CN1303000C - Method and apparatus for treating waste water by microwave photocatalysis - Google Patents

Abstract

The invention discloses a method and a device for microwave photocatalytic treatment of wastewater. To treat waste water, it is necessary to remove impurities by grille, settle and adjust pH. After the above preliminary treatment, it enters the device for microwave photocatalytic treatment of waste water for microwave photocatalysis. The device includes a microwave reaction furnace, a waste water reaction chamber and an electrodeless lamp. The waste water reaction chamber is placed in the microwave reaction furnace cavity, and a circular holder is erected on the convex column on the wall of the waste water reaction chamber. The electrodeless lamp is inserted into the small hole of the ring holder, and the quartz The stirrer is placed in the waste water reaction chamber, and the central shaft of the quartz stirrer is connected with the external rotating motor through openings in the upper part of the waste water reaction chamber and the upper part of the microwave reaction furnace. The invention can prolong the service life of the electrodeless lamp and improve the efficiency of photocatalytic degradation; the device is simple, occupies less floor area, and consumes less energy; it integrates microwave action, ultraviolet-visible light, and catalyst photocatalytic oxidation technology, and the concentration of organic matter is less than 100mg /L of wastewater, the removal rate is over 90%.

Description

Method and device for microwave photocatalytic treatment of wastewater

1. Technical field

The invention relates to a method and a device for wastewater treatment, in particular to a method and a device for treating wastewater by using microwaves, microwaves to excite ultraviolet-visible light generated by electrodeless lamps, and loading nanometer catalysts.

2. Background technology

At present, the types and quantities of pollutants entering the environment, especially water bodies, are increasing. Toxic, harmful, tertiary and refractory organic pollutants have seriously threatened the survival of human beings. At present, there are many chemical, physical, and biological methods for eliminating pollution. These methods have shown their own advantages for different types of pollutants and pollution control requirements. However, generally speaking, some traditional treatment technologies can only transfer pollutants and cause serious secondary pollution; some have poor adaptability, and are often powerless when the concentration of pollutants is too high or too low; Although the control method provides some unique technologies for the removal of organic pollutants, such as liquid-liquid extraction method, macroporous adsorption resin method, membrane separation method, ultrasonic method, etc., at present, my country's papermaking, printing and dyeing, pharmaceutical, petrochemical and other industries and There is still a large amount of toxic organic wastewater discharged from the garbage dump, and there is a lack of efficient and thorough treatment methods.

At present, microwave technology is generally paid attention to by people. Microwaves are electromagnetic waves with a frequency of 300MHz to 3006Hz. Microwaves act on matter in a very special way. First of all, microwave is a direct effect on the molecular level of the substance. The "polarization effect" of the substance molecule is caused by the microwave field, which makes the heating more rapid (thermal effect); at the same time, it greatly increases the collision probability between the reactant molecules and makes the reactivity increase (non-thermal effect). Second, microwave action is selective. When heated by microwaves, polar substances heat up quickly, while non-polar substances do not absorb or transmit microwaves. Microwaves have been widely used in the field of environmental science. For example, microwaves have been successfully used in the digestion of environmental samples and the sterilization of drinking water. There are also technologies that use microwaves and external ultraviolet light to degrade organic pollutants. Among them, ultraviolet light is a The degradation of organic matter is a very effective energy source. Due to the high energy of ultraviolet rays, it can break most of the chemical bonds, or combine with catalysts to produce active substances, thereby converting organic pollutants into carbon dioxide and water to achieve the purpose of decontamination. However, these methods consume a lot of energy, and the equipment is complicated. At the same time, when degrading the target pollutants, new pollution may be introduced.

In recent years, some scholars have used microwaves to excite electrodeless lamps to generate ultraviolet light to treat wastewater, such as "Microwave-Infinite Ultraviolet Photocatalytic Oxidation Water Treatment Method" (public number CN 1482072A), and electrodeless ultraviolet lamps are used in the degradation of dye wastewater (Meng Xiangzhou et al. .Research on the degradation of reactive brilliant blue KN-R dye solution by infinite ultraviolet light. Journal of Wuhan Institute of Science and Technology, 2003, 16 (5): 32～36), after 40mg/L reactive brilliant blue KN-R was treated for 110min, the decolorization rate was 73 %, TOC removal 34%. The advantage of this method is that the electrodeless lamp that can generate ultraviolet light does not need an additional power source to provide energy, and the device for the synergistic effect of microwave and ultraviolet light is simple and easy to implement. However, when this electrodeless lamp is excited by microwaves, it flickers indefinitely, the luminous efficiency is not high, the light intensity is small, and it takes a long time to degrade; moreover, the temperature of the electrodeless lamp after being excited can reach 700-1400K. Timely and effective cooling, the excited spectral line will be broadened due to self-absorption, and the life of the electrodeless lamp will be shortened.

