Preparation method of a functionalized highly adsorbent adsorbent

Abstract

The invention discloses a preparation method of a functionalized highly adsorbent adsorbent, which comprises the following steps: preparation of an amino-terminated hyperbranched polymer; preparation of a carbon material: using waste biomass and waste polyvinyl chloride as raw materials, adding water and mixing them, then carrying out co-hydrothermal carbonization to obtain a solid-liquid mixture, roasting the solid part to obtain a solid product, soaking the solid product in an alkaline solution and then carrying out solid-liquid separation again, washing with water and drying to obtain the carbon material; preparation of the adsorbent: uniformly mixing the carbon material grafted with the amino-terminated hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid to form a mixed solution C, and polymerizing the mixed solution C under a redox-azo composite system to form the adsorbent. By adopting the above preparation method, the obtained adsorbent uses PVC and biomass solid waste as raw materials, the raw material sources are wide and it is easy to promote, and the adsorption performance for dyes methylene blue and malachite green is extremely excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbents, and particularly to a preparation method of a functionalized highly adsorbent adsorbent. Background Art

[0002] The large-scale use of dyes will produce a large amount of harmful wastewater, which has an adverse impact on human health and environmental safety. The adsorption method is an effective method for removing high-molecular dyes in water bodies, and has advantages such as flexibility, simplicity, and low cost. There are many types of adsorbents, among which adsorbents prepared from waste biomass have received extensive attention due to their rich raw materials, environmental protection, and low cost. Hydrothermal carbonization is an economic technology that can thermochemically convert biomass into carbon-rich products. Compared with other common technologies, the hydrothermal carbonization method has a simple process, mild reaction conditions, and rich surface functional groups (such as phenolic hydroxyl groups, lactone groups, etc.) on the product, which can adsorb and remove pollutants through ion exchange, electrostatic adsorption, surface complexation and other adsorption effects with pollutants.

[0003] Polyvinyl chloride (PVC) is widely used in daily life due to its high performance and low price. Polyvinyl chloride is usually stable in nature, not easily decomposed, and has a high chlorine content. Therefore, the treatment and disposal of PVC pose a serious challenge to the environment. Hydrothermal carbonization is an effective method for converting PVC into harmless value-added products. Through the hydrolysis and dechlorination reactions in the hydrothermal carbonization process, part of the organic chlorine in PVC can be converted into hydrochloric acid and enter the liquid phase, avoiding the ecological system pollution caused by landfill treatment and the air pollution caused by the emission of hydrogen chloride and organohalogen compounds generated by incineration. However, this process has low carbonization degree, low chlorine conversion rate, and poor dechlorination effect, and additional chemical reagents need to be added to improve the dechlorination efficiency.

[0004] In order to improve the adsorption effect of the adsorbent, new functional groups, such as carboxylic acid functional groups, need to be introduced on the surface of the product carbon, further enriching its surface chemical properties, significantly improving and enhancing the adsorption performance, broadening its application in environmental remediation, and at the same time, it is necessary to increase the carbonization degree and dechlorination degree of polyvinyl chloride to greatly improve the adsorption effect of the adsorbent. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a functionalized highly adsorbent adsorbent to solve the problems of poor adsorption effect of the adsorbent and waste utilization in the prior art.

[0006] To achieve the above purpose, the present invention provides a preparation method of a functionalized highly adsorbent adsorbent, including the following steps:

[0007] (1) Preparation of amino-terminated hyperbranched polymer

[0008] Mix absolute ethanol and amine compounds evenly, and stir well under nitrogen protection to form a mixed solution A. Then, slowly add the above mixed solution A dropwise to the mixed solution B formed by acrylate compounds and absolute methanol for reaction. After the reaction, an amino-terminated hyperbranched polymer is obtained.

[0009] (2) Preparation of carbon materials

[0010] Use waste biomass and waste polyvinyl chloride as raw materials, add water and mix them, then add them to a reaction kettle for co-hydrothermal carbonization to obtain a solid-liquid mixture. Perform solid-liquid separation on the solid-liquid mixture, place the solid part in a heating furnace with a protective atmosphere for roasting to obtain a solid product. Immerse the solid product in an alkaline solution for a period of time and then perform solid-liquid separation again. After washing with water until neutral and drying, carbon materials are obtained.

