Photocatalytic reaction device and sewage treatment method

Abstract

The invention provides a photocatalytic reaction device and a sewage treatment method. The photocatalytic reaction device comprises a premixer, a catalytic oxidation reactor, a postmixer, a solid-liquid separator and a photocatalytic reactor. Iron ions Fe < 3 + > are converted into ferrous ions Fe < 2 + > through backflow of effluent in the catalytic oxidation reactor, backflow of waste residues and photocatalytic reaction, and the method has the advantages of being small in agent adding amount, small in waste residue generation amount, good in treatment effect and low in treatment cost and is suitable for treating refractory sewage.

Description

Technical Field

[0001] The invention belongs to the field of sewage treatment, and specifically relates to a sewage treatment device, in particular to a photocatalytic reaction device and a method for treating sewage using the device. Background Art

[0002] Refractory industrial wastewater refers to industrial wastewater containing organic matter that is difficult to be biodegraded, including polycyclic aromatic hydrocarbons, organophosphorus pesticides, surfactants, organic dyes, etc. The common characteristics of these substances are high toxicity, complex composition, and difficulty in being degraded by microorganisms. At present, low-concentration wastewater or fresh water is often used for treatment after dilution, or pretreatment + advanced oxidation treatment is used before mixing with low-concentration wastewater for treatment. The current processes have the problems of long treatment process, easy impact on sewage treatment system, and inability to achieve stable discharge standards.

[0003] In industrial wastewater treatment plants, wastewater that has undergone biochemical treatment still contains low concentrations of non-biodegradable organic matter, causing the wastewater to fail to meet the requirements of discharge standards. At present, the original process flow is mostly based on the addition of advanced oxidation + biochemical deep treatment to further reduce the organic content. Among them, advanced oxidation units mostly use ozone catalytic oxidation, Fenton and other treatment technologies. The mechanism of Fenton oxidation is to combine a catalyst with an oxidant to produce highly active free radicals (such as OH) in the reaction; then, through addition, substitution, electron transfer, bond breaking, etc. between free radicals and organic compounds, the large molecular weight, difficult-to-degrade organic matter in the water is oxidized and degraded into small molecular substances that are easily biodegradable, and even directly degraded into CO2 and H2O, which is close to complete mineralization. Ferrous ion Fe 2+ Oxidized to iron ion Fe 3+ , iron ion Fe 3+ Sedimentation under moderately alkaline conditions, its flocculation effect can be used to remove some organic matter, and at the same time generate waste slag containing Fe(OH)3 (commonly known as iron sludge waste slag). Fenton oxidation technology has been widely studied due to its simple operation and rapid reaction. However, in practical applications, traditional Fenton oxidation has the problems of large catalyst dosage and large amount of waste slag generated. In particular, the waste slag generated by Fenton oxidation is usually disposed of as hazardous waste, resulting in high treatment costs for Fenton oxidation treatment, all of which affect the wider application of Fenton oxidation technology in industry.

[0004] CN 109020015 A A UV catalytic oxidation wastewater treatment system and method proposes a method for treating wastewater by coupling Fenton oxidation and photocatalysis, which can reduce the amount of Fenton iron sludge produced and improve the treatment effect. However, this method has Fe 3+ Conversion Fe 2+ The disadvantages are low efficiency, large amount of sewage treated by the photocatalytic reactor and high investment.

[0005] Therefore, it is necessary to develop new technologies to solve the technical defects of Fenton iron oxide sludge. Summary of the invention

[0006] In order to overcome the difficulties of the above-mentioned Fenton oxidation catalyst, such as large consumption, large amount of waste residue generated, and high treatment cost, the present invention provides a photocatalytic reaction device and a method for treating sewage using the device, so as to solve the defects of the existing Fenton oxidation technology, such as large amount of reagent dosage, large amount of waste residue generated, and high treatment cost.

