A method for treating vat dyeing wastewater

Abstract

The present invention relates to the technical field of printing and dyeing wastewater treatment, and specifically discloses a method for treating vat dye wastewater, comprising the following steps: subjecting the vat dye wastewater to an electroflocculation treatment, sequentially adding an adsorbent and a hydroxy silicone oil emulsion to the treated wastewater for flocculation and precipitation treatment in stages; wherein the adsorbent is diatomaceous earth or diatomaceous earth modified with an aminosilane coupling agent. The method for treating vat dye wastewater provided by the present invention utilizes a diatomaceous earth adsorbent in conjunction with a hydroxy silicone oil emulsion to promote the adsorption, coupling, and re-flocculation of flocs generated by the electroflocculation reaction, effectively enhancing the structure of the flocs, increasing the specific gravity of the flocs, increasing the flocculation speed, and shortening the sedimentation time, thereby significantly improving the treatment effect and efficiency. The national emission standards can be met through simple filtration, and the process is simple, does not require special equipment, is low in cost, has high applicability, does not cause secondary pollution, and has high practicality.

Description

Technical Field

[0001] The invention relates to the technical field of printing and dyeing wastewater treatment, in particular to a method for treating vat dyeing wastewater. Background Art

[0002] Vat dyes themselves cannot be directly dissolved in water. They must first be reduced with a reducing agent in an alkaline solution to form a water-soluble leuco dye. The dye then uses the affinity of the leuco dye sodium salt for the fiber. Because a large amount of reducing agent is used during dyeing, the redox potential of the wastewater from vat dyeing is negative, and the ions in the wastewater are highly negatively charged.

[0003] As a green and efficient water treatment technology, electrochemical flocculation has been widely used in various wastewater treatments, such as printing and dyeing wastewater, domestic wastewater, heavy metal wastewater, etc. The principle of electrocoagulation is to use metal materials (iron, aluminum, stainless steel, etc.) as sacrificial anodes. Under certain voltage conditions, the metal anodes undergo electrolysis to produce metal cations, which react with the )OH generated at the cathode. - Hydroxide microflocculation forms, which, through charge neutralization, form larger flocs, accelerating the adsorption and deposition of pollutants. However, the flocs produced by electrochemical flocculation have a relatively loose structure, resulting in poor flocculation effect and long settling time. This results in poor wastewater treatment effectiveness and low treatment efficiency using electroflocculation.

[0004] At present, in order to improve the effect of electroflocculation in treating wastewater, most of the methods are optimized in terms of treatment equipment. For example, there are literature reports that by setting a device integrating an electroflocculation zone, a reaction zone, a sedimentation zone, and a clear water zone, the flocculation-clarification process is ensured to proceed smoothly and the electroflocculation treatment effect is improved. There are also literature reports that in the electroflocculation wastewater treatment process, magnetic powder is added to the wastewater to form flocs with the magnetic powder as coagulation nuclei, strengthen the flocculation effect, and improve the sedimentation efficiency. However, the above method has a high processing cost and requires a special device to operate, and its applicability is not high. Therefore, it is urgently needed to develop a method for treating vat dyeing wastewater with a high processing efficiency and good flocculation effect at a low cost. Summary of the Invention

[0005] To address the problems of existing electroflocculation treatment of vat dye wastewater, such as poor treatment effects, low treatment efficiency, high treatment costs, and poor applicability, the present invention provides a method for treating vat dye wastewater. This method adds diatomaceous earth or modified diatomaceous earth to the wastewater treated by electroflocculation, along with hydroxyl silicone oil, to enhance the floc structure and stability, promote floc aggregation, improve wastewater treatment effectiveness, and effectively shorten the electroflocculation time.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] A method for treating vat dyeing wastewater comprises subjecting the vat dyeing wastewater to electric flocculation treatment, sequentially adding an adsorbent and a hydroxy silicone oil emulsion to the treated wastewater for flocculation and precipitation treatment in stages; wherein the adsorbent is diatomaceous earth or diatomaceous earth modified with an aminosilane coupling agent.

