Sulfide pollution control and resourceful treatment method based on conductive composite membrane coupling system

Abstract

The invention discloses a sulfide pollution control and resourceful treatment method based on a conductive composite membrane coupling system, and belongs to the technical field of wastewater treatment. By constructing a composite membrane coupling system, more than 99% of sulfur ions in the wastewater can be removed; a reaction product ZnS-NiS-ACF Power is loaded to the composite membrane, and the multifunctional catalytic membrane is successfully prepared; under the synergistic effect of visible light and PMS, the removal rate of the catalytic membrane on tetracycline reaches 87.0%, and the catalytic membrane shows excellent catalytic activity and PMS activation capacity. According to the invention, a membrane separation technology and an adsorption-catalytic oxidation technology are efficiently coupled, so that the dual targets of efficient removal and resource utilization of sulfides are achieved; pMS degradation pollutants are activated in a low-cost, efficient and environment-friendly manner. The method has the remarkable advantages of being high in treatment efficiency, low in operation cost, environmentally friendly and the like, is not only suitable for treatment of industrial wastewater and urban black and odorous water bodies, but also provides a new thought for development of catalytic materials and application of an advanced oxidation technology.

Description

Technical Field

[0001] The present invention provides a method for controlling sulfide pollution and resource treatment based on a conductive composite membrane coupling system, belonging to the technical field of wastewater treatment. It involves the construction of a conductive composite membrane coupling system, coupling membrane separation technology with the synergistic effect of adsorption-catalytic oxidation to achieve efficient removal of sulfide ions (S2-) in wastewater; it involves the recovery and utilization of sulfur resources, converting S2- in wastewater into a ZnS-NiS-ACF Powder catalyst, preparing a catalytic membrane, and using the prepared catalytic membrane to couple with the photocatalytic activation of persulfate (PMS) technology to efficiently degrade water pollutants. Background Art

[0002] Sulfide is one of the pollutants widely present in wastewater, mainly originating from the production processes of industries such as petrochemical, leather manufacturing, and papermaking, as well as the anaerobic treatment processes of sulfate or organic sulfur compounds. Dissolved sulfide is corrosive and easily damages steel, concrete, etc., causing economic losses and leaving potential safety hazards. At the same time, sulfide is easily converted into hydrogen sulfide (H2S) in water, producing a foul smell, harming the human respiratory, nervous, and other systems; increasing the morbidity and mortality of fish; and forming complexes with heavy metals, which will inhibit the growth of plant roots. In order to improve water quality, ensure drinking water safety, extend the life of equipment and pipelines, etc., effective measures must be taken to remove sulfide and control sulfide emissions. Traditional treatment methods include filtration, chemical, and biological methods, etc., but they all have disadvantages to varying degrees, such as high investment costs, inability to treat high-concentration wastewater, low treatment efficiency, and the need for secondary treatment. More importantly, these traditional processes usually directly remove sulfide ions by converting them into elemental sulfur or sulfate, resulting in two prominent problems: on the one hand, elemental sulfur is difficult to effectively recycle; on the other hand, the discharge of a large amount of sulfate will disrupt the sulfur cycle balance in nature, trigger new environmental problems, and cause waste of sulfur resources.

[0003] Transition metal sulfides (TMS) exhibit great potential in the catalytic field due to their unique optoelectronic properties. Among them, zinc sulfide (ZnS) has important application value in the field of photocatalytic degradation due to its unique optoelectronic properties and suitable band gap (~3.6 eV); nickel sulfide (NiS) has become a research hotspot in catalytic materials due to its rich Ni-S and Ni-Ni bond active sites. However, powdered catalysts have the inherent defect of being difficult to recycle. Loading the catalyst on a conductive composite membrane to achieve catalyst immobilization can also control membrane fouling through catalytic action. In recent years, advanced oxidation processes (AOPs) have received extensive attention due to their excellent efficacy in treating refractory organic pollutants. Among them, AOPs based on persulfate (PMS) are considered a highly practical treatment method because they can generate a large number of highly oxidizing reactive species after catalytic activation, and have the characteristics of high stability, low cost, and mild products. In terms of the reaction mechanism, the catalyst destroys the O-O bond in PMS through electron transfer, and then generates highly active sulfate radicals. In particular, due to the intrinsic photocatalytic activity of ZnS and NiS, this invention couples membrane catalysis with photocatalysis to improve the pollutant degradation efficiency and PMS activation rate of the system.

