Method for removing metal pollutants through advanced oxidation enhanced filtration

Abstract

The invention discloses a method for removing metal pollutants by advanced oxidation enhanced filtration, which comprises the following steps: mixing raw water to be treated containing manganese pollutants with peroxymonosulfate, carrying out ultraviolet radiation, and carrying out oxidation reaction to obtain an oxidized water body; the oxidized water body is filtered through quartz sand, manganese pollutants are removed through reaction, and the purified water body is obtained. By adopting a method of coupling peroxymonosulfate, ultraviolet radiation and quartz sand filtration, the originally mild peroxymonosulfate can be converted into a relatively active oxidation system, the efficient oxidation of the manganese pollutants is realized, the required treatment time is short, and the treatment cost is low. The deep removal of manganese pollutants in low-concentration raw water can be realized under the conditions that a complexing agent is not added, an expensive special adsorbent is not used and a complex filter material is not used.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and in particular relates to a method for removing metal pollutants by using advanced oxidation-enhanced filtration. Background Technology

[0002] Manganese (Mn) is a common heavy metal pollutant in raw water. The "Standards for Drinking Water Quality" (GB 5749-2022) clearly specifies the concentration of this heavy metal ion, requiring that the manganese concentration not exceed 0.1 mg / L. Excessive heavy metal levels can significantly impact water quality and human health. For example, high manganese content can cause treated water to turn yellowish-brown, develop an unpleasant odor, and lead to sediment buildup in pipe networks, affecting their lifespan. Therefore, the stable removal of manganese ions in water treatment processes is one of the key issues in ensuring drinking water safety.

[0003] In natural water bodies, manganese mainly exists in the form of dissolved Mn(II). Currently, mainstream manganese removal processes primarily rely on chemical oxidation or biological oxidation, which oxidizes dissolved manganese into Mn(III) / Mn(IV), generating particulate manganese oxides (MnOx) which are then removed. In practical applications, biological oxidation, which relies on microbial communities fixed on filter media to oxidize manganese ions and retain them in the filter bed, is easily affected by water quality factors such as effluent temperature and dissolved oxygen concentration, exhibiting high instability. Cost control is also difficult, thus presenting challenges in practical applications. Existing manganese oxidation processes often rely on pre-oxidation with potassium permanganate or chlorine-containing oxidants (sodium hypochlorite, chlorine dioxide, etc.) combined with filtration in manganese sand or quartz sand filters. The methods described above have demonstrated good removal rates and practicality in practice, but they also have corresponding problems. For example, in the traditional potassium permanganate oxidation process, the dosage of potassium permanganate is difficult to control. At low concentrations, it is difficult to reduce the heavy metal content below the standard value. At high concentrations, the residual permanganate ions themselves may cause water discoloration or secondary exceedance of manganese content. Therefore, the dosage of potassium permanganate must be strictly controlled. The traditional sodium hypochlorite pre-oxidation method is not very effective for low-concentration raw water, and the effect of pre-filtration addition is not obvious. The treatment effect is highly dependent on the contact reaction time. In addition, there are also problems such as large oxidant dosage, new water quality problems caused by high concentrations of permanganate and residual chlorine, high adsorbent cost, and difficulty in filter column regeneration. Furthermore, the ability to remove manganese is not stable at lower temperatures and lower initial concentrations.

[0004] Sand filtration is a crucial step in water treatment at water plants. In waterworks, sand filtration is a physical filtration technology primarily used to remove suspended particles, colloidal substances, and some microorganisms from water. Commonly used sand filter materials include manganese sand, quartz sand, and activated carbon. Quartz sand is the most commonly used filter material in waterworks, but current research indicates that quartz sand filtration is less effective at removing manganese, thus indicating significant room for improvement.

[0005] Persulfate (PMS, usually composed mainly of potassium persulfate) can generate sulfate free radicals (SO4) under appropriate conditions. - PMS (particulate matter) contains · and hydroxyl radicals (·OH), exhibiting high redox potentials and a wide applicable pH range, making it a rapidly developing class of advanced oxidants in recent years. Compared to potassium permanganate and sodium hypochlorite oxidants commonly used in water treatment, PMS treatment avoids the color problems caused by residual chlorine and potassium permanganate residues, has less impact on water quality, and allows for more flexible dosage. The synergistic removal of iron, manganese, and trace organic matter from groundwater using PMS has been validated and reported. For example, one study disclosed a filtration method in groundwater using in-situ activated PMS with iron and manganese ions coupled with anthracite / quartz sand dual-layer filter media. This method enhances the removal of Fe from groundwater by adding a complexing agent. 2+ Mn 2+ Activation of PMS simultaneously removed iron, manganese, and micro-polluting organic matter within a dual-layer filter, achieving good treatment results.

