A fortified defluoridation matrix, constructed wetland system and method

Abstract

The application provides a fluorine removal enhanced substrate, an artificial wetland system and a method, and relates to the technical field of ecological water treatment.The fluorine removal enhanced substrate comprises a magnesium-carbon particle mixture, and the magnesium-carbon particle mixture comprises magnesium particles and metal-modified biochar particles.The application can improve the fluorine removal efficiency of the artificial wetland system.

Description

Technical Field

[0001] This invention relates to the field of ecological water treatment technology, specifically to an enhanced fluoride removal matrix, an artificial wetland system, and a method. Background Technology

[0002] Fluoride is a significant anionic pollutant in water bodies, widely present in them. Excessive fluoride intake can lead to pathological changes in teeth and bones, such as dental fluorosis and skeletal fluorosis, and even cause thyroid disorders, brain damage, and cancer. Current water fluoride removal technologies mainly include precipitation, membrane separation, adsorption, ion exchange, and electrochemical methods. While these technologies can effectively remove fluoride pollution from water bodies, they also have drawbacks such as high cost, complex operation and maintenance, and unstable removal efficiency, making large-scale application in watershed environments difficult.

[0003] Constructed wetlands (CWs), as a green water treatment technology that simulates natural wetlands, utilize complex physical, chemical, and biological mechanisms, including adsorption, sedimentation, filtration, redox reactions, and decomposition and transformation by plants and microorganisms, to remove pollutants from water bodies and improve water quality. They offer advantages such as low investment, low operating costs, and stable results. Currently, most CW applications focus on the removal of organic matter, nitrogen, and phosphates, lacking targeted measures for the removal of high concentrations of fluoride.

[0004] The substrate is a major factor affecting fluoride removal in constructed wetlands. Improving the substrate's adsorption capacity can enhance the fluoride removal efficiency. Micro-electrolysis technology possesses a certain fluoride removal capability, and applying it to the substrate of constructed wetland systems is a feasible method to improve fluoride removal efficiency. Traditional micro-electrolysis fluoride removal technology primarily uses iron-carbon micro-electrolysis. Iron hydroxide, formed by iron hydrolysis, complexes with fluorides to form complexes that are difficult to dissociate. Further removal of fluorides is achieved through adsorption and precipitation. However, during the complex formation process, the low adsorption capacity of iron hydroxide leads to the consumption of large amounts of iron material for fluoride adsorption. Furthermore, iron hydroxide is prone to caking, causing effluent blockage, which has become a major challenge restricting the efficient coupling of micro-electrolysis with constructed wetlands. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an enhanced defluorination substrate, an artificial wetland system, and a method to improve the defluorination efficiency of artificial wetland systems.

[0006] To achieve the above objectives, according to some embodiments, a first aspect of the present invention provides an enhanced defluorination matrix comprising a magnesium-carbon particle mixture, said magnesium-carbon particle mixture comprising magnesium particles and metal-modified biochar particles.

[0007] A second aspect of the present invention provides an enhanced fluoride removal constructed wetland system, wherein the constructed wetland system is filled with an enhanced fluoride removal matrix provided in the first aspect.