[0004] The present invention provides a method for sulfide pollution control and resource utilization based on a conductive composite membrane coupling system. This method innovatively proposes a technical route of "treating waste with waste": constructing a conductive composite membrane coupling system, using activated carbon felt powder (ACFPowder) as an adsorbent and carrier, and in-situ converting sulfide ions (S 2- ) in wastewater into ZnS-NiS-ACF Powde catalyst, which is loaded on a conductive composite membrane to form a catalytic membrane. This catalytic membrane is coupled with other treatment technologies for the removal of refractory pollutants in wastewater, and a treatment system integrating sulfide removal, resource recovery, and catalytic degradation is successfully constructed. It not only eliminates the risk of hydrogen sulfide generation and achieves the purpose of pollutant removal, but also realizes the resource utilization of metal ions and sulfides, and is applicable to various scenarios such as industrial wastewater and urban black and odorous water bodies. Currently, there are no reports on similar conductive composite membrane coupling systems at home and abroad that can simultaneously achieve sulfide pollution control and resource utilization. Summary of the Invention

[0005] Aiming at the problems of difficult treatment of sulfide pollution and resource waste in wastewater, the present invention constructs a conductive composite membrane coupling system. This method uses membrane separation coupled with adsorption-catalytic oxidation to treat sulfur-containing wastewater, and innovatively converts sulfide ions (S 2-)In-situ conversion into ZnS-NiS-ACF Powder catalyst to achieve the recovery of sulfur resources. The catalyst is loaded on a conductive composite membrane to prepare a catalytic membrane, which can not only efficiently activate persulfate (PMS) to degrade refractory organic pollutants in wastewater, but also act as a functional electrode to synergistically act with advanced oxidation technologies such as photocatalysis and electrocatalysis, providing an innovative solution for the optimization of the sewage treatment system.

[0006] The technical solution of the present invention:

[0007] A method for controlling sulfide pollution and resource treatment based on a conductive composite membrane coupling system, the steps are as follows:

[0008] (1) Preparation of a conductive composite membrane:

[0009] Prepare a casting solution with polyvinylidene fluoride (PVDF) as the binder, nano-carbon fiber as the conductive reinforcing phase, and polyvinylpyrrolidone (PVP) as the pore-forming agent, and use the phase inversion method to prepare a conductive composite membrane on a carbon fiber cloth substrate; fix the conductive composite membrane on the membrane module for later use.

[0010] (2) Construction of the conductive composite membrane coupling system

[0011] Treat the sulfide-containing wastewater with one of the following schemes to in-situ generate ZnS-NiS-ACF Powder catalyst on the activated carbon felt powder ACF Powder to form a suspension. The specific scheme is as follows:

[0012] The first scheme, add ACF Powder to the sulfide-containing wastewater, stir to reach the adsorption / desorption equilibrium to effectively adsorb the sulfide ion (S 2- ) in the sulfide-containing wastewater. Subsequently, add a solution containing metal ions Zn 2+ and Ni 2+ , and insert an aeration head into the sulfide-containing wastewater to provide dissolved oxygen and mechanical external force through aeration to promote the oxidation process in the reaction system.

[0013] The second scheme, first add ACF Powder to a solution containing metal ions Zn 2+ and Ni 2+ , carry out adsorption and reach equilibrium, then add the sulfide-containing wastewater, and finally turn on the aeration pump for reaction.

