A method for removing polymorphic inorganic phosphorus

Abstract

The present invention discloses a method for removing multi-form inorganic phosphorus, belonging to the technical field of preparation and application of environmental materials. The method is as follows: adding a biomass-based modified iron-based organic framework composite material and an oxidant into nickel-containing electroplating wastewater, and oscillating and adsorbing at room temperature to remove multi-form inorganic phosphorus in the nickel-containing electroplating wastewater; wherein, the multi-form inorganic phosphorus includes phosphate, phosphite, and nickel-complexed phosphite. The biomass-based modified iron-based organic framework composite material prepared by the present invention can achieve the breaking and adsorption of heavy metal-phosphite complexes, the oxidation and adsorption of phosphite, and the adsorption of orthophosphate in electroplating wastewater in one step. The maximum adsorption capacities for phosphate, phosphite, and nickel-complexed phosphite are 2.26 mmol / g, 1.89 mmol / g, and 2.77 mmol / g respectively, and the loss amount in practical applications does not exceed 3%, and it has a wide applicable pH range.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation and application of environmental materials, and particularly relates to a method for removing multi-form inorganic phosphorus. Background Art

[0002] Electroplating is an essential basic industry for human industry and life. However, due to the large amount of phosphorus-containing polluted wastewater discharged during the process, the electroplating industry has become one of the most dangerous chemical-intensive industries in the world. A variety of phosphorus-containing wastewater is generated during the production process. Phosphorus is one of the main elements causing water eutrophication. It can accelerate the growth of phytoplankton, resulting in oxygen consumption and the death of fish and aquatic organisms. Phosphite (P(III)) is an important component of total dissolved phosphorus (TP) and is an emerging eutrophication pollutant. It can be converted into phosphate (P(V)) in the biogeochemical phosphorus cycle occurring naturally in the aquatic environment. The accumulation of P(III) in electroplating wastewater comes from phosphorus-containing agents such as phosphoric acid, complexing agents, reducing agents, etc.

[0003] Nowadays, extensive exploration has been carried out on methods for removing P(V), including processes such as ion exchange method, membrane separation method, adsorption method, etc. Compared with other methods, the adsorption method has lower preparation cost and fewer required processes. It is suitable for enriching and recovering low-concentration phosphorus using solid functional groups and has the advantages of simplicity, low cost, and low carbon. However, since P(III) is more likely to complex with heavy metal ions in electroplating wastewater than P(V), common P(V) removal technologies cannot be directly applied to P(III). The main method is a two-step removal strategy, which oxidizes P(III) to P(V) and breaks the complexing system, and then removes P(V) by precipitation or biological treatment. However, the two-step method is complex and costly, and precipitation or biological treatment often cannot reduce the total phosphorus concentration to the discharge standard. In recent years, one-step methods such as electro-induced oxidation precipitation method, simultaneous oxidation method, and filtration method have been widely adopted. Therefore, one-step coupling of oxidation and adsorption can promote the entire P(III) removal process and effectively remove P(III) in water.

[0004] Literature studies at home and abroad have shown that iron-based metal-organic frameworks are a new type of porous coordination polymer material assembled by coordination of iron and organic ligands. They have a unique structure, a large specific surface area, and uniform, controllable, and diverse pore structures. They are widely used in the adsorption field and have shown strong phosphorus absorption and anti-interference abilities. Modifying MOF is beneficial to the optimization of its crystal structure and the improvement of porosity. These modification methods usually result in MOF having unique structures and properties, ultimately facilitating its ion adsorption ability in water. Currently, there are common problems with modified MOF, such as excessively high costs and energy consumption, and low adsorption efficiency. Graphene oxide is widely used to modify the stability and optical properties of MOF, but it blocks large organic molecules and the electrostatic attraction generated is too small to provide significant selective adsorption. Nitrogen-doped Fe-based MOF can be used to activate persulfate to further adsorb pollutants. However, due to uneven mixing of raw materials, only nitrogen heteroatoms can be directly incorporated into the carbon framework, and iron is prone to aggregation during carbonization, resulting in incomplete exposure of active sites and metal leaching, thereby impairing catalytic activity.

[0005] In addition, although it performs well in phosphorus absorption, the use of fine particles in wastewater treatment may lead to element loss and poor recycling and reuse after treatment, resulting in higher operating costs. Therefore, it is very important to find a suitable matrix to retain the adsorbent for the recycling and recovery of waste adsorbents.

