A modified resin-based activated carbon, its preparation method and its application in carboxylic acid wastewater treatment

Abstract

The present invention relates to a modified resin-based activated carbon, a preparation method thereof, and an application thereof in the treatment of carboxylic acid wastewater, and belongs to the field of resource recovery treatment of salt-containing refractory organic wastewater. A modified resin-based activated carbon comprises granular resin-based activated carbon; carbon nanotubes are in situ grown on the surface of the resin-based activated carbon. The modified resin-based activated carbon stabilizes C atoms in the subsequent carbonization process, reduces the production of tar, and improves the yield of carbon balls; improves the thermal stability of the resin balls, making them less likely to melt or structurally collapse during high-temperature carbonization, which is beneficial to maintaining good sphericity; the large amount of skeleton oxygen introduced is beneficial to the formation of abundant weakly polar ether groups (Ether group) during the carbonization process, thereby forming important adsorption sites for carboxylic acid; the adsorbent surface has high roughness and possesses a large number of coral-like carbon nanotubes, which is beneficial to the rapid progress of the mass transfer process at the liquid-solid micro-interface.

Description

Technical Field

[0001] The invention relates to a modified resin-based activated carbon, a preparation method thereof and application in carboxylic acid wastewater treatment, and belongs to the field of resource treatment of salt-containing refractory organic wastewater. Background Art

[0002] Water is a precious resource essential for human survival, but human activities discharge vast quantities of industrial, agricultural, and domestic waste into water bodies, polluting them. The "Water Pollution Prevention and Control Law of the People's Republic of China" defines "water pollution" as the presence of substances that alter the chemical, physical, biological, or radioactive properties of water, thereby affecting its effective use, endangering human health, damaging the ecological environment, and deteriorating water quality. Human wastewater can generally be divided into two categories: domestic sewage and industrial wastewater. Domestic sewage, originating from urban residential areas, hospital living quarters, and factory living quarters, generally does not contain toxic substances and can be treated by physical, chemical, and biological methods to meet discharge standards. An analysis of the current state of wastewater management reveals that a significant portion of industrial wastewater discharged untreated or failing to meet discharge standards after certain treatment processes is difficult-to-treat organic wastewater. This type of wastewater primarily originates from the chemical industry, such as pesticide wastewater, dye wastewater, pharmaceutical wastewater, and organic synthesis wastewater. Industrial wastewater, with its complex composition, particularly the high content of toxic, harmful, and recalcitrant organic matter in chemical industry wastewater, presents both a key and challenging area for water pollution control.

[0003] Wastewater treatment units can be categorized by their working principle as physical, chemical, and biological. Common physical treatment methods include sedimentation, flotation, filtration, and centrifugation; common physicochemical treatment methods include coagulation, adsorption, extraction, ion exchange, and membrane separation. Their disadvantage is that pollutants are merely transferred from one phase of the water to another, essentially failing to remove them. Commonly used microbial treatment technologies include aerobic activated sludge, anaerobic, biofilm, and enzyme biotreatment. Their disadvantages include long treatment times, large equipment footprints, large amounts of sludge generated, poor treatment effectiveness, and significant seasonality. Advanced Oxidation Processes (AOPs), a chemical oxidation method, were developed in the 1980s for treating refractory organic pollutants. Their characteristic is that they use hydroxyl radicals (·OH) generated in the reaction to oxidize refractory, large-molecule toxic organic pollutants in wastewater into less toxic or non-toxic small molecules, or even completely oxidize them into CO2, H2O, and other small-molecule carboxylic acids, thereby achieving pollutant degradation. Advanced oxidation processes (AOPs) have attracted worldwide attention due to their advantages, including strong oxidizing capacity, low selectivity for organic matter, high treatment efficiency, and easily controlled operating conditions. They are playing an increasingly important role in wastewater treatment. These processes generally include ozone oxidation, hydrogen peroxide oxidation, persulfate oxidation, chlorine oxidation, electrocatalytic oxidation, photocatalytic oxidation, wet / catalytic wet oxidation, and combinations of these methods.

[0004] Carboxylic acids produced by advanced oxidation treatment of industrial wastewater are important chemical raw materials, widely used in industries such as basic synthesis, pharmaceuticals, dyes, fragrances, pesticides, food, printing and dyeing, leather, and metallurgy. Direct discharge without recovery and treatment pollutes the environment and wastes resources. Therefore, recovering carboxylic acids from advanced oxidation effluents offers significant economic, environmental, and social benefits.

[0005] Currently, commonly used methods for recovering carboxylic acids both domestically and internationally include distillation, extraction, esterification, neutralization, adsorption, ion exchange, membrane separation, and combinations of these methods. Since the carboxylic acid content in the effluent from advanced oxidation is generally low (10-2000 mg / L), only adsorption and ion exchange are suitable. In "Study on the Adsorption of Acetic Acid by Ion Exchange Resins," Cao Ying of Wuhan University of Technology reported that the macroporous weakly basic anion exchange resin D301G recovered 1.2 wt.% acetic acid solution at 25°C, achieving an adsorption rate of 98.13%. However, after regeneration with 4% NaOH solution, performance decreased by 13.28%. Before use, the resin undergoes a complex pretreatment regimen: NaCl solution → distilled water → hydrochloric acid solution → sodium hydroxide solution → hydrochloric acid solution → sodium hydroxide solution → ethanol extraction → drying. Wang Chuanzeng of the China Astronaut Research and Training Center noted in his paper "Experimental Study on Acetic Acid Removal by Ion Exchange" that as early as 1975, astronauts aboard the Soviet Salyut space station began drinking condensate-recycled water. Condensate also provided 80% of the drinking water for astronauts aboard the Mir space station. The average TOC content in condensate is approximately 85-158 mg / L, with varying levels. Small-molecule alcohols constitute the majority of pollutants in condensate wastewater. These polar organic compounds are difficult to remove by adsorption, typically by oxidizing them into organic acids before removal by ion exchange. Resins with high acetic acid adsorption capacities include IRA67, IRA96, D301, and 201×4. The ion exchange resins mentioned in the study can only adsorb salt-free condensate.

