Preparation method and application of bio-based composite environment-friendly adsorbent

Abstract

The invention relates to a preparation method and application of a bio-based composite environment-friendly adsorbent, and belongs to the technical fields of biomass waste recycling, composite materials thereof, wastewater treatment and the like. The main raw material for preparing the adsorbent is derived from waste sugar filter mud in the sugar manufacturing process, and after low-energy activation treatment is conducted on the waste sugar filter mud, high-activity isocyanate and amine monomers are adopted on the surface of the waste sugar filter mud to conduct in-situ polymerization to generate polyurea; the preparation method does not need complex equipment and expensive reagents, is simple in process, low in reaction energy consumption and suitable for large-scale industrial production, and opens up a new path for the development of circulating biological economy; according to the prepared adsorbent, after five continuous adsorption-desorption cycles, the removal rate of Cd (II) and Pb (II) is still kept at 85% or above, and the decolorization rate of methyl orange dye is 96% or above, so that the adsorbent has high-efficiency treatment capacity on a heavy metal and dye pollution system, and a technical scheme with extremely high competitiveness is provided for deep treatment of industrial wastewater and environmental ecological restoration.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a bio-based composite environmentally friendly adsorbent, and specifically to a preparation method and application of a beet sugar filter mud and polyurea composite adsorbent, belonging to the technical fields of biomass waste recycling, bio-based composite materials, polymers and wastewater treatment, etc. Background Art

[0002] Sugar beet (Beta vulgaris L.) is one of China's major sugar crops and the second-largest globally, accounting for 30% of the world's sugar supply. Compared to sugarcane, sugar beet cultivation is simpler, more mechanized, less expensive, and offers significant returns. In 2022, China's sugar beet planting area reached 184,670 hectares. In 2019, the global sugar beet harvest totaled 314 million tons, with my country producing 12.2729 million tons. Sugar beet production requires clarification. Currently, many sugar beet factories use the carbonation process, which adds large amounts of lime and carbon dioxide to the beet juice to produce calcium carbonate precipitation, which absorbs and removes impurities from the juice, ultimately producing a clear liquid. The precipitated mixture is referred to as carbonation mill sludge (hereinafter referred to as sugar sludge). This process produces high-purity, low-impregnation, and high-quality white sugar.

[0003] The sugar production process suffers from high lime consumption and high filter mud production. Producing 10,000 tons of sugar from sugar beets generates approximately 5,000 tons of filter mud waste [Chinese Patent, Application No. 2022102865833]. Filter mud is rich in calcium carbonate and a small amount of organic matter, with a pH of approximately 9.0. Currently, trenching and landfilling or direct return to the field are still methods of disposal. Trenching and landfilling not only occupies land, but also pollutes water bodies through leachate, wasting resources. Direct return to the field exacerbates soil alkalinization and hinders crop growth. Therefore, developing efficient, cost-effective, and easy-to-use technologies for high-value-added filter mud applications is of great significance.

[0004] Meanwhile, industrial sectors like petrochemicals, mining, electroplating, and manufacturing often generate wastewater containing heavy metal ions like lead and cadmium during production processes. These heavy metals are highly stable, soluble, difficult to degrade, bioaccumulate, and are carcinogenic, posing a serious threat to the environment and human health. They have been identified as endocrine disruptors, damaging vital organs like the brain, nervous system, kidneys, lungs, liver, and bones. The International Agency for Research on Cancer (IARC) also lists blood lead concentrations exceeding 10 μg / dL as a potential carcinogen. Cadmium is classified as a Group 1 carcinogen and can cause gout and serious kidney, bone, and respiratory diseases.

[0005] When addressing the challenge of removing pollutants such as heavy metals and dyes from wastewater, existing solutions often rely on chemical synthesis techniques, such as hydrogel polymers, chitosan-based adsorbents, iron oxide nanoparticles, and graphene. While these methods hold promise, they are expensive and complex. In contrast, innovative methods for preparing heavy metal ion and dye adsorbents from industrial waste not only inject new vitality into green chemistry but also transform waste into valuable resources, disrupting traditional production models and paving new paths for the development of a circular bioeconomy.