[0008] A third aspect of the present invention provides an enhanced defluorination method, comprising: constructing an enhanced defluorination constructed wetland system as provided in the second aspect above; and adopting a continuous flow inlet and outlet method, wherein fluoride-containing wastewater enters the constructed wetland system through the inlet and flows out through the outlet.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[0010] This invention provides an enhanced defluorination matrix, constructed wetland system, and method. A magnesium-carbon microelectrolysis system is used for defluorination, with metal-modified biochar serving as the negative electrode. Magnesium has better metallic activity than iron, and its redox potential is much lower than iron, exhibiting stronger reducing power and electron transfer intensity, ensuring the feasibility of the magnesium-carbon microelectrolysis system. Studies have shown that metal-modified biochars such as Fe / Al / La / Mn have high adsorption capacity for fluorides and can increase the electrode potential difference between magnesium and carbon. Iron-modified biochar has gained favor among researchers due to its simple preparation, inexpensive raw materials, abundant oxygen-containing functional groups, and stable performance. The modified biochar, with its rich pore structure, can enhance the adsorption-co-precipitation effect of fluorides and effectively increase the electrode potential. Adding magnesium-carbon microelectrolysis materials to the constructed wetland matrix... 2+ and F - The specific binding of these molecules generates precipitates and crystals. These precipitates are not easily accumulated and can be continuously flushed out by the water flow. This invention effectively improves the electrode potential difference between the micro-electrolysis cells, solves the problems of poor ion migration and low reaction rate, enhances the defluorination capacity of constructed wetland systems using magnesium-carbon micro-electrolysis systems, and provides a technical reference for the wasteless electrochemical enhancement of constructed wetland treatment of fluoride-containing wastewater.

[0011] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0013] Figure 1 SEM image of iron-modified biochar;

[0014] Figure 2 This is a schematic diagram of an artificial wetland system. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Constructed wetlands treat fluoride-containing wastewater primarily through matrix adsorption, co-precipitation, and ion exchange. Traditional constructed wetlands mainly focus on removing organic matter, nitrogen, and phosphates, lacking specific measures for high concentrations of fluoride. The introduction of micro-electrolysis technology has enhanced the removal efficiency of fluoride-containing wastewater in constructed wetlands; however, traditional iron-carbon micro-electrolysis systems coupled with constructed wetlands exhibit poor adsorption of fluoride in wastewater and are prone to clogging of the effluent.

[0017] Therefore, this invention proposes to use a magnesium-carbon microelectrolysis system for fluoride removal, and to replace the negative electrode in the system with metal-modified biochar to effectively enhance the fluoride removal capacity. In some embodiments, an enhanced fluoride removal matrix is ​​first provided, comprising a magnesium-carbon particle mixture, wherein the magnesium-carbon particle mixture includes magnesium particles and metal-modified biochar particles, and the metal-modified biochar is preferably iron-modified biochar.

[0018] Compared to the iron-carbon microelectrolysis system, the magnesium-carbon density difference is smaller, resulting in higher galvanic cell reaction efficiency. - With Mg 2+ It can form insoluble MgF2 and thus be removed; magnesium has better metallic activity than iron, and its redox potential is much lower than that of iron (E0(Mg)). 2+ / Mg)=-2.372V,E0(Fe 2+ Magnesium (Fe) = -0.44V exhibits stronger reducing power and electron transfer intensity, thus providing a stronger driving force for electron transfer. Furthermore, magnesium's passivation degree is lower than that of iron. Therefore, this invention proposes using a magnesium-carbon microelectrolysis system for fluoride removal, which significantly enhances the fluoride removal capability compared to existing iron-carbon microelectrolysis systems.

[0019] Biochar possesses abundant pore structure and specific surface area, but its surface alkalinity and negative charge greatly limit its adsorption efficiency for anionic pollutants such as fluorides. Metal-modified biochar enhances the adsorption-co-precipitation effect of fluorides. Simultaneously, it improves the stability of biochar in redox reactions, exhibiting excellent electrocatalytic activity. Furthermore, magnesium particles, upon dissolving in water, can rapidly generate a large amount of Mg. 2+ , with F - The formation of MgF2 crystals precipitates enables the adsorption of fluorides. By using metal-modified biochar as the negative electrode in magnesium-carbon micro-electrolysis, the electrode potential difference between the micro-electrolysis cells is effectively increased, solving the problems of poor ion migration and low reaction rate. This enhances the fluoride removal capability.

[0020] Preferably, the metal-modified biochar is iron-modified biochar, such as... Figure 1As shown, the magnesium-carbon microelectrolysis filler is composed of a mixture of magnesium particles and iron-modified biochar particles. Furthermore, literature has demonstrated that modification with transition metals such as iron, cobalt, and nickel helps improve the catalytic redox reaction capability of biochar. Therefore, other transition metal-modified biochars, based on the same mechanism, can also be used in the defluorination scenario of this patent.

