CN109304108B - Micro-nano bubble generation device and method and application of micro-nano bubble generation device and method in dye wastewater treatment - Google Patents

Micro-nano bubble generation device and method and application of micro-nano bubble generation device and method in dye wastewater treatment Download PDF

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CN109304108B
CN109304108B CN201710632218.2A CN201710632218A CN109304108B CN 109304108 B CN109304108 B CN 109304108B CN 201710632218 A CN201710632218 A CN 201710632218A CN 109304108 B CN109304108 B CN 109304108B
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wastewater
micro
gas
ejector
treatment
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CN109304108A (en
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余江
陈鹏
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Beijing University of Chemical Technology
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Beijing University of Chemical Technology
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01FMIXING, e.g. DISSOLVING, EMULSIFYING, DISPERSING
    • B01F3/00Mixing, e.g. dispersing, emulsifying, according to the phases to be mixed
    • B01F3/04Mixing, e.g. dispersing, emulsifying, according to the phases to be mixed gases or vapours with liquids
    • B01F3/04099Introducing a gas or vapour into a liquid medium, e.g. producing aerated liquids
    • B01F3/04446Making foam
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01FMIXING, e.g. DISSOLVING, EMULSIFYING, DISPERSING
    • B01F5/00Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F5/02Jet mixers
    • B01F5/0281Jet mixers characterized by the specific design of the jet injector
    • B01F5/0287Jet mixers characterized by the specific design of the jet injector the jet injector being of the RESS (explosive rapid expansion of supercritical solutions) or FIMS (fluid injection of molecular spray) type, i.e. the liquid is jetted in an environment (gas or liquid) by nozzles, in conditions of significant pressure drop, with the possible generation of shock waves
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/72Treatment of water, waste water, or sewage by oxidation
    • C02F1/74Treatment of water, waste water, or sewage by oxidation with air
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01FMIXING, e.g. DISSOLVING, EMULSIFYING, DISPERSING
    • B01F3/00Mixing, e.g. dispersing, emulsifying, according to the phases to be mixed
    • B01F3/04Mixing, e.g. dispersing, emulsifying, according to the phases to be mixed gases or vapours with liquids
    • B01F3/04099Introducing a gas or vapour into a liquid medium, e.g. producing aerated liquids
    • B01F2003/04843Introducing a gas or vapour into a liquid medium, e.g. producing aerated liquids characterized by the gas being introduced or the material in which the gas is introduced
    • B01F2003/04851Introducing a gas or vapour into a liquid medium, e.g. producing aerated liquids characterized by the gas being introduced or the material in which the gas is introduced characterized by the gas being introduced
    • B01F2003/04865Aerating, i.e. introducing oxygen containing gas in liquids
    • B01F2003/04872Normal air
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01FMIXING, e.g. DISSOLVING, EMULSIFYING, DISPERSING
    • B01F2215/00Auxiliary or complementary information in relation with mixing
    • B01F2215/0001Field of application of the mixing device
    • B01F2215/0052Treatment of water, waste water or sewage
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/30Organic compounds
    • C02F2101/308Dyes; Colorants; Fluorescent agents
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00Use of specific compounds during water treatment
    • C02F2305/02Specific form of oxidant
    • C02F2305/023Reactive oxygen species, singlet oxygen, OH radical

Abstract

The invention provides a micro-nano bubble generating device and method and application in dye wastewater treatment. The device can generate a large amount of micro-nano bubbles with low rising speed and the diameter of more than 100nm to 300nm by adjusting the air suction amount of the gas-liquid mixing pump and the ejector. Aiming at the problems of deep chromaticity, high COD (chemical oxygen demand) and difficult degradation of dye wastewater, the efficient oxygenation of micro-nano bubbles and the characteristic of generating hydroxyl radicals can degrade organic matters in water without selectivity, and foams generated in the degradation process can be relieved by fine adjustment of temperature, salt concentration, defoaming agent concentration and the like. The micro-nano bubble generating device and the method provided by the invention have extremely high application value in dye wastewater treatment.

Description

Micro-nano bubble generation device and method and application of micro-nano bubble generation device and method in dye wastewater treatment
Technical Field
The invention belongs to the technical field of dye wastewater treatment, and particularly relates to a micro-nano bubble generating device and method and application in dye wastewater treatment.
Background
The dye wastewater is mainly wastewater generated in the dye production process, and because the domestic dyes are various in types and complex in production process, the dye wastewater often contains a lot of organic matters and salts. Most dyes have aromatic ring structures with large molecular weight, so that organic matters in the dye wastewater have the problems of stable performance, high COD (chemical oxygen demand) and difficult degradation.