[0006] In recent years, the research and production of activated carbon has rapidly advanced, with ever-improving quality, a growing variety of products, and a broadening range of applications. Initial applications in sugar, pharmaceuticals, and monosodium glutamate processing have expanded to include solvent recovery, wastewater treatment, air purification, desulfurization, gas masks, catalyst supports, blood purification, and supercapacitors. With the development of diverse activated carbon types and applications, its applications are poised to expand further.

[0007] Activated carbon can be categorized by its specific form: powdered activated carbon (PAC), activated carbon fiber (ACF), and granular activated carbon (GAC). While powdered activated carbon is inexpensive, its dispersed pore structure leads to poor specific adsorption performance, susceptibility to secondary contamination, and difficulty in regeneration, limiting its use. Activated carbon fiber, with its predominantly microporous pore size distribution, offers rapid adsorption and desorption rates and a high adsorption capacity, but is more suitable for gas-phase adsorption and is less susceptible to backwashing than granular activated carbon. Spherical activated carbon, a form of granular activated carbon, was initially developed in the United States, Germany, Japan, and the Soviet Union. It was not until the 1980s that industrial production began and its use in a wide range of applications began. Compared to powdered, columnar, and flake activated carbon, spherical activated carbon boasts a large fluid contact area, low resistance, and excellent flowability, while also producing significantly less dust than the other three forms. Like conventional activated carbon, spherical activated carbon exhibits a certain degree of porosity and a basic microcrystalline structure.

[0008] Spherical activated carbon has the advantages of large specific surface area, high mechanical strength, low impurity content, good sphericity, wide availability, excellent adsorption performance and easy desorption. It has a wide range of applications in environmental protection and as a catalyst carrier. Currently, there are many reports on the use of resin as a precursor for spherical activated carbon, but generally the carbonized product must be activated before it can be used. Activation of the carbonized product involves adding chemical reagents or introducing water vapor, CO2, or other agents to expand the pores and increase the volume. A literature document discloses a method for preparing resin-based spherical activated carbon. This involves soaking the carbonized spherical polymer in an alkaline alcohol solution and then subjecting it to water vapor and CO2 activation, resulting in spherical activated carbon with a median particle size of 0.02-1.0 mm. This alkaline alcohol treatment of the carbonized initial product maintains its sphericity and helps control pore volume and pore size. However, this method increases the preparation cost of the spherical activated carbon and the alkaline alcohol solution also leads to unnecessary wastewater treatment costs. Another literature document discloses a spherical activated carbon prepared using a macroporous, strongly acidic cation exchange resin D001 as a precursor through carbonization and KOH activation. The adsorption and desulfurization performance of the spherical activated carbon was investigated, and the adsorption performance was significantly improved compared to commercial coal-based activated carbon F400. Using KOH as an activation agent also increases environmental protection costs and process operation and operating costs. Research by Nakashima et al. demonstrated that phenolic resin-based spherical activated carbon exhibits irreversible adsorption of carbon dioxide, with the residual CO₂ in the spherical activated carbon after a single adsorption and desorption step being 30 cm³ / L. Research by Li Yuan et al. demonstrated an average desulfurization rate of 87% for spherical activated carbon, significantly higher than the 53% for conventional activated carbon. However, the reported pre-oxidation methods for spherical activated carbon preparation have been limited to air oxidation or sulfuric acid sulfonation. The resulting spherical activated carbon, similar in microstructure to conventional coconut shell charcoal, is unable to specifically adsorb carboxylic acids in wastewater.

[0009] Carboxylic acids (RCOOH) are one of the most important organic acids in the chemical industry. Their functional group is -COOH. In the general formula RCOOH, R represents an aliphatic or aromatic group, respectively referred to as a fatty acid or aromatic acid. Depending on the number of carboxyl groups, acids can be classified as monobasic, dibasic, and polybasic. They can also be categorized as saturated or unsaturated. They are acidic and react with bases to form salts.

[0010] In a carboxylic acid molecule, the carboxyl carbon atom forms three σ bonds with the hydrocarbon group and two oxygen atoms using sp2 hybrid orbitals. These three σ bonds are in the same plane. The remaining p electron forms a π bond with the oxygen atom, forming the π bond of the C=O in the carboxyl group. However, the oxygen atom on the -OH moiety of the carboxyl group has a pair of unshared electrons, which can form a p-π conjugated system with the π bond. Due to the p-π conjugation, the electron cloud on the oxygen atom in the -OH group shifts toward the carbonyl group, and the electron cloud between the OH atoms is closer to the oxygen atom, which increases the polarity of the OH bond and facilitates the dissociation of the H atom. The H atom has a positive charge, allowing negatively charged groups to form bonds with the H atom. Therefore, carboxylic acids are more acidic than alcohols. When the carboxylic acid releases the H atom, the p-π conjugation becomes more complete, the bond length becomes equalized, and the negative charge on the -COOˉ group is no longer concentrated on a single oxygen atom, but is evenly distributed between the two oxygen atoms.

[0011] The carboxylic acid content in the effluent of advanced oxidation is generally low (30-2000 mg / L), and only ion exchange and adsorption methods are suitable for effective recovery.

[0012] Ion exchange resins, the core element of ion exchange methods, are polymer materials with ion exchange capabilities. In solution, they can exchange their own ions for ions of the same sign in the solution. Ion exchange resins can be divided into two categories, cation exchange resins and anion exchange resins, depending on the nature of the exchange groups. Because ion exchange is reversible, used ion exchange resins are typically washed with an appropriate concentration of inorganic acid or alkali to restore them to their original state for reuse. This process is called regeneration. Cation exchange resins can be washed with solutions such as dilute hydrochloric acid and dilute sulfuric acid; anion exchange resins can be regenerated by treating them with solutions such as sodium hydroxide.

[0013] Most cation exchange resins contain acidic groups such as sulfonic acid (-SO3H), carboxyl (-COOH) or phenol (-C6H4OH), in which the hydrogen ions can exchange with metal ions or other cations in the solution. Strong acid cation exchange resin: mainly contains strongly acidic reactive groups such as sulfonic acid (-SO3H), this ion exchange resin can exchange all cations. Weak acid cation exchange resin: has weaker reactive groups such as carboxyl (-COOH), this ion exchange resin can only exchange cations in weak bases such as Ca 2+ and Mg 2+ , for ions in strong bases such as Na + and K + etc. cannot be exchanged.