[0006] However, the aforementioned study used a high manganese concentration, exceeding the peak-period standards for raw water in typical water treatment plants. Furthermore, the study employed complexing agent activation and a dual-layer composite filter media of anthracite / quartz sand, resulting in a relatively complex overall treatment system with a large number of added and operating chemicals. This makes it difficult to easily implement in conventional water treatment plants or mine water treatment systems. For raw water from water treatment plants characterized primarily by excessive manganese levels, a treatment process that is simple in structure, requires fewer chemical types, and can operate stably for extended periods remains lacking. Summary of the Invention

[0007] In order to overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide a method for removing metal pollutants by using advanced oxidation-enhanced filtration. This method can effectively treat water bodies with low concentrations of manganese pollution, and the process is simple, can operate stably for a long time, and has low operating costs.

[0008] A second objective of this invention is to provide an apparatus for removing metal contaminants using advanced oxidation-enhanced filtration.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a method for removing metal pollutants using advanced oxidation-enhanced filtration, comprising the following steps: mixing raw water containing manganese pollutants with persulfate (PMS), subjecting it to ultraviolet irradiation to an oxidation reaction, and obtaining oxidized water; filtering the oxidized water through quartz sand to remove manganese pollutants by reaction, and obtaining purified water.

[0010] In the method of this invention, persulfate (PMS), after being activated by ultraviolet irradiation, can rapidly react with manganese pollutants (Mn(II)) in the raw water to be treated, generating a large amount of high-valence manganese oxides (MnO). x The manganese oxide particles themselves can also activate the PMS, further promoting the oxidation process. The resulting oxidized water contains manganese oxide particles and dissolved manganese ions. After oxidation by the PMS, the dissolved manganese ions form manganese oxide, which can be in situ loaded on the surface of the quartz sand to form a composite oxide film (manganese oxide film) mainly composed of high-valence manganese oxides. This oxide film serves two purposes: firstly, it acts as a heterogeneous catalytic active site for the PMS, continuously activating the PMS to generate free radicals; secondly, it provides a large number of adsorption and internal coordination sites for manganese ions, achieving efficient adsorption and capture of manganese. After the formation of this interfacial oxidation system, the manganese oxide film produced during the oxidation process will further develop the system, thereby continuously improving the filtration performance of the quartz sand and achieving better treatment results.

[0011] In some embodiments of the present invention, the manganese contaminant is manganese ions (Mn(II)).

[0012] In some embodiments of the present invention, the oxidizing water contains manganese oxide particles and dissolved manganese ions.

[0013] In some embodiments of the present invention, a manganese oxide film forms on the surface of the quartz sand after filtration. A significant change in the surface morphology of the quartz sand was observed after the filtration reaction, indicating the formation of the manganese oxide film.

[0014] In some embodiments of the present invention, the manganese content on the surface of the quartz sand after filtration is 10-20 wt%; in some specific embodiments of the present invention, the manganese content on the surface of the quartz sand after filtration is 12-16 wt%. The formed manganese oxide film significantly increases the manganese content on the surface of the quartz sand, which also indicates the formation of a mature interfacial oxidation system.

[0015] In some embodiments of the present invention, the persulfate includes potassium persulfate, sodium persulfate, or a combination thereof; in some specific embodiments of the present invention, the persulfate is selected from potassium persulfate; in some more specific embodiments of the present invention, the potassium persulfate is a potassium persulfate complex salt; its chemical formula is K5H3S4O. 18 (or 2KHSO5·KHSO4·K2SO4).

[0016] In some embodiments of the present invention, the mass ratio of the persulfate to the manganese content in the raw water to be treated is (1~15):1; in some specific embodiments of the present invention, the mass ratio of the persulfate to the manganese content in the raw water to be treated is (1.5~12):1; in some more specific embodiments of the present invention, the mass ratio of the persulfate to the manganese content in the raw water to be treated is (5~10):1.