[0006] Chinese Patent No. CN114621457A discloses a modified iron-based metal-organic framework material, its preparation method and uses. Dissolve FeCl3·6H2O, Ni(NO3)2·6H2O and reagent A (reagent A is terephthalic acid or a mixture of 2-aminoterephthalic acid and p-mercaptobenzoic acid) in N,N-dimethylformamide solution, then add NaOH solution, stir evenly and transfer to a high-pressure reaction kettle. The pressure value in the high-pressure reaction kettle is 0.2 - 0.4 MPa, react at 80 - 150 °C for 15 - 24 h, then cool, centrifuge, wash with N,N-dimethylformamide solution, and finally dry at 70 - 75 °C for 15 - 24 h to obtain the modified iron-based metal-organic framework material. This patent shows that modifying the organic framework can enhance the material's reaction ability under visible light, but the material preparation cycle is long, and higher costs are required to achieve better effects.

[0007] The patent with Chinese Patent No. CN117866222A discloses a modified iron-copper-based bimetallic organic framework material, its preparation method and uses: Dissolve FeCl3·6H2O, Cu(NO3)2·3H2O, and 1,4-naphthalenedicarboxylic acid in N,N-dimethylformamide, add NaOH dissolved in ultrapure water, mix well, and react at 0.2 - 0.4 Mpa and 80 - 180 °C for 10 - 20 h. After the reaction, wash and centrifuge with N,N-dimethylformamide for multiple times, then react at 50 - 100 °C for 15 - 20 h, and finally obtain the modified iron-copper-based bimetallic organic framework material Fe-Cu-T100 for visible light photocatalytic reduction of CO2 by grinding. The successful preparation of this material shows that modifying the organic framework material can improve the catalytic performance, but this material is only used in the photocatalytic field and fails to demonstrate its potential in adsorption.

[0008] The patent with Chinese Patent No. CN202210404779.8 discloses a preparation method and application of MIL-100(Fe) / cellulose porous composite spheres. Add the iron-based organic framework to the cellulose solution, stir evenly, and soak it in the metal ion solution to obtain a composite sphere hydrogel, which has the advantages of good mechanical properties, high porosity, high adsorption efficiency, etc., but the leakage risk of the iron-based organic framework is not accurately controlled during the preparation process.

[0009] Through retrieval, no relevant patents and public literatures have been found on the adsorption of multi-form inorganic phosphorus in electroplating wastewater in the form of biomass-based modified iron-based organic framework composites. Therefore, there is an urgent need to develop a method to effectively improve the adsorption efficiency of multi-form inorganic phosphorus, maintain a high adsorption capacity, load biomass-based materials to reduce the loss of MOF during continuous operation, and effectively remove multi-form inorganic phosphorus from electroplating wastewater. Compared with the patent previously applied by the inventor (CN118236986A), the adsorbed pollutants have expanded from single phosphate to multi-form inorganic phosphorus, and the application scope is the removal of multi-form inorganic phosphorus in nickel-containing electroplating wastewater. Summary of the Invention

[0010] Aiming at the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for removing multi-form inorganic phosphorus, which adopts one-step coupling catalytic oxidation and adsorption of inorganic phosphorus, and the method is simple and low-cost.

[0011] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0012] A method for removing multi-form inorganic phosphorus, adding a biomass-based modified iron-based organic framework composite material and an oxidant into nickel-containing electroplating wastewater, oscillating and adsorbing at room temperature to remove multi-form inorganic phosphorus in the nickel-containing electroplating wastewater; wherein, the multi-form inorganic phosphorus includes phosphate, phosphite, and nickel-complexed phosphite; the nickel-containing electroplating wastewater contains 0.25-4 mmol / L of nickel chloride and phosphite.

[0013] Preferably, the mass ratio of the biomass-based modified iron-based organic framework composite material to the oxidant is 0.5-1.5:0.04-0.08.

[0014] Preferably, the preparation process of the biomass-based modified iron-based organic framework composite material is: performing a hydrothermal reaction on a precursor and then calcining it to form a modified iron-based organic framework Cc-BA-MIL-88(B), and reacting the modified iron-based organic framework Cc-BA-MIL-88(B), chitosan, a crosslinking agent, and a mixed solution to obtain the biomass-based modified iron-based organic framework composite material.