[0008] Compared with the prior art, the present invention provides a method for treating vat dyeing wastewater. First, a specific diatomaceous earth adsorbent is added to the vat dyeing wastewater after electroflocculation treatment. Through the net capture and sweeping action of the diatomaceous earth adsorbent, the suspended matter generated by the electroflocculation is aggregated into flocs with larger particle sizes. Then, by adding a hydroxy silicone oil emulsion, the chargeability and linear molecular structure of the hydroxy silicone oil are utilized to further aggregate the aforementioned flocs with larger particle sizes into coarse aggregates through bridging, forming one-dimensional or two-dimensional linear spherical clusters. The coarse aggregates formed by the hydroxy silicone oil bridging are structurally stable, which can avoid structural damage of the flocs during the sedimentation process, thereby achieving rapid sedimentation and improving the treatment effect. The present invention can not only significantly improve the treatment efficiency of electroflocculation, but also significantly reduce the COD value and chromaticity of the wastewater. No special treatment equipment is required, which significantly reduces the treatment cost. It has high economic, environmental and social benefits and is extremely valuable.

[0009] For example, the vat dyeing wastewater in the present invention may be indigo dyeing wastewater.

[0010] Preferably, the method for treating vat dyeing wastewater specifically comprises the following steps: adding the vat dyeing wastewater into an electrolytic cell, performing electric flocculation under stirring conditions, adding an adsorbent to the wastewater after the electric flocculation is completed, stirring and adsorbing, stopping stirring after the adsorption is completed, adding hydroxyl silicone oil emulsion, allowing to settle, filtering, and draining after testing.

[0011] The method for treating vat dyeing wastewater provided by the present invention can significantly improve the sedimentation rate of flocs in the wastewater treated by electroflocculation. After treatment, the COD value and chroma of the wastewater are significantly reduced, meeting national emission standards. No special equipment is required, the operation is simple, and the cost is low. The method can be applied to the treatment of actual industrial vat dyeing wastewater, provides a new energy-saving and efficient treatment process route for the treatment of vat dyeing wastewater, and has extremely high promotion and application value.

[0012] Preferably, the aminosilane coupling agent modified diatomaceous earth is 3-aminopropyltrimethoxysilane modified diatomaceous earth.

[0013] In further combination with the above, the preparation method of the aminosilane coupling agent modified diatomaceous earth includes the following steps: adding diatomaceous earth to a sulfuric acid solution and dispersing it evenly, keeping it at 55°C-65°C for a reaction of 2.5h-3.5h, washing, and calcining to obtain acidified diatomaceous earth; then dispersing the acidified diatomaceous earth in an organic solvent, adding an aminosilane coupling agent, reacting it at 85°C-95°C for 11h-13h, washing, and drying to obtain aminosilane coupling agent modified diatomaceous earth.

[0014] Modifying diatomaceous earth with a preferred aminosilane coupling agent can significantly enhance the coupling effect between diatomaceous earth and flocs generated by the electroflocculation reaction, strengthen the structural stability of the flocs, improve the flocculation effect, and shorten the sedimentation time of the flocs.

[0015] In combination with the above, the calcination temperature is 550° C.-650° C., and the calcination time is 5 h-7 h.

[0016] In combination with the above, the organic solvent is toluene.

[0017] In combination with the above, the mass ratio of the aminosilane coupling agent to the acidified diatomaceous earth is 1-2:1-2.

[0018] Optionally, the sulfuric acid solution has a concentration of 4.5 mol / L-5.5 mol / L.

[0019] Optionally, the mass volume ratio of the diatomaceous earth to the sulfuric acid solution is 25-35 g:100-200 mL.

[0020] Optionally, the mass volume ratio of the acidified diatomaceous earth to the organic solvent is 1-2 g:100-200 mL.

[0021] Preferably, the mesh size of the diatomaceous earth is 800-1200 mesh.

[0022] The preferred modification conditions of diatomaceous earth can promote the full reaction between diatomaceous earth and aminosilane coupling agent, thereby improving the flocculation effect of diatomaceous earth, strengthening the floc structure, and improving the wastewater treatment effect.

[0023] Preferably, the mass-to-volume ratio of the adsorbent to the vat dyeing wastewater is 0.8-1.2:1, wherein the unit of mass is gram and the unit of volume is liter.

[0024] Furthermore, the mass volume ratio of the adsorbent to the vat dyeing wastewater is 1g:1L.

[0025] Preferably, the addition amount of the hydroxy silicone oil emulsion is 0.05%-0.15% of the solid content of the vat dyeing wastewater.

[0026] Furthermore, the addition amount of the hydroxy silicone oil emulsion is 0.08% of the solid content of the vat dyeing wastewater.

[0027] The preferred amount of hydroxy silicone oil emulsion added can reduce processing costs while ensuring that all flocs are quickly settled.