At present, the treatment technology of dye wastewater mainly comprises an adsorption method, a coagulation method, an advanced oxidation method, a biological oxidation method and the like. However, the adsorption method and the flocculation precipitation method have large sludge production, the cost of the adsorbent or the coagulant is high, and pollutants are only immobilized in the adsorbent or the coagulant and cannot be mineralized and degraded. Oxidation by Fenton, photocatalysis, electrochemical oxygenThe advanced oxidation method mainly has no selectivity on the degradation of pollutants, and has better treatment effect on high-concentration dye wastewater. However, iron mud generated by Fenton oxidation may generate secondary pollution, and Fenton reaction has high requirements on pH and limited mineralization effect; with TiO2The photocatalytic oxidation represented by the above has a limited ability to utilize visible light; electrochemical oxidation is difficult to be widely used in industry due to high cost. The biological oxidation method has a long reaction period and a large occupied area, and has certain limitations because the normal metabolic process of microorganisms in the sludge is difficult to control aiming at dye which is a substance with a special chemical structure and toxicity.
Therefore, a method for treating dye wastewater in a green manner, which is safe, reliable, free from secondary pollution, short in reaction period, small in occupied area, convenient to operate and control and low in cost, is urgently needed to be developed.
Disclosure of Invention
In order to solve the above problems, the present inventors have conducted intensive studies and, as a result, have found that: the micro-nano bubbles generated by jet flow can generate a large amount of intermediate active species (such as hydroxyl free radicals) with strong oxidizing property, and meanwhile, the gas-liquid mass transfer rate can be greatly improved, and the dye in the wastewater can be effectively degraded under the set acid-base environment and temperature; meanwhile, the problem of generation of a large amount of foams on the surface of the water body in wastewater treatment is solved by setting conditions and adding substances; the wastewater treatment method has low cost, simple operation and no secondary pollution generation, and avoids the influence on the subsequent industrial production popularization, thereby completing the invention.
The invention aims to provide the following technical scheme:
(1) a micro-nano bubble generating device comprises a gas-liquid mixing pump 1, a pressure dissolved air tank 2, an ejector 3 and a water tank 4 which are sequentially connected by pipelines,
the lower end of the pressure dissolved air tank 2 is provided with a water inlet which is directly connected with a water outlet of the gas-liquid mixing pump 1, and a water outlet at the upper end of the pressure dissolved air tank 2 is connected with the ejector 3; the ejector 3 generates micro-nano bubbles and introduces fluid containing the micro-nano bubbles into the water tank 4; the water tank 4 is directly connected with the water inlet of the gas-liquid mixing pump 1, so that the device forms a circulating system.
(2) The device according to the above (1), wherein an exhaust valve 21 is installed at the top of the pressure dissolved air tank 2; and/or
The water outlet pipeline of the pressure dissolved air tank 2 is divided into two branches: one branch pipeline, namely branch 1, is connected with an ejector 3, the preferable branch 1 is also connected with a valve, and the other branch pipeline, namely branch 2, is connected with a valve, a pressure gauge 5 and a liquid flowmeter 6.
(3) The device according to claim (2), wherein the device is used for adjusting the air inflow in the gas-liquid mixing pump 1 and the ejector 3 when micro-nano bubbles are generated;
preferably, the ratio of the suction air quantity of the ejector 3 to the flow quantity of the branch 2 is set between 1: 200-1: 350, preferably between 1: 250-1: 300, respectively; and/or
Setting the ratio of the suction volume of the gas-liquid mixing pump 1 to the flow of the branch 2 to be 1: 8-1: 12, preferably between 1: 9-1: 10, respectively.
(4) A wastewater treatment apparatus having the same structure as the micro-nano bubble generating apparatus according to any one of claims 1 to 3;
the wastewater is organic wastewater, preferably dye wastewater, more preferably cationic dye wastewater, such as methylene blue dye wastewater.
(5) A method for treating wastewater by the wastewater treatment apparatus as described in (4) above;
preferably, the method comprises the steps of:
step 1), connecting all functional components in the wastewater treatment device to form a wastewater treatment device capable of performing fluid circulation;
and 2) introducing wastewater into the water tank, and starting the wastewater treatment device to treat the wastewater.
(6) The method according to the above (5), wherein the step 2 further includes adjusting the air intake amounts in the gas-liquid mixing pump 1 and the ejector 3;
preferably, the ratio of the suction air quantity of the ejector 3 to the flow quantity of the branch 2 is set between 1: 200-1: 350, preferably between 1: 250-1: 300, respectively; and/or
Setting the ratio of the suction volume of the gas-liquid mixing pump 1 to the flow of the branch 2 to be 1: 8-1: 12, preferably between 1: 9-1: 10, respectively.
(7) The method according to the above (5), wherein a defoaming agent is added to the wastewater during the treatment, and the defoaming agent is selected from tributyl phosphate, an organosilicon defoaming agent, a polyether defoaming agent or a polyether compound organosilicon defoaming agent, preferably a polyether compound organosilicon defoaming agent.
