A method for recovering p-aminophenol from wastewater

Abstract

The application discloses a method for recycling p-aminophenol in wastewater, and belongs to the technical field of wastewater treatment. First, p-nitrophenol wastewater is adsorbed by carbon fibers, and then is treated by a microbial fuel cell. Protons and electrons are generated in an anode liquid of an anode modified graphite felt, the electrons are transmitted to a cathode through a wire, the protons are simultaneously transferred to the cathode chamber through a membrane, and the organic matters adhered to the carbon fibers are degraded after being combined in the cathode chamber. Finally, the carbon fibers and the organic matters are separated, and then are subjected to vacuum distillation in deionized water, concentrated evaporation, and p-aminophenol is obtained. The microbial fuel cell has good electricity generation performance, stable performance, high anode COD removal rate, and efficient use of electric charges in the cathode, so that the removal rate of p-nitrophenol is high, and the generation of p-aminophenol is promoted.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and specifically relates to a method for recovering p-aminophenol from wastewater. Background Technology

[0002] p-Aminophenol, a fine chemical intermediate, is mainly used in the pharmaceutical, rubber, dye, photography, and petroleum industries. Through acetylation, p-aminophenol can produce the antipyretic and analgesic drug paracetamol, and it can also be used as a polymerization inhibitor for plastic monomers, a rubber antioxidant and vulcanizing agent, an intermediate for azo fur dyes, and a developing agent. Currently, nearly 90% of domestic p-aminophenol consumption is for the synthesis of paracetamol. Paracetamol is the world's most important antipyretic and analgesic drug, accounting for 45% of the entire antipyretic and analgesic drug market; therefore, the recycling of p-aminophenol can bring significant economic benefits. However, the production of p-aminophenol generates a large amount of wastewater. p-Nitrophenol is one of the 129 primary pollutants in the United States and is also one of the sources of p-aminophenol production. Traditional methods for degrading p-nitrophenol to obtain p-aminophenol by physical and chemical treatment of phenol-containing wastewater can easily cause secondary pollution. Biological treatment has problems such as long reaction cycles and easy poisoning. This paper seeks a new, efficient, and low-cost wastewater treatment method that can degrade p-nitrophenol to obtain p-aminophenol and recover it.

[0003] Microbial fuel cells (MFCs), with their combined power generation and pollutant removal capabilities, are attracting increasing attention from researchers both domestically and internationally. Developing new electrode materials and modification methods is an effective means to improve the power density and pollutant degradation efficiency of MFCs. Commonly used anode materials mainly include carbon-based materials, stainless steel materials, and nickel mesh. They generally possess high conductivity and chemical stability, but due to their smooth surfaces and low porosity, they often exhibit drawbacks such as low microbial loading, poor electrocatalytic biofilm activity, and small specific capacitance.

[0004] As reported in the literature "Basic Research on Phenol Treatment by Microbial Fuel Cell Technology", MFC, as a novel electrochemical technology, can not only effectively degrade phenol pollutants, but also generate electricity without external energy intake. The degradation process is pollution-free and the operating conditions are mild and simple, so it has gradually become a research hotspot in the field of water treatment and has great development potential. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recovering p-aminophenol from wastewater, so as to achieve the following objectives:

[0006] (1) A method for recovering p-aminophenol from wastewater is provided. The microbial fuel cell has good power generation performance, the COD removal rate in the anode is effectively improved, and the p-nitrophenol removal rate in the cathode is relatively high.

[0007] (2) A method for recovering p-aminophenol from wastewater is provided, which is pollution-free and efficient in the process of degrading and recovering p-aminophenol from p-nitrophenol.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A method for recovering p-aminophenol from wastewater includes the following steps:

[0010] Step (1): Add sodium hydroxide solution to p-nitrophenol wastewater, adjust the pH value to 3.5-4.5, filter, obtain filtrate, inject the filtrate into an adsorption column containing activated carbon fiber at room temperature, with a flow rate of 0.2-0.3 L / h, to obtain carbon fiber containing organic matter;

