Pomegranate peel polyphenol extract / chitosan composite functional material as well as preparation method and application thereof

Abstract

The invention provides a pomegranate peel polyphenol extract / chitosan composite functional material as well as a preparation method and application thereof. The composite functional material is prepared on the basis of Schiff base reaction among pomegranate peel polyphenol extract, chitosan and glutaraldehyde. Wherein the pomegranate peel polyphenol extract is used as a functional precursor and is used for increasing the number and / or density of o-hydroxyls on the surface of the composite functional material and improving the coordination chelation capability on scattered metal ions; chitosan is used as a polymer precursor, is used as a skeleton and / or is used for providing amino acid sites; glutaraldehyde is used as a cross-linking agent and reacts with the pomegranate peel polyphenol extract and the chitosan to form a three-dimensional network structure, so that the stability of the composite functional material is improved. The composite functional material prepared through the formula and the process design has excellent adsorption performance on scattered metal ions in water, the germanium ion adsorption capacity is 19.14-22.32 mg / g, and the composite functional material can be recycled through elution.

Description

Technical Field

[0001] The invention belongs to the field of resource environment and material technology, and particularly relates to a pomegranate peel polyphenol extract / chitosan composite functional material and a preparation method and application thereof. Background Art

[0002] As a strategic rare earth metal, germanium, due to its unique physical and chemical properties, is widely used in a variety of high-tech fields, including the semiconductor industry, infrared optics, fiber-optic communications, aerospace, solar cells, and medicine. In nature, germanium primarily occurs as an associated element in polymetallic deposits, with an extremely low probability of independent mineralization. Currently, the primary raw materials for industrial germanium recovery are aluminum smelting byproducts, zinc smelting residues, and coal fly ash. Coal contains over 300 μg / g of germanium, but during the acid leaching of coal, the leachate contains various metallic impurities in addition to germanium. To effectively recover germanium, numerous studies have investigated the selective separation of germanium from related elements during the leaching process.

[0003] At present, the methods for enriching and recovering germanium from solutions mainly include adsorption, solvent extraction, ion exchange, membrane separation and tannin precipitation. Among them, adsorption has become one of the most efficient methods for recovering metal ions due to its advantages such as simple preparation, convenient operation and low environmental harm. At present, the adsorption materials used to recover germanium ions from coal leachate mainly include metal oxides (such as titanium dioxide, iron oxide), layered silicates (such as clay minerals) and functionalized polymer materials (such as chelating resins). However, these materials still have obvious limitations in practical applications: such as low adsorption efficiency for low-concentration germanium ions, poor material regeneration performance, and insufficient stability during recycling, which seriously restrict their promotion and application on an industrial scale.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide a pomegranate peel polyphenol extract / chitosan composite functional material, wherein the composite functional material is prepared based on the Schiff base reaction between pomegranate peel polyphenol extract, chitosan and glutaraldehyde;

[0006] The pomegranate peel polyphenol extract is a functional precursor used to increase the number and / or density of ortho-hydroxyl groups on the surface of the composite functional material and to improve the coordination and chelation ability of scattered metal ions;

[0007] The chitosan is a polymer precursor, serving as a skeleton and / or providing amino acid sites;

[0008] The glutaraldehyde is a cross-linking agent, which reacts with the pomegranate peel polyphenol extract and chitosan to form a three-dimensional network structure, thereby improving the stability of the composite functional material.

[0009] In a preferred embodiment, the scattered metal ions are germanium ions.

[0010] In a preferred embodiment, the adsorption capacity of the composite functional material for germanium ions can reach 22.32 mg / g.