(8) The method according to the above (5), wherein the pH of the wastewater is controlled to 2 to 5, preferably 3 to 4, during the treatment of the wastewater.
(9) The method according to the above (5), wherein the treatment temperature of the wastewater is controlled to be 20 to 40 ℃, preferably 20 to 30 ℃ during the wastewater treatment.
(10) The method according to the above (5), wherein the volume concentration of the defoaming agent is 0.00045% to 0.005%, preferably 0.00075% to 0.003%, when the treatment temperature is 20 ℃ to 40 ℃ in the wastewater treatment.
According to the micro-nano bubble generating device and method and the application of the micro-nano bubble generating device and method in dye wastewater treatment, the device and method have the following beneficial effects:
(1) the generating device of the micro-nano bubbles has small noise and simple operation: the gas-liquid mixing pump adopted by the generating device can automatically suck gas to mix gas and liquid, so that the problems of high noise of the air compressor, possible oil pollution and the like are avoided, the air-liquid mixing pump can continuously operate as long as the gas-liquid ratio is adjusted in operation, and the use is convenient;
(2) the dye wastewater treatment process has less foam and good degradation effect: the floating foam amount is reduced by adding proper defoaming agent and salt or adjusting pH value, reaction temperature, defoaming agent concentration and other measures;
meanwhile, the foam breaking effect generated by the diffusion pipe section of the ejector can greatly relieve the generation of foam, and redundant foam can be discharged out of the tank body through an exhaust valve of the pressure dissolved air tank, so that micro-nano bubbles are relatively stable in the process of degrading wastewater, and the generation efficiency of free radicals cannot be influenced;
(3) the diameter of the bubbles is small, and the cavitation effect is good: by adjusting the air suction amount of the pressure dissolved air tank and/or the ejector, bubbles with smaller diameter can be obtained;
(4) the diffusion section of the ejector has a cavitation effect, and instantaneously generated high temperature and high pressure can enable bubbles to collapse, so that the particle size of micro-nano bubbles is effectively reduced, and a large number of hydroxyl free radicals are generated, thereby mineralizing organic matters in water, degrading dye wastewater in a water tank and the ejector, solving the problems of deep chromaticity, high COD (chemical oxygen demand) and difficult degradation of the dye wastewater, and having better application value.
Drawings
Fig. 1 shows a schematic structural diagram of a micro-nano bubble generating device;
fig. 2 shows a schematic structural view of the ejector;
fig. 3 shows the size and particle size distribution of the micro-nano bubbles in example 1;
FIG. 4 shows the degradation efficiency of methylene blue at pH 3, 7 and 9 in example 2 and comparative examples 1-2;
FIG. 5 shows the degradation efficiency of methylene blue at different temperatures in examples 3 to 5;
FIG. 6 shows the TOC removal of methylene blue at 40 ℃ in example 5;
FIG. 7 shows the degradation efficiency of methylene blue in examples 6 to 7 under the conditions of 2g/L sodium sulfate and no sodium sulfate, respectively;
FIG. 8 shows the COD removal rate of methylene blue in example 6 under 2g/L sodium sulfate conditions.
The reference numbers illustrate:
1-gas-liquid mixing pump;
11-a negative pressure gauge;
12-gas flow meter I;
2-pressure dissolved air tank;
21-an exhaust valve;
3-an ejector;
31-a nozzle;
32-a suction chamber;
33-a throat;
34-a diffuser pipe;
4-a water tank;
5-a pressure gauge;
6-liquid flow meter;
7-gas flowmeter II.
Detailed Description
The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.
In the present invention, it should be noted that the terms "connected" and "mounted" are used in a broad sense, and may be mechanically connected through a loose joint, a direct connection, or through other media. Those skilled in the art can understand the meaning of these terms in the present invention according to actual situations.
The pipe fittings consumption materials in the invention can be understood in a broad sense, for example, the valves can adopt a ball valve, a stop valve and a gate valve; the flow meter may be a rotameter, an electronic flow meter, a gear flow meter, etc., and those skilled in the art will understand that these terms are meant in the present invention according to actual situations.
The inventor finds that the common wastewater treatment mode in the prior art has defects in the aspect of dye wastewater treatment, and the micro-nano bubble generation technology can generate beneficial technical effects in the aspect. Wherein, the micro-nano bubbles are micro bubbles with the diameter of 200 nm-50 μm, have the advantages of large specific surface area, long retention time in water, high interface Zeta potential, free radical generation and the like, and are widely applied to the industries of aquaculture, cosmetology and the like.
