Modified ardealite adsorbent as well as preparation method and application thereof

Abstract

The invention provides a modified ardealite adsorbent as well as a preparation method and application thereof, and belongs to the technical field of industrial solid waste resource utilization and wastewater treatment. The preparation method of the modified ardealite adsorbent comprises the following steps: drying ardealite, grinding, sieving, mixing with an APTES solution, adjusting the pH value to 7-9, and stirring for reaction to obtain APTES modified ardealite; uniformly mixing the APTES modified ardealite with the first solution and the second solution, stirring and reacting for 12-24 hours, and performing centrifugal separation, washing and freeze drying to obtain a modified ardealite adsorbent; wherein the first solution is an aqueous solution of graphene oxide; the second solution is a mixed solution of PEI and glutaraldehyde. The industrial solid waste ardealite is used as a raw material, is subjected to multiple modification and is used as an adsorbent for removing heavy metal ions and dyes in industrial wastewater, and the removal rate of the heavy metal ions and the dyes is high.

Description

Technical Field

[0001] The invention relates to the technical field of industrial solid waste resource utilization and wastewater treatment, and in particular to a modified phosphogypsum adsorbent and a preparation method and application thereof. Background Art

[0002] Pollution by heavy metals and dyes has caused serious alarm among researchers worldwide. Hexavalent chromium (Cr(VI)) is a common heavy metal pollutant known for its toxic and carcinogenic properties. Malachite green (MG) is a triphenylmethane dye that not only causes serious water pollution but also poses risks to organisms due to its carcinogenic, teratogenic, mutagenic and sensitizing effects. Naphthol green B (NGB) is an azo dye that is widely present in the environment and is notorious. Dyes can be toxic to aquatic organisms and affect fish and other organisms if they enter water bodies. Heavy metals such as Cr(VI) are often present in wastewater containing dyes, which poses a challenge for subsequent treatment. Therefore, it is crucial to develop a multifunctional material that can remove Cr(VI), NGB and MG from water sources. Currently, a variety of methods such as chemical precipitation, ion exchange, membrane filtration and adsorption are used for the removal of heavy metals and dyes from wastewater. These methods inevitably have difficulties in terms of economy or waste management. Adsorption, as a powerful, simple and economical technology, has been widely used to remove heavy metals and dyes from aqueous media.

[0003] Phosphogypsum (PG) is a byproduct of phosphate fertilizer production. With the development of my country's phosphate fertilizer industry, the amount of phosphogypsum produced has increased dramatically. The large-scale storage of phosphogypsum not only occupies a large amount of land resources, but also seriously pollutes the environment. Therefore, the resource utilization of phosphogypsum is of great significance to environmental governance. At present, phosphogypsum is mainly used in the metallurgical industry, the production of building gypsum boards, soil conditioners, cement retarders, etc. Studies have shown that phosphogypsum has certain adsorption properties for metal ions and dyes and can be used as an adsorbent to treat heavy metals and dyes in wastewater (Es-said A, Nafai H, Zerki N, Bchitou R, Chemometrics approach for multi-response optimisation of heavy metals Zn(II),Cu(II) and Cd(II) removal by phosphogypsum: Ternary aqueous solution[J]. International Journal of Environmental Analytical Chemistry, 2021, 103(13):3044-3058.) (GaoY, Sun D, ​​Han C, Huang J, Comprehensive utilization ofphosphogypsum: Adsorption of methylene blue and its application in bricks[J]. Surface Review and Letters, 2021, 28(09): 2150075). However, when phosphogypsum is used directly as an adsorbent, the adsorption capacity is low and the adsorption effect is general due to the limited adsorption sites.At present, there are a few literature reports on the use of modified phosphogypsum to treat heavy metals and dyes in wastewater, but the reported adsorbents have limited removal capacity for heavy metals and dyes, and the phosphogypsum modification method is relatively complicated ( Lian G, Wang B, Lee X, Li L, Liu T, Lyu W, Enhanced removal of hexavalent chromium by engineered biochar composite fabricated from phosphogypsum and distillers grains[J]. Science of The TotalEnvironment, 2019, 697: 134119. ) ( Lu M, Wang Y, Yu J, Li D, Zhao Q, Chi R, Treating waste with waste: Adsorption of anionic dyes in wastewater withsurfactant-modified phosphogypsum[J]. Environmental Research, 2023, 237:116963. ). Therefore, it is of great significance to develop a new type of modified phosphogypsum adsorbent with simple synthesis and excellent performance for the removal of heavy metal ions and dyes in wastewater, which can not only realize the resource utilization of large amounts of stockpiled phosphogypsum, but also provide an effective method for the treatment of environmental pollutants. Summary of the invention