[0011] Step (2), construction of microbial fuel cell, anode inoculum, wastewater treatment; construction of microbial fuel cell includes: modified graphite felt;

[0012] The anode inoculum and anolyte are placed in the anode chamber, and the anolyte is continuously supplied to the anode chamber through the continuous water supply system; the catholyte and carbon fiber containing organic matter are mixed and placed in the cathode chamber, and the catholyte is continuously supplied to the cathode chamber through the continuous water supply system, and kept at room temperature for 10-20 days;

[0013] Step (3): Take out the carbon fiber containing organic matter after microbial fuel cell treatment, centrifuge, filter and evaporate to obtain crude p-aminophenol, then add the crude p-aminophenol to deionized water to obtain a mixed solution, and then distill the mixed solution under reduced pressure to concentrate and evaporate to obtain p-aminophenol.

[0014] The method for preparing the anode inoculum in step (2) includes the following steps:

[0015] Sludge containing anaerobic bacteria from the wastewater treatment system of Yanshan Petrochemical was used as unacclimated anode inoculum. The anaerobic bacteria were unacclimated strains. The acclimation solution consisted of glucose, potassium dihydrogen phosphate, MgSO4·7H2O, sodium carboxylate, and calcium chloride. Nitrogen gas was introduced into the acclimation solution for 30-60 minutes. The solution was then stirred with the unacclimated anode inoculum under anaerobic conditions at a speed of 15 RPM and acclimated for 1-2 days to obtain the anode inoculum.

[0016] In step (2), the mass ratio of glucose, potassium dihydrogen phosphate, MgSO4·7H2O, sodium carboxylate, and calcium chloride is 3-5:1:2-3:1:1-2; the volume ratio of the acclimation solution to the unacclimated anode inoculum is 3-5:1.

[0017] In step (2), the concentration of the anode inoculum in the anode chamber is 0.5-1 g / L.

[0018] The concentration of p-nitrophenol wastewater in the anolyte in step (2) is 380-420 mg / L.

[0019] The mixing steps of the cathode liquid and the carbon fiber containing organic matter in step (2) are as follows:

[0020] Mix the carbon fiber containing organic matter with the catholyte, and purge with nitrogen gas at room temperature for 30-60 minutes. The ratio of organic carbon fiber to deionized water is 4-8 g: 1 L, and the catholyte is preferably deionized water.

[0021] The construction of the microbial fuel cell in step (2) includes an anode chamber, an ion exchange membrane, a cathode chamber membrane, and a continuous water inlet system; the anode chamber is provided with anolyte and anode inoculum, and the cathode chamber is provided with catholyte; the anode chamber and the cathode chamber are connected by wires; the anode electrode is modified graphite felt, and the cathode electrode is graphite felt.

[0022] The method for preparing modified graphite felt in step (2) includes the following steps:

[0023] S1. Cut the graphite felt into rectangular pieces of 4cm×1cm with a thickness of 1mm. Sonicate them in 2mol / L hydrochloric acid solution, acetone and deionized water for 20-40min respectively, and dry them to obtain pretreated graphite felt.

[0024] S2. First, mix 50wt% phytic acid solution, aniline, and deionized water, then pour in 0.3g / L ammonium persulfate solution and mix. Keep the temperature at 1-3℃, separate, purify for 3-5 days, and vacuum dry to obtain polyaniline hydrogel.

[0025] S3. Dissolve the polyaniline hydrogel in the carbon nanotube suspension and mix. Sonicate for 5-10 minutes. Then add potassium persulfate and tetramethylethylenediamine. Stir in an ice bath for 4-8 minutes to obtain a mixed solution. Immerse the graphite felt in the mixed solution and keep it at 35-40℃ for 20-40 minutes. Filter, remove the filter cake, scrape off the excess polyaniline hydrogel on the surface of the filter cake, and dry to obtain the modified graphite felt.

[0026] The ratio of 50wt% phytic acid solution, aniline, deionized water and ammonium persulfate solution in S2 is 1-1.4mL:0.46-0.58mL:2mL:0.28-0.36g.