Micro-nano bubbles are generally generated by a pressurizing and air dissolving method: the air is pressed into the dissolved air tank to make the gas in the water be in a supersaturated state, and then the pressure is suddenly released to separate out micro-nano bubbles. The process of pressing air into the air dissolving tank by the pressurized air dissolving method commonly adopted at present needs to utilize an air compressor, which not only can generate noise and oil pollution, but also has more complex operation; meanwhile, the generated bubbles are mainly applied to an air floatation process, the diameter of the bubbles is relatively large (20-100 mu m), the bubbles are not favorable for stable existence of the bubbles and gas-liquid mass transfer, and the effect in dye wastewater treatment is limited. Therefore, the development of the innovative micro-nano bubble generation device and method can increase the number of micro-nano bubbles and improve the performance of the micro-nano bubbles, which is very important for degrading dye wastewater by the micro-nano bubbles.
One aspect of the present invention is to provide a micro-nano bubble generating device, as shown in fig. 1, the device includes a gas-liquid mixing pump 1, a pressure dissolved air tank 2, an ejector 3 and a water tank 4 connected in sequence by pipelines,
the lower end of the pressure dissolved air tank 2 is provided with a water inlet which is directly connected with a water outlet of the gas-liquid mixing pump 1, and a water outlet at the upper end of the pressure dissolved air tank 2 is connected with the ejector 3; the ejector 3 generates micro-nano bubbles and introduces fluid containing the micro-nano bubbles into the water tank 4; the water tank 4 is directly connected with the water inlet of the gas-liquid mixing pump 1, so that the device forms a circulating system.
In a preferred embodiment, the gas-liquid mixing pump 1 is a self-priming gas-liquid mixing pump so as to directly suck a large amount of air to be mixed with liquid, and meanwhile, the defects of high noise, electric energy consumption, oil pollution and the like caused by the fact that an air compressor supplies air to the pressure dissolved air tank 2 are avoided.
In a further preferred embodiment, a negative pressure gauge 11 is further installed at the water inlet of the gas-liquid mixture pump 1 to monitor the suction condition at the inlet of the gas-liquid mixture pump 1 and the operating state of the gas-liquid mixture pump 1.
In a further preferred embodiment, water in the water tank 4 is directly poured into the gas-liquid mixing pump 1, the gas-liquid mixing pump 1 lifts the water into a pipeline, and meanwhile, a gas flowmeter I12 is installed at a gas suction port of the gas-liquid mixing pump 1, so that the flow of the gas inlet can be conveniently adjusted as required to control the quantity of micro-nano bubbles.
In a further preferred embodiment, a valve is connected in a pipeline connecting the water inlet of the gas-liquid mixing pump 1 and the water tank 4, and the valve is matched with the negative pressure gauge 11 and used for controlling the negative pressure state in the pressure dissolved air tank 2.
In a preferred embodiment, an exhaust valve 21 is installed at the top of the pressure dissolved air tank 2 to exhaust the excessive gas after the gas and the liquid are mixed.
In a further preferred embodiment, a hose may be connected at the outlet of the air outlet valve 21 to drain the excess foam generated back into the water tank 4 when there is foaming material in the liquid.
In a preferred embodiment, the water outlet pipeline of the pressure dissolved air tank 2 is divided into two branches: one pipeline, branch 1, is connected with an ejector 3, preferably a valve, and the other pipeline, branch 2, is connected with a valve, a pressure gauge 5 and a liquid flowmeter 6. And valves on the branch 1 and/or the branch 2 are used for regulating the pressure and the flow of the branch 1 and the branch 2.
In the present invention, as shown in fig. 2, the ejector 3 is a device having the following functional structure: the ejector 3 comprises a nozzle 31, an air suction chamber 32, a throat 33 and a diffuser pipe 34, liquid is injected from the nozzle 31, negative pressure is formed in the air suction chamber 32, and gas is sucked into the throat 33 together with the liquid; the liquid drops moving at high speed in the throat 33 collide with the gas, and the gas is accelerated and dispersed; after entering the diffuser pipe 34, the flow rate is reduced, the pressure is increased, the gas is compressed into micro-nano bubbles, and the gas phase and the liquid phase are sprayed out in a fluid form containing the micro-nano bubbles.
In a preferred embodiment, a gas flow meter II 7 is installed at the suction chamber 32 of the ejector 3, so as to adjust the flow rate of the intake air as required.
In the prior art, the diameter of the micro-nano bubbles generated by the jet device is relatively large, compared with the bubbles with small diameter, the capacities of dissolving oxygen, generating free radicals by the bubbles with large diameter and the like are small, and the application of the micro-nano bubbles in dye wastewater treatment is limited. In order to solve the problem, the inventor of the present invention finds, through intensive research, that micro-nano bubbles with small diameters are mostly obtained by regulating the suction amount in the gas-liquid mixing pump 1 and the ejector 3.
In the invention, the ejector 3 at the branch 1 has double effects of releasing gas-liquid mixture and pressurizing and breaking bubbles. The air suction amount of the ejector 3 is too large, and because the sucked gas is not dissolved into water, more micro-nano bubbles cannot be formed, and the bubbles generated by the 34 sections of the diffuser pipe can be impacted, so that the yield of the micro-nano bubbles is greatly reduced, and the effect of pressurizing and dissolving the gas by the gas-liquid mixing pump 1 is influenced. Therefore, the air suction amount of the ejector 3 can be properly reduced, and the micro-nano bubble yield is improved.