[0014] For example, the polymers of styrene and divinylbenzene are sulfonated to obtain a strong acidic cation exchange resin, whose structural formula can be simply expressed as R-SO3H, where R represents the resin matrix. Its exchange principle is:

[0015] 2R-SO3H+Ca 2+ →(R-SO3)2Ca+2H + This is also the principle of hard water softening. The effluent from industrial wastewater treated by advanced oxidation process often contains Na + , K + , Ca 2+ and Mg 2+ Inorganic cations such as cation exchange resin can be removed and then regenerated with hydrochloric acid solution.

[0016] Anion exchange resins contain basic groups such as quaternary amine [-N(CH3)3OH], amine (-NH2) or imine (=NH). They can generate OH in water. - Ions can exchange with various anions, and the exchange principle is:

[0017] RN(CH3)3OH+Cl - →RN(CH3)3Cl+OH -

[0018] from Figure 1 It can be seen that when anion exchange resins are commonly used in the prior art to recover carboxylic acids, in advanced oxidation effluents containing inorganic salts, basic groups preferentially exchange with inorganic anions, which are present in higher concentrations. Therefore, ion exchange resins cannot effectively recover carboxylic acids from the advanced oxidation effluent. Furthermore, ion exchange resins require complex pretreatment processes before use and require adequate protection during use, making them more complex for advanced oxidation effluents containing low levels of inorganic salts. Furthermore, even low levels of inorganic salts in the oxidation effluent will compete with carboxylic acids for exchange, significantly reducing the resin's adsorption capacity for carboxylic acids. Summary of the Invention

[0019] Aiming at the characteristics that the salt and organic matter in the advanced oxidation effluent are mainly carboxylic acids, the present invention adopts special oxidation modification and superstructure modification as core technologies to prepare a modified resin-based activated carbon with specific adsorption for carboxylic acids.

[0020] In one aspect, the present invention provides a modified resin-based activated carbon, comprising granular resin-based activated carbon; carbon nanotubes are in-situ grown on the surface of the resin-based activated carbon.

[0021] More preferably, in the modified resin-based activated carbon, more than 80% of the resin-based activated carbon has a particle size of 0.04 to 3 mm.

[0022] Optionally, the resin-based activated carbon is in the form of spherical particles, flaky particles, columnar particles, or irregular particles.

[0023] Further preferably, the content of carbon nanotubes in the modified resin-based activated carbon is 0.01 to 5.00 wt.% of the total weight of the modified resin-based activated carbon;

[0024] Optionally, the carbon nanotubes are multi-walled carbon nanotubes and / or single-walled carbon nanotubes;

[0025] Optionally, the diameter of the single-walled carbon nanotubes is distributed between 5 and 50 nm, and the carbon nanotubes with diameters concentrated between 10 and 20 nm account for more than 70%;

[0026] Optionally, the innermost layer diameter of the multi-walled carbon nanotube is 5 to 25 nm, and the outermost layer diameter is 6 to 50 nm;

[0027] Optionally, the particle size of the granular resin-based activated carbon is 2,000 to 400,000 times the diameter of the carbon nanotube.

[0028] Further preferably, the surface of the resin-based activated carbon has ether groups.

[0029] Optionally, the content of the ether groups is 0.5 to 10.0% of the total weight of the modified resin-based activated carbon, calculated as oxygen content.

[0030] Preferably, the modified resin-based activated carbon is a carbon ball, the bulk density of the carbon ball is 400 to 1000 g / L, and the BET specific surface area is 100 to 1600 m 2 / g; pore volume is 0.10-0.70cm 3 / g; pore diameter is 0.1~8nm.

[0031] On the other hand, the present invention provides a method for preparing modified resin-based activated carbon, wherein a raw material containing an ion exchange resin is subjected to oxidation treatment and carbonization treatment in sequence to prepare the modified resin-based activated carbon.

[0032] This method produces ether-rich, specific spherical activated carbon. The carbon spheroid preparation process consists of two main steps: oxidation and carbonization. The raw material can be fresh or spent ion exchange resin. The resulting modified resin-based activated carbon is a synthetic activated carbon, distinct from traditional adsorbents such as ion exchange resins, tar charcoal, bamboo charcoal, coal-based charcoal, and coconut shell charcoal.

[0033] Optionally, the oxidation treatment process is selected from at least one of hydrogen peroxide oxidation, ozone oxidation, electric anode oxidation, photocatalytic oxidation, high-temperature air oxidation and wet air oxidation.

[0034] Optionally, the oxidation treatment temperature of the high-temperature air oxidation treatment and the wet air oxidation treatment is 250-300°C; the lower limit of the oxidation treatment temperature is selected from 250°C and 260°C; the upper limit is selected from 260°C and 300°C.

[0035] Optionally, the oxidation treatment temperature of the hydrogen peroxide oxidation, ozone oxidation, electric anode oxidation, and photocatalytic oxidation is 25-100°C.

[0036] Optionally, a catalyst is added during the oxidation treatment, wherein the catalyst is a metal inorganic salt, the metal being selected from at least one of Mn, Fe, Co, Ni, Cu, and Zn. Preferably, the inorganic salt is selected from at least one of nitrates, sulfates, and chlorides. The inorganic salt catalyst can interfere with the oxidation process, increase free radical yield, reduce tar yield, promote graphite structure formation during resin carbonization, and increase the oxygen content of the resin skeleton. The prepared resin-based activated carbon contains the aforementioned metal elements; the residual elements contain the following weight percentages: Mn 0-6 wt.%; Fe 0-6.5 wt.%; Co 0-6 wt.%; Ni 0-6 wt.%; Cu 0-6 wt.%; Zn 0-6 wt.%; S 0-6.5 wt.%.