[0006] Polyurea is a polymer formed by the polymerization of isocyanates and amino compounds, boasting a unique molecular structure and excellent overall properties. Its rapid reaction speed allows it to adapt to complex construction surfaces (such as concrete, metal, and foam). It also boasts strong adhesion, exceptional weather resistance, resistance to acids and alkalis, chemical corrosion, impact resistance, and abrasion resistance. It can be sprayed, brushed, or poured, flexibly adapting to diverse needs. The polyurea layer's inherent properties undoubtedly protect against mechanical wear during the adsorption and desorption cycles of sugar filter mud particles, effectively preventing deformation and dissolution under fluid erosion, thereby extending the material's service life. Summary of the Invention

[0007] One of the technical tasks of the present invention is to make up for the shortcomings of the existing technology and provide a method for preparing a low-processing sugar filter mud and polyurea bio-based composite environmentally friendly adsorbent. The method has low raw material cost, simple preparation process, low reaction energy consumption, and has industrial application prospects.

[0008] The second technical task of the present invention is to provide the use of the bio-based composite environmentally friendly adsorbent, that is, to use the material for the efficient adsorption and separation of heavy metal ions and dyes.

[0009] The technical solutions of the present invention are as follows: 1. A method for preparing a bio-based composite environmentally friendly adsorbent, the preparation steps are as follows: (1) Activation treatment of sugar filter mud The sugar filter mud is washed with water and filtered, and the process is repeated several times until no soluble matter is dissolved. The sugar filter mud is dried at 120°C in a vacuum until constant weight is reached, cooled to room temperature, crushed, and passed through a 70-mesh sieve to obtain sugar filter mud powder. (2) Chemical cross-linking of sugar filter mud surface Take 1 kg of sugar filter mud powder, spray add 103-110 g of N, N'-diethyl-1,3-propylenediamine containing 4-5 g of catalyst and 7-8 g of water under stirring, stir at room temperature for 10 minutes, continue to spray add 210-230 g of isocyanate PM-200, continue stirring for 60 minutes, stop stirring, age at 60 ° C for 3 hours, and cool to room temperature to obtain a sugar filter mud / polyurea composite material, that is, a composite material with chemical cross-linking on the surface of the sugar filter mud, that is, a bio-based composite environmentally friendly adsorbent.

[0010] The sugar filter mud in the above step (1) is a precipitated mixture obtained by removing impurities from beet juice by carbonation adsorption in a beet sugar factory.

[0011] The vacuum drying at 120°C in the above step (1) has a vacuum absolute pressure of 10-100 Pa.

[0012] The catalyst in the above step (2) is a diethylene glycol solution of ethylenediamine with a mass fraction of 33%.

[0013] The above-mentioned isocyanate PM-200 is produced by Wanhua Chemical Group Co., Ltd. Its mass content of isocyanate -NCO is 30.5-32.0%. It is a mixture of higher-functionality isocyanate and diphenylmethane diisocyanate. It is a brown liquid at room temperature, with a viscosity of 150-250mPa•s at 25℃ and a density of 1.22-1.25g / cm3 at 25℃.

[0014] The bio-based composite environmentally friendly adsorbent prepared by the above preparation method is used to remove heavy metal ions and organic dye pollutants in wastewater, and the steps are as follows: (1) Removal of heavy metal ions from wastewater 1) Adsorption experiment: In a conical flask, add 100 mL of simulated metal ion wastewater solution with a pH of 6-8, and then add 0.50 g of the bio-based composite environmentally friendly adsorbent prepared above. Adsorb for 2 h at 30°C and a vibration frequency of 150 osc / min. After centrifugation, collect the supernatant and detect the remaining metal ion concentration. 2) Desorption experiment: Add 100 mL of 0.1 mol / L HCl solution to a conical flask, followed by 0.5 g of a dried bio-based composite environmentally friendly adsorbent that has been adsorbed with metal ions. Desorb the metal ions at 30°C and a vibration frequency of 150 osc / min for 4 h. After centrifugation, collect the supernatant and measure the concentration of the desorbed metal ions. 3) Cyclic Adsorption Experiment: 100 mL of 0.1 mol / L HCl solution was added to a conical flask, followed by 0.5 g of a dried bio-based composite environmentally friendly adsorbent that had adsorbed metal ions. Desorption was carried out at 30°C and a vibration frequency of 150 osc / min for 4 hours to effectively desorb the adsorbed metal ions. The adsorbent was then filtered and washed with water three or more times. After drying under vacuum at 120°C to constant weight, it was used in subsequent adsorption experiments to evaluate the reusability of the bio-based composite environmentally friendly adsorbent. 4) Removal of heavy metal ions from wastewater using actual wastewater samples In a conical flask, add 100 mL of metal ion wastewater solution, and then add 0.50 g of the bio-based composite environmentally friendly adsorbent prepared above. Adsorb for 2 h at 30 ° C and a vibration frequency of 150 osc / min. After centrifugation, take the supernatant to detect the remaining metal ion concentration; The above-mentioned detection adopts flame atomic absorption spectrophotometer; The results showed that the bio-based composite environmentally friendly adsorbent has good reusability potential. Over five cycles, the removal efficiency of Pb(II) decreased from 98.3% to 87.9%, and the removal efficiency of Cd(II) decreased from 98.9% to 97.3%. This indicates good cyclic retention. The decrease in adsorption efficiency is likely due to the loss of active binding sites and the partial dissolution of CaCO3 within the filter mud due to repeated use.

