阅读说明：本技术 一种丙酮强化光降解废水中多环芳香烃的方法 (Method for degrading polycyclic aromatic hydrocarbon in wastewater by acetone enhancement light ) 是由 徐焕志 姚冰 吴亦茹 高佳俊 张保平 于 2019-09-26 设计创作，主要内容包括：本发明涉及废水处理领域,尤其涉及一种丙酮强化光降解废水中多环芳香烃的方法。包括以下步骤：向含有多环芳香烃的废水中通入氧气一定时间,得到含氧废水；然后向含氧废水中加入一定量的丙酮后,得到前处理液,将前处理液通入内部设置有多层光催化板的容器中,然后对容器中照射紫外光一定时间,得到降解废水。本发明是为了克服现有技术中的光降解废水中多环芳香烃的方法所用到的光催化效率较低,其使用的紫外光强度极高容易对人造成伤害,同时光催化剂添加量需要较高的缺陷,具有能够在低紫外光强度的条件下快速降解水中多环芳香烃的优点,同时光催化促进剂添加含量低且光催化效率不会随时间推移而降低。(The invention relates to the field of wastewater treatment, in particular to a method for degrading polycyclic aromatic hydrocarbon in wastewater by acetone enhancement light. The method comprises the following steps: introducing oxygen into wastewater containing polycyclic aromatic hydrocarbon for a certain time to obtain oxygen-containing wastewater; and then adding a certain amount of acetone into the oxygen-containing wastewater to obtain a pretreatment liquid, introducing the pretreatment liquid into a container with a plurality of layers of photocatalytic plates arranged inside, and irradiating ultraviolet light in the container for a certain time to obtain the degraded wastewater. The method for degrading polycyclic aromatic hydrocarbons in wastewater by light in the prior art has the advantages that the method is used for overcoming the defects that the photocatalysis efficiency is low, the intensity of ultraviolet light used by the method is extremely high, the damage to people is easily caused, and the addition amount of the photocatalyst is high, the method can be used for rapidly degrading the polycyclic aromatic hydrocarbons in water under the condition of low ultraviolet light intensity, and meanwhile, the addition content of the photocatalyst promoter is low, and the photocatalysis efficiency cannot be reduced along with the lapse of time.)

1. A method for strengthening the degradation of polycyclic aromatic hydrocarbon in wastewater by acetone is characterized by comprising the following steps:

(1) micro-oxidation treatment: introducing oxygen into wastewater containing polycyclic aromatic hydrocarbon for a certain time to obtain oxygen-containing wastewater;

(2) preparation of a pretreatment liquid: adding a certain amount of acetone into the oxygen-containing wastewater to obtain a pretreatment liquid;

(3) ultraviolet light catalysis: introducing the pretreatment liquid into a container with a plurality of layers of photocatalytic plates arranged inside, and irradiating ultraviolet light in the container for a certain time to obtain degraded wastewater;

the surface of the photocatalytic plate contains a certain amount of metallic silver and rare earth elements.

2. The method of claim 1, wherein the oxygen is introduced at 500 ~ 1500mL/min for 0.5 ~ 3h in step (1).

3. The method of claim 1, wherein the acetone content in the step (2) is 300 ~ 1500 ppm.

4. The method for enhancing degradation of polycyclic aromatic hydrocarbons in wastewater by acetone according to claim 1, wherein the photocatalytic plate in step (3) is prepared by the following steps:

(S.1) preparing the rare earth-containing aerogel: stirring and mixing tetraethoxysilane, rare earth powder, an acid catalyst and an absolute ethyl alcohol solvent, standing, heating and aging to obtain wet sol, and performing supercritical treatment to obtain rare earth aerogel;

(S.2) depositing metallic silver on the surface: crushing the rare earth aerogel, adding the crushed rare earth aerogel into a silver ammonia solution, uniformly mixing, then dripping a glucose solution into the mixture, stirring the mixture in a water bath for a certain time, and filtering and drying the mixture to obtain rare earth aerogel powder with metal silver deposited on the surface;

(S.3) sintering and forming: the rare earth aerogel powder with the surface deposited with the metal silver is subjected to uniaxial compression to obtain a slab, and then the slab is sintered at high temperature to obtain the photocatalytic plate.

5. The method of claim 4, wherein the mass ratio of tetraethoxysilane to rare earth powder in the step (S.1) is 100 (1 ~ 5), the pH of the solution is adjusted to 2 ~ 3.5.5 by the acid catalyst, and the solution is stirred and reacted for 20 ~ 40 min.

6. The method of claim 4 or 5, wherein the rare earth powder of step (S.1) comprises 20 parts by weight of cerium oxide 20 ~ 35, 10 parts by weight of europium oxide 10 ~ 15, 10 parts by weight of lanthanum oxide 10 ~ 15 and 3 parts by weight of ytterbium oxide 3 ~ 8.

7. The method of claim 6, wherein the aging temperature in the step (S.1) is 65 ~ 70 ℃ and the aging time is 1 ~ 3h, the supercritical temperature is 250 ~ 280 ℃ and the supercritical pressure is 5 ~ 8 MPa.