[0014] (3) Preparation of ZnS-NiS-ACF Powder catalyst and catalytic membrane

[0015] Use a peristaltic pump to pump the suspension in step (2) into the membrane module and load it on the conductive composite membrane; repeat multiple times, and obtain the catalytic membrane after natural drying.

[0016] Further, in the step (1), the thickness of the conductive composite film is 200 - 400 μm;

[0017] Further, in the casting solution of the step (1): the solvent is N,N-dimethylformamide (DMF), the mass percentage of PVDF in the total mass of the casting solution is 10 - 15 wt%, the mass percentage of nano-carbon fiber in the total mass of the casting solution is 1 - 3 wt%, and the mass percentage of polyvinylpyrrolidone (PVP) in the mass of PVDF is 5 - 15 wt%.

[0018] Further, in the step (2), the preparation of ACF Powder: the activated carbon felt (ACF) is ultrasonically treated in acetone, ethanol, and deionized water for 10 - 15 min in sequence and then vacuum dried; secondly, the ACF is soaked in a dilute alkali solution, such as 0.5 - 1 M NaOH or KOH solution, stirred for 2 - 4 hours, rinsed to neutrality, and vacuum dried; finally, the alkali-treated ACF is ground and sieved through a 100 - 200 mesh sieve to collect uniform particles. The temperature of vacuum drying is 60 - 80 °C and the time is 6 - 12 h.

[0019] Further, in the step (2), the mass of ACF Powder is 1 - 20 times the mass of S in the sulfide-containing wastewater 2- of.

[0020] Further, in the step (2), Zn 2+ and Ni 2+ are a mixed solution prepared from Zn(NO3)2·6H2O, Ni(NO3)2·6H2O and deionized water, the molar ratio of Zn to Ni is 1:5 - 1:1, and the amount of substance of S in the sulfide-containing wastewater 2- is 10 - 20 times the sum of the amounts of substance of Zn and Ni.

[0021] Further, in the step (2), the conditions for aeration are 1.8 - 3.0 L min -1 .

[0022] Further, through the synergistic effect of membrane separation coupling adsorption - catalytic oxidation, sulfide ions in the sulfide-containing wastewater are efficiently removed, and the products are recycled to realize the resource utilization of sulfides.

[0023] Further, the catalytic membrane in the step (3) is used to activate persulfate (PMS) to oxidize organic pollutants.

[0024] Further, the catalytic membrane in the step (3) can degrade more than 85% of tetracycline under the action of external visible light and PMS, and has good photocatalytic activity, PMS activation and pollutant removal effects.

[0025] Advantages of the present invention: The present invention provides an innovative method for efficiently removing sulfides from wastewater and realizing resource utilization, with the following remarkable advantages: Through the synergistic effect of membrane separation coupled with adsorption-catalytic oxidation, not only the efficient treatment of sulfur-containing wastewater and the recovery of sulfur resources are achieved, but also the odor and poisoning risks caused by the generation of hydrogen sulfide (H2S) are synchronously solved. In particular, this method innovatively converts sulfide ions (S 2- ) in wastewater into ZnS-NiS-ACF Powder catalyst. The introduction of ACF Powder increases the specific surface area of the catalyst and the number of active sites. Using PVDF as the binder and carbon nanofibers as the conductive reinforcing phase, a catalytic membrane supported on carbon fiber cloth is successfully prepared, which can efficiently activate persulfate (PMS) to remove refractory organic compounds. The present invention realizes the integration of "pollutant removal-resource recovery-depth treatment", and has significant environmental, economic and social benefits. It can be widely applied to the treatment of industrial wastewater and urban black and odorous water bodies, and has important popularization and application value. Brief Description of the Drawings

[0026] Figure 1 It is a comparison chart of the effects of the first and second operation schemes of the conductive composite membrane coupling system on removing sulfide ions.

