A method for treating wastewater by catalytic oxidation system

Abstract

A method for treating wastewater using a catalytic oxidation system with enhanced synergy includes the following steps: adjusting the reaction system to acidic or neutral with acid, then sequentially adding a reducing catalyst, a synergist 1, an oxidant, and a synergist 2 to carry out a catalytic oxidation reaction; the synergist 1 is a complex or a small molecule organic acid, and the synergist 2 is a non-metallic reducing inorganic substance. This method overcomes the shortcomings of traditional catalytic oxidation, such as low efficiency, high dosage, and reliance on a strongly acidic reaction environment, effectively improving catalytic oxidation efficiency.

Description

Technical Field

[0001] The present invention relates to a wastewater treatment method, in particular to a wastewater treatment method using a catalytic oxidation system. Background Art

[0002] With the development of society and the progress of related industries, my country's wastewater output is increasing, and the water pollution situation is serious. Especially for high-concentration, refractory organic polluted wastewater, its biodegradability is poor, and it is difficult to treat. The general biological treatment effect is poor.

[0003] Advanced oxidation technology has been a research hotspot in recent years. It has a good treatment effect on high-concentration, difficult-to-degrade, and especially poorly biodegradable organic wastewater, and can effectively improve its biodegradability. The Fenton oxidation method is the most widely used due to its low treatment cost, the lack of large-scale treatment equipment, and simple operation. However, traditional Fenton also has certain problems. First, it requires a strictly acidic reaction environment, generally pH = 3. In addition, it is limited by the conversion rate of the valence state of divalent iron and trivalent iron, and its catalytic reaction rate is relatively slow. A large amount of iron salt is required to maintain the reaction effect, which in turn leads to the problem of secondary pollution caused by iron sludge that is difficult to treat.

[0004] At present, a large number of researchers have made improvements to the Fenton reaction process to enhance its treatment effect and promote its wider application.

[0005] Patent CN110015744A utilizes free chlorine to enhance the Fenton / Fenton-like reaction system to remove pollutants from water, addressing the problems of existing Fenton treatment systems, such as high H2O2 consumption, high iron dosage, and poor pollutant removal. The pH of the water to be treated is adjusted to between 2.0 and 4.0. Ferrous salts are then added to the water, stirred, and hydrogen peroxide solution is added. A hypochlorite solution or chlorine gas is then added to bring the effective chlorine concentration in the system to 1 to 15 mg / L, enhancing the reaction and removing pollutants from the water. However, this invention suffers from the fact that the addition of chlorine reacts with some organic matter in the wastewater to form difficult-to-degrade chlorinated hydrocarbons, which can affect the treatment process.

[0006] Patent CN105195150A discloses a method and application for preparing a highly efficient Fe3O4 / FeAl2O4 composite film Fenton-like catalyst, addressing the challenges of existing Fenton-like catalysts, such as difficulty in catalyst separation and recycling, and poor mechanical properties. The method comprises: 1. polishing carbon steel; 2. connecting a bright carbon steel sheet to the positive pole of a power supply, serving as an anode; and 3. connecting a stainless steel electrolytic cell to the negative pole of a power supply, serving as a cathode; and 4. employing a plasma electrolysis reaction to obtain a highly efficient Fe3O4 / FeAl2O4 composite film Fenton-like catalyst. The Fe3O4 / FeAl2O4 composite film Fenton-like catalyst prepared in this invention achieves 100% phenol degradation efficiency within 60 minutes. This method can be used under near-neutral conditions, effectively addressing the limitations of conventional Fenton-like catalysts, which are limited by the complexity of preparing the composite film Fenton-like catalyst and the potential for membrane contamination that affects the treatment effect.

[0007] In short, the existing Fenton oxidation technology still has problems of slow reaction rate and low treatment efficiency for some difficult-to-treat organic wastewater. Summary of the Invention

[0008] The present invention aims to provide a method for treating wastewater by enhancing the efficiency of catalytic oxidation system, which can further improve the catalytic oxidation efficiency and reduce the dosage.

