A phenolic resin adsorbing material, a preparation method thereof and application thereof in heavy metal wastewater field

Abstract

The application discloses a phenolic resin adsorption material, and a structural general formula thereof is as follows: I; wherein n is an integer of 2-20; and each of R1 and R2 is independently selected from CH2 and CH2-O-CH2. The phenolic resin adsorption material has excellent stability in water, excellent heavy metal ion adsorption performance and recycling performance, and is prepared by taking gallic acid and formaldehyde as main raw materials and combining a pH gradient regulation process based on alkaline polycondensation-acidification curing. The phenolic resin adsorption material can provide a new idea for preparation of high-performance adsorption materials.

Description

Technical Field

[0001] This invention belongs to the field of adsorption materials and water pollution control technology, specifically relating to a phenolic resin adsorption material, its preparation method, and its application in the field of heavy metal wastewater. Background Technology

[0002] Phenolic resins possess good thermal, chemical, and mechanical stability and are widely used in electrical laminates, carbon foam, adhesives, molding compounds, acid-resistant coatings, and fiber-reinforced composites. Traditional phenolic resins are typically obtained through the condensation polymerization of phenol, formaldehyde, or other phenolic and aldehyde compounds. Common systems include methyl phenolic resins formed under alkaline conditions and linear phenolic resins formed under acidic conditions.

[0003] In the field of heavy metal wastewater treatment, adsorption methods have attracted attention due to their simple operation and wide applicability. However, existing resin-based or carbon-based adsorption materials still suffer from insufficient active site density, narrow pH adaptability, and the coexistence of Na+. + K + Ca 2+ Mg 2+ Significant issues arise from plasma interference, decreased adsorption capacity after regeneration, and reliance on toxic phenolic monomers or organic solvents in the material preparation process. In particular, heavy metal ions such as Pb(II) in water can coordinate with oxygen-containing functional groups, but are also affected by hydrolysis precipitation and competing ions. Therefore, adsorption materials must possess high water stability, abundant and accessible oxygen donor sites, and good regeneration performance.

[0004] In the prior art, phenolic resin-based heavy metal water treatment materials have been reported, such as CN106186165A which discloses a heavy metal wastewater treatment material based on plant-modified phenolic resin. Although the above technologies disclose the applicability of polyphenol structures or phenolic resins in the materials field, the formulation systems involved are relatively complex and cannot effectively achieve high selectivity, high removal rate, and multiple recycling characteristics at the same time.

[0005] Therefore, there is an urgent need to further explore adsorbent materials that are simple to prepare, have high active site density, and have good treatment effects on lead-containing wastewater and other heavy metal wastewater that can coordinate with oxygen-containing functional groups. Summary of the Invention

[0006] One of the objectives of this invention is to address the shortcomings of existing adsorption materials, such as insufficient active sites, limited adaptability to pH and coexisting ions, insufficient regeneration stability, and the difficulty in regulating existing bio-based phenolic resins for heavy metal wastewater adsorption. This invention provides a phenolic resin adsorption material that, by bridging gallic acid and formaldehyde, forms a cross-linked resin framework with water-insoluble and abundant oxygen-containing functional groups, thereby achieving efficient removal of heavy metal ions.

[0007] The second objective of this invention is to provide a method for preparing the above-mentioned phenolic resin adsorbent material, which uses an aqueous system and a stepwise pH control process to promote the activation, condensation and efficient precipitation of gallic acid-modified resin; it avoids the use of traditional phenol sources and achieves efficient removal of free formaldehyde and soluble small molecule residues through simple washing and drying post-treatment processes (this invention does not completely eliminate the use of aldehydes, but uses formaldehyde as a bridging reaction raw material to participate in the condensation reaction and removes unreacted residues in the post-treatment stage).

[0008] The third objective of this invention is to provide the application of the above-mentioned phenolic resin adsorbent material in the treatment of heavy metal wastewater.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A phenolic resin adsorbent material is a cross-linked phenolic resin formed by the condensation polymerization of gallic acid and formaldehyde, denoted as GA / FM resin; wherein GA represents the structural unit corresponding to gallic acid or its hydrate, and FM represents the methylene and / or methylene ether bridging structural unit formed by the condensation polymerization of formaldehyde; the general structural formula of the GA / FM resin is shown in Formula I. I; In the formula, n is the number of repeating units, which is an integer from 2 to 20, preferably 5 to 16, and more preferably 8 to 12; and Choose one of CH2 or CH2-O-CH2 independently.