If the air suction amount of the gas-liquid mixing pump 1 is too small, the yield of the micro-nano bubbles is low; if the air suction amount of the air-liquid mixing pump 1 is too large, although the yield of the micro-nano bubbles can be theoretically improved, the dissolving capacity of air in water is reduced. Therefore, it is necessary to adjust the intake air amount of the air-liquid mixing pump 1 reasonably to balance the relationship between the bubble particle diameter and the number of bubbles.
Therefore, in the invention, the ratio of the air suction volume of the ejector to the flow of the branch 2 is set to be 1: 200-1: 350, preferably between 1: 250-1: 300, respectively;
setting the ratio of the suction volume of the gas-liquid mixing pump 1 to the flow of the branch 2 to be 1: 8-1: 12, preferably between 1: 9-1: 10, the particle size effect of the generated micro-nano bubbles is best.
The micro-nano bubble generating device can generate nano bubbles with the diameter of more than 100-300 nm, and the diameters of the nano bubbles are smaller than those of bubbles generated by a common air floating device, and the bubbles can stably exist for a longer time, so that the gas-liquid mass transfer rate is greatly improved.
In another aspect of the present invention, there is provided a method for generating micro-nano bubbles, the method including the steps of:
step 1, connecting a gas-liquid mixing pump, a pressure dissolved air tank, an ejector and a water tank in sequence through pipelines to form a micro-nano bubble generating device capable of performing fluid circulation;
specifically, a water inlet of the pressure dissolved air tank is directly connected with a gas-liquid mixing pump, a water outlet of the pressure dissolved air tank is connected with an ejector, fluid is ejected into a water tank by the ejector, and the water tank is connected with a water inlet of the gas-liquid mixing pump to form a fluid circulation system.
And 2, adding liquid into the water tank, starting each functional component in the micro-nano bubble generating device, and adjusting the air inflow in the gas-liquid mixing pump and the ejector to generate micro-nano bubbles meeting the requirements.
Specifically, the air is inhaled to the gas-liquid mixing pump, makes and gets into pressure dissolved air tank after the liquid that lets in by the water tank and inspiratory air intensive mixing, forms high-pressure gas-liquid mixture, gets into the ejector afterwards in, the room of breathing in of ejector can form the negative pressure to make the bubble release, diffusion pipeline section behind the room of breathing in has the supercharging effect can break into more tiny bubble promptly micro-nano bubble with the bubble that releases, through the outlet pipe blowout.
In still another aspect of the present invention, there is provided a wastewater treatment apparatus, wherein the wastewater is organic wastewater, preferably dye wastewater.
Preferably, the wastewater treatment device and the micro-nano bubble generation device have the same structure, wherein liquid in the wastewater treatment device is wastewater.
In another aspect of the present invention, a wastewater treatment method is provided, preferably, the wastewater treatment method is performed by the above wastewater treatment apparatus, that is, micro-nano bubbles are applied to dye wastewater treatment. Specifically, each functional component in the wastewater treatment device is connected to form the wastewater treatment device capable of performing fluid circulation; and introducing wastewater into the water tank, and starting the wastewater treatment device to treat the wastewater. The wastewater treatment device generates micro-nano bubbles in wastewater, gas-liquid interfaces disappear at the moment that the micro-nano bubbles collapse, chemical energy accumulated on the interfaces is released suddenly to excite and generate free radicals, the free radicals are mainly hydroxyl free radicals, and dissolved oxygen of a water body is in a supersaturated state in the reaction process, can be combined with the hydroxyl free radicals to generate more kinds of free radicals, can degrade pollutants without selectivity, and cannot generate secondary pollution.
In a preferred embodiment, the wastewater is a dye wastewater, preferably a cationic dye wastewater, such as a methylene blue dye wastewater.
In the micro-nano bubble application process, the degradation process of waste water can produce a series of intermediate products, the intermediate products are gathered along with the floating of the micro-nano bubbles, the viscosity is high, the surface tension of the water surface is reduced, a stable foam layer is formed, the foams can greatly influence the quantity and the stability of the micro-nano bubbles, and therefore measures must be taken to eliminate the foams on the water surface or reduce the surface tension, the foams are prevented from being gathered and formed, and the yield of free radicals is improved.
One way to reduce the foam on the wastewater surface is to add an anti-foaming agent to the system. In the invention, defoaming agent tributyl phosphate, organic silicon defoaming agent, polyether defoaming agent and polyether compound organic silicon defoaming agent are adopted to eliminate foam generated in the wastewater treatment process, and polyether compound organic silicon defoaming agent is preferably adopted.