[0009] A method for treating wastewater by synergistically enhancing a catalytic oxidation system comprises the following steps: adjusting a reaction system to acidity or neutrality with an acid, and then sequentially adding a reducing catalyst, a synergist 1, an oxidant, and a synergist 2 to carry out a catalytic oxidation reaction.

[0010] In the present invention, the synergist 1 is a complex or a small molecule organic acid substance, which can be selected from one or more of the complexing agents EDTA (ethylenediaminetetraacetic acid), EDDS (ethylenediamine disuccinic acid), citric acid, oxalic acid, salicylic acid, tartaric acid, benzoquinone, etc., preferably EDTA.

[0011] In the present invention, the synergist 2 is a non-metallic reducing inorganic substance selected from hydroxylamine hydrochloride, hydroxylamine sulfate, sulfite, hydrazine, etc., preferably hydroxylamine hydrochloride.

[0012] In the present invention, the pH of the catalytic oxidation reaction is 1-8, preferably 2-5.

[0013] In the present invention, the catalyst is selected from one or more of reducing metals, metal salts, and metal oxides, such as Fe 2 + 、Fe 3+ 、Co 2+ 、Ni 2+ 、Mn 2+ 、Cu 2+etc., preferably ferrous salts such as ferrous chloride, ferrous sulfate, etc.

[0014] In the present invention, the oxidant is selected from one or more of H2O2, ozone, and hypochlorite, preferably H2O2.

[0015] In the present invention, the mass concentration ratio of the catalyst to the oxidant is 0.1 to 20:1, preferably 0.5 to 10:1.

[0016] In the present invention, the ratio of the mass concentration of the oxidant to the COD is 0.05 to 10:1, preferably 0.1 to 2:1.

[0017] In the present invention, the ratio of the dosage of the synergist 1 to the mass concentration of the added catalyst is 0.02 to 11:1, preferably 0.1 to 5:1, and more preferably 0.3 to 2:1.

[0018] In the present invention, the ratio of the dosage of the synergist 2 to the mass concentration of the added catalyst is 0.01 to 5:1, preferably 0.05 to 1:1, and more preferably 0.1 to 0.5:1.

[0019] In the present invention, after adjusting the pH, the catalyst, synergist 1, and oxidant are added in sequence and reacted for 0.1 to 8 minutes, preferably 0.5 to 3 minutes. Then, synergist 2 is added and reacted for 5 to 120 minutes, preferably 10 to 90 minutes. After the reaction, the pH is adjusted to neutral with a base, and flocculation precipitation is performed. The base is preferably sodium hydroxide, and the pH is preferably 6 to 9. The reaction time for flocculation precipitation (clarification) is 5 to 600 minutes, preferably 30 to 320 minutes.

[0020] In the present invention, the wastewater to be treated may be wastewater that is difficult to biodegrade, especially wastewater generated by the HPPO process.

[0021] The present invention effectively overcomes the shortcomings of traditional catalytic oxidation, such as low efficiency, high dosage, and reliance on a strongly acidic reaction environment, effectively improving catalytic oxidation efficiency. It can treat wastewater that is difficult to treat using conventional catalytic oxidation methods, and has the advantages of good treatment effect and high treatment efficiency. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below with reference to specific implementation methods.

[0023] Experiment 1:

[0024] Table 1 shows the HPPO wastewater produced by a chemical production unit of a refining and chemical company. The water quality indicators are as follows:

[0025] Table 1 HPPO wastewater produced by a refinery chemical plant

[0026]

[0027] Experimental setup and processing results:

[0028] Experimental group Hydroxylamine / Hydrazine EDTA / citric acid pH COD BOD B / C unit mg / L mg / L mg / L mg / L Example 1-1 750 2000 3 8300 2660 0.32 Example 1-2 1000 2500 3 8200 2870 0.35 Examples 1-3 1000 2500 3 8350 1420 0.17 Examples 1-4 1000 2500 3 8943 1342 0.15 Comparative Example 1-1 0 0 3 9370 1040 0.15 Comparative Example 1-2 0 2000 3 8900 1500 0.17 Comparative Examples 1-3 1000 0 3 9150 1650 0.18 Comparative Examples 1-4 1000 2500 3 8450 1267 0.17 Comparative Examples 1-5 1000 2500 3 8400 1347 0.15 Comparative Examples 1-6 1000 2500 3 8420 1347 0.16 Comparative Examples 1-7 1000 2500 3 8310 1496 0.18 Comparative Examples 1-8 0 2500 3 8950 1432 0.16