8. The method for acetone-enhanced photodegradation of polycyclic aromatic hydrocarbons in wastewater according to claim 4, wherein the mass ratio of the rare earth aerogel to the silver ammonia solution in the step (S.2) is (10 ~ 35) to 100, the mass fraction of the glucose solution is 20 ~ 30%, the volume ratio of the silver ammonia solution to the glucose solution is 100 (0.2 ~ 0.5), and the water bath temperature is 60 ~ 65 ℃.

9. The method of claim 4, wherein the uniaxial compression pressure in the step (S.3) is 8 ~ 12MPa, the sintering temperature is 600 ~ 850 ℃, and the sintering atmosphere is nitrogen.

10. The method according to claim 1, wherein the ultraviolet light emission wavelength in step (3) is 254nm, and the irradiation intensity is 120 ~ 150uW/cm to obtain the polycyclic aromatic hydrocarbon in the wastewater²The irradiation time was 10 ~ 30 min.

Technical Field

The invention relates to the field of wastewater treatment, in particular to a method for degrading polycyclic aromatic hydrocarbon in wastewater by acetone enhancement light.

Background

Polycyclic Aromatic Hydrocarbons (PAHs) are compounds having two or more benzene ring structures in the molecule. Polycyclic aromatic hydrocarbons were also the earliest successful chemical carcinogens in animal experiments. Yamagiwa and Ichikawa, Japan scholars, 1915, were induced by polycyclic aromatic hydrocarbons in coal tar. Polycyclic aromatic hydrocarbons have been considered the most major carcinogenic factor before the fifties, and one of the different types of carcinogens after the fifties. However, it still has a very important position in carcinogens in general, because it is still the most carcinogen in quantity and has a very wide distribution. Air, soil, water and plants exist, and 3, 4-benzopyrene is separated from limestone even reaching fifty meters below the stratum. In nature, it is mainly present in coal, petroleum, tar and asphalt, and can also be produced by incomplete combustion of compounds containing elemental carbon. The exhaust gas from automobiles, airplanes and various motor vehicles and the smoke of cigarettes contain various carcinogenic fused ring aromatic hydrocarbons. The open-air incineration (fire and waste) can generate a plurality of fused ring aromatic carcinogens. Smoked, baked and roasted foods can be contaminated with polycyclic aromatic hydrocarbons.

The photocatalytic degradation is a process of degrading pollutants into inorganic substances completely by utilizing radicals with extremely strong activity generated in a reaction system by radiation and a photocatalyst through the processes of addition, substitution, electron transfer and the like between the radicals and organic pollutants.

Due to the characteristic that polycyclic aromatic hydrocarbon is difficult to be chemically and biologically degraded, the traditional method for degrading polycyclic aromatic hydrocarbon is a photodegradation method, but the traditional photodegradation method needs ultraviolet light irradiation with high optical density, so that not only is energy loss large, but also the human body is easily damaged by the high-energy ultraviolet light.

For example, a photocatalytic treatment technique for sewage from a steam plant, which is disclosed in publication No. CN109052764A, includes filtering and photocatalytic treatment techniques, wherein suspended substances in sewage are filtered out, and then the sewage is subjected to photocatalytic treatment by adding a catalyst and using a xenon lamp as a light source, and the photocatalytic oxidation method is a method of generating a reaction group to oxidize and mineralize a harmful compound by using the characteristics of a semiconductor and absorbing photons under the irradiation of light to play a role of the catalyst, so as to decompose the harmful compound into carbon dioxide, water and inorganic salts; the technology can be operated without an additional electron acceptor, the operation condition is easy to control, the oxidation capacity is strong, secondary pollution is avoided, organic pollutants contained in water can be completely degraded into water or carbon dioxide, inorganic pollutants are reduced into harmless substances or oxidized, the needed photocatalyst has the advantages of being non-toxic, cheap, stable and capable of being used repeatedly, the catalytic efficiency is low, the extra-high light intensity is needed, and meanwhile the adding amount of the photocatalyst is high.

Disclosure of Invention

The invention provides a method for strengthening the degradation of polycyclic aromatic hydrocarbon in wastewater by acetone, aiming at overcoming the defects that the photocatalysis efficiency is lower, the used ultraviolet light intensity is extremely high and is easy to cause harm to people, and the addition amount of a photocatalyst is higher in the prior art.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a method for acetone-enhanced photodegradation of polycyclic aromatic hydrocarbons in wastewater, the method comprising the steps of:

(1) micro-oxidation treatment: introducing oxygen into wastewater containing polycyclic aromatic hydrocarbon for a certain time to obtain oxygen-containing wastewater;

(2) preparation of a pretreatment liquid: adding a certain amount of acetone into the oxygen-containing wastewater to obtain a pretreatment liquid;

(3) ultraviolet light catalysis: introducing the pretreatment liquid into a container with a plurality of layers of photocatalytic plates arranged inside, and irradiating ultraviolet light in the container for a certain time to obtain degraded wastewater;

the surface of the photocatalytic plate contains a certain amount of metallic silver and rare earth elements.

