A photocatalytic reduction system and method for reducing perchlorate in display fireworks wastewater

Abstract

The present application relates to wastewater treatment technical field, provide a kind of for reducing flower cannon wastewater high chlorate photocatalytic reduction system and method.Light catalytic reduction system includes pretreatment unit and catalytic reaction unit;The pretreatment unit includes sequentially connected primary sedimentation tank, coagulation sedimentation tank, tubular sound-ozone multi-field collaborative reactor and micro-bubble air floatation separator;The catalytic reaction unit includes tungsten trioxide catalytic reactor;The micro-bubble air floatation separator outlet is connected with tungsten trioxide catalytic reactor inlet.The present application avoids high chlorate with concentrated liquid or adsorption material etc. enrichment state form transfer, can reduce subsequent secondary disposal pressure.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a photocatalytic reduction system and method for reducing perchlorate ions in fireworks wastewater. Background Technology

[0002] Perchlorate (ClO4) - Perchlorate is an emerging persistent pollutant characterized by high water solubility, high diffusion, and persistence. It is widely used in various industries. Once it enters the environment, particularly through surface runoff and groundwater, it can migrate long distances and persist for extended periods. Studies show that the natural degradation of perchlorate in water is extremely slow, potentially taking decades to complete. Therefore, its pollution control has received widespread attention.

[0003] Currently, the main technologies for treating perchlorate wastewater include adsorption, ion exchange, membrane separation, chemical reduction, and biological reduction.

[0004] Adsorption, ion exchange, and membrane separation are relatively mature technologies with good removal effects on perchlorate. However, they are essentially processes of pollutant separation and enrichment, and do not achieve complete conversion of perchlorate. The treatment process often generates high-concentration concentrates or degraded adsorbent materials, requiring further disposal, which increases operating costs and environmental management pressure.

[0005] Chemical reduction can reduce perchlorate to chloride ions, but it usually requires the addition of reducing agents, catalysts or enhanced reaction conditions, resulting in problems such as high reagent consumption, high equipment requirements and high operating costs.

[0006] The biological reduction method utilizes the metabolic activity of microorganisms to reduce perchlorate, which has the advantage of low energy consumption. However, it generally suffers from problems such as long start-up period, sensitivity to operating conditions, limited resistance to shock loads, and complex maintenance and management.

[0007] In recent years, photocatalysis technology has attracted widespread attention due to its ability to drive pollutant conversion using light energy. Tungsten trioxide, as a semiconductor material with good visible light response, can generate photoelectrons and holes under light irradiation. Among them, the photoelectrons have strong reducing power and can be used for the conversion of perchlorate to chloride ions. However, current research mainly focuses on the laboratory application of powdered photocatalysts, which suffers from problems such as easy catalyst agglomeration, difficult recovery, insufficient continuous operation capability, and limited engineering applications.

[0008] Furthermore, fireworks wastewater typically contains a large amount of suspended particles, colloidal and binder-like organic matter, including dextrin, starch gum, polyvinyl alcohol, and carboxymethyl cellulose. These substances easily cause a decrease in light transmittance and fouling of the catalyst surface, severely affecting the treatment efficiency and long-term operational stability of the photocatalytic system. Therefore, developing a highly efficient perchlorate removal system suitable for the characteristics of fireworks wastewater is of great significance. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a photocatalytic reduction system and method for reducing perchlorate in fireworks wastewater, which does not produce perchlorate concentrate or perchlorate-enriched waste, thereby reducing the pressure of subsequent secondary treatment.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a photocatalytic reduction system for reducing perchlorate in fireworks wastewater, the photocatalytic reduction system comprising a pretreatment unit and a catalytic reaction unit; the pretreatment unit comprising a primary sedimentation tank, a coagulation sedimentation tank, a tubular acoustic-ozone multi-field synergistic reactor, and a microbubble flotation separator connected in sequence; the catalytic reaction unit comprising a tungsten trioxide catalytic reactor; and the outlet of the microbubble flotation separator being connected to the inlet of the tungsten trioxide catalytic reactor.

[0011] As a preferred example, the coagulation sedimentation tank includes a primary mixing tank, a secondary mixing tank, and a sedimentation zone connected in sequence; the sedimentation zone is connected to the inlet of the tubular acoustic-ozone multi-field synergistic reactor; the primary mixing tank is equipped with a polyaluminum chloride dosing pump; and the secondary mixing tank is equipped with a polyacrylamide dosing pump.

