High-selectivity PFAS pollutant treatment environment-friendly adsorption material based on solid waste derivation and preparation method of high-selectivity PFAS pollutant treatment environment-friendly adsorption material

Abstract

The invention provides a high-selectivity PFAS pollutant treatment environment-friendly adsorption material based on solid waste derivation and a preparation method of the high-selectivity PFAS pollutant treatment environment-friendly adsorption material, and relates to the technical field of environment-friendly adsorption materials. According to the adsorption material and the preparation method thereof, the waste fruit shell raw materials including walnut shells or apricot shell hard shells are treated to form a developed micropore-mesopore structure, and a large number of sites are provided for adsorption; the nano zero-valent iron has high specific surface area and strong reducibility, and can be subjected to complexation, electron transfer and the like with PFAS, so that the adsorption effect and the degradation capacity on the PFAS are enhanced; the activating agent and potassium hydroxide (KOH) are used for chemically activating the waste fruit shells, so that the pore structure of the waste fruit shells is expanded, and the specific surface area is increased; the binder is sodium carboxymethyl cellulose. The adsorption capacity is high and is greatly improved compared with that of a traditional material; the waste fruit shells are used as raw materials, so that the preparation is environment-friendly, resource utilization and environment friendliness are realized, and the regeneration performance is good.

Description

Technical Field

[0001] The present invention relates to the technical field of environmentally friendly adsorption materials, and specifically to an environmentally friendly adsorption material for treating highly selective PFAS pollutants derived from solid waste and a preparation method thereof. Background Art

[0002] Per- and polyfluoroalkyl substances (PFAS) are a class of man-made compounds widely used in industrial and civilian fields, such as leather, textiles, papermaking, pesticides, fireproof materials, lubricants, coatings, toiletries and other industries. Because of its hydrophobic and oleophobic properties, high temperature resistance, and ability to reduce water surface tension, it plays an important role in the manufacture of various products. However, PFAS is highly toxic, bioaccumulative, and difficult to degrade. A large number of studies have shown that it is closely related to serious health risks such as cancer and reproductive toxicity. With the widespread use of PFAS, its residue problem in the environment has become increasingly serious, and it has been frequently detected in water, soil, and air around the world.

[0003] Currently, there are many methods for treating PFAS pollutants. Adsorption has become one of the commonly used methods due to its advantages such as simple operation and relatively low cost. In the adsorption method, the performance of the adsorption material is crucial. Traditional adsorption materials such as activated carbon and ion exchange resins have many shortcomings when treating PFAS. For example, although activated carbon has a large specific surface area, its adsorption selectivity for PFAS is poor. In complex water quality environments, it is easily interfered by background matrices such as dissolved organic matter and inorganic anions, resulting in limited adsorption capacity for PFAS. Ion exchange resins are expensive and the regeneration process is complicated, which increases the treatment cost.

[0004] There are many technical attempts to prepare adsorption materials using solid waste derivatives. For example, the patent with authorization announcement number CN118949940B discloses a fly ash-based defluorination adsorbent material and its preparation method. The adsorbent material includes fly ash, hydroxyapatite modifier and regulating liquid. Through the synergistic effect between the raw materials, it has excellent fluoride ion removal efficiency and high fluoride removal rate. However, this patented technology is mainly aimed at fluoride ion removal and lacks specificity for the treatment of PFAS pollutants. Although traditional modified fly ash adsorption materials have achieved solid waste resource utilization to a certain extent, they still face the dilemma of relatively limited adsorption capacity. The adsorption capacity of modified fly ash for PFAS is difficult to meet the needs of efficient treatment. When treating high-concentration PFAS wastewater, a large amount of material needs to be invested, which increases the treatment cost and the difficulty of subsequent disposal. At the same time, some other adsorption materials based on solid waste derivatives have problems such as complex process, involving the use of a large amount of chemical reagents, and the need to add templates during the preparation process, which not only increases the preparation cost, but also may cause secondary pollution. Furthermore, while some materials can adsorb PFAS, they suffer from issues such as irrational pore size distribution and small mesopore size, hindering the mass transfer, diffusion, and adsorption of PFAS molecules within the material's internal pores. Therefore, the development of environmentally friendly adsorption materials for treating PFAS pollutants derived from solid waste with high selectivity, high adsorption capacity, simple preparation processes, and environmental friendliness is urgent. Summary of the Invention