[0010] Furthermore, the number-average molecular weight of the phenolic resin adsorbent material is 500-4000 Da, preferably 1000-3000 Da.

[0011] Furthermore, the phenolic resin adsorbent material is a brownish-red solid, specifically in the form of layers, sheets, particles, or a combination thereof; its surface contains oxygen-containing functional groups such as CO, C=O, OC=O, and -OH, among which the carboxyl and phenolic hydroxyl groups can act as electron donors to form Pb-O or Pb-OOC coordination structures with Pb(II), thereby achieving surface complexation, coordination fixation, and ion exchange of Pb(II); at the same time, under certain conditions, oxygen-containing functional groups such as phenolic hydroxyl groups can participate in the redox process, causing some Pb(II) to be converted into zero-valent lead Pb(O) or other low-mobility lead species, which are then fixed on the resin surface, thereby achieving the removal of Pb(II).

[0012] The preparation method of the above-mentioned phenolic resin adsorbent material includes the following steps: 1) Under water bath and reflux conditions, gallic acid or gallic acid hydrate is added to water and heated to dissolve; formaldehyde aqueous solution is added to the obtained gallic acid solution, and an alkalinity regulator is added to adjust the reaction system to alkalinity; 2) The heating condensation reaction is carried out under continuous stirring to bridge the gallic acid units with formaldehyde, and then the mixture is allowed to cool naturally to room temperature. 3) Add acid to the reaction solution obtained in step 2) to adjust to acidity, let stand, so that the polycondensation product can be further solidified, precipitated and form a water-insoluble resin; 4) Filter the reaction system obtained in step 3), wash it with water until it is neutral and / or there is no obvious free reactant residue, and then dry it (freeze-dry or vacuum-dry) to obtain the phenolic resin adsorbent material.

[0013] In the above method, gallic acid is first dissolved by heating in a water bath, and formaldehyde is added under alkaline conditions to promote the acquisition of phenolic resin with a layered structure.

[0014] In the above scheme, the water bath temperature in step 1) is 50-70℃, more preferably 55-65℃, and even more preferably 60℃; the heating and dissolving time is 3-30 min, preferably 5-15 min.

[0015] In the above scheme, the molar ratio of gallic acid to formaldehyde (CH2OH) in step 1) is 1:(3.0-8.0), more preferably 1:(4.0-7.0), and even more preferably 1:(4.5-6.5).

[0016] In the above scheme, the concentration of the formaldehyde aqueous solution is 35-40 wt%.

[0017] In the above scheme, the alkaline regulator is one or more of sodium hydroxide solution and potassium hydroxide solution; the concentration of the alkaline regulator is 20-60 wt%, preferably 40-55 wt%, more preferably 50 wt%; the pH value of the reaction system in step 1) is adjusted to 9.0-11.0, preferably 9.5-10.5, more preferably 10.0.

[0018] In the above scheme, the temperature used for the heating polycondensation reaction in step 2) is 65-85℃, preferably 70-80℃, more preferably 75℃; the reaction time is 60-180 min, preferably 90-150 min, more preferably 120 min; the stirring speed can be 100-500 rpm, preferably 120-300 rpm.

[0019] In the above scheme, the acid solution mentioned in step 3) is one or more of nitric acid, hydrochloric acid, acetic acid, etc., preferably nitric acid; the acid concentration is 20-65 wt%, preferably 50-60 wt%; the pH value is adjusted to 1.5-3.0 in step 3), preferably 1.8-2.5, more preferably 2.0; the standing time is 10-90 min, preferably 20-60 min, more preferably 30 min.

[0020] In the above scheme, the washing time in step 4) shall be no less than 3 times, and the freeze-drying time shall be 12-48 h, preferably 24 h; vacuum drying at 40-70℃ can also be used instead of freeze-drying, but it is preferable to maintain the pores and layered structure of the material.

