Preparation method of bimetallic modified cathode and application thereof in phosphorus recovery

Abstract

The application discloses a preparation method of a bimetallic modified cathode and application of the bimetallic modified cathode in phosphorus recovery, and belongs to the technical field of phosphorus recovery. The material takes carbon felt as a substrate, loads Fe-Ni bimetallic chitosan active layers, realizes uniform dispersion of Fe and Ni species in an atomic scale by means of Fe / Ni electronic restructuring effect and chitosan N / O coordination effect, and can realize efficient spontaneous capture of phosphorus by utilizing the inner sphere coordination effect between Fe / Ni active sites and phosphate under acidic conditions. After saturation of adsorption, a direct current bias is applied in a two-electrode system, strong electrostatic repulsive force is generated on the cathode surface due to electron accumulation, and rapid reversible release of phosphate is realized by combining the interface deprotonation effect and the weakening of the coordination bond. The application does not need chemical regenerants, and can complete in-situ regeneration of the electrode by driving of an electric field only, has the advantages of fast desorption rate and environmental friendliness, and provides a sustainable new technical scheme for purification of phosphorus-containing wastewater and recovery of phosphorus resources.

Description

Technical Field

[0001] This invention belongs to the field of phosphorus recovery technology, specifically relating to a method for preparing a bimetallic modified cathode and its application in phosphorus recovery. Background Technology

[0002] Phosphorus is one of the main pollutants causing eutrophication in water bodies. Excessive discharge can lead to a series of environmental problems such as algal blooms, water quality deterioration, and ecosystem imbalance. Meanwhile, as a non-renewable critical strategic resource, phosphorus has limited natural reserves, making efficient recovery and recycling crucial for ensuring resource security. Among existing phosphorus treatment technologies, adsorption is widely used for purifying phosphorus-containing wastewater and recovering phosphorus resources due to its simple operation, high removal efficiency, and wide applicability. However, traditional adsorption materials generally suffer from the drawback of high regeneration difficulty. The regeneration process often requires the addition of large amounts of chemicals such as acids, alkalis, and salts, resulting in high operating costs, complex procedures, and a tendency to generate secondary pollution, making it difficult to meet the requirements of green and sustainable treatment.

[0003] Electrochemical regulation, as an environmentally friendly interfacial control method, can achieve controlled adsorption and desorption of ions by applying an electric field without the need for a large number of chemical reagents. However, conventional carbon electrode materials have a weak binding capacity for phosphates, and the adsorption force is mainly physical adsorption, making it difficult to form a stable chemical bond. In complex aquatic environments, it is even more difficult to achieve an efficient match and balance between adsorption binding force and electric field desorption force, resulting in low adsorption capacity, incomplete regeneration, and poor cycle stability.

[0004] Therefore, developing a novel functional electrode material that combines strong phosphorus adsorption affinity, high selectivity, and rapid in-situ regeneration via electrochemical means is of significant application value and practical importance for achieving efficient treatment of phosphorus-containing wastewater and sustainable recovery of phosphorus resources. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a bimetallic modified cathode and its application in phosphorus recovery.

[0006] This invention first provides a method for preparing a bimetallic modified cathode, comprising the following steps: dissolving chitosan in glacial acetic acid solution and stirring at room temperature until completely dissolved; then adding iron salt precursor and nickel salt precursor and stirring until dispersed to obtain a mixed solution; immersing the pretreated carbon felt in the mixed solution for 10 min; removing the electrode to remove excess chitosan metal salt solution from its surface and placing it in a 1M sodium hydroxide solution for curing at room temperature for 5 min; finally, placing the cured electrode in a 60°C oven for drying for 1 h to obtain an Fe-Ni bimetallic chitosan modified carbon felt composite cathode material.

[0007] Ideally, the ratio of chitosan to glacial acetic acid solution is 1 g: 0.5 mL.

[0008] More preferably, the iron salt precursor includes divalent iron salt and trivalent iron salt, wherein the divalent iron salt is FeCl2·4H2O and the trivalent iron salt is FeCl3·6H2O; the nickel salt precursor is NiCl2·6H2O.

[0009] More optimally, the Fe provided by the divalent iron salt 2+ Fe provided by trivalent iron salts 3+ Ni provided by nickel salt precursor 2+ The molar ratio of the three components is 1:2:3, and the total amount of substance of the three components is 0.015 mol.

[0010] Second, the present invention further provides a bimetallic modified cathode obtained by the above preparation method.