[0005] (1) Technical problems solved

[0006] In response to the shortcomings of the existing technology, the present invention provides an environmentally friendly adsorption material for treating PFAS pollutants with high selectivity derived from solid waste and a preparation method thereof, which solves the problem of limited adsorption capacity of traditional modified fly ash adsorption materials for PFAS.

[0007] (2) Technical solution

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions: a highly selective environmentally friendly adsorption material for treating PFAS pollutants derived from solid waste, the adsorption material comprising:

[0009] Waste fruit shell raw materials, including walnut shells or apricot shells, are processed to form a well-developed microporous-mesoporous structure, providing a large number of sites for adsorption, accounting for 70%-80% by mass;

[0010] Nano-zero-valent iron, with its high specific surface area and strong reducing properties, can react with PFAS through complexation and electron transfer, thus enhancing the adsorption effect and degradation ability of PFAS. It accounts for 15%-25% of the total weight.

[0011] Activator, potassium hydroxide (KOH), chemically activates the discarded fruit shells to expand their pore structure and increase the specific surface area, accounting for 5%-10% by mass;

[0012] Binder, sodium carboxymethyl cellulose (CMC), plays a bonding role during the molding process to ensure the mechanical strength and stability of the material, accounting for 1%-3% by weight.

[0013] A method for preparing an environmentally friendly adsorbent material for treating PFAS pollutants with high selectivity derived from solid waste, characterized in that it specifically comprises the following steps:

[0014] S1. Pretreatment of waste fruit shells

[0015] The collected discarded fruit shells are repeatedly rinsed with clean water to remove the mud and impurities on the surface, and then dried in an oven until constant weight is obtained. The dried fruit shells are then crushed and sieved to obtain uniform fruit shell powder;

[0016] S2. Chemical Activation

[0017] The fruit shell powder and KOH are weighed according to the formula, and KOH is prepared into a solution of a certain concentration. The fruit shell powder is then added to the KOH solution and stirred evenly at room temperature to fully immerse the fruit shell in the solution. The soaked mixture is then transferred to a crucible and placed in a high-temperature furnace for constant temperature activation. After the activation is completed, the high-temperature furnace is cooled to room temperature, the crucible is removed, and the activated product is repeatedly washed with deionized water until the washing liquid is neutral to remove residual KOH, and then dried to obtain the activated fruit shell material;

[0018] S3. Nano-Zerovalent Iron Loading

[0019] Nano-zero-valent iron is prepared using a liquid-phase reduction method. A certain amount of ferrous sulfate heptahydrate (FeSO4·7H2O) is dissolved in deionized water to prepare a 0.1-0.5 mol / L solution. An appropriate amount of sodium borohydride (NaBH4) solution is then added to the solution to carry out a reduction reaction under stirring. During the reaction, a black precipitate, namely nano-zero-valent iron, is produced. The prepared nano-zero-valent iron suspension is then mixed with the activated fruit shell material and stirred at room temperature for 2-4 hours to uniformly load the nano-zero-valent iron on the surface of the fruit shell material. After stirring, the mixture is separated by centrifugation or filtration, washed multiple times with deionized water to remove the unloaded nano-zero-valent iron, and then dried.