[0029] Example 1-1

[0030] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 3000mg / L of FeSO4·7H2O, stir at 300rpm, add 2000mg / L of EDTA, stir for 2 minutes, then add 2000mg / L of hydrogen peroxide. After reacting for 2 minutes, add 750mg / L of hydroxylamine hydrochloride. After reacting for 60 minutes, adjust the pH to 7 with 5% sodium hydroxide. After standing for 1 hour, collect the supernatant and measure the corresponding indicators. The measured COD is 8300mg / L, BOD is 2660mg / L, and the B / C ratio reaches 0.32.

[0031] Example 1-2

[0032] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 3000mg / L of FeSO4·7H2O, stir at 300rpm, add 2500mg / L of EDTA, stir for 2 minutes, then add 2000mg / L of hydrogen peroxide. After reacting for 2 minutes, add 1000mg / L of hydroxylamine hydrochloride. After reacting for 60 minutes, adjust the pH to 7 with 5% sodium hydroxide. After standing for 1 hour, collect the supernatant and measure the corresponding indicators. The measured COD is 8200mg / L, BOD is 2870mg / L, and the B / C ratio reaches 0.35.

[0033] Examples 1-3

[0034] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 3000mg / L of FeSO4·7H2O, stir at 300rpm, add 2500mg / L of citric acid, stir for 2 minutes, then add 2000mg / L of hydrogen peroxide. After reacting for 2 minutes, add 1000mg / L of hydroxylamine hydrochloride. After reacting for 60 minutes, adjust the pH to 7 with 5% sodium hydroxide. After standing for 1 hour, collect the supernatant and measure the corresponding indicators. The measured COD is 8350mg / L, BOD is 1420mg / L, and the B / C ratio reaches 0.17.

[0035] Examples 1-4

[0036] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 3000mg / L of FeSO4·7H2O, stir at 300rpm, add 2500mg / L of EDTA, stir for 2 minutes, then add 2000mg / L of hydrogen peroxide. After reacting for 2 minutes, add 1000mg / L of hydrazine, react for 60 minutes, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1 hour, collect the supernatant and measure the corresponding indicators. The measured COD is 8943mg / L, the BOD is 1342mg / L, and the B / C ratio reaches 0.17.

[0037] Comparative Example 1-1

[0038] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 3000mg / L of FeSO4·7H2O, stir at 300rpm, stir for 2 minutes, then add 2000mg / L of hydrogen peroxide. After reacting for 60 minutes, adjust the pH to 7 with 5% sodium hydroxide. After standing for 1 hour, collect the supernatant and measure the corresponding indicators. The measured COD is 9370mg / L, the BOD is 1040mg / L, and the B / C ratio reaches 0.11.

[0039] Comparative Example 1-2

[0040] The main process is the same as that of Example 1-1, but compared with Example 1-1, Comparative Example 1-2 does not add EDTA. The other reaction processes are the same. The COD is 9150 mg / L, the BOD is 1650 mg / L, and the B / C reaches 0.18.

[0041] Comparative Examples 1-3

[0042] The main process is the same as that of Example 1-1, but compared with Example 1-1, hydroxylamine hydrochloride is not added in Comparative Example 1-3. The other reaction processes are the same. The COD is 8900 mg / L, the BOD is 1500 mg / L, and the B / C reaches 0.17.

[0043] Comparative Examples 1-4

[0044] The main process is the same as that of Example 1-2, but compared with Example 1-1, Comparative Example 1-4 is added with EDTA and hydroxylamine hydrochloride at the same time after the addition of the catalyst FeSO4·7H2O. The other reaction processes are the same. The COD is 8450 mg / L, the BOD is 1267 mg / L, and the B / C reaches 0.15.

