Circulating type photocatalytic oxidation treatment device and method

Abstract

The invention relates to a circulating type photocatalytic oxidation treatment device and method.The circulating type photocatalytic oxidation treatment device comprises a backflow mixing pool, a photocatalytic oxidation reactor and a catalyst concentration separator, a nano catalyst is added into the photocatalytic oxidation reactor, and photocatalytic oxidation degradation is conducted on organic pollutants in water; treated effluent containing the nano-catalyst in the photocatalytic oxidation reactor is injected into a catalyst concentration separator, and the nano-catalyst in the water is repelled in a long range by utilizing an EZ phenomenon generated by a hydrophilic film, so that the catalyst is quickly separated and recycled; and adding the nano-catalyst concentrated and recovered by the catalyst concentration separator into the reflux mixing tank again for recycling, and discharging the treated effluent without the nano-catalyst. The device is reasonable in design, the property that the EZ phenomenon on the hydrophilic surface repels particles in water for a long range is coupled, and the nano-catalyst for treating the effluent through photocatalytic oxidation is rapidly separated and recycled.

Description

Technical Field

[0001] The invention relates to a circulating photocatalytic oxidation treatment device and method. Background Art

[0002] Photocatalytic oxidation technology is an emerging environmental pollution control technology that can be used to treat slightly polluted drinking water, printing and dyeing wastewater, papermaking wastewater and landfill leachate. It has the technical characteristics of low cost, easy operation and clean environmental protection. Despite this, the large-scale application of this technology in actual environmental governance, especially in water pollution control, faces many challenges. Although nanocatalysts are favored for their large specific surface area and excellent catalytic activity, the rapid separation and effective recovery of nanoparticles put into water after pollutant degradation have become the main obstacles to the practical application of photocatalytic oxidation technology. These nanocatalysts that are difficult to effectively separate from water may be enriched in natural water bodies, which in turn has potential negative effects on aquatic ecosystems, including water pollution, inhibition of aquatic biological growth and destruction of ecological balance. Therefore, the application of photocatalytic oxidation technology is often limited to laboratory scale.

[0003] At present, the separation and recovery of nanocatalysts mainly rely on traditional physical and chemical methods. Although physical methods such as filtration, centrifugation, flotation and membrane separation can directly separate catalysts, they are limited by the size of nanoparticles, and the separation and recovery effect is not ideal. They are also prone to produce residual sludge or cause membrane surface pollution. Chemical methods achieve precipitation separation by adding coagulants or adjusting the pH of the solution, but this may affect the performance and stability of the catalyst. At the same time, the separated catalyst is difficult to recycle and reuse.

[0004] In recent years, a large number of studies have attempted to recycle and reuse nanocatalysts by introducing magnetic materials or changing the surface charge state of materials. However, these methods are complex to operate, require high stability of the catalyst, and may have an adverse effect on the photocatalytic oxidation reaction. In order to solve the problem of nanocatalysts being difficult to recycle and reuse, a large number of studies have also used the loading method to fix nanocatalysts on carriers such as glass, porous materials, and thin films. However, the specific surface area of ​​the fixed catalyst becomes smaller, the catalytic activity decreases, and the treatment effect is not as good as the traditional suspension photocatalytic oxidation process. In addition, there are problems such as catalyst shedding and loss during use, and unstable treatment effect. Summary of the invention

[0005] The present invention makes improvements on the problems existing in the above-mentioned prior art, that is, the technical problem to be solved by the present invention is to provide a circulating photocatalytic oxidation treatment device and method.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a circulating photocatalytic oxidation treatment device, comprising a reflux mixing tank, a photocatalytic oxidation reactor and a catalyst concentration separator, wherein a nanocatalyst is added to the photocatalytic oxidation reactor; the water outlet of the reflux mixing tank is connected to the liquid input end of the photocatalytic oxidation reactor, the liquid output end of the photocatalytic oxidation reactor is connected to the liquid input end of the catalyst concentration separator, a hydrophilic membrane is arranged in the catalyst concentration separator, and the concentrate discharge port of the catalyst concentration separator is connected to the reflux mixing tank.

[0007] Furthermore, the photocatalytic oxidation reactor is a tubular photocatalytic oxidation reactor.

[0008] Furthermore, a xenon lamp or an ultraviolet lamp is placed in the middle of the photocatalytic oxidation reactor.

[0009] Furthermore, the hydrophilic membrane in the catalyst concentration separator is obtained by coating a 5% Nafion solution on a glass tube.

[0010] Another technical solution adopted by the present invention is: a cyclic photocatalytic oxidation treatment method, comprising the following steps: first, water is introduced into the photocatalytic oxidation reactor from a reflux mixing tank, nanocatalysts are added into the photocatalytic oxidation reactor, and organic pollutants in the water are photocatalytically oxidized and degraded; secondly, the treated water containing the nanocatalyst in the photocatalytic oxidation reactor is injected into a catalyst concentration separator, and the EZ phenomenon generated by the hydrophilic membrane is utilized to repel the nanocatalyst in the water over a long distance, thereby realizing rapid separation and recovery of the catalyst; finally, the nanocatalyst recovered from the concentrated catalyst concentration separator is added back into the reflux mixing tank for cyclic use, and the treated water without the nanocatalyst is discharged.