[0007] A first aspect of the present invention provides a photocatalytic reaction device, the device comprising:

[0008] Pre-mixer;

[0009] Catalytic oxidation reactor;

[0010] Post mixer;

[0011] solid-liquid separator; and

[0012] Photocatalytic reactor;

[0013] The inlet of the pre-mixer is connected with a water inlet line, a catalyst line and an oxidant line; the outlet of the pre-mixer is connected with the inlet of the catalytic oxidation reactor;

[0014] The first outlet of the catalytic oxidation reactor is communicated with the inlet of the post-mixer, and the inlet of the post-mixer is connected to an alkali adding line;

[0015] The outlet of the post-mixer is connected to the inlet of the solid-liquid separator, the drain outlet of the solid-liquid separator is connected to the drain line, and the slag discharge outlet of the solid-liquid separator is connected to the slag discharge line;

[0016] The slag discharge port of the solid-liquid separator is also connected to the first inlet of the photocatalytic reactor, and the first inlet of the photocatalytic reactor is also connected to the acid addition line;

[0017] The outlet of the photocatalytic reactor is communicated with the inlet of the pre-mixer.

[0018] According to the device of the first aspect, the catalytic oxidation reactor is further provided with a second outlet, the photocatalytic reactor is further provided with a second inlet, and the second inlet of the photocatalytic reactor is connected to the second outlet of the catalytic oxidation reactor.

[0019] According to the device of the first aspect, a pH probe is provided in the catalytic oxidation reactor, and a regulating valve is provided on the acid addition line, and the regulating valve is used to adjust the amount of acid addition to control the pH value in the catalytic oxidation reactor.

[0020] According to the device of the first aspect, a pH probe is provided in the solid-liquid separator, and a regulating valve is provided on the alkali adding line, and the regulating valve is used to adjust the amount of alkali added to control the pH value in the solid-liquid separator.

[0021] The device according to the first aspect, wherein the photocatalyst in the photocatalytic reactor is TiO2; and / or

[0022] An ultraviolet lamp is arranged in the photocatalytic reactor; preferably, the wavelength of the ultraviolet lamp is 185nm and 254nm.

[0023] The second aspect of the present invention provides a method for treating sewage, wherein the method uses the photocatalytic reaction device described in the first aspect to treat sewage, comprising:

[0024] The sewage to be treated is mixed with the catalyst, oxidant, and acidic reflux liquid from the photocatalytic reactor in the pre-mixer and then enters the catalytic oxidation reactor for catalytic oxidation reaction. The sewage after the catalytic oxidation reaction is mixed with the alkaline solution in the post-mixer and then enters the solid-liquid separator for solid-liquid separation.

[0025] The sewage after solid-liquid separation is discharged from the drain outlet, part of the waste residue after solid-liquid separation is discharged from the residue outlet, and the rest is mixed with the acid liquid and returned to the photocatalytic reactor for photocatalytic oxidation reaction. The acidic reflux liquid after the photocatalytic oxidation reaction returns to the pre-mixer.

[0026] According to the method of the second aspect, the reflux ratio of the waste residue is 0.2-20:1, preferably 0.5-10:1.

[0027] According to the method of the second aspect, the catalyst is a reducing metal and / or a reducing metal salt, preferably ferrous sulfate; and / or

[0028] The oxidant is peroxide and / or persulfate, preferably hydrogen peroxide.

[0029] The method according to the second aspect, wherein the pH value in the catalytic oxidation reactor is <6, preferably pH 3-5; and / or

[0030] The pH value in the solid-liquid separator is ≥6, preferably a pH value of 6-9.

[0031] According to the method of the second aspect, the residence time of the sewage in the catalytic oxidation reactor is 5-1200 min, preferably 30-300 min;

[0032] The residence time of the sewage in the solid-liquid separator is 20-1200 min, preferably 30-600 min; and / or

[0033] The residence time of the material in the photocatalytic reactor is 2-600 min, preferably 20-240 min.

[0034] According to the method of the second aspect, part of the wastewater after the catalytic oxidation reaction is returned to the photocatalytic reactor, and the rest is mixed with the alkali solution in the post-mixer;

[0035] Preferably, the mass ratio of iron in the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction to iron in the returned waste residue is 0.001-1:1, preferably 0.01-0.2:1.