[0012] As a preferred example, the tubular acoustic-ozone multi-field synergistic reactor includes a first inlet pipe, a first connecting pipe, a reaction pipe, a second connecting pipe, and a first outlet pipe connected in sequence; the diameters of the first inlet pipe and the first outlet pipe are larger than the diameter of the reaction pipe, the diameter of the first connecting pipe gradually decreases from the direction closer to the first inlet pipe to the direction farther away from the first inlet pipe, and the diameter of the second connecting pipe gradually increases from the direction closer to the reaction pipe to the direction farther away from the reaction pipe; an inlet pipe is provided on the first inlet pipe; one end of the inlet pipe is connected to the first inlet pipe, and the other end is connected to an ozone micro-nano bubble generator; a high-frequency ultrasonic transducer array is provided on the outside of the reaction pipe.

[0013] As a preferred embodiment, the microbubble flotation separator has a contact area at its bottom, and the outlet of the tubular acoustic-ozone multi-field synergistic reactor is connected to the contact area of ​​the microbubble flotation separator through a gas-liquid mixture diffuser; the top of the microbubble flotation separator is equipped with a chain-type reverse scraper; and the outlet of the microbubble flotation separator is connected to the inlet of the tungsten trioxide catalytic reactor through a conveying pipeline.

[0014] As a preferred embodiment, the tungsten trioxide catalytic reactor includes a reactor body, a tungsten trioxide catalytic plate, a second inlet pipe, and a second outlet pipe; the second inlet pipe and the second outlet pipe are respectively connected to the reactor body, and the tungsten trioxide catalytic plate is disposed inside the reactor body, thereby forming multiple reaction channels inside the reactor body; the reactor body is a transparent sealed box; the tungsten trioxide catalytic plate is a fluorine-doped tin oxide transparent conductive glass substrate, and tungsten trioxide is loaded on the fluorine-doped tin oxide transparent conductive glass substrate; the tungsten trioxide catalytic reactor is equipped with a light source assembly.

[0015] Secondly, the present invention also provides a photocatalytic reduction method for perchlorate ions in fireworks wastewater, employing the photocatalytic reduction system provided in the first aspect; the method includes: Step 10: Pass the fireworks wastewater into the pretreatment unit for pretreatment; Step 20: The pretreated fireworks wastewater is passed into a tungsten trioxide catalytic reactor for reduction reaction, so that low molecular weight organic matter consumes photogenerated holes and the generated photogenerated electrons are used to reduce perchlorate ions.

[0016] As a preferred example, the pretreatment in step 10 includes sedimentation and coagulation of the fireworks wastewater, and the synergistic effect of ozone micro-nano bubbles and ultrasonic cavitation to convert the polymer binder into low-molecular-weight organic matter.

[0017] As a preferred example, step 10 includes, Step 101: Pass the fireworks wastewater into the primary sedimentation tank for the first sedimentation. Step 102: The wastewater treated in step 101 is fed into the primary mixing tank of the coagulation sedimentation tank. Polyaluminum chloride is added to the primary mixing tank and stirred to destabilize the colloidal particles and fine suspended particles in the wastewater and form initial micro-flocs. Step 103: The wastewater treated in step 102 is fed into a secondary mixing tank. Polyacrylamide is added to the secondary mixing tank and stirred to allow the initial micro-flocs to aggregate and form larger flocs through adsorption bridging. Step 104: The wastewater treated in step 103 is passed into the sedimentation zone, where the flocs settle under gravity to complete solid-liquid separation. Step 105: The wastewater treated in step 104 is fed into a tubular acoustic-ozone multi-field synergistic reactor. At the same time, the ozone micro-nano bubble gas-liquid mixture prepared by the ozone micro-nano bubble generator is injected into the first inlet pipe through the inlet pipe. After the reaction in the reaction pipe, the wastewater containing colloidal fragments, flocs, low molecular weight organic matter and residual ozone micro-nano bubbles is output from the first outlet pipe. Step 106: The wastewater treated in step 105 is passed into a microbubble flotation separator to obtain pretreated wastewater with reduced suspended solids and colloid content, reduced turbidity, increased light transmittance, and perchlorate ions still existing in a dissolved state.

[0018] As a preferred example, step 20 specifically includes: Step 201: The pretreated wastewater is fed into the tungsten trioxide catalytic reactor, allowing the wastewater to enter the reaction channel; Step 202: Turn on the light source component to provide stable light to the tungsten trioxide catalyst plate, so that the tungsten trioxide generates photogenerated electron-hole pairs; low molecular weight organic matter in the pretreated wastewater participates in consuming the photogenerated holes, and the photogenerated electrons undergo a reduction reaction with perchlorate ions; Step 203: Collect the wastewater after the reaction.