[0037] Optionally, the added amount of the catalyst is 0% to 10% of the total mass of the ion exchange resin;

[0038] Further preferably, an oxidizing agent is added during the oxidation treatment, wherein the oxidizing agent is selected from at least one of dicyandiamide, melamine, and urea. The oxidizing agent (also known as a nitrogen modification agent) can generate hydrophilic superstructured carbon nanotubes on the surface of the carbon spheres, further increasing the adsorption capacity of the carbon spheres.

[0039] Optionally, the added amount of the oxidation aid is 0% to 50% of the total mass of the ion exchange resin.

[0040] Further preferably, the carbonization treatment is performed in an inert atmosphere; preferably, the inert atmosphere is selected from at least one of nitrogen, helium, and argon; preferably, the heat treatment temperature is 750-900°C, and the heat treatment time is 0.5-12 hours. The lower limit of the heat treatment temperature is selected from 750°C and 800°C; the upper limit is selected from 800°C and 900°C. A rotary gas furnace is used for carbonization, and the carbonization atmosphere is a mixture of one or more of nitrogen, helium, or argon. After carbonization, functional groups such as hydrogen (-H), hydroxyl (-OH), carboxyl (-COOH), and carbonyl (-C=O) on the surface of the modified resin are removed, and modified resin-based activated carbon is finally obtained.

[0041] The present invention also provides the use of any of the above-mentioned modified resin-based activated carbons or the modified resin-based activated carbons obtained by any of the preparation methods as an adsorption material.

[0042] Preferably, the adsorption material is used for wastewater treatment.

[0043] Optionally, the wastewater is organic wastewater; preferably organic wastewater, more preferably salt-containing organic wastewater; the organic wastewater is preferably wastewater containing carboxylic acid; the carboxylic acid is preferably a small molecule carboxylic acid, more preferably C 1-4 carboxylic acid.

[0044] Optionally, the amount of carboxylic acid in the wastewater is 30 mg / L to 5000 mg / L in terms of TOC; the above-mentioned adsorption material is used to treat the advanced oxidation effluent to adsorb carboxylic acid, so that the TOC of the carboxylic acid in the wastewater is less than 30 mg / L.

[0045] Optionally, the salt in the saline organic wastewater is an inorganic alkali metal salt and / or an alkaline earth metal-free salt.

[0046] Preferably, the salt comprises at least one of CaCl2, NaCl, NaNO3, Na2SO4, and Na3PO4.

[0047] Calculated based on the mass of metal ions, the salt content in the wastewater source is 0.5-25%.

[0048] The modified resin-based activated carbon has an adsorption capacity of ≤0.5% for salt in wastewater.

[0049] The saline organic wastewater referred to herein specifically refers to saline organic wastewater whose primary organic component is carboxylic acid, with a carboxylic acid content of 30 mg / L to 5000 mg / L (measured as TOC). The salts contained are a mixture of one or more salts selected from CaCl2, NaCl, NaNO3, Na2SO4, and Na3PO4. The saline wastewater originates from chemical production wastewater or effluent treated with advanced oxidation technologies such as ozone oxidation, hydrogen peroxide oxidation, persulfate oxidation, chlorine oxidation, electrocatalytic oxidation, photocatalytic oxidation, and wet / catalytic wet oxidation. The oxidation technologies involved can be a combination of one or more. This adsorption technology can achieve near-complete removal of organic matter from saline organic wastewater, resulting in a pure salt solution with a TOC of less than 30 mg / L, which can be used as a raw material for industrial production. The use of this adsorption material can create an economical, recyclable, and green production process for enterprises.

[0050] The prepared carbon balls can also be made porous by alkali, carbon dioxide or water vapor method to increase their specific surface area, which can be used for adsorption of other organic matter and as catalyst carrier.

[0051] The beneficial effects that the present invention can produce include:

[0052] The present invention utilizes one or a combination of oxidation technologies, including hydrogen peroxide oxidation, ozone oxidation, electroanodic oxidation, photocatalytic oxidation, high-temperature air oxidation, and wet air oxidation, while simultaneously adding one or more inorganic salts selected from the group consisting of Mn, Fe, Co, Ni, Cu, and Zn as catalysts, and dicyandiamide, melamine, and urea as oxidizing agents, to perform resin oxidation modification. This results in a modified resin-based activated carbon with a sphericity greater than 90% and a temperature resistance of -25°C to 320°C. After oxidation modification, functional groups such as hydroxyl (-OH), carboxyl (-COOH), and carbonyl (-C=O) are generated on the resin surface; the cross-linked structure of the resin skeleton is destroyed, and oxygen atoms are introduced, forming a "COC-" structure. This modified resin-based activated carbon structure has the following advantages:

[0053] a. Stabilize C atoms in the subsequent carbonization process, reduce tar production, and increase carbon ball yield;

[0054] b. Improve the thermal stability of the resin balls, making them less likely to melt or collapse during high-temperature carbonization, which is beneficial for maintaining good sphericity;

[0055] c. The introduction of a large amount of skeleton oxygen facilitates the formation of abundant weakly polar ether groups during the carbonization process, thereby forming important adsorption sites for carboxylic acids;

[0056] d. The adsorbent has a high surface roughness and contains a large number of coral-like carbon nanotubes, which is conducive to the rapid mass transfer process at the liquid-solid micro-interface.

[0057] The modified resin-based activated carbon can be used as an adsorption material to achieve almost complete removal of organic matter in saline organic wastewater, and can form an economical and recyclable green production process for enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Schematic diagram of anion exchange resin in the prior art

[0059] Figure 2 This is a flow chart for preparing the modified resin-based activated carbon of the present invention;

[0060] Figure 3 The diagram shows the adsorption / desorption mechanism of carboxylic acid on the modified resin-based activated carbon of the present invention;

[0061] Figure 4 The morphology of carbon ball 1# prepared in Example 1 of the present invention is shown in Figure 1, where a is the particle morphology; b is the crucible sample; and c is the glass sample.

