A light / pH dual-response bipyridyl-based supramolecular adsorbing material, a preparation method and application thereof

Abstract

This invention belongs to the field of new materials technology, specifically relating to a light / pH dual-responsive bipyridine-based supramolecular adsorbent material, its preparation method, and its application. The preparation method of this light / pH dual-responsive bipyridine-based supramolecular adsorbent material includes the following steps: dissolving azobenzene dicarboxylic acid monomer and bipyridine diamine monomer in a solvent to obtain a monomer mixture; adding a composite condensing agent to the monomer mixture for activation treatment; after activation treatment, stirring the reaction at 60–80°C for 8–12 hours under an inert gas atmosphere; after the reaction, dialysis of the reaction system; centrifugation of the dialyzed reaction system; collection of the precipitate; and drying of the precipitate to obtain the light / pH dual-responsive bipyridine-based supramolecular adsorbent material. The adsorbent material of this invention is effective against Cu... 2+ Ni 2+ Cd 2+ The saturated adsorption capacity is 40%-60% higher than that of conventional resins and activated carbon, and the selective removal rate of target heavy metal ions reaches over 95%. After deep treatment, the heavy metal content of wastewater can meet the discharge standards.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a light / pH dual-responsive bipyridine-based supramolecular adsorbent material, its preparation method, and its application. Background Technology

[0002] Currently, commonly used adsorbents for industrial heavy metal wastewater treatment mainly include activated carbon, ion exchange resins, biomass adsorbents, and inorganic nanomaterials. These materials rely on physical adsorption, electrostatic adsorption, or weak chelation to capture heavy metal ions and are widely used in wastewater treatment in industries such as electroplating and metallurgy. In recent years, supramolecular adsorbents have become a research hotspot in the field of heavy metal treatment due to their advantages of directional chelation and selective adsorption. However, existing supramolecular adsorbents generally suffer from single functionality and poor responsiveness. Most materials rely solely on a single chemical action to bind heavy metal ions, failing to achieve controllable adsorption and desorption.

[0003] The core pain points and shortcomings of existing technologies include: 1. Limited adsorption capacity and poor selectivity: Conventional adsorption materials lack specific heavy metal binding sites, and have limited selectivity for Cu. 2+ Ni 2+ Cd 2+ 1. Weak chelating ability of transition metal ions and low saturation adsorption capacity make it difficult to meet the requirements of deep treatment of high-concentration heavy metal wastewater, and it is easily interfered with by other ions in the water. 2. Difficult elution and regeneration, high energy consumption and heavy pollution: After the existing adsorbents are saturated, they need to be soaked and desorbed with high-concentration strong acids, strong alkalis or chelating agents. This not only consumes a lot of reagents and is costly, but also generates a large amount of high-salt and high-acid secondary wastewater, which damages the structure of the adsorbent and leads to rapid decline in its recycling performance. 3. Difficulty in heavy metal recovery and low purity: The heavy metal eluent obtained by traditional desorption methods has low concentration and many impurities, making it difficult to directly recover resources. Most of them need to be further concentrated, and the process is complicated, making it impossible to achieve efficient purification and recycling of heavy metals. 4. Lack of intelligent response characteristics and inability to accurately control: Existing materials cannot switch adsorption-desorption states autonomously according to external environmental signals. The adsorption and release process is uncontrollable, making it difficult to adapt to the flexible treatment needs under complex water quality conditions, and limiting the applicability of the technology. Summary of the Invention

[0004] To address the problems and shortcomings of existing technologies, this invention aims to provide a light / pH dual-responsive bipyridine-based supramolecular adsorbent material, its preparation method, and its applications.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for preparing a light / pH dual-responsive bipyridine-based supramolecular adsorbent material, comprising the following steps: Azobenzene dicarboxylic acid monomer and bipyridine diamine monomer are dissolved in a solvent to obtain a monomer mixture. A composite condensing agent is added to the monomer mixture for activation treatment. After activation treatment, the mixture is stirred at 60-80°C for 8-12 hours under an inert gas atmosphere. After the reaction is completed, the reaction system is dialyzed. The dialyzed reaction system is centrifuged, and the precipitate is collected. The precipitate is dried to obtain the light / pH dual-responsive bipyridine-based supramolecular adsorbent material.