[0019] Compared with existing technologies, the technical solution of this invention has the following beneficial effects: Firstly, this invention pre-treats fireworks wastewater by constructing a pretreatment device comprising a primary sedimentation tank, a coagulation sedimentation tank, a tubular acoustic-ozone multi-field synergistic reactor, and a microbubble flotation separator. This pre-treats the wastewater by breaking down and partially degrading the stubborn polymeric binders in the wastewater that clog and block light from the catalyst plate into small-molecule organic acids such as oxalic acid and acetic acid, which are then converted into hole sacrificial agents required for the tungsten trioxide reduction reaction. Secondly, this invention sets up a tungsten trioxide reactor after the pretreatment device, immobilizing a tungsten trioxide catalytic film on the surface of a fluorinated tin oxide (FTO) substrate. Under illumination, the tungsten trioxide absorbs light energy and generates photogenerated electrons and holes through the hole sacrificial agent produced by the pretreatment device. Perchlorate ions diffuse to the surface of the tungsten trioxide catalytic layer and undergo a reduction reaction with the photogenerated electrons, gradually transforming and ultimately forming chloride ions. The wastewater after the reaction flows along the reaction channel and is discharged and collected from the reactor outlet. This provides a feasible path for in-situ reduction and transformation of perchlorate under continuous industrial flow conditions, which consumes less energy, does not produce perchlorate concentrate or perchlorate-enriched waste, and reduces the pressure of subsequent secondary treatment. Attached Figure Description

[0020] Figure 1 This is a structural diagram of the photocatalytic reduction system in an embodiment of the present invention; Figure 2 yes Figure 1 Structural diagram of a tubular acoustic-ozone multi-field synergistic reactor; Figure 3 yes Figure 1 Structural diagram of the tungsten trioxide catalytic reactor; The diagram includes: primary sedimentation tank 1, coagulation sedimentation tank 2, tubular acoustic-ozone multi-field synergistic reactor 3, microbubble flotation separator 4, reactor body 5, tungsten trioxide catalyst plate 6, second inlet pipe 7, second outlet pipe 8, primary mixing tank 21, secondary mixing tank 22, sedimentation zone 23, first inlet pipe 31, first outlet pipe 32, high-frequency ultrasonic transducer array 33, inlet pipe 34, ozone micro-nano bubble generator 35, reaction pipe 36, second connecting pipe 37, and first connecting pipe 38. Detailed Implementation

[0021] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] In a first aspect, the present invention provides a photocatalytic reduction system for reducing perchlorate in fireworks wastewater. The photocatalytic reduction system includes a pretreatment unit and a catalytic reaction unit. The pretreatment unit includes a primary sedimentation tank 1, a coagulation sedimentation tank 2, a tubular acoustic-ozone multi-field synergistic reactor 3, and a microbubble flotation separator 4 connected in sequence. The catalytic reaction unit includes a tungsten trioxide catalytic reactor. The outlet of the microbubble flotation separator 4 is connected to the inlet of the tungsten trioxide catalytic reactor.

[0023] As a preferred example, the coagulation sedimentation tank 2 includes a primary mixing tank 21, a secondary mixing tank 22, and a sedimentation zone 23 connected in sequence; the sedimentation zone 23 is connected to the inlet of the tubular acoustic-ozone multi-field synergistic reactor 3; the primary mixing tank 21 is equipped with a polyaluminum chloride dosing pump; and the secondary mixing tank 22 is equipped with a polyacrylamide dosing pump.

[0024] The primary mixing tank 21 is mainly used for the rapid dispersion of polyaluminum chloride (PAC) and the coagulation and destabilization of colloidal particles in wastewater. After wastewater enters the primary mixing tank 21 and PAC is added, the PAC is rapidly and uniformly dispersed in the wastewater under the action of a high-speed shear mixer. The PAC undergoes hydrolysis, and through charge neutralization, double-layer compression, adsorption, and entrapment sweeping, it reduces the electrostatic repulsion between colloidal particles in the wastewater, causing the originally stable dispersed colloidal particles and fine suspended particles to destabilize and form initial micro-flocs.

[0025] The secondary mixing tank 22 is mainly used to promote the further aggregation and growth of initial micro-flocs. After wastewater enters the secondary mixing tank 22 and polyacrylamide is added, under low-speed impeller stirring conditions, the added polyacrylamide connects multiple initial micro-flocs through the adsorption and bridging effect of the polymer chains, forming larger flocs with larger size, more stable structure, and easier gravity settling. The use of low-speed stirring can promote floc collision and growth while avoiding excessive shearing and breakage of the flocs.

[0026] After the wastewater completes floc growth in the secondary mixing tank 22, it enters the sedimentation zone 23. Larger flocs settle under gravity, and the supernatant enters the subsequent tubular acoustic-ozone multi-field synergistic reactor 3.

[0027] After coagulation, flocculation and sedimentation, the larger flocs formed settle and are removed in sedimentation zone 23. Most of the suspended solids and easily miscible gels in the supernatant after sedimentation have been removed, but soluble or microcolloid polymer binders that are difficult to remove by coagulation and sedimentation still enter the tubular acoustic-ozone multi-field synergistic reactor 3 along with the supernatant.