[0036] According to the method of the second aspect, the weight ratio of the dosage of the oxidant to the COD of the sewage is 0.01-100:1, preferably 0.1-5:1; and / or

[0037] The molar ratio of ferrous ions to oxidant in the pre-mixer is 0.01-100:1, preferably 0.1-10:1.

[0038] The photocatalytic reaction device and sewage treatment method of the present invention may have but are not limited to the following beneficial effects:

[0039] The present invention converts iron ions Fe into ferrous ions by reflux of effluent and waste residue in a catalytic oxidation reactor and by photocatalytic reaction. 3+ Converted into ferrous ion Fe 2+ , which promotes the circulation of catalyst in the system, reduces the amount of catalyst added, and reduces the amount of hazardous waste and slag generated.

[0040] The invention has the advantages of small dosage of reagents, small amount of waste residue generated, good treatment effect and low treatment cost. It is suitable for treating difficult-to-degrade sewage, especially suitable for treating low-salt sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The schematic diagram of the structure of the photocatalytic reaction device of the present invention is shown.

[0042] Description of reference numerals:

[0043] 1. Pre-mixer; 2. Catalytic oxidation reactor; 3. Post-mixer; 4. Solid-liquid separator; 5. Photocatalytic reactor; G1, water inlet line; G2, catalyst line; G3, oxidant line; G4, alkali addition line; G5, drainage line; G6, slag discharge line; G7, acid addition line; S1, pre-mixer inlet; S2, pre-mixer outlet; S3, catalytic oxidation reactor inlet; S4, catalytic oxidation reactor outlet 1; S5, post-mixer inlet; S6, post-mixer outlet; S7, solid-liquid separator inlet; S8, solid-liquid separator drainage outlet; S9, solid-liquid separator slag discharge outlet; S10, photocatalytic reactor inlet 1; S11 photocatalytic reactor outlet; S12, catalytic oxidation reactor outlet 2; S13, photocatalytic reactor inlet 2; T1, acid addition line regulating valve; T2, alkali addition line regulating valve; Z1, catalytic oxidation reactor pH online probe; Z2, solid-liquid separator pH online probe. DETAILED DESCRIPTION

[0044] The present application is further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present application will become clearer and more specific.

[0045] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0046] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0047] In the present application, the reflux ratio of waste slag refers to the ratio of the amount of waste slag returned to the photocatalytic reactor to the amount of waste slag discharged through the slag discharge line.

[0048] The following combination Figure 1 To illustrate the photocatalytic reaction device and sewage treatment method of the present invention,

[0049] like Figure 1 As shown, the photocatalytic reaction device of the present invention comprises:

[0050] Pre-mixer 1;

[0051] Catalytic oxidation reactor 2;

[0052] Post mixer 3;

[0053] a solid-liquid separator 4; and

[0054] Photocatalytic reactor 5;

[0055] The pre-mixer inlet S1 is connected to the water inlet line G1, the catalyst line G2 and the oxidant line G3; the pre-mixer outlet S2 is connected to the catalytic oxidation reactor inlet S3;

[0056] The outlet of the catalytic oxidation reactor S4 is connected to the inlet of the post-mixer S5, and the inlet of the post-mixer S5 is connected to the alkali adding line G4;

[0057] The outlet S6 of the post-mixer is connected to the inlet S7 of the solid-liquid separator, the drain outlet S8 of the solid-liquid separator is connected to the drain line G5, and the slag discharge outlet S9 of the solid-liquid separator is connected to the slag discharge line G6;

[0058] The solid-liquid separator slag discharge port S9 is also connected to the photocatalytic reactor inlet S10, and the photocatalytic reactor inlet S10 is also connected to the acid addition line G7;

[0059] The photocatalytic reactor outlet S11 is communicated with the pre-mixer inlet S1.

[0060] In one embodiment, the catalytic oxidation reactor 2 is further provided with a catalytic oxidation reactor outlet 2 S12, and the photocatalytic reactor 5 is further provided with a photocatalytic reactor inlet 2 S13, and the photocatalytic reactor inlet 2 S13 is connected to the catalytic oxidation reactor outlet 2 S12.