[0021] The enhanced fluoride removal matrix is ​​obtained by uniformly mixing quartz sand and magnesium carbon micro-electrolysis filler, and then used to fill the constructed wetland system.

[0022] Based on the enhanced defluorination matrix provided above, some embodiments further provide an enhanced defluorination constructed wetland system, which is filled with an enhanced defluorination matrix obtained by mixing quartz sand and magnesium carbon micro-electrolysis filler.

[0023] Specifically, such as Figure 2 As shown, the constructed wetland system is set up in a vertical flow constructed wetland device, using a cylindrical PVC device with a diameter of 150mm and a height of 550mm. From top to bottom, it includes wetland plants and a filler substrate. The filler substrate is layered, consisting of an upper layer of quartz sand and a lower layer of gravel. The quartz sand layer is filled with a reinforced fluoride-removing substrate, and the gravel layer is filled with pebbles. The substrate is filled from bottom to top: 0-5cm is filled with pebbles with a particle size of 2-4cm; 5-40cm is filled with quartz sand and magnesium-carbon micro-electrolysis filler with a particle size of 2-4mm. The magnesium-carbon micro-electrolysis filler is a mixture of magnesium particles and iron-modified biochar particles. Before filling, the magnesium particles, biochar particles, and quartz sand are mixed evenly. The wetland plants selected are healthy, uniformly sized *Iris tectorum*, planted at a density of 180 plants / m². 2 This translates to 3 plants per device. The device operates with a continuous flow of water, with water entering from the top and exiting from the bottom. The water enters through a quartz sand layer and a gravel layer in sequence, and the purified water is discharged through a drain pipe. A peristaltic pump controls the flow rate, and the hydraulic retention time is set to 5 days.

[0024] To facilitate in-situ measurement of physicochemical parameters and timely monitoring of wetland conditions, a measuring tube (PVC pipe, 50mm in diameter) with uniform perforations is vertically inserted in the middle of the constructed wetland system.

[0025] In some embodiments, an enhanced fluoride removal method based on the constructed wetland system is further provided, including:

[0026] Construct the above-mentioned enhanced fluoride removal constructed wetland system; fill the substrate from bottom to top, fill the 0-5cm layer with sand and gravel (pebbles), fill the 5-40cm layer with quartz sand (enhanced fluoride removal substrate), and then plant the healthy and uniformly sized yellow iris on the substrate;

[0027] The system adopts a continuous flow inlet and outlet method. Fluoride-containing wastewater enters the constructed wetland system through the inlet and flows out through the outlet. The device operates in a continuous flow inlet and outlet mode, with the inlet located at the top and the outlet at the bottom. The inlet and outlet are preferably located on both sides of the device. A peristaltic pump is used to control the wastewater flow rate, and the hydraulic retention time is set to 5 days.

[0028] The constructed wetland system provided by this invention can improve the fluoride removal efficiency to over 80%. The effectiveness of this invention is illustrated below with reference to embodiments and comparative examples.

[0029] Example

[0030] An enhanced fluoride removal constructed wetland system employs a continuous flow inlet and outlet water system. It includes wetland plants and a substrate filler. The substrate filler is arranged from bottom to top: 0-5cm is filled with pebbles with a particle size of 2-4cm, and 5-40cm is filled with an enhanced fluoride removal substrate (quartz sand with a particle size of 2-4mm and magnesium-carbon micro-electrolysis filler). The magnesium-carbon micro-electrolysis filler is a mixture of magnesium particles and iron-modified biochar particles. The magnesium particles have a particle size of 200-800mm, and the iron-modified biochar particles have a particle size of 0.5-2mm and a pore size of 2-6nm.

[0031] Comparative Example

[0032] To determine that iron-modified biochar is the optimal solution in magnesium-carbon microelectrolysis materials, two additional artificial wetland systems with different matrices were set up for comparison.