[0027] The ratio of polyaniline hydrogel, carbon nanotube suspension, potassium persulfate and tetramethylethylenediamine in S3 is 1 mL: 0.18-0.26 mL: 0.001 g: 0.001 g.

[0028] The method for preparing the carbon nanotube suspension in S3 includes the following steps:

[0029] The method for preparing the carbon nanotube suspension in S3 includes the following steps: adding single-walled carbon nanotubes to a mixed solution of 98wt% H2SO4 and 68wt% HNO3, sonicating at 45-60℃ for 5-8 hours, diluting in 500mL of deionized water, filtering with a 0.20-0.25μm polytetrafluoroethylene membrane, adjusting the pH to 6.5-7.5, centrifuging, filtering, and washing to obtain carbon nanotubes, and then dispersing the obtained carbon nanotubes in deionized water by sonication to obtain a carbon nanotube suspension.

[0030] The ratio of the mixed solution to single-walled carbon nanotubes is 0.6 mL: 1-1.4 g, the volume ratio of 98 wt% H2SO4 to 68 wt% HNO3 is 3:1, and the concentration of the carbon nanotube suspension is 1 mg / mL.

[0031] In step (3), the crude p-aminophenol is 30-40% of the mass of deionized water.

[0032] The beneficial effects of this invention are:

[0033] (1) The modified graphite felt constructed in this invention reacts with phytic acid through the nitrogen groups on protonated polyaniline, and the phytic acid molecules and aniline chains cross-link to form a three-dimensional hydrogel network structure, which exhibits good conductivity. Phytic acid itself has excellent biological activity and can accommodate more microorganisms. When mixed with carbon nanotubes, it increases the specific surface area. The pore structure of the graphite felt can provide better support and attachment points for the hydrogel, so that the hydrogel forms a stable bond on the skeleton. The microbial fuel cell has stable performance and good power generation performance.

[0034] (2) The method for recovering p-aminophenol from wastewater in this invention uses microbial fuel cell treatment to achieve a high COD removal rate at the anode and efficient use of charge at the cathode to achieve a high removal rate of p-nitrophenol and generate p-aminophenol. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing a carbon nanotube suspension, comprising the following steps:

[0038] 10 g of single-walled carbon nanotubes were added to a mixed solution of 4.5 mL of 98 wt% H₂SO₄ and 1.5 mL of 68 wt% HNO₃, and sonicated at 45 °C for 5 h. The solution was then diluted in 500 mL of deionized water, filtered through a 0.20 μm polytetrafluoroethylene membrane, and the pH was adjusted to 6.5. The solution was then centrifuged, filtered, and washed to obtain a carbon nanotube suspension. The preparation method of the carbon nanotube suspension in S3 includes the following steps: adding single-walled carbon nanotubes to a mixed solution of 98 wt% H₂SO₄ and 68 wt% HNO₃, sonicating at 45 °C for 5 h, diluting in 500 mL of deionized water, filtering through a 0.20 μm polytetrafluoroethylene membrane, adjusting the pH to 6.5, centrifuging, filtering, and washing to obtain carbon nanotubes, and then dispersing the obtained carbon nanotubes in deionized water by sonication to obtain a carbon nanotube suspension.

[0039] The concentration of the carbon nanotube suspension was 1 mg / mL.

[0040] Example 2

[0041] A method for preparing a carbon nanotube suspension, comprising the following steps:

[0042] 14 g of single-walled carbon nanotubes were added to a mixed solution of 4.5 mL of 98 wt% H2SO4 and 1.5 mL of 68 wt% HNO3. The mixture was sonicated at 60 °C for 8 h, then diluted in 500 mL of deionized water. The solution was filtered through a 0.25 μm polytetrafluoroethylene membrane, and the pH was adjusted to 7.5. The solution was then centrifuged, filtered, washed, and then sonicated to disperse the carbon nanotubes in deionized water to obtain a carbon nanotube suspension.

[0043] The concentration of the carbon nanotube suspension was 1 mg / mL.