[0004] In view of the technical problems existing in the background technology, the present application provides a modified phosphogypsum adsorbent and its preparation method and application, aiming to solve the technical problems that the existing modified phosphogypsum adsorbent has limited removal capacity for heavy metals and dyes and the modification method is complicated.

[0005] In a first aspect, the present application provides a method for preparing a modified phosphogypsum adsorbent, comprising the following steps: S1. Dry the phosphogypsum, grind it and sieve it to obtain a phosphogypsum pretreatment sample; S2, mixing the phosphogypsum pretreated sample with the APTES solution, adjusting the pH to 7-9, and stirring the mixture to obtain the APTES-modified phosphogypsum; S3. After mixing the APTES-modified phosphogypsum with the first solution and the second solution, stirring the mixture for 12 to 24 hours, centrifuging, washing, and freeze-drying to obtain a modified phosphogypsum adsorbent; wherein the first solution is an aqueous solution of graphene oxide; and the second solution is a mixed solution of PEI and glutaraldehyde.

[0006] Preferably, in step S1, the drying temperature is 40-60°C.

[0007] Preferably, in step S1, the mesh size of the sieving is 180-200 meshes.

[0008] Preferably, in step S2, the mass ratio of APTES to phosphogypsum is (0.38~1.14):1.

[0009] Preferably, in step S3, the mass ratio of graphene oxide to APTES-modified phosphogypsum is (0.5-5):1.

[0010] Preferably, in step S3, the mass ratio of graphene oxide to APTES-modified phosphogypsum is (1-2):1.

[0011] Preferably, in step S3, the concentration of graphene oxide in the first solution is 0.5 mg / mL to 5 mg / mL.

[0012] Preferably, in step S3, the mass volume ratio of APTES-modified phosphogypsum to the second solution is 1-5 mg / mL; the mass concentration of PEI in the second solution is 5-20 g / L, and the concentration of glutaraldehyde is 0.5-1%.

[0013] Preferably, in step S3, the stirring rate is 100-300 rpm.

[0014] In a second aspect, the present application provides a modified phosphogypsum adsorbent prepared by the method described in the first aspect.

[0015] In a third aspect, the present application provides a modified phosphogypsum adsorbent prepared by the method described in the first aspect for use in adsorbing heavy metals and / or dyes in wastewater. Preferably, the heavy metal includes Cr(VI); and the dye includes Naphthol Green B and Malachite Green.

[0016] Preferably, the concentration of Cr(VI) in the wastewater is ≤1000 mg / L; the concentration of naphthol green B in the wastewater is ≤1000 mg / L; the concentration of malachite green in the wastewater is ≤2000 mg / L; and the added amount of the modified phosphogypsum adsorbent is 0.375 mg / mL~0.6 mg / mL.

[0017] The principle of the technical solution of the present invention is: (1) Unmodified phosphogypsum has an irregular plate-like structure and a rough surface. However, after modification with 3-aminopropyltriethoxysilane (APTES), the regularity and compactness of the phosphogypsum surface are increased. APTES-PG introduces amino functional groups on the surface of phosphogypsum. These newly introduced functional groups provide active sites for subsequent reactions with graphene oxide (GO) and polyethyleneimine (PEI). The change in surface morphology and the introduction of new functional groups provide more adsorption sites for the adsorption process. The denser and more compact surface and amino functional groups enable phosphogypsum to better interact with heavy metal ions and dye molecules in wastewater. For example, amino functional groups can chelate with heavy metal ions and increase the adsorption capacity for heavy metal ions.

