUV are mainly reflected in the following two aspects: 1. Direct activation of PAA: FUV can efficiently excite PAA molecules to generate highly reactive hydroxyl radicals (·OH) and acetate radicals (CH3COO·), thereby enhancing the oxidation ability of the system; 2. Promotion of the Fe(III) / Fe(II) cycle: FUV converts Fe(III) into Fe(II) through photoreduction, accelerating the Fe(III) / Fe(II) cycle, further enhancing the activation efficiency of PAA, forming a chain reaction of "activation - reduction - re - activation", and significantly improving the oxidation performance of the system. Under the irradiation of the FUV light source, the water body is stirred for reaction, and the photochemical effects of FUV are used to continuously enhance the oxidation performance of the Fe(III) / PAA system. Through the generated reactive radicals and highly oxidizing substances, organic pollutants in water are efficiently degraded.

[0011] According to some embodiments of the present invention, in the mixed solution, the concentration of the iron(III) - containing compound is 2 - 10 μM, and the concentration of peracetic acid is 90 - 100 μM.

[0012] Under the above conditions, it can effectively catalyze the decomposition of peracetic acid (PAA) to generate hydroxyl radicals (OH) and acetate radicals (CH3COO). These radicals are strong oxidants and can efficiently degrade organic pollutants in water. During the reaction process, Fe(III) will be reduced to Fe(II), and Fe(II) can be re - oxidized to Fe(III) by PAA or other oxidants, forming an Fe(III) / Fe(II) cycle. This cyclic mechanism can continuously catalyze the activation of PAA and improve the oxidation efficiency. Controlling the concentrations of Fe(III) and PAA within a relatively low range can reduce by - products generated by the self - decomposition of Fe(III) and PAA, such as Fe(OH)3 precipitation or ineffective PAA decomposition products. This ensures the cleanliness and high efficiency of the reaction system.

[0013] Fe(III)+PAA→Fe(II)+·OH+CH3COO·

[0014] Fe(II)+PAA→Fe(III)+·OH+CH3COO·Fe(II)+PAA→Fe(III)+·OH+CH3COO·

[0015] According to some embodiments of the present invention, during the reaction, the pH value of the reaction system is 4 - 9.

[0016] In the range of pH 4 - 9, Fe(III) can maintain a stable dissolved state. When the pH is too low (<4), Fe(III) may exist in the form of hydrated iron ions with low activity. When the pH is too high (>9), Fe(III) will form insoluble Fe(OH)3 precipitate and lose its catalytic activity. Stability of peracetic acid (PAA): PAA is most stable in an environment close to neutral or weakly acidic (pH 5 - 7). When the pH is too high, PAA will decompose rapidly, reducing its oxidation ability. When the pH is too low, the activation efficiency of PAA is affected.

[0017] According to some embodiments of the present invention, the iron(III)-containing compound includes at least one of ferric chloride, ferric sulfate, sodium ferrate, and potassium ferrate.

[0018] According to some embodiments of the present invention, the method includes the following steps:

[0019] S1. Add the iron(III)-containing compound and peracetic acid to the sewage in sequence and mix to obtain a mixed solution;

[0020] S2. Irradiate the mixed solution with ultraviolet light at 222 - 230 nm to react and remove pollutants.

[0021] As a catalyst, Fe(III) can activate peracetic acid (PAA) to generate highly reactive hydroxyl radicals (·OH) and acetate radicals (CH3COO·). Adding Fe(III) first can ensure that PAA is immediately activated after addition, improve the reaction rate, and stabilize the reaction system: Fe(III) can be evenly distributed in the solution after addition, forming a stable catalytic environment, providing a basis for subsequent PAA activation and radical generation. If PAA is added first, in the absence of a catalyst, PAA may decompose ineffectively without generating radicals, reducing its oxidation efficiency. Adding PAA later can ensure its efficient decomposition under the catalysis of Fe(III). Controlling the generation of radicals: The addition timing of PAA is synchronized with the catalytic action of Fe(III), which can precisely control the generation of radicals, avoid excessive or insufficient radicals, and thus optimize the degradation effect of pollutants.

[0022] According to some embodiments of the present invention, the reaction includes a stirring reaction, and the rotation speed of the stirring reaction is 600 - 800 r / min.

[0023] According to some embodiments of the present invention, in the system obtained after mixing, the concentration of the iron(III)-containing compound is 2 - 3 μM, and the concentration of peracetic acid is 100 μM.

[0024] According to some embodiments of the present invention, the wavelength of the ultraviolet light is 222 nm.

[0025] According to some embodiments of the present invention, the reaction time is 20 to 40 minutes.

[0026] According to some embodiments of the present invention, the peracetic acid comprises an aqueous solution of peracetic acid with a mass percentage concentration of 15% to 30%.

[0027] Unless otherwise specified, the "about" in the present invention actually means that the allowable error is within the range of ±2%. For example, about 100 is actually 100 ± 2% × 100.

[0028] Unless otherwise specified, the "between... and..." in the present invention includes the numbers themselves. For example, "between 2 and 3" includes the endpoint values 2 and 3.

[0029] Other features and advantages of the present invention will be described in the following specification, and in part, will become apparent from the specification, or will be understood by implementing the present invention. Detailed Embodiments

[0030] The following will clearly and completely describe the concept and technical effects of the present invention in combination with the embodiments to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0031] In the description of the present invention, the description of reference terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0032] Example 1

[0033] This example provides a method for removing pollutants from sewage, specifically the following steps:

[0034] S1. Add 2 μM of Fe(III) and 100 μM of PAA to a deionized water source containing 5 μM of carbamazepine, and mix to obtain a mixed solution;

[0035] S2. Stir for 15 min under the irradiation of 222 nm FUV to complete the removal of organic pollutants in water by Fe(III) / PAA; wherein the Fe(III) is FeCl3 solution, the pH of the reaction solution is 7, the reaction stirring speed is 600 r / min, and the feeding sequence of Fe(III) and PAA is to add Fe(III) first and then PAA.