[0028] As a preferred embodiment, the tubular acoustic-ozone multi-field synergistic reactor 3 includes a first inlet pipe 31, a first connecting pipe 38, a reaction pipe 36, a second connecting pipe 37, and a first outlet pipe 32 connected in sequence; the diameters of the first inlet pipe 31 and the first outlet pipe 32 are larger than the diameter of the reaction pipe 36; the diameter of the first connecting pipe 38 gradually decreases from near the first inlet pipe 31 to away from the first inlet pipe 31; the diameter of the second connecting pipe 37 gradually increases from near the reaction pipe 36 to away from the reaction pipe 36; an inlet pipe 34 is provided on the first inlet pipe 31; one end of the inlet pipe 34 is connected to the first inlet pipe 31, and the other end is connected to the ozone micro-nano bubble generator 35; a high-frequency ultrasonic transducer array 33 is provided on the outside of the reaction pipe 36.

[0029] The ozone micro-nano bubble generator 35 is an integrated gas-liquid mixing device. Internally, it completes the preparation of ozone gas, the mixing of ozone and water, and the formation of ozone micro-nano bubbles, outputting a gas-liquid mixture containing ozone micro-nano bubbles. The ozone micro-nano bubble generator 35 is located outside the tubular acoustic-ozone multi-field synergistic reactor 3. Before wastewater enters the tubular acoustic-ozone multi-field synergistic reactor 3, the ozone micro-nano bubble generator 35 prepares the gas-liquid mixture containing ozone micro-nano bubbles and injects it into the first inlet pipe 31 through the inlet pipe 34. After mixing with the wastewater, the gas-liquid mixture enters the reaction pipe 36.

[0030] When the wastewater enters the smaller diameter reaction pipe 36 from the larger diameter first inlet pipe 31, the flow rate increases. Under the fluid shearing, turbulent mixing and ultrasonic cavitation generated by the variable diameter flow channel and the high-frequency ultrasonic transducer array 33, the polymer binder undergoes chain breaking, gel breaking, viscosity reduction and partial oxidative degradation. This process can enhance the dispersion of ozone micro-nano bubbles in the wastewater and the mass transfer of ozone to the liquid phase.

[0031] The high-frequency ultrasonic transducer array 33, located outside the reaction tube 36, generates ultrasonic cavitation, causing ozone micro- and nanobubbles to oscillate, contract, and rupture, forming localized microjets, shock waves, and high shear forces. Ultrasonic cavitation and ozone oxidation synergistically act on polymeric binders such as dextrin, starch gum, polyvinyl alcohol, and carboxymethyl cellulose, breaking their long-chain structures and converting some high-molecular-weight organic compounds into low-molecular-weight organic compounds or low-molecular-weight organic acids.

[0032] The low-molecular-weight organic matter generated by the tubular acoustic-ozone multi-field synergistic reactor 3 enters the tungsten trioxide catalytic reactor along with the pretreated wastewater and acts as a hole sacrificial agent in the photocatalytic reaction to reduce photogenerated electron-hole recombination and improve the perchlorate reduction efficiency.

[0033] The main purposes of injecting ozone micro-nano bubble generator 35 into wastewater in this embodiment are as follows: First, to utilize the oxidizing effect of ozone to break down the polymer binders such as dextrin, starch glue, polyvinyl alcohol, and carboxymethyl cellulose in the fireworks wastewater, causing them to undergo chain breakage, gelation, and partial oxidative degradation; Second, to utilize the small particle size and large gas-liquid contact area of ​​micro-nano bubbles to improve the dispersion, mass transfer efficiency, and utilization rate of ozone in the wastewater; Third, to enhance ozone oxidation by combining the turbulence generated by the variable diameter flow channel and the cavitation effect generated by ultrasound. The process involves: 1) breaking down the polymer binder; 2) reducing wastewater viscosity and colloidal stability, thereby minimizing the shading and clogging caused by the polymer binder on the subsequent tungsten trioxide catalyst plate 6; 3) converting some high-molecular organic matter into soluble low-molecular organic matter, providing conditions for the consumption of photogenerated holes in the subsequent photocatalytic reaction; and 4) utilizing incompletely consumed ozone micro-nano bubbles as a buoyancy carrier in the subsequent air flotation process, promoting the separation of flocs, colloidal fragments, and suspended particles, thus realizing the tandem utilization of ozone micro-nano bubbles in the front-end chemical oxidation and the back-end physical air flotation.