[0015] (2) Removal of dyes from wastewater In a conical flask, add 100 mL of methyl orange simulated dye solution with a pH of 6.5, and then add 0.40 g of the bio-based composite environmentally friendly adsorbent prepared above. Adsorb for 180 minutes at 30°C and a vibration frequency of 150 osc / min, then centrifuge. Take the supernatant and use a UV-visible spectrophotometer to detect the concentration of residual methyl orange. Experimental results show that the bio-based composite environmentally friendly adsorbent prepared by the present invention has removal rates of 96.2%, 99.8% and 99.1% for methyl orange aqueous solutions with concentrations of 15 mg / L, 18 mg / L and 21 mg / L, respectively, demonstrating the great potential of this composite environmentally friendly adsorbent in environmental remediation of dye wastewater treatment.

[0016] Beneficial technical effects of the present invention: 1. In the preparation method of the bio-based composite environmentally friendly adsorbent of the present invention, the main raw material used is sugar filter mud, which is derived from the waste of the sugar production process of beet sugar factories. Its resource utilization has opened up a new path for the development of a circular bioeconomy. In addition, the activation treatment of the sugar filter mud of the present invention is simple, easy to operate, low in energy consumption, does not require complex equipment and expensive reagents, and is suitable for large-scale industrial production. Step (2) chemically crosslinks the surface of the sugar filter mud powder by using a raw material spray and a catalytic polymerization chemical crosslinking reaction with the sugar filter mud. The preparation process is simple, the reaction energy consumption is low, and it has industrial application prospects.

[0017] The present invention adopts a strategy of chemical cross-linking on the surface of sugar filter mud, using highly active isocyanate and amine monomers to form a polyurea coating by in-situ polymerization. The technical effects are as follows: (1) The polyurea molecular chain is rich in active functional groups such as urea (-HN-CO-NH-) and amine groups. The lone pairs of electrons carried by the nitrogen and oxygen atoms can form coordination bonds with metal ions and electron-rich dye molecules, giving the material a high-efficiency adsorption capacity for heavy metal ions (such as Pb2+, Cd2+, etc.) and dyes in water. This synergistic coordination adsorption mechanism enhances the application potential of sugar filter mud in the field of industrial wastewater treatment. (2) The high reactivity of the isocyanate group (-N=C=O) enables it to not only polymerize with amine monomers to form polyurea, but also undergo cross-linking reactions with hydroxyl groups (-OH) in the organic matter on the surface of the sugar filter mud to form a polyurethane structure. This polyurea-polyurethane composite structure significantly improves the interfacial bonding strength between the coating and the sugar filter mud matrix; (3) The polyurea layer itself has properties such as impact resistance and acid and alkali corrosion resistance, which can undoubtedly resist the mechanical wear of the sugar filter mud particles during the adsorption-desorption cycle; effectively prevent its deformation and dissolution under fluid erosion, and extend the service life of the material. (4) Polyurea has a porous structure, and its through-hole channel structure has both high permeability and low flow resistance. This structure allows heavy metal ions and dye molecules in the wastewater to quickly diffuse to the adsorption active sites, thereby increasing the adsorption rate. It provides a green and efficient technical solution for the treatment of heavy metal wastewater and printing and dyeing wastewater.