[0061] In one embodiment, a catalytic oxidation reactor pH online probe Z1 is provided in the catalytic oxidation reactor 2 , and an acid addition line regulating valve T1 is provided on the acid addition line G7 for adjusting the acid addition amount to control the pH value in the catalytic oxidation reactor 2 .

[0062] In one embodiment, a solid-liquid separator pH online probe Z2 is provided in the solid-liquid separator 4 , and an alkali addition line regulating valve T2 is provided on the alkali addition line G4 for adjusting the amount of alkali addition to control the pH value in the solid-liquid separator 4 .

[0063] In one embodiment, the photocatalyst in the photocatalytic reactor 5 is TiO2; and / or

[0064] An ultraviolet lamp is arranged in the photocatalytic reactor 5; preferably, the wavelength of the ultraviolet lamp is 185nm and 254nm.

[0065] The present invention also provides a sewage treatment method, which uses the above-mentioned photocatalytic reaction device to treat sewage, comprising:

[0066] The sewage to be treated is mixed with the catalyst, the oxidant, and the acidic reflux liquid flowing out of the photocatalytic reactor 5 in the pre-mixer 1 and then enters the catalytic oxidation reactor 2 for catalytic oxidation reaction. The sewage after the catalytic oxidation reaction and the alkaline solution are mixed in the post-mixer 3 and then enter the solid-liquid separator 4 for solid-liquid separation.

[0067] The sewage after solid-liquid separation is discharged from the solid-liquid separator drain port S8, a part of the waste residue after solid-liquid separation is discharged from the solid-liquid separator residue discharge port S9, and the rest is mixed with the acid solution and refluxed to the photocatalytic reactor 5 for photocatalytic oxidation reaction, and the acidic reflux liquid after the photocatalytic oxidation reaction returns to the pre-mixer 1.

[0068] The waste slag reflux dissolves Fe(OH)3 in the waste slag to form Fe 3+ In the photocatalytic reactor 5, the combined action of ultraviolet light and photocatalyst promotes the Fe 3+ Converted to Fe 2+ The method of the present invention is to reflux the waste residue and dissolve it in acid, and use photocatalytic reaction to convert Fe 3+ Converted to Fe 2+ , reducing and utilizing Fe in waste slag 3+ , greatly reducing the amount of waste residue generated and the amount of catalyst added. In one embodiment, the reflux ratio of the waste residue is 0.2-20:1, preferably 0.5-10:1.

[0069] In one embodiment, a portion of the wastewater after the catalytic oxidation reaction is returned to the photocatalytic reactor 5, and the remaining portion is mixed with the alkali solution in the post-mixer 3;

[0070] Preferably, the mass ratio of iron in the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction to iron in the returned waste residue is 0.001-1:1, preferably 0.01-0.2:1.

[0071] Catalytic oxidation reactor 2 is rich in Fe 3+ The effluent is directly returned to the photocatalytic reactor 5, skipping the waste residue acid dissolution process, and in the photocatalytic reactor 5, the Fe 3+ Converted to Fe 2+ , the reduced Fe 2+ Enter the pre-mixer and re-enter the pre-mixer 1 to participate in the reaction, thereby reducing the amount of catalyst added.

[0072] In one embodiment, the catalyst is a reducing metal and / or a reducing metal salt, preferably ferrous sulfate; and / or

[0073] The oxidant is peroxide and / or persulfate, preferably hydrogen peroxide.

[0074] In one embodiment, the pH value in the catalytic oxidation reactor 2 is <6, preferably a pH value of 3-5; and / or

[0075] The pH value in the solid-liquid separator 4 is ≥6, preferably a pH value of 6-9.

[0076] In one embodiment, the residence time of the sewage in the catalytic oxidation reactor 2 is 5-1200 min, preferably 30-300 min;

[0077] The residence time of the sewage in the solid-liquid separator is 20-1200 min, preferably 30-600 min; and / or

[0078] The residence time of the material in the photocatalytic reactor is 2-600 min, preferably 20-240 min.