[0006] Preferably, the composite condensing agent is composed of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide.

[0007] Preferably, the molar ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and azobenzene dicarboxylic acid monomer is (1.1-1.3):(0.9-1.1):1.0.

[0008] Preferably, the molar ratio of the azobenzene dicarboxylic acid monomer to the bipyridine diamine monomer is 1:1 to 1:1.5; the solvent is composed of anhydrous ethanol and dimethylformamide.

[0009] The second aspect of the present invention provides a light / pH dual-responsive bipyridine-based supramolecular adsorbent material prepared by the preparation method described in the first aspect above.

[0010] The third aspect of this invention provides the application of the light / pH dual-responsive bipyridine-based supramolecular adsorbent material described in the second aspect above in the treatment of heavy metal wastewater.

[0011] A fourth aspect of the present invention provides a method for treating heavy metal wastewater, comprising the following steps: The light / pH dual-responsive bipyridyl supramolecular adsorbent material described in the second aspect above is added to the heavy metal wastewater for adsorption treatment. After the adsorption treatment is completed, the light / pH dual-responsive bipyridyl supramolecular adsorbent material that adsorbs the heavy metals is separated to obtain purified wastewater.

[0012] Preferably, the specific conditions for the adsorption treatment are: adsorption is carried out at a pH of 5-7 and with stirring at room temperature.

[0013] The fifth aspect of this invention provides a method for regenerating a light / pH dual-responsive bipyridyl supramolecular adsorbent material, comprising the following steps: adding the light / pH dual-responsive bipyridyl supramolecular adsorbent material for adsorbing heavy metals as described in the fourth aspect above to water, treating it with ultraviolet light, and after the irradiation treatment is completed, obtaining a concentrated heavy metal solution and desorbed light / pH dual-responsive bipyridyl supramolecular adsorbent material; treating the desorbed light / pH dual-responsive bipyridyl supramolecular adsorbent material with visible light, and after the light irradiation is completed, obtaining regenerated light / pH dual-responsive bipyridyl supramolecular adsorbent material.

[0014] Preferably, the specific conditions for the ultraviolet light irradiation treatment are: irradiation with 300-365nm ultraviolet light for 10-30 minutes.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention provides a dual-response supramolecular adsorbent material, which forms a flexible main chain skeleton by covalently linking amide bonds. Two types of functional groups are simultaneously grafted onto the main chain, and the structure is precise and controllable. No additional skeleton monomers are added. The polymerized main chain of the functional monomers is the core skeleton of the supramolecular polymer, taking into account conformational flexibility, mechanical stability and uniform distribution of functional groups. Specifically, the design is as follows: ① Azobenzene photoresponsive group: As a light-controlled switching unit, an aromatic azobenzene derivative is selected and covalently grafted onto the supramolecular main chain. Under the alternating irradiation of ultraviolet light (300-365nm) and visible light of a specific wavelength, a reversible cis-trans isomerization transformation occurs, which directly drives the supramolecular polymer chain to undergo a reversible switching of coil-unwind conformation, resulting in dynamic changes in steric hindrance. Moreover, the structure of this group is stable under mild polymerization conditions and there is no risk of deactivation. ② Bipyridine functional group: It has both pH-responsive units and heavy metal-specific chelating sites. The nitrogen atom of bipyridine is in a protonation-deprotonation equilibrium state in the weakly acidic to neutral pH range (pH=5-7, suitable for most heavy metal wastewater conditions). The polymer chain is fully extended, exposing a large number of nitrogen chelating sites, forming stable coordination bonds with heavy metal ions. Under excessively acidic or alkaline conditions, the coordination effect is weakened, reserving room for controllable desorption. ③ Supramolecular polymer backbone: A flexible conjugated supramolecular backbone backbone is formed by the amide condensation of azobenzene dicarboxylic acid and bipyridine diamine. At the same time, the chains are cross-linked through hydrogen bonding, π-π stacking, and coordination. This ensures the flexibility of the material's conformational transformation, adapting to the core mechanism of light-controlled steric extrusion, while also improving the material's mechanical stability and water solubility / dispersibility, making it suitable for wastewater liquid phase treatment systems. Moreover, the backbone remains structurally intact after multiple cycles of use.