[0011] (3) Preparation of amino-terminated hyperbranched polymer-grafted carbon materials

[0012] Disperse the carbon materials in distilled water by ultrasonic wave to obtain a suspension, then add the amino-terminated hyperbranched polymer to the above suspension and continue ultrasonic dispersion to obtain a uniform mixed solution. Stir at 80 - 90 °C for 12 hours. After the reaction, amino-terminated hyperbranched polymer-grafted carbon materials are obtained.

[0013] (4) Preparation of adsorbent

[0014] Mix the amino-terminated hyperbranched polymer-grafted carbon materials, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid evenly to form a mixed solution C. The mixed solution C is polymerized under a redox-azo composite system to form an adsorbent.

[0015] Preferably, in step (1), the volume ratio of the amine compound to absolute ethanol is 1:1, the volume ratio of the acrylate compound to absolute ethanol is 1:1, and the mass ratio of the amine compound to the acrylate compound is 1:1. During the reaction, place the product under reduced pressure distillation at 60 °C for 2 hours, and then react at 120 °C for 7 hours to obtain an amino-terminated hyperbranched polymer.

[0016] Preferably, the amine compound in step (1) is one or more of tris(3-aminopropyl)amine, 1,2,4-triaminobenzene, and 1,3,5-triaminocyclohexane.

[0017] Preferably, in step (2), the waste biomass is one or more of waste fruit shells, peels, plant straws, livestock and poultry manure, municipal sludge, paper, garden waste, and wood chips; the waste polyvinyl chloride is one or more of waste plastics, electronic product casings, and printed circuit boards; the mass ratio of the waste polyvinyl chloride to the waste biomass is 1 - 5:1 - 20, and the particle size range of the raw materials is 0.5 mm - 5 mm.

[0018] Preferably, the solid-liquid mixture obtained in step (2) is subjected to a pH test, and the solid-liquid mixture is selectively diluted and left for a period of time according to the pH value. The pH range before and after selective dilution is 0-7. The solvent used for dilution is deionized water or tap water, and the standing time after dilution is 0-72 hours; the alkaline solution for soaking is a solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, ammonia water, etc., and the concentration range is 5-200 g / L.

[0019] Preferably, the temperature of the hydrothermal carbonization reaction in step (2) is 160°C - 350°C, the reaction time of the hydrothermal carbonization reaction is 1-48 h, the pressure of the hydrothermal reaction is 2-15 MPa, the solid-liquid mass ratio is 1:5 - 1:100, and the hydrothermal solvent is deionized water or tap water; the protective atmosphere in the heating furnace is an inert gas, the heating rate is 1-40°C / min, the heat preservation temperature is 250-450°C, and the heat preservation time is 5-180 min; the drying temperature range is 60-100°C, and the drying time is 30-180 min.

[0020] Preferably, in step (3), the mass fraction of the suspension is 5-8 wt%, and the mass ratio of the amino-terminated hyperbranched polymer to the carbon material is 1:100 - 150.

[0021] Preferably, the weight parts of the carbon material grafted with the amino-terminated hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid added in step (4) are 50-100 parts, 50-100 parts, 20-40 parts, and 60-80 parts respectively.

[0022] Preferably, the redox-azo composite system is a system composed of 0.3-0.5 parts of azo salt, 0.001-0.002 parts of tert-butyl peroxide, and 0.005-0.01 parts of ammonium ferrous sulfate.

[0023] Preferably, the azo salt is one or two of azodiisooctanenitrile, azodiethylcyanovaleric acid, and azo V044, and the tert-butyl peroxide is tert-butyl hydroperoxide.

[0024] Therefore, the preparation method of a functionalized highly adsorbent adsorbent adopting the above structure in the present invention has the following beneficial effects:

[0025] (1) Using waste PVC and waste biomass as raw materials, the raw material sources are extensive, and at the same time, the functionalized co-reutilization of two typical municipal solid wastes is realized, providing a new idea for urban energy conservation, emission reduction, green and low-carbon development in China.

[0026] (2) The waste of PVC and biomass is co-treated by co-hydrothermal carbonization and low-temperature activation methods. The raw materials do not need to be dried, and no additional chemical reagents are required for the reaction. It has the advantages of simple process, mild reaction conditions, controllable time, low equipment requirements, convenient separation and recovery of by-products, etc.