[0017] In some embodiments of the present invention, the manganese content in the raw water to be treated is 0.05~0.5 mg / L; in some specific embodiments of the present invention, the manganese content in the raw water to be treated is 0.1~0.4 mg / L; in some more specific embodiments of the present invention, the manganese content in the raw water to be treated is 0.2~0.3 mg / L.

[0018] In some embodiments of the present invention, the pH value of the raw water to be treated is 6.8 to 7.3; in some specific embodiments of the present invention, the pH value of the raw water to be treated is 6.85 to 7.25; in some more specific embodiments of the present invention, the pH value of the raw water to be treated is 6.9 to 7.2.

[0019] In some embodiments of the present invention, the manganese content in the purified water is ≤0.1 mg / L; specifically, it can be 0.001~0.1 mg / L. In some specific embodiments of the present invention, the manganese content in the purified water is ≤0.01 mg / L; specifically, it can be 0.001~0.01 mg / L.

[0020] In some embodiments of the present invention, the power of the ultraviolet irradiation is 300~1200W; in some specific embodiments of the present invention, the power of the ultraviolet irradiation is 400~1000W; in some more specific embodiments of the present invention, the power of the ultraviolet irradiation is 450~550W.

[0021] In some embodiments of the present invention, the ultraviolet irradiation time is 0.5 to 5 minutes; in some specific embodiments of the present invention, the ultraviolet irradiation time is 1 to 4 minutes; and in some more specific embodiments of the present invention, the ultraviolet irradiation time is 1.5 to 2.5 minutes.

[0022] In some embodiments of the present invention, the wavelength of the ultraviolet light used for ultraviolet irradiation is 200-300 nm; in some specific embodiments of the present invention, the wavelength of the ultraviolet light used for ultraviolet irradiation is 250-260 nm.

[0023] In some embodiments of the present invention, the oxidation reaction takes 20 to 40 minutes; in some specific embodiments of the present invention, the oxidation reaction takes 25 to 35 minutes.

[0024] In some embodiments of the present invention, the filtration speed is 6~10 m / h; in some specific embodiments of the present invention, the filtration speed is 7~9 m / h.

[0025] In some embodiments of the present invention, the particle size of the quartz sand is 0.7~1.2mm and the uniformity coefficient is ≤1.6; specifically, the uniformity coefficient can be 1~1.6.

[0026] In some embodiments of the present invention, the thickness of the filter layer formed by the quartz sand is 0.6~1m; in some specific embodiments of the present invention, the thickness of the filter layer formed by the quartz sand is 0.7~0.9m.

[0027] In some embodiments of the present invention, the raw water to be treated is further subjected to coagulation and sedimentation treatment before being mixed with persulfate.

[0028] In some embodiments of the present invention, the reagents used in the coagulation and sedimentation treatment include pH adjusters.

[0029] In some embodiments of the present invention, the pH adjuster includes at least one of sodium carbonate, potassium carbonate, or ammonium carbonate; in some embodiments of the present invention, the pH adjuster is selected from sodium carbonate (Na2CO3).

[0030] Sodium hydroxide, potassium hydroxide, and other bases are too alkaline, which can easily lead to pH instability in the system during long-term use. Using the pH adjusters mentioned above can obtain a more stable reaction system.

[0031] In some embodiments of the present invention, the dosage of the pH adjuster is 10-20 mg / L; in some specific embodiments of the present invention, the dosage of the pH adjuster is 12-18 mg / L. The dosage of the pH adjuster can be adjusted according to the conditions of the raw water to be treated.

[0032] In some embodiments of the present invention, the pH of the water is adjusted to 6.9-7.1 using the pH adjuster. Good removal efficiency can be achieved within this pH range, and it meets the requirements of water plant application scenarios.

[0033] In some embodiments of the present invention, the reagents used in the coagulation and sedimentation treatment also include coagulants. Depending on the turbidity of the raw water to be treated, coagulants can be added to improve the treatment effect.

[0034] In some embodiments of the present invention, the coagulant includes at least one of polyaluminum chloride, polyaluminum sulfate, polyferric chloride, or polyferric sulfate; in some specific embodiments of the present invention, the coagulant is selected from polyaluminum chloride (PAC). All of the above-mentioned inorganic polymeric coagulants can achieve good coagulation effects, among which polyaluminum chloride has large molecular particles, strong adsorption capacity, and lower treatment costs, resulting in superior coagulation effects.