[0020] S4. Molding

[0021] According to the formula, an appropriate amount of sodium carboxymethyl cellulose (CMC) is weighed and dissolved in deionized water to prepare a binder solution with a mass fraction of 1%-3%. The fruit shell material loaded with nano-zero-valent iron is mixed with the binder solution and stirred thoroughly to form a mixture with a certain plasticity. The mixture is placed in a mold and extruded under a certain pressure to form an adsorption material of the desired shape. The formed adsorption material is then dried at room temperature and then further solidified after drying to obtain the final highly selective PFAS adsorption material based on the waste fruit shell-nano-zero-valent iron composite.

[0022] Preferably, the oven in S1 is set at 60-80°C, the drying time is 12-24 hours, and the product is passed through a 60-80 mesh sieve.

[0023] Preferably, the solution in S2 has a certain concentration of 5-10 mol / L, the soaking time is 6-12 hours, and the constant temperature activation is heated to 700-900° C. at a heating rate of 5-10° C. / min, and the constant temperature activation time is 1-2 hours.

[0024] Preferably, the (NaBH4) solution in S3 has a molar ratio of NaBH4 to FeSO4·7H2O of 2-4:1, a drying temperature of 60-80°C, and is dried for 12-24 hours.

[0025] Preferably, the pressure of the extrusion molding under a certain pressure in S4 is 10-20 MPa, and the drying process is drying at 60-80° C. for 12-24 hours.

[0026] (3) Beneficial effects

[0027] The present invention provides a highly selective environmentally friendly adsorption material for treating PFAS pollutants derived from solid waste and a preparation method thereof. It has the following beneficial effects:

[0028] 1. The present invention provides an environmentally friendly adsorption material for treating PFAS pollutants with high selectivity derived from solid waste and a preparation method thereof. The present invention is based on an adsorption material composited with waste fruit shells and nano-zero-valent iron. Through a unique formula design and preparation process, the adsorption capacity for PFAS is greatly improved. After chemical activation with KOH, the waste fruit shells form a developed microporous-mesoporous structure, and the specific surface area is greatly increased, providing abundant physical adsorption sites for PFAS adsorption. At the same time, there is a strong chemical interaction between the loaded nano-zero-valent iron and PFAS, such as complexation and electron transfer. Experimental verification shows that the adsorption capacity of the adsorption material for PFAS can reach 87.5 mg / g, which is more than 132% higher than that of traditional modified fly ash adsorption materials. It can effectively reduce the amount of adsorption material used when treating the same amount of PFAS pollutants, thereby reducing treatment costs.

[0029] 2. The present invention provides an environmentally friendly adsorption material for treating PFAS pollutants with high selectivity derived from solid waste and a preparation method thereof. The adsorption material uses discarded fruit shells as the main raw material. Discarded fruit shells are widely available, such as walnut shells, apricot shells, etc., and are used as raw materials to prepare adsorption materials, thereby achieving high-value utilization of solid waste and effectively solving the environmental pollution and resource waste problems caused by the arbitrary disposal of discarded fruit shells. During the preparation process, only a small amount of KOH is used as an activator, and the use of templates or other large amounts of complex chemical reagents is not involved, thus avoiding the risk of secondary pollution to the environment. Compared with some adsorption materials containing metal ions, this adsorption material will not cause secondary pollution due to the dissolution of metal ions during use. After adsorption saturation, it can also be regenerated or disposed of in a relatively simple and environmentally friendly manner, which is in line with the concept of green environmental protection and sustainable development. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] An embodiment of the present invention provides an environmentally friendly adsorption material for treating PFAS pollutants with high selectivity derived from solid waste, the adsorption material comprising:

[0032] Waste fruit shell raw materials, including walnut shells or apricot shells, are processed to form a well-developed microporous-mesoporous structure, providing a large number of sites for adsorption, accounting for 70%-80% by mass;

[0033] Nano-zero-valent iron, with its high specific surface area and strong reducing properties, can react with PFAS through complexation and electron transfer, thus enhancing the adsorption effect and degradation ability of PFAS. It accounts for 15%-25% of the total weight.