[0079] The present invention controls the total iron mass percentage concentration in the photocatalytic reactor to be 0.1-1% and the pH to be 1-2, thereby determining the reflux ratio of the waste residue and the effluent reflux amount of the catalytic oxidation reactor back to the photocatalytic reactor. The total iron includes iron in the solution and the iron mud waste residue.

[0080] In one embodiment, the weight ratio of the dosage of the oxidant to the COD of the sewage is 0.01-100:1, preferably 0.1-5:1; and / or

[0081] The molar ratio of ferrous ions to oxidant in the pre-mixer is 0.01-100:1, preferably 0.1-10:1.

[0082] The following examples treat phenol-containing wastewater. Table 1 shows the water quality of phenol-containing wastewater, and Table 2 shows the water quality of a certain petrochemical high-difficulty and difficult-to-degrade wastewater.

[0083] Table 1 Water quality of phenol-containing wastewater

[0084] index pH COD(mg / L) TOC(mg / L) Numeric 7.99 435 135

[0085] Table 2 Water quality of a petrochemical wastewater

[0086] index pH COD(mg / L) TOC(mg / L) Numeric 7.20 1650 560

[0087] In the following examples, the inner wall of the photocatalytic reactor is coated with a conventional TiO2 photocatalyst, and the TiO2 photocatalyst used in the following examples and comparative examples is a nano titanium dioxide ball purchased from Xuancheng Jingrui New Materials Co., Ltd. The ultraviolet lamp in the photocatalytic reactor simultaneously irradiates vacuum ultraviolet waves with a wavelength of 185nm and short-wavelength ultraviolet waves with a wavelength of 254nm.

[0088] Example 1

[0089] Taking phenol-containing wastewater as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+The molar ratio of the wastewater to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 minutes; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 minutes, the residence time of the material in the photocatalytic reactor is 30 minutes, the ultraviolet lamp in the photocatalytic reactor is turned on, the ultraviolet lamp power corresponding to each liter of wastewater is 6W, the reflux ratio of the waste residue is 3:1, the mass ratio of the iron in the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction to the iron in the reflux waste residue is 0.03:1, the mass percentage concentration of the total iron in the photocatalytic reactor is 0.31%, the pH is 1.1, and the Fe after the photocatalytic reaction 2+ 10% of the total iron content, Fe 2+ The concentration of divalent iron is 311 mg / L, the effluent COD of the solid-liquid separator is 80 mg / L, and the TOC is 27 mg / L.

[0090] Example 2

[0091] Taking phenol-containing wastewater as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+ The molar ratio of the wastewater to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 minutes; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 minutes, the residence time of the material in the photocatalytic reactor is 30 minutes, the ultraviolet lamp of the photocatalytic reactor is turned on, the ultraviolet power corresponding to each liter of wastewater is 6W, the reflux ratio of the waste residue is 6:1, the mass percentage concentration of total iron in the photocatalytic reactor is 0.33%, the pH is 1.7, the mass ratio of iron in the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction to the iron in the reflux waste residue is 0.05:1, and the Fe after the photocatalytic reaction is 0.1%. 2+ 6% of the total iron content, Fe 2+ The concentration of divalent iron is 198 mg / L, the effluent COD of the solid-liquid separator is 70 mg / L, and the TOC is 23 mg / L.

[0092] In the reaction system of the present invention, as the reaction continues, the system eventually reaches a steady-state equilibrium. In this state, the Fe 2+ The amount of iron in the waste slag discharged through the slag discharge line G6 is equal. Therefore, different waste slag reflux ratios will result in different total amounts of iron in the system. When the system reaches a steady-state equilibrium, the total amount of iron in the photocatalytic reactor of Example 2 is about twice that of Example 1. Therefore, the Fe 2+ The total amount is greater, thus achieving a better degradation effect.