[0018] The bio-based composite environmentally friendly adsorbent of the present invention maintains a removal rate of Cd(II) and Pb(II) of over 85% after five consecutive adsorption-desorption cycles, confirming its excellent recyclability. Adsorption experiments on actual wastewater containing Pb(II), Cu(II), Ni(II) and Fe(III) show that the removal rate of each metal ion exceeds 92%, and the decolorization rate of methyl orange dye is over 96%, indicating its efficient treatment capability for heavy metal and dye pollution systems. Combined with the green attribute of its raw materials being derived from sugar industry waste, the present invention provides a highly competitive technical solution for deep treatment of industrial wastewater and environmental ecological restoration. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0020] Example 1. Preparation method of a bio-based composite environmentally friendly adsorbent (1) Activation treatment of sugar filter mud The sugar filter mud is washed with water and filtered, and the process is repeated several times until no soluble matter is dissolved. The sugar filter mud is dried at 120°C in a vacuum until constant weight is reached, cooled to room temperature, crushed, and passed through a 70-mesh sieve to obtain sugar filter mud powder. (2) Chemical cross-linking of sugar filter mud powder surface Take 1 kg of sugar filter mud powder, spray add 103 g of N, N'-diethyl-1, 3-propylenediamine containing 4 g of catalyst and 7 g of water under stirring, stir at room temperature for 10 minutes, continue to spray add 210 g of isocyanate PM-200, continue stirring for 60 minutes, stop stirring, age at 60°C for 3 hours, and cool to room temperature to prepare a sugar filter mud / polyurea composite material, that is, a composite material with chemical cross-linking on the surface of the sugar filter mud, that is, a bio-based composite environmentally friendly adsorbent; The sugar filter mud in the above step (1) is the precipitate mixture obtained by removing impurities from beet juice by carbonation adsorption in a beet sugar factory; The vacuum drying at 120°C in step (1) above has an absolute vacuum pressure of 10-100 Pa; The catalyst in the above step (2) is a diethylene glycol solution of ethylenediamine with a mass fraction of 33%.

[0021] The above-mentioned isocyanate PM-200 is produced by Wanhua Chemical Group Co., Ltd. Its mass content of isocyanate -NCO is 30.5-32.0%. It is a mixture of higher-functionality isocyanate and diphenylmethane diisocyanate. It is a brown liquid at room temperature, with a viscosity of 150-250mPa•s at 25℃ and a density of 1.22-1.25g / cm3 at 25℃.

[0022] Example 2. Preparation method of a bio-based composite environmentally friendly adsorbent (1) Activation treatment of sugar filter mud The method is the same as in Example 1; (2) Chemical cross-linking of sugar filter mud powder surface Take 1 kg of sugar filter mud powder, spray add 110 g of N, N'-diethyl-1, 3-propylenediamine containing 5 g of catalyst and 8 g of water under stirring, stir at room temperature for 10 minutes, continue to spray add 230 g of isocyanate PM-200, continue stirring for 60 minutes, stop stirring, age at 60 ° C for 3 hours, and cool to room temperature to obtain a sugar filter mud / polyurea composite material, that is, a composite material with chemical cross-linking on the surface of sugar filter mud powder, that is, a bio-based composite environmentally friendly adsorbent.

[0023] The sugar filter mud in the above step (1) is vacuum dried at 120°C, as in step 1; The catalyst and isocyanate PM-200 in the above step (2) are the same as those in embodiment 1.

[0024] Example 3 Application of the bio-based composite environmentally friendly adsorbent prepared by the preparation method of Example 1 or 2 for removing heavy metal ions from wastewater (1) Adsorption experiment: In a conical flask, add 100 mL of simulated wastewater solution of metal ions with a pH of 6-8, and then add 0.50 g of the bio-based composite environmentally friendly adsorbent prepared above. Adsorb for 2 h at 30 °C and a vibration frequency of 150 osc / min, then centrifuge. Take the supernatant to detect the remaining metal ion concentration; (2) Desorption experiment: 100 mL of 0.1 mol / L HCl solution was added to a conical flask, followed by 0.5 g of a dried bio-based composite environmentally friendly adsorbent that had adsorbed metal ions. Desorption was carried out at 30 °C and a vibration frequency of 150 osc / min for 4 h. After centrifugation, the supernatant was collected to detect the concentration of desorbed metal ions. (3) Cyclic adsorption experiment: 100 mL of 0.1 mol / L HCl solution was added to a conical flask, followed by 0.5 g of dried bio-based composite environmentally friendly adsorbent that had adsorbed metal ions. The adsorbent was desorbed at 30 °C and a vibration frequency of 150 osc / min for 4 h to effectively desorb the adsorbed metal ions. The adsorbent was then filtered and washed with water for more than 3 times, and dried at 120 °C in a vacuum oven to a constant weight before use in subsequent adsorption experiments to evaluate the reusability of the bio-based composite environmentally friendly adsorbent. The detection was performed using a flame atomic absorption spectrophotometer; The results showed that the bio-based composite environmentally friendly adsorbents prepared in Examples 1 and 2 both had good reusability. Over five cycles, the Pb(II) removal efficiency decreased from 98.3% to 87.9%, and the Cd(II) removal efficiency decreased from 98.9% to 97.3%. This indicates good cyclic retention. The decrease in adsorption efficiency may be due to the loss of active binding sites and the partial dissolution of CaCO3 within the filter mud due to repeated use.