[0045] Comparative Examples 1-5

[0046] The main process is the same as that of Example 1-2, except that the order of adding EDTA and hydroxylamine hydrochloride is reversed, i.e., hydroxylamine hydrochloride is added first, then EDTA. The other reaction processes are the same. The COD is 8400 mg / L, the BOD is 1260 mg / L, and the B / C ratio reaches 0.15.

[0047] Comparative Examples 1-6

[0048] The main process is the same as that of Example 1-2. Compared with Example 1-2, Comparative Example 1-6 is characterized by adding the oxidant and hydroxylamine hydrochloride at the same time, and the other reaction processes are the same. The COD is 8420 mg / L, the BOD is 1347 mg / L, and the B / C ratio reaches 0.16.

[0049] Comparative Examples 1-7

[0050] The main process is the same as that of Example 1-2. Compared with Example 1-2, Comparative Example 1-7 is added with hydroxylamine hydrochloride 10 minutes after the addition of the oxidant. The other reaction processes are the same. The COD is 8310 mg / L, the BOD is 1496 mg / L, and the B / C reaches 0.18.

[0051] Comparative Examples 1-8

[0052] The main process is the same as that of Example 1-2, but compared with Example 1-2, no hydroxylamine hydrochloride is added in Comparative Example 1-8. The other reaction processes are the same. The COD is 8950 mg / L, the BOD is 1430 mg / L, and the B / C reaches 0.16.

[0053] Experiment 2:

[0054] The wastewater was taken from the secondary biochemical effluent of a certain refinery's sewage treatment plant. Its pH was 8.08 and COD was 75.6 mg / L. To meet the discharge standards, further deep treatment was required. The main purpose of catalytic oxidation as a deep treatment unit was to reduce the COD of the wastewater.

[0055] Experimental setup and processing results:

[0056]

[0057]

[0058] Example 2-1

[0059] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 50mg / L of FeSO4·7H2O, stir at 300rpm, add 40mg / L of EDTA, stir for 2min, then add 75mg / L of hydrogen peroxide, react for 2 minutes, add 20mg / L of hydroxylamine hydrochloride, react for 60min, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1h, take the supernatant and measure the corresponding indicators, and the measured COD is 38.5mg / L.

[0060] Example 2-2

[0061] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 50mg / L of FeSO4·7H2O, stir at 300rpm, add 40mg / L of EDTA, stir for 2min, then add 75mg / L of hydrogen peroxide, react for 2 minutes, add 20mg / L of hydroxylamine hydrochloride, react for 90min, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1h, take the supernatant and measure the corresponding indicators, and the measured COD is 37.0mg / L.

[0062] Example 2-3

[0063] Take 500mL of raw water, adjust the pH to 6.5 with 30% sulfuric acid, add 50mg / L of FeSO4·7H2O, stir at 300rpm, add 40mg / L of EDTA, stir for 2min, then add 75mg / L of hydrogen peroxide, react for 2 minutes, add 20mg / L of hydroxylamine hydrochloride, react for 60min, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1h, take the supernatant and measure the corresponding indicators, the measured COD is 44.5mg / L.

[0064] Examples 2-4

[0065] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 50mg / L of FeSO4·7H2O, stir at 300rpm, add 30mg / L of EDTA, stir for 2min, then add 75mg / L of hydrogen peroxide, react for 2 minutes, add 50mg / L of hydroxylamine hydrochloride, react for 60min, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1h, take the supernatant and measure the corresponding indicators, and the measured COD is 49.0mg / L.

[0066] Examples 2-5

[0067] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 50mg / L of FeSO4·7H2O, stir at 300rpm, add 40mg / L of citric acid, stir for 2min, then add 75mg / L of hydrogen peroxide, react for 2 minutes, add 20mg / L of hydroxylamine sulfate, react for 60min, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1h, take the supernatant and measure the corresponding indicators, the measured COD is 42.0mg / L.