[0044] Example 3

[0045] A method for preparing modified graphite felt, comprising the following steps:

[0046] S1. Cut the graphite felt into rectangular pieces of 4cm×1cm with a thickness of 1mm. Sonicate them in 2mol / L hydrochloric acid solution, acetone and deionized water for 20min respectively, and dry them to obtain pretreated graphite felt.

[0047] S2. First, mix 2 mL of 50 wt% phytic acid solution, 0.92 mL of aniline, and 4 mL of deionized water, then pour in 1.12 mL of 0.3 g / L ammonium persulfate solution and mix. Keep the temperature at 1℃, separate, purify for 3 days, and vacuum dry to obtain polyaniline hydrogel.

[0048] S3. Dissolve 2 mL of polyaniline hydrogel in 0.36 mL of carbon nanotube suspension from Example 1 and mix. Sonicate for 5 min. Then add 0.002 g of potassium persulfate and 0.002 g of tetramethylethylenediamine. Stir in an ice bath for 4 min to obtain a mixed solution. Immerse the graphite felt in the mixed solution and keep it at 35°C for 20 min. Filter, remove the filter cake, scrape off the excess polyaniline hydrogel on the surface of the filter cake, and dry to obtain modified graphite felt.

[0049] Example 4

[0050] A method for preparing modified graphite felt, comprising the following steps:

[0051] S1. Cut the graphite felt into rectangular pieces of 4cm×1cm with a thickness of 1mm. Sonicate them in 2mol / L hydrochloric acid solution, acetone and deionized water for 40min respectively, and dry them to obtain pretreated graphite felt.

[0052] S2. First, mix 2.8 mL of 50 wt% phytic acid solution, 1.16 mL of aniline, and 4 mL of deionized water, then pour in 1.44 mL of 0.3 g / L ammonium persulfate solution and mix. Keep the temperature at 3℃, separate, purify for 5 days, and vacuum dry to obtain polyaniline hydrogel.

[0053] S3. Dissolve 2 mL of polyaniline hydrogel in 0.52 mL of carbon nanotube suspension from Example 2, mix, sonicate for 10 min, then add 0.002 g of potassium persulfate and 0.002 g of tetramethylethylenediamine, stir in an ice bath for 8 min to obtain a mixed solution, then immerse the graphite felt in the mixed solution, keep at 40°C for 40 min, filter, remove the filter cake, scrape off the excess polyaniline hydrogel on the surface of the filter cake, dry, and obtain the modified graphite felt.

[0054] Example 5

[0055] A method for preparing modified graphite felt, comprising the following steps:

[0056] S1. Cut the graphite felt into rectangular pieces of 4cm×1cm with a thickness of 1mm. Sonicate them in 2mol / L hydrochloric acid solution, acetone and deionized water for 30min respectively, and dry them to obtain pretreated graphite felt.

[0057] S2. First, mix 2.4 mL of 50 wt% phytic acid solution, 1 mL of aniline, and 4 mL of deionized water, then pour in 1.2 mL of 0.3 g / L ammonium persulfate solution and mix. Keep the temperature at 2℃, separate, purify for 4 days, and vacuum dry to obtain polyaniline hydrogel.

[0058] S3. Dissolve 2 mL of polyaniline hydrogel in 0.4 mL of carbon nanotube suspension from Example 2 and mix. Sonicate for 8 min. Then add 0.002 g of potassium persulfate and 0.002 g of tetramethylethylenediamine. Stir in an ice bath for 6 min to obtain a mixed solution. Then immerse the graphite felt in the mixed solution and keep it at 38°C for 30 min. Filter, remove the filter cake, scrape off the excess polyaniline hydrogel on the surface of the filter cake, and dry to obtain modified graphite felt.

[0059] Example 6

[0060] A method for recovering p-aminophenol from wastewater includes the following steps:

[0061] Step (1): Add sodium hydroxide solution to p-nitrophenol wastewater, adjust the pH value to 3.5, filter, and obtain filtrate. Inject the filtrate into an adsorption column containing activated carbon fiber at room temperature with a flow rate of 0.2 L / h to obtain carbon fiber containing organic matter.