[0062] Figure 5 This is an electron microscope image of carbon ball 1# prepared in Example 1 of the present invention, wherein a is magnified 5000 times; b is magnified 2000 times; c is magnified 500 times;

[0063] Figure 6 For comparative example test example 1, the ion exchange resin adsorption experiment of the effluent from the oxidation of epichlorohydrin high-salt wastewater CWAO;

[0064] Figure 7 The adsorption effect of different resins on acetic acid in the absence of salt;

[0065] Figure 8 The adsorption effect of different resins on acetic acid in 1% NaCl solution;

[0066] Figure 9 The adsorption effect of different resins on acetic acid in 5% NaCl solution;

[0067] Figure 10 This is the adsorption curve of Formosa Plastics wastewater by resin and coconut shell charcoal;

[0068] Figure 11 In the figure, a is the SEM image of carbon ball 0# prepared in comparative example 1; b, c, and d are SEM images of carbon ball 1# prepared in example 1 at magnifications of 2000, 10000, and 30000 times, respectively. DETAILED DESCRIPTION

[0069] The present invention is described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0070] Unless otherwise specified, the raw materials and catalysts in the examples of the present invention were purchased from commercial sources.

[0071] In the embodiments of the present invention, the characterization and analysis methods of the samples are as follows:

[0072] (1) The specific surface area of the sample was analyzed by N2 adsorption-desorption experiment. The analytical instrument was Quanta Chrome's AutosorbiQ Station 2. The test conditions were 300℃ pretreatment for 5h and constant temperature adsorption at 77K with N2 as the adsorbent.

[0073] (2) Ether content (measured as oxygen content) was quantified using an organic element analyzer. The main components of the sample were C, H, O, and S. The test modes were: CH2SO4 mode and O mode. The required sample size was 50 mg.

[0074] Test item: EA

[0075] Instrument model: ELEMENTAR varioELlll or unicube

[0076] Test mode: CHNS mode, O mode.

[0077] Principle: It mainly uses the high temperature combustion method to analyze the content of conventional organic elements in samples.

[0078] Common elements found in organic matter include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S). Under high-temperature, oxygen-containing conditions, organic matter can burn. After combustion, the organic elements are converted into corresponding stable forms, such as CO2, H2O, N2, and SO2. Given a known sample mass, the content of each element in the sample can be determined by measuring the amount of gaseous products generated after complete combustion and performing conversions.

[0079] EA has three measurement modes: CHN mode, CHNS mode, and oxygen mode.

[0080] CHNS mode:

[0081] The sample is burned in pure oxygen and converted into CO2, H2O, N2 and SO2. After separation by chromatographic column, thermal conductivity detection is performed to measure the content of C, H, N and S in the sample.

[0082] Oxygen Mode:

[0083] The sample is cracked at high temperature in H2 / He to obtain CO and other gases. The CO is separated and detected by thermal conductivity to measure the oxygen content in the sample.

[0084] (3) Quantitative method for carbon nanotube content in modified resin-based activated carbon:

[0085] The carbon balls prepared by the preferred method of adding catalysts and nitrogen modification reagents have superstructure characteristics. Carbon nanotubes are grown in situ on the surface of the carbon balls. The ether functional groups on the carbon nanotubes have the characteristics of rapid adsorption and desorption. The specific quantitative method is as follows:

[0086] Take two portions of resin beads of equal weight. One portion is carbonized without nitrogen modification reagent to obtain m1 g of carbon beads. The other portion is carbonized with nitrogen modification reagent to obtain m2 g of superstructured carbon beads. After acid washing and drying, the resulting superstructured carbon beads weigh m3 g.

[0087] The mass ratio of carbon nanotubes in superstructured carbon balls can be estimated as X = (m2-m1) / m3*100%

[0088] (4) The morphological characteristics of the samples were analyzed by scanning electron microscopy (SEM). The analysis instrument was a JSM6360LV SEM with the following performance indicators: accelerating voltage 0.5-30 kV, magnification: 18-50,000 times, resolution: 3.0 nm in high vacuum, 4.5 nm in low vacuum. It was equipped with an energy dispersive spectrometer and EBSD analysis system.

[0089] (5) COD was determined by microwave digestion method based on the potassium dichromate method in GB11914-89. BOD5 was determined by BODTrak TM TOC was analyzed by TOC-V produced by Shimadzu Corporation of Japan. CPH / CPN The TOC removal rate (%) is measured by a type instrument to analyze the content of organic matter. in -TOC out ) / TOC in *100.

[0090] Comparative Example 1 Preparation of unmodified resin-based activated carbon

[0091] A styrene-based WS370 resin was selected and wet oxidized at 200°C and 3MPa O2 partial pressure for 2h, with a solid-to-liquid ratio of 10%; the obtained oxide was dried at 120°C for 2h and then air oxidized in a rotary gas furnace at an oxidation temperature of 260°C, an air flow rate of 25% (material volume) / min, and an oxidation time of 6h; after the oxidation was completed, nitrogen was introduced at a nitrogen flow rate of 20% (material volume) / min, and the resin was heat treated and carbonized at 800°C for 2h to obtain spherical unmodified resin-based activated carbon (carbon ball 0#).

[0092] Figure 11 Figure a is a SEM image of carbon ball 0# at a magnification of 2000 times. It can be seen that the surface of the carbon ball is relatively smooth, which is not conducive to the adsorption of organic matter.

[0093] Example 1 Preparation of modified resin-based activated carbon

[0094] A styrene-based WS370 resin was selected and wet oxidized at 200°C and 3MPa O2 partial pressure for 2h, wherein the solid-to-liquid ratio was 10%; the obtained oxide was dried at 120°C for 2h, and then 5% of Fe(NO3)3·9H2O by weight of the WS370 resin and 4% of dicyandiamide by weight of the WS370 resin were added and mixed, and then air oxidized in a rotary gas furnace at an oxidation temperature of 260°C, an air flow rate of 25% (material volume) / min, and an oxidation time of 6h; after the oxidation was completed, nitrogen was introduced at a nitrogen flow rate of 20% (material volume) / min, and the product was heat-treated and carbonized at 800°C for 2h to obtain spherical modified resin-based activated carbon (carbon ball 1#).