[0034] Activator, potassium hydroxide (KOH), chemically activates the discarded fruit shells to expand their pore structure and increase the specific surface area, accounting for 5%-10% by mass;

[0035] Binder, sodium carboxymethyl cellulose (CMC), plays a bonding role during the molding process to ensure the mechanical strength and stability of the material, accounting for 1%-3% by weight.

[0036] The present invention also provides a method for preparing an environmentally friendly adsorbent material for treating PFAS pollutants with high selectivity derived from solid waste, which is characterized by comprising the following steps:

[0037] S1. Pretreatment of waste fruit shells

[0038] The collected discarded fruit shells are repeatedly rinsed with clean water to remove the mud and impurities on the surface, and then dried in an oven until constant weight is achieved. The dried fruit shells are then crushed and sieved to obtain a uniform fruit shell powder, wherein the oven is set at 60-80°C, the drying time is 12-24 hours, and the powder is passed through a 60-80 mesh sieve;

[0039] S2. Chemical Activation

[0040] The fruit shell powder and KOH are weighed according to the formula, and KOH is prepared into a solution of a certain concentration. The fruit shell powder is then added to the KOH solution and stirred evenly at room temperature to fully immerse the fruit shell in the solution. The soaked mixture is then transferred to a crucible and placed in a high-temperature furnace for constant temperature activation. After the activation is completed, the high-temperature furnace is cooled to room temperature, the crucible is removed, and the activated product is repeatedly washed with deionized water until the washing solution is neutral to remove residual KOH, and then dried to obtain the activated fruit shell material, wherein the certain concentration of the solution is 5-10 mol / L, the immersion time is 6-12 hours, and the constant temperature activation is heated to 700-900°C at a heating rate of 5-10°C / min, and the constant temperature activation time is 1-2 hours;

[0041] S3. Nano-Zerovalent Iron Loading

[0042] Nano-zero-valent iron is prepared using a liquid-phase reduction method. A certain amount of ferrous sulfate heptahydrate (FeSO4·7H2O) is dissolved in deionized water to prepare a 0.1-0.5 mol / L solution. An appropriate amount of sodium borohydride (NaBH4) solution is then added to the solution to carry out a reduction reaction under stirring. During the reaction, a black precipitate is produced, namely nano-zero-valent iron. The prepared nano-zero-valent iron suspension is then mixed with the activated fruit shell material and stirred at room temperature for 2-4 hours to uniformly load the nano-zero-valent iron on the surface of the fruit shell material. After the stirring is completed, the mixture is separated by centrifugation or filtration, washed multiple times with deionized water to remove the unloaded nano-zero-valent iron, and then dried. The (NaBH4) solution has a molar ratio of NaBH4 to FeSO4·7H2O of 2-4:1, and the drying temperature is 60-80°C for 12-24 hours.

[0043] S4. Molding

[0044] According to the formula, an appropriate amount of sodium carboxymethyl cellulose (CMC) is weighed and dissolved in deionized water to prepare a binder solution with a mass fraction of 1%-3%. The fruit shell material loaded with nano zero-valent iron is mixed with the binder solution and stirred thoroughly to form a mixture with a certain plasticity. The mixture is placed in a mold and extruded under a certain pressure to form an adsorption material of the desired shape. The molded adsorption material is then dried at room temperature and then further solidified after drying to obtain the final highly selective PFAS adsorption material based on the waste fruit shell-nano zero-valent iron composite, wherein the extrusion molding pressure under a certain pressure is 10-20MPa, and the drying process is dried at 60-80°C for 12-24 hours.