[0062] Step (2), construction of microbial fuel cell, anode inoculum, wastewater treatment; construction of microbial fuel cell includes: modified graphite felt of Example 3;

[0063] The anode inoculum and anolyte are placed in the anode chamber, and the anolyte is continuously supplied to the anode chamber through a continuous water supply system; deionized water and carbon fiber containing organic matter are mixed and placed in the cathode chamber, and the catholyte is continuously supplied to the cathode chamber through the same continuous water supply system, and kept at room temperature for 10 days.

[0064] Step (3): Take out the carbon fiber containing organic matter after microbial fuel cell treatment, centrifuge, filter and evaporate to obtain crude p-aminophenol, then add 6g of crude p-aminophenol to 20g of deionized water to obtain a mixed solution, and distill the mixed solution under reduced pressure to concentrate and evaporate to obtain p-aminophenol.

[0065] The method for preparing the anode inoculum in step (2) includes the following steps:

[0066] Sludge containing anaerobic bacteria from the wastewater treatment system of Yanshan Petrochemical was used as unacclimated anode inoculum. The anaerobic bacteria were unacclimated strains. The acclimation solution consisted of 1.5g glucose, 0.5g potassium dihydrogen phosphate, 1g MgSO4·7H2O, 0.5g sodium carboxylate, and 0.5g calcium chloride. Nitrogen gas was introduced into the acclimation solution for 30 minutes. The solution was then stirred with the unacclimated anode inoculum under anaerobic conditions at a speed of 15 RPM and acclimated for 1 day to obtain the anode inoculum.

[0067] The volume ratio of the acclimation solution to the unacclimated anode inoculum is 3:1.

[0068] In step (2), the concentration of the anode inoculum in the anode chamber is 0.5 g / L.

[0069] In step (2), the anolyte is p-nitrophenol wastewater with a concentration of 380 mg / L.

[0070] The mixing steps of deionized water and carbon fiber containing organic matter in step (2) are as follows:

[0071] Mix 2g of carbon fiber containing organic matter with 500mL of deionized water, and purge with nitrogen gas at 25°C for 30min.

[0072] The construction of the microbial fuel cell in step (2) includes an anode chamber, an ion exchange membrane, a cathode chamber membrane, and a continuous water supply system; the anode chamber is provided with anolyte and anode inoculum, and the cathode chamber is provided with deionized water; the anode chamber and the cathode chamber are connected by wires; the anode electrode is the modified graphite felt of Example 3, and the cathode electrode is graphite felt.

[0073] Example 7

[0074] A method for recovering p-aminophenol from wastewater includes the following steps:

[0075] Step (1): Add sodium hydroxide solution to p-nitrophenol wastewater, adjust the pH value to 4.5, filter, and obtain filtrate. Inject the filtrate into an adsorption column containing activated carbon fiber at room temperature with a flow rate of 0.3 L / h to obtain carbon fiber containing organic matter.

[0076] Step (2), construction of microbial fuel cell, anode inoculum, wastewater treatment; construction of microbial fuel cell includes: modified graphite felt of Example 4;

[0077] The obtained bacterial strain and anolyte were placed in the anode chamber, and the anolyte was continuously supplied to the anode chamber through a continuous water supply system; deionized water and carbon fiber containing organic matter were mixed and placed in the cathode chamber, and the catholyte was continuously supplied to the cathode chamber through the same continuous water supply system, and kept at room temperature for 20 days.

[0078] Step (3): Take out the carbon fiber containing organic matter after microbial fuel cell treatment, centrifuge, filter and evaporate to obtain crude p-aminophenol, then add 8g of crude p-aminophenol to 20g of deionized water to obtain a mixed solution, and distill the mixed solution under reduced pressure to concentrate and evaporate to obtain p-aminophenol.