[0095] The test results show that the bulk density of carbon ball 1# is 650g / L and the BET specific surface area is 700m 2 / g, pore volume 0.40cm 3 / g, an average pore diameter of 3nm, an average particle size of 0.8mm, a sphericity greater than 92%, a temperature resistance of -25 to 320°C, an Fe content of 6.5%, a surface ether group content of 6.0%, and a content of in-situ grown carbon nanotubes of 2.5%.

[0096] from Figure 2 and Figure 3 It can be seen that the carbon ball 1# prepared in the present invention relies on the abundant weakly polar ether groups (Ethergroup) to adsorb carboxylic acid and is also conducive to alkali desorption.

[0097] Figure 11 Figures b, c, and d are SEM images of carbon ball 1# at magnifications of 2000, 10000, and 30000 times, respectively. Compared with the morphology of comparative example 1 in Figure a, it can be seen that by modifying the carbon nanotube superstructure on the surface of the carbon ball, the surface roughness of carbon ball 1# is significantly improved, and it has a large number of coral-like carbon nanotubes, which is conducive to the rapid mass transfer process at the liquid-solid micro-interface. Figure 11 As can be seen from Figure d in the figure, the carbon nanotubes are single-walled carbon nanotubes and multi-walled carbon nanotubes, and the diameter of the single-walled carbon nanotubes is distributed between 40 and 50 nm; the innermost layer diameter of the multi-walled carbon nanotubes is 30 to 40 nm, and the outermost layer diameter is 40 to 50 nm; preferably, the particle size of the granular resin-based activated carbon is 2000 to 400,000 times the diameter of the carbon nanotubes.

[0098] The ether content (in terms of oxygen content) of carbon ball 1# was quantitatively tested using an organic element analyzer in CHOS mode and O mode. The oxygen content of the prepared carbon ball 1# was 10% of the total weight of the carbon ball.

[0099] A styrene-based WS370 resin was selected and wet oxidized at 200°C and 3MPa O2 partial pressure for 2h, wherein the solid-to-liquid ratio was 10%; the obtained oxide was dried at 120°C for 2h, and then 4% of dicyandiamide (based on the weight of the WS370 resin) was added and mixed, and then air oxidized in a rotary gas furnace at an oxidation temperature of 260°C, an air flow rate of 25% (material volume) / min, and an oxidation time of 6h; after the oxidation was completed, nitrogen was introduced at a nitrogen flow rate of 20% (material volume) / min, and the mixture was heat-treated and carbonized at 800°C for 2h to obtain spherical modified resin-based activated carbon (carbon ball 2#).

[0100] The ether content (in terms of oxygen content) of carbon ball 2# was quantitatively tested using an organic element analyzer in CHOS mode and O mode. The oxygen content of the prepared carbon ball 2# was only 5% of the total weight of the carbon ball.

[0101] (1) Resin ball pretreatment

[0102] Take 100mL of 0.8-1.2mm resin balls (including eight resin types: WD315, WDX6001, WD311, SD300, 945, D301-1, D301-2, D311) and wash them with 2L of deionized water for 2 hours; then wash them with 1L of 5% HCl solution and soak them for 8 hours, then drain the acid and rinse them with deionized water until neutral; finally, wash them with 1L of 5% NaOH solution and soak them for 8 hours, drain the alkali solution, and rinse them with deionized water until neutral. The pretreated resin balls are obtained and stored in deionized water for use.

[0103] (2) Catalytic wet oxidation treatment of high-salt wastewater

[0104] The wastewater to be treated in the experiment is high-salt wastewater from the preparation of epichlorohydrin by the glycerol method, which contains 20-30 wt.% of sodium chloride, the main organic matter is glycerol, diglycerol, triglycerol, etc., the COD is 80,000-120,000 mg / L, the TOC is 25,000-35,000 mg / L, and the pH is 10-14.

[0105] The wastewater to be treated is subjected to catalytic wet oxidation degradation reaction:

[0106] In the first step, 48 g of 37 wt% concentrated hydrochloric acid was added to the regulating tank to adjust the wastewater to pH 3.

[0107] In the second step, after adjusting the pH, the wastewater to be treated is diluted 4 times with deionized water;

[0108] The third step is to add the catalyst CuCl2 after dilution, with the addition amount being 0.1wt.% of the wastewater to be treated.

[0109] In the fourth step, after the catalyst is added, the wastewater to be treated is mixed with air through a pipeline and then enters a heat exchanger to be heated to 245°C;

[0110] The fifth step is to introduce the wastewater to be treated into the catalytic wet oxidation reaction tower after heating. The catalytic wet oxidation reaction temperature is 270 ° C, the reaction pressure is 6.5 MPa, and the wastewater air velocity is 1h -1 The gas flow rate is 40-80 mL / min. The outlet water is cooled to 45°C in the heat exchanger.

[0111] 50 mL of catalytic wet oxidation effluent was taken and the pH was adjusted to the desired value using concentrated H₂SO₄ and NaOH pellets. 5 g of filtered resin pellets were added and allowed to stand for 8 hours. After filtration, the TOC content was measured. The effluent TOC was 549 mg / L, with a TOC removal rate of 92.5% and a pH of 6.15.

[0112] From the experimental results, we can see that ( Figure 6), WD315 resin had the best treatment effect, with a TOC removal rate of up to 38.7%; pH had a great influence on the adsorption performance of the resin, and the best adsorption effect was achieved when pH was 3.

[0113] Comparative Test Example 2: Resin Adsorption Intermittent Experiment of Carboxylic Acid Wastewater

[0114] a. Adsorption of acetic acid solution 1000 mg / L acetic acid solution

[0115] Weigh 0.5g of acetic acid and dilute to 500mL. Take 50mL of 1000mg / L acetic acid solution in a reagent bottle and add 5g of each of the anion exchange resins No. 1 to 5 (1-WD-315, 2-D301, 3-945, 4-WD311, 5-D311) pretreated by the resin ball pretreatment method in Comparative Test Example 1 (1). Shake several times and let it sit overnight. Filter and dilute 5 times to measure TOC. Results are shown in the figure. Figure 7 .

