Water purification method for producing sludge by gathering and precipitating pollutants

Abstract

The invention belongs to the technical field of water pollution control, and particularly relates to a water purification method for producing sludge through pollutant aggregation and precipitation, which comprises the following steps: adding a FexSy catalyst and hydrogen peroxide into wastewater to carry out catalytic oxidation reaction, so that the hydrophobicity of organic pollutant molecules in water is increased, and the organic pollutant molecules are aggregated to form solid sludge; and then carrying out static settlement and mud-water separation to obtain clear water. According to the water purification method provided by the invention, organic pollutants are converted from degradation mineralization gas production to weak oxidation aggregation precipitation mud production, and the dosage of an oxidizing agent is effectively reduced under the condition of ensuring that the COD (Chemical Oxygen Demand) of effluent reaches the standard and is stable, so that the energy consumption and the cost of an oxidation water treatment process are remarkably reduced, and the method has a wide practical application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of water pollution control, and in particular relates to a water purification method for pollutants that accumulate and precipitate to produce mud. Background Art

[0002] Advanced oxidation (AOP) methods, represented by Fenton oxidation technology, have long attracted wide attention in the field of physical and chemical water treatment. 2+ ) activates oxidants (such as H2O2) to produce highly active oxidative species intermediates, such as hydroxyl radicals, to degrade mineralized organic pollutants. Due to their potential for treating highly toxic and difficult-to-degrade organic pollutants, they are widely used in detoxification pretreatment and deep purification of industrial wastewater.

[0003] However, advanced oxidation methods represented by Fenton always have the problem of high energy consumption and high cost caused by the large amount of oxidant added, among which the cost of oxidant accounts for more than 60% of the cost of oxidation water treatment process. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a water purification method in which pollutants aggregate and precipitate to produce sludge, which has the advantages of high organic pollutant removal efficiency, low oxidant consumption, and stable effluent.

[0005] The present invention provides a water purification method in which pollutants are accumulated and precipitated to produce sludge, comprising the following steps:

[0006] Adding catalyst and hydrogen peroxide to the wastewater for catalytic oxidation reaction increases the hydrophobicity of pollutant molecules and aggregates them to form solid sludge; then standing and settling, mud and water are separated to obtain clean water;

[0007] The catalyst is an iron-sulfur compound with a general chemical formula of 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 catalyst is added to the wastewater in an amount of 0.1 to 5 g / L.

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

[0011] Preferably, the concentration of hydrogen peroxide added to the wastewater is 3 to 5 times the molar concentration of 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 to adjust the pH.

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

[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 2000-10000 mg / L.

[0017] Compared with the prior art, the present invention provides a water purification method in which pollutants are aggregated and precipitated to form sludge, comprising the following steps: adding Fe x S y The catalyst and hydrogen peroxide undergo a catalytic oxidation reaction, so that the organic pollutant molecules in the water are weakly oxidized under the conditions of the catalyst and the oxidant, reducing the proportion of hydrophilic functional groups such as hydroxyl, amino, thiol, etc., increasing the hydrophobicity of the molecules, and facilitating their aggregation and precipitation to form solid sludge; then static sedimentation is performed, mud and water are separated, and clean water is obtained. In order to effectively reduce the amount of oxidant used while improving the water treatment effect, the present invention innovates the reaction path of advanced oxidation technology, converts the degradation and mineralization gas production of organic pollutants into aggregation and precipitation mud production, and then performs simple separation and removal. Through this method, there is no need to destroy various chemical bonds (such as CC bonds) in the organic pollutant molecules, but only weak oxidation of the organic molecules, thereby significantly reducing the consumption of oxidants. Compared with traditional degradation and mineralization methods, aggregation and precipitation mud production can reduce the amount of oxidant used by 1 to 3 orders of magnitude. Taking phenol as an example, if a degradation and mineralization reaction is carried out, 1 mole of phenol needs to release 28 moles of electrons and consume more than about 14 moles of H2O2 (the reaction is: 1PhOH→6CO2+3H2O(small molecule product)+28e-); in the aggregation and precipitation sludge reaction, 1 mole of phenol releases 2 to 6 moles of electrons, converting the hydroxyl group into a carbonyl group or an ether bond, consuming about 1 to 3 moles of H2O2. Through this weak oxidation reaction and change in hydrophilicity and hydrophobicity, the organic pollutants in the water aggregate and precipitate to produce sludge, and finally through solid-liquid separation, clean water is discharged. In addition, the main components of the sludge generated by the method of the present invention are Fe x S y The aggregates of catalysts and organic pollutants are different from traditional biochemical sludge, and do not involve the removal of bound water in cells, making dehydration and drying easier, and the sludge disposal process is relatively simple. In summary, the water purification method provided by the present invention has low oxidant dosage, high organic pollutant removal efficiency, stable effluent, and can significantly reduce the energy consumption and cost of the oxidation water treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 This is a quantitative analysis diagram of the aggregated sedimentation sludge produced according to Example 2 of the present invention;

[0020] Figure 2 This is a practical application effect diagram provided by Example 3 of the present invention. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The present invention provides a water purification method in which pollutants are accumulated and precipitated to produce sludge, comprising the following steps:

[0023] Adding catalyst and hydrogen peroxide to the wastewater for catalytic oxidation reaction increases the hydrophobicity of organic pollutant molecules in the water and aggregates to form solid sludge; then standing and settling, mud and water separation, to obtain clean water;

[0024] The catalyst is an iron-sulfur compound with a general chemical formula of Fe x S y .