[0021] This invention also provides a method for controlling the ratio of GA units to FM bridging units and the degree of crosslinking in phenolic resin adsorbent materials: by adjusting the molar ratio of gallic acid to formaldehyde, the alkalinization pH (step 1), the polymerization temperature, the polymerization time, and the acidification pH (step 3), the resulting resin is made insoluble in water and retains a high density of carboxyl and phenolic hydroxyl sites. Preferably, the resin is prepared under the following conditions: a GA:FM molar ratio of 1:(4.5-6.5), an alkalinization pH of 9.5-10.5, a polymerization temperature of 70-80℃, a polymerization time of 90-150 min, and an acidification pH of 1.8-2.5.

[0022] This invention also provides the application of the above-mentioned phenolic resin adsorbent material in heavy metal wastewater treatment, comprising the following steps: 1) Obtain the wastewater containing heavy metals to be treated, and determine the concentration of the target heavy metal ions and pH; 2) Add phenolic resin adsorbent material to the heavy metal wastewater to be treated at a dosage of 0.5-10 g / L, preferably 0.5-2 g / L, more preferably 1 g / L; 3) Adsorption treatment at 15-45℃, preferably 25-45℃, for 30-240 min, preferably 120-240 min; after solid-liquid separation, treated water is obtained.

[0023] Furthermore, the heavy metal wastewater is preferably lead-containing wastewater; the initial concentration of Pb(II) in the lead-containing wastewater can be 10-1000 mg / L, preferably 50-1000 mg / L.

[0024] Furthermore, the heavy metal wastewater also contains one or more of Cu(II), Cd(II), Zn(II), Ni(II), etc.

[0025] Furthermore, the pH value of the heavy metal wastewater to be treated is adjusted to 3-6, preferably 4-6, and more preferably 5.0.

[0026] For actual low-concentration lead-containing wastewater, the dosage can be adjusted according to the influent concentration, discharge limits, and contact time.

[0027] Furthermore, the adsorption application steps for Pb(II)-containing wastewater include: A) Preparation of GA / FM resin adsorption material; B) Obtain wastewater samples containing Pb(II) and determine the Pb(II) concentration using inductively coupled plasma atomic emission spectrometry or other heavy metal detection methods; C) Detect the pH of the wastewater. If the pH is not within the range of 3-6, adjust it to 3-6, preferably to 4-6. D) Conduct small-scale tests based on Pb(II) concentration, resin dosage, and contact time to determine the appropriate GA:FM material ratio and resin dosage; wherein, the mass-to-volume ratio of gallic acid monohydrate to formaldehyde solution is 5 g : 10~15 mL, preferably 5 g : 12 mL; calculated based on the effective formaldehyde component, the molar ratio of gallic acid structural units to formaldehyde is 1:5.0~7.0, preferably 1:5.5~6.5; the resin dosage is 0.2~5.0 g / L, preferably 0.5~2.0 g / L, more preferably 1.0 g / L; E) Add GA / FM resin under defined conditions to wastewater containing Pb(II) to remove Pb(II) from the water through synergistic effects such as coordination, ion exchange, electrostatic attraction and redox.

[0028] The present invention also provides a method for recycling the above-mentioned phenolic resin adsorbent material, comprising the following steps: 1) Add the phenolic resin adsorbent material after adsorption treatment to a nitric acid solution and shake to desorb; 2) Filter, wash, and collect the regenerated phenolic resin adsorbent material; 3) The regenerated phenolic resin adsorbent material is added back into the heavy metal wastewater for heavy metal adsorption treatment.

[0029] Furthermore, the concentration of the nitric acid solution is 0.1~0.2 mol / L.

[0030] Furthermore, the oscillation desorption time is 5-7 hours.

[0031] Furthermore, after five adsorption-desorption cycles, the phenolic resin adsorbent material of the present invention can still maintain a Pb(II) removal rate of approximately 82%.

[0032] The principles of this invention include the following: This invention uses gallic acid and formaldehyde as the main raw materials, combined with a pH gradient control process based on alkaline polycondensation-acidification curing, to prepare phenolic resin adsorbent materials with excellent adsorption performance: In the alkaline polycondensation stage, the adjacent phenolic hydroxyl and carboxyl groups in the gallic acid molecule are retained as high-density oxygen donor sites on the resin backbone, and formaldehyde provides methylene or methylene ether bridging structures, enabling the material to form a water-insoluble cross-linked network; In the acidification stage, the polycondensation product precipitates and solidifies into a layered or granular solid, significantly improving its water stability and helping to retain active sites that can interact with heavy metal ions.