3. Contents of the invention

1. Purpose of the invention

The invention provides a method and device for microwave photocatalytic treatment of waste water, which uses microwaves and microwaves to excite electrodeless lamps to generate ultraviolet-visible light, and supports nano-catalysts to photocatalyze and oxidize organic pollutants in waste water, providing an effective solution for the purification of refractory toxic organic waste water. Methods and Apparatus.

2. Technical solution

The invention provides a method and a device for microwave photocatalytic treatment of wastewater. The method for microwave photocatalytic treatment of wastewater includes grid removal, static precipitation, and pH adjustment. After the above preliminary treatment, the wastewater enters a microwave photocatalytic wastewater treatment device for microwave photocatalysis.

The pH value of the wastewater should be controlled between 2 and 10. If it exceeds the range, it needs to be adjusted with acid and alkali. The pH range of the acid-base adjustment solution is 2-10. The microwave photocatalytic treatment of wastewater is carried out in the device for microwave photocatalytic treatment of wastewater. The temperature is kept below 100°C, and the pressure is normal pressure: the nano-catalysts for microwave photocatalysis are semiconductor materials TiO ₂ , ZnO, CdS, or semiconductor materials doped with Cu, Fe, Ag, Cd, Zn, Mn, Co, Ni The composite catalyst of equal oxides is doped with metal oxides in a mass percentage of 0.1% to 5.0%. The nano-catalyst is prepared by sol-gel method, chemical vapor deposition method and solution standing method.

The method of microwave photocatalytic treatment of wastewater, its working principle is: the microwave excites the electrodeless lamp to generate ultraviolet-visible light, and generates high-potential OH or OOH after irradiating the surface of the nano-catalyst film, and oxidizes organic pollutants; or excites the generated Ultraviolet-visible light directly degrades organic matter and realizes the purification of wastewater.

The above-mentioned device for treating waste water by microwave photocatalysis includes a microwave reaction furnace, a waste water reaction chamber and an electrodeless lamp. A quartz stirrer is placed in the waste water reaction chamber in the small hole of the annular fixer, and the central axis of the quartz stirrer is connected with the external rotating motor through openings in the upper part of the waste water reaction chamber and the upper part of the microwave reaction furnace.

In the microwave photocatalytic waste water treatment device proposed by the present invention, waveguides and 5-20 magnetrons are built in the two side walls of the microwave reaction furnace, the power of each magnetron is 0.5-2.0kW, and the inner wall of the microwave reaction furnace is made of stainless steel. materials or materials containing nickel and aluminum; the waste water reaction chamber container is made of microwave-permeable materials such as polytetrafluoroethylene, polystyrene, ceramics, etc., and the upper cover of the container is a detachable opening cover; the inner wall of the waste water reaction chamber is raised There are 3 to 9 convex pillars, and a ring holder is placed on the boss to fix the electrodeless lamp; the ring holder is made of quartz material that does not absorb ultraviolet light, and there are 4 to 8 small holes of appropriate size on the ring holder; The quartz stirrer is a coaxial multi-page quartz plate, and the nano-catalyst is loaded on the quartz plate. The quartz stirrer not only has the function of stirring, but also has the function of catalyst carrier and can transmit ultraviolet light and improve the light utilization rate; the microwave electrodeless lamp is Quartz hollow cylinder or cuboid, the diameter of the bottom circle of the electrodeless lamp is consistent with the diameter of the small hole on the ring holder, and its height is not less than 2/3 of the height of the wastewater reaction chamber; the manufacturing process of the electrodeless lamp is to pump air After reaching 2.5-5.0kPa, fill it with 0.5-2.0kPa argon or helium gas, and drop 1-5 drops of metallic mercury, and finally seal it; the water inlet and outlet of the wastewater reaction chamber are connected with polytetrafluoroethylene water pipes; microwave The side and upper openings of the reaction furnace are covered with aluminum sleeves.