[0016] (2) In this invention, the prepared supramolecular adsorbent material is added to wastewater containing heavy metals, and the pH of the wastewater is adjusted to the optimal adsorption range of 5-7. At this time, the bipyridine group is in a deprotonated and extended state, the polymer chain is fully extended, and a large number of nitrogen atom chelation sites are fully exposed, like an open mousetrap, which reacts with Cu in the wastewater. 2+ Ni 2+ Cd 2+ When transition metal ions undergo directional coordination chelation, they rapidly form stable supramolecular-metal complexes, achieving highly efficient capture of heavy metal ions. This process is characterized by fast adsorption rate, high capacity, and strong selectivity, and is unaffected by common sodium, calcium, and magnesium ions in water. After adsorption saturation, the material does not require treatment with high-concentration strong acids or bases; only low-temperature irradiation with specific wavelength ultraviolet light (300-365nm) is needed. This causes the azophenyl groups within the material to rapidly undergo trans-cis isomerization, driving the entire supramolecular polymer chain to undergo intense coiling and contraction. A directional steric hindrance and compression effect is generated within the molecule, physically breaking the coordination bonds between bipyridine and heavy metal ions, actively "squeezing" the heavy metal ions from the chelation sites, thus achieving efficient separation of heavy metal ions from the adsorbent material. After desorption, switching to visible light irradiation causes the azophenyl groups to revert to their trans structure, the polymer chains to unwind, and the material to regain its initial adsorption performance, completing one full adsorption-desorption cycle.

[0017] (3) The present invention relates to Cu 2+ Ni 2+ Cd 2+ The saturated adsorption capacity is 40%-60% higher than that of conventional resins and activated carbon, and the selective removal rate of target heavy metal ions reaches over 95%. After deep treatment, the heavy metal content of the wastewater can meet the discharge standards. It abandons the traditional high-concentration strong acid and strong alkali desorption process, relying solely on light-controlled desorption. The desorption system uses only water or low-concentration weak acid (pH=3-4), significantly reducing chemical reagent consumption and eliminating the generation of high-salt, high-acid secondary wastewater. After more than 10 adsorption-desorption cycles, the material retains ≥90% of its adsorption capacity, with no structural damage, and the desorption efficiency remains consistently above 85%, far superior to conventional adsorbents (conventional materials experience performance degradation of over 50% after 3-5 cycles). The concentrated heavy metal solution obtained from light-controlled desorption has a high concentration and few impurities, requiring no complex purification treatment and can be directly used for electrolysis and precipitation recovery of high-purity metals, achieving a closed-loop resource recovery system. This mild amide polycondensation process, employing an EDC-HCl / NHS composite condensing agent, operates at a reaction temperature of 60-80℃. It eliminates the need for high-temperature, strong free radical initiators, fully compatibility with the structural characteristics of azobenzene and bipyridine functional groups, avoiding functional group deactivation. The process is simple, requires no special equipment, and is suitable for large-scale production. The adsorption-desorption process is precisely controlled via dual pH and light signals, making it adaptable to heavy metal wastewater of varying concentrations and pH levels. The process is easy to operate, energy-efficient, and suitable for continuous industrial treatment. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example 1