[0034] The ultimate goal of the tubular acoustic-ozone multi-field synergistic reactor 3 is to break down polymer binders, enhance ozone mass transfer, and generate low-molecular-weight organic matter. Its overall functions include: First, utilizing a variable-diameter flow channel to increase local flow velocity and generate fluid shearing and turbulent mixing, ensuring thorough mixing of ozone micro / nanobubbles with wastewater; Second, utilizing ultrasonic cavitation generated by a high-frequency ultrasonic transducer to cause oscillation and collapse of ozone micro / nanobubbles; Third, utilizing the synergistic effects of fluid shearing, ultrasonic cavitation, and ozone oxidation to cause chain breakage, debonding, viscosity reduction, and partial oxidative degradation of polymer binders such as dextrin, starch glue, polyvinyl alcohol, and carboxymethyl cellulose; Fourth, converting some high-molecular-weight organic matter into soluble low-molecular-weight organic matter or low-molecular-weight organic acids, enabling them to participate in consuming photogenerated holes in the subsequent tungsten trioxide photocatalytic reaction; Fifth, reducing the light-shielding, adhesion, and fouling effects of polymer binders on the tungsten trioxide catalyst plate 6.

[0035] As a preferred embodiment, the microbubble flotation separator 4 has a contact area at its bottom, and the outlet of the tubular acoustic-ozone multi-field synergistic reactor 3 is connected to the contact area of ​​the microbubble flotation separator 4 through a gas-liquid mixture diffuser; the top of the microbubble flotation separator 4 is equipped with a chain-type reverse scraper; and the outlet of the microbubble flotation separator 4 is connected to the inlet of the tungsten trioxide catalytic reactor through a conveying pipeline.

[0036] The microbubble flotation separator 4 is mainly used to remove residual flocs, colloidal fragments, suspended particles, and some incompletely degraded macromolecular organic matter after treatment by the tubular acoustic-ozone multi-field synergistic reactor 3.

[0037] Wastewater discharged from the tubular acoustic-ozone multi-field synergistic reactor 3 enters the contact zone at the bottom of the microbubble flotation separator 4 through a gas-liquid mixture diffuser. Unconsumed ozone micro-nano bubbles in the wastewater collide with and adhere to destabilized colloids, flocs, colloidal fragments, and suspended particles, forming bubble-floc complexes. The apparent density of these bubble-floc complexes is lower than that of water, therefore they float to the surface under buoyancy and form a scum layer. A residual ozone reduction unit is installed between the clear water outlet of the microbubble flotation separator 4 and the tungsten trioxide catalytic reactor to reduce the residual ozone concentration in the flotation effluent.

[0038] A chain-type reverse scraper, located at the top of the microbubble flotation separator 4, continuously scrapes scum into the scum collection area, achieving the separation of pollutants from the water. The clarified water after flotation separation is collected by the water collection pipe or effluent weir in the clear water zone and transported to the tungsten trioxide catalytic reactor.

[0039] The microbubble flotation separator 4 is equipped with a sealed cover on top, which is connected to the ozone exhaust gas decomposition device through the exhaust gas collection pipe to collect part of the ozone that escapes from the microbubble flotation separator 4.

[0040] The contact zone in the microbubble flotation separator 4 is the functional area at the bottom of the microbubble flotation separator 4. The contact zone is used to receive the wastewater containing micro-nano bubbles discharged from the tubular acoustic-ozone multi-field synergistic reactor 3, so that the remaining ozone micro-nano bubbles can fully contact the destabilized colloids, flocs, colloidal fragments and suspended particles in the wastewater.

[0041] The gas-liquid mixed wastewater diffuser is set in the contact zone to evenly distribute the gas-liquid mixed wastewater to the contact zone, thereby improving the collision and adhesion efficiency between micro-nano bubbles and pollutants.

[0042] The chain-type reverse scum scraper is installed at the top of the microbubble flotation separator 4 to continuously scrape off the scum formed on the liquid surface, discharge the enriched flocs and suspended particles from the system, and prevent the scum from re-entering the water body.

[0043] The water collection pipe or outlet weir in the clear water zone is used to collect the clarified water after air flotation separation evenly and transport the clarified water to the tungsten trioxide catalytic reactor.

[0044] As a preferred embodiment, the tungsten trioxide catalytic reactor includes a reactor body 5, a tungsten trioxide catalytic plate 6, a second inlet pipe 7, and a second outlet pipe 8; the second inlet pipe 7 and the second outlet pipe 8 are respectively connected to the reactor body 5; the tungsten trioxide catalytic plate 6 is disposed inside the reactor body 5, thereby forming multiple reaction channels within the reactor body 5; the reactor body 5 is a transparent sealed box; the tungsten trioxide catalytic plate 6 is a fluorine-doped tin oxide transparent conductive glass substrate, on which tungsten trioxide is loaded; the tungsten trioxide catalytic reactor is equipped with a light source assembly.

[0045] After pretreatment, the wastewater from fireworks enters the tungsten trioxide catalytic reactor and flows through the tungsten trioxide catalytic plate 6. At this point, light is supplied to the interior through a light source assembly. Under illumination, the tungsten trioxide absorbs light energy, generating photogenerated electrons and holes. The low-molecular-weight organic matter retained in the pretreated wastewater can undergo an oxidation reaction with the photogenerated holes, thereby reducing the recombination of photogenerated electrons and holes and increasing the number of photogenerated electrons participating in the reduction reaction.