The organic silicon defoaming agent has strong foam inhibition capability but poor water solubility, and is easy to accumulate on the water surface to cause secondary pollution; the polyether defoamer has good water solubility, but has limited foam inhibition time and relatively large addition amount. And the tributyl phosphate antifoaming agent has strong toxicity and is inconvenient to operate. Therefore, the invention preferably adopts the defoaming agent of polyether compound organic silicon, combines the advantages of the organic silicon defoaming agent and the polyether defoaming agent, reduces the dosage of the defoaming agent on one hand, and can slowly dissolve the defoaming agent in the water body on the other hand, thereby not causing secondary pollution or even greatly improving the COD of the system.
Furthermore, the invention also reduces the floating foam amount and improves the treatment effect by changing the concentration, the pH value, the reaction temperature and the like of different defoaming agents.
The inventor finds that the pH value of the dye wastewater is in positive correlation with the foaming degree through research. Under acidic conditions, the dye molecule is heavily coated with H+And the micro-nano bubbles generate charged electrons OH in the degradation process, and the free radicals are easy to attract positive charges, so that the pH value of the system is slowly increased, and meanwhile, dye molecules are mineralized. Under alkaline conditions, the dye molecules are surrounded by a large number of OH groups-Surrounding, free radicals repel negatively charged OH "causing a large number of bubbles to dissolve out, creating foam, and failing to mineralize the dye molecules. In the present invention, the optimum reaction pH is 2 to 5, preferably 3 to 4.
The inventor also finds that the system decolorization rate can be improved along with the rise of the reaction temperature, wherein the decolorization rate at 20-40 ℃ is improved most. The temperature rise accelerates the rising rate and the collapse speed of the micro-nano bubbles, more free radicals are generated, the degradation of dye molecules is facilitated, the temperature rise is higher than 40 ℃, the dissolved oxygen of the system is lower, the oxidative degradation effect of the system can be weakened, and therefore the decolorization rate is lower than the promotion degree of 30 ℃. Therefore, in the invention, the reaction temperature is 20-40 ℃, and preferably 20-30 ℃.
Further, the present inventors have found that the higher the temperature is, the lower the dissolved oxygen in water is, and the more the bubbles are dissolved out easily, and therefore, the more the defoaming agent is required to improve the treatment effect, and the concentration of the defoaming agent required is positively correlated with the reaction temperature. When the reaction temperature is between 20 and 40 ℃, the volume concentration of the corresponding defoaming agent is between 0.00045 and 0.005 percent, and preferably between 0.00075 and 0.003 percent.
The inventor also finds that the reaction foaming phenomenon is inhibited by adding a proper amount of salt into the dye wastewater, and further the wastewater treatment effect is improved. The salt is selected from soluble sulfate, soluble chloride or soluble nitrate, preferably soluble sulfate such as sodium sulfate.
Further, the concentration of the salt is between 0.5 and 5g/L, preferably between 1 and 3 g/L. The salt with the concentration within the range can reduce the pressure difference between the bubbles, so that the bubbles are more stable and are not easy to coalesce, and the number of dispersed bubbles is correspondingly increased, thereby improving the yield of free radicals, promoting the mineralization of dye molecules and improving the treatment effect.
Meanwhile, as mentioned above, the jet device is adopted to generate micro-nano bubbles, the jet device can crush the bubbles after decompression and release, the particle size of the bubbles is reduced, and the generation of foam can be greatly relieved; and the redundant foam can be discharged out of the tank body through an exhaust valve of the pressure dissolved air tank. Therefore, the micro-nano bubbles are stable in the process of degrading wastewater, and the efficiency of generating free radicals cannot be influenced.
It is worth noting that when the gas-liquid mixture passes through the air suction chamber, the local pressure of the liquid is lower than the critical pressure, so that the bubbles in the liquid are rapidly expanded, the water flow carries cavitation bubbles to flow through the downstream diffusion pipe section, the cavitation bubbles are collapsed due to the increase of the pressure, a cavitation effect is generated, and a certain degradation effect can be generated on the wastewater due to the high temperature and the high pressure generated by the cavitation effect. That is, in the invention, the dye wastewater can be degraded in the water tank and the ejector simultaneously, thereby improving the treatment effect of the wastewater.
Examples
Example 1 preparation of micro-nano bubbles
1. The pipeline is connected with a gas-liquid mixing pump, a pressure dissolved air tank, a jet device and a water tank in sequence to form a nano micro bubble generating device capable of performing fluid circulation, and pure water is injected into the water tank; wherein, the outlet pipe way of pressure dissolved air jar divides into two: one branch pipeline, namely the branch 1, is connected with an ejector, and the other branch pipeline, namely the branch 2, is connected with a valve, a pressure gauge and a liquid flowmeter;
2. and starting each functional component in the micro-nano bubble generating device, and adjusting the air inflow in the gas-liquid mixing pump and the ejector to generate fluid containing micro-nano bubbles.