Beneficial effect

Compared with the prior art, the present invention immerses the microwave electrodeless lamp in the waste water solution to keep its surface temperature below 100°C (the boiling point of water), which can prolong the service life of the electrodeless lamp, and the electrodeless lamp produces The ultraviolet-visible light directly acts on the organic wastewater, which can improve the efficiency of photocatalytic degradation; the device is simple, occupies a small area, the reaction pressure is normal pressure, and consumes less energy; the photocatalytic oxidation technology integrating microwave action, ultraviolet-visible light and catalyst , can catalyze the degradation of toxic and harmful organic pollutants that are difficult to degrade by conventional methods, especially phenols, dyes, hormones, pesticides, etc., and the removal rate of organic matter concentration is less than 100mg/L in wastewater. The removal rate is over 90%.

4. Description of drawings

Fig. 1 is a schematic flow chart of the method of the present invention.

Fig. 2 is a sectional view of the device of the present invention.

Fig. 3 is a schematic diagram of the structure of a quartz stirrer.

Fig. 4 is a top view of the ring fixer.

5. Specific implementation

The following is further illustrated by examples.

Example 1

Prepare a 50 mg/L m-nitrophenol aqueous solution to simulate phenol-containing wastewater, without needing a grid to remove impurities. After standing still, adjust the pH of the solution to 3-7. The phenol-containing wastewater passes through the flow meter [4] and the pump [5] at a flow rate of 1.5 L/min Enter the 25L waste water reaction chamber [11], the speed is controlled so that the waste water in the waste water reaction chamber [11] stays for 15 to 20 minutes, and the water flow direction is the way of going in and out. The microwave power is 1000W, and the four electrodeless lamps [17] located in the microwave field are excited by the microwave to generate ultraviolet-visible light. The Ti0 ₂ nanocatalyst loaded on the quartz stirrer [13] by the sol-gel method is exposed to the ultraviolet-visible light. Visible light irradiation, at the same time, the quartz agitator [13] is driven by the motor [12] to rotate at a speed of 30r/m. At this time, the phenolic wastewater solution is simultaneously affected by microwaves, ultraviolet-visible light and _TiO2 nano catalysts. The steam generated in the wastewater reaction chamber [11] is discharged through the upper opening, and the temperature of the electrodeless lamp [17] immersed in the wastewater is lower than 100°C. The m-nitrophenol concentration discharged through the wastewater outlet [19] is less than 5mg/L, and the TOC is reduced by 76%.

Example 2

Prepare 50mg/L rhodamine-B aqueous solution to simulate dye wastewater, adjust the pH value to 3-7, and after standing still, enter the 25L wastewater reaction chamber at a flow rate of 1L/min through the flow meter [4] and pump [5] [11 ], the speed is controlled so that the wastewater in the reaction chamber stays for 25 to 30 minutes, and the direction of water flow is in the way of going up and down. The microwave power is 1500W, and the 6 electrodeless lamps [17] placed in the reaction chamber are excited by the microwave to generate ultraviolet-visible light. The Mn/TiO ₂ catalyst is loaded on the quartz stirrer [13], the doping amount is 0.5%, and the quartz stirrer [13] is loaded with Mn/TiO2 catalyst. The device rotates at a speed of 20r/min driven by an external motor [12]. The temperature in the waste water reaction chamber is less than 100°C and normal pressure. The rhodamine-B concentration in the wastewater discharged through the wastewater outlet is less than 10mg/L, and the TOC is reduced by 70%. The discharged wastewater was refluxed and reprocessed [8], and the rest of the steps were the same as before. The effluent was tested, and the remaining rhodamine-B was less than 1 mg/L, and the remaining TOC was reduced to 5% of the initial concentration.

Example 3

Prepare a 40mg/L bisphenol A aqueous solution to simulate wastewater containing environmental hormones, adjust the pH to 3-7, and after standing still, enter the 25L wastewater reaction chamber [11] at a flow rate of 1L/min through a flow meter [4] and a pump [5]. Control the waste water in the reaction chamber to stay for 25 to 30 minutes, and the direction of water flow is in the way of going up and down. The microwave power is 1500W, and the 6 electrodeless lamps [17] placed in _the reaction chamber are excited by microwaves to generate ultraviolet-visible light. - Irradiation of visible light, at the same time, the quartz stirrer is driven by an external motor [12] to rotate at a speed of 20r/min. The temperature in the waste water reaction chamber is less than 100°C and normal pressure. The concentration of bisphenol A in the wastewater discharged from the wastewater outlet is about 10mg/L, and the TOC is reduced by 50%. The discharged waste water was refluxed and reprocessed [8], and the rest of the steps were the same as before. After the effluent was tested, the remaining bisphenol A was 2 mg/L, and the remaining TOC was 8% of the initial concentration.