[0027] (3) On the one hand, in the present invention, a large number of free -OH in biomass are used to replace -Cl in PVC, improving the hydrolysis and dechlorination efficiency of PVC, promoting the conversion of organic chlorine into inorganic chlorine and entering the liquid phase, reducing environmental hazards. On the other hand, the hydrochloric acid generated by the hydrolysis of PVC is used to catalytically accelerate the hydrolysis and carbonization of biomass, remove metal ions contained in the biomass, and introduce a large number of carboxyl and hydroxyl functional groups generated by the hydrolysis of PVC into the hydrochar of biomass, effectively strengthening the surface active sites of the hydrochar product and improving its adsorption capacity for pollutants.

[0028] (4) The present invention fully utilizes the HCl generated by the dechlorination of PVC during the co-hydrothermal carbonization process to form an acidic solution, realizing the synchronous impregnation of the solid product of co-hydrothermal carbonization. By combining simple subsequent treatments such as selectively adjusting the pH value and impregnation time of the solid-liquid mixture, the in-situ activation and pore formation of the solid product of co-hydrothermal carbonization can be achieved through low-temperature heat treatment, achieving the purpose of self-activation without adding additional agents. At the same time, low-temperature activation can effectively retain the surface functional groups of the hydrochar, overcome the shortcomings of underdeveloped pore structure and low specific surface area of the co-hydrochar, and has a faster adsorption rate and better adsorption effect on pollutants.

[0029] (5) Cold alkali strengthening treatment further increases the specific surface area and oxygen-containing functional group content of the product adsorbent, changes the surface charge, makes the adsorbent more electronegative, and can effectively improve the removal ability of the porous carbon product for cationic pollutants, enhancing the actual application effect.

[0030] (6) By grafting the terminal amino hyperbranched polymer on the surface of the carbon material and combining subsequent polymerization reactions, a porous polymer layer is further formed on the surface of the carbon material, further increasing the adsorption effect of the adsorbent.

[0031] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0032] Figure 1 is the SEM image of the carbon material prepared in Example 1;

[0033] Figure 2 is the FT-IR image of the carbon materials of Example 1, Comparative Example 4 and Comparative Example 5. Detailed Embodiments

[0034] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution, and detailed implementation manners and specific operation processes are given, but the present invention is not limited to this embodiment.

[0035] Example 1

[0036] A preparation method of a functionalized highly adsorbent adsorbent, characterized in that it comprises the following steps:

[0037] (1) Preparation of amino-terminated hyperbranched polymer

[0038] Mix anhydrous ethanol and tris(3-aminopropyl)amine evenly. The volume ratio of tris(3-aminopropyl)amine to anhydrous ethanol is 1:1. Stir well under nitrogen protection to form a mixed solution A. Then slowly drop the above mixed solution A into the mixed solution B formed by ethyl acrylate and anhydrous methanol for reaction. The volume ratio of ethyl acrylate to anhydrous ethanol is 1:1, and the mass ratio of tris(3-aminopropyl)amine to ethyl acrylate is 1:1. During the reaction, place the product under reduced pressure distillation at 60 °C for 2 hours, and then react at 120 °C for 7 hours. After the reaction, an amino-terminated hyperbranched polymer is obtained;

[0039] (2) Preparation of carbon material

[0040] Use waste fruit shells and waste polyvinyl chloride plastics as raw materials, add water and mix them, then add them to a reaction kettle for co-hydrothermal carbonization to obtain a solid-liquid mixture. The temperature of the hydrothermal carbonization reaction is 200 °C, the reaction time of the hydrothermal carbonization reaction is 24 h, the pressure of the hydrothermal reaction is 5 MPa, the solid-liquid mass ratio is 1:10, the mass ratio of waste polyvinyl chloride to waste biomass is 2:10. The fruit shell is specifically a walnut shell, the particle size of the raw material is 2 mm. Test the pH of the solid-liquid mixture, and perform selective dilution treatment on the solid-liquid mixture according to the pH value and let it stand for a period of time. The pH range before and after selective dilution is 0-7, the solvent used for dilution is deionized water, and the standing time after dilution is 24 hours. Separate the solid and liquid of the solid-liquid mixture, place the solid part in a heating furnace with an inert gas protection atmosphere for roasting to obtain a solid product. The heating rate of the heating furnace is 20 °C / min, the holding temperature is 300 °C, and the holding time is 60 min. Immerse the solid product in a sodium hydroxide solution for a period of time and then perform solid-liquid separation again. The concentration of the sodium hydroxide solution is 10 g / L. Wash it with water until neutral and then dry it to obtain the carbon material. The drying temperature is 80 °C and the drying time is 90 min;

[0041] (3) Preparation of amino-terminated hyperbranched polymer grafted carbon material

[0042] The carbon material was ultrasonically dispersed in distilled water to obtain a suspension with a mass fraction of 6 wt%. Then, the amino-terminated hyperbranched polymer was added to the above suspension and ultrasonically dispersed continuously to obtain a homogeneous mixture. The mass ratio of the amino-terminated hyperbranched polymer to the carbon material was 1:120, and it was stirred at 85 °C for 12 hours. After the reaction, the carbon material grafted with the amino-terminated hyperbranched polymer was obtained.