[0011] Another object of the present invention is to provide a method for preparing any one of the above-mentioned pomegranate peel polyphenol extract / chitosan composite functional materials, comprising the following steps:

[0012] (1) washing, drying, and crushing pomegranate peel to obtain pomegranate peel powder; dispersing the pomegranate peel powder in an ethanol solution, and ultrasonically extracting it for a period of time to obtain a slurry; centrifuging the slurry, taking the supernatant, and concentrating it under reduced pressure; drying and crushing the obtained concentrate to obtain a pomegranate peel polyphenol extract, which is recorded as PPPs;

[0013] (2) dispersing the PPPs prepared in step (1) in deionized water to obtain a PPPs solution; mixing the PPPs solution with chitosan and stirring to react;

[0014] (3) The reactant obtained in step (2) was filtered, and the solid was collected and dispersed in glutaraldehyde, and reacted at room temperature for a period of time. The resulting mixture was reacted in an ice-water bath for a period of time. The slurry after the reaction was filtered, and the solid was collected, washed, and dried to obtain a pomegranate peel polyphenol extract / chitosan composite functional material, which was recorded as PPPs-CS.

[0015] In a preferred embodiment, in step (1), the pomegranate peel can be dried using conventional methods and conditions known to those skilled in the art, such as drying at 40-60° C. to constant weight.

[0016] In a preferred embodiment, in step (1), the particle size of the pomegranate peel powder is below 425 microns.

[0017] In a preferred embodiment, in step (1), the solid-liquid ratio of the pomegranate peel powder to the ethanol solution is 1 g: (35-50) mL. Insufficient ethanol usage will result in incomplete extraction, while excessive ethanol usage will increase energy consumption for subsequent concentration. Therefore, the present invention limits the solid-liquid ratio of the pomegranate peel powder to the ethanol solution to 1 g: (35-50) mL.

[0018] In a preferred embodiment, in step (1), the volume fraction of the ethanol solution is 50-65%. In the present invention, the specific volume fraction of the ethanol solution is set so that this range can achieve the best match between the solvent polarity and the solubility characteristics of most polyphenolic compounds, thereby achieving the best extraction effect. When the volume fraction of ethanol is less than 50%, the solubility of weakly polar polyphenolic compounds is significantly reduced due to the excessive polarity of the solvent; when the volume fraction of ethanol exceeds 70%, the co-extraction of impurities (such as lipids) may increase.

[0019] In a preferred embodiment, in step (1), the ultrasonic extraction temperature is 50-70°C, the ultrasonic extraction power is 50-150W, and the ultrasonic extraction time is 60-90min; preferably, the ultrasonic extraction temperature is 60°C, the ultrasonic extraction power is 100W, and the ultrasonic extraction time is 75min.

[0020] In a preferred embodiment, in step (1), the reduced pressure concentration conditions include: reducing the volume to 1 / 5 to 1 / 4 of the original volume at 45-55°C and 0.1 MPa.

[0021] In a preferred embodiment, in step (1), the concentrate can be dried using conventional methods and conditions known to those skilled in the art, such as drying at 40-60° C. for 2-6 hours.

[0022] In a preferred embodiment, in step (1), the particle size of the pomegranate peel polyphenol extract is 50-100 μm

[0023] In a preferred embodiment, in step (2), the mass concentration of the PPPs solution is 70-85 g / L.

[0024] In a preferred embodiment, in step (2), the mass ratio of the chitosan to the PPPs prepared in step (1) is 1:(1-2).

[0025] In a preferred embodiment, in step (2), the stirring reaction temperature is room temperature, and the stirring reaction time is 5 to 7 hours.

[0026] In a preferred embodiment, in step (2), after the stirring reaction, the mixture is further washed with deionized water for 2 to 4 times.

[0027] In a preferred embodiment, in step (3), the ratio of glutaraldehyde to chitosan used in step (2) is (25-35) mL:1 g. Insufficient glutaraldehyde can lead to incomplete cross-linking, manifested as insufficient coverage of amino and phenolic hydroxyl reaction sites and a loose intermolecular cross-linking network structure. Exceeding the optimal glutaraldehyde dosage can lead to steric hindrance due to the close proximity of cross-linking sites, thereby reducing the effective cross-linking efficiency. Therefore, this case limits the aforementioned glutaraldehyde to chitosan ratio range.