Example 4

Prepare 30mg/L atrazine aqueous solution to simulate pesticide wastewater without filtering, adjust the pH to 3-7, and after standing still, enter the 25L wastewater reaction chamber at a flow rate of 1L/min through the flow meter [4] and pump [5] [11 ], the residence time of wastewater in the reaction chamber is 25-30 minutes, and the direction of water flow is the way of going in and out from top to bottom. The microwave power is 1500W, and 6 electrodeless lamps [17] placed in the reaction chamber are excited by microwaves to generate _ultraviolet -visible light. Under the irradiation of ultraviolet-visible light, at the same time, the quartz stirrer is driven by an external motor [12] to rotate at a speed of 20r/m. At this time, the pesticide-containing wastewater solution is simultaneously subjected to microwave, ultraviolet-visible light and Co/TiO ₂ catalyst. The temperature in the waste water reaction chamber is less than 100°C and normal pressure. The concentration of atrazine in the wastewater discharged through the wastewater outlet is less than 5mg/L, and the TOC is reduced by 60%. The discharged wastewater was refluxed for retreatment [8], and the remaining methods were the same as before. The effluent was tested and found that there was no atrazine remaining, and the remaining TOC was 5% of the initial concentration.

Example 5

A laboratory mixed wastewater, the main components are phenol, p-chlorophenol, m-nitrophenol, methyl orange, rhodamine-B, bisphenol A, nonylphenol, atrazine, parathion, TOC before treatment It is 82mg/L, and the impurity is removed by the grid. After standing still, the pH is adjusted to 3~7, and the flow meter [4] and the pump [5] enter the 25L wastewater reaction chamber [11] at a flow rate of 1L/min in the clear night. Stay in the reaction chamber for 25 to 30 minutes, and the direction of water flow is in the way of up and down. The microwave power is 3000W, 8 electrodeless lamps [17] are inserted into the circular holder, Cu/TiO ₂ catalyst is loaded on the quartz stirrer [13], and the doping amount is 1.0%. At the same time, the quartz stirrer is driven by the motor [12] Rotate at a speed of 20r/m. The temperature in the waste water reaction chamber is less than 100°C and normal pressure. The TOC of the wastewater discharged through the wastewater outlet is reduced by 65%. The discharged waste water is refluxed and reprocessed [8] once, and the remaining TOC is 6% of the TOC of the initial solution.

Example 6

Wastewater from a paper mill, pH = 13 before treatment, TOC greater than 100mg/L, impurity removal through grids [1], static precipitation [2], dilute solution TOC to 70mg/L with water, pH adjustment [3] to adjust the pH of the solution The value is 3 to 7, and the flow rate of 1L/min enters the 25L wastewater reaction chamber [11] of the microwave photocatalytic wastewater treatment device through the flow meter [4] and the pump [5], and the wastewater stays in the reaction chamber for 25 to 30 minutes , the direction of water flow is the way of up-in and down-out. The microwave power is 3000W, 8 electrodeless lamps [17] are inserted into the circular holder, Cu/TiO ₂ catalyst is loaded on the quartz stirrer [13], and the doping amount is 1.0%. At the same time, the quartz stirrer is driven by the motor [12] Rotate at a speed of 20r/m. The temperature in the waste water reaction chamber is less than 100°C and normal pressure. The effluent is discharged through the wastewater outlet [7], and the TOC is reduced by 50%. The discharged waste water is refluxed and reprocessed [8] once, and the remaining TOC is 10mg/L.

Example 7

A device for microwave photocatalytic treatment of wastewater, including a microwave reaction furnace [10], a wastewater reaction chamber [11] and an electrodeless lamp [17]. 11] An annular holder [14] is erected on the convex column [18] of the inner wall, the electrodeless lamp [17] is inserted into the small hole of the annular holder [14], and the quartz agitator [13] is placed in the waste water reaction chamber [11] Among them, the central shaft of the quartz agitator [13] is connected to the external rotating motor [12] through the openings on the upper part of the waste water reaction chamber [11] and the upper part of the microwave reaction furnace [10]. There are waveguides [16] and 10 magnetrons [15] built in the two side walls of the microwave reaction furnace [10], the power of each magnetron is 1 kW, and the height of the electrodeless lamp is 1 /2. The quartz stirrer [13] is a coaxial multi-page quartz plate, placed in the center of the hollow circle of the ring holder, and its axis passes through the opening of the waste water reaction chamber [11] and the upper part of the microwave reaction furnace [10] and the rotating motor [12]. connected. There are 6 protrusions [18] on the inner wall of the wastewater reaction chamber, the upper cover of the wastewater reaction chamber is a detachable opening cover, and there are 6 small holes on the ring holder [14], and the electrodeless lamp [17] is inserted into the ring holder [14] in the small hole. The manufacturing method of the electrodeless lamp [17] is to pump the air to 2.5-5.0kPa, fill it with 0.5-2.0kPa argon, helium and other inert gases, add 1-10 drops of metallic mercury, and finally seal it. The wastewater reaction chamber [11] is heat-resistant and corrosion-resistant materials such as polytetrafluoroethylene, polystyrene, pottery, etc., and the inner wall of the microwave reaction furnace [10] is made of stainless steel or materials containing nickel and aluminum.