[0027] Figure 2 It is a degradation effect diagram of 20 mg / L tetracycline by the ZnS-NiS-ACF Powder catalytic membrane coupled with photocatalysis under the condition of PMS.

[0028] Figure 3 It is a comparison chart of the degradation effects of 20 mg / L tetracycline by the ZnS-NiS-ACF Powder catalytic membrane with and without PMS.

[0029] Figure 4 It is a comparison chart of the degradation effects of 20 mg / L tetracycline by activating PMS with and without light by the ZnS-NiS-ACF Powder catalytic membrane. Detailed Embodiments

[0030] The following describes the detailed embodiments of the present invention in detail in combination with the technical solutions and drawings.

[0031] Example 1: Construction of the conductive composite membrane coupling system and preparation of the catalytic membrane

[0032] Step 1. Construction of the conductive composite membrane coupling system

[0033] (1) Preparation of ACF Powder: Cut a piece of 3×6 cm 2The ACF was ultrasonically treated in acetone, ethanol, and deionized water for 10 min in sequence, placed in a vacuum drying oven, and dried at 60 °C for 8 h; the pretreated ACF was soaked in 1 M NaOH solution, stirred for 4 h, rinsed until neutral, and dried at 60 °C for 8 h; finally, the alkali-treated ACF was ground, sieved through a 200-mesh sieve, and uniform particles were collected to obtain ACF Powder for standby.

[0034] (2) Preparation of the mixed solution: 0.03 g of Zn(NO3)2·6H2O (0.10 mmol) and 0.01 g of Ni(NO3)2·6H2O (0.10 mmol) were added to 0.5 mL of deionized water, and ultrasonic stirring was carried out to obtain a mixed solution for standby.

[0035] (3) In the first scheme, a cylindrical glass reactor with a volume of 250 mL was selected. With S 2- at a concentration of 360 mg L -1 (2.25 mmol, 72 mg) of sodium sulfide (Na2S·9H2O) solution as the pollutant solution to be treated, 200 mL was taken and poured into the reactor. 0.2 g of ACF Powder was slowly added to the reactor, and stirred for 1 h to reach the adsorption / desorption equilibrium. Subsequently, 0.5 ml of the mixed solution (a total of 0.20 mmol of metal ions) was added dropwise, and the aeration head was inserted into the object to be treated, and the aeration rate was 1.8 L min -1 , and the reaction was carried out at room temperature for 1 h. Samples were taken every 15 min after the reaction started, and the concentration of S 2- in the solution was measured by methylene blue spectrophotometry, and the concentration change and removal efficiency of S 2- in the system were calculated.

[0036] In the second scheme, first, 0.2 g of ACF Powder was added to 10 ml of deionized water containing 0.5 ml of the mixed solution, and stirred for 30 min for adsorption to reach equilibrium. Then the object to be treated was added, and finally, the aeration pump was turned on for the reaction, and the aeration rate was 1.8 L min -1 , and the reaction was carried out at room temperature for 1 h. The construction methods, sampling, and testing methods of the remaining systems were the same as those of the first scheme.

[0037] After treating the sulfide-containing wastewater by one of the two schemes, a ZnS-NiS-ACF Powder catalyst was in-situ generated on the ACF Powder, forming a suspension.

[0038] Step two: Preparation of the catalytic membrane

[0039] The casting solution was prepared as shown in Table 1, magnetically stirred for 4 h to mix it evenly, and after vacuum degassing for 30 min, a 300-μm membrane was scraped on the carbon fiber cloth using a membrane preparation device, and then the membrane was placed in deionized water for 1 night to complete the phase inversion.

[0040] Use a peristaltic pump to pump the suspension in Step 1 into the membrane module, repeat the cleaning three times, and obtain the catalytic membrane.