[0015] Preferably, the preparation process of the precursor is: mixing benzoic acid, terephthalic acid, ferric trichloride hexahydrate, and N,N-dimethylformamide uniformly to obtain a precursor.

[0016] Preferably, the mmol / mmol / mmol / mL of benzoic acid, terephthalic acid, ferric trichloride hexahydrate, and N,N-dimethylformamide is 3.2:12.8:16:100.

[0017] Preferably, the calcination is carried out in a nitrogen atmosphere, the calcination temperature is 400 °C, and the calcination time is 4-6 h.

[0018] Preferably, the oxidant is sodium persulfate.

[0019] A method for preparing a biomass-based modified iron-based organic framework composite material for the method of removing multi-form inorganic phosphorus described above, specifically including the following steps:

[0020] 1) Mixing benzoic acid, terephthalic acid, ferric trichloride hexahydrate, and N,N-dimethylformamide uniformly to form a precursor, performing a hydrothermal reaction on the precursor, centrifuging and drying to obtain BA-MIL-88(B);

[0021] 2) Calcining the BA-MIL-88(B) obtained in step 1) to obtain a modified iron-based organic framework Cc-BA-MIL-88(B);

[0022] 3) Add the modified iron-based metal-organic framework Cc-BA-MIL-88(B), chitosan, and crosslinking agent obtained in step 2) to acetic acid solution. After mixing evenly, heat-crosslink at 60 °C in a water bath for 2 h to obtain a mixed material;

[0023] 4) Drop the mixed material obtained in step 3) into a mixed solution containing sodium hydroxide, sodium sulfate, absolute ethanol, and water to obtain a hydrogel; place the obtained hydrogel in the diluted crosslinking agent to enhance its mechanical strength, wash it, and dry it at room temperature to prepare a biomass-based modified iron-based metal-organic framework composite material.

[0024] Preferably, the mass ratio of the modified iron-based metal-organic framework Cc-BA-MIL-88(B), chitosan, and crosslinking agent is 1:0.6:0.154 (g / g / mL).

[0025] Preferably, the crosslinking agent is epichlorohydrin.

[0026] Preferably, in the mixed solution, the mass ratio of sodium hydroxide, sodium sulfate, absolute ethanol, and water is 16:12:2:300 (g / g / mL / mL).

[0027] The preparation method of the biomass-based modified iron-based metal-organic framework composite material prepares the biomass-based modified iron-based metal-organic framework composite material.

[0028] Application of the biomass-based modified iron-based metal-organic framework composite material as an adsorbent for adsorbing multi-form inorganic phosphorus pollutants in nickel-containing electroplating wastewater.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) In the method for removing multi-form inorganic phosphorus provided by the present invention, the prepared biomass-based modified iron-based metal-organic framework composite material can be applied to the removal of multi-form inorganic phosphorus in nickel-containing electroplating wastewater. The maximum adsorption capacities for phosphate, phosphite, and nickel-complexed phosphite can reach 2.26 mmol / g, 1.89 mmol / g, and 2.77 mmol / g, respectively;

[0031] (2) For the biomass-based modified iron-based metal-organic framework composite material prepared by the present invention, when the molar ratio of benzoic acid to terephthalic acid is 2:8, the enhancement effect of the adsorption and removal ability of inorganic phosphorus is the best, and the adsorption effects on phosphate, phosphite, and phosphite containing nickel ions are not less than 1.5 mmol / g;

[0032] (3) In practical applications, the loss of the biomass-based modified iron-based metal-organic framework composite material prepared by the present invention does not exceed 3%, indicating that the biomass-based material chitosan effectively reduces the loss of the material;

[0033] (4) The method for removing multi - morphological inorganic phosphorus provided by the present invention, compared with the traditional Fenton method for phosphorus removal and biological method for phosphorus removal, when the prepared Cc - BA - MIL - 88(B)@Cs adsorbs and removes inorganic phosphorus in nickel - containing water bodies, has a wider applicable pH range and has good removal effects at pH values from 4 to 10;

[0034] (5) The method for removing multi - morphological inorganic phosphorus of the present invention couples catalytic oxidation and adsorption of inorganic phosphorus in one step through the prepared biomass - based - modified iron - based organic framework composite material. The method is simple and low - cost; it also has good removal effects in low - concentration electroplating nickel - containing inorganic phosphorus wastewater. Brief Description of the Drawings