[0028] Optionally, the hydroxy silicone oil emulsion is an anionic hydroxy silicone oil emulsion, a cationic hydroxy silicone oil emulsion, a nonionic hydroxy silicone oil emulsion, a hydroxy silicone oil emulsion of a combination of cationic and nonionic hydroxy silicone oil emulsion, or a hydroxy silicone oil emulsion of a combination of anionic and nonionic hydroxy silicone oil emulsion.

[0029] Preferably, the voltage of the electrocoagulation is 5V-10V, and the time of the electrocoagulation is 5min-10min.

[0030] Furthermore, the voltage of the electrocoagulation is 7V, and the time of the electrocoagulation is 10 minutes.

[0031] Preferably, the stirring speed during the electroflocculation process is 150 r / min-210 r / min.

[0032] For example, the cathode and anode electrode materials for the electrocoagulation treatment can both be made of aluminum sheets and a DC regulated power supply.

[0033] The optimal voltage and electro-flocculation time can ensure the full electro-oxidation reaction of the reduced dyes and other substances, and at the same time, can promote the collision and aggregation of the dyes in the wastewater, thereby improving the electro-flocculation treatment efficiency and treatment effect.

[0034] Preferably, the rotation speed of the stirring adsorption is 150 r / min-210 r / min, and the time of the stirring adsorption is 2 min-4 min.

[0035] Furthermore, the stirring adsorption speed is 180 r / min, and the stirring adsorption time is 3 min.

[0036] The optimal stirring speed and time can promote the diatomaceous earth to fully capture the flocs generated in the electro-flocculation process and form flocs with larger particle sizes.

[0037] Preferably, the settling time is 2 min to 3 min.

[0038] The present invention provides a method for treating vat dyeing wastewater, which utilizes a diatomaceous earth adsorbent in conjunction with a hydroxy silicone oil emulsion to promote the adsorption, coupling, and re-flocculation of flocs generated by an electric flocculation reaction, effectively enhancing the structure of the flocs, increasing the specific gravity of the flocs, improving the flocculation speed, and shortening the sedimentation time, thereby significantly improving the treatment effect and efficiency. The method can meet national emission standards through simple filtration, and the process is simple, does not require special equipment, is low in cost, has high applicability, will not cause secondary pollution, and has high practicality. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] COD test: According to HJ / T399-2007 "Rapid determination of chemical oxygen demand in water - rapid digestion spectrophotometry", take 3 mL of treated water sample and use LY-X12 digester to digest the water sample for 10 minutes, and measure the COD of the water sample.

[0041] Chroma test: According to HJ 1182-2021 "Dilution multiple method for the determination of chroma of water quality", the dilution multiple method is used to take the treated supernatant to determine the chroma value of the treated wastewater.

[0042] Example 1

[0043] A method for treating indigo dyeing wastewater:

[0044] 250 mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1 mm) were used as the anode and cathode electrode materials. A DC regulated power supply was used to apply a voltage of 7 V. The electrolysis was stirred for 10 minutes. The plate spacing was 3 cm. After the electroflocculation was completed, 1.0 g / L of diatomaceous earth was added and stirred for 2 minutes. The stirring speed of the whole process was 180 r / min. Then the stirring was stopped and a cationic hydroxyl silicone oil emulsion with a solid content of 0.09% of the indigo dyeing wastewater was added. The flocs were completely precipitated in 132 seconds.

[0045] The supernatant after precipitation was taken to test the COD of the treated indigo dyeing wastewater, which was 180.8 mg / L and the chroma was 30.

[0046] Example 2

[0047] A method for treating indigo dyeing wastewater:

[0048] 250 mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1 mm) were used as the cathode and anode electrode materials. A DC regulated power supply was used to apply a voltage of 5 V. The electrolysis was stirred for 10 minutes. The plate spacing was 3 cm. After the electroflocculation was completed, 0.8 g / L of diatomaceous earth was added and stirred for 3 minutes. The stirring speed of the whole process was 210 r / min. Then the stirring was stopped and a cationic hydroxyl silicone oil emulsion with a solid content of 0.05% of the indigo dyeing wastewater was added. The flocs were completely precipitated in 146 seconds.

[0049] The supernatant after precipitation was taken to test the COD of the treated indigo dyeing wastewater, which was 192.3 mg / L and the chroma was 30.