[0046] Perchlorate ions diffuse to the surface of the tungsten trioxide catalyst layer and undergo a reduction reaction with photogenerated electrons, gradually transforming and ultimately forming chloride ions. The wastewater after the reaction flows along the reaction channel and is discharged and collected from the reactor outlet.

[0047] In a photocatalytic reduction system for reducing perchlorate in fireworks wastewater, a mechanism for in-situ transformation and internal circulation between pre-treated pollutants and subsequent photocatalytic additives is established. The system utilizes a pre-treatment tubular acoustic-ozone multi-field synergistic reactor 3 to break down and partially degrade stubborn polymeric binders (dextrin, polyvinyl alcohol, carboxymethyl cellulose, etc.) in the fireworks wastewater that clog and block light from the catalyst plate into small-molecule organic acids such as oxalic acid and acetic acid. These degradation products are then continuously fed into the subsequent photocatalytic reactor, where they are in-situ converted into hole sacrificial agents required for the reduction of tungsten trioxide.

[0048] Furthermore, this invention constructs a continuous flow series utilization process for ozone source between a closed flow channel (chemical oxidation) and an open tank (physical flotation). The system only adds ozone micro-nano bubbles once in the first half of the tubular reactor, utilizing an ultrasonic field to perform partial sonochemical catalysis to achieve advanced oxidation and debriding. The remaining ozone micro-nano bubbles, not fully consumed, are directly sprayed into the microbubble flotation separator 4 in the second half of the system, where they act as a physical buoyancy carrier in situ under laminar flow conditions, encapsulating and pulling the destabilized flocs to the surface. This design eliminates the need for a separate aeration system in the flotation tank while enabling deep mass transfer and consumption of ozone gas within the closed flow channel. Furthermore, the sealed hood at the top of the device eliminates the safety hazard of ozone gas escape that can occur in traditional open flotation tanks.

[0049] This invention incorporates multiple sets of parallel-arranged immobilized slots within the reactor body 5, used for mounting and securing tungsten trioxide catalyst plates 6. By immobilizing a petal-shaped micro / nano structured tungsten trioxide catalyst film onto an FTO substrate via in-situ hydrothermal growth, the in-situ, room-temperature, and ambient-pressure final-state reduction of perchlorate to chloride ions is achieved. The FTO substrate possesses excellent electrical conductivity, forming a good ohmic contact with the in-situ hydrothermally grown tungsten trioxide. Microscopically, it acts as a highly efficient charge collection and transport channel, promptly extracting and redistributing photogenerated electrons generated by photoexcitation, mitigating the recombination tendency of charge carriers within the bulk phase of the film, thereby increasing the effective electron abundance for perchlorate reduction. Ultimately, the photogenerated electrons generated in the tungsten trioxide catalytic reactor reduce perchlorate to chloride ions in situ. This invention does not produce perchlorate concentrate or perchlorate-enriched waste, reducing the burden of subsequent secondary treatment.

[0050] Secondly, the present invention provides a method for reducing perchlorate ions in fireworks wastewater, employing the photocatalytic reduction system described in the above embodiment, the method comprising: Step 10: Pass the fireworks wastewater into the pretreatment unit for pretreatment; Step 20: The pretreated fireworks wastewater is passed into a tungsten trioxide catalytic reactor for reduction reaction, so that low molecular weight organic matter consumes photogenerated holes and the generated photogenerated electrons are used to reduce perchlorate ions.

[0051] As a preferred example, the pretreatment in step 10 includes sedimentation and coagulation of the fireworks wastewater, and the synergistic effect of ozone micro-nano bubbles and ultrasonic cavitation to convert the polymer binder into low-molecular-weight organic matter.

[0052] As a preferred example, step 10 includes: Step 101: The wastewater from fireworks is introduced into the primary sedimentation tank 1 for the first sedimentation. Step 102: The wastewater treated in step 101 is fed into the primary mixing tank 21 of the coagulation sedimentation tank 2. Polyaluminum chloride is added to the primary mixing tank 21 and stirred to destabilize the colloidal particles and fine suspended particles in the wastewater and form initial micro-flocs. Step 103: The wastewater treated in step 102 is fed into the secondary mixing tank 22. Polyacrylamide is added into the secondary mixing tank 22 and stirred, so that the initial micro flocs aggregate to form larger flocs through adsorption bridging. Step 104: The wastewater treated in step 103 is passed into sedimentation zone 23, where the flocs settle under gravity to complete solid-liquid separation. Step 105: The wastewater treated in step 104 is fed into the tubular acoustic-ozone multi-field synergistic reactor 3. At the same time, the ozone micro-nano bubble gas-liquid mixture prepared by the ozone micro-nano bubble generator 35 is injected into the first water inlet pipe 31 through the inlet pipe 34. After reacting in the reaction pipe 36, the wastewater containing colloidal fragments, flocs, low molecular weight organic matter and residual ozone micro-nano bubbles is discharged from the first water outlet pipe 32. Step 106: The wastewater treated in step 105 is passed into the microbubble flotation separator 4 to obtain pretreated wastewater with reduced suspended solids and colloid content, reduced turbidity, improved light transmittance, and perchlorate ions still existing in a dissolved state.