[0041] Such as Figure 1 It is a comparison chart of the effects of removing sulfide ions by the first and second operation schemes of the conductive composite membrane coupling system. As can be seen from the figure, both methods can efficiently remove sulfides, and the removal efficiency is greater than 99%. The first method is suitable for the treatment of wastewater with a high concentration of sulfides, can quickly adsorb sulfides and initiate the oxidation reaction; the second method optimizes the catalytic oxidation ability of the reaction system by pre-adsorbing metal ions. The two methods can be flexibly selected according to the actual wastewater characteristics and treatment requirements, and have broad application prospects.

[0042] Table 1 Composition of the casting solution

[0043] PVDF Carbon nanofiber DMF PVP 1.5g 0.25g 8.1g 0.15g

[0044] Example 2: Degradation of tetracycline by the catalytic membrane under visible light and in the presence of PMS

[0045] Use a cuboid quartz container (4×5×22 cm 3 ) as the reactor. Add 300 mL of 20 mg / L tetracycline into the reactor, immerse the catalytic membrane prepared in Example 1 with a total area of 2.5 cm×5.75 cm×2 in the solution, and stir at a speed of 500 rpm at the bottom. Shade and adsorb for the first 30 min, and use a peristaltic pump to pump the water discharged after the reaction back to the membrane module to enhance mass transfer. Add 1 mM PMS, turn on the external light source (20 W iodine tungsten lamp, the light source is 4 cm away from the electrode membrane, and the light-receiving membrane area is 2.5 cm×5.75 cm), and the reaction starts. React at room temperature for 90 min. Take water samples every about 10 min, measure the absorbance at a wavelength of 357 nm using a spectrophotometer, and calculate the tetracycline concentration and removal rate.

[0046] Such as Figure 2 As shown, the catalytic membrane can remove about 6.5% of tetracycline through adsorption. After reacting for 1.5 h, the degradation rate can reach 87.0%, indicating that the catalytic membrane has photocatalytic activity and PMS activation ability, and can effectively remove the refractory pollutant tetracycline.

[0047] Example 3: Degradation of tetracycline by the catalytic membrane with and without PMS

[0048] The sampling and testing methods are the same as those in Example 2, except that in the construction of the catalytic membrane coupling system: in this example, a cuboid quartz container (4×5×22 cm 3) It is a reactor. Add 300 mL of 20 mg / L tetracycline into the reactor, immerse the catalytic membrane prepared in Example 1 with a total area of 2.5 cm × 5.75 cm × 2 in the solution, and stir at a speed of 500 rpm at the bottom. Adsorb under light shielding for the first 30 min, and use a peristaltic pump to pump the water after the reaction back to the membrane module to enhance mass transfer. Add 1 mM PMS to start the reaction. React at 35 °C for 90 min. The control group has no PMS.

[0049] As Figure 3 shown, it is a comparison chart of the tetracycline removal effects of the system under the conditions of no PMS and with PMS for 2 h. It can be seen from the figure that after 2 h of reaction, the removal efficiencies of the catalytic membrane coupling system without PMS and with PMS for tetracycline are 13.3% and 78.8% respectively. It shows that the catalytic membrane coupling system has an activation effect on PMS.

[0050] Example 4: Degradation of tetracycline by catalytic membrane-activated PMS under light and dark conditions

[0051] The construction method of the catalytic membrane coupling system is the same as that in Example 2, and the sampling and testing methods are the same as those in Example 2. The control group has no light.

[0052] As Figure 4 shown, it is a comparison chart of the tetracycline removal effects of the system under light and dark conditions for 2 h. It can be seen from the figure that after 2 h of reaction, the removal efficiencies of the catalytic membrane coupling system in the dark and under light for tetracycline are 56.0% and 87.0% respectively. It shows that the catalytic membrane coupling system can activate part of PMS, and coupling photocatalysis can further improve the activation rate of PMS in the system and the removal ability of pollutants.