[0033] During adsorption, the carboxyl and phenolic hydroxyl groups undergo partial deprotonation with increasing pH, forming sites such as -COO- and -O-, which can undergo surface coordination and ion exchange with Pb(II), while releasing H+. + Furthermore, adjacent phenolic hydroxyl groups can undergo electron transfer in the presence of Pb(II), causing some Pb(II) to be reduced and fixed on the material surface. These effects collectively improve the Pb(II) removal capacity and the resistance to interference from coexisting ions.

[0034] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention takes GA / FM resin material itself as the core, uses gallic acid to replace traditional phenol as the main phenol source, and formaldehyde as a bridging agent to participate in the polycondensation reaction. Unreacted residual components are removed through simple post-treatment steps such as washing and drying, thereby reducing dependence on toxic phenol monomers.

[0035] 2) This invention uses a pH gradient control process based on "alkaline polycondensation-acidification curing" to obtain water-insoluble layered / particulate crosslinked resin. Its structure has a high density of oxygen-containing functional groups such as carboxyl groups, phenolic hydroxyl groups, carbonyl groups, and ether bonds, which are suitable as adsorption sites for heavy metal ions such as Pb(II).

[0036] 3) Based on abundant active sites and multiple adsorption mechanisms such as coordination, ion exchange, electrostatic attraction, and redox, this invention can achieve efficient removal of heavy metal ions such as Pb(II), and can provide a new approach for the preparation of high-performance adsorption materials.

[0037] 4) The material of this invention exhibits pH-responsive adsorption characteristics for Pb(II) within a pH range of 3-6; furthermore, in Na... + K + Ca 2+ Mg 2+ It can maintain a high Pb(II) selective removal effect even under coexisting ion conditions, making it suitable for complex water quality and other fields.

[0038] 5) The phenolic resin adsorbent material described in this invention has reusability after acid washing and regeneration, and has a better recycling effect. Attached Figure Description

[0039] Figure 1 This is a scanning electron microscope (SEM) image of the phenolic resin obtained in Example 1; Figure 2 The X-ray photoelectron spectroscopy (XPS) spectra of the phenolic resin obtained in Example 1 before and after treatment with Pb(II). Figure 3 The infrared spectrum analysis diagram of the phenolic resin obtained in Example 1; Figure 4 The infrared spectrum analysis diagram of the phenolic resin obtained in Example 2; Figure 5 The infrared spectrum analysis diagram of the phenolic resin obtained in Example 3; Figure 6 The graph shows the adsorption performance of the phenolic resin adsorbent material obtained in Example 1 on Pb(II) under different pH conditions in Example 1. Figure 7 The graph shows the adsorption performance of the phenolic resin adsorbent material obtained in Example 1 on Pb(II) under different temperature conditions in Example 1. Figure 8 The graph shows the adsorption performance of the phenolic resin adsorbent material obtained in Example 1 on Pb(II) using other coexisting ions in Example 1. Figure 9 The graph shows the cycle performance of the phenolic resin adsorbent material obtained in Example 1 of Application Example 1 for the adsorption-desorption of Pb(II). Detailed Implementation

[0040] The technical solutions adopted in this invention will be clearly and specifically described below through embodiments and comparative examples. These embodiments and comparative examples are merely illustrative examples of this invention and do not represent all embodiments, nor do they limit the scope of this invention. The embodiments in this invention, as well as various modifications or alterations made by those skilled in the art based on this invention, are also within the scope of protection of this invention.

[0041] In the following examples, gallic acid can be gallic acid monohydrate or anhydrous gallic acid; formaldehyde is preferably a 35-40 wt% formaldehyde aqueous solution, specifically a 37 wt% formaldehyde aqueous solution; the reagents used are preferably analytical grade or industrial grade after purification. The Pb(II) stock solution can be prepared from Pb(NO3)2, and the Pb(II) concentration can be determined by ICP-AES, ICP-MS, atomic absorption spectrometry, or equivalent methods.

[0042] Furthermore, the reaction routes in some embodiments of the present invention are shown in Formula II; II.