[0035] Figure 1 SEM images of Cc - BA - MIL - 88(B)@Cs (a, d, g), BA - MIL - 88(B)@Cs (b, e, h), and MIL - 88(B)@Cs (c, f, i);

[0036] Figure 2 EPR spectra of Cc - BA - MIL - 88(B)@Cs and MIL - 88(B)@Cs;

[0037] Figure 3 Adsorption effect diagrams of Cc - BA - MIL - 88(B)@Cs, BA - MIL - 88(B)@Cs, and MIL - 88(B)@Cs on 1 mmol / L of each morphological inorganic phosphorus;

[0038] Figure 4 Adsorption effect diagrams of Cc - BA - MIL - 88(B)@Cs on each morphological inorganic phosphorus at different benzoic acid ratios;

[0039] Figure 5 Removal effect diagrams of Cc - BA - MIL - 88(B)@Cs on different concentrations of phosphite;

[0040] Figure 6 Adsorption effect diagrams of Cc - BA - MIL - 88(B)@Cs on different concentrations of phosphite at different temperatures;

[0041] Figure 7 Diagrams of the proportion of each role during the process of Cc - BA - MIL - 88(B)@Cs adsorbing nickel - containing phosphite solution;

[0042] Figure 8 Comparison diagrams of the adsorption effect of Cc - BA - MIL - 88(B)@Cs on inorganic phosphorus, the loss amount of iron ions, and traditional methods under different pH conditions;

[0043] Figure 9Effect diagram of Cc-BA-MIL-88(B)@Cs for adsorbing inorganic phosphorus in nickel-containing electroplating wastewater. Detailed implementation manners

[0044] The following further clarifies the present invention in conjunction with specific embodiments. The embodiments are implemented on the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In the following embodiments, unless otherwise specified, the technical means used are all conventional means well known to those skilled in the art. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0045] The performance test method adopted by the present invention is as follows:

[0046] (1) The test method for the content of various forms of inorganic phosphorus is: ammonium molybdate spectrophotometry (GB / T 11893-1989).

[0047] (2) The measurement method for iron ion content is: flame atomic absorption spectrophotometry (GB / T 11911-1989).

[0048] Example 1

[0049] A preparation method of a biomass-based modified iron-based organic framework composite material for removing various forms of inorganic phosphorus, comprising the following steps:

[0050] 1) Add 3.2 mmol of benzoic acid, 12.8 mmol of terephthalic acid and 16 mmol of ferric chloride hexahydrate to 100 mL of N,N-dimethylformamide and dissolve completely. Keep the temperature at 150 °C in an autoclave for 12 h, wash several times alternately with deionized water and methanol, and obtain 1.88 g of BA-MIL-88(B) after drying;

[0051] 2) Take 1.5 g of BA-MIL-88(B) prepared in step 1) and calcine it in a nitrogen atmosphere at 400 °C for 4 h to obtain 1.35 g of the modified iron-based organic framework Cc-BA-MIL-88(B);

[0052] 3) Add 1.0 g of modified iron-based metal-organic framework Cc-BA-MIL-88(B), 0.6 g of chitosan, and 0.154 mL of epichlorohydrin into 20 mL of 2% (V / V) acetic acid solution respectively, crosslink at a constant temperature of 60 °C for 2 h, dropwise add into a 300 mL mixed solution containing 16 g of sodium hydroxide, 12 g of sodium sulfate, and 2 mL of absolute ethanol with a syringe, fully crosslink to form a hydrogel, crosslink in 100 mL of distilled water containing 0.5 mL of epichlorohydrin for 2 h to enhance the mechanical strength, wash and then dry at room temperature to obtain 12.17 g of biomass-based modified iron-based metal-organic framework composite Cc-BA-MIL-88(B)@Cs.

[0053] Comparative Example 1

[0054] Weigh 1.0 g of MIL-88(B), 0.6 g of chitosan, and 0.154 mL of epichlorohydrin and add them into 20 mL of 2% (V / V) acetic acid solution respectively, crosslink at a constant temperature of 60 °C for 2 h, dropwise add into a 300 mL mixed solution containing 16 g of sodium hydroxide, 12 g of sodium sulfate, and 2 mL of absolute ethanol with a syringe, fully crosslink to form a hydrogel, crosslink in 100 mL of distilled water containing 0.5 mL of epichlorohydrin for 2 h to enhance the mechanical strength, wash and then dry at room temperature to obtain 12.85 g of material MIL-88(B)@Cs.