[0043] (4) Preparation of the adsorbent

[0044] The carbon material grafted with the amino-terminated hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid were mixed evenly to form a mixed solution C. The weight parts added of the carbon material grafted with the amino-terminated hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid were 50 parts, 50 parts, 20 parts, and 70 parts respectively. The mixed solution C was polymerized into an adsorbent under an oxidation-reduction-azo composite system, and the oxidation-reduction-azo composite system was a system composed of 0.4 part of azobisisobutyronitrile, 0.002 part of tert-butyl hydroperoxide, and 0.008 part of ammonium ferrous sulfate.

[0045] Example 2

[0046] A preparation method of a functionalized highly adsorbent adsorbent, characterized in that it includes the following steps:

[0047] (1) Preparation of the amino-terminated hyperbranched polymer

[0048] Absolute ethanol and 1,2,4-triaminobenzene were mixed evenly. The volume ratio of tris(3-aminopropyl)amine to absolute ethanol was 1:1. Under the protection of nitrogen, it was fully stirred to form a mixed solution A. Then, the mixed solution A was slowly added dropwise to the mixed solution B formed by methyl acrylate and absolute methanol for reaction. The volume ratio of ethyl acrylate to absolute ethanol was 1:1, and the mass ratio of tris(3-aminopropyl)amine to ethyl acrylate was 1:1. During the reaction, the product was placed under reduced pressure distillation at 60 °C for 2 hours, and then reacted at 120 °C for 7 hours. After the reaction, the amino-terminated hyperbranched polymer was obtained.

[0049] (2) Preparation of the carbon material

[0050] Using waste wood chips and waste polyvinyl chloride plastics as raw materials, they are mixed with water and then added to a reaction kettle for co-hydrothermal carbonization to obtain a solid-liquid mixture. The temperature of the hydrothermal carbonization reaction is 300 °C, the reaction time of the hydrothermal carbonization reaction is 24 h, the pressure of the hydrothermal reaction is 5 MPa, the solid-liquid mass ratio is 1:10, the mass ratio of waste polyvinyl chloride to waste biomass is 2:10, the particle size of the raw materials is 3 mm. The solid-liquid mixture is subjected to a pH test, and the solid-liquid mixture is selectively diluted according to the pH value and left for a period of time. The pH range before and after selective dilution is 0-7, the solvent used for dilution is deionized water, and the time for standing after dilution is 24 hours. The solid-liquid mixture is separated by solid-liquid separation, and the solid part is placed in a heating furnace with an inert gas protection atmosphere for roasting to obtain a solid product. The heating rate of the heating furnace is 20 °C / min, the holding temperature is 300 °C, and the holding time is 60 min. The solid product is immersed in a sodium hydroxide solution for a period of time and then solid-liquid separation is carried out again. The concentration of the sodium hydroxide solution is 10 g / L, and after washing to neutrality and drying, a carbon material is obtained. The drying temperature is 80 °C and the drying time is 90 min;

[0051] (3) Preparation of carbon material grafted with terminal amino hyperbranched polymer

[0052] The carbon material is placed in distilled water and ultrasonically dispersed to obtain a suspension. The mass fraction of the suspension is 6 wt%. Then, the terminal amino hyperbranched polymer is added to the above suspension and ultrasonically dispersed continuously to obtain a homogeneous mixture. The mass ratio of the terminal amino hyperbranched polymer to the carbon material is 1:120, and it is stirred at 85 °C for 12 hours. After the reaction, a carbon material grafted with terminal amino hyperbranched polymer is obtained;

[0053] (4) Preparation of adsorbent

[0054] The carbon material grafted with terminal amino hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid are mixed evenly to form a mixed solution C. The weight parts added of the carbon material grafted with terminal amino hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid are 60 parts, 50 parts, 20 parts, and 70 parts respectively. The mixed solution C is polymerized into an adsorbent under an oxidation-reduction-azo composite system. The oxidation-reduction-azo composite system is a system composed of 0.4 parts of azobis(2-cyanovaleric acid), 0.002 parts of tert-butyl hydroperoxide, and 0.001 parts of ammonium ferrous sulfate.