[0028] In a preferred embodiment, in step (3), the concentration of glutaraldehyde is 20-30 wt%.

[0029] In a preferred embodiment, in step (3), the reaction time at room temperature is 0.5 to 1.5 hours.

[0030] In a preferred embodiment, in step (3), the ice-water bath reaction time is 5 to 7 hours.

[0031] In a preferred embodiment, in step (3), the washing can be performed using conventional methods and conditions known to those skilled in the art, such as washing with deionized water until neutral.

[0032] In a preferred embodiment, in step (3), the drying can be carried out using conventional methods and conditions known to those skilled in the art, such as vacuum drying at 40-60° C. for 18-30 hours.

[0033] Another object of the present invention is to provide a use of any one of the above-mentioned pomegranate peel polyphenol extract / chitosan composite functional materials in separating and recovering dispersed metal ions in coal leachate.

[0034] In a preferred embodiment, the application method comprises: adsorption recovery of scattered metal ions and / or desorption regeneration of composite functional materials;

[0035] The adsorption method comprises: placing the composite functional material in a coal leachate containing scattered metal ions; preferably, the scattered metal ions are germanium ions; the concentration of germanium ions in the coal leachate is above 20 mg / L; the pH of the coal leachate is 3 to 11; and the adsorption time is 2 to 48 hours.

[0036] The desorption method comprises: eluting and regenerating the composite functional material with a 1 mol / L HCl 50% ethanol solution; preferably, the preparation method of the 1 mol / L HCl 50% ethanol solution comprises: taking equal volumes of anhydrous ethanol and deionized water to mix to form a 50% ethanol aqueous solution, and then adding concentrated hydrochloric acid to the solution and adjusting the volume to make the HCl concentration reach 1 mol / L.

[0037] In a preferred embodiment, after the adsorption-desorption cycle is repeated 5 times, the adsorption efficiency of the composite functional material is 87.34%.

[0038] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0039] 1. The present invention prepares pomegranate peel polyphenol extract / chitosan composite functional material particles with a particle size of 100-150 μm, with a smooth surface and no obvious grain boundary structure. This unique amorphous structure is more conducive to the uniform distribution of active sites and sufficient contact of reactants.

[0040] 2. In the present invention, pomegranate peel polyphenol extract is used as a functional precursor to increase the number and / or density of orthohydroxyl groups on the surface of the composite functional material, and to improve the coordination and chelating ability of scattered metal ions; chitosan is used as a polymer precursor, as a skeleton and / or for providing amino acid sites; glutaraldehyde is used as a cross-linking agent, by reacting with pomegranate peel polyphenol extract and chitosan, a three-dimensional network structure is formed to improve the stability of the composite functional material. At the same time, the amino group of chitosan provides electrostatic adsorption and primary complexing sites, and the phenolic hydroxyl group of polyphenol provides strong chelating sites and π action sites, which synergistically enhance the adsorption effect of scattered metal ions. The cross-linked network provided by glutaraldehyde can then orient the active groups of chitosan and polyphenol, avoid "ineffective exposure" of functional groups due to molecular chain motion, and prevent polyphenol from falling off and losing in solution, so that the composite functional material still has high adsorption capacity for germanium ions in a complex environment.

[0041] 3. The preparation method of the present invention has simple process, safe operation, low requirements on equipment and energy consumption, clean and environmentally friendly production process, and no three wastes are generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] These and / or other aspects and advantages of the present invention will become more apparent and more readily understood from the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0043] Figure 1 This is a schematic diagram of the process for preparing the pomegranate peel polyphenol extract / chitosan composite functional material of the present invention;

[0044] Figure 2 This is the SEM image of the pomegranate peel polyphenol extract / chitosan composite functional material prepared in Example 1 of the present invention;

[0045] Figure 3 Zeta potential diagram of the pomegranate peel polyphenol extract / chitosan composite functional material prepared in Example 1 of the present invention at different pH values;