Claims

1. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system, characterized in that The steps are as follows: (1) Prepare a conductive composite membrane: Prepare a casting solution with polyvinylidene fluoride as the binder, carbon nanofibers as the conductive reinforcing phase, and polyvinylpyrrolidone as the pore-forming agent, and use the phase inversion method to prepare a conductive composite membrane on a carbon fiber cloth substrate; Fix the conductive composite membrane on the membrane module for standby; (2) Construct a conductive composite membrane coupling system Treat the sulfide-containing wastewater using one of the following schemes to in-situ generate a ZnS-NiS-ACF Powder catalyst on activated carbon felt powder (ACF Powder) to form a suspension; the specific scheme is as follows: In the first solution, ACF Powder is added to the sulfide-containing wastewater and stirred until the adsorption / desorption equilibrium is reached to effectively adsorb the sulfide ion S in the sulfide-containing wastewater 2- ; Subsequently, a solution containing metal ions Zn 2+ and Ni 2+ is added, and the aeration head is inserted into the sulfide-containing wastewater. Dissolved oxygen and mechanical external force are provided through aeration to promote the oxidation process in the reaction system; The second solution is to first add ACF Powder to a solution containing metal ions Zn 2+ and Ni 2+ for adsorption until equilibrium is reached, then add sulfide-containing wastewater, and finally turn on the aeration pump for reaction; (3) Prepare the ZnS-NiS-ACF Powder catalyst and the catalytic membrane Use a peristaltic pump to pump the suspension in step (2) into the membrane module and load it on the conductive composite membrane; repeat multiple times, and obtain the catalytic membrane after natural drying.

2. The sulfide pollution control and resource utilization method based on a conductive composite film coupling system according to claim 1, characterized in that In step (1), the thickness of the conductive composite membrane is 200 - 400 μm.

3. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that In the casting solution of step (1): the solvent is N,N-dimethylformamide, the mass percentage of polyvinylidene fluoride in the total mass of the casting solution is 10 - 15 wt%, the mass percentage of carbon nanofibers in the total mass of the casting solution is 1 - 3 wt%, and the mass percentage of polyvinylpyrrolidone in polyvinylidene fluoride is 5 - 15 wt%.

4. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that In step (2), for the preparation of ACF Powder: ultrasonically treat activated carbon felt (ACF) in acetone, ethanol, and deionized water for 10 - 15 min each, and then vacuum dry; secondly, soak the ACF in a dilute alkali solution, such as 0.5 - 1 M NaOH or KOH solution, stir for 2 - 4 hours, rinse until neutral, and vacuum dry; finally, grind the alkali-treated ACF, sieve it through a 100 - 200 mesh sieve, and collect the uniform particles; the temperature of vacuum drying is 60 - 80 °C, and the time is 6 - 12 h.

5. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that, In the step (2), the mass of the ACF Powder is 1 to 20 times the mass of S 2- in the sulfide-containing wastewater.

6. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that, In the step (2), Zn 2+ and Ni 2+ are a mixed solution prepared from Zn(NO3)2·6H2O, Ni(NO3)2·6H2O and deionized water. The molar ratio of Zn to Ni is 1:5 - 1:1, and the amount of substance of S 2- in the sulfide-containing wastewater is 10 - 20 times the sum of the amounts of substance of Zn and Ni.

7. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that, In the step (2), the conditions for aeration are 1.8 - 3.0 L min -1 .

8. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that, Through the synergistic effect of membrane separation, coupled with adsorption-catalytic oxidation, efficiently remove sulfide ions in the sulfide-containing wastewater, and recycle the products to achieve the resource utilization of sulfides.

9. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that The catalytic membrane in step (3) is used to activate persulfate (PMS) to oxidize organic pollutants.

10. A method for controlling sulfide pollution and resource treatment based on a conductive composite film coupling system according to claim 1, characterized in that, The catalytic membrane in step (3) can degrade more than 85% of tetracycline under the action of external visible light and PMS, and has good photocatalytic activity, PMS activation, and pollutant removal effects.

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