A wastewater treatment system and method based on droplet impingement

Abstract

The application discloses a wastewater treatment system and method based on droplet impact, which comprises a wastewater pool, a droplet impact reactor and a recovery pool connected in sequence, wherein the droplet impact reactor comprises a droplet releasing device and a droplet reaction device; the droplet releasing device is made of conductive material and is used for releasing input wastewater in the form of droplets; the droplet reaction device is made of dielectric material, the surface of the droplet reaction device is super-hydrophobic, and the droplet reaction device is arranged obliquely below the droplet releasing device and is used for enabling the droplets released by the droplet releasing device to drop on the surface of the droplet reaction device to complete the impact and sliding process. The application can completely degrade organic waste, recover pure metal without reagent, and provide technical support for environmental governance and resource recovery.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, and in particular to a wastewater treatment system and method based on droplet impaction. Background Technology

[0002] Water resources are the cornerstone of maintaining ecological balance and human societal development. However, with the rapid development of industries such as dyeing, textiles, and electroplating, large quantities of wastewater containing high concentrations of organic dyes (such as crystal violet and methylene blue) and heavy / precious metal ions are being discharged, posing a serious challenge to global water quality and human health. Organic pollutants that are difficult to degrade in natural water bodies are not only ecotoxicological but also often coexist with pathogenic bacteria such as E. coli, further exacerbating the biosafety risks to aquatic bodies.

[0003] Currently, advanced oxidation processes (AOPs) are widely used in the deep treatment of organic wastewater. AOPs primarily rely on generating reactive oxygen species (ROS, such as hydroxyl radicals ·OH) with extremely high redox potentials to non-selectively attack and thoroughly mineralize organic pollutants. However, traditional AOPs technologies still have significant limitations and defects. Specifically, whether it is photocatalysis, electrocatalysis, or ultrasonic catalysis, all heavily depend on the continuous input of external energy (such as ultraviolet light sources or high-voltage electricity). In addition, traditional oxidation methods that rely on chemical reagents (such as ozone, hydrogen peroxide, or chlorine) are not only costly to operate, but also easily generate secondary byproducts with carcinogenic risks in complex water bodies.

[0004] On the other hand, the recovery of precious metal ions from wastewater and the synthesis of nanocrystals also face technical bottlenecks. Traditional colloidal chemical synthesis methods and metal recovery processes require the addition of various surfactants and chemical reducing agents. These chemicals irreversibly bind to the surface of metal nanocrystals, making them difficult to remove completely through conventional cleaning. Surface contamination not only hinders the clean recovery of precious metal resources, but more critically, it severely shields the active sites on the metal surface, leading to a significant performance degradation in subsequent high-value applications (such as surface-enhanced Raman spectroscopy (SERS) detection and precision catalysis). This represents a fundamental contradiction in traditional synthesis techniques: the inability to simultaneously achieve high product dispersion stability and absolute surface cleanliness. Summary of the Invention

[0005] The purpose of this invention is to provide a wastewater treatment system and method based on droplet impaction.

[0006] The technical solution of the present invention is as follows: On the one hand, a wastewater treatment system based on droplet impact is provided, comprising a wastewater tank, a droplet impact reactor, and a recovery tank connected in sequence, wherein the droplet impact reactor includes a droplet release device and a droplet reaction device; The droplet release device is made of conductive material and is used to release the input wastewater in the form of droplets; the droplet reaction device is made of dielectric material and has a superhydrophobic surface. The droplet reaction device is tilted below the droplet release device so that the droplets released by the droplet release device can fall onto the surface of the droplet reaction device to complete the impact and sliding process.

[0007] Preferably, the droplet release device has multiple droplet release ends, and the multiple droplet release ends are arranged in an array.

[0008] Preferably, the conductive material also has corrosion resistance.

[0009] Preferably, the droplet size released by the droplet release device is 8-18 μL.

[0010] Preferably, the relative permittivity of the dielectric material is less than 10.

[0011] Preferably, the droplet reaction device is tilted at an angle of 60°.

[0012] Preferably, the droplet reaction device is located below the droplet release device to achieve a Weber number of 50-100.