[0043] Example 1 A phenolic resin adsorbent material (GA / FM resin) is prepared by the following steps: 1) Add 10 ml of distilled water to a round-bottom flask equipped with a reflux condenser, preheat in a 60°C water bath for 5 min, add 5 g of gallic acid monohydrate, and keep at 60°C until it is completely dissolved. 2) Add 12 mL of 37 wt% formaldehyde aqueous solution (GA:FM molar ratio 1:6) to the gallic acid solution obtained in step 1), and adjust the pH of the resulting reaction solution to 10.0 using 50 wt% sodium hydroxide solution; 3) Under continuous stirring (stirring speed of 120 rpm), raise the water bath temperature to 75℃, react for 120 min, and then allow it to cool naturally to room temperature; 4) Add a 60 wt% nitric acid solution to the reaction solution obtained in step 3) to adjust the pH value to 2, let it stand for 30 minutes, and solidify to precipitate the resin product. 5) Filter the product obtained in step 4), wash the resulting solid three times with deionized water, and then freeze-dry for 24 h to obtain a brown phenolic resin adsorbent material.

[0044] Figure 1 The image shows a scanning electron microscope (SEM) analysis of the phenolic resin obtained in this embodiment; it can be seen that the phenolic resin material contains particulate and layered structures.

[0045] Figure 2 The X-ray photoelectron spectroscopy (XPS) spectra of the phenolic resin obtained in this embodiment before and after treatment with Pb(II) are shown. It can be seen that no characteristic peaks of Pb were found on the original phenolic resin material, but characteristic peaks of Pb were detected on the phenolic resin material after treatment with Pb(II), indicating that the phenolic resin material has the function of adsorption treatment of Pb(II).

[0046] Example 2 A phenolic resin adsorbent material is prepared in a manner that is basically the same as in Example 1, except that: the amount of gallic acid monohydrate is 5 g, the amount of formaldehyde aqueous solution added is GA:FM in a molar ratio of 1:4.5, the alkalization pH is adjusted to 9.5, the polycondensation temperature is 70℃, the reaction time is 150 min, the acidification pH is adjusted to 2.0, and the mixture is allowed to stand for 30 min.

[0047] The resulting adsorbent material, after washing and drying, is a brownish-brown solid powder, which can be used as an adsorbent material for GA / FM resin under low formaldehyde dosage conditions.

[0048] Characterized by FTIR (see Figure 3 The material obtained in Example 2 is in the range of 3700-3000 cm. -1 The stretching vibration of a carboxyl OH or phenolic hydroxyl OH group occurs at 1702 cm⁻¹. -1 It has a carboxyl C=O absorption peak at 1592 cm⁻¹. -1 It has an aromatic skeleton C=C absorption peak at 1351 cm⁻¹. -1 It has a CH-related absorption peak at 1109 cm⁻¹. -1The presence of COC-related absorption indicates that the obtained resin product contains abundant carboxyl, phenolic hydroxyl, carbonyl, and ether bond structures.

[0049] Example 3 A GA / FM phenolic resin adsorbent material was prepared using a method essentially the same as in Example 1, except that: the amount of gallic acid monohydrate used was 5 g; the amount of formaldehyde aqueous solution added was calculated based on a GA:FM molar ratio of approximately 1:6.5; the alkalization pH was adjusted to 10.5; the polymerization temperature was 80℃; the reaction time was 90 min; the acidification pH was adjusted to 2.5; and the mixture was allowed to stand for 45 min. The resulting material, after washing and drying, was a brownish-red solid powder, which can be used as a GA / FM resin adsorbent material under high crosslinking conditions.

[0050] Characterized by FTIR (see Figure 5 The material obtained in Example 3 is at a depth of 3600-3100 cm. -1 The stretching vibration of a carboxyl OH or phenolic hydroxyl OH group occurs at 1711 cm⁻¹. -1 It has a carboxyl C=O absorption peak at 1618 cm⁻¹. -1 It has an aromatic skeleton C=C absorption at 1468 cm⁻¹ -1 It has a COO-related vibrational peak at 1299 cm⁻¹. -1 The phenolic hydroxyl group (OH) and CO-related absorption are present at 1103 cm⁻¹. -1 The presence of COC-related absorption indicates that the resin surface contains abundant carboxyl, phenolic hydroxyl, carbonyl, and ether bond structures.