[0055] Comparative Example 2

[0056] 1) Add 3.2 mmol of benzoic acid, 12.8 mmol of terephthalic acid, and 16 mmol of ferric chloride hexahydrate into 100 mL of N,N-dimethylformamide and dissolve completely, keep at a constant temperature of 150 °C in an autoclave for 12 h, wash several times alternately with deionized water and methanol, and obtain 1.88 g of material BA-MIL-88(B) after drying;

[0057] 2) Add 1.0 g of BA-MIL-88(B) prepared in step 1), 0.6 g of chitosan, and 0.154 mL of epichlorohydrin into 20 mL of 2% (V / V) acetic acid solution respectively, crosslink at a constant temperature of 60 °C for 2 h, dropwise add into a 300 mL mixed solution containing 16 g of sodium hydroxide, 12 g of sodium sulfate, and 2 mL of absolute ethanol with a syringe, fully crosslink to form a hydrogel, crosslink in 100 mL of distilled water containing 0.5 mL of epichlorohydrin for 2 h to enhance the mechanical strength, wash and then dry at room temperature to obtain 12.43 g of BA-MIL-88(B)@Cs.

[0058] From Figure 1It can be seen that the surface structure of MIL-88(B)@Cs is relatively smooth. After introducing defects, the modified iron-based metal-organic framework in Cc-BA-MIL-88(B)@Cs can retain a similar morphology to the iron-based metal-organic framework in MIL-88(B)@Cs, but their surfaces become significantly rougher, and the surface roughness gradually increases with the introduction of benzoic acid and the calcination process. These defects are formed during the modification and calcination processes, accompanied by the appearance of several uniformly distributed particles.

[0059] It can be seen from Figure 2 that by measuring the vacancy defects of Cc-BA-MIL-88(B)@Cs and MIL-88(B)@Cs, it is proved that the defects appearing during modification are oxygen vacancies. The positively charged oxygen vacancies can promote the adsorption of negatively charged phosphate in phosphate, negatively charged phosphite in phosphite, and negatively charged phosphate in phosphate formed by the oxidation of phosphite after the complexation of nickel chloride complex phosphite through electrostatic attraction, thereby providing more adsorption sites.

[0060] Comparative Example 3

[0061] 1) When the total amount of benzoic acid and terephthalic acid is 16 mmol, control the proportion of benzoic acid to be 0% - 50%. Add benzoic acid, terephthalic acid, and 16 mmol of ferric chloride hexahydrate to 100 mL of N,N-dimethylformamide and dissolve completely. Keep the temperature constant at 150 °C in an autoclave for 12 h, wash several times alternately with deionized water and methanol, and obtain 1.72 g - 1.98 g of (0% - 50%)BA-MIL-88(B) after drying;

[0062] 2) Take 1.5 g of (0% - 50%)BA-MIL-88(B) prepared in step 1) and calcine it in a nitrogen atmosphere at 400 °C for 4 h to obtain 1.24 g - 1.42 g of modified iron-based metal-organic framework Cc-(0% - 50%)BA-MIL-88(B) respectively;

[0063] 3) Add 1.0 g of the modified iron-based metal-organic framework Cc-(0% to 50%)BA-MIL-88(B) prepared in step 2), 0.6 g of chitosan, and 0.154 mL of epichlorohydrin into 20 mL of 2% (V / V) acetic acid solution respectively. Crosslink at a constant temperature of 60 °C for 2 h, then dropwise add it into a 300 mL mixed solution containing 16 g of sodium hydroxide, 12 g of sodium sulfate, and 2 mL of absolute ethanol with a syringe to fully crosslink and form a hydrogel. Crosslink in 100 mL of distilled water containing 0.5 mL of epichlorohydrin for 2 h to enhance the mechanical strength. After washing, dry at room temperature to obtain 11.13 - 12.82 g of biomass-based modified iron-based metal-organic framework composite Cc-(0% to 50%)BA-MIL-88(B)@Cs. Among them, Cc-(20%)BA-MIL-88(B)@Cs is the Cc-BA-MIL-88(B)@Cs prepared in Example 1.