[0018] (2) After PEI is grafted with graphene oxide, graphene oxide (GO) is grafted onto phosphogypsum (PG) in its typical flake shape to form a PG-GO-PEI composite material, which significantly changes the structure of phosphogypsum. This structural change not only retains the original properties of phosphogypsum, but also introduces the large specific surface area of ​​graphene oxide and the metal chelating ability of PEI. Graphene oxide has a large number of functional groups, such as carboxyl and hydroxyl groups, which can interact with heavy metal ions and dye molecules to enhance the adsorption effect. At the same time, the introduction of PEI further increases the metal chelating ability of the adsorbent, making it have a higher selective adsorption capacity for heavy metal ions. In addition, PEI grafted with graphene oxide also improves the hydrophilicity and chemical activity of the surface of phosphogypsum, making it easier for the composite material to contact pollutants in wastewater and undergo adsorption reactions.

[0019] Compared with the prior art, the beneficial effects of the present invention include: (1) The present invention uses industrial solid waste phosphogypsum as a raw material, firstly uses 3-aminopropyltriethoxysilane (APTES) to modify the phosphogypsum so that its surface contains amino functional groups, and then uses GO and PEI containing carboxylic acid and amino functional groups as modifiers to prepare PEI-grafted graphene oxide-modified phosphogypsum, which is used as an adsorbent for the removal of heavy metal ions and dyes in industrial wastewater. The removal rate of heavy metal ions and dyes is high, which is significantly better than that of unmodified phosphogypsum.

[0020] (2) The adsorbent prepared by the present invention has an adsorption capacity of 313.5 mg / g for heavy metal ion Cr(VI), 425.5 mg / g for NGB, and 3300.9 mg / g for MG, which are significantly better than the modified phosphogypsum adsorbents reported previously.

[0021] (3) The present invention develops a new way to recycle PG solid waste, thereby alleviating the environmental pollution problem caused by long-term storage of PG.

[0022] (4) The adsorbent prepared by the present invention has excellent performance, low production cost and good stability. It can be used as a sustainable and efficient wastewater treatment agent with strong industrial application value, and has made a positive contribution to the development of green technology for environmental remediation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 SEM images of phosphogypsum (a), APTES-PG (b) and PG-GO-PEI (c) prepared in Example 1, and EDS elemental images of PG-GO-PEI (d~i); Figure 2 Thermogravimetric diagrams of phosphogypsum and PG-GO-PEI prepared in Example 1; Figure 3 FTIR images of phosphogypsum and PG-GO-PEI prepared in Example 1; Figure 4 This is a graph showing the effect of the amount of PG-GO-PEI adsorbent prepared in Example 1 on the adsorption performance of Cr(VI), NGB and MG; Figure 5 It is a comparison chart of the adsorption performance of the modified phosphogypsum adsorbent prepared in Example 1 and Comparative Example 3 on Cr(VI), NGB and MG; Figure 6 It is a comparison chart of the adsorption performance of the modified phosphogypsum adsorbent prepared in Example 1 and Comparative Example 1 on Cr(VI), NGB and MG; Figure 7 This is a comparison chart of the adsorption performance of the modified phosphogypsum adsorbent prepared in Example 1 and Comparative Example 2 for Cr(VI), NGB and MG. DETAILED DESCRIPTION

[0024] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0025] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased from the market or are commonly used in the field.

[0026] 1. Preparation method Example 1 A method for preparing a modified phosphogypsum adsorbent, comprising the following steps: S1. Pretreatment of phosphogypsum: drying phosphogypsum (PG) in an oven at 50°C, grinding it through a 200-mesh sieve, and obtaining a pretreated phosphogypsum sample; S2. APTES modification: Weigh 0.50 g of the pretreated PG sample and add it to a beaker, then add 20 mL of an ethanol solution containing 2% 3-aminopropyltriethoxysilane (APTES) (v / v). Use ammonium hydroxide to adjust the pH to about 8, stir at room temperature for 12 h, wash with ethanol, centrifuge, and then dry in an oven at 50 ° C for 12 h to obtain the APTES-modified phosphogypsum product APTES-PG; S3, PEI grafted graphene oxide modification: 100 mg of graphene oxide (GO) powder was ultrasonically dispersed in 100 mL of deionized water, heated to 50 ° C and stirred for 1 h, then 100 mg of APTES-PG was added and stirred for 1 h. Then 100 mL of a mixed aqueous solution of polyetherimide (PEI) and glutaraldehyde (PEI mass concentration of 10 g / L, glutaraldehyde volume concentration of 1%) was added to the above solution, and stirring was continued for 12 h, centrifuged, washed with water, and freeze-dried for 24 h to obtain PG-GO-PEI adsorbent.