[0055] Comparative Example 1

[0056] The difference from Example 1 is that in step (2), the waste fruit shells and waste polyvinyl chloride plastics are directly roasted in a heating furnace with an inert gas protection atmosphere to obtain a solid product, and the solid product is used as the carbon material.

[0057] Comparative Example 2

[0058] The difference from Example 1 is that tris(3-aminopropyl) is replaced with ethylenediamine.

[0059] Comparative Example 3

[0060] The difference from Example 1 is that the solid product obtained by roasting in a heating furnace in step (2) is directly used as the carbon material to react with the terminal amino hyperbranched polymer.

[0061] Comparative Example 4

[0062] The difference from Example 1 is that the waste polyvinyl chloride plastic in step (2) is used alone as a raw material to prepare the carbon material, and the waste fruit shell is not added.

[0063] Comparative Example 5

[0064] The difference from Example 1 is that the waste fruit shell in step (2) is used alone as a raw material to prepare the carbon material, and the waste polyvinyl chloride plastic is not added.

[0065] Comparative Example 6

[0066] The difference from Example 1 is that the solid in the solid-liquid mixture obtained by co-hydrothermal carbonization in step (2) is directly used as the carbon material to react with the terminal amino hyperbranched polymer, and the pH test, roasting and alkali solution soaking steps are not carried out.

[0067] Comparative Example 7

[0068] The difference from Example 1 is that the carbon material is directly mixed with acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid to form a mixed solution C.

[0069] Comparative Example 8

[0070] The difference from Example 1 is that in step (4), the terminal amino hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid are directly mixed evenly to form a mixed solution C, and the mixed solution C is polymerized into an adsorbent under a redox-azo composite system.

[0071] Comparative Example 9

[0072] The difference from Example 1 is that 2-acrylamido-2-methylpropanesulfonic acid in step (4) is replaced with 2-acrylamide.

[0073] Test Example 1

[0074] The carbon material prepared in Example 1 was subjected to SEM testing, and the carbon materials prepared in Example 1, Comparative Example 4, and Comparative Example 5 were subjected to elemental analysis and infrared spectroscopy analysis.

[0075] The SEM test results of the carbon material are shown inFigure 1 .

[0076] The elemental analysis results are shown in Table 1.

[0077] Table 1 Elemental analysis results of the carbon materials of Example 1, Comparative Example 4 and Comparative Example 5

[0078]

[0079]

[0080] As can be seen from Table 1, compared with the hydrothermal carbon obtained by co-hydrothermal carbonization with biomass, the hydrothermal carbon obtained by co-hydrothermal carbonization with biomass has a higher carbon content and a lower chlorine content than the pure biomass hydrothermal carbon and the pure PVC hydrothermal carbon. The dechlorination effect is remarkable. The presence of biomass significantly reduces the chlorine element content. After the chlorine element changes from the organic state to the inorganic state and enters the liquid phase, it can be effectively separated and recovered by solid-liquid separation, reducing the risk of its entry into the environment.

[0081] The infrared spectrum test results are shown in Figure 2 . From Figure 2 it can be seen that compared with the product of the hydrothermal carbonization of PVC alone (the carbon material of Comparative Example 4), the carbon material of Example 1 has a significantly reduced peak intensity at 2800 - 3000 cm -1 (stretching vibration of aliphatic C-H) because the walnut shell promotes the dechlorination of PVC and improves the aromaticity of PVC. Compared with the hydrothermal carbon of walnut shell (the carbon material of Comparative Example 5), the peak intensities at 1110 - 1000 cm -1 (C-O-C vibration of cellulose and hemicellulose) and 2800 - 3000 cm -1 (stretching vibration of aliphatic C-H) decrease because the hydrochloric acid released by the dechlorination of PVC during the co-hydrothermal process promotes the hydrolysis and carbonization of the walnut shell. In addition, absorption peaks of the stretching vibrations of -COOH and C=O appear at 1386 and 1701 cm -1 in the co-hydrothermal carbon. These characteristic peaks also exist in the infrared spectrum of the PVC hydrothermal carbon (the carbon material of Comparative Example 4). At the same time, the -OH peak at 3340 cm -1 becomes wider and blue-shifts to 3382 cm -1 , which all indicate that the co-hydrothermal carbon has more oxygen-containing functional groups and also shows that the co-hydrothermal carbonization successfully introduces the abundant carboxyl and hydroxyl groups generated during the hydrolysis of PVC onto the surface of the biomass hydrothermal carbon.