[0019] A method for preparing a light / pH dual-responsive bipyridine-based supramolecular adsorbent material, the specific steps of which are as follows: S1. Disperse 0.01 mol of azobenzene dicarboxylic acid monomer and 0.012 mol of bipyridine diamine monomer in a mixed solvent of anhydrous ethanol / dimethylformamide, and stir magnetically at room temperature until completely dissolved to obtain a monomer mixture; wherein the volume ratio of anhydrous ethanol to dimethylformamide is 1:1. S2. Add 0.012 mol of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.01 mol of N-hydroxysuccinimide to the above monomer mixture, and continue stirring at room temperature for 30 min to complete the carboxyl activation; S3. High-purity nitrogen gas is introduced into the activated monomer mixture for protection, and the mixture is stirred at a constant temperature of 70°C for 10 hours to complete the amide polycondensation reaction. S4. Transfer the reaction product to a dialysis bag with a molecular weight cutoff of 3500 Da, dialyze with deionized water for 48 h, and change the deionized water every 6 h. After dialysis, centrifuge at 8000 r / min for 10 min to collect the solid, and vacuum dry at 60 °C for 12 h to obtain the light / pH dual-responsive bipyridine-based supramolecular adsorbent material.

[0020] The specific steps of the method for treating heavy metal wastewater and regenerating light / pH dual-responsive bipyridine-based supramolecular adsorbents are as follows: A. Take 1L of Cu-containing solution with an initial concentration of 50mg / L. 2+ Simulated wastewater was used, and the pH was adjusted to 6. 0.1g of the light / pH dual-responsive bipyridine supramolecular adsorbent prepared in this embodiment was added. The mixture was stirred at room temperature for 60 minutes to adsorb the wastewater and the light / pH dual-responsive bipyridine supramolecular adsorbent that adsorbed heavy metals. Cu was detected in the purified wastewater. 2+ The concentration dropped to below 0.3 mg / L; B. The light / pH dual-responsive bipyridine supramolecular adsorbent material adsorbing heavy metals was filtered and separated, transferred to 50 mL of pure water, and irradiated with 365 nm ultraviolet light for 20 min. Cu 2+ The heavy metals were actively released into pure water to obtain a concentrated solution of heavy metals and a desorbed light / pH dual-responsive bipyridine supramolecular adsorbent. The Cu in the concentrated heavy metal solution was then detected. 2+ The concentration reached 92 mg / L; C. Irradiate the desorbed light / pH dual-responsive bipyridine supramolecular adsorbent material obtained in step B with visible light for 10 min to obtain the regenerated light / pH dual-responsive bipyridine supramolecular adsorbent material.

[0021] After repeating steps AC above for 10 cycles, the adsorption capacity of the regenerated light / pH dual-response bipyridine supramolecular adsorbent material still reached 168 mg / g, with a capacity retention rate of 90.3%. Example 2

[0022] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that in step S1, the molar ratio of azobenzene dicarboxylic acid monomer to bipyridine diamine monomer is 1:1.0.

[0023] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 3

[0024] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that in step S1, the molar ratio of azobenzene dicarboxylic acid monomer to bipyridine diamine monomer is 1:1.1.

[0025] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 4

[0026] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that in step S1, the molar ratio of azobenzene dicarboxylic acid monomer to bipyridine diamine monomer is 1:1.3.

[0027] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 5

[0028] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that in step S1, the molar ratio of azobenzene dicarboxylic acid monomer to bipyridine diamine monomer is 1:1.5.

[0029] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used.

[0030] Performance testing: 1. Method for determining saturated adsorption capacity: Prepare a series of Cu concentrations (10–200 mg / L) 2+ Ni 2+ or Cd 2+ Simulated heavy metal wastewater was prepared, and the pH was adjusted to 5–7. A certain volume V (L) of wastewater was taken, and a mass m (g) of adsorbent material was added. The mixture was stirred at room temperature until adsorption equilibrium was reached (approximately 60 min). After filtration, the initial concentration was determined using atomic absorption spectrophotometry (AAS) or inductively coupled plasma mass spectrometry (ICP-MS). C 0 (mg / L) and equilibrium concentration C e (mg / L). Calculate the saturated adsorption capacity. The formula for calculating the saturated adsorption capacity is as follows:

[0031] In the formula: Q e : Saturated adsorption capacity, mg / g; CO: Initial concentration of heavy metal, mg / L; C e : Concentration of heavy metals at adsorption equilibrium, mg / L; V Wastewater volume, L; m : Mass of adsorbent material added, g.