[0011] Furthermore, the nanocatalyst is P25 TiO2.

[0012] Furthermore, the pH value of the solution to be treated is adjusted to 8 in the reflux mixing tank.

[0013] Compared with the prior art, the present invention has the following effects: the present invention has a reasonable design, couples the hydrophilic surface EZ phenomenon to repel particles in the water over a long distance, and can be widely used in fields such as water purification and water pollution control that require photocatalytic oxidation degradation of difficult-to-degrade organic matter in water by quickly separating the nanocatalysts discharged from the water and recycling them. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of an embodiment of the present invention; Figure 2 are the SEM results of the nanocatalyst before and after recycling; Figure 3 is the XRD result of nanocatalyst before and after recycling; Figure 4 It is a multiple cycle processing effect.

[0015] In the figure: 1- reflux mixing tank; 2- photocatalytic oxidation reactor; 3- catalyst concentration separator; 4- catalytic reaction light source; 5- hydrophilic membrane. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0018] The hydrophilic surface exclusion-zone (EZ) phenomenon is a long-range interface phenomenon. When a hydrophilic material comes into contact with a particle suspension, all particles at the solid-liquid interface will be repelled and move away from the hydrophilic surface due to the long-range interface effect between the hydrophilic surface and water. Since this repulsion process occurs spontaneously and does not produce by-products, it is green and efficient.

[0019] like Figure 1As shown, the present invention is a circulating photocatalytic oxidation treatment device that couples the hydrophilic surface EZ phenomenon and the photocatalytic oxidation technology, comprising a reflux mixing tank 1, a photocatalytic oxidation reactor 2 and a catalyst concentration separator 3, wherein a nanocatalyst is added into the photocatalytic oxidation reactor 2; the water outlet of the reflux mixing tank 1 is connected to the liquid input end of the photocatalytic oxidation reactor 2, the liquid output end of the photocatalytic oxidation reactor 2 is connected to the liquid input end of the catalyst concentration separator 3, a hydrophilic membrane 5 is arranged in the catalyst concentration separator 3, and the concentrate discharge port of the catalyst concentration separator 5 is connected to the reflux mixing tank 1. During operation, the reflux mixing tank 1 feeds water into the photocatalytic oxidation reactor 2, and the photocatalytic oxidation reactor 2 performs photocatalytic oxidation degradation on organic pollutants in the water by adding nanocatalysts; the treated effluent containing the nanocatalysts is injected into the catalyst concentration separator 2, and the EZ phenomenon produced by the hydrophilic membrane 5 (perfluorosulfonic acid Nafion) is utilized to repel the nanocatalysts in the water over a long distance, thereby realizing rapid separation and recovery of the catalyst; finally, the nanocatalysts recovered from the concentrated catalyst concentration separator 3 are added back into the reflux mixing tank 1 for recycling, and the treated effluent without the nanocatalysts is discharged.

[0020] In this embodiment, the photocatalytic oxidation reactor 2 is a tubular photocatalytic oxidation reactor made of quartz glass, in the middle of which a xenon lamp or an ultraviolet lamp (ie, a catalytic reaction light source 4) can be placed.

[0021] In this embodiment, the hydrophilic membrane 5 in the catalyst concentration separator 3 is obtained by coating a 5% Nafion solution on a glass tube in the catalyst concentration separator. It should be noted that in actual use, multi-stage concentration and separation of nanocatalysts can be achieved by stacking glass tubes with different diameters according to processing requirements.

[0022] In this embodiment, the reflux mixing tank 1 is a reactor for fully mixing the incoming water and the concentrated and recovered nanocatalyst, where the concentration of the nanocatalyst and the pH value of the solution can be adjusted according to the properties of the organic pollutants to be treated.

[0023] In this embodiment, a cyclic photocatalytic oxidation treatment method that couples the hydrophilic surface EZ phenomenon and the photocatalytic oxidation technology includes the following steps: first, a reflux mixing pool 1 feeds water into the photocatalytic oxidation reactor 2, and a nanocatalyst is added to the photocatalytic oxidation reactor 2 to photocatalytically oxidize and degrade organic pollutants in the water; secondly, the treated water containing the nanocatalyst in the photocatalytic oxidation reactor 2 is injected into the catalyst concentration separator 3, and the EZ phenomenon generated by the hydrophilic membrane 5 is used to repel the nanocatalyst in the water over a long distance, thereby realizing rapid separation and recovery of the catalyst; finally, the nanocatalyst concentrated and recovered by the catalyst concentration separator 3 is added back into the reflux mixing pool 1 for cyclic use, and the treated water without the nanocatalyst is discharged.