Wherein, the ratio of ejector inspiration capacity and branch 2 flow is 1: 250, setting the ratio of the suction volume of the gas-liquid mixing pump to the flow of the branch 2 to be 1: 9.
a water sample with a certain volume is taken out from a water tank and filled in a glass bottle, after long-distance transportation for 3-4 h, a nanosight NS500 nanoparticle tracking analyzer is adopted to analyze the size and the particle size distribution of bubbles, and the result is shown in figure 3.
As can be seen from FIG. 3, a large amount of nano bubbles between 100nm and 300nm are uniformly dispersed in the water sample, which indicates that the effect of reducing the diameter of the bubbles can be really achieved by the cavitation effect of the ejector by adopting the air inflow in the gas-liquid mixing pump and the ejector set in the invention.
Example 2 wastewater treatment (pH 3)
1. A gas-liquid mixing pump, a pressure dissolved air tank, an ejector and a water tank are sequentially connected by pipelines to form a wastewater treatment device capable of performing fluid circulation, 6mg/L methylene blue aqueous solution is injected into the water tank, and the pH value of the aqueous solution is adjusted to be 3; wherein, the outlet pipe way of pressure dissolved air jar divides into two: one branch pipeline, namely the branch 1, is connected with an ejector, and the other branch pipeline, namely the branch 2, is connected with a valve, a pressure gauge and a liquid flowmeter;
2. starting all functional components in the wastewater treatment device, adjusting the air input in the gas-liquid mixing pump and the ejector, and performing wastewater treatment at room temperature. Wherein, the ratio of ejector inspiration capacity and branch 2 flow is 1: 250, setting the ratio of the suction volume of the gas-liquid mixing pump to the flow of the branch 2 to be 1: 9.
example 3 wastewater treatment (temperature + antifoam)
The procedure for methylene blue wastewater treatment was the same as in example 2 except that the treatment temperature of the methylene blue aqueous solution was further limited to 20 ℃ and the defoaming agent concentration was 0.00075%.
Wherein the adopted defoamer is polyether compound organic silicon defoamer (DT-882D of Schw chemical technology Co., Ltd., Guangdong Fushan city).
Example 4 wastewater treatment (temperature + antifoam)
The methylene blue wastewater treatment procedure was the same as in example 3 except that the treatment temperature of the methylene blue aqueous solution was limited to 30 ℃ and the concentration of the antifoaming agent was 0.00175%.
Example 5 wastewater treatment (temperature + antifoam)
The methylene blue wastewater treatment procedure was the same as in example 3 except that the treatment temperature of the methylene blue aqueous solution was limited to 40 ℃ and the concentration of the antifoaming agent was 0.003%.
Example 6 wastewater treatment (salt treatment)
The methylene blue wastewater treatment procedure is the same as that of example 2, except that the treatment temperature of the methylene blue aqueous solution is further limited to 40 ℃, and sodium sulfate is added to maintain the concentration of sodium sulfate in the system to be 2 g/L.
Example 7 wastewater treatment (salt-free treatment)
The procedure for methylene blue wastewater treatment was the same as in example 2 except that the temperature for treating the methylene blue aqueous solution was further limited to 40 ℃ and sodium sulfate was not added.
Comparative example
Comparative example 1 wastewater treatment (pH 7)
The methylene blue wastewater treatment procedure was the same as in example 2 except that the aqueous methylene blue solution had a pH of 7.
Comparative example 2 wastewater treatment (pH 9)
The methylene blue wastewater treatment procedure was the same as in example 2 except that the aqueous methylene blue solution had a pH of 9.
Examples of the experiments
Experimental example 1
The treatment effects of the methylene blue aqueous solutions in example 2 and comparative examples 1 to 2 were compared, and the degradation efficiency of methylene blue at pH 3, 7 and 9 in 1h was measured, respectively, and the results are shown in fig. 4.
As can be seen from fig. 4, methylene blue has a significant decolorization effect within 1h at room temperature at pH 3, with a maximum removal rate of 25.68%. Methylene blue hardly degrades under the conditions of pH 7 and pH 9. The reason may be that under acidic conditions, methylene blue molecules are heavily substituted with H+And the micro-nano bubbles generate charged electrons OH in the degradation process, and the free radicals are easy to attract positive charges, so that the pH value of the system is slowly increased, and methylene blue is mineralized. Under alkaline conditions, methylene blue is surrounded by a large amount of OH-Surrounding, free radical and negatively charged OH-Mutual repulsion results in dissolution of a large number of bubbles, foam is generated, and thus methylene blue cannot be mineralized.
Experimental example 2
The results of comparing the treatment effects of the methylene blue aqueous solutions of examples 3 to 5, measuring the methylene blue decolorization rate at different temperatures at 20min intervals, and measuring the TOC (total organic carbon content) of the system at 40 ℃ with the largest amount of the antifoaming agent added are shown in fig. 5 and 6, respectively.