[0025] In the method provided by the present invention, the organic pollutants in 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 invention, the COD of the wastewater is preferably 2000-10000 mg / L, specifically 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 invention, 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 50nm~10μm, specifically 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm; The amount of the catalyst added to the wastewater is preferably 0.1~5g / L, specifically 0.1g / L, 0.5g / L, 1g / L, 1.5g / L, 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, 4.5g / L or 5g / L.

[0028] In the method provided by the present invention, the concentration of hydrogen peroxide added to the wastewater is preferably 3 to 5 times the molar concentration of organic pollutants in the wastewater, 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 invention, the pH value of the catalytic oxidation reaction is preferably 3 to 5, 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 invention, 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 invention, the temperature of the catalytic oxidation reaction is preferably 10-40°C, specifically 10°C, 15°C, 20°C, 25°C (room temperature), 30°C, 35°C or 40°C; 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 invention converts organic pollutants from degradation and mineralization to gas production into aggregation and precipitation to sludge production. It can effectively reduce the amount of oxidant used while ensuring high and stable COD removal efficiency in the effluent, thereby significantly reducing the energy consumption and cost of the oxidation water treatment process, and has broad practical application prospects.

[0032] For the purpose of greater clarity, the invention is described in detail through the following examples.

[0033] In the following examples of the present invention, unless otherwise specified, operations were carried out at room temperature (25° C.) and normal pressure (1 atm).

[0034] Example 1

[0035] In a 100 mL beaker, add 80 mL of aniline solution with an initial COD of 8000 mg / L, adjust the pH to 4.0 with sulfuric acid, and then add 0.08 g of Fe 0.8 S 0.2 The powder (particle size 200 nm) was ultrasonically dispersed and stirred at 200 rpm with a stirring paddle, and then 0.64 mL of hydrogen peroxide mother solution (mass fraction 30%) was added to start the reaction. The initial concentration of hydrogen peroxide in the reaction solution was 3.25 times the molar concentration of aniline.

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

[0037] During the reaction, the COD of the sample (suspension) taken at the above time point 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 sample was filtered with a 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 Removal rates of aniline, clear COD and suspended COD in treated water in Example 1

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

[0040] Example 2

[0041] Experimental group: 400 mL of aniline solution (simulated wastewater, 1.2916 g of aniline) with an initial COD of 8042 mg / L was added to a 500 mL blue-mouth bottle, the pH was adjusted to 4.2 with sulfuric acid, and then 0.9999 g of Fe 0.8 S 0.2 The powder (particle size 200nm) was ultrasonically dispersed and stirred evenly with a stirring paddle at a speed of 200 rpm; then 3.2mL of hydrogen peroxide mother solution (mass fraction 30%) was added thereto to start the reaction, 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, and the solution was allowed to stand and precipitate, and the supernatant was filtered with a 0.22 micron hydrophilic PTFE filter head, and the COD in the water was tested to be 1760mg / L; the precipitate at the bottom 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 2.0522g.

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

[0043] Through the experimental group and the control group, it can be calculated that the mass increase rate of solids during the pollutant reaction process is (2.0522-1.1022) / 1.2916=73.6%; the COD removal rate in water is (8042-1760) / 8042=78.1%, indicating that organic pollutants in water are mainly removed in the form of solid sludge.

[0044] Example 3

[0045] In a volume of 1.5m 3 1.2 m of rubber additive wastewater with a pH of 3.8 was injected into the reactor. 3 (initial COD is 4091 mg / L), Fe is added 0.8 S 0.2 0.6 kg of powder (particle size 200 nm) was added, and the inclined plate stirring from bottom to top was turned on to evenly mix the catalyst and the wastewater (stirring speed 50 rpm), and then 4.8 L of industrial-grade hydrogen peroxide with a mass fraction of 27% was added thereto to react; after reacting for 1 hour, 40 wt % of concentrated sodium hydroxide was added to the reactor to adjust the pH to about 7.0, and then allowed to stand for 1 day; after standing, the mud and water were separated into layers, and the clear water on the upper layer was discharged through three drainage ports from top to bottom, and the mud and water at the bottom were discharged through the drainage port at the bottom.

Claims

1. A method for purifying water from which pollutants accumulate and precipitate to form sludge, characterized in that: The following steps are involved: Adding catalyst and hydrogen peroxide to the wastewater for catalytic oxidation reaction increases the hydrophobicity of organic pollutant molecules in the water and aggregates to form solid sludge; then standing and settling, mud and water separation, to obtain clean water; The catalyst is an iron-sulfur compound with a general chemical formula of Fe x S y .

2. The water purification method according to claim 1, characterized in that: The catalyst is Fe 0.8 S 0.2 or Fe 0.6 S 0.4 .

3. The water purification method according to claim 1, characterized in that: The catalyst is added in an amount of 0.1 to 5 g / L in wastewater.

4. The water purification method according to claim 1, characterized in that: The particle size of the catalyst is 50 nm to 10 μm.

5. The water purification method according to claim 1, characterized in that: The concentration of hydrogen peroxide added to the wastewater is 3 to 5 times the molar concentration of organic pollutants in the wastewater.

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

7. The water purification method according to claim 6, characterized in that: 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 to adjust the pH.

8. The water purification method according to claim 1, characterized in that: The temperature of the catalytic oxidation reaction is 10-40°C.

9. The water purification method according to claim 1, characterized in that: The organic pollutants include one or more of phenol, aniline, chlorophenol, bisphenol A, sulfonamide, chloroaniline and thiophene.

10. The water purification method according to claim 1, characterized in that: The COD of the wastewater is 2000-10000 mg / L.

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