[0046] Figure 4This is a graph showing the adsorption of Ge(IV) at different pH values ​​by the pomegranate peel polyphenol extract / chitosan composite functional materials prepared in Examples 1-3 of the present invention;

[0047] Figure 5 This is a graph showing the adsorption efficiency of the pomegranate peel polyphenol extract / chitosan composite functional material for germanium ions at different adsorption times prepared in Example 1 of the present invention;

[0048] Figure 6 This is a diagram showing the adsorption efficiency of germanium ions by the pomegranate peel polyphenol extract / chitosan composite functional material prepared in Example 1 of the present invention after multiple cycles of adsorption-desorption. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the protection scope of the present invention is not limited to the specific embodiments.

[0050] The embodiment of the present invention provides a pomegranate peel polyphenol extract / chitosan composite functional material and its preparation method and application, which effectively solves the problem of poor recovery of germanium ions in coal leachate in the prior art.

[0051] The technical solution of this application is described in detail below through specific embodiments:

[0052] Unless otherwise specified, the technical means used in the present invention are conventional means well known to those skilled in the art. The various raw materials, reagents, instruments, and equipment used in the present invention can be purchased commercially or prepared by existing methods. Unless otherwise specified, the reagents used in the present invention are of analytical grade. The room temperature in the present invention is 25±5°C.

[0053] In the present invention, parts by weight may be weight units known in the art such as μg, mg, g, kg, etc., or multiples thereof, such as 1 / 10, 1 / 100, 10 times, 100 times, etc.

[0054] Example 1

[0055] like Figure 1 As shown in the flow chart, a pomegranate peel polyphenol extract / chitosan composite functional material comprises the following steps:

[0056] 1) Wash the pomegranate peel with distilled water to remove surface impurities, dry it in a 50°C oven until the mass is constant, grind it, and pass it through a 40-mesh sieve.

[0057] 2) The obtained pomegranate peel powder was added to a 65% ethanol solution at a solid-liquid ratio of 1 g:40 mL, and ultrasonic extraction was performed at 60° C. with a power of 100 W for 75 min.

[0058] 3) The obtained mixed slurry was centrifuged, and the supernatant was collected and concentrated under reduced pressure at 50° C. and 0.1 MPa until the volume was reduced to 1 / 5 of the original volume. After drying at 50° C., the mixture was ground and pulverized to obtain a pomegranate peel polyphenol extract with a particle size of 80 μm, which was recorded as PPPs.

[0059] 4) Ultrasonic dispersion of the obtained PPPs in an appropriate amount of deionized water to obtain an 85 g / L PPPs solution.

[0060] 5) Chitosan was added to the PPPs solution in a mass ratio of 1:2 between chitosan and the PPPs solid in step 4), and the reaction was stirred at room temperature for 6 h. The suspension was filtered and washed three times with deionized water.

[0061] 6) The washed suspension was dispersed in 25 wt% glutaraldehyde in a ratio of 30 mL glutaraldehyde to 1 g chitosan from step 5), and the mixture was reacted at room temperature for 1 hour. The mixture was then transferred to an ice-water bath and reacted for 6 hours.

[0062] 7) The mixed reaction slurry was filtered, and the obtained solid was washed with deionized water until neutral, and vacuum dried at 50° C. for 24 hours to obtain a pomegranate peel polyphenol extract / chitosan composite functional material, which was recorded as PPPs-CS.

[0063] The SEM spectrum obtained in Example 1 is as follows Figure 2 As shown in the figure, the prepared PPPs-CS composite material has a rough and loose surface morphology and a non-uniformly distributed porous structure. The rough surface and non-uniformly distributed pores provide a large number of active sites for Ge(IV) adsorption and promote its diffusion, thus having a favorable effect on adsorption.