[0027] Example 2 Steps S1 and S2 of this embodiment are the same as those of embodiment 1.

[0028] The difference between this embodiment and embodiment 1 is that the mass ratio of graphene oxide to APTES-PG in step S3 is 0.5:1; step S3 is specifically as follows: S3, PEI grafted graphene oxide modification: 50 mg of graphene oxide (GO) powder was ultrasonically dispersed in 100 mL of deionized water, heated to 50 ° C and stirred for 1 h, then 100 mg of APTES-PG was added and stirred for 1 h. Then 100 mL of a mixed aqueous solution of polyetherimide (PEI) and glutaraldehyde (PEI mass concentration of 10 g / L, glutaraldehyde concentration of 1%) was added to the above solution, and stirring was continued for 12 h, centrifuged, washed with water, and freeze-dried for 24 h to obtain PG-GO-PEI adsorbent.

[0029] Example 3 Steps S1 and S2 of this embodiment are the same as those of embodiment 1.

[0030] The difference between this embodiment and embodiment 1 is that the mass ratio of graphene oxide to APTES-PG in step S3 is 1.5:1; step S3 is specifically as follows: S3, PEI grafted graphene oxide modification: 150 mg of graphene oxide (GO) powder was ultrasonically dispersed in 100 mL of deionized water, heated to 50 ° C and stirred for 1 h, then 100 mg of APTES-PG was added and stirred for 1 h. Then 100 mL of a mixed aqueous solution of polyetherimide (PEI) and glutaraldehyde (PEI mass concentration of 10 g / L, glutaraldehyde concentration of 1%) was added to the above solution, and stirring was continued for 12 h, centrifuged, washed with water, and freeze-dried for 24 h to obtain PG-GO-PEI adsorbent.

[0031] Example 4 Steps S1 and S2 of this embodiment are the same as those of embodiment 1.

[0032] The difference between this embodiment and embodiment 1 is that the mass ratio of graphene oxide to APTES-PG in step S3 is 2:1; step S3 is specifically as follows: S3, PEI grafted graphene oxide modification: 200 mg of graphene oxide (GO) powder was ultrasonically dispersed in 100 mL of deionized water, heated to 50 ° C and stirred for 1 h, then 100 mg of APTES-PG was added and stirred for 1 h. Then 100 mL of a mixed aqueous solution of polyetherimide (PEI) and glutaraldehyde (PEI mass concentration of 10 g / L, glutaraldehyde concentration of 1%) was added to the above solution, and stirring was continued for 12 h, centrifuged, washed with water, and freeze-dried for 24 h to obtain PG-GO-PEI adsorbent.

[0033] Example 5 The difference between this embodiment and embodiment 1 is that in step S2, 0.50 g of the pretreated PG sample is weighed and added to a beaker, and then 20 mL of an ethanol solution containing 1% 3-aminopropyltriethoxysilane (APTES) (v / v) is added. The remaining steps are the same as those in embodiment 1.

[0034] Example 6 The difference between this embodiment and embodiment 1 is that in step S2, 0.50 g of the pretreated PG sample is weighed and added to a beaker, and then 20 mL of an ethanol solution containing 3% 3-aminopropyltriethoxysilane (APTES) (v / v) is added. The remaining steps are the same as those in embodiment 1.