Claims (10)

1. A method for microwave photocatalytic treatment of waste water, comprising grid impurity removal, static precipitation, pH adjustment, characterized in that waste water enters the device for microwave photocatalytic treatment of waste water after the above-mentioned preliminary treatment, and carries out microwave photocatalysis, in place In the microwave photocatalytic waste water treatment device, the temperature of the waste water is kept below 100°C, and the microwave excites the electrodeless lamp to generate ultraviolet-visible light, and irradiates the nano-catalyst to realize the purification of the waste water. 2. The method according to claim 1, characterized in that the pH value of the waste water is controlled at 2 to 10, and if it exceeds the range, the pH value is adjusted with acid and alkali. 3. The method according to claim 2, characterized in that the residence time of the waste water in the device for microwave photocatalytic treatment of waste water is 20 to 40 minutes, and the pressure is normal pressure. 4. The method according to any one of claims 1 to 3, characterized in that the nano-catalyst of microwave photocatalysis is pure semiconductor material TiO ₂ , ZnO or CdS, or the pure semiconductor material doped with metal oxide The composite catalyst is doped with a metal oxide in a mass percentage of 0.1% to 5.0%, and the metal oxide is a metal oxide of Cu, Fe, Ag, Cd, Zn, Mn, Co or Ni. 5. The method according to claim 1, wherein said device for microwave photocatalytic treatment of waste water comprises a microwave reaction furnace [10], a waste water reaction chamber [11] and an electrodeless lamp [17], and is characterized in that the microwave reaction The waste water reaction chamber [11] is placed in the cavity of the furnace [10], and the ring holder [14] is erected on the convex column [18] of the inner wall of the waste water reaction chamber [11], and the electrodeless lamp [17] is inserted into the ring holder [14]. In the small hole, the quartz agitator [13] is placed in the waste water reaction chamber [11], and the central axis of the quartz agitator [13] passes through the upper part of the waste water reaction chamber [11] and the upper part of the microwave reaction furnace [10] and the external rotating motor [12] connected. 6. method according to claim 5 is characterized in that waveguide [16] and 5～20 magnetrons [15] are built-in in microwave reactor [10] two side walls, and the power of each magnetron is 0.5 ~ 2.0kW, the height of the electrodeless lamp is not lower than 2/3 of the height of the wastewater reaction chamber [11]. 7. The method according to claim 6, characterized in that the quartz stirrer [13] is a coaxial multi-page quartz plate, placed in the center of the hollow circle of the ring fixture, and the shaft of the quartz stirrer passes through the waste water reaction chamber [ 11] and the opening on the top of the microwave reactor [10] is connected with the rotary motor [12]. 8. The method according to claim 5 or 6 or 7, characterized in that there are 3 to 9 protrusions [18] protruding from the inner wall of the wastewater reaction chamber, the upper cover of the wastewater reaction chamber is a detachable opening cover, and a ring holder There are 4～8 small holes on [14], and electrodeless lamp [17] is inserted in the small hole of ring holder [14]. 9. The method according to claim 5 or 6 or 7, characterized in that the electrodeless lamp [17] is made by pumping the air to 2.5-5.0kPa, filling it with argon or helium at 0.5-2.0kPa, and Add 1 to 5 drops of metallic mercury, and finally seal it. 10. The method according to claim 5 or 6 or 7, characterized in that the wastewater reaction chamber [11] is made of heat-resistant and corrosion-resistant materials such as polytetrafluoroethylene, polystyrene or ceramics, and the inner wall of the microwave reaction furnace [10] is made of Stainless steel materials or materials containing nickel and aluminum.

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