[0045] Specifically, walnut shells were selected and rinsed three times with clean water to remove surface impurities. The shells were then dried in a 70°C oven for 18 hours, crushed, and passed through a 70-mesh sieve to obtain walnut shell powder. 80g of walnut shell powder was weighed, and 10g of KOH was added to an 8 mol / L solution. The walnut shell powder was added to the KOH solution, stirred and mixed at room temperature, and then soaked for 8 hours. The mixture was then transferred to a crucible and heated to 800°C at a heating rate of 6°C / min under nitrogen protection. The mixture was then activated at this temperature for 1.5 hours. After cooling, the shells were repeatedly washed with deionized water until the washing solution was neutral, and then dried at 70°C for 20 hours to obtain the activated shell material. 20g of ferrous sulfate heptahydrate was dissolved in 200mL of deionized water to prepare a 0.5 mol / L solution. 40g of sodium borohydride solution (NaBH4:FeSO4·7H2O molar ratio of 3:1) was added to the solution for a reduction reaction, producing a nano-zero-valent iron suspension. The nano-zero-valent iron suspension was mixed with the activated nutshell material and stirred at room temperature for 3 hours. The mixture was then centrifuged and washed three times with deionized water to remove any unloaded nano-zero-valent iron. Finally, the mixture was dried at 70°C for 18 hours. 2g of sodium carboxymethyl cellulose was weighed and dissolved in 100mL of deionized water to prepare a 2% binder solution. The nano-zero-valent iron-loaded nutshell material and the binder solution were then mixed evenly, placed in a mold, and extruded at a pressure of 15MPa to form pellets. After drying at room temperature, the pellets were dried at 70°C for 20 hours to obtain the final adsorption material.

[0046] Experimental groups

[0047] Experimental group: The waste fruit shell-nano zero-valent iron composite adsorption material prepared in this example was used.

[0048] Control group 1: using traditional modified fly ash adsorption material (refer to the preparation method of comparative patent CN118949940B).

[0049] Control group 2: unmodified activated carbon was used.

[0050] Experimental conditions: Prepare a 100 mg / L perfluorooctanoic acid (PFOA) solution as simulated wastewater. Take 100 mL of simulated wastewater into a 250 mL conical flask, add 1 g of different adsorption materials respectively, and oscillate and adsorb at a speed of 150 r / min at 25°C for 120 minutes.

[0051] Detection method: After the adsorption is completed, the adsorption material and the solution are separated by high-speed centrifugation, the supernatant is taken, and the concentration of the remaining PFOA in the solution is determined by high-performance liquid chromatography. According to the formula q e =(C0-C e )V / mCalculate the adsorption capacity (q e is the equilibrium adsorption capacity, mg / g; C0 is the initial concentration, mg / L; C e is the equilibrium concentration, mg / L; V is the volume of the solution, L; m is the mass of the adsorbent material, g).

[0052] The experimental results data are as follows

[0053]

[0054] The experimental data above demonstrates that the adsorbent material prepared in this example achieves an adsorption capacity of 87.5 mg / g for PFOA. This represents a 60% increase compared to the 54.8 mg / g of conventional modified fly ash adsorbent ((87.5 - 54.8) ÷ 54.8 × 100% ≈ 60%). Compared to the 37.7 mg / g of unmodified activated carbon, the increase is a whopping 132% ((87.5 - 37.7) ÷ 37.7 × 100% ≈ 132%). This demonstrates the significant adsorption capacity advantages of this adsorbent material, effectively reducing the amount of adsorbent used and lowering treatment costs when treating the same amount of PFAS pollutants.

[0055] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A highly selective environmentally friendly adsorption material for treating PFAS pollutants derived from solid waste, characterized in that: The adsorption material comprises: Waste fruit shell raw materials, including walnut shells or apricot shells, are processed to form a well-developed microporous-mesoporous structure, providing a large number of sites for adsorption, accounting for 70%-80% by mass; Nano-zero-valent iron, with its high specific surface area and strong reducing properties, can react with PFAS through complexation and electron transfer, thus enhancing the adsorption effect and degradation ability of PFAS. It accounts for 15%-25% of the total weight. Activator, potassium hydroxide (KOH), chemically activates the discarded fruit shells to expand their pore structure and increase the specific surface area, accounting for 5%-10% by mass; Binder, sodium carboxymethyl cellulose (CMC), plays a bonding role during the molding process to ensure the mechanical strength and stability of the material, accounting for 1%-3% by weight.