[0032] 2. Desorption efficiency detection method: Take the material that is saturated with adsorption and add a certain volume V In 1 L of deionized water, irradiate with 300–365 nm ultraviolet light for 10–30 min; filter, and determine the concentration of heavy metals in the desorbate. C d (mg / L); the desorption efficiency is calculated based on the saturated adsorption capacity. The formula for calculating the desorption efficiency is as follows:

[0033] In the formula: η: desorption efficiency, % C d : Concentration of heavy metals in the desorption solution, mg / L; V 1: Desorption volume, L; Q e : Saturated adsorption capacity, mg / g; m Mass of adsorption saturated material, in grams.

[0034] The saturated adsorption capacity and desorption efficiency of Examples 1-5 of the present invention were calculated, and the results are shown in Table 1.

[0035] Table 1. Saturated adsorption capacity and desorption efficiency of Examples 1-5

[0036] As shown in Table 1, with the increase of the molar ratio of bipyridine diamine, the saturated adsorption capacity of the material first increases and then decreases, while the desorption efficiency continues to decline. When the molar ratio is 1:1.0 to 1:1.2, with the increase of the amount of bipyridine groups introduced, the number of N coordination sites on the polymer chain increases, the chelation effect on heavy metal ions is enhanced, and the saturated adsorption capacity increases from 172.5 mg / g to 186.2 mg / g. When the molar ratio exceeds 1:1.2 (1:1.3 to 1:1.5), the excess bipyridine diamine leads to excessive cross-linking of the polymer, increased chain rigidity, and increased unreacted monomer residue, which in turn causes the effective chelation sites to be buried, resulting in a decrease in adsorption capacity. In addition, excessive cross-linking also restricts the photo-induced isomerization of azophenyl groups, causing the photo-controlled desorption efficiency to decrease from 91.5% to 86.2%. Therefore, the preferred molar ratio of azobenzene dicarboxylic acid to bipyridine diamine is 1:1.2, at which point the material has both high adsorption capacity and high photo-controlled desorption efficiency. Example 6

[0037] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction temperature in step S3 is 60℃.

[0038] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 7

[0039] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction temperature in step S3 is 65℃.

[0040] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 8

[0041] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction temperature in step S3 is 75℃.

[0042] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 9

[0043] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction temperature in step S3 is 80℃.

[0044] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used.

[0045] The saturated adsorption capacity and desorption efficiency of Examples 6-9 of the present invention were calculated, and the results are shown in Table 2.

[0046] Table 2. Saturated adsorption capacity and desorption efficiency of Examples 6-9

[0047] Table 2 shows that the reaction temperature has a significant impact on the material properties, with a clear optimal range: at lower temperatures (60–65℃), the polycondensation reaction rate is slow, the polymer molecular weight distribution is wide, and the chain segment regularity is poor, resulting in insufficient exposure of chelating sites and a saturated adsorption capacity of only 165.3–179.5 mg / g; when the temperature rises to 70℃, the reaction rate is moderate, the polymer chain segment regularity is high, and both the bipyridine chelating sites and the azobenzene photoresponsive groups are effectively distributed, with the saturated adsorption capacity reaching 186.5 mg / g and the photocontrolled desorption efficiency remaining at a relatively high level of 91.6%; when the temperature continues to rise (75–80℃), side reactions (such as amide bond hydrolysis and polymer thermal degradation) are prone to occur, leading to an increase in structural defects in the material and partial deactivation of photoresponsive groups, resulting in a simultaneous decrease in adsorption capacity and desorption efficiency. Therefore, the preferred reaction temperature is 70℃, at which the reaction efficiency and material properties achieve the best balance. Example 10

[0048] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction time in step S3 is 8 hours.

[0049] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 11

[0050] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction time in step S3 is 9 hours.

[0051] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 12

[0052] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction time in step S3 is 11 h.

[0053] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used. Example 13

[0054] The preparation method of a light / pH dual-responsive bipyridine-based supramolecular adsorbent material is basically the same as that in Example 1, except that the reaction time in step S3 is 12h.

[0055] The method for treating heavy metal wastewater and regenerating the light / pH dual-responsive bipyridine supramolecular adsorbent material is basically the same as in Example 1, except that the light / pH dual-responsive bipyridine supramolecular adsorbent material prepared in this example is used.