The method for degrading polycyclic aromatic hydrocarbon in wastewater comprises the steps of firstly introducing oxygen into the wastewater to greatly improve the oxygen content in the wastewater, then uniformly mixing the oxygen with acetone and carrying out photocatalysis, wherein the acetone in the wastewater reacts with a photocatalysis plate under the action of ultraviolet light to form HO (HO)_xThe free radical can be used as a catalytic promoter to generate free radical oxidation reaction with polycyclic aromatic hydrocarbon in the wastewater, so that the polycyclic aromatic hydrocarbon can be degraded under the condition of low optical density, and the decomposition efficiency of the polycyclic aromatic hydrocarbon can be effectively improved by matching with the oxidation of oxygen. In addition, because the surface of the photocatalytic plate contains a certain amount of metal silver and rare earth elements, the photocatalytic plate has good photosensitive activity and photosensitive excitability, so that the photocatalytic reaction activity can be greatly enhanced, and the photocatalytic effect is greatly improved.

Preferably, in the step (1), the oxygen introducing amount is 500 ~ 1500mL/min and 1500mL/min, and the oxygen introducing time is 0.5 ~ 3 h.

Preferably, the acetone content in step (2) is 300 ~ 1500ppm to 1500 ppm.

The acetone adding amount concentration is ppm level, the decomposition efficiency of polycyclic aromatic hydrocarbon can be effectively improved under the concentration, and the acetone can effectively and completely form HO under the concentration_xFree radicals, which prevent acetone from still being present in the wastewater after photodegradation.

Preferably, the preparation method of the photocatalytic plate in the step (3) is as follows:

(S.1) preparing the rare earth-containing aerogel: stirring and mixing tetraethoxysilane, rare earth powder, an acid catalyst and an absolute ethyl alcohol solvent, standing, heating and aging to obtain wet sol, and performing supercritical treatment to obtain rare earth aerogel;

(S.2) depositing metallic silver on the surface: crushing the rare earth aerogel, adding the crushed rare earth aerogel into a silver ammonia solution, uniformly mixing, then dripping a glucose solution into the mixture, stirring the mixture in a water bath for a certain time, and filtering and drying the mixture to obtain rare earth aerogel powder with metal silver deposited on the surface;

(S.3) sintering and forming: the rare earth aerogel powder with the surface deposited with the metal silver is subjected to uniaxial compression to obtain a slab, and then the slab is sintered at high temperature to obtain the photocatalytic plate.

According to the invention, tetraethoxysilane is used as a carrier to adsorb rare earth powder to generate aerogel containing rare earth components, the aerogel is crushed and dissolved in silver ammonia solution, and glucose solution is added to precipitate single metal silver on the surface of the rare earth aerogel powder. Then the rare earth aerogel powder with metal silver deposited on the surface is sintered to obtain the photocatalytic plate with more pores, so that the wastewater can be catalyzed on the surface of the photocatalytic plate and can enter the pores inside the photocatalytic plate for catalysis, and the catalytic effect is improved.

Meanwhile, because the catalytic components in the photocatalytic plate can be effectively fixed in the plate, the overall catalytic effect is not reduced with the passage of time.

Preferably, the mass ratio of the tetraethoxysilane to the rare earth powder in the step (S.1) is 100 (1 ~ 5), the pH of the solution is adjusted to 2 ~ 3.5.5 by the acid catalyst, and the solution is stirred and reacted for 20 ~ 40min

Preferably, the rare earth powder of step (s.1) includes, in terms of that part by weight, 20 ~ 35 parts of cerium oxide, 10 ~ 15 parts of europium oxide, 10 ~ 15 parts of lanthanum oxide, and 3 ~ 8 parts of ytterbium oxide.

Preferably, the aging temperature in the step (S.1) is 65 ~ 70 ℃, the aging time is 1 ~ 3h, the supercritical temperature is 250 ~ 280 ℃, and the supercritical pressure is 5 ~ 8 MPa.

Preferably, in the step (S.2), the mass ratio of the rare earth aerogel to the silver ammonia solution is (10 ~ 35): 100, the mass fraction of the glucose solution is 20 ~ 30%, the volume ratio of the silver ammonia solution to the glucose solution is 100: (0.2 ~ 0.5), and the water bath temperature is 60 ~ 65 ℃.

Preferably, in step (s.3), the uniaxial compression pressure is 8 ~ 12MPa, the sintering temperature is 600 ~ 850 ℃ and the sintering atmosphere is nitrogen.

Preferably, the ultraviolet light emission wavelength in the step (3) is 254nm, and the irradiation intensity is 120 ~ 150uW/cm²The irradiation time was 10 ~ 30 min.

Drawings

FIG. 1 is a graph showing the concentration time curves of polycyclic aromatic hydrocarbons in example 1 and comparative examples 1 and 2.

Detailed Description

The invention is further described with reference to the drawings and the specific embodiments. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.