[0033] The two constructed wetland systems are as follows:

[0034] Constructed wetland A: The 0-5cm section is filled with pebbles with a particle size of 2-4cm, and the 5-40cm section is filled with quartz sand with a particle size of 2-4mm and magnesium-carbon micro-electrolysis filler. The magnesium-carbon micro-electrolysis filler is made of a mixture of magnesium particles and unmodified biochar particles.

[0035] Artificial wetland B: Fill the 0-40cm space with 2-4mm of quartz sand.

[0036] Except for the different filler material, the construction of the artificial wetland described above is consistent with that of the embodiment.

[0037] The constructed wetland systems of the embodiments and comparative examples were operated under the following conditions:

[0038] The constructed wetland operates using a continuous flow inlet / outlet system, with water entering from the top and exiting from the bottom. A peristaltic pump controls the flow rate, and the hydraulic retention time is set to 5 days. The influent includes: COD [50 mg / L] and NH4+. + -N [5 mg / N], total phosphorus [0.5 mg P / L] and NO3 --N [10 mg N / L]; in addition, the initial fluoride ion concentration is set at 20 mg / L. A biofilm is attached before operation, aerobic activated sludge is added, and MLSS (mixed liquor suspended solids) is controlled at 50 mg / L. The plants and microorganisms in the system are acclimatized for 30 days. The effluent contains COD (chemical oxygen demand), TP (total phosphorus), TN (total nitrogen), and NH4+. + -N and NO3 - The experiment was started after the -N removal performance stabilized. Two parallel water samples were set up and maintained at room temperature (25±2℃) and relative humidity of about 70%. The expected experiment period was 120 days.

[0039] The experimental results are shown in Table 1. The constructed wetland system with added magnesium and iron-modified biochar particles exhibited the highest fluoride removal rate in the examples, demonstrating that this invention enhances the fluoride removal capacity of traditional constructed wetlands. Furthermore, the experimental results show that the introduction of transition metals onto the biochar surface can increase the number and diversity of active sites, which helps improve the adsorption capacity and catalytic activity of biochar. Transition metal-modified biochar increases the specific surface area and surface functional groups of the original biochar while attaching metal cations to the surface, enhancing the adsorption of anionic pollutants in water. Transition metals typically possess excellent catalytic properties, promoting chemical reactions on the biochar surface. This catalytic activity can improve the adsorption performance of biochar, catalytically degrade organic pollutants, and thus enhance its overall performance.

[0040] Table 1 Fluoride removal rates of different constructed wetland systems

[0041]

[0042] It should be noted that this invention only selected the above-mentioned wastewater quality as an example to verify the characteristics of the constructed wetland system constructed by this invention in enhancing fluoride removal. However, in actual applications, the water quality that the constructed wetland system disclosed in this invention can treat is not limited to this.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fortified defluoridation constructed wetland system characterized in that, The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles.

2. The enhanced defluoridation constructed wetland system as claimed in claim 1, wherein, The artificial wetland system comprises wetland plants and filler substrate from top to bottom, wherein the filler substrate comprises a quartz sand layer and a sandstone layer, and the quartz sand layer is filled with the reinforced fluoride removal substrate.

3. The enhanced defluoridation constructed wetland system as claimed in claim 2, wherein, The artificial wetland system further comprises an inlet and an outlet, wherein the inlet is located at the quartz sand layer, the outlet is located at the sandstone layer, and the inlet and the outlet are arranged on both sides of the artificial wetland system.

4. The enhanced defluoridation constructed wetland system of claim 1, wherein, The artificial wetland system further comprises a measuring tube, which is vertically arranged in the middle of the artificial wetland system.

5. A method of enhanced defluoridation characterized by, The artificial wetland system comprises: The artificial wetland system comprises: The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles.

6. The enhanced defluoridation method as claimed in claim 5, wherein, The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified biochar particles. The artificial wetland system is filled with a reinforced fluoride removal substrate, which is uniformly mixed by quartz sand, magnesium particles and metal modified

Images