[0053] As a preferred example, step 20 specifically includes: Step 201: The pretreated wastewater is fed into the tungsten trioxide catalytic reactor, allowing the wastewater to enter the reaction channel; Step 202: Turn on the light source assembly to provide stable light to the tungsten trioxide catalyst plate 6, so that the tungsten trioxide generates photogenerated electron-hole pairs; low molecular weight organic matter in the pretreated wastewater participates in consuming the photogenerated holes, and the photogenerated electrons undergo a reduction reaction with perchlorate ions; Step 203: Collect the wastewater after the reaction.

[0054] The process for reducing perchlorate in fireworks wastewater described in the above embodiment is as follows: Fireworks wastewater is fed into primary sedimentation tank 1 to remove larger-sized and denser impurities and suspended particles.

[0055] After primary sedimentation, the wastewater enters coagulation sedimentation tank 2, where it undergoes rapid coagulation with polyaluminum chloride (PAC), slow flocculation with polyacrylamide (PAM), and gravity sedimentation in sequence to remove fine suspended particles and easily mixed gels.

[0056] The supernatant after coagulation and sedimentation enters the tubular acoustic-ozone multi-field synergistic reactor 3, where the residual soluble or microcolloid polymer binder is subjected to chain breaking, gel breaking, and partial oxidative degradation.

[0057] The wastewater after the reaction enters the microbubble flotation separator 4 to remove colloidal fragments and fine suspended particles formed during the depolymerization process.

[0058] The pretreated wastewater after microbubble flotation separation enters the reactor body 5 through the inlet of the tungsten trioxide catalytic reactor, and is evenly fed into the reaction channel formed by multiple tungsten trioxide catalytic plates 6 through the guide or water distribution structure.

[0059] The tungsten trioxide catalyst plate 6 includes an FTO transparent conductive glass substrate and a tungsten trioxide catalyst layer supported or grown in situ on the surface of the FTO transparent conductive glass substrate. Light emitted from the light source assembly passes through the transparent reactor body 5 and irradiates the tungsten trioxide catalyst layer.

[0060] Under illumination, tungsten trioxide absorbs light energy, generating photogenerated electrons and holes. Low-molecular-weight organic matter retained in the pretreated wastewater can react with these photogenerated holes through oxidation, thereby reducing the recombination of photogenerated electrons and holes and increasing the number of photogenerated electrons participating in the reduction reaction.

[0061] Perchlorate ions diffuse to the surface of the tungsten trioxide catalyst layer and undergo a reduction reaction with photogenerated electrons, gradually transforming and ultimately forming chloride ions. The wastewater after the reaction flows along the parallel reaction channel and is discharged and collected from the reactor outlet.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the specific embodiments described above. The specific embodiments and descriptions in the specification are merely for further illustrating the principles of the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A photocatalytic reduction system for reducing perchlorate ions in fireworks wastewater, characterized in that, The photocatalytic reduction system includes a pretreatment unit and a catalytic reaction unit; the pretreatment unit includes a primary sedimentation tank (1), a coagulation sedimentation tank (2), a tubular acoustic-ozone multi-field synergistic reactor (3), and a microbubble flotation separator (4) connected in sequence; the catalytic reaction unit includes a tungsten trioxide catalytic reactor; the outlet of the microbubble flotation separator (4) is connected to the inlet of the tungsten trioxide catalytic reactor.

2. The photocatalytic reduction system according to claim 1, characterized in that, The coagulation sedimentation tank (2) includes a primary mixing tank (21), a secondary mixing tank (22) and a sedimentation zone (23) connected in sequence; the sedimentation zone (23) is connected to the inlet of the tubular acoustic-ozone multi-field synergistic reactor (3); the primary mixing tank (21) is equipped with a polyaluminum chloride dosing pump; the secondary mixing tank (22) is equipped with a polyacrylamide dosing pump.