[0064] Example 2

[0065] Prepare 50 mL of mixed solutions containing phosphate, phosphite, and nickel chloride complexed phosphite respectively, where the concentrations of phosphate, phosphite, and nickel chloride complexed phosphite are all 1 mmol / L, adjust the pH value to 8.0, then add 0.08 g of oxidant sodium persulfate and 1.5 g of the adsorbent to be tested respectively. Oscillate at room temperature of 25 °C for 24 h, and use ammonium molybdate spectrophotometry (GB / T 11893 - 1989) to measure the content of inorganic phosphorus in the solution. The adsorption capacities of Cc-BA-MIL-88(B)@Cs prepared in Example 1, MIL-88(B)@Cs prepared in Comparative Example 1, and BA-MIL-88(B)@Cs prepared in Comparative Example 2 for phosphate, phosphite, and nickel chloride complexed phosphite in the solution are as Figure 3 shown in Table 1.

[0066] Table 1 Adsorption results for solutions containing phosphate, phosphite, and nickel chloride complexed phosphite

[0067]

[0068] From Table 1 and Figure 3It can be seen that the adsorption capacity of Cc-BA-MIL-88(B)@Cs prepared in Example 1 for 1 mmol / L phosphate is 0.68 mmol / g, which is higher than that of MIL-88(B)@Cs prepared in Comparative Example 1 for 1 mmol / L phosphate (0.25 mmol / g) and that of BA-MIL-88(B)@Cs prepared in Comparative Example 2 for 1 mmol / L phosphate (0.34 mmol / g); the adsorption capacity of Cc-BA-MIL-88(B)@Cs prepared in Example 1 for 1 mmol / L phosphite is 0.56 mmol / g, which is higher than that of MIL-88(B)@Cs prepared in Comparative Example 1 for 1 mmol / L phosphite (0.21 mmol / g) and that of BA-MIL-88(B)@Cs prepared in Comparative Example 2 for 1 mmol / L phosphite (0.28 mmol / g); the adsorption capacity of Cc-BA-MIL-88(B)@Cs for 1 mmol / L nickel chloride complexed phosphite is 1.02 mmol / g, which is higher than that of MIL-88(B)@Cs prepared in Comparative Example 1 for 1 mmol / L nickel chloride complexed phosphite (0.31 mmol / g) and that of BA-MIL-88(B)@Cs prepared in Comparative Example 2 for 1 mmol / L nickel chloride complexed phosphite (0.51 mmol / g). The results show that benzoic acid modification effectively improves the adsorption capacity of the material for phosphate and phosphite, and calcination increases the catalytic performance of the material, accelerating the breaking of the complex of nickel chloride complexed phosphite and the oxidation of phosphite. As Figure 1 and Figure 2 shown, the benzoic acid modification and the calcination process endow the iron-based metal-organic framework with many oxygen vacancies and active sites, which is beneficial to improving the adsorption performance of the material for phosphite. During the adsorption process, the possible mechanism mainly depends on electrostatic attraction and complexation between the oxygen vacancy sites from the Fe-O bond.

[0069] Example 3

[0070] Prepare 50 mL of solutions containing phosphate, phosphite, and nickel chloride complexed phosphite respectively, where the concentrations of phosphate, phosphite, and nickel chloride complexed phosphite are all 1 mmol / L, adjust the pH values to 8.0, add 0.08 g of the oxidant sodium persulfate and 1.5 g of Cc-BA-MIL-88(B)@Cs prepared in Example 1 and Cc-(0% - 50%)BA-MIL-88(B)@Cs prepared in Comparative Example 3 respectively, oscillate for 24 h at room temperature of 25 °C, and use the ammonium molybdate spectrophotometry (GB / T 11893 - 1989) to measure the inorganic phosphorus concentration in the solution. The maximum adsorption capacities of Cc-BA-MIL-88(B)@Cs prepared in Example 1 and Cc-(0% - 50%)BA-MIL-88(B)@Cs prepared in Comparative Example 3 for phosphate, phosphite, and nickel chloride complexed phosphite in the solution are as Figure 4 shown in Table 2.