[0051] Application Example 1 Pb(II) adsorption performance test The phenolic resin adsorbent obtained in Example 1 was used for Pb(II) adsorption, wherein the initial concentration of Pb(II) solution was 100 mg / L, the amount of adsorbent added was 1 g / L, the temperature was 25℃, the pH was 5.0, and the adsorption time was 240 min.

[0052] The results show that the removal rate of Pb(II) using the adsorption process described in this invention reaches 97%.

[0053] Further testing was conducted on the adsorption effect of phenolic resin adsorbent material on lead ions under different conditions. The specific steps are as follows: 1) pH effect: The phenolic resin adsorbent obtained in Example 1 was used for Pb(II) adsorption. The initial concentration of Pb(II) was 600 mg / L, the amount of adsorbent added was 1 g / L, the temperature was 25℃, and the adsorption time was 240 min. The pH value of the solution was controlled within the range of 3.0 to 6.0.

[0054] The results show (see) Figure 6 As the pH value increases, the adsorption capacity of the material for Pb(II) increases, reaching an optimal level at approximately pH 5.0; the adsorption capacity remains relatively high between pH 5.0 and 6.0. Considering that Pb(II) may hydrolyze or form Pb(OH)₂ precipitate at pH values ​​above approximately 5.2, subsequent experiments preferably use a pH of 5.0 to reduce the interference of precipitation on the adsorption results.

[0055] 2) Temperature effect: The phenolic resin adsorbent obtained in Example 1 was used for Pb(II) adsorption. The initial concentration of Pb(II) was 100 mg / L, the amount of adsorbent added was 1 g / L, the pH was 5.0, and the adsorption time was 240 min. The test temperature was adjusted to 25~45℃.

[0056] The results show (see) Figure 7 Within the aforementioned test range, the Pb(II) removal rate increased with increasing temperature; at 45°C, the Pb(II) removal rate was approximately 99%. This embodiment has not yet verified conditions above 45°C. Based on actual wastewater treatment energy consumption and common water temperature ranges, the preferred operating temperature is 25~45°C.

[0057] 3) Effect of ionic strength: The phenolic resin adsorbent obtained in Example 1 was used for Pb(II) adsorption. The initial concentration of Pb(II) was 100 mg / L, the amount of adsorbent added was 1 g / L, the temperature was 25℃, the pH was 5.0, and the adsorption time was 240 min. Na was also added to the Pb(II) solution simultaneously. + K + Ca 2+ and Mg 2+ The concentration of each coexisting ion was set at four levels from low to high: 10 mg / L, 50 mg / L, 100 mg / L, and 200 mg / L.

[0058] The results show (see) Figure 8 The presence of coexisting ions has little impact on Pb(II) removal, and the Pb(II) removal rate can still reach over 96% after adsorption.

[0059] 4) Recycling test: The phenolic resin adsorbent obtained in Example 1 was used for Pb(II) adsorption. The initial concentration of Pb(II) was 300 mg / L, the amount of adsorbent added was 1 g / L, the temperature was 25℃, the pH was 5.0, and the adsorption time was 240 min. After adsorption, it was desorbed by shaking with 0.1 mol / L HNO3 for 6 h, and after washing, it was reused for the next round of adsorption.

[0060] The results show (see) Figure 9 After five adsorption-desorption cycles, the removal rate of Pb(II) can still be maintained at about 82%.

[0061] Application Example 2 Adsorption isotherms and kinetic characteristics The phenolic resin adsorbent obtained in Example 1 was used for Pb(II) isothermal adsorption tests. The initial Pb(II) concentration was set to 50–1000 mg / L, the pH was controlled at 5.0, the adsorption time was 240 min, and the test temperatures were 298 K, 308 K, and 318 K. Using the Langmuir model, the maximum adsorption capacities were approximately 355.8 mg / g, 407.6 mg / g, and 444.1 mg / g, respectively, indicating that increasing the temperature is beneficial for Pb(II) adsorption.

[0062] The phenolic resin adsorbent material obtained in Example 1 was used for Pb(II) kinetic testing. The initial concentration of Pb(II) was 600 mg / L, the pH was 5.0, the temperature was 298 K, and the reaction time was 0-180 min.

[0063] The results showed that Pb(II) was rapidly adsorbed within the first 30 min and then gradually reached equilibrium. The correlation coefficient of the Elovich model was about 0.99 and the correlation coefficient of the pseudo-second-order kinetic model was about 0.98, indicating that the adsorption process was closely related to the surface interactions involving heterogeneous active sites and oxygen-containing functional groups.