[0035] Comparative Example 1 The difference between this comparative example and Example 1 is that APTES is not used to modify the phosphogypsum, and the phosphogypsum is directly modified by PEI grafted graphene oxide. The specific steps are as follows: The phosphogypsum was dried in an oven at 50°C and ground through a 200-mesh sieve to obtain a pretreated phosphogypsum sample; 100 mg of graphene oxide (GO) powder was ultrasonically dispersed in 100 mL of deionized water, heated to 50°C and stirred for 1 h, followed by the addition of 100 mg of PG and continued stirring for 1 h. 100 mL of a mixed aqueous solution of PEI and glutaraldehyde (PEI mass concentration of 10 g / L, glutaraldehyde concentration of 1%) was added to the above solution, continued stirring for 12 h, centrifuged, washed with water, and freeze-dried for 24 h to obtain a modified phosphogypsum adsorbent.

[0036] Comparative Example 2 The phosphogypsum was dried in an oven at 50 °C and ground through a 200-mesh sieve to obtain the pretreated phosphogypsum sample, and then the adsorption experiments of Cr (VI), NGB and MG were carried out using PG.

[0037] Comparative Example 3 The difference between this comparative example and Example 1 is that the pH is adjusted to 4.2 during the APTES modification in step S2; the remaining steps are the same as those in Example 1. Specifically, step S2 is: 0.50 g of the pretreated PG sample was weighed and added to a beaker, and then 20 mL of ethanol solution containing 2% APTES (v / v) was added, and the pH value was adjusted to about 4.2 using acetic acid.

[0038] At a pH of about 4.2, the adsorption capacities of the prepared PG-GO-PEI adsorbent for Cr (VI), NGB and MG were 54.36 mg / g, 76.43 mg / g and 102.54 mg / g, respectively.

[0039] It shows that under the condition of pH value of about 8, 3-aminopropyltriethoxysilane (APTES) can be successfully modified on the surface of phosphogypsum to form APTES-PG. When the pH value is reduced to about 4.2, the modification effect of APTES on the surface of phosphogypsum may be inhibited. Due to the decrease in the silanization reaction rate under acidic conditions, APTES may not be able to fully react with phosphogypsum, resulting in a weakened modification effect.

[0040] Test Example 1 PG-GO-PEI Material Characterization Test Figure 1 SEM images of phosphogypsum (corresponding to Figure a), APTES-PG (corresponding to Figure b), PG-GO-PEI prepared in Example 1 (corresponding to Figure c), and EDS elemental image of PG-GO-PEI (corresponding to Figure di). Figure 1 (a) shows the SEM image of phosphogypsum. It can be seen from the figure that phosphogypsum has an irregular plate-like structure and a rough surface. Figure 1(b) is the SEM image of 3-aminopropyltriethoxysilane modified phosphogypsum. It can be seen from the figure that APTES-PG shows a denser and more compact crystal surface. Figure 1 (c) is the SEM image of PG-GO-PEI. Figure 1 (c) shows the typical flake shape of graphene oxide GO grafted on PG, indicating the successful modification of GO. EDS analysis in Figure (di) shows the presence of elements C, N, O, Si, Ca and S, further confirming the successful synthesis of PG-GO-PEI.

[0041] Figure 2 Thermogravimetric graphs of phosphogypsum and PG-GO-PEI prepared in Example 1. PG and PG-GO-PEI were measured using thermogravimetric analysis. The thermal decomposition of phosphogypsum began at about 110°C. Through layer-by-layer modification, PG-GO-PEI only lost 15.79% at 300°C, which was attributed to the decomposition of unstable oxygen-containing functional groups. The results show that the PG-GO-PEI adsorbent has good thermal stability. The difference in thermal stability between phosphogypsum PG and PG-GO-PEI also indicates the successful modification of GO and PEI.