[0093] Comparative Example 1

[0094] Taking phenol-containing wastewater as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+ The molar ratio of the waste residue to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 minutes; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 minutes, the residence time of the material in the photocatalytic reactor is 30 minutes, the ultraviolet lamp in the photocatalytic reactor is not turned on, the reflux ratio of the waste residue is 6:1, the mass ratio of the iron in the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction to the iron in the waste residue is 0.05:1, the mass percentage concentration of the total iron in the photocatalytic reactor is 0.33%, the pH is 1.7, and the Fe after the photocatalytic unit 2+ Accounting for 0.6% of the total iron content, Fe 2+ The concentration of divalent iron is 19.8 mg / L, the effluent COD of the solid-liquid separator is 100 mg / L, and the TOC is 34 mg / L.

[0095] Without turning on the UV lamp, the photocatalytic reactor converts into Fe 2+ Fe 3+ Very little, which has an adverse effect on the further catalytic oxidation reaction.

[0096] Comparative Example 2

[0097] Taking phenol-containing wastewater as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+ The molar ratio of the wastewater to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 min; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 min, the residence time of the material in the photocatalytic reactor is 30 min, the ultraviolet lamp in the photocatalytic reactor is turned on, the ultraviolet lamp power corresponding to each liter of wastewater is 6 W, the waste residue is not refluxed, and the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction is consistent with that in Comparative Example 1, the mass percentage concentration of total iron in the photocatalytic reactor is 0.013%, the pH is 4, and the Fe after the photocatalytic reaction 2+ Fe accounts for 28% of the total iron content. 2+ The concentration of divalent iron is 37.5 mg / L, the effluent COD of the solid-liquid separator is 90 mg / L, and the TOC is 31 mg / L.

[0098] Without reflux of waste residue, although under the same photocatalytic reaction conditions, Fe 2+ However, since the waste residue is not refluxed, the mass percentage concentration of total iron in the photocatalytic reactor is low, which makes Fe 2+ The concentration of divalent iron is still at a low level, which is not conducive to the catalytic degradation reaction.

[0099] Comparative Example 3

[0100] Taking phenol-containing wastewater as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+ The molar ratio of the wastewater to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 minutes; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 minutes, the residence time of the material in the photocatalytic reactor is 30 minutes, the photocatalytic reactor turns on the ultraviolet lamp, the ultraviolet lamp power corresponding to each liter of wastewater is 6W, the reflux ratio of the waste residue is 6:1, the effluent of the catalytic oxidation reactor does not flow back to the photocatalytic reactor, the mass percentage concentration of total iron in the photocatalytic reactor is 0.42%, the pH is 1.7, and the Fe after the photocatalytic reaction 2+ 7% of the total iron content, Fe 2+ The concentration of divalent iron is 294 mg / L, the effluent COD of the solid-liquid separator is 85 mg / L, and the TOC is 29 mg / L.

[0101] Since the recirculated effluent can degrade a portion of COD by means of photocatalysis, the degradation effect of wastewater is poor when the effluent from the catalytic oxidation reactor is not recirculated.

[0102] Comparative Example 4

[0103] The phenol-containing wastewater was treated by conventional Fenton treatment, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+ The molar ratio of hydrogen peroxide to water was 0.1:1, and the residence time in the reactor was 60 min. The same wastewater as in Example 1 was treated, and the amount of waste residue produced was similar. The COD of the effluent from the solid-liquid separator was 100 mg / L, and the TOC was 35 mg / L.

[0104] Comparative Example 5

[0105] The phenol-containing wastewater was treated by conventional Fenton treatment, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+ The molar ratio of hydrogen peroxide to water was 0.4:1, and the residence time in the reactor was 60 min. When treating the same wastewater as in Example 1, the amount of waste residue produced was nearly 4 times that of the waste residue in Example 1. The COD of the effluent from the solid-liquid separator was 80 mg / L, and the TOC was 27 mg / L.

[0106] Comparative Example 6

[0107] Taking phenol-containing wastewater as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+The molar ratio of the wastewater to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 minutes; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 minutes, the residence time of the material in the photocatalytic reactor is 30 minutes, there is no titanium dioxide catalyst in the photocatalytic reactor, the ultraviolet lamp is turned on, the ultraviolet lamp power corresponding to each liter of wastewater is 6W, the reflux ratio of the waste residue is 6:1, the mass percentage concentration of total iron in the photocatalytic reactor is 0.33%, the pH is 1.7, the mass ratio of iron in the effluent refluxed to the photocatalytic reactor after the catalytic oxidation reaction to the iron in the refluxed waste residue is 0.05:1, and the Fe after the photocatalytic reaction is 0.1:1. 2+ 5% of the total iron content, Fe 2+ The concentration of divalent iron is 165 mg / L, the effluent COD of the solid-liquid separator is 88 mg / L, and the TOC is 30 mg / L.