[0035] In some embodiments of the present invention, the dosage of the coagulant is 10-20 mg / L; in some specific embodiments of the present invention, the dosage of the coagulant is 12-18 mg / L.

[0036] In some embodiments of the present invention, the method for removing metal contaminants using advanced oxidation-enhanced filtration employs a processing temperature of 20-25°C.

[0037] A second aspect of the present invention provides an apparatus for removing metal contaminants using advanced oxidation-enhanced filtration, comprising a settling reaction tank and a quartz sand filter tank connected in sequence; the settling reaction tank is provided with a water inlet, an oxidant dosing port and an ultraviolet device; the water inlet is used to introduce raw water containing manganese contaminants; the oxidant dosing port is used to add persulfate; and the ultraviolet device is used to irradiate the water with ultraviolet light.

[0038] In some embodiments of the present invention, the apparatus for removing metal contaminants by advanced oxidation-enhanced filtration is used to perform the method for removing metal contaminants by advanced oxidation-enhanced filtration as described in the first aspect of the present invention.

[0039] In some embodiments of the present invention, a quartz sand filter layer and a cushion layer are sequentially arranged in the quartz sand filter tank; specifically, the quartz sand filter layer is composed of a single quartz sand filter material, and the thickness of the quartz sand filter layer is 0.6~1m; the cushion layer can be composed of pebbles, and the thickness of the cushion layer is 0.2~0.3m.

[0040] In some embodiments of the present invention, the settling reaction tank is also connected to a coagulation sedimentation tank; the coagulation sedimentation tank is provided with a pH adjuster inlet. The pH adjuster inlet is used to add a pH adjuster to the coagulation sedimentation tank.

[0041] In some embodiments of the present invention, the coagulation sedimentation tank is further provided with a coagulant inlet. The coagulant inlet is used to add coagulant to the coagulation sedimentation tank.

[0042] The beneficial effects of this invention are: This invention uses a coupling method of persulfate, ultraviolet irradiation and quartz sand filtration, which can transform the originally mild persulfate into a more active oxidation system, achieving efficient oxidation of manganese pollutants. The required treatment time is short, and deep removal of low-concentration manganese pollutants from raw water can be achieved without adding complexing agents, using expensive special adsorbents and without complex filter media.

[0043] Specifically, compared with the prior art, the present invention has the following advantages: 1) This invention uses ultraviolet irradiation as a method to promote oxidation treatment. After introduction, it can greatly promote the decomposition of permonosulfate (PMS), activating it to generate more potent sulfate free radicals (SO4). - ·), thereby significantly enhancing its ability to oxidize and degrade pollutants. The specific reaction mechanism is that ultraviolet treatment can break the peroxide bond (-OO-) in the PMS molecule, thereby generating a large number of sulfate radicals and hydroxyl radicals, which then react as follows: This transforms the relatively mild PMS oxidant into a more active free radical, thereby enhancing the oxidizing ability of manganese (converting Mn(II) into Mn(III)).

[0044] 2) The coupling of persulfate (PMS) with quartz sand can also enhance the oxidation capacity of persulfate. After PMS converts Mn(II) in the raw water into manganese oxides, the generated manganese oxides act as a medium to improve the oxidation activity of PMS. Furthermore, the generated manganese oxides adhere to the surface of the quartz sand, forming an interfacial oxidation system, further enhancing the overall oxidation capacity of the process. Therefore, the method of this invention can achieve deep removal of low-concentration Mn(II) from raw water without adding complexing agents, using expensive specialized adsorbents, or employing complex filter media. Attached Figure Description

[0045] Figure 1 This is a reaction flow diagram of various embodiments of the present invention.

[0046] Figure 2 This is a diagram of the surface morphology of the quartz sand before the reaction.

[0047] Figure 3 This is a diagram of the surface morphology of the quartz sand after the reaction.

[0048] Figure 4 This is a comparison chart of the manganese removal effects of Example 1 and Comparative Example 1.

[0049] Figure 5 This is a comparison chart of the manganese removal effects of Example 2 and Comparative Example 1.