[0050] Example 3

[0051] A method for treating indigo dyeing wastewater:

[0052] 250 mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1 mm) were used as the anode and cathode electrode materials. A DC regulated power supply was used to apply a voltage of 10 V. The electrolysis was stirred for 5 minutes. The plate spacing was 3 cm. After the electroflocculation was completed, 1.2 g / L of diatomaceous earth was added and stirred for 2 minutes. The stirring speed of the whole process was 150 r / min. Then the stirring was stopped and a cationic hydroxyl silicone oil emulsion with a solid content of 0.15% of the indigo dyeing wastewater was added. The flocs were completely precipitated in 138 seconds.

[0053] The supernatant after precipitation was taken to test the COD of the treated indigo dyeing wastewater, which was 183.7 mg / L and the chroma was 30.

[0054] Example 4

[0055] A method for treating indigo dyeing wastewater:

[0056] 250 mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1 mm) were used as the anode and cathode electrode materials. A DC regulated power supply was used to apply 8 V voltage. The electrolysis was stirred for 8 minutes. The plate spacing was 3 cm. After the electroflocculation was completed, 0.9 g / L of diatomaceous earth was added and stirred for 4 minutes. The stirring speed of the whole process was 170 r / min. Then the stirring was stopped and a cationic hydroxyl silicone oil emulsion with a solid content of 0.1% of the indigo dyeing wastewater was added. The flocs were completely precipitated in 143 seconds.

[0057] The supernatant after precipitation was taken to test the COD of the treated indigo dyeing wastewater, which was 190.4 mg / L and the chroma was 30.

[0058] Example 5

[0059] A method for treating indigo dyeing wastewater:

[0060] 250 mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1 mm) were used as the cathode and anode electrode materials. A DC regulated power supply was used to apply a voltage of 9 V. The electrolysis was stirred for 7 minutes with a plate spacing of 3 cm. After the electroflocculation was completed, 1.1 g / L of diatomaceous earth was added and stirred for 2 minutes. The stirring speed of the whole process was 200 r / min. Then the stirring was stopped and a cationic hydroxyl silicone oil emulsion with a solid content of 0.12% of the indigo dyeing wastewater was added. The flocs were completely precipitated in 160 seconds.

[0061] The supernatant after precipitation was taken to test the COD of the treated indigo dyeing wastewater, which was 189.6 mg / L and the chroma was 30.

[0062] Example 6

[0063] A method for treating indigo dyeing wastewater:

[0064] Preparation of 3-aminopropyltrimethoxysilane-modified diatomite: 30 g of diatomite was added to 150 mL of 5 mol / L sulfuric acid solution, dispersed evenly, and reacted at 60° C. for 3 h. The mixture was washed with deionized water until neutral, and calcined at 600° C. for 6 h to obtain acidified diatomite. Then, 1.5 g of the acidified diatomite was dispersed in 150 mL of toluene, 1.5 g of 3-aminopropyltrimethoxysilane was added, and the mixture was reacted at 90° C. for 12 h. After the reaction, the mixture was washed with toluene and ethanol, and then dried in a vacuum drying oven at 60° C. for 8 h to obtain 3-aminopropyltrimethoxysilane-modified diatomite.

[0065] 250 mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1 mm) were used as the anode and cathode electrode materials. A DC regulated power supply was used to apply a voltage of 7 V. The electrolysis was stirred for 10 minutes. The plate spacing was 3 cm. After the electrocoagulation was completed, 1.0 g / L of 3-aminopropyltrimethoxysilane-modified diatomaceous earth was added and stirred for 3 minutes. The stirring speed of the whole process was 180 r / min. Then the stirring was stopped and a cationic hydroxyl silicone oil emulsion with a solid content of 0.09% of the indigo dyeing wastewater was added. The flocs were completely precipitated in 122 seconds.

[0066] The supernatant after precipitation was taken to test the COD of the treated indigo dyeing wastewater, which was 176.9 mg / L and the chroma was 30.

[0067] In this embodiment, 3-aminopropyltrimethoxysilane-modified diatomaceous earth adopts other conditions specified in the present invention. As long as they are within the scope specified in the present invention, technical effects substantially equivalent to the above can be achieved.

[0068] Comparative Example 1

[0069] A method for treating indigo dyeing wastewater:

[0070] 250mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1mm) were used as the anode and cathode electrode materials. A DC regulated power supply was used to apply a voltage of 7V. The electrolysis was stirred for 10 minutes. The plate spacing was 3cm. Magnetic stirring was applied at a stirring speed of 180r / min. After complete sedimentation, the supernatant after precipitation was tested. The COD of the treated indigo dyeing wastewater was 319.7mg / L, the chroma was 80, and the complete sedimentation time was 28min.