[0013] Preferably, a circulation pump is provided between the recovery tank and the input end of the droplet impact reactor. The droplet impact reactor also includes a grounding connection switch, which is connected to the droplet release device to enable the droplet release device to be grounded.

[0014] Preferably, when recovering metals from wastewater, the grounding switch is turned on to ground the droplet release device; when treating organic matter in wastewater, the grounding switch is turned off to levitate the droplet release device.

[0015] On the other hand, a wastewater treatment method based on droplet impact is also provided, which uses the wastewater treatment system based on droplet impact described in any one of the above-mentioned methods for treatment.

[0016] The beneficial effects of this invention are: 1. This invention is a green, zero-reagent solution that eliminates secondary pollution: it completely eliminates the use of chemical oxidants (such as H2O2 and O3) in traditional wastewater treatment and chemical reducing agents in traditional metal recycling. This not only avoids secondary pollution but also results in extremely clean surfaces for the precious metals produced during reduction, significantly enhancing their value for subsequent resource utilization.

[0017] 2. This invention converts simple mechanical energy into chemical energy: the system does not require a high-voltage power supply, ultrasonic generator or strong light source to directly convert the mechanical energy (fluid kinetic energy) that drives fluid circulation into the chemical energy that drives oxidation-reduction reaction.

[0018] 3. This invention is scalable: Further employing a closed-loop circuit and multi-point drip array design, this invention possesses high scalability. The system exhibits extremely strong anti-interference capabilities, maintaining over 75% reactivity even in complex aquatic substrates such as tap water or lake water. Attached Figure Description 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, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the wastewater treatment system based on droplet impaction according to the present invention. Figure 2 This is a schematic diagram of the wastewater treatment system based on droplet impaction of the present invention in a specific embodiment; Figure 3 This is a schematic diagram showing the effect of precious metal recovery and organic waste liquid treatment in Example 1; Figure 4 This is a schematic diagram of the noble metal reduction and dye degradation process with different parameters in Example 2. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0021] On the one hand, such as Figure 1 As shown, the present invention provides a wastewater treatment system based on droplet impact, comprising a wastewater tank, a droplet impact reactor, and a recovery tank connected in sequence, wherein the droplet impact reactor includes a droplet release device and a droplet reaction device; The droplet release device is made of conductive material and is used to release the input wastewater in the form of droplets; the droplet reaction device is made of dielectric material and has a superhydrophobic surface. The droplet reaction device is tilted below the droplet release device so that the droplets released by the droplet release device can fall onto the surface of the droplet reaction device to complete the impact and sliding process.

[0022] In this invention, wastewater is treated by droplet impact, where the dynamic contact and separation of the droplets with the dielectric material surface spontaneously induces intense interfacial electron transfer. Specifically, this invention employs a droplet reaction device with a superhydrophobic surface made of dielectric material, possessing extremely low surface energy. Due to this superhydrophobic property, fluid droplets rapidly bounce and detach after impacting the surface, exhibiting minimal solid-liquid contact adhesion and contact area. This brief but intense dynamic contact-separation process not only ensures the material surface's anti-fouling properties and long-term self-cleaning, but also induces highly directional charge transfer between interfaces due to the strong electron affinity of the dielectric material. This high-energy charge transfer at the microscopic interface generates reactive oxygen species that degrade organic matter and reduce metal ions in situ, thereby achieving the purpose of wastewater treatment.

[0023] When using this invention, the droplet reaction device can autonomously and continuously drive electron transfer at the solid-liquid interface using only fluid kinetic energy, without requiring external high-energy input. By precisely controlling the charge direction through droplet impact on the dielectric superhydrophobic material and grounding, highly efficient oxidation with self-supplied active oxygen and highly efficient reduction with self-supplied electrons can be flexibly achieved at the microscopic interface. This invention integrates highly efficient advanced oxidative degradation of organic pollutants, broad-spectrum sterilization, and reagent-free reduction and recovery of metals into a single physical driving system, completely eliminating the dependence on chemical oxidants, reducing agents, and surfactants in traditional processes, thus eliminating secondary pollution problems caused by chemical byproducts and metal surface deactivation problems at the source.