[0050] Figure 6 This is a comparison chart of the manganese removal effects of Example 1 and Comparative Example 2.

[0051] Figure 7 This is a comparison chart of the manganese removal effects of Example 2 and Comparative Example 3.

[0052] Figure 8 The diagram shows a comparison of the manganese removal effects of Examples 3-4 and Comparative Example 1.

[0053] Figure 9 The diagram shows a comparison of the manganese removal effects of Examples 5-6 and Comparative Example 1.

[0054] Figure 10 The diagram shows a comparison of the manganese removal effects of Example 7 and Comparative Examples 1 and 4. Detailed Implementation

[0055] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0056] It should be noted that the following information pertains to some of the raw materials and instruments used in the embodiments and comparative examples: Potassium persulfate (PMS): 42-46%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; this potassium persulfate is a potassium peroxymonosulfate complex salt, with the chemical formula K5H3S4O. 18 (2KHSO5·KHSO4·K2SO4), the target mass concentration of potassium persulfate (C) PMS (Based on the effective concentration of potassium persulfate)

[0057] Manganese sulfate (MnSO4): 98% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. pH meter: Model SD305, purchased from Loebbon; Manganese analyzer: Model MD640, purchased from Luo Weibang; Colorimeter: Model DGB-421, purchased from Leici.

[0058] The detection methods used in the following embodiments and comparative examples are as follows: Total manganese was determined using a Loeb MD640 portable manganese analyzer. For sampling, 10 mL of water was taken, one packet of Vario ascorbic acid was added, followed by 15 drops of Vario alkaline cyanide reagent solution and 21 drops of Verio PAN indicator solution. After thorough mixing, the solution was placed in the instrument for zeroing. The water sample to be tested was then treated in the same manner and placed in the instrument for measurement.

[0059] The formula for calculating the Mn removal rate is: Mn removal rate = (Mn content in the raw water to be treated - Mn content in the treated water) / Mn content in the raw water to be treated × 100%.

[0060] The following examples and comparative examples use raw water from a water plant in the East District of Zhongshan City.

[0061] Example 1 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration is shown in the reaction flow diagram below. Figure 1 As shown, the specific steps are as follows: Step 1: Sample and test the raw water to be treated. Tests include pH, turbidity, color, and dissolved manganese ion concentration [Mn]. 2+ The PMS dosage was determined based on the manganese ion concentration. The raw water to be treated in this case had a pH of 7.12, a turbidity of 1.05, a color of 9, and a Mn content of 0.27 mg / L. The treatment temperature was 21℃.

[0062] Step 2: Construct a conventional coagulation and sedimentation unit for water treatment in a conventional water plant, establishing a complete coagulation and sedimentation process. The coagulation mixing tank operates at 200 r / min. Coagulant and pH adjuster are added. PAC (polyaluminum chloride) is selected as the coagulant at a dosage of 15 mg / L, and soda ash (Na₂CO₃) is selected as the pH adjuster at a dosage of 13.6 mg / L, stabilizing the pH in the coagulation tank between 6.9 and 7.1. Following the coagulation and sedimentation tank, a settling reaction tank, a quartz sand filter, and a disinfection device are connected sequentially before water supply.

[0063] Step 3: The raw water to be treated is passed into the coagulation and sedimentation device described above. After the coagulation and sedimentation process, PMS oxidant is added at a dosage of 2 mg / L (the mass ratio of PMS to the Mn content in the raw water to be treated is 7.4:1). Then, the ultraviolet lamp is turned on, and the flow rate is controlled according to the container volume to achieve 2 minutes of ultraviolet irradiation (254 nm wavelength) at a power of 500W (unless otherwise specified, the ultraviolet power used is 500W). Then, the water enters the settling reaction tank to undergo a complete reaction. The reaction time in the system is 30 minutes, and high-valence manganese oxide (MnO) is generated in the reaction tank. x ).

[0064] A PMS dosing point is set up after the coagulation sedimentation tank and before the settling reaction tank. After thorough mixing, the mixture is irradiated with a medium-pressure UV lamp. After UV irradiation, the mixture enters the settling reaction tank. After UV activation, the PMS reacts rapidly with Mn(II) in the raw water to generate a large amount of high-valence manganese oxides (MnO). x At this point, the color of the reaction tank will change significantly, and the water will turn yellowish. This phenomenon is caused by a large amount of small manganese oxide particles generated in the water. These small manganese oxide particles can also activate the PMS and promote the oxidation process to proceed further.