[0071] Table 2 Adsorption results for solutions containing phosphate, phosphite, and nickel chloride complexed phosphite

[0072]

[0073] As can be seen from Table 2 and Figure 4 it can be known that when the proportion of benzoic acid is 20%, that is, under the preparation conditions of Example 1, the prepared biomass-based modified iron-based organic framework composite material has the best adsorption effect on phosphate, phosphite, and phosphite containing nickel chloride, proving that the ratio of benzoic acid to terephthalic acid of 2:8 in Example 1 is the best ratio.

[0074] Example 4

[0075] Prepare 50 mL of solutions with nickel chloride and phosphite concentrations of 0.25, 0.5, 1, 2, and 4 mmol / L respectively, adjust the pH values to 8.0, add 0.04 g of the oxidant sodium persulfate and 0.5 g of Cc-BA-MIL-88(B)@Cs prepared in Example 1 respectively, oscillate for 24 h at 15 °C, 25 °C, and 35 °C, and use the ammonium molybdate spectrophotometry (GB / T 11893 - 1989) to measure the phosphite concentration in the solution. The results are shown in Table 3, Table 4, Figure 5 and Figure 6 shown below.

[0076] Table 3 Adsorption amounts of Cc-BA-MIL-88(B)@Cs for phosphite at different phosphite concentrations and different temperatures

[0077]

[0078]

[0079] Table 4 Fitting parameters of the adsorption isotherm of Cc-BA-MIL-88(B)@Cs on phosphite at different temperatures

[0080]

[0081] As can be seen from Table 3 and Figure 6 it can be known that the maximum adsorption capacity of Cc-BA-MIL-88(B)@Cs prepared in Example 1 for phosphite can reach 2.77 mmol / g at room temperature (25 °C); during the adsorption of phosphite, the adsorption capacity of phosphite increases with the increase of temperature, indicating that the adsorption of phosphite by Cc-BA-MIL-88(B)@Cs is an endothermic process, and nickel chloride promotes the adsorption of phosphite after breaking the complexation.

[0082] As can be seen from Table 4, the adsorption process of the biomass-based modified iron-based metal-organic framework composite Cc-BA-MIL-88(B)@Cs for phosphite conforms better to the Freundlich isotherm, which indicates that Cc-BA-MIL-88(B)@Cs performs multilayer adsorption on the heterogeneous surface to remove phosphite.

[0083] Example 5

[0084] 50 mL of solutions containing 1 mmol / L phosphite were respectively prepared, and 0.5 g of Cc-BA-MIL-88(B)@Cs prepared in Example 1 was added under the conditions of the presence or absence of 0.04 g of oxidant sodium persulfate and the presence or absence of 1 mmol / L nickel chloride, and shaken at 25 °C for 24 h. The concentration of phosphite in the solution was measured by the ammonium molybdate spectrophotometry (GB / T 11893-1989).

[0085] Table 5 Results of the adsorption of 1 mmol / L phosphite with or without oxidant and nickel chloride

[0086]

[0087] As can be seen from Table 5 and Figure 7 it can be known that during the process of the biomass-based modified iron-based metal-organic framework composite Cc-BA-MIL-88(B)@Cs prepared in Example 1 adsorbing the solution of nickel chloride complexed phosphite, there are three processes: directly adsorbing phosphite, oxidizing phosphite to phosphate and then adsorbing it, and nickel promoting adsorption. Among the maximum adsorption capacity of 2.77 mmol / g, the direct adsorption of phosphite is 0.45 mmol / g, the oxidation of phosphite to phosphate and then adsorption is 1.44 mmol / g, and the nickel-promoted adsorption is 0.88 mmol / g. The proportions of the three effects are 16%:52%:32%.

[0088] Example 6

[0089] Prepare 50 mL of solutions containing phosphate, phosphite, and nickel chloride complexed phosphite respectively, with the concentrations of phosphate, phosphite, and nickel chloride complexed phosphite all being 1 mmol / L, and adjust the pH values to 4, 5, 6, 7, 8, 9, and 10 respectively. In the first solution, use the Cc-BA-MIL-88(B)@Cs prepared in Example 1, add 0.08 g of the oxidant sodium persulfate and 1.0 g of the Cc-BA-MIL-88(B)@Cs prepared in Example 1 respectively, and oscillate at 25 °C for 24 h. In the second solution, use the Fenton method, add 5 mL of 27.5% hydrogen peroxide and 0.02 g of ferrous sulfate respectively, and oscillate at 25 °C for 24 h. In the third solution, use the biological method, add 1.0 g of polyphosphate-accumulating organisms respectively, and oscillate at 25 °C for 24 h. Determine the concentration of phosphite in the solution by the ammonium molybdate spectrophotometric method (GB / T 11893-1989). Determine the concentration of iron ions in the first solution by the flame atomic absorption spectrophotometric method (GB / T 11911-1989). The results are shown in Table 6 and Figure 8 as follows.