3. The photocatalytic reduction system according to claim 1, characterized in that, The tubular acoustic-ozone multi-field synergistic reactor (3) includes a first inlet pipe (31), a first connecting pipe (38), a reaction pipe (36), a second connecting pipe (37), and a first outlet pipe (32) connected in sequence. The diameters of the first inlet pipe (31) and the first outlet pipe (32) are larger than the diameter of the reaction pipe (36). The diameter of the first connecting pipe (38) gradually decreases from the direction closer to the first inlet pipe (31) to the direction farther away from the first inlet pipe (31), and the diameter of the second connecting pipe (37) gradually increases from the direction closer to the reaction pipe (36) to the direction farther away from the reaction pipe (36). An inlet pipe (34) is provided on the first inlet pipe (31). One end of the inlet pipe (34) is connected to the first inlet pipe (31), and the other end is connected to the ozone micro-nano bubble generator (35). A high-frequency ultrasonic transducer array (33) is provided on the outside of the reaction pipe (36).

4. The photocatalytic reduction system according to claim 1, characterized in that, The microbubble flotation separator (4) has a contact area at the bottom. The outlet of the tubular acoustic-ozone multi-field synergistic reactor (3) is connected to the contact area of ​​the microbubble flotation separator (4) through a gas-liquid mixture diffuser. The top of the microbubble flotation separator (4) is equipped with a chain-belt reverse scraper. The outlet of the microbubble flotation separator (4) is connected to the inlet of the tungsten trioxide catalytic reactor through a conveying pipeline.

5. The photocatalytic reduction system according to claim 1, characterized in that, The tungsten trioxide catalytic reactor includes a reactor body (5), a tungsten trioxide catalytic plate (6), a second inlet pipe (7), and a second outlet pipe (8); the second inlet pipe (7) and the second outlet pipe (8) are respectively connected to the reactor body (5), and the tungsten trioxide catalytic plate (6) is disposed inside the reactor body (5), so that multiple reaction channels are formed inside the reactor body (5); the reactor body (5) is a transparent sealed box; the tungsten trioxide catalytic plate (6) is a fluorine-doped tin oxide transparent conductive glass substrate, and tungsten trioxide is loaded on the fluorine-doped tin oxide transparent conductive glass substrate; the tungsten trioxide catalytic reactor is equipped with a light source assembly.

6. A photocatalytic reduction method for perchlorate ions in fireworks wastewater, characterized in that, The photocatalytic reduction system according to any one of claims 1-5 is used; the method includes: Step 10: Pass the fireworks wastewater into the pretreatment unit for pretreatment; Step 20: The pretreated fireworks wastewater is passed into a tungsten trioxide catalytic reactor for reduction reaction, so that low molecular weight organic matter consumes photogenerated holes and the generated photogenerated electrons are used to reduce perchlorate ions.

7. The photocatalytic reduction method according to claim 6, characterized in that, The pretreatment in step 10 includes sedimentation and coagulation of the fireworks wastewater, and the synergistic effect of ozone micro-nano bubbles and ultrasonic cavitation to convert the polymer binder into low-molecular-weight organic matter.

8. The photocatalytic reduction method according to claim 7, characterized in that, Step 10 includes: Step 101: The wastewater from fireworks is fed into the primary sedimentation tank (1) for the first sedimentation. Step 102: The wastewater treated in step 101 is fed into the primary mixing tank (21) of the coagulation sedimentation tank (2). Polyaluminum chloride is added to the primary mixing tank (21) and stirred to destabilize the colloidal particles and fine suspended particles in the wastewater and form initial micro-flocs. Step 103: The wastewater treated in step 102 is fed into the secondary mixing tank (22), polyacrylamide is added into the secondary mixing tank (22) and stirred, so that the initial micro flocs aggregate to form larger flocs through adsorption bridging. Step 104: The wastewater treated in step 103 is passed into the sedimentation zone (23), and the flocs settle under gravity to complete the solid-liquid separation. Step 105: The wastewater treated in step 104 is fed into the tubular acoustic-ozone multi-field synergistic reactor (3). At the same time, the ozone micro-nano bubble gas-liquid mixture prepared by the ozone micro-nano bubble generator (35) is injected into the first water inlet pipe (31) through the inlet pipe (34). After the reaction is carried out through the reaction pipe (36), the wastewater containing colloidal fragments, flocs, low molecular weight organic matter and residual ozone micro-nano bubbles is discharged from the first water outlet pipe (32). Step 106: The wastewater treated in step 105 is passed into a microbubble flotation separator (4) to obtain pretreated wastewater with reduced suspended solids and colloid content, reduced turbidity, increased light transmittance, and perchlorate ions still existing in a dissolved state.

9. The photocatalytic reduction method according to claim 6, characterized in that, Step 20 specifically includes: Step 201: The pretreated wastewater is fed into the tungsten trioxide catalytic reactor, allowing the wastewater to enter the reaction channel; Step 202: Turn on the light source assembly to provide stable light to the tungsten trioxide catalyst plate (6) so that tungsten trioxide generates photogenerated electron-hole pairs; low molecular weight organic matter in the pretreated wastewater participates in consuming photogenerated holes, and photogenerated electrons undergo a reduction reaction with perchlorate ions; Step 203: Collect the wastewater after the reaction.

Images