[0108] Without adding TiO2 catalyst, UV light can promote the 3+ Converted to Fe 2+ , but the effect is worse than that in the presence of TiO2 catalyst. 2+ The synergistic effect can better reduce COD, so without adding TiO2 catalyst, the value of effluent COD increases significantly.

[0109] Comparative Example 7

[0110] Taking phenol-containing wastewater as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 800 mg / L (based on the amount of wastewater), and Fe 2+ The molar ratio of the wastewater to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 minutes; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 minutes, the residence time of the material in the photocatalytic reactor is 30 minutes, there is no titanium dioxide catalyst in the photocatalytic reactor, the ultraviolet lamp is turned on, the ultraviolet lamp power corresponding to each liter of wastewater is 6W, the reflux ratio of the waste residue is 6:1, no acid is added to the reflux of the waste residue, acid is added before Fenton oxidation, the effluent of the catalytic oxidation reactor is not refluxed, the mass percentage concentration of total iron in the photocatalytic reactor is 0.33%, the pH is 4.4, the mass ratio of iron in the effluent returning to the photocatalytic reactor after the catalytic oxidation reaction to iron in the refluxed waste residue is 0.05:1, and Fe after the photocatalytic reaction is 2.34%. 2+ 3% of the total iron content, Fe 2+ The concentration of divalent iron is 99 mg / L, the effluent COD of the solid-liquid separator is 83 mg / L, and the TOC is 28 mg / L.

[0111] Under the conditions of no acid addition during waste slag reflux and acid addition before Fenton oxidation, the trivalent iron in the photocatalytic reactor mainly exists in the form of waste slag, a small amount of trivalent iron is refluxed by the catalytic oxidation reaction, and a small amount is converted into divalent iron through the photocatalytic reaction, which affects the degradation effect of the wastewater.

[0112] Comparative Example 8

[0113] Taking a petrochemical wastewater (properties as shown in Table 2) as the treatment object, the pH value of the catalytic oxidation reactor was controlled to be 4, the amount of hydrogen peroxide added was 2000 mg / L (based on the amount of wastewater), Fe 2+ The molar ratio of the wastewater to hydrogen peroxide is 0.1:1, and the residence time in the reactor is 60 minutes; the pH value of the solid-liquid separator is 8, the residence time in the solid-liquid separator is 60 minutes, the residence time of the material in the photocatalytic reactor is 30 minutes, the ultraviolet lamp of the photocatalytic reactor is turned on, the ultraviolet power corresponding to each liter of wastewater is 6W, the reflux ratio of the waste residue is 6:1, the mass percentage concentration of total iron in the photocatalytic reactor is 0.34%, the pH is 2.0, the mass ratio of iron in the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction to the iron in the reflux waste residue is 0.13:1, and the Fe after the photocatalytic reaction is 0.14:1. 2+ 2% of the total iron content, Fe 2+ The concentration of divalent iron is 68 mg / L, the effluent COD of the solid-liquid separator is 270 mg / L, TOC is 100 mg / L, the sludge production accounts for about 5% of the input treatment volume, and the treatment cost is about 10-12 yuan / cubic meter (excluding sludge treatment cost).

[0114] The present application has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, various replacements and improvements may be made to the present application, all of which fall within the scope of protection of the present application.

