A method of purifying water by precipitating pollutants

Abstract

The present application belongs to the technical field of water pollution control, and particularly relates to a water purification method for pollutant gathering and sedimentation, which comprises the following steps: adding Fe x S y and hydrogen peroxide into wastewater to perform catalytic oxidation reaction, so that the hydrophobicity of organic pollutant molecules in water is increased and the organic pollutant molecules are gathered to form solid sludge; then, through standing and sedimentation, the sludge and water are separated to obtain clean water. The water purification method provided by the present application changes the organic pollutants from degradation and mineralization to produce gas to weak oxidation, gathering and sedimentation to produce sludge, effectively reduces the amount of oxidizing agent under the condition of ensuring that the effluent COD meets the standard and is stable, thereby significantly reducing the energy consumption and cost of the oxidation water treatment process, and has a wide practical application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water pollution control, and particularly relates to a water purification method for pollutant aggregation and sedimentation. BACKGROUND

[0002] For a long time, advanced oxidation (AOP) methods represented by Fenton oxidation technology have been widely concerned in the field of physicochemical water treatment. They produce highly active oxidizing species intermediates such as hydroxyl radicals by activating oxidizing agents (such as H2O2) through catalysts (such as Fe 2+ ), thereby degrading and mineralizing organic pollutants. Due to the potential for treating highly toxic and refractory organic pollutants, they are widely used in detoxification pretreatment and deep purification treatment of industrial wastewater.

[0003] However, the Fenton-representative advanced oxidation method always has the problem of high energy consumption and high cost caused by the large addition of oxidizing agents, and the cost of oxidizing agents accounts for more than 60% of the cost of the oxidation water treatment process. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a water purification method for pollutant aggregation and sedimentation, which has the advantages of high removal efficiency of organic pollutants, low consumption of oxidizing agents, and stable effluent.

[0005] The present application provides a water purification method for pollutant aggregation and sedimentation, comprising the following steps:

[0006] Catalytic oxidation reaction is carried out by adding a catalyst and hydrogen peroxide to wastewater, so that the hydrophobicity of pollutant molecules increases and aggregates to form solid sludge; then standing and sedimentation are carried out, and the water is separated from the sludge to obtain clear water;

[0007] The catalyst is an iron-sulfur compound, and the chemical general formula is Fe x S y .

[0008] Preferably, the catalyst is Fe 0.8 S 0.2 or Fe 0.6 S 0.4 .

[0009] Preferably, the addition amount of the catalyst in the wastewater is 0.1-5 g / L.

[0010] Preferably, the particle size of the catalyst is 50 nm-10 μm.

[0011] Preferably, the addition concentration of the hydrogen peroxide in the wastewater is 3-5 times the molar concentration of the organic pollutants in the wastewater.

[0012] Preferably, the pH value of the catalytic oxidation reaction is 3-5.

[0013] Preferably, if the pH value of the wastewater does not meet the pH value requirement of the catalytic oxidation reaction, sulfuric acid is added to the wastewater for pH adjustment.

[0014] Preferably, the temperature of the catalytic oxidation reaction is 10-40℃.

[0015] Preferably, the organic pollutants include one or more of phenol, aniline, chlorophenol, bisphenol A, sulfonamide, chloroaniline and thiophene.

[0016] Preferably, the COD of the wastewater is 2000-10000mg / L.

[0017] Compared with the prior art, the present application provides a water purification method for pollutant aggregation and sludge production, which comprises the following steps: adding Fe x S y The catalytic oxidation reaction is carried out by adding a catalyst and hydrogen peroxide to the wastewater, so that the organic pollutant molecules in the water are weakly oxidized under the conditions of the catalyst and the oxidant, the proportion of hydrophilic functional groups such as hydroxyl, amino and mercapto is reduced, and the hydrophobicity of the molecules is increased, so that the organic pollutant molecules are aggregated and precipitated to form solid sludge. Then, the sludge is allowed to stand and precipitate, and the sludge and water are separated to obtain clean water. In order to improve the water treatment effect while effectively reducing the amount of oxidant used, the present application innovates the reaction path of the advanced oxidation technology, changes the gas production by degradation and mineralization of the organic pollutants to sludge production by aggregation and precipitation, and then performs simple separation and removal. By this method, various chemical bonds (such as C-C bonds) in the organic pollutant molecules do not need to be destroyed, and only the organic molecules are weakly oxidized, so the consumption of oxidant can be significantly reduced. Compared with the traditional degradation and mineralization method, the sludge production by aggregation and precipitation can reduce the use of oxidant by 1 to 3 orders of magnitude. Taking phenol as an example, if the degradation and mineralization reaction is carried out, 1 mole of phenol needs to release 28 moles of electrons, and consume about 14 moles or more of H2O2 (reaction: 1PhOH→6CO2+3H2O (small molecule product)+28e-); while in the sludge production by aggregation and precipitation reaction, 1 mole of phenol releases 2-6 moles of electrons, changes the hydroxyl group to a carbonyl group or an ether bond, and consumes about 1-3 moles of H2O2. Through this weak oxidation reaction and change in hydrophilic and hydrophobic properties, the organic pollutants in the water are aggregated and precipitated to form sludge, and finally the clean water is discharged through solid-liquid separation. In addition, the main components of the sludge generated by the method of the present application are Fe x S y The aggregates of the catalyst and the organic pollutants are different from the traditional biochemical sludge, and do not involve the removal of intracellular bound water, so the dehydration and drying are easier, and the sludge disposal process is relatively simple. In summary, the water purification method provided by the present application has low oxidant consumption, high organic pollutant removal efficiency and stable effluent, and can significantly reduce the energy consumption and cost of the oxidation water treatment process. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only represent some of the embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative effort based on the provided drawings are within the protection scope of the present application.