[0082] Test Example 2

[0083] The specific surface area of the carbon materials prepared in Example 1 and Comparative Example 3 was tested and analyzed, and the test results are shown in Table 2.

[0084] Table 2 Specific surface area test results of carbon materials prepared in Example 1, Comparative Example 3 and Comparative Example 6

[0085]

[0086] As can be seen from Table 2, during the co-hydrothermal carbonization process of PVC and biomass, the presence of biomass strengthened the dechlorination effect of PVC. The HCl generated by PVC dechlorination formed an acidic solution, enabling the synchronous impregnation of the hydrothermal carbonization solid product during the co-hydrothermal carbonization stage. Through subsequent operations such as selectively adjusting the solution pH value and impregnation time when necessary, in-situ activation, pore formation, and pore structure regulation of the co-hydrothermal carbonization solid product can be achieved through low-temperature heat treatment. This greatly promoted the development of the pore structure of the product, overcoming the shortcomings of underdeveloped pore structure and low specific surface area of the co-hydrothermal carbonization product, with a faster pollutant adsorption rate and better adsorption effect. Low-temperature heat treatment not only has low energy consumption but also can effectively avoid over-carbonization caused by high temperature, maximizing the retention of the number of oxygen-containing functional groups on the surface of the hydrothermal carbon. The oxygen-containing functional groups of the carbon material in Example 1 are higher than those in Comparative Example 3 and Comparative Example 6.

[0087] It can also be seen from Table 2 that although the specific surface area of Comparative Example 6 is very low, it already has a certain adsorption capacity for methylene blue and malachite green. Compared with the average saturated adsorption capacity of about 200 mg / g of methylene blue of commercially available activated carbon, it is only about 60% or so, but it is still much higher than the adsorption capacity of general biochar. This shows that the functional groups provided by PVC play an important role in the good adsorption capacity of the co-hydrothermal carbonization product. On this basis, through low-temperature activation, the pore structure of the co-hydrothermal carbon has achieved a breakthrough development, and there is no obvious loss of the functional groups on the surface of the adsorbent. The adsorption capacity of the product adsorbent for methylene blue and malachite green has increased several times, far exceeding that of commercially available activated carbon. This shows that the rich pore structure and surface oxygen-containing functional groups play a key role in enhancing the adsorption capacity of the adsorbent. By co-hydrothermal carbonizing PVC and biomass and combining low-temperature activation, the two can effectively promote each other, simultaneously obtaining a product with a developed pore structure and rich surface oxygen-containing functional groups. Through further alkali treatment to continue to increase the specific surface area and the content of oxygen-containing functional groups, an adsorbent with better adsorption performance can be obtained.

[0088] Test Example 3

[0089] The adsorption effects of Examples 1-2 and Comparative Examples 1-9 were tested.

[0090] (1) Simulation of dye wastewater and its standard curve

[0091] Dissolve the dye in water, and neutralize the solution to about pH 7 with sodium hydroxide solution and hydrochloric acid to prepare dye solutions with different concentrations;

[0092] Using deionized water as the reference solution, the absorbance of dye solutions at various concentrations was measured, and an ultraviolet absorption standard curve of dye concentration versus absorbance was plotted.

[0093] (2) Detection of dye adsorption performance

[0094] Take 25 mL of the dye solution in a conical flask, add 0.05 g of the adsorbent, adjust the initial pH of the dye solution to 3 - 5 with hydrochloric acid and sodium hydroxide solutions, then place the sealed conical flask in a magnetic stirrer and shake for 30 min, centrifuge, and take the supernatant. The dye concentration is 100 - 800 mg·L -1 , and measure its absorbance with a UV-visible spectrophotometer. The calculation formula for the dye adsorption capacity q is:

[0095]

[0096] where C0 and C e are the initial dye concentration and the dye adsorption equilibrium concentration respectively, V is the volume of the solution, and m is the mass of the adsorbent.

[0097] The dyes tested were methylene blue and malachite green, and the test results are shown in Table 3.