[0064] The Zeta potential diagram prepared in Example 1 is as follows Figure 3 As shown in the figure, it can be seen that the surface potential of the prepared PPPs-CS composite material is negative in the pH range of 3 to 11. When the pH value is less than 10, and as the pH increases, the absolute value of the zeta potential gradually increases. The reason is that the alkaline environment increases surface deprotonation and enhances the negative charge. When the pH value is greater than 10, the negative charge on the particle surface tends to be saturated. At this time, if the NaOH solution is continued to be added, the ionic strength also increases. Because the surface charge of the particles is close to saturation, the absolute value of the zeta potential on the adsorbent surface no longer increases significantly. At the same time, as the ionic strength increases, the conductivity increases rapidly, resulting in a gradually enhanced shielding effect, which causes the absolute value of the zeta potential to show a slowly decreasing trend.

[0065] Example 2

[0066] Compared with Example 1, the only difference is that in step 6), the ratio of glutaraldehyde to chitosan in step 5) is 20 mL:1 g, and the amounts of other raw materials and process parameters are exactly the same as those in Example 1.

[0067] Example 3

[0068] Compared with Example 1, the only difference is that in step 6), the ratio of glutaraldehyde to chitosan in step 5) is 40 mL:1 g, and the amounts of other raw materials and process parameters are exactly the same as those in Example 1.

[0069] Application Example 1

[0070] The pomegranate peel polyphenol extract / chitosan composite functional material prepared in Examples 1-3 was subjected to an adsorption experiment, comprising the following steps:

[0071] 10 mg of the composite functional material prepared in Example 1-3 was placed in 20 mL of coal leachate with a germanium ion concentration of 20 mg / L. The solution pH range was 3 to 11. The reaction was carried out at 25° C. for 48 hours. The germanium ion concentration in the solution after adsorption was tested using an ultraviolet spectrophotometer, and the maximum absorption wavelength was 510 nm.

[0072] The results are as follows Figure 4 As shown in the figure, it can be seen that the PPPs-CS composite materials prepared in different examples all have good adsorption effects on germanium ions in solutions with a pH of 3 to 11. Among them, the PPPs-CS composite material prepared in Example 1 has the best adsorption effect at a pH of 5 to 7: in a germanium ion solution with a pH of 7, the adsorption capacity of the composite functional material prepared in Example 1 for germanium ions reaches 22.32 mg / g.

[0073] Application Example 2

[0074] The pomegranate peel polyphenol extract / chitosan composite functional material prepared in Example 1 was subjected to an adsorption experiment, comprising the following steps:

[0075] 10 mg of the composite functional material prepared in Example 1 was placed in 20 mL of coal leachate with a germanium ion concentration of 20 mg / L. The solution pH was 7 and reacted at 25° C. for a period of time. The germanium ion concentration in the solution after adsorption was tested using an ultraviolet spectrophotometer, and the maximum absorption wavelength was 510 nm.

[0076] The adsorption amount is calculated as follows:

[0077] The results are as follows Figure 5 As shown, it can be seen that the composite functional material prepared in Example 1 adsorbs germanium ions rapidly in the first 18 hours and reaches adsorption saturation after 48 hours.

[0078] Application Example 3

[0079] The pomegranate peel polyphenol extract / chitosan composite functional material prepared in Example 1 was subjected to an adsorption-desorption experiment, comprising the following steps:

[0080] Adsorption: 100 mg of the composite functional material prepared in Example 1 was placed in 50 mL of coal leachate with a germanium ion concentration of 20 mg / L at a pH of 7. The reaction was carried out at 25°C for 24 hours. The germanium ion concentration in the solution after adsorption was measured using an ultraviolet spectrophotometer, with a maximum absorption wavelength of 510 nm.

[0081] Desorption: The adsorbed composite functional material was eluted with a 1 mol / L HCl 50% ethanol solution until no germanium ions were detected in the eluate, and then dried at 50°C for 24 hours before the next adsorption.