[0019] Figure 1 is a quantitative analysis diagram of the aggregated and precipitated sludge provided by the embodiment 2 of the present application;

[0020] Figure 2 is an actual application effect diagram provided by the embodiment 3 of the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present application.

[0022] The present application provides a water purification method of pollutant aggregation and precipitation sludge, comprising the following steps:

[0023] The catalyst and hydrogen peroxide are added to the wastewater to perform catalytic oxidation reaction, so that the hydrophobicity of the organic pollutant molecules in the water is increased and the organic pollutant molecules are aggregated to form solid sludge. Then, standing and precipitation are performed, and the sludge and water are separated to obtain clean water.

[0024] The catalyst is an iron-sulfur compound, and the chemical general formula is Fe x S y .

[0025] In the method provided by the present application, the organic pollutants of the wastewater include but are not limited to one or more of phenol, aniline, chlorophenol, bisphenol A, sulfonamide, chloroaniline and thiophene.

[0026] In the method provided by the present application, the COD of the wastewater is preferably 2000-10000 mg / L, and specifically can be 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, 4000 mg / L, 4091 mg / L, 4350 mg / L, 4500 mg / L, 5000 mg / L, 5500 mg / L, 6000 mg / L, 6500 mg / L, 7000 mg / L, 7500 mg / L, 8000 mg / L, 8042 mg / L, 8500 mg / L, 9000 mg / L, 9500 mg / L or 10000 mg / L. In the method provided by the present application, the COD of the wastewater is preferably 2000-10000 mg / L, and specifically can be 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, 4000 mg / L, 4091 mg / L, 4350 mg / L, 4500 mg / L, 5000 mg / L, 5500 mg / L, 6000 mg / L, 6500 mg / L, 7000 mg / L, 7500 mg / L, 8000 mg / L, 8042 mg / L, 8500 mg / L, 9000 mg / L, 9500 mg / L or 10000 mg / L.

[0027] In the method provided by the present application, the catalyst is a compound with different Fe:S molar ratios, such as Fe 0.8 S 0.2 or Fe 0.6 S 0.4 The particle size of the catalyst is preferably 50 nm to 10 μm, and can be specifically 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm; and the addition amount of the catalyst in the wastewater is preferably 0.1 to 5 g / L, and can be specifically 0.1 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L or 5 g / L.

[0028] In the method provided by the present application, the addition concentration of the hydrogen peroxide in the wastewater is preferably 3 to 5 times of the molar concentration of the organic pollutants in the wastewater, and can be specifically 3 times, 3.25 times, 3.5 times, 3.75 times, 4 times, 4.25 times, 4.5 times, 4.75 times or 5 times.

[0029] In the method provided by the present application, the pH value of the catalytic oxidation reaction is preferably 3 to 5, and can be specifically 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5. In the present application, if the pH value of the wastewater does not meet the pH value requirement of the catalytic oxidation reaction, sulfuric acid is preferably added to the wastewater for pH adjustment.

[0030] In the method provided by the present application, the temperature of the catalytic oxidation reaction is preferably 10 to 40℃, and can be specifically 10℃, 15℃, 20℃, 25℃ (room temperature), 30℃, 35℃ or 40℃; and the time of the catalytic oxidation reaction is preferably in the order of minutes to hours.

[0031] The water purification method provided by the present application can convert the organic pollutants from degradation mineralization gas production to aggregation precipitation sludge production, can effectively reduce the amount of oxidant under the condition of ensuring high and stable removal efficiency of effluent COD, thereby significantly reducing the energy consumption and cost of the oxidation water treatment process, and has a wide practical application prospect.

[0032] For a clearer understanding, the following examples are provided for further illustration.

[0033] In the following examples of the present application, the operations are all carried out at room temperature (25℃) and normal pressure (1 atm) unless otherwise specified.

[0034] Example 1

[0035] In a beaker with a volume of 100 mL, 80 mL of aniline solution with an initial COD of 8000 mg / L was added, the pH was adjusted to 4.0 with sulfuric acid, and then 0.08 g of Fe 0.8 S 0.2 powder (particle size 200 nm) was added, ultrasonic dispersion was performed, and stirring was performed uniformly with a stirring paddle at a speed of 200 revolutions / min; then 0.64 mL of a hydrogen peroxide mother liquor (mass fraction 30%) was added, the reaction was started, and the initial concentration of hydrogen peroxide in the reaction solution was 3.25 times the molar concentration of aniline.