[0116] b. Adsorption of saline acetic acid solution 1000ppm acetic acid + 1wt.% NaCl

[0117] Weigh 0.5g of acetic acid and 5g of NaCl, dilute to 500mL, take 50mL of saline acetic acid solution in a reagent bottle, add 5g of each of the anion exchange resins No. 1 to 5 (1-WD-315, 2-D301, 3-945, 4-WD311, 5-D311) pretreated by the method of Comparative Example 1, shake several times, let it sit overnight, filter, and dilute 5 times to measure TOC. The results are shown in the figure. Figure 8 .

[0118] c. Adsorption of saline acetic acid solution 1000ppm acetic acid + 5wt.% NaCl

[0119] Weigh 0.5g acetic acid and 25g NaCl, dilute to 500mL, take 50mL of saline acetic acid solution in a reagent bottle, add 5g of each of the anion exchange resins No. 1 to 5 (1-WD-315, 2-D301, 3-945, 4-WD311, 5-D311) pretreated by the method of Comparative Example 1, shake several times, let it sit overnight, filter, and dilute 10 times to measure TOC. The results are shown in the figure. Figure 9 .

[0120] from Figure 7 、 Figure 8 、 Figure 9, it can be seen that when the substrate is 1000 mg / L acetic acid, Resin No. 2 has the highest TOC removal rate, reaching over 80% after adsorption. When the substrate is 1000 mg / L acetic acid + 1 wt.% NaCl, the overall adsorption efficiency decreases significantly, falling below 10%. When the substrate is 1000 mg / L acetic acid + 5 wt.% NaCl, the acetic acid adsorption efficiency almost approaches zero. Therefore, anion exchange resins are not suitable for treating saline carboxylic acid wastewater.

[0121] Test Example 1 Continuous Wastewater Adsorption Experiment

[0122] The resin, carbon material, and carbon ball 1# prepared in Example 1 were subjected to continuous adsorption experiments.

[0123] The wastewater to be treated is the effluent CWAO of VW11B wastewater from the NAE plant of Formosa Plastics Acrylates Ningbo Co., Ltd. The wastewater quality is COD: 846 mg / L, more than 95% of the organic matter in the wastewater is organic carboxylic acid, pH: 8.0, salinity: 0.5%, and the inorganic salts are mainly sodium chloride and sodium sulfate.

[0124] a.Select Figure 6 The best resin WD-315 (particle size of 1.5-2.0 mm) was taken and about 50 mL was placed in the reactor. The pH of the wastewater was adjusted to 1.5 (3 mL of concentrated sulfuric acid / L of wastewater) and the mixture was heated at 50 mL·h -1 The flow rate is passed into the fixed bed reactor, and samples are taken at regular intervals to determine the COD.

[0125] b. Take about 50mL WS600 macroporous adsorption resin in the reactor, adjust the wastewater pH to 1.5 (add 3mL concentrated sulfuric acid / L wastewater), and -1 The flow rate is passed into the reactor, samples are taken regularly, and COD is measured.

[0126] c. Take about 50 mL of coconut shell carbon (LJHBYK-01, Shandong Lujing Activated Carbon Co., Ltd.) in the reactor, adjust the pH of the wastewater to 1.5 (add 3 mL of concentrated sulfuric acid / L of wastewater), and use 50 mL·h -1 The flow rate is passed into the reactor, samples are taken regularly, and COD is measured.

[0127] d. Take about 50 mL of carbon ball 1# prepared in Example 1 in the reactor, adjust the pH of the wastewater to 1.5 (add 3 mL of concentrated sulfuric acid / L of wastewater), and -1 The flow rate is passed into the reactor, samples are taken regularly, and COD is measured.

[0128] from Figure 10As can be seen, both the anionic resin WD-315 and the macroporous adsorption resin WS600 for organic matter showed poor treatment effects on the CWAO oxidation of acrylic acid wastewater, reaching saturation after just 5 hours. Under the same experimental conditions, coconut shell charcoal also had poor adsorption capacity, with the effluent COD exceeding 100 mg / L after just one hour of adsorption and continuing to rise, reaching saturation after 14 hours. However, carbon balls 1# prepared in Example 1 of the present invention exhibited superior adsorption effects on CWAO oxidation, with the effluent COD still below 50 mg / L after 36 hours.

[0129] Test Example 2 Adsorption and desorption test of modified resin-based activated carbon

[0130] In order to investigate the regeneration service life of the carbon ball 1# prepared in Example 1 and determine the COD adsorption capacity, the air velocity condition was 3h -1 , the concentration of sodium hydroxide desorption solution was 6%, and continuous cycle adsorption and desorption experiments were carried out.

[0131] To avoid failing to reach saturated resin adsorption capacity in the first three experiments, the single adsorption volume was increased, and 4-6 experiments were performed. The COD adsorption and desorption capacities are shown in Table 1. Multiple adsorption and desorption cycles did not significantly affect the total adsorption capacity of Carbon Ball 1#, indicating that Carbon Ball 1# has good stability.

[0132] Table 1 Carbon ball 1# continuous cycle adsorption and desorption experiment

[0133]

[0134] Notes:

[0135] pH of wastewater treated with ads 7 sample = 4.5;

[0136] pH0 of wastewater treated with samples ads 1-6, des1-6, and ads8 was 1.5;

[0137] pH of wastewater treated with ads 9 sample = 2.5;

[0138] The pH of wastewater treated with ads 10 sample was 3.5.

[0139] ADS / DESCOD (mg) is the total amount of COD continuously adsorbed / desorbed

[0140] Test Example 3 Broad-spectrum test of resin-based modified activated carbon

[0141] 1 g of carbon ball 1# prepared in Example 1 was weighed and added into 10 mL of 1000 mg / L acetic acid, propionic acid, n-butyric acid, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, acrylic acid, isobutyric acid, and salicylic acid solutions at pH 1, respectively, for 1 h.

[0142] The TOC values and TOC removal rates of the solutions before and after adsorption are shown in Table 2. As can be seen, the prepared carbon balls 1# exhibit excellent adsorption and removal capabilities for a variety of small-molecule organic acids. They are non-specific and suitable for adsorption treatment of advanced oxidation effluent, facilitating the resource recovery and utilization of carboxylic acids.