[0024] In one specific embodiment, the droplet release device has multiple droplet release ends, and the multiple droplet release ends are arranged in an array. Optionally, the multiple droplet release ends are arranged in a 15×15mm matrix. In this embodiment, by setting multiple droplet release ends, the wastewater treatment efficiency can be accelerated.

[0025] In one specific embodiment, the conductive material also has corrosion resistance. When the wastewater to be treated is a metal waste liquid, the metal ion solution has a certain oxidizing property, and the droplet release device made of a conductive material with corrosion resistance can extend its service life.

[0026] In one specific embodiment, the droplet release device releases droplets with a size of 8-18 μL. In this invention, different droplet sizes result in different amounts of electrostatic charge generated upon impact. Adjusting the droplet size can regulate the amount of electrostatic charge, thereby adjusting the reaction progress. It should be noted that larger droplets are not necessarily better. At an impact height of 10 cm, a droplet size of 18 μL generates the highest amount of electrostatic charge (approximately 1.5 nanocoulombs / drop). When the droplet size exceeds 18 μL, the droplet becomes too large to maintain complete wetting of the superhydrophobic surface, leading to reduced charge generation and uncontrollable reaction progress.

[0027] In one specific embodiment, the relative permittivity of the dielectric material is less than 10. It should be noted that dielectric materials with superhydrophobic surfaces (such as perfluorooctyltrichlorosilane-modified silica / carbon composite coatings or polytetrafluoroethylene coatings, superhydrophobic polytetrafluoroethylene, superhydrophobic fluorinated ethylene propylene copolymers, superhydrophobic polyvinylidene fluoride, etc.) are all applicable to this invention; however, the reaction process and rate differ slightly depending on the dielectric properties of the material.

[0028] In one specific embodiment, the tilt angle of the droplet reaction device is 60°. In this invention, when the tilt angle of the droplet reaction device is too large, the droplets tend to wet the interface and slide down, resulting in a smaller amount of charge; when the tilt angle is too small, the droplets will be broken when they hit the surface of the droplet reaction device, thus generating many small droplets and reducing its controllability. The angle used in this embodiment is the preferred tilt angle of this invention, considering factors such as charge amount and controllability.

[0029] In one specific embodiment, the droplet reaction device is located below the droplet release device at a position where the Weber number (We) reaches 50-100. Optionally, when the droplet released by the droplet release device is 18 μL, the We value at a position 10 cm below the droplet release device is 59; and the We value at a position 15 cm below is 88.

[0030] It should be noted that the Weber number is a more physically meaningful expression of the impact height. The Weber number is related to droplet size and velocity; when the droplet size is constant, the Weber number is essentially the height. Adjusting the impact height allows for control of fluid dynamics and optimization of charge transfer efficiency in a single impact. The Weber number in this embodiment is a preferred parameter of the invention; other Weber numbers can be selected based on the target efficiency when using this invention. It should also be noted that, in addition to adjusting the Weber number, the reaction rate can be maximized by adjusting the flow rate of the droplet release device to balance the charge generation and dissipation rates.

[0031] In one specific embodiment, a circulation pump is further provided between the recovery tank and the input end of the droplet impact reactor. The droplet impact reactor also includes a grounding connection switch, which is connected to the droplet release device to enable the droplet release device to be grounded. Optionally, the output end of the circulation pump and the output end of the input pump are connected to the input end of the droplet impact reactor through a mixer.

[0032] In the above embodiments, a circulation pump is installed to circulate the wastewater, preventing incomplete treatment in a single pass. Mixing the liquid from the recovery tank and the wastewater tank using a mixer reduces the wastewater concentration and improves treatment efficiency.

[0033] In one specific embodiment, when recovering metals from wastewater, the grounding switch is turned on to ground the droplet release device; when treating organic matter in wastewater, the grounding switch is turned off to levitate the droplet release device.

[0034] In the above embodiments, grounding during metal recovery ensures that the circulating droplets are electrically neutral. Without grounding, the circulating droplets carry positive charges from previous impacts, hindering the continued generation of positive and negative charges. This reduces the charge density of the superhydrophobic surface, thereby decreasing the metal reduction rate. Floating during organic matter processing prevents the grounding process from neutralizing previously accumulated positive charges during droplet circulation, thus preventing effective positive charge accumulation and reducing the rate of organic matter oxidation.