[0056] The saturated adsorption capacity and desorption efficiency of Examples 10-13 of the present invention were calculated, and the results are shown in Table 3.

[0057] Table 3. Saturated adsorption capacity and desorption efficiency of Examples 10-13

[0058] Table 3 shows that the effect of reaction time on material properties exhibits a "first increase, then decrease" trend: when the reaction time is insufficient (8–9 h), the condensation reaction is incomplete, the polymer molecular weight is low, the chain segment length is insufficient, a stable supramolecular network structure cannot be formed, the number of effective chelating sites is limited, and the saturated adsorption capacity is only 170.6–182.3 mg / g; when the reaction time is 10 h, the condensation reaction is basically completed, the polymer chain segments grow fully, forming a stable supramolecular network with uniform site distribution, the saturated adsorption capacity reaches 186.3 mg / g, and the photocontrolled desorption efficiency is maintained at 91.4%; when the reaction time is too long (11–12 h), excessive condensation or chain segment crosslinking is prone to occur, resulting in the embedding of some chelating sites, and the photoresponsive activity of the azophenyl group decreases due to the increased chain segment rigidity, and the desorption efficiency drops below 89.2%. Therefore, a reaction time of 10 h is preferred, as the reaction is sufficient and the material properties are optimal at this time. Example 14

[0059] The adsorbent material was prepared using the optimal process described in Example 1. An initial concentration of Cu was prepared at 50 mg / L. 2+ Simulated wastewater was used, with pH adjusted to 3, 4, 5, 6, 7, and 8 respectively. 1 L of wastewater was taken from each sample, and 0.1 g of adsorbent material was added. The mixture was stirred and adsorbed at room temperature for 60 min. The remaining Cu was then measured after filtration. 2+ Concentration was used to calculate the saturated adsorption capacity and removal rate, and the results are shown in Table 4.

[0060] Table 4 Adsorption performance at different pH values

[0061] As shown in Table 4, the optimal adsorption range is pH 5–7, and the adsorption capacity and removal rate are highest at pH 6. Example 15

[0062] The adsorbent material was prepared using the optimal process described in Example 1. Cu with an initial concentration of 50 mg / L was prepared separately. 2+ Ni 2+ Cd 2+ Single ion simulated wastewater: 1 L of wastewater was taken from each sample, pH was adjusted to 6, 0.1 g of adsorbent material was added, and the sample was stirred and adsorbed at room temperature for 60 min. The remaining ion concentration was measured after filtration, and the saturated adsorption capacity and removal rate were calculated. The results are shown in Table 5.

[0063] Table 5. Saturated adsorption capacity for different heavy metal ions

[0064] Table 5 shows that the material affects Cu 2+ Ni 2+ Cd 2+They all have high adsorption capacity and removal rate, and are widely applicable. Example 16

[0065] The adsorbent material was prepared using the optimal process described in Example 1; granular activated carbon (GAC), strongly acidic cation exchange resin, and chitosan adsorbent were selected as comparative materials. Cu with an initial concentration of 50 mg / L and pH=6 was prepared. 2+ Simulated wastewater: 1 L of wastewater was taken from each sample, and 0.1 g of different adsorbent materials were added to each sample. The samples were adsorbed at room temperature for 60 min, and the saturated adsorption capacity was measured. The samples were then treated according to their respective conventional regeneration methods, and the cycle was repeated 10 times. The capacity retention rate was measured. The results are shown in Table 6.

[0066] Table 6. Performance Comparison with Conventional Adsorption Materials

[0067] As shown in Table 6, the material of the present invention has higher adsorption capacity, greener regeneration, and significantly better cycle stability than conventional materials. Example 17

[0068] Take the adsorbed saturated Cu from Example 1 2+ Five portions of the material (0.1 g each) were placed in 50 mL of deionized water and irradiated with ultraviolet light at 300 nm, 320 nm, and 365 nm for 20 min. The Cu content in the desorption solution was then determined by filtration. 2+ Concentration was used to calculate desorption efficiency, and the results are shown in Table 7.