[0036] Sampling test time points during the reaction: 0, 10, 30, 60, 120, and 180 min.

[0037] During the reaction, the COD of the samples (suspensions) taken at the above time points was detected, and the COD removal rate of the suspension was calculated; at the same time, the aniline content and COD of the clear liquid obtained after the samples were filtered with 5000-mesh filter cloth were detected, and the aniline removal rate and the COD removal rate of the clear liquid were calculated. The results are shown in Table 1.

[0038] Table 1 Aniline in water after treatment in Example 1, COD of the clear liquid, and COD removal rate of the suspension

[0039] Time (min) 0 10 30 60 120 180 Aniline removal 0 76.6％ 79.7％ 81.4％ 83.4％ 86.1％ Effluent COD removal 0 68.3％ 70.3％ 72.6％ 76.9％ 80.1％ Suspended solids COD removal 0 18.5％ 19.5％ 19.4％ 18.8％ 19.7％

[0040] Example 2

[0041] Experimental group: In a blue beaker with a volume of 500 mL, 400 mL of aniline solution with an initial COD of 8042 mg / L (simulated wastewater, the mass of aniline was 1.2916 g) was added, the pH was adjusted to 4.2 with sulfuric acid, and then 0.9999 g of Fe 0.8 S 0.2 powder (particle size 200 nm) was added, ultrasonic dispersion was performed, and stirring was performed uniformly with a stirring paddle at a speed of 200 revolutions / min; then 3.2 mL of a hydrogen peroxide mother liquor (mass fraction 30%) was added, the reaction was started, and the initial concentration of hydrogen peroxide in the reaction solution was 3 times the molar concentration of aniline; after the reaction, the pH was adjusted to about 7.0 with sodium hydroxide, precipitation was allowed to stand, the supernatant was filtered with a 0.22-micron hydrophilic PTFE filter head, and the COD of the water was tested to be 1760 mg / L; the bottom precipitate was collected by centrifugation, dried at 60 degrees for 12 hours, and the total mass of the solid produced after the reaction was weighed to be 2.0522 g.

[0042] Control group: the aniline solution in the reaction system of the experimental group was replaced with water, i.e., hydrogen peroxide directly oxidized the catalyst, and the mass of the oxidized catalyst was collected to be 1.1022 g.

[0043] The experimental and control groups showed that the mass increase rate of solids during the pollutant reaction process was (2.0522-1.1022) / 1.2916 = 73.6%; the COD removal rate in the water was (8042-1760) / 8042 = 78.1%, indicating that organic pollutants in the water were mainly removed in the form of solid sludge.

[0044] Example 3

[0045] In a volume of 1.5m 3 1.2 m³ of rubber additive wastewater with a pH of 3.8 was injected into the reactor. 3 (Initial COD was 4091 mg / L), Fe was added. 0.8 S 0.2 0.6 kg of powder (particle size 200 nm) was mixed with a bottom-up inclined plate stirrer (stirring speed 50 rpm) to ensure uniform mixing of the catalyst and wastewater. Then, 4.8 L of 27% industrial-grade hydrogen peroxide was added to initiate the reaction. After 1 hour of reaction, 40 wt% concentrated sodium hydroxide was added to the reactor to adjust the pH to approximately 7.0, and then the mixture was allowed to stand for 1 day. After standing, the mud and water separated into layers. The clear water at the top was discharged through three drain outlets from top to bottom, while the mud and water at the bottom was discharged through the drain outlet at the bottom.

Claims

1. A method for purifying water from pollutants by aggregate sedimentation of sludge, characterized in that, The method comprises the following steps: adding a catalyst and hydrogen peroxide into the wastewater to perform a catalytic oxidation reaction, so that the hydrophobicity of organic pollutant molecules in the wastewater is increased and the organic pollutant molecules are aggregated to form solid sludge; then, standing and sedimentation are performed, and the sludge and water are separated, so that clean water is obtained; The catalyst is an iron sulfur compound, chemical formula Fe 0.8 S 0.2 or Fe 0.6 S 0.4 .

2. The water purification method according to claim 1, characterized by, the adding amount of the catalyst in the wastewater is 0.1-5 g / L.

3. The water purification method according to claim 1, characterized by, the particle size of the catalyst is 50 nm-10 μm.

4. The water purification method according to claim 1, characterized by, the adding concentration of the hydrogen peroxide in the wastewater is 3-5 times of the molar concentration of the organic pollutants in the wastewater.

5. The water purification method according to claim 1, characterized by, the pH value of the catalytic oxidation reaction is 3-5.

6. The water purification method according to claim 5, characterized by, if the pH value of the wastewater does not meet the pH value requirement of the catalytic oxidation reaction, sulfuric acid is added into the wastewater to adjust the pH value.

7. The water purification method according to claim 1, characterized by, the temperature of the catalytic oxidation reaction is 10-40 ℃.

8. The water purification method of claim 1, wherein, the organic pollutants include one or more of phenol, aniline, chlorophenol, bisphenol A, sulfonamide, chloroaniline and thiophene.

9. The water purification method of claim 1, wherein, the COD of the wastewater is 2000-10000 mg / L.

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