[0035] It should be noted that for complex wastewater containing both organic matter and metals, the high-energy free radical solution generated by oxidation and the pure metal nanocrystals generated by reduction can be collected separately by switching the grounding state of the droplet release device or by connecting two droplet release devices in series.

[0036] In addition, when using this invention, the catalytic performance and recovery efficiency of the system can be adjusted by optimizing the Weber number, droplet impact frequency, impact array area, and controlling charge dissipation conditions (such as settling time and flow rate) to break the charge saturation limitation at the solid-liquid interface.

[0037] On the other hand, the present invention also provides a wastewater treatment method based on droplet impaction, wherein the wastewater is treated using any of the above-described wastewater treatment systems based on droplet impaction.

[0038] In this invention, when treating wastewater containing organic pollutants (such as methylene blue, rhodamine B, basic fuchsin, basic brown, basic orange 2, and pathogens) using the droplet impaction-based wastewater treatment method described herein, the released droplets are electrically neutral, and the surface of the droplet reaction device is uncharged. After the droplets impact the droplet reaction device, due to the difference in electron affinity, the rebounding droplets carry a positive charge, and the superhydrophobic surface of the droplet reaction device carries a negative charge. High-energy interfacial electron exchange triggers the oxidation of water molecules, continuously generating hydroxyl radicals (•OH) and superoxide anions (•O2). - ) and singlet oxygen ( 1 Reactive oxygen species (ROS) such as O2 attack electron-rich functional groups in organic pollutant molecules like dyes, degrading them into smaller molecules like carbon dioxide and water. Simultaneously, they inactivate bacteria by damaging their cell membranes and DNA, such as those of Escherichia coli and Staphylococcus aureus. The reaction follows pseudo-first-order kinetics: ln(C0 / C2) t ) = kt, where C0 is the initial concentration of the sample; C t t represents the current concentration of the product; k is the reaction rate constant; and t is the reaction time.

[0039] The wastewater treatment method based on droplet impaction described in this invention is used to treat wastewater containing metal ions (such as Au). 3+ Ag + Pt 4+ When releasing wastewater containing precious metal ions, the droplet release device is grounded, and the released droplets are electrically neutral, with the surface of the droplet reaction device being uncharged. After a droplet impacts the droplet reaction device, the rebounding droplet carries a positive charge, and the superhydrophobic surface of the droplet reaction device carries a negative charge. This negative charge accumulates continuously on the superhydrophobic surface of the droplet reaction device. When the surface negative charge density of the droplet reaction device is sufficiently high (approximately -3 nC / cm³),... 2 (Above), electrons are transferred from the surface to the next impacting droplet, triggering a reduction reaction of metal ions (such as HAuCl4) within the droplet, transforming them into zero-valent metal nanocrystals.

[0040] Example 1 Wastewater is treated using the droplet impaction-based wastewater treatment method described in this invention. In this embodiment, the droplet impaction-based wastewater treatment system is as follows: Figure 2 As shown. Figure 2In this system, the sample tank stores the sample to be processed. A liquid guide tube connected via a liquid guide hole controls the flow rate to the metal needle position (droplet release device) with a needle insertion hole. If processing a metal sample, the metal needle is grounded at this point. The droplets are then expelled through the metal needle and fall onto the droplet reaction device attached to the sample holder. The sample holder's height can be adjusted to regulate the impact height. After impact, the liquid enters the bottom recovery tank, and then is circulated through a peristaltic pump via a return conduit, repeating the process.

[0041] In this embodiment, the effects of precious metal recovery and organic wastewater treatment are as follows: Figure 3 As shown. During the experiment, the impact height was 10 cm, the impact frequency was 1 drop per second, the impact mode used was a single needle impact mode, and the impact area was 12 × 24 mm. The raw materials used for precious metal recovery were 1 M HAuCl4 solution, 0.05 M silver nitrate solution, and 0.05 M potassium tetrachloroplatinate solution. The raw material used for organic waste liquid was 10 ppm methylene blue solution. The metal needle was grounded during precious metal recovery. The droplet reaction device used a micron-sized silica microstructure glass sheet deposited by the candle ash method. A superhydrophobic glass sheet of PFOTS material was vapor-deposited using a vacuum desiccator in a laboratory environment.