Claims

1. A photocatalytic reaction device, characterized in that: The device comprises: Pre-mixer; Catalytic oxidation reactor; Post mixer; solid-liquid separator; and Photocatalytic reactor; The inlet of the pre-mixer is connected with a water inlet line, a catalyst line and an oxidant line; the outlet of the pre-mixer is connected with the inlet of the catalytic oxidation reactor; The first outlet of the catalytic oxidation reactor is communicated with the inlet of the post-mixer, and the inlet of the post-mixer is connected to an alkali adding line; The outlet of the post-mixer is connected to the inlet of the solid-liquid separator, the drain outlet of the solid-liquid separator is connected to the drain line, and the slag discharge outlet of the solid-liquid separator is connected to the slag discharge line; The slag discharge port of the solid-liquid separator is also connected to the first inlet of the photocatalytic reactor, and the first inlet of the photocatalytic reactor is also connected to the acid addition line; The outlet of the photocatalytic reactor is communicated with the inlet of the pre-mixer.

2. The device according to claim 1, characterized in that The catalytic oxidation reactor is further provided with a second outlet, and the photocatalytic reactor is further provided with a second inlet, and the second inlet of the photocatalytic reactor is connected to the second outlet of the catalytic oxidation reactor.

3. The device according to claim 1, characterized in that A pH probe is provided in the catalytic oxidation reactor, and a regulating valve is provided on the acid addition line, wherein the regulating valve is used to adjust the amount of acid addition to control the pH value in the catalytic oxidation reactor.

4. The device according to claim 1, characterized in that A pH probe is provided in the solid-liquid separator, and a regulating valve is provided on the alkali adding line, wherein the regulating valve is used to adjust the amount of alkali added to control the pH value in the solid-liquid separator.

5. The device according to claim 1, characterized in that The photocatalyst in the photocatalytic reactor is TiO2; and / or An ultraviolet lamp is arranged in the photocatalytic reactor; preferably, the wavelength of the ultraviolet lamp is 185nm and 254nm.

6. A method for treating sewage, characterized in that: The method uses the photocatalytic reaction device according to any one of claims 1 to 5 to treat sewage, comprising: The sewage to be treated is mixed with the catalyst, oxidant, and acidic reflux liquid from the photocatalytic reactor in the pre-mixer and then enters the catalytic oxidation reactor for catalytic oxidation reaction. The sewage after the catalytic oxidation reaction is mixed with the alkaline solution in the post-mixer and then enters the solid-liquid separator for solid-liquid separation. The sewage after solid-liquid separation is discharged from the drain outlet, part of the waste residue after solid-liquid separation is discharged from the residue outlet, and the rest is mixed with the acid liquid and returned to the photocatalytic reactor for photocatalytic oxidation reaction. The acidic reflux liquid after the photocatalytic oxidation reaction returns to the pre-mixer.

7. The method according to claim 6, characterized in that The reflux ratio of the waste residue is 0.2-20:1, preferably 0.5-10:

1.

8. The method according to claim 6, characterized in that The catalyst is a reducing metal and / or a reducing metal salt, preferably ferrous sulfate; and / or The oxidant is peroxide and / or persulfate, preferably hydrogen peroxide.

9. The method according to claim 6, characterized in that The pH value in the catalytic oxidation reactor is <6, preferably pH 3-5; and / or The pH value in the solid-liquid separator is ≥6, preferably a pH value of 6-9.

10. The method according to claim 6, characterized in that The residence time of the sewage in the catalytic oxidation reactor is 5-1200 min, preferably 30-300 min; The residence time of the sewage in the solid-liquid separator is 20-1200 min, preferably 30-600 min; and / or The residence time of the material in the photocatalytic reactor is 2-600 min, preferably 20-240 min.

11. The method according to claim 6, characterized in that Part of the wastewater after the catalytic oxidation reaction flows back to the photocatalytic reactor, and the rest is mixed with the alkali solution in the post-mixer; Preferably, the mass ratio of iron in the effluent returned to the photocatalytic reactor after the catalytic oxidation reaction to iron in the returned waste residue is 0.001-1:1, preferably 0.01-0.2:

1.

12. The method according to claim 6, characterized in that The weight ratio of the dosage of the oxidant to the COD of the sewage is 0.01-100:1, preferably 0.1-5:1; and / or The molar ratio of ferrous ions to oxidant in the pre-mixer is 0.01-100:1, preferably 0.1-10:1.

Images