[0011] The application of the aforementioned bimetallic modified cathode in phosphorus recovery also falls within the scope of protection of this invention.

[0012] Finally, the present invention provides a method for phosphorus recovery, comprising the following steps: (a) The bimetallic modified cathode described in claim 3 is placed in phosphorus-containing wastewater and adsorbed under acidic conditions. The protonated amino groups of chitosan (CS) generate electrostatic attraction with phosphate, while the Fe / Ni active center forms a strong internal sphere coordination (MOP bond) with phosphate to achieve efficient capture of phosphate. (b) After adsorption is complete, a cathode bias voltage is applied to the bimetallic modified cathode in the two-electrode system. Due to the accumulation of electrons, a strong electrostatic repulsion force is generated on the cathode surface, which at the same time triggers the interface deprotonation effect, weakens the coordination bond between Fe / Ni and phosphate, and causes phosphate to desorb and be released into the solution, thereby realizing the in-situ regeneration of the electrode.

[0013] Ideally, the cathode bias is a DC voltage with a value of 3.0V-5.5V.

[0014] Ideally, the acidic conditions are pH 3-5.

[0015] Further optimized, the acidic condition is pH=3.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Green and environmentally friendly regeneration method: The adsorbent can be regenerated in situ by simply adjusting the applied voltage. No chemical reagents such as acids, alkalis, and salts are consumed throughout the process. It is green, environmentally friendly and has no secondary pollution. (2) Significantly improved adsorption and regeneration performance: Electron rearrangement occurs between Fe and Ni bimetals, which can effectively optimize the coordination field of active sites, thus significantly improving the adsorption rate and regeneration efficiency of the material. (3) Excellent stability in recycling: The chitosan backbone can form a stable and strong hydrogen bond network. Combined with the synergistic effect of bimetallic active sites, it ensures that the material maintains its structural integrity after multiple adsorption-desorption cycles. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a SEM image of the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material (Fe-Ni / CS@CF) in Example 1 of the present invention; Figure 2 The X-ray diffraction pattern of the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material (Fe-Ni / CS@CF) in Example 1 of this invention; Figure 3 The X-ray photoelectron spectrum of the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material (Fe-Ni / CS@CF) in Example 1 of this invention is shown below. Figure 4 The phosphate adsorption concentration of the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material (Fe-Ni / CS@CF) in Example 2 of this invention under different pH conditions; Figure 5 The results of the phosphate adsorption isotherm model fitting for the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material (Fe-Ni / CS@CF) in Example 2 of this invention at pH=3. Figure 6 The results show the phosphate desorption efficiency of the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material (Fe-Ni / CS@CF) in Example 3 of this invention under different DC voltages applied in a two-electrode system. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1:

[0021] A method for preparing a bimetallic modified cathode includes the following steps: dissolving 1g of chitosan in 0.5ml of glacial acetic acid solution, stirring continuously at room temperature until the chitosan is completely dissolved to form a transparent and homogeneous chitosan gel solution; adding iron and nickel salt precursors, namely: FeCl2·4H2O, FeCl3·6H2O, and NiCl2·6H2O in the order of Fe... 2+ Fe 3+ Ni 2+ A total of 0.015 mol of a chitosan gel solution was added to the above solution at a molar ratio of 1:2:3 and stirred until dispersed to obtain a mixture. The pretreated carbon felt was then immersed in the mixture for 10 min. The electrode was then removed to remove excess chitosan metal salt solution from its surface and placed in 1M NaOH solution for curing for 5 min. Finally, the cured electrode was placed in a 60°C oven for drying for 1 h to obtain the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material (Fe-Ni / CS@CF).

[0022] The morphology and structure of the prepared electrodes were characterized: Depend on Figure 1 (SEM image) As can be seen, the Fe-Ni bimetal is uniformly loaded on the surface of the chitosan-modified carbon felt, with a complete morphology, uniform dispersion, and no obvious agglomeration.

[0023] Depend on Figure 2 (X-ray diffraction pattern) shows that the Fe and Ni bimetallic species exist in amorphous or low-crystallinity form, with no obvious metal crystal diffraction peaks.

[0024] Depend on Figure 3 (X-ray photoelectron spectroscopy) confirms that both Fe and Ni exist in a coordinated state and are stably bound to the chitosan backbone through N / O coordination, without an independent crystalline phase.

[0025] The above results indicate that the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode has been successfully prepared.