[0071] Comparative Example 2

[0072] A method for treating indigo dyeing wastewater:

[0073] 250mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1mm) were used as the cathode and anode electrode materials. A DC regulated power supply was used to apply a voltage of 7V. The electrolysis was stirred for 10 minutes with a plate spacing of 3cm. After the electrocoagulation was completed, 1.0g / L of diatomaceous earth was added and stirred for 2 minutes. Magnetic stirring was applied during the entire reaction process at a stirring speed of 180r / min. After complete sedimentation, the supernatant after precipitation was tested. The COD of the treated indigo dyeing wastewater was 224.9mg / L, the chroma was 40, and the complete sedimentation time was 14min.

[0074] Comparative Example 3

[0075] A method for treating indigo dyeing wastewater:

[0076] 250mL of indigo dyeing wastewater was added to the electrolytic cell. Aluminum sheets (40×40×1mm) were used as the cathode and anode electrode materials. A DC regulated power supply was used to apply a voltage of 7V. The electrolysis was stirred for 10 minutes with a plate spacing of 3cm. After the electrocoagulation was completed, 1.0g / L of diatomaceous earth was added and stirred for 2 minutes. The stirring speed of the whole process was 180r / min. Then the stirring was stopped and a dimethyl hydrogen silicone oil emulsion with a solid content of 0.09% of the indigo dyeing wastewater was added. After complete sedimentation, the supernatant after precipitation was tested. The COD of the indigo dyeing wastewater after treatment was 239.1mg / L, the chroma was 40, and the complete sedimentation time was 16min.

[0077] In summary, the method for treating indigo dyeing wastewater provided by the embodiment of the present invention has a simple treatment process, high treatment efficiency, safety, environmental protection, and low cost. The treated wastewater can meet national emission standards after simple filtration, and has broad application prospects.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating vat dyeing wastewater, characterized in that: The method specifically comprises the following steps: adding vat dyeing wastewater into an electrolytic cell, performing electric flocculation under stirring conditions, adding an adsorbent to the wastewater, stirring and adsorbing, stopping stirring after the adsorption, adding hydroxyl silicone oil emulsion, standing and settling, filtering, and draining; wherein the adsorbent is diatomaceous earth or diatomaceous earth modified with an aminosilane coupling agent; the voltage of the electric flocculation is 5V-10V, and the time of the electric flocculation is 5min-10min.

2. The method for treating vat dyeing wastewater according to claim 1, wherein: The aminosilane coupling agent modified diatomaceous earth is 3-aminopropyltrimethoxysilane modified diatomaceous earth.

3. The method for treating vat dyeing wastewater according to claim 2, wherein: The preparation method of the aminosilane coupling agent modified diatomaceous earth comprises the following steps: adding diatomaceous earth into a sulfuric acid solution and uniformly dispersing the diatomaceous earth, keeping the temperature at 55°C-65°C for reaction for 2.5h-3.5h, washing, calcining, and obtaining acidified diatomaceous earth; then dispersing the acidified diatomaceous earth in an organic solvent, adding an aminosilane coupling agent, keeping the temperature at 85°C-95°C for reaction for 11h-13h, washing, and drying, and obtaining the aminosilane coupling agent modified diatomaceous earth.

4. The method for treating vat dyeing wastewater according to claim 3, wherein: The calcination temperature is 550° C.-650° C., and the calcination time is 5 h-7 h; and / or The organic solvent is toluene; and / or The mass ratio of the aminosilane coupling agent to the acidified diatomaceous earth is 1-2:1-2.

5. The method for treating vat dyeing wastewater according to claim 1, wherein: The mass-to-volume ratio of the adsorbent to the vat dyeing wastewater is 0.8-1.2:1, wherein the unit of mass is gram and the unit of volume is liter.

6. The method for treating vat dyeing wastewater according to claim 1, wherein: The added amount of the hydroxy silicone oil emulsion is 0.05%-0.15% of the solid content of the vat dyeing wastewater.

7. The method for treating vat dyeing wastewater according to claim 1, wherein: The rotation speed of the stirring adsorption is 150 r / min-210 r / min, and the time of the stirring adsorption is 2 min-4 min.

8. The method for treating vat dyeing wastewater according to claim 7, wherein: The time for the static precipitation is 2 min to 3 min.