[0042] Figure 3 FTIR graphs of phosphogypsum and PG-GO-PEI prepared in Example 1. At 2923 cm -1 and 2853 cm -1 Two very obvious characteristic peaks were observed at 2 , -CH 3 ), indicating that APTES was successfully modified on the PG surface. In addition, the 1121 cm -1 A new peak of Si-OC appeared at 1458 cm-1, which may be caused by the partial hydrolysis of APTES organosilane during the whole silanization process. These results indicate that there is a strong molecular interaction between graphene oxide nanosheets and APTES molecules. APTES molecules are successfully attached to the GO surface through the coupling reaction between the silanol groups in APTES and the -OH and -COOH functional groups on the GO surface. After PEI modification, the peak at 1458 cm-1 was -1 A new obvious peak was observed at 1647 cm -1 A characteristic peak at indicated that the C=N bond was formed between the amine group of PEI and the aldehyde group of glutaraldehyde through the Schiff base reaction. The strong interaction between graphene oxide nanosheets and polymer chains produced a synergistic effect and improved the structural stability of the composite material. FTIR spectral analysis showed that the PG-GO-PEI adsorbent was successfully prepared.

[0043] Test Example 2 Test on the adsorption performance of modified phosphogypsum adsorbent on Cr(VI), NGB and MG (1) Effect of modified phosphogypsum adsorbent dosage on the adsorption performance of Cr(VI), NGB and MG The test method is as follows: prepare 10 mL of Cr(VI) solution, NGB solution and MG solution respectively; wherein the pH value of Cr(VI) solution is 2 and the concentration is 50 mg / L; the pH value of NGB solution is 5 and the concentration is 100 mg / L; the pH value of MG solution is 7 and the concentration is 100 mg / L. Different masses of the modified phosphogypsum adsorbent prepared in Example 1 are added to the above solutions respectively, and after observing the adsorption for 4 hours, the supernatant is taken by centrifugation, the concentration of the remaining substance to be tested in the purified solution is determined, and the removal rate and adsorption capacity are calculated.

[0044] Figure 4 The effect of the amount of PG-GO-PEI adsorbent prepared in Example 1 on the adsorption performance of Cr(VI), NGB and MG. Generally speaking, as the amount of adsorbent increases, the removal rate gradually increases, but the adsorption capacity does not always follow this trend. When the concentration of pollutants in the wastewater remains unchanged, a higher adsorbent dosage provides more available adsorption sites, thereby improving the removal rate. However, an increase in dosage also leads to a decrease in the unit adsorption capacity of the adsorbent. Therefore, considering the cost and adsorption efficiency, it is concluded that a dosage of 6 mg is the optimal dosage for achieving the highest removal efficiency of Cr(VI), while a dosage of 3.75 mg is the optimal dosage for removing NGB and MG. The PG-GO-PEI adsorbent prepared by the present invention exhibits excellent adsorption performance, with a removal rate of 100% for Cr(VI), NGB and MG, an adsorption capacity of 313.5 mg / g for heavy metal ions Cr(VI), 425.5 mg / g for NGB, and 3300.9 mg / g for MG.

[0045] (2) Effect of preparation conditions on the adsorption performance of modified phosphogypsum The test method is as follows: prepare 10 mL of Cr(VI) solution, NGB solution and MG solution respectively; wherein the pH value of Cr(VI) solution is 2 and the concentration is 50 mg / L; the pH value of NGB solution is 5 and the concentration is 100 mg / L; the pH value of MG solution is 7 and the concentration is 100 mg / L. Add 6 mg, 3.75 mg and 3.75 mg of the modified phosphogypsum adsorbent prepared in Examples 1-6 and Comparative Examples 1-3 to the above solutions respectively, observe the adsorption for 4 hours, centrifuge and take the supernatant, determine the concentration of the remaining substance to be tested in the purified solution, and calculate the adsorption equilibrium amount.

[0046] The adsorption performance results of the modified phosphogypsum adsorbents prepared in Examples 1 to 6 for Cr(VI), NGB and MG are shown in Table 1.

[0047] Table 1

[0048] It can be seen from Table 1 that the modified phosphogypsum adsorbents prepared in Examples 1 to 6 of the present invention show good adsorption effects on Cr (VI), NGB and MG. It can be found from Table 1 that increasing the amount of graphene oxide can improve the adsorption effects on Cr (VI), NGB and MG.