[0098] Table 3 Adsorption effects of Examples 1 - 2 and Comparative Examples 1 - 9

[0099]

[0100]

[0101] As can be seen from Table 3, in Comparative Example 1, waste PVC and biomass were directly calcined without co-hydrothermal carbonization and alkali solution activation. On the one hand, it is difficult to convert the organic chlorine on PVC into inorganic chlorine. On the other hand, it is difficult for the active groups on PVC to react onto the biochar, resulting in fewer active groups (such as hydroxyl groups and carboxyl groups) on the surface of the synthesized carbon material, which is not conducive to the subsequent reaction with the terminal amino hyperbranched polymer, and finally leads to a decrease in adsorption performance; in Comparative Example 2, the trifunctional amine compound in the present invention was replaced with a difunctional amine compound, and the adsorption effect decreased. This is because the degree of branching of the generated terminal amino hyperbranched polymer decreased, and a polymer material with more pores could not be formed on the surface of the carbon material, so the adsorption performance of the dye became worse; in Comparative Example 3, the carbon material was not soaked in the alkali solution, and both the specific surface area and the oxygen-containing functional groups decreased, resulting in insufficient reaction between the subsequent carbon material and the terminal amino hyperbranched polymer, and large pores and specific surface area could not be formed during the polymerization reaction, and the adsorption performance was insufficient; in Comparative Examples 4 and 5, carbon materials were prepared using only one of PVC and biomass. The carbon content of both was low, and using only PVC to prepare the carbon material would also result in a high chlorine content, causing pollution to the prepared adsorbent and being not environmentally friendly. The adsorption performance of the adsorbents prepared in Comparative Examples 4 and 5 also decreased compared with Example 1; in Comparative Example 6, the carbon material used was not calcined and activated with an alkali solution, making the carbon material not only have a small specific surface area but also few active groups, with both low adsorption capacity and few reactive groups. While the carbon material in Example 1 underwent a pore-forming and activation process, having the advantages of a high specific surface area and many reactive groups, and the subsequent reaction with the terminal amino hyperbranched polymer was more sufficient, which was more conducive to the further formation of a porous polymer on the surface of the carbon material; in Comparative Example 7, the terminal amino hyperbranched polymer was not added. The terminal amino hyperbranched polymer has a highly branched structure rather than a planar spatial structure, which can make there be a large number of pores between the carbon material molecules, increasing the contact area between the dye and the adsorbent. Comparative Example 7 did not use this branched structure, resulting in a decrease in adsorption performance; in Comparative Example 8, the carbon material was not added, and a porous polymer material was directly formed by polymerizing the terminal amino hyperbranched polymer with acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid. However, from the perspective of the adsorption effect, the adsorption effect decreased. This is because the carbon material not only provided a rich pore structure for adsorption but also gave the core for the subsequent polymerization reaction, which was conducive to the polymerization reaction to occur centered on the activated carbon, making the reaction more orderly and forming more pores; in Comparative Example 9, 2-acrylamido-2-methylpropanesulfonic acid containing a sulfonic acid group was replaced with 2-acrylamide without a sulfonic acid group, and the product generated by the reaction did not contain a sulfonic acid group. However, the sulfonic acid group belongs to an anionic group, and the dye has a positive charge in an aqueous solution. The sulfonic acid group is beneficial to the adsorption of the dye. The adsorbent in Example 1 uses a combination of physical adsorption and chemical adsorption to have a relatively excellent adsorption effect on the dye.

[0102] Therefore, the present invention adopts the preparation method of a functionalized highly adsorbent adsorbent with the above structure. Using PVC waste and biomass solid waste as raw materials, an adsorbent containing rich functional groups is prepared by means of co-hydrothermal carbonization, low-temperature self-activation process and surface construction of porous polymers. The preparation process is simple, with low cost, wide raw material sources, and is easy to promote. It has extremely excellent adsorption performance for typical dyes such as methylene blue and malachite green.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a functionalized highly adsorbent adsorbent, characterized in that: It includes the following steps: (1) Preparation of amino-terminated hyperbranched polymer Mix anhydrous ethanol and amine compound evenly, stir well under nitrogen protection to form a mixed solution A, and then slowly drop the above mixed solution A into a mixed solution B formed by acrylate compound and anhydrous methanol for reaction. After the reaction, amino-terminated hyperbranched polymer is obtained; (2) Preparation of carbon material Use waste biomass and waste polyvinyl chloride as raw materials, add water and mix them, then add them to a reaction kettle for co-hydrothermal carbonization to obtain a solid-liquid mixture. Perform solid-liquid separation on the solid-liquid mixture, place the solid part in a heating furnace with a protective atmosphere for roasting to obtain a solid product. Immerse the solid product in an alkaline solution for a period of time and then perform solid-liquid separation again. Wash it with water until neutral and then dry it to obtain carbon material; (3) Preparation of amino-terminated hyperbranched polymer grafted carbon material Disperse the carbon material in distilled water by ultrasonic wave to obtain a suspension, and then add the amino-terminated hyperbranched polymer to the above suspension and continue ultrasonic dispersion to obtain a uniform mixture. Stir at 80-90 °C for 12 hours. After the reaction, amino-terminated hyperbranched polymer grafted carbon material is obtained; (4) Preparation of adsorbent Mix the amino-terminated hyperbranched polymer grafted carbon material, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid evenly to form a mixed solution C. The mixed solution C is polymerized under a redox-azo composite system to form an adsorbent.