[0069] Table 7. Effect of ultraviolet light wavelength on desorption efficiency (irradiation for 20 min)

[0070] As shown in Table 7, the 365 nm ultraviolet light has the highest desorption efficiency and is the optimal wavelength. Example 18

[0071] Take the adsorbed saturated Cu from Example 1 2+ Four portions of the material (0.1 g each) were placed in 50 mL of deionized water and irradiated with 365 nm ultraviolet light for 5 min, 10 min, 20 min, and 30 min, respectively. The Cu content in the desorption solution was then determined by filtration. 2+ Concentration was used to calculate desorption efficiency, and the results are shown in Table 8.

[0072] Table 8 Effect of irradiation time on desorption efficiency (365 nm)

[0073] As shown in Table 8, the desorption efficiency reaches its peak after 20 minutes of irradiation, which is the optimal time.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention based on the concept of the present invention, without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a light / pH dual-responsive bipyridine-based supramolecular adsorbent material, characterized in that, Includes the following steps: Azobenzene dicarboxylic acid monomer and bipyridine diamine monomer are dissolved in a solvent to obtain a monomer mixture. A composite condensing agent is added to the monomer mixture for activation treatment. After activation treatment, the mixture is stirred at 60-80°C for 8-12 hours under an inert gas atmosphere. After the reaction is completed, the reaction system is dialyzed. The dialyzed reaction system is centrifuged, and the precipitate is collected. The precipitate is dried to obtain the light / pH dual-responsive bipyridine-based supramolecular adsorbent material.

2. The method for preparing the light / pH dual-responsive bipyridine-based supramolecular adsorbent material according to claim 1, characterized in that, The composite condensing agent consists of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide.

3. The method for preparing the light / pH dual-responsive bipyridine-based supramolecular adsorbent material according to claim 2, characterized in that, The molar ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and azobenzene dicarboxylic acid monomer is (1.1-1.3):(0.9-1.1):1.

0.

4. The method for preparing the light / pH dual-responsive bipyridine-based supramolecular adsorbent material according to any one of claims 1-3, characterized in that, The molar ratio of the azobenzene dicarboxylic acid monomer to the bipyridine diamine monomer is 1:1 to 1:1.5; the solvent is composed of anhydrous ethanol and dimethylformamide.

5. A light / pH dual-responsive bipyridine-based supramolecular adsorbent material prepared by any one of the preparation methods described in claims 1-4.

6. The application of the light / pH dual-responsive bipyridine-based supramolecular adsorbent material according to claim 5 in the treatment of heavy metal wastewater.

7. A method for treating heavy metal wastewater, characterized in that, Includes the following steps: The light / pH dual-responsive bipyridyl supramolecular adsorbent material described in claim 5 is added to heavy metal wastewater for adsorption treatment. After the adsorption treatment is completed, the light / pH dual-responsive bipyridyl supramolecular adsorbent material that adsorbs heavy metals is separated to obtain purified wastewater.

8. The method for treating heavy metal wastewater according to claim 7, characterized in that, The specific conditions for the adsorption treatment are as follows: adsorption is carried out at a pH of 5-7 and under stirring at room temperature.

9. A method for regenerating a light / pH dual-responsive bipyridine-based supramolecular adsorbent material, characterized in that, The process includes the following steps: adding the light / pH dual-responsive bipyridine supramolecular adsorbent material for adsorbing heavy metals as described in claim 7 into water, treating it with ultraviolet light, and after the irradiation treatment is completed, obtaining a concentrated solution of heavy metals and the desorbed light / pH dual-responsive bipyridine supramolecular adsorbent material; The desorbed light / pH dual-responsive bipyridyl supramolecular adsorbent material was subjected to visible light irradiation. After the irradiation ended, the regenerated light / pH dual-responsive bipyridyl supramolecular adsorbent material was obtained.

10. The regeneration method for the light / pH dual-responsive bipyridine-based supramolecular adsorbent material according to claim 9, characterized in that, The specific conditions for the ultraviolet light irradiation treatment are: irradiation with 300-365nm ultraviolet light for 10-30 minutes.

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