[0079] The method for preparing the anode inoculum in step (2) includes the following steps:

[0080] Sludge containing anaerobic bacteria from the wastewater treatment system of Yanshan Petrochemical was used as unacclimated anode inoculum. The anaerobic bacteria were unacclimated strains. The acclimation solution consisted of 2.5g glucose, 0.5g potassium dihydrogen phosphate, 1.5g MgSO4·7H2O, 0.5g sodium carboxylate, and 1g calcium chloride. Nitrogen gas was introduced into the acclimation solution for 60 minutes. The solution was then stirred with the unacclimated anode inoculum under anaerobic conditions at a speed of 15 RPM and acclimated for 2 days to obtain the anode inoculum.

[0081] The volume ratio of the acclimation solution to the unacclimated anode inoculum is 5:1.

[0082] In step (2), the concentration of the anode inoculum in the anode chamber is 1 g / L.

[0083] In step (2), the anolyte is p-nitrophenol wastewater with a concentration of 420 mg / L.

[0084] The mixing steps of deionized water and carbon fiber containing organic matter in step (2) are as follows:

[0085] Mix 4g of carbon fiber containing organic matter with 500mL of deionized water, and purge with nitrogen gas at 25°C for 60min.

[0086] The construction of the microbial fuel cell in step (2) includes an anode chamber, an ion exchange membrane, a cathode chamber membrane, and a continuous water supply system; the anode chamber is provided with anolyte and positive inoculum, and the cathode chamber is provided with deionized water; the anode chamber and the cathode chamber are connected by wires; the anode electrode is the modified graphite felt of Example 4, and the cathode electrode is graphite felt.

[0087] Example 8

[0088] A method for recovering p-aminophenol from wastewater includes the following steps:

[0089] Step (1): Add sodium hydroxide solution to p-nitrophenol wastewater, adjust the pH value to 4, filter, and obtain filtrate. Inject the filtrate into an adsorption column containing activated carbon fiber at room temperature with a flow rate of 0.25 L / h to obtain carbon fiber containing organic matter.

[0090] Step (2), construction of microbial fuel cell, anode inoculum, wastewater treatment; construction of microbial fuel cell includes: modified graphite felt of Example 5;

[0091] The anode inoculum and anolyte are placed in the anode chamber, and the anolyte is continuously supplied to the anode chamber through the continuous water supply system; the catholyte and carbon fiber containing organic matter are mixed and placed in the cathode chamber, and the catholyte is continuously supplied to the cathode chamber through the continuous water supply system, and kept at room temperature for 15 days.

[0092] Step (3): Take out the carbon fiber containing organic matter after microbial fuel cell treatment, centrifuge, filter and evaporate to obtain crude p-aminophenol, then add 6.8g of crude p-aminophenol to 20g of deionized water to obtain a mixed solution, and then distill the mixed solution under reduced pressure to concentrate and evaporate to obtain p-aminophenol.

[0093] The method for preparing the anode inoculum in step (2) includes the following steps:

[0094] Sludge containing anaerobic bacteria from the wastewater treatment system of Yanshan Petrochemical was used as unacclimated anode inoculum. The anaerobic bacteria were unacclimated strains. The acclimation solution consisted of 2g glucose, 0.5g potassium dihydrogen phosphate, 1.2g MgSO4·7H2O, 0.5g sodium carboxylate, and 0.8g calcium chloride. Nitrogen gas was introduced into the acclimation solution for 40 minutes. The solution was then stirred with the unacclimated anode inoculum under anaerobic conditions at a speed of 15 RPM and acclimated for 1.5 days to obtain the anode inoculum.

[0095] The volume ratio of the acclimation solution to the unacclimated anode inoculum is 4:1.

[0096] In step (2), the concentration of the anode inoculum in the anode chamber is 0.8 g / L.

[0097] In step (2), the anolyte is p-nitrophenol wastewater with a concentration of 400 mg / L.

[0098] The mixing steps of deionized water and carbon fiber containing organic matter in step (2) are as follows:

[0099] Mix 3g of carbon fiber containing organic matter with 500mL of deionized water, and purge with nitrogen gas at 25°C for 40min.

[0100] The construction of the microbial fuel cell in step (2) includes an anode chamber, an ion exchange membrane, a cathode chamber membrane, and a continuous water supply system; the anode chamber is provided with anolyte and anode inoculum, and the cathode chamber is provided with deionized water; the anode chamber and the cathode chamber are connected by wires; the anode electrode is the modified graphite felt of Example 5, and the cathode electrode is graphite felt.