2. The preparation method of a functionalized highly adsorbent adsorbent according to claim 1, characterized in that: In step (1), the volume ratio of amine compound to anhydrous ethanol is 1:1, the volume ratio of acrylate compound to anhydrous ethanol is 1:1, and the mass ratio of amine compound to acrylate compound is 1:

1. During the reaction, place the product under reduced pressure distillation at 60 °C for 2 hours, and then react at 120 °C for 7 hours to obtain amino-terminated hyperbranched polymer.

3. The preparation method of a functionalized highly adsorbent adsorbent according to claim 2, characterized in that: The amine compound in step (1) is one or more of tris(3-aminopropyl)amine, 1,2,4-triaminobenzene, and 1,3,5-triaminocyclohexane.

4. The preparation method of a functionalized highly adsorbent adsorbent according to claim 1, characterized in that: In step (2), the waste biomass is one or more of waste fruit shells, peels, plant straws, livestock and poultry manure, municipal sludge, paper, garden waste, and wood chips; the waste polyvinyl chloride is one or more of waste plastics, electronic product casings, and printed circuit boards; the mass ratio of the waste polyvinyl chloride to the waste biomass is 1-5:1-20, and the particle size range of the raw materials is 0.5 mm-5 mm.

5. The preparation method of a functionalized highly adsorbent adsorbent according to claim 1, characterized in that: Perform a pH test on the solid-liquid mixture obtained in step (2), perform selective dilution treatment on the solid-liquid mixture according to the pH value and let it stand for a period of time. The pH range before and after selective dilution is 0-7, the solvent used for dilution is deionized water or tap water, and the standing time after dilution is 0-72 hours; the alkaline solution used for soaking is a solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, or ammonia water, and the concentration range is 5-200 g / L.

6. The preparation method of a functionalized highly adsorbent adsorbent according to claim 1, characterized in that: In step (2), the temperature of the hydrothermal carbonization reaction is 160°C - 350°C, the reaction time of the hydrothermal carbonization reaction is 1 - 48 h, the pressure of the hydrothermal reaction is 2 - 15 MPa, the solid-liquid mass ratio is 1:5 - 1:100, and the hydrothermal solvent is deionized water or tap water; the protective atmosphere in the heating furnace is an inert gas, the heating rate is 1 - 40°C / min, the heat preservation temperature is 250 - 450°C, and the heat preservation time is 5 - 180 min; the drying temperature range is 60 - 100°C, and the drying time is 30 - 180 min.

7. The preparation method of a functionalized highly adsorbent adsorbent according to claim 1, characterized in that: In step (3), the mass fraction of the suspension is 5 - 8 wt%, and the mass ratio of the amino-terminated hyperbranched polymer to the carbon material is 1:100 - 150.

8. The preparation method of a functionalized highly adsorbent adsorbent according to claim 1, characterized in that: In step (4), the weight parts of the carbon material grafted with the amino-terminated hyperbranched polymer, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and acrylic acid added are 50 - 100 parts, 50 - 100 parts, 20 - 40 parts, and 60 - 80 parts, respectively.

9. The preparation method of a functionalized highly adsorbent adsorbent according to claim 8, characterized in that: The redox-azo composite system is a system composed of 0.3 - 0.5 parts of azo salt, 0.001 - 0.002 parts of tert-butyl peroxide, and 0.005 - 0.01 parts of ammonium ferrous sulfate.

10. The preparation method of a functionalized highly adsorbent adsorbent according to claim 9, characterized in that: The azo salt is one or two of azodiisooctanenitrile, azodiethylcyanovaleric acid, and azo V044, and the tert-butyl peroxide is tert-butyl hydroperoxide.

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