[0065] Step 4: The water from the reaction in step 3 is filtered from top to bottom through a quartz sand filter and the reaction continues. The quartz sand filter consists of the following layers from top to bottom: a filter media layer composed of a single quartz sand filter media with a thickness of 0.8 m, an effective particle size of 0.7~1.2 mm, and a uniformity coefficient ≤1.6; and a pebble cushion layer placed at the bottom with a thickness of 0.25 m. The filtration process uses gravity flow, and the filtration rate is monitored in real time, with the filtration speed controlled at 8.3 m / h.

[0066] In the initial stage of operation, dissolved manganese ions are oxidized by PMS to form manganese oxide, which is then loaded in situ onto the surface of the quartz sand, gradually forming a composite oxide film mainly composed of high-valence manganese oxides. This oxide film serves two purposes: firstly, it acts as a heterogeneous catalytic active site for PMS, continuously activating PMS to generate free radicals; secondly, it provides numerous adsorption and internal coordination sites for manganese ions, achieving highly efficient adsorption and capture of manganese. After the formation of this interfacial oxidation system, the manganese oxide film produced during the oxidation process further develops the system, thereby continuously improving the performance of the filter column and achieving better treatment results.

[0067] Figure 2 This is a diagram of the surface morphology of the quartz sand before the reaction. Figure 3 The image shows the surface morphology of the reacted quartz sand. Figures 2-3 The comparison also shows that the surface morphology of the quartz sand changed significantly after the reaction. EDS results indicate that after filtration, the manganese content on the surface of the quartz sand increased from 0% to approximately 14%, a significant increase that is a sign of a mature interfacial oxidation system.

[0068] Step 5: After filtration in step 4, the concentration of residual manganese ions in the water is measured. The effluent flows through pipes into the water treatment system of the water plant, continuously running the entire reaction process to restore the contaminated raw water in the water plant.

[0069] Example 2 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration differs from Example 1 in that the PMS dosage is changed to 0.5 mg / L, and some conditions are different, as shown in Table 1; otherwise, it is the same as Example 1.

[0070] Example 3 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration differs from Example 1 in that the conditions of the raw water to be treated are different in this example, as shown in Table 2; otherwise, it is the same as Example 1.

[0071] Example 4 A method for removing Mn metal pollutants using advanced oxidation-enhanced filtration differs from Example 1 in that the ultraviolet power is changed to 1000W and the conditions of the raw water to be treated are different, as shown in Table 2; otherwise, it is the same as Example 1.

[0072] Example 5 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration differs from Example 2 in that the conditions of the raw water to be treated are different in this example, as shown in Table 3; otherwise, it is the same as Example 2.

[0073] Example 6 A method for removing Mn metal pollutants using advanced oxidation-enhanced filtration differs from Example 2 in that the ultraviolet irradiation time is changed to 1 min, and the conditions of the raw water to be treated are different, as shown in Table 3; otherwise, it is the same as Example 2.

[0074] Example 7 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration differs from Example 1 in that the conditions of the raw water to be treated are different in this example, as shown in Table 4; otherwise, it is the same as Example 1.

[0075] Comparative Example 1 A method for removing Mn metal contaminants by filtration differs from Example 1 in that PMS oxidant is not added in this example, and the conditions of the raw water to be treated are different, as shown in Table 1; otherwise, it is the same as Example 1.

[0076] Comparative Example 2 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration differs from Example 1 in that ultraviolet irradiation is not used in this example, and some conditions are different, as shown in Table 1; otherwise, it is the same as Example 1.

[0077] Comparative Example 3 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration differs from Example 2 in that ultraviolet irradiation is not used in this example, and some conditions are different, as shown in Table 1; otherwise, it is the same as Example 2.

[0078] Comparative Example 4 A method for removing Mn metal contaminants using advanced oxidation-enhanced filtration differs from Example 1 in that potassium persulfate (PMS) is replaced with potassium perdisulfate (PDS), and the conditions of the raw water to be treated are different, as shown in Table 4; otherwise, it is the same as Example 1.

[0079] The Mn content before and after treatment in each embodiment and comparative example was detected, and the Mn removal rate was calculated.