[0101] Comparative Example 1

[0102] Compared with Example 7, the modified graphite felt in Example 7 was replaced with graphite felt, and the other raw materials and preparation process were the same as in Example 7.

[0103] Comparative Example 2

[0104] Compared with Example 7, the carbon fiber containing organic matter and the step of mixing carbon fiber containing organic matter and deionized water in Example 7 were removed, while the remaining raw materials and preparation process were the same as in Example 7.

[0105] Performance tests were conducted on Examples 6-8 and Comparative Examples 1-2. COD was determined according to GB11914-89 "Determination of Chemical Oxygen Demand"; voltage was measured using an automatic voltage acquisition device connected to the dual-chamber microbial fuel cell, with output voltage collected every 0.5 hours. Under stable system operation, the effluent from the cathode and anode chambers was collected, filtered using a nanofilter, and the concentrations of p-nitrophenol and p-aminophenol were measured. The cathode coulombic efficiency was calculated as: (Number of electrons accepted per mole of p-nitrophenol) × (Concentration of p-nitrophenol in the cathode feed liquid - Concentration of degradation products in the cathode effluent) × Cathode feed liquid flow rate × 10⁻¹⁰. 3 The current of a microbial fuel cell can be measured using an electrochemical workstation by calculating ÷24÷3600×Faraday constant÷current.

[0106] All tests were conducted on the microbial fuel cell under a hydraulic residence time of 8 hours, as shown in Table 1:

[0107] Table 1

[0108]

[0109]

[0110] As shown in Table 1, the anode COD removal rate remained at 74.2-77.4% in Examples 6-8 and Comparative Example 2, with Comparative Example 2 being 54.8%; the cathode coulombic efficiency for p-aminophenol was 71.8-76.2%, with Comparative Example 1 being 65.4%; and the cathode coulombic efficiency for p-aminophenol was 74.2-78.6%, with Comparative Example 1 being 66.8%.

[0111] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for recovering p-aminophenol from waste water, characterized in that, It comprises the following steps: Step (1), adding sodium hydroxide solution to p-nitrophenol wastewater, adjusting the pH value to 3.5-4.5, filtering, obtaining the filtrate, and injecting the filtrate into an adsorption column containing activated carbon fiber at room temperature, the flow rate being 0.2-0.3 L / h, and obtaining the activated carbon fiber containing organic matter; Step (2), construction of microbial fuel cell, anode inoculum, and wastewater treatment; the construction of the microbial fuel cell comprises: the anode electrode is modified graphite felt, and the cathode electrode is graphite felt; The anode inoculum and anode liquid are placed in the anode chamber, and the anode liquid is continuously supplied to the anode chamber through a continuous water feeding system; the cathode liquid and the activated carbon fiber containing organic matter are mixed and placed in the cathode chamber, and the cathode liquid is continuously supplied to the cathode chamber through the continuous water feeding system, and the room temperature is maintained for 10-20 days; Step (3), taking out the activated carbon fiber containing organic matter treated by the microbial fuel cell, and performing centrifugation, filtration, and evaporation to obtain a crude product of p-aminophenol, then adding the crude product of p-aminophenol into deionized water to obtain a mixed solution, and performing vacuum distillation on the mixed solution to obtain p-aminophenol through concentration and evaporation; The anode liquid in step (2) is p-nitrophenol wastewater with a concentration of 380-420 mg / L. The preparation method of the anode inoculum in step (2) comprises the following steps: The sludge containing anaerobic bacteria in a sewage treatment system is used as the unacclimated anode inoculum, and the anaerobic bacteria are unacclimated strains; the acclimation liquid components include glucose, potassium dihydrogen phosphate, MgSO4·7H2O, sodium carboxylate, and calcium chloride; nitrogen gas is introduced into the acclimation liquid for 30-60 min, and then the unacclimated anode inoculum is stirred at a stirring speed of 15 RPM in an anaerobic state to obtain the anode inoculum after acclimation culture for 1-2 days; The preparation method of the modified graphite felt in step (2) comprises the following steps: S1, cutting the graphite felt into a rectangular sheet with a size of 4 cm×1 cm and a thickness of 1 mm, and ultrasonic treating the graphite felt in 2 mol / L hydrochloric acid solution, acetone, and deionized water for 20-40 min, respectively, and drying to obtain pretreated graphite felt; S2, mixing 50 wt% phytic acid solution, aniline, and deionized water, then pouring into 0.3 g / L ammonium persulfate solution, keeping the temperature at 1-3 ℃, separating, purifying for 3-5 days, and vacuum drying to obtain polyaniline hydrogel; S3, dissolving the polyaniline hydrogel in carbon nanotube suspension, ultrasonic treating for 5-10 min, then adding potassium persulfate and tetramethyl ethylenediamine, stirring in an ice bath for 4-8 min to obtain a mixed solution, then immersing the graphite felt in the mixed solution, keeping the temperature at 35-40 ℃ for 20-40 min, filtering, taking out the filter cake, scraping off the excess polyaniline hydrogel on the surface of the filter cake, and drying to obtain the modified graphite felt.