[0143] Table 2 Adsorption of various small molecule acids by carbon balls

[0144]

[0145] Test Example 4

[0146] The research object is the VW11B wastewater CWAO effluent of the NAE plant of Formosa Plastics Acrylates Ningbo Co., Ltd. The wastewater quality is COD: 846 mg / L, more than 95% of the organic matter in the wastewater is organic carboxylic acid, pH: 8.0, salinity: 0.5%, and the inorganic salts are mainly sodium chloride and sodium sulfate.

[0147] Adsorption equilibrium experiments were performed on carbon ball 0# prepared in comparative example 1 and carbon ball 1# prepared in example 1: 1 g of carbon ball 0# and carbon ball 1# were weighed and added into 10 mL of wastewater respectively. The adsorption equilibrium time of carbon ball 1# in example 1 was only 5 minutes, and the effluent COD was 3 mg / L; while the adsorption equilibrium time of carbon ball 0# was 60 minutes, and the effluent COD was 20 mg / L.

[0148] The above descriptions are merely several embodiments of the present invention and do not constitute any form of limitation to the present invention. Although the present invention is disclosed as above in terms of preferred embodiments, they are not intended to limit the present invention. Any technician familiar with the present profession who, without departing from the scope of the technical solution of the present invention, makes slight changes or modifications using the technical contents disclosed above are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing modified resin-based activated carbon, characterized in that: The method sequentially subjects a raw material containing an ion exchange resin to oxidation treatment and carbonization treatment to prepare the modified resin-based activated carbon; The ion exchange resin is styrene-based WS370 resin; A catalyst is added during the oxidation treatment, wherein the catalyst is a metal inorganic salt, and the metal is selected from at least one of Mn, Fe, Co, Ni, Cu, and Zn; Adding an oxidizing aid during the oxidation treatment, wherein the oxidizing aid is selected from at least one of dicyandiamide, melamine, and urea; The modified resin-based activated carbon is granular resin-based activated carbon; In-situ growth of carbon nanotubes on the surface of the resin-based activated carbon; The surface of the resin-based activated carbon has ether groups; The content of the ether groups is 0.5-10.0% of the total weight of the modified resin-based activated carbon, calculated as oxygen content. The ether groups are distributed on the surface of the carbon balls and the carbon nanotubes.

2. The preparation method according to claim 1, characterized in that In the modified resin-based activated carbon, more than 80% of the resin-based activated carbon has a particle size of 0.04 to 3 mm.

3. The preparation method according to claim 1, characterized in that The resin-based activated carbon is in the form of spherical particles.

4. The preparation method according to claim 1, characterized in that In the modified resin-based activated carbon, the content of the carbon nanotubes is 0.01 to 5.00 wt.% of the total weight of the modified resin-based activated carbon.

5. The preparation method according to claim 1, characterized in that The carbon nanotubes are multi-walled carbon nanotubes or single-walled carbon nanotubes.

6. The preparation method according to claim 5, characterized in that The diameter of the single-walled carbon nanotubes is distributed between 5 and 50 nm.

7. The preparation method according to claim 6, characterized in that The carbon nanotubes with diameters ranging from 10 to 20 nm account for more than 70%.

8. The preparation method according to claim 5, characterized in that The innermost layer diameter of the multi-walled carbon nanotube is 5 to 25 nm, and the outermost layer diameter is 6 to 50 nm.

9. The preparation method according to claim 1, characterized in that The particle size of the granular resin-based activated carbon is 2,000 to 400,000 times the diameter of the carbon nanotube.

10. The preparation method according to claim 1, characterized in that The modified resin-based activated carbon is a carbon ball, the bulk density of the carbon ball is 400 to 1000 g / L, and the BET specific surface area is 100 to 1600 m 2 / g; pore volume is 0.10-0.70cm 3 / g; pore diameter is 0.1~8nm.

11. The preparation method according to claim 1, characterized in that The oxidation treatment process is selected from at least one of hydrogen peroxide oxidation, ozone oxidation, electric anode oxidation, photocatalytic oxidation, high-temperature air oxidation and wet air oxidation.

12. The preparation method according to claim 11, characterized in that The temperature of the oxidation treatment of the high temperature air oxidation and wet air oxidation is 250-300°C; The temperature of the oxidation treatment of hydrogen peroxide oxidation, ozone oxidation, electric anode oxidation, and photocatalytic oxidation is 25 to 100° C. The inorganic salt is selected from at least one of nitrates, sulfates, and chlorides; The amount of the catalyst added is 0% to 10% of the total mass of the ion exchange resin; The added amount of the oxidation aid is 0% to 50% of the total mass of the ion exchange resin.

13. The preparation method according to claim 1, characterized in that The carbonization treatment is a heat treatment performed in an inert atmosphere; the inert atmosphere is selected from at least one of nitrogen, helium, and argon.

14. The preparation method according to claim 13, characterized in that The heat treatment temperature is 750-900° C., and the heat treatment time is 0.5-12 hours.

15. Use of the modified resin-based activated carbon obtained by the preparation method of any one of claims 1 to 14 as an adsorption material in the treatment of saline organic wastewater; The saline organic wastewater is saline wastewater containing carboxylic acid, and the carboxylic acid is a small molecule carboxylic acid.

16. The use according to claim 15, characterized in that The carboxylic acid is C 1-4 carboxylic acid.

17. The use according to claim 15, characterized in that The amount of carboxylic acid in the raw wastewater is 30 mg / L to 5000 mg / L in terms of TOC; the amount of carboxylic acid in the wastewater after adsorption treatment by the modified resin-based activated carbon is less than 30 mg / L.

18. The use according to claim 15, characterized in that The salt in the saline organic wastewater is an inorganic alkali metal salt or an inorganic alkaline earth metal.

19. The use according to claim 15, characterized in that The salt is at least one of CaCl2, NaCl, NaNO3, Na2SO4, and Na3PO4.

20. The use according to claim 15, characterized in that Calculated based on the mass of metal ions, the salt content in the wastewater is 0.5-25%; the adsorption of salt in the wastewater by the modified resin-based activated carbon is ≤0.5%.

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