[0082] The adsorption efficiency calculation formula is:

[0083] The adsorption efficiency of the composite functional material was calculated by statistically analyzing the adsorption-desorption cycles for 5 times. Figure 6 As shown in the figure, it can be seen that after the composite material prepared in Example 1 was subjected to repeated adsorption-desorption for 5 times, the adsorption efficiency was still as high as 87.34%, indicating that the polyphenol extract / chitosan composite functional material prepared in the present invention has good stability and renewability.

[0084] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A pomegranate peel polyphenol extract / chitosan composite functional material, characterized in that: The composite functional material is prepared based on the Schiff base reaction between pomegranate peel polyphenol extract, chitosan and glutaraldehyde; The pomegranate peel polyphenol extract is a functional precursor used to increase the number and / or density of ortho-hydroxyl groups on the surface of the composite functional material and to improve the coordination and chelation ability of scattered metal ions; The chitosan is a polymer precursor, serving as a skeleton and / or providing amino acid sites; The glutaraldehyde is a cross-linking agent, which reacts with the pomegranate peel polyphenol extract and chitosan to form a three-dimensional network structure, thereby improving the stability of the composite functional material.

2. The pomegranate peel polyphenol extract / chitosan composite functional material according to claim 1, wherein: The scattered metal ions are germanium ions.

3. The pomegranate peel polyphenol extract / chitosan composite functional material according to claim 1, wherein: The adsorption capacity of the composite functional material for germanium ions can reach 22.32 mg / g.

4. The method for preparing the pomegranate peel polyphenol extract / chitosan composite functional material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) washing, drying, and crushing pomegranate peel to obtain pomegranate peel powder; dispersing the pomegranate peel powder in an ethanol solution, and ultrasonically extracting it for a period of time to obtain a slurry; centrifuging the slurry, taking the supernatant, and concentrating it under reduced pressure; drying and crushing the obtained concentrate to obtain a pomegranate peel polyphenol extract, which is recorded as PPPs; (2) dispersing the PPPs prepared in step (1) in deionized water to obtain a PPPs solution; mixing the PPPs solution with chitosan and stirring to react; (3) The reactant obtained in step (2) was filtered, and the solid was collected and dispersed in glutaraldehyde, and reacted at room temperature for a period of time. The resulting mixture was reacted in an ice-water bath for a period of time. The slurry after the reaction was filtered, and the solid was collected, washed, and dried to obtain a pomegranate peel polyphenol extract / chitosan composite functional material, which was recorded as PPPs-CS.

5. The method for preparing the pomegranate peel polyphenol extract / chitosan composite functional material according to claim 3, wherein: In step (1), the solid-liquid ratio of the pomegranate peel powder to the ethanol solution is 1 g: (35-50) mL; and the volume fraction of the ethanol solution is 50-65%.

6. The method for preparing the pomegranate peel polyphenol extract / chitosan composite functional material according to claim 3, wherein: In step (2), the mass ratio of the chitosan to the PPPs prepared in step (1) is 1:(1-2).

7. The method for preparing the pomegranate peel polyphenol extract / chitosan composite functional material according to claim 3, wherein: In step (3), the ratio of the amount of glutaraldehyde to the chitosan in step (2) is (25-35) mL: 1 g; the concentration of the glutaraldehyde is 20-30 wt%.

8. Use of the pomegranate peel polyphenol extract / chitosan composite functional material according to any one of claims 1 to 3 in separating and recovering dispersed metal ions in coal leachate.

9. Use of the pomegranate peel polyphenol extract / chitosan composite functional material in separating and recovering scattered metal ions in coal leachate as claimed in claim 8, characterized in that: The application method includes: adsorption recovery of scattered metal ions and / or desorption regeneration of composite functional materials; wherein, the desorption method includes: elution and regeneration of the composite functional materials with 1 mol / L HCl 50% ethanol solution.

10. Use of the pomegranate peel polyphenol extract / chitosan composite functional material as claimed in claim 9 in separating and recovering scattered metal ions in coal leachate, characterized in that: After the adsorption-desorption cycle was repeated 5 times, the adsorption efficiency of the composite functional material was 87.34%.

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