2. A process for recovering p-aminophenol from waste water as claimed in claim 1 wherein, The mass ratio of glucose, potassium dihydrogen phosphate, MgSO4·7H2O, sodium carboxylate, and calcium chloride in step (2) is 3-5:1:2-3:1:1-2; the volume ratio of the acclimation liquid to the unacclimated anode inoculum is 3-5:

1.

3. The process of claim 1, wherein the process is carried out at a temperature of about 20°C to about 60°C. The concentration of the anode inoculum in the anode chamber in step (2) is 0.5-1 g / L.

4. The process of claim 1, wherein the process is carried out at a temperature of about 20°C to about 60°C. The mixing step of the catholyte and the activated carbon fiber containing organic matter in step (2) is as follows: The activated carbon fiber containing organic matter and the catholyte are mixed, and nitrogen is introduced at room temperature for 30-60 min, the usage ratio of the activated carbon fiber containing organic matter and the catholyte is 4-8 g:1 L, and the catholyte is deionized water.

5. The process of claim 1, wherein the process is carried out at a temperature of about 20°C to about 60°C. The microbial fuel cell in step (2) is constructed and includes an anode chamber, an ion exchange membrane, a cathode chamber membrane and a continuous water feeding system; the anode chamber is provided with an anode liquid and an anode inoculum, and the cathode chamber is provided with a cathode liquid and an activated carbon fiber containing organic matter; the anode chamber and the cathode chamber are connected by wires.

6. The method of recovering p-aminophenol from wastewater of claim 1, wherein, The usage ratio of the polyaniline hydrogel, the carbon nanotube suspension, the potassium persulfate and the tetramethylethylenediamine in S3 is 1 mL:0.18-0.26 mL:0.001 g:0.001 g; the preparation method of the carbon nanotube suspension in S3 includes the following steps: single-walled carbon nanotubes are added into a mixed solution of 98 wt% H2SO4 and 68 wt% HNO3, ultrasonic treatment is performed at 45-60 °C for 5-8 h, the mixture is diluted by pouring into 500 mL deionized water, 0.20-0.25 μm polytetrafluoroethylene membrane is used for filtration, the pH value is adjusted to 6.5-7.5, and centrifugation, filtration and washing are performed to obtain carbon nanotubes, the obtained carbon nanotubes are dispersed in deionized water by ultrasonic treatment to obtain a carbon nanotube suspension, and the usage ratio of the mixed solution and the single-walled carbon nanotubes is 0.6 mL:1-1.4 g, the volume ratio of 98 wt% H2SO4 and 68 wt% HNO3 is 3:1, and the concentration of the carbon nanotube suspension is 1 mg / mL.

7. The method of recovering p-aminophenol from wastewater according to claim 1, wherein The crude p-aminophenol in step (3) is 30-40% of the mass of deionized water.

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