As can be seen from FIG. 5, with the rise of the reaction temperature, the decolorization rate of the system is also improved, wherein the decolorization rate at 40 ℃ is the highest, and the decolorization rate at 20-30 ℃ is improved most.
As can be seen from fig. 6, the TOC removal rate of the system at 40 ℃ can reach more than 60%, and therefore, it can be considered that the antifoaming agent does not additionally increase the total organic content of the whole system.
Experimental example 3
Comparing the treatment effects of the methylene blue aqueous solutions in examples 6 to 7, and respectively measuring the methylene blue decolorization rates; meanwhile, example 6 was subjected to a COD (chemical oxygen demand) test, and the degradation of organic substances in the system after adding sulfate was further determined, and the results are shown in FIGS. 7 and 8.
As can be seen from fig. 7, the addition of sulfate can promote the decolorization of methylene blue, mainly because the addition of salt can reduce the pressure difference between bubbles, so that the bubbles are more stable and less prone to coalescence, and the number of dispersed bubbles is correspondingly increased, thereby increasing the yield of free radicals and promoting the mineralization of methylene blue.
In fig. 8, the removal rate of COD can reach 80%, and it is also proved that the high-concentration salt solution can effectively promote the degradation of the micro-nano bubbles on the organic matters, thereby improving the treatment effect.
The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims (14)

1. A method for wastewater treatment, characterized in that wastewater treatment is performed by a wastewater treatment apparatus, the method comprising the steps of:
step 1), connecting all functional components in the wastewater treatment device to form a wastewater treatment device capable of performing fluid circulation;
step 2), introducing wastewater into the water tank, starting the wastewater treatment device to treat the wastewater,
the wastewater treatment device comprises a gas-liquid mixing pump (1), a pressure dissolved air tank (2), an ejector (3) and a water tank (4) which are sequentially connected by pipelines,
the lower end of the pressure dissolved air tank (2) is provided with a water inlet and is directly connected with a water outlet of the gas-liquid mixing pump (1), and a water outlet at the upper end of the pressure dissolved air tank (2) is connected with the ejector (3); the ejector (3) generates micro-nano bubbles and introduces fluid containing the micro-nano bubbles into the water tank (4); the water tank (4) is directly connected with the water inlet of the gas-liquid mixing pump (1) to form a circulating system,
an exhaust valve (21) is arranged at the top of the pressure dissolved air tank (2);
the water outlet pipeline of the pressure dissolved air tank (2) is divided into two branches: one branch pipeline, namely the branch 1, is connected with an ejector (3), the other branch pipeline, namely the branch 2, is connected with a valve, a pressure gauge (5) and a liquid flowmeter (6),
step 2) comprises adjusting the air inflow in the gas-liquid mixing pump (1) and the ejector (3);
setting the ratio of the air suction volume of the ejector (3) to the flow volume of the branch 2 to be 1: 200-1: 350 of the first time;
setting the ratio of the suction volume of the gas-liquid mixing pump (1) to the flow of the branch 2 to be 1: 8-1: 12.
2. The method of claim 1, wherein the wastewater is an organic wastewater.
3. The method of claim 2, wherein the wastewater is dye wastewater.
4. The method of claim 3, wherein the wastewater is cationic dye wastewater.
5. The method of claim 4, wherein the wastewater is methylene blue dye wastewater.
6. The method of claim 1,
setting the ratio of the air suction volume of the ejector (3) to the flow volume of the branch 2 to be 1: 250-1: 300, respectively;
setting the ratio of the suction volume of the gas-liquid mixing pump (1) to the flow of the branch 2 to be 1: 9-1: between the number 10 of the first and second electrodes,
the branch 1 is also connected with a valve.
7. The method of claim 1, wherein a defoaming agent is added to the wastewater during the treatment, wherein the defoaming agent is selected from tributyl phosphate, a silicone defoaming agent, a polyether defoaming agent, or a polyether compounded silicone defoaming agent.
8. The method of claim 7, wherein the defoamer is a polyether built silicone defoamer.
9. The method according to claim 1, wherein the pH of the wastewater is controlled to 2 to 5 during the treatment of the wastewater.
10. The method according to claim 9, wherein the pH of the wastewater is controlled to 3 to 4 during the wastewater treatment.
11. The method according to claim 1, wherein the treatment temperature of the wastewater is controlled to 20 to 40 ℃ during the wastewater treatment.
12. The method according to claim 11, wherein the treatment temperature of the wastewater is controlled to be 20 to 30 ℃ during the wastewater treatment.
13. The method as claimed in claim 11, wherein the volume concentration of the defoaming agent is 0.00045% -0.005% when the wastewater is treated at a temperature of 20-40 ℃.
14. The method of claim 13, wherein the volume concentration of the corresponding defoaming agent is between 0.00075% and 0.003%.
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