[0024] In this embodiment, the nanocatalyst is P25 TiO2. P25 TiO2 is the most commonly used commercial nanocatalyst. Therefore, the present invention uses P25 (mixed crystal phase TiO2, particle size 25 nm, density 0.13 g / cm 3 ) as a representative of nanocatalysts for separation, recovery and reuse. P25 has good dispersibility and stability under alkaline conditions, so the pH value of the solution to be treated needs to be adjusted to 8 in the reflux mixing tank.

[0025] In this embodiment, after passing through the catalyst concentration separator, the recovery rate of P25 can reach 99.8%. The recovered P25 was characterized by SEM and XRD ( Figure 2 and Figure 3 ), and no changes were found in particle size and crystal form. By recycling P25, methyl orange, a representative of azo dyes in water, was subjected to multiple photocatalytic oxidation treatments. It was found that after multiple recycling, P25 still maintained excellent photocatalytic oxidation performance. After 10 cycles, the removal rate of methyl orange by P25 was only slightly lower than the removal rate at the first use by 2%, and the recycling treatment effect was relatively stable ( Figure 4 In addition, the present invention also studies the nanocatalyst tungsten oxide (particle size 360 ​​nm, density 7.27 g / cm 3 ) and zirconium oxide (particle size 380 nm, density 5.85 g / cm 3 ) was used for the above treatment, and the results showed that the recovery rate of tungsten oxide was 99.81%, and the recovery rate of zirconium oxide was 99.95%. The recovery effect of the nanocatalyst is excellent, the loss of the catalyst is very small, and the recycling and reuse does not affect the properties of the catalyst itself and the treatment effect.

[0026] The present invention couples the hydrophilic surface EZ phenomenon to repel particles in the water over a long distance, and quickly separates the nanocatalysts discharged from the photocatalytic oxidation treatment, and recycles them. The present invention can be widely used in the fields of water purification and water pollution control where it is necessary to photocatalytically oxidize and degrade refractory organic matter in water. Its main advantages are reflected in the following three points: (1) The present invention has a fast separation and concentration speed for nanocatalysts (≤10 min) and a high recovery efficiency (>99.8%), which can effectively solve the problem of difficulty in recovering and recycling nanocatalysts in the current photocatalytic oxidation process; (2) The present invention does not affect the properties and performance of the recovered nanocatalyst. The nanocatalyst can be recycled and reused multiple times, and the treatment effect on organic matter is relatively stable, which can save the amount of catalyst used and the number of regeneration treatments; (3) The present invention does not require the use of a large amount of chemical agents, will not produce secondary pollutants, and does not require the use of complex processes. The operation process is simple and it is a green and efficient water treatment method.

[0027] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by one-piece molding using a casting process) (except when it is obviously impossible to use an one-piece molding process).

[0028] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0029] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A circulating photocatalytic oxidation treatment device, characterized in that: It comprises a reflux mixing tank, a photocatalytic oxidation reactor and a catalyst concentration separator, wherein a nanocatalyst is added into the photocatalytic oxidation reactor; a water outlet of the reflux mixing tank is connected to a liquid input end of the photocatalytic oxidation reactor, a liquid output end of the photocatalytic oxidation reactor is connected to a liquid input end of the catalyst concentration separator, a hydrophilic membrane is arranged in the catalyst concentration separator, and a concentrate discharge port of the catalyst concentration separator is connected to the reflux mixing tank.

2. A circulating photocatalytic oxidation treatment device according to claim 1, characterized in that: The photocatalytic oxidation reactor is a tubular photocatalytic oxidation reactor.

3. A circulating photocatalytic oxidation treatment device according to claim 1 or 2, characterized in that: A xenon lamp or an ultraviolet lamp is placed in the middle of the photocatalytic oxidation reactor.

4. A circulating photocatalytic oxidation treatment device according to claim 1, characterized in that: The hydrophilic membrane in the catalyst concentration separator is obtained by coating a 5% Nafion solution on a glass tube.

5. A cyclic photocatalytic oxidation treatment method, characterized in that: The method comprises adopting a circulating photocatalytic oxidation treatment device as described in any one of claims 1 to 4, comprising the following steps: first, water is introduced into a photocatalytic oxidation reactor from a reflux mixing tank, nanocatalysts are added into the photocatalytic oxidation reactor, and organic pollutants in the water are photocatalytically oxidized and degraded; secondly, treated water containing nanocatalysts in the photocatalytic oxidation reactor is injected into a catalyst concentration separator, and the EZ phenomenon generated by the hydrophilic membrane is utilized to repel the nanocatalysts in the water over a long distance, thereby realizing rapid separation and recovery of the catalyst; finally, the nanocatalysts recovered from the concentrated catalyst concentration separator are added back into the reflux mixing tank for cyclic use, and the treated water without the nanocatalysts is discharged.

6. A cyclic photocatalytic oxidation treatment method according to claim 5, characterized in that: The nano catalyst is P25 TiO2.

7. A cyclic photocatalytic oxidation treatment method according to claim 5, characterized in that: The pH value of the solution to be treated is adjusted to 8 in the reflux mixing tank.

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