[0049] Figure 5 The figure is a comparison of the adsorption performance of the modified phosphogypsum adsorbent prepared in Example 1 and Comparative Example 3 for Cr(VI), NGB and MG under the conditions of pH=8 and pH=4.2. It can be seen from the figure that under the same conditions, the adsorption effect of the PG-GO-PEI adsorbent prepared in Example 1 at a pH of about 8 is significantly greater than that of the PG-GO-PEI adsorbent prepared in Comparative Example 3 at a pH of about 4.2. This may be due to the reduced silanization reaction rate under acidic conditions, and APTES cannot fully react with phosphogypsum, resulting in a weakened modification effect.

[0050] Figure 6 The following is a comparison of the adsorption performance of the modified phosphogypsum adsorbent prepared in Example 1 and Comparative Example 1 on Cr(VI), NGB and MG. Figure 6 It can be seen that compared with Comparative Example 1, the modified phosphogypsum adsorbent prepared in Example 1 has better adsorption effects on Cr (VI), NGB and MG, indicating that after PG is modified by APTES, amino functional groups are introduced, and these newly introduced functional groups provide active sites for subsequent reactions with graphene oxide (GO) and polyethyleneimine (PEI), so that phosphogypsum can better interact with heavy metal ions and dye molecules in wastewater.

[0051] Figure 7 The figure is a comparison of the adsorption performance of PG prepared in Example 1 and Comparative Example 2 on Cr(VI), NGB and MG. Figure 7 It can be seen that under the same test conditions, PG-GO-PEI has better adsorption effects on Cr(VI), NGB and MG than PG, indicating that the adsorption performance of phosphogypsum is significantly improved after modification with PEI and GO.

[0052] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a modified phosphogypsum adsorbent, characterized in that: The steps include: S1. Dry the phosphogypsum, grind it and sieve it to obtain a phosphogypsum pretreatment sample; S2, mixing the phosphogypsum pretreated sample with the APTES solution, adjusting the pH to 7-9, and stirring the mixture to obtain APTES-modified phosphogypsum; S3. After mixing the APTES-modified phosphogypsum with the first solution and the second solution, stirring the mixture for 12 to 24 hours, centrifuging, washing, and freeze-drying to obtain the modified phosphogypsum adsorbent; wherein the first solution is an aqueous solution of graphene oxide; and the second solution is a mixed solution of PEI and glutaraldehyde.

2. The method for preparing a modified phosphogypsum adsorbent according to claim 1, characterized in that: In the step S1, the drying temperature is 40-60° C., and the sieving mesh size is 180-200 meshes.

3. The method for preparing a modified phosphogypsum adsorbent according to claim 1, characterized in that: In the step S2, the mass ratio of APTES to phosphogypsum is (0.38-1.14):

1.

4. The method for preparing a modified phosphogypsum adsorbent according to claim 1, characterized in that: In the step S3, the mass ratio of the graphene oxide to the APTES-modified phosphogypsum is (0.5-5):

1.

5. The method for preparing a modified phosphogypsum adsorbent according to claim 1, characterized in that: In step S3, the concentration of graphene oxide in the first solution is 0.5 mg / mL to 5 mg / mL.

6. The method for preparing a modified phosphogypsum adsorbent according to claim 1, characterized in that: The mass volume ratio of the APTES modified phosphogypsum to the second solution is 1-5 mg / mL; the mass concentration of PEI in the second solution is 5-20 g / L, and the volume concentration of glutaraldehyde is 0.5-1%.

7. The modified phosphogypsum adsorbent obtained by the preparation method of the modified phosphogypsum adsorbent according to any one of claims 1 to 6.

8. Use of the modified phosphogypsum adsorbent according to claim 7 in adsorbing heavy metals and / or dyes in wastewater.

9. The use according to claim 8, characterized in that: The heavy metal includes Cr(VI); and the dye includes naphthol green B and malachite green.

10. The use according to claim 9, characterized in that: The concentration of Cr(VI) in the wastewater is ≤1000 mg / L; the concentration of naphthol green B in the wastewater is ≤1000 mg / L; the concentration of malachite green in the wastewater is ≤2000 mg / L; and the added amount of the modified phosphogypsum adsorbent is 0.375 mg / mL~0.6 mg / mL.

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