[0036] The removal rate of carbamazepine in this example is 96.4%.

[0037] Example 2

[0038] This example provides a method for removing pollutants in sewage, specifically the following steps:

[0039] S1. Add 5 μM Fe(III) and 100 μM PAA to a deionized water source containing 5 μM carbamazepine, and mix to obtain a mixed solution;

[0040] S2. Stir for 10 min under the irradiation of 222 nm FUV to complete the removal of organic pollutants in water by Fe(III) / PAA; wherein the Fe(III) is FeCl3 solution, the pH of the reaction solution is 7, the reaction stirring speed is 600 r / min, and the feeding sequence of Fe(III) and PAA is to add Fe(III) first and then PAA.

[0041] The removal rate of carbamazepine in this example is 87.8%.

[0042] Example 3

[0043] This example provides a method for removing pollutants in sewage, specifically the following steps:

[0044] S1. Add 2 μM Fe(III) and 100 μM PAA to a deionized water source containing 5 μM carbamazepine and mix to obtain a mixed solution;

[0045] S2. Stir for 15 min under the irradiation of 222 nm FUV to complete the removal of organic pollutants in water by Fe(III) / PAA; wherein the Fe(III) is FeCl3 solution, the pH of the reaction solution is 9, the reaction stirring speed is 600 r / min, and the feeding sequence of Fe(III) and PAA is to add Fe(III) first and then PAA.

[0046] The removal rate of carbamazepine in this example is 86.3%.

[0047] Example 4

[0048] This example provides a method for removing pollutants in sewage, specifically the following steps:

[0049] S1. Add 3 μM of Fe(III) and 110 μM of PAA to a deionized water source containing 5 μM of carbamazepine simultaneously and mix them to obtain a mixed solution;

[0050] S2. Stir for 15 min under irradiation of 222 nm FUV to complete the removal of organic pollutants in water by Fe(III) / PAA; wherein the Fe(III) is an FeCl3 solution, the pH of the reaction solution is 7, and the reaction stirring speed is 600 r / min.

[0051] The removal rate of carbamazepine in this example is 86.4%.

[0052] Example 5:

[0053] The method for reducing Fe(III) by FUV and promoting the Fe(III) / Fe(II) cycle in this example is realized according to the following steps:

[0054] Add 20 μM of Fe(III) to a blank deionized water source and carry out a stirring reaction under FUV irradiation for 30 minutes to complete the reduction of Fe(III) by FUV. The pH of the reaction solution is 7, and the reaction stirring speed is 600 r / min.

[0055] After adding FUV in this example, the concentration of Fe(II) in water gradually increases with the reaction time. This example proves that FUV light irradiation can promote the iron cycle without adding pollutants.

[0056] Comparative Example 1

[0057] This example provides a method for removing pollutants in sewage, specifically the following steps:

[0058] S1. Add 2 μM of Fe(III) and 100 μM of PAA to a deionized water source containing 5 μM of carbamazepine and mix them to obtain a mixed solution; the pH of the reaction is 7, the reaction stirring speed is 600 r / min, and the addition order of Fe(III) and PAA is to add Fe(III) first and then PAA.

[0059] The removal rate of carbamazepine in this example is 8.3%.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 1 is that traditional ultraviolet light of 254 nm is used instead of far ultraviolet light (FUV) of 222 - 230 nm, and other conditions are the same as those in Example 1.

[0062] The removal rate of carbamazepine in this example is 76.4%.

[0063] The above has been described in detail in connection with the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for removing pollutants in sewage, characterized in that, The method comprises the following steps: S1. Mix sewage, a ferric iron-containing compound, and peracetic acid to obtain a mixed solution; S2. React the mixed solution under ultraviolet light irradiation at 222 - 230 nm to remove pollutants; The pollutants include at least one of carbamazepine, sulfamethoxazole, benzodiazole, and trimethoprim.

2. The method for removing pollutants from sewage according to claim 1, characterized in that, In the mixed solution, the concentration of the ferric iron-containing compound is 2 - 10 μM, and the concentration of peracetic acid is 90 - 100 μM.

3. The method for removing pollutants from sewage according to claim 1, characterized in that, During the reaction, the pH value of the reaction system is 4 - 9.

4. The method for removing pollutants from sewage according to claim 1, characterized in that, The ferric iron-containing compound includes at least one of ferric chloride, ferric sulfate, sodium ferrate, and potassium ferrate.

5. The method for removing pollutants from sewage according to claim 1, characterized in that, The method comprises the following steps: S1. Sequentially add a ferric iron-containing compound and peracetic acid to sewage and mix them to obtain a mixed solution; S2. React the mixed solution under ultraviolet light irradiation at 222 - 230 nm to remove pollutants.

6. The method for removing pollutants from sewage according to claim 1, wherein The reaction includes a stirring reaction, and the rotation speed of the stirring reaction is 600 - 800 r / min.

7. The method for removing pollutants from sewage according to claim 1, characterized in that, In the system obtained after mixing, the concentration of the ferric iron-containing compound is 2 - 3 μM, and the concentration of peracetic acid is 100 μM.

8. The method for removing pollutants from sewage according to claim 1, wherein, The wavelength of the ultraviolet light is 222 nm.

9. The method for removing pollutants from sewage according to claim 1, characterized in that, The reaction time is 10 - 40 min.

10. The method for removing pollutants from sewage according to claim 1, characterized in that, The peracetic acid includes an aqueous solution of peracetic acid with a mass percentage concentration of 15% - 30%.