[0080] Figure 4 This is a comparison chart of the manganese removal effects of Example 1 and Comparative Example 1; Figure 5 This is a comparison chart of the manganese removal effects of Example 2 and Comparative Example 1; Figure 6 This is a comparison chart of the manganese removal effects of Example 1 and Comparative Example 2; Figure 7 This is a comparison chart of the manganese removal effects of Example 2 and Comparative Example 3. In the chart, "2 mg / L PMS + UV" represents Example 1, "0.5 mg / L PMS + UV" represents Example 2, "UV irradiation only" represents Comparative Example 1, "2 mg / L PMS" represents Comparative Example 2, and "0.5 mg / L PMS" represents Comparative Example 3. Table 1 records the specific experimental data for Examples 1-2 and Comparative Examples 1-3.

[0081] From Table 1 and Figures 4-7 As can be seen, Examples 1-2 of this application all exhibited good removal effects on manganese under pH conditions close to 6.9-7.2. Under ultraviolet treatment, the removal rate reached 80% or higher. Combining this with high-concentration dosing resulted in even better removal, reaching up to 96% or higher. The turbidity and color after removal were within normal effluent levels, effectively meeting the requirements of water plants treating manganese-containing raw water. In Comparative Example 1, no oxidant was added, only ultraviolet irradiation was used; in Comparative Examples 2-3, only oxidant was added, but no ultraviolet irradiation was used, and the manganese removal effect decreased in both cases.

[0082] Table 1. Specific experimental data for Examples 1-2 and Comparative Examples 1-3

[0083] Figure 8 Table 2 shows a comparison of the manganese removal effects of Examples 3-4 and Comparative Example 1. Example 3 is described as "2 mg / L PMS + 500W UV", Example 4 as "2 mg / L PMS + 1000W UV", and Comparative Example 1 as "UV irradiation only". Table 2 records the specific experimental data for Examples 3-4. From Table 2 and... Figure 8 It is evident that there is no significant difference in processing efficiency between 500W and 1000W ultraviolet irradiation. Considering energy consumption and economy, 500W ultraviolet irradiation is superior.

[0084] Table 2 Specific experimental data for Examples 3-4

[0085] Figure 9 Table 3 shows a comparison of the manganese removal effects of Examples 5-6 and Comparative Example 1. Example 5 is described as "0.5 mg / L PMS + 2 min UV", Example 6 as "0.5 mg / L PMS + 1 min UV", and Comparative Example 1 as "UV irradiation only". Table 3 records the specific experimental data for Examples 5-6. From Table 3 and... Figure 9 It is evident that 2 minutes of UV irradiation can essentially ensure the reaction proceeds fully, increase the reaction rate, and achieve better manganese removal, especially under conditions of low dosage. Therefore, a 2-minute UV irradiation time is more effective, but a 1-minute UV irradiation time can also be used under high-concentration dosage conditions.

[0086] Table 3 Specific experimental data of Examples 5-6

[0087] Figure 10 Table 4 shows a comparison of the manganese removal effects of Example 7 and Comparative Examples 1 and 4. In the table, "2 mg / L PMS + UV" represents Example 7, "2 mg / L PDS + UV" represents Comparative Example 4, and "UV irradiation only" represents Comparative Example 1. Table 4 records the specific experimental data for Example 7 and Comparative Example 4. From Table 4 and... Figure 10 It is evident that using a combination of ultraviolet (UV) radiation and PMS can enhance the oxidizing capacity of PMS. The basic mechanism is as follows: UV irradiation breaks the peroxide bonds in PMS molecules, generating a large number of sulfate and hydroxyl radicals. This transforms the relatively mild PMS oxidant into more active free radicals, thereby increasing its oxidizing capacity for manganese (converting Mn(II) to Mn(III)). By setting up a UV device to irradiate the reaction system, the reaction rate can be increased, resulting in better removal efficiency.

[0088] In comparison, PDS (potassium persulfate) exhibits similar characteristics to PMS during treatment, namely, it does not produce residual chlorine pollution or secondary manganese pollution. However, studies have shown that the -OO- bonds in PDS are less active than the -OOH bonds in PMS, resulting in weaker oxidizing capacity. (Table 4 and...) Figure 10 Practical application results also show that PDS is less effective than PMS in removing manganese.