[0026] Example 2:

[0027] The Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material prepared in Example 1 was placed in simulated phosphorus-containing wastewater containing 30 mg P / L. The pH of the system was adjusted, and static adsorption was performed under the same conditions for 48 h. The residual phosphorus concentration was then measured, and the results are as follows: Figure 4 As shown.

[0028] The results showed that the adsorption performance decreased significantly with increasing pH. The adsorption was optimal under acidic conditions (pH=3), with an adsorption capacity of about 7 mg P / L after 48 h. The adsorption capacity decreased significantly under neutral and alkaline conditions, far lower than that under acidic conditions.

[0029] Adsorption mechanism: Under acidic conditions, the amino protonation of chitosan generates electrostatic attraction with phosphate, while the Fe / Ni active center forms MOP inner sphere coordination bonds with phosphate, synergistically achieving efficient capture.

[0030] The adsorption data under pH=3 condition were fitted with an isothermal model, and the results are as follows: Figure 5 As shown: Freundlich model (R 2 =0.88) The fitting effect is better than the Langmuir model (R² = 0.88). 2 =0.82), indicating that the electrode surface has multiple active sites with uneven energy distribution, belonging to heterogeneous multilayer adsorption.

[0031] Example 3:

[0032] A Fe-Ni bimetallic chitosan-modified carbon felt composite cathode was adsorbed for 48 h under optimal adsorption conditions (pH=3) to construct a two-electrode system. This composite electrode served as the cathode, and the anode was a DSA electrode (ruthenium-iridium coated titanium-based electrode). Regeneration was performed at room temperature by applying a DC cathode bias of 3.0V-5.5V. The desorption efficiency results are as follows: Figure 6 As shown.

[0033] The results show that: After applying a cathode bias voltage, electrons accumulate on the cathode surface, generating a strong electrostatic repulsion force. Simultaneously, a deprotonation effect occurs at the interface, weakening the MOP coordination bonds and driving rapid phosphate desorption. At 5.5V, the desorption efficiency can reach 87%-93%, enabling efficient in-situ electrode regeneration.

[0034] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a bimetallic modified cathode, characterized in that, Includes the following steps: Chitosan was dissolved in glacial acetic acid solution and stirred at room temperature until completely dissolved. Then, iron salt precursor and nickel salt precursor were added and stirred until dispersed to obtain a mixture. The pretreated carbon felt was immersed in the mixture for 10 min. The electrode was then removed to remove excess chitosan metal salt solution from its surface and placed in 1M sodium hydroxide solution for curing at room temperature for 5 min. Finally, the cured electrode was placed in a 60°C oven for drying for 1 h to obtain Fe-Ni bimetallic chitosan modified carbon felt composite cathode material.

2. The method for preparing a bimetallic modified cathode according to claim 1, characterized in that, The ratio of chitosan to glacial acetic acid solution is 1g:0.5mL.

3. The method for preparing a bimetallic modified cathode according to claim 1, characterized in that, The iron salt precursor includes divalent iron salt and trivalent iron salt, wherein the divalent iron salt is FeCl2·4H2O and the trivalent iron salt is FeCl3·6H2O; the nickel salt precursor is NiCl2·6H2O.

4. The method for preparing a bimetallic modified cathode according to claim 3, characterized in that, The Fe provided by the divalent iron salt 2+ Fe provided by trivalent iron salts 3+ Ni provided by nickel salt precursor 2+ The molar ratio of the three components is 1:2:3, and the total amount of substance of the three components is 0.015 mol.

5. The Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material obtained by the preparation method of the bimetallic modified cathode according to any one of claims 1-4.

6. The application of the Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material according to claim 5 in phosphorus recovery.

7. A method for phosphorus recovery, characterized in that, Includes the following steps: (a) The Fe-Ni bimetallic chitosan-modified carbon felt composite cathode material as described in claim 5 is placed in phosphorus-containing wastewater and adsorbs phosphate under acidic conditions; (b) After adsorption is complete, a cathode bias voltage is applied to the bimetallic modified cathode to desorb and release the phosphate into a 0.1M Na2SO4 solution, thereby achieving in-situ regeneration of the cathode.

8. The method for phosphorus recovery according to claim 7, characterized in that, The cathode bias voltage is a DC voltage with a value of 3.0V-5.5V.

9. A method for phosphorus recovery according to claim 7, characterized in that, The acidic conditions are pH=3-5.

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