[0068] Comparative Example 2-1

[0069] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 50mg / L of FeSO4·7H2O, stir at 300rpm, stir for 2min, then add 75mg / L of hydrogen peroxide, react for 60min, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1h, take the supernatant and measure the corresponding indicators, the measured COD is 65.4mg / L.

[0070] Comparative Example 2-2

[0071] Take 500mL of raw water, adjust the pH to 3 with 30% sulfuric acid, add 300mg / L of FeSO4·7H2O, stir at 300rpm, stir for 2min, then add 150mg / L of hydrogen peroxide, react for 60min, adjust the pH to 7 with 5% sodium hydroxide, let it stand for 1h, take the supernatant and measure the corresponding indicators, the measured COD is 64.0mg / L.

[0072] Comparative Examples 2-3

[0073] Compared with Example 2-1, the difference is that the addition order of EDTA and hydroxylamine hydrochloride is replaced with that of Example 2-1. Other reaction conditions are the same. The COD of the effluent is measured to be 65 mg / L.

[0074] Comparative Examples 2-4

[0075] Compared with Example 2-5, the difference is that hydroxylamine hydrochloride is not added, and other reaction conditions are the same. The COD of the effluent is measured to be 64.5 mg / L.

[0076] It can be seen from the examples and comparative examples that the method of the present invention can significantly promote the catalytic oxidation treatment effect through the coordinated use of two synergists, especially the coordinated use of hydroxylamine hydrochloride and EDTA, and the effect is significantly better than conventional catalytic oxidation, effectively shortening the reaction time, reducing the pH requirement of the reaction system, and saving the amount of drug added during the reaction; in addition, the order and time of adding the synergists also have a significant impact on the reaction effect.

Claims

1. A method for treating wastewater by synergistically enhancing a catalytic oxidation system, comprising the following steps: adjusting the reaction system to acidity with an acid, sequentially adding a reducing catalyst, a synergist 1, and an oxidant, reacting for 0.1 to 8 minutes, and then adding a synergist 2 to carry out a catalytic oxidation reaction; the synergist 1 is selected from one or more of ethylenediaminetetraacetic acid, ethylenediamine disuccinic acid, citric acid, salicylic acid, and tartaric acid, and the synergist 2 is selected from one or more of hydroxylamine hydrochloride, hydroxylamine sulfate, and hydrazine.

2. The method according to claim 1, wherein The pH of the catalytic oxidation reaction is 1 to 6.

5.

3. The method according to claim 1, wherein The pH of the catalytic oxidation reaction is 2-5.

4. The method according to claim 1, wherein The catalyst is selected from Fe 2+ 、Fe 3+ 、Co 2+ 、Ni 2+ 、Mn 2+ 、Cu 2+ One or more of the .

5. The method according to claim 1, wherein The oxidant is selected from one or more of H2O2, ozone, and hypochlorite.

6. The method according to claim 1, wherein The mass concentration ratio of the catalyst to the oxidant is 0.1 to 20:

1.

7. The method according to claim 1, wherein The mass concentration ratio of the catalyst to the oxidant is 0.5 to 10:

1.

8. The method according to claim 1, wherein The ratio of oxidant to COD mass concentration is 0.05 to 10:

1.

9. The method according to claim 1, wherein The ratio of oxidant to COD mass concentration is 0.1 to 2:

1.

10. The method according to claim 1, wherein The ratio of the dosage of synergist 1 to the mass concentration of the added catalyst is 0.1 to 5:

1.

11. The method according to claim 1, wherein The ratio of the dosage of synergist 1 to the mass concentration of the added catalyst is 0.3 to 2:

1.

12. The method according to claim 1, wherein The ratio of the dosage of synergist 2 to the mass concentration of the added catalyst is 0.05 to 1:

1.

13. The method according to claim 1, wherein The ratio of the dosage of synergist 2 to the mass concentration of the added catalyst is 0.1 to 0.5:

1.

14. The method according to claim 1, wherein After adjusting the pH value, the catalyst, synergist 1, and oxidant are added in sequence, and reacted for 0.5 to 3 minutes. Then, synergist 2 is added and reacted for 5 to 120 minutes.

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