[0042] from Figure 3 It can be seen that as the reaction time increases, the color of the metal solution gradually deepens, and the metal is gradually reduced; as the reaction time increases, the color of the methylene blue solution gradually lightens, and the methylene blue is gradually oxidized and degraded.

[0043] Example 2 In this embodiment, the reduction of noble metals and the degradation of dyes under different parameters were studied, and the results are as follows: Figure 4 As shown in the figure. In this embodiment, the parameters used are the same as those in Example 1, except that a single variable is varied. Specifically: a is the reduction concentration of chloroauric acid at different impact times; b is the reduction concentration of chloroauric acid at different impact areas; c is the concentration of chloroauric acid reduced at different Weber numbers; d is the concentration change of methylene blue at different impact frequencies; e is the concentration change of methylene blue at different areas; and f is the concentration change of methylene blue at different flow rates.

[0044] from Figure 4It can be seen that the reaction rate of metal reduction is faster when the impact frequency is between 1-3 drops per second. Excessive frequency will affect the impact process due to the formation of liquid flow, thus reducing efficiency. The reaction rate is better at impact areas of 6×12 mm and 9×18 mm. Too small an area will affect the size of the region where impact charge is generated, while too large an area will cause excessive charge dissipation, resulting in a very low equilibrium charge. A Weber number (We) of 59-88.5 (10-15 cm) yields better results; higher numbers will cause droplets to break up, while smaller numbers result in very low charge generation. Four drops are most effective in the methylene blue treatment process because the oxidation end does not need to consider droplet morphology excessively; maintaining positive charge generation is sufficient. A medium area of ​​15×15 mm maintains the best charge density, resulting in the optimal rate. A stable flow rate (68 mL / min) ensures both charge generation and droplet morphology, resulting in the optimal rate.

[0045] In summary, this invention can completely degrade organic waste and recover pure metals with zero reagents, providing technical support for environmental governance and resource recycling. Compared with existing technologies, this invention represents a significant advancement.

[0046] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A wastewater treatment system based on droplet impaction, characterized in that, It includes a wastewater tank, a droplet impact reactor, and a recovery tank connected in sequence. The droplet impact reactor includes a droplet release device and a droplet reaction device. The droplet release device is made of conductive material and is used to release the input wastewater in the form of droplets; the droplet reaction device is made of dielectric material and has a superhydrophobic surface. The droplet reaction device is tilted below the droplet release device so that the droplets released by the droplet release device can fall onto the surface of the droplet reaction device to complete the impact and sliding process.

2. The wastewater treatment system based on droplet impaction according to claim 1, characterized in that, The droplet release device is provided with multiple droplet release ends, and the multiple droplet release ends are arranged in an array.

3. The wastewater treatment system based on droplet impaction according to claim 1, characterized in that, The conductive material also has corrosion resistance.

4. The wastewater treatment system based on droplet impaction according to claim 1, characterized in that, The droplet release device releases droplets with a size of 8-18 μL.

5. The wastewater treatment system based on droplet impaction according to claim 1, characterized in that, The relative permittivity of the dielectric material is less than 10.

6. The wastewater treatment system based on droplet impaction according to claim 1, characterized in that, The droplet reaction device is tilted at an angle of 60°.

7. The wastewater treatment system based on droplet impaction according to claim 1, characterized in that, The droplet reaction device is located below the droplet release device to achieve a Weber number of 50-100.

8. The wastewater treatment system based on droplet impaction according to any one of claims 1-7, characterized in that, A circulation pump is also provided between the recycling tank and the input end of the droplet impact reactor. The droplet impact reactor also includes a grounding connection switch, which is connected to the droplet release device to enable the droplet release device to be grounded.

9. The wastewater treatment system based on droplet impaction according to claim 8, characterized in that, When recovering metals from wastewater, the grounding switch is turned on to ground the droplet release device; when treating organic matter in wastewater, the grounding switch is turned off to levitate the droplet release device.

10. A wastewater treatment method based on droplet impaction, characterized in that, The wastewater is treated using the droplet impact-based wastewater treatment system described in any one of claims 1-9.

Images