[0064] Comparative Example 1 A phenolic resin adsorbent material is prepared in a manner that is basically the same as in Example 1, except that in step 2), the pH of the system is not adjusted to 9.0-11.0, but formaldehyde is directly added and heated under near-neutral conditions.

[0065] The results show that the obtained product has poor stability in curing and water, indicating that the alkaline polycondensation conditions used in this invention play an important role in the formation of the water-insoluble GA / FM resin skeleton.

[0066] Comparative Example 2 A phenolic resin adsorbent material is prepared in a manner that is basically the same as in Example 1, except that: in step 3), acidification is not performed, or the pH is higher than 4.0 after acidification before filtration and drying.

[0067] The results showed that the obtained polycondensation products were difficult to fully solidify and precipitate, and the obtained materials had poor stability and filtration and recovery performance in water.

[0068] Comparative Example 3 A phenolic resin adsorbent material is prepared in a manner that is basically the same as in Example 1, except that in step 2), the GA:FM molar ratio is less than 1:3.0 (specifically 1:2.8).

[0069] If the crosslinking density is insufficient under these conditions, the material is prone to problems such as an increase in soluble components or insufficient structural stability.

[0070] Furthermore, if the GA:FM molar ratio is higher than 1:8.0 (specifically 1:8.5), the degree of cross-linking is too high, which may lead to a decrease in the accessibility of active sites such as carboxyl and phenolic hydroxyl groups.

[0071] In summary, the synergistic regulation mechanism of the GA to FM material ratio and pH / temperature / time is of great significance for obtaining resin materials with both stability and high adsorption performance.

[0072] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A phenolic resin adsorbent material, characterized in that, Its general structural formula is shown in Formula I; I； In the formula, n is an integer from 2 to 20; and Choose one of CH2 or CH2-O-CH2 independently.

2. The phenolic resin adsorbent material according to claim 1, characterized in that, The number-average molecular weight of the phenolic resin adsorbent material is 500-4000 Da.

3. The method for preparing the phenolic resin adsorbent material according to claim 1 or 2, characterized in that, Includes the following steps: 1) Add formaldehyde aqueous solution to the obtained gallic acid solution, and add an alkalinity regulator to adjust the obtained reaction system to alkalinity; 2) The polycondensation reaction was carried out under stirring conditions, and then naturally cooled to room temperature; 3) Add acid to the reaction solution obtained in step 2) to adjust it to acidity, and let it stand; 4) Filter the reaction system obtained in step 3), wash with water, and dry to obtain the phenolic resin adsorbent material.

4. The preparation method according to claim 3, characterized in that, In step 1), the molar ratio of gallic acid to formaldehyde is 1:(3.0-8.0).

5. The preparation method according to claim 3, characterized in that, In step 1), the pH of the reaction system is adjusted to 9.0-11.

0.

6. The preparation method according to claim 3, characterized in that, In step 2), the heating polycondensation reaction is carried out at a temperature of 65-85℃ for a time of 60-180 min.

7. The preparation method according to claim 3, characterized in that, In step 3), adjust the pH value to 1.5-3.0; let it stand for 10-90 minutes.

8. The application of the phenolic resin adsorbent material according to claim 1 or 2 in the treatment of heavy metal wastewater, characterized in that, Includes the following steps: 1) Add phenolic resin adsorbent material to the heavy metal wastewater to be treated at a dosage of 0.5-10 g / L; 2) Adsorption treatment at 15-45℃ for 30-240 min; solid-liquid separation to obtain treated water after adsorption of heavy metal ions.

9. The application according to claim 8, characterized in that, The heavy metal wastewater is lead-containing wastewater; the initial concentration of Pb(II) in the lead-containing wastewater is 10-1000 mg / L.

10. A method for recycling the phenolic resin adsorbent material according to claim 1 or 2, characterized in that, Includes the following steps: 1) Add the phenolic resin adsorbent material after adsorption treatment to a nitric acid solution and shake to desorb; 2) Filter, wash, and collect the regenerated phenolic resin adsorbent material; 3) The regenerated phenolic resin adsorbent material is added back into the heavy metal wastewater for heavy metal adsorption treatment.

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