[0089] Table 4. Specific experimental data for Example 7 and Comparative Example 4

[0090] In this embodiment of the invention, a PMS-manganese oxide membrane coupling system is constructed in situ in a single quartz sand filter, which combines the functions of advanced PMS oxidation and heavy metal adsorption. Combined with the enhancement effect of ultraviolet (UV) irradiation on PMS oxidation, a manganese removal rate of ≥80% can be achieved without the addition of special adsorbents, and the manganese concentration, color and turbidity of the effluent are stably up to standard.

[0091] The process flow of this invention is basically the same as the conventional water treatment plant's "pre-oxidation before filtration, coagulation, and quartz sand filtration" method. In practical applications, it is only necessary to change the original pre-oxidant to PMS and modify the addition site, or add it directly after the coagulation tank on the basis of the original pre-oxidation process. Only the ultraviolet treatment-related equipment and processes need to be added. There is no need to further modify the filter media. The amount of modification work is small and it is easy to promote in existing projects.

[0092] The process in this invention does not use complexing agents or complex catalysts containing heavy metals, thus avoiding the risks of secondary pollution from permanganate and residual chlorine, as well as complex oxidants. It also avoids the process modifications and cost increases caused by the addition of complex drugs.

[0093] In summary, this invention employs a coupling method of persulfate, ultraviolet irradiation, and quartz sand filtration, which can transform the originally mild persulfate into a more active oxidation system, achieving efficient oxidation of manganese pollutants. The required treatment time is short, and deep removal of low-concentration manganese pollutants from raw water can be achieved without the addition of complexing agents, the use of expensive special adsorbents, or complex filter media.

Claims

1. A method for removing metallic contaminants using advanced oxidation-enhanced filtration, characterized in that, Includes the following steps: The raw water containing manganese pollutants is mixed with persulfate and subjected to ultraviolet irradiation to undergo an oxidation reaction, resulting in oxidized water. The oxidized water is then filtered through quartz sand to remove the manganese pollutants, resulting in purified water.

2. The method according to claim 1, characterized in that, The mass ratio of the persulfate to the manganese content in the raw water to be treated is (1~15):

1.

3. The method according to claim 1, characterized in that, The manganese content in the raw water to be treated is 0.05~0.5 mg / L; And / or, the pH value of the raw water to be treated is 6.8~7.3; And / or, the manganese content in the purified water is ≤0.1mg / L.

4. The method according to claim 1, characterized in that, The power of the ultraviolet irradiation is 300~1200W; And / or, the ultraviolet irradiation time is 0.5~5 min.

5. The method according to claim 1, characterized in that, The oxidation reaction takes 20-40 minutes.

6. The method according to claim 1, characterized in that, The filtration speed is 6~10m / h; And / or, the quartz sand has a particle size of 0.7~1.2mm and a uniformity coefficient ≤1.6; And / or, the thickness of the filter layer formed by the quartz sand is 0.6~1m.

7. The method according to claim 1, characterized in that, Before the raw water to be treated is mixed with persulfate, it also includes a coagulation and sedimentation treatment; the reagents used in the coagulation and sedimentation treatment include pH adjusters. The pH adjuster includes at least one of sodium carbonate, potassium carbonate, or ammonium carbonate; and / or, the dosage of the pH adjuster is 10-20 mg / L.

8. The method according to claim 7, characterized in that, The reagents used in the coagulation and sedimentation treatment also include coagulants; The coagulant includes at least one of polyaluminum chloride, polyaluminum sulfate, polyferric chloride, or polyferric sulfate; and / or, the dosage of the coagulant is 10~20 mg / L.

9. An apparatus for removing metal contaminants using advanced oxidation-enhanced filtration, characterized in that, It includes a static reaction tank and a quartz sand filter connected in sequence; the static reaction tank is equipped with a water inlet, an oxidant dosing port and an ultraviolet device; the water inlet is used to introduce raw water containing manganese pollutants; the oxidant dosing port is used to add persulfate; the ultraviolet device is used to irradiate the water with ultraviolet light.

10. The apparatus according to claim 9, characterized in that, The settling reaction tank is also connected to the coagulation sedimentation tank; the coagulation sedimentation tank is equipped with a pH adjuster dosing port; optionally, the coagulation sedimentation tank is also equipped with a coagulant dosing port.

Images