[0025] Example 4 The bio-based composite environmentally friendly adsorbent prepared in Example 1 or 2 is used to remove heavy metal ions from wastewater samples. In a conical flask, add 100 mL of the metal ion wastewater solution, and then add 0.50 g of the bio-based composite environmentally friendly adsorbent prepared in Example 1 or Example 2. Adsorb for 2 h at 30 ° C and a vibration frequency of 150 osc / min, then centrifuge. Take the supernatant to detect the remaining metal ion concentration; Table 1 Removal rate of metal ions in wastewater samples Table 1 shows the initial concentration, final concentration and removal rate of metal ions before and after the composite environmentally friendly adsorbent of the present invention adsorbs actual wastewater from two industrial sites. For actual samples 1 and 2, the composite environmentally friendly adsorbent of the present invention removes Mn(II) ions in sample 2 with a removal rate of 88.7%. The removal percentages of other metal ions, Pb(II), Cu(II), Ni(II) and Fe(III) metal ions are all above 92%. These results reveal the great potential of the composite environmentally friendly adsorbent in environmental remediation of wastewater treatment, which expands the applicability of the composite environmentally friendly adsorbent outside laboratory conditions and shows its potential in large-scale industrial applications for treating contaminated water with different pollutant ions.

[0026] Example 5: The bio-based composite environmentally friendly adsorbent prepared in Example 1 or 2 is used to remove dyes from wastewater. In a conical flask, 100 mL of a methyl orange simulated dye solution with a pH of 6.5 was added, followed by 0.40 g of the bio-based composite environmentally friendly adsorbent prepared in Example 1 or Example 2. The mixture was adsorbed for 180 min at 30°C and a vibration frequency of 150 osc / min, and then centrifuged. The supernatant was collected and the concentration of the remaining methyl orange was measured using a UV-visible spectrophotometer. Experimental results show that the bio-based composite environmentally friendly adsorbent prepared by the present invention has removal rates of 96.2%, 99.8% and 99.1% for methyl orange aqueous solutions with concentrations of 15 mg / L, 18 mg / L and 21 mg / L, respectively, demonstrating the great potential of this composite environmentally friendly adsorbent in environmental remediation of dye wastewater treatment.

Claims

1. A method for preparing a bio-based composite environmentally friendly adsorbent, characterized in that: The preparation steps are as follows: (1) Activation treatment of sugar filter mud The sugar filter mud is washed with water and filtered, and the process is repeated several times until no soluble matter is dissolved. The sugar filter mud is dried at 120°C in a vacuum until constant weight is reached, cooled to room temperature, crushed, and passed through a 70-mesh sieve to obtain sugar filter mud powder. (2) Chemical cross-linking of sugar filter mud surface Take 1 kg of sugar filter mud powder, spray add 103-110 g of N, N'-diethyl-1,3-propylenediamine containing 4-5 g of catalyst and 7-8 g of water under stirring, stir at room temperature for 10 min, continue to spray add 210-230 g of isocyanate PM-200, continue stirring for 60 min, stop stirring, age at 60 ° C for 3 h, and cool to room temperature to obtain a sugar filter mud / polyurea composite material, that is, a composite material with chemical cross-linking on the surface of sugar filter mud powder, that is, a bio-based composite environmentally friendly adsorbent.

2. The method for preparing the bio-based composite environmentally friendly adsorbent according to claim 1, characterized in that: The sugar filter mud in step (1) is derived from the precipitation mixture obtained by removing impurities from beet juice by carbonation adsorption in a beet sugar factory.

3. The method for preparing the bio-based composite environmentally friendly adsorbent according to claim 1, characterized in that: The vacuum drying at 120° C. in step (1) has an absolute vacuum pressure of 10-100 Pa.

4. The method for preparing the bio-based composite environmentally friendly adsorbent according to claim 1, characterized in that: The catalyst in step (2) is a diethylene glycol solution of ethylenediamine with a mass fraction of 33%.

5. The method for preparing the bio-based composite environmentally friendly adsorbent according to claim 1, characterized in that: The isocyanate PM-200 has an isocyanate-NCO mass content of 30.5-32.0%, is a mixture of higher-functionality isocyanate and diphenylmethane diisocyanate, is a brown liquid at room temperature, has a viscosity of 150-250 mPa•s at 25°C, an isocyanate-NCO mass content of 30.5-32.0%, and a density of 1.22-1.25 g / cm3 at 25°C.

6. Use of the bio-based composite environmentally friendly adsorbent prepared by the preparation method according to claim 1 for removing heavy metal ions, organic dyes and other pollutants in industrial wastewater.

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