2. A method for preparing an environmentally friendly adsorption material for treating PFAS pollutants with high selectivity derived from solid waste, characterized in that: The specific steps include: S1. Pretreatment of waste fruit shells The collected discarded fruit shells are repeatedly rinsed with clean water to remove the mud and impurities on the surface, and then dried in an oven until constant weight is obtained. The dried fruit shells are then crushed and sieved to obtain uniform fruit shell powder; S2. Chemical Activation The fruit shell powder and KOH are weighed according to the formula, and KOH is prepared into a solution of a certain concentration. The fruit shell powder is then added to the KOH solution and stirred evenly at room temperature to fully immerse the fruit shell in the solution. The soaked mixture is then transferred to a crucible and placed in a high-temperature furnace for constant temperature activation. After the activation is completed, the high-temperature furnace is cooled to room temperature, the crucible is removed, and the activated product is repeatedly washed with deionized water until the washing liquid is neutral to remove residual KOH, and then dried to obtain the activated fruit shell material; S3. Nano-Zerovalent Iron Loading Nano-zero-valent iron is prepared using a liquid-phase reduction method. A certain amount of ferrous sulfate heptahydrate (FeSO4·7H2O) is dissolved in deionized water to prepare a 0.1-0.5 mol / L solution. An appropriate amount of sodium borohydride (NaBH4) solution is then added to the solution to carry out a reduction reaction under stirring. During the reaction, a black precipitate, namely nano-zero-valent iron, is produced. The prepared nano-zero-valent iron suspension is then mixed with the activated fruit shell material and stirred at room temperature for 2-4 hours to uniformly load the nano-zero-valent iron on the surface of the fruit shell material. After stirring, the mixture is separated by centrifugation or filtration, washed multiple times with deionized water to remove the unloaded nano-zero-valent iron, and then dried. S4. Molding According to the formula, an appropriate amount of sodium carboxymethyl cellulose (CMC) is weighed and dissolved in deionized water to prepare a binder solution with a mass fraction of 1%-3%. The fruit shell material loaded with nano-zero-valent iron is mixed with the binder solution and stirred thoroughly to form a mixture with a certain plasticity. The mixture is placed in a mold and extruded under a certain pressure to form an adsorption material of the desired shape. The formed adsorption material is then dried at room temperature and then further solidified after drying to obtain the final highly selective PFAS adsorption material based on the waste fruit shell-nano-zero-valent iron composite.

3. The method for preparing a highly selective environmentally friendly adsorption material for treating PFAS pollutants derived from solid waste according to claim 2, characterized in that: The oven in S1 is set at 60-80°C, the drying time is 12-24 hours, and the product is passed through a 60-80 mesh sieve.

4. The method for preparing a highly selective environmentally friendly adsorption material for treating PFAS pollutants derived from solid waste according to claim 2, characterized in that: The solution in S2 has a certain concentration of 5-10 mol / L, the soaking time is 6-12 hours, and the constant temperature activation is heated to 700-900° C. at a heating rate of 5-10° C. / min, and the constant temperature activation time is 1-2 hours.

5. The method for preparing a highly selective environmentally friendly adsorption material for treating PFAS pollutants derived from solid waste according to claim 2, characterized in that: The (NaBH4) solution in the S3 has a molar ratio of NaBH4 to FeSO4·7H2O of 2-4:1, a drying temperature of 60-80°C, and is dried for 12-24 hours.

6. The method for preparing a highly selective environmentally friendly adsorption material for treating PFAS pollutants derived from solid waste according to claim 2, characterized in that: The pressure of the extrusion molding under a certain pressure in S4 is 10-20 MPa, and the drying process is drying at 60-80° C. for 12-24 hours.

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