[0090] Table 6 Comparison results of the adsorption effect of Cc-BA-MIL-88(B)@Cs on inorganic phosphorus, the loss of iron ions, and traditional methods under different pH conditions

[0091]

[0092]

[0093] As can be seen from Table 6 and Figure 8 it can be known that Cc-BA-MIL-88(B)@Cs has good adsorption effects in the pH range of 4-10, and the loss of Cc-BA-MIL-88(B)@Cs does not exceed 3%. The results show that the biomass-based material chitosan effectively reduces the loss of the material. Compared with the acidic conditions of the traditional Fenton method and the neutral to alkaline conditions of the biological method, the applicable pH for Cc-BA-MIL-88(B)@Cs to adsorb and remove inorganic phosphorus is 4-10, with a wider range.

[0094] Example 7

[0095] Adsorb inorganic phosphorus in actual nickel-containing electroplating wastewater. Prepare 6 groups of 50 mL of nickel-containing electroplating wastewater (the components are shown in Table 7), add 0.04 g of the oxidant sodium persulfate and 0.5 g of the Cc-BA-MIL-88(B)@Cs prepared in Example 1 respectively, oscillate at room temperature of 25 °C for 24 h, and determine the concentration of phosphite in the solution by the ammonium molybdate spectrophotometric method (GB / T11893-1989). The results are shown in Table 8 and Figure 9 as follows.

[0096] Table 7 Main components of nickel-containing electroplating wastewater

[0097] Component or property Content Phosphate 0.34 mg / L Phosphite 0.6 mg / L Nickel ion 0.31 mg / L pH value 7.27 Temperature 23.4℃ Conductivity 177 μs / cm COD 240 mg / L Sulfate ion 0.14 mg / L

[0098] Table 8 Results of actual adsorption of inorganic phosphorus in nickel-containing electroplating wastewater by Cc-BA-MIL-88(B)@Cs

[0099]

[0100]

[0101] As can be seen from Table 8 and Figure 9 it can be known that the average removal rate of Cc-BA-MIL-88(B)@Cs for nickel-containing electroplating wastewater with an initial concentration of 0.94 mg / L of phosphite exceeds 90%, indicating that Cc-BA-MIL-88(B)@Cs has excellent ability to adsorb various forms of inorganic phosphorus in actual electroplating wastewater.

[0102] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for removing polymorphic inorganic phosphorus, characterized in that: Adding a biomass-based-modified iron-based organic framework composite material and sodium persulfate in a mass ratio of 0.5-1.5:0.04-0.08 to nickel-containing electroplating wastewater, and oscillating and adsorbing at room temperature to remove polymorphic inorganic phosphorus in the nickel-containing electroplating wastewater; wherein the polymorphic inorganic phosphorus includes phosphate, phosphite, and nickel-complexed phosphite; the nickel-containing electroplating wastewater contains 0.25-4 mmol / L of nickel ions and phosphite; The preparation process of the biomass-based-modified iron-based organic framework composite material comprises the following steps: 1) Benzoic acid, terephthalic acid, ferric chloride hexahydrate and N,N-dimethylformamide are uniformly mixed to form a precursor, the precursor is subjected to a hydrothermal reaction, centrifuged and then dried to obtain BA-MIL-88 (B); 2) calcining the BA-MIL-88 (B) obtained in step 1) to obtain a modified iron-based organic framework Cc-BA-MIL-88 (B); 3) adding the modified iron-based organic framework Cc-BA-MIL-88 (B), chitosan and a crosslinking agent obtained in step 2) into an acetic acid solution, mixing them evenly, and then heating them in a water bath at 60° C. for crosslinking for 2 h to obtain a mixed material; 4) dropping the mixture obtained in step 3) into a mixed solution containing sodium hydroxide, sodium sulfate, anhydrous ethanol and water to obtain a hydrogel; placing the obtained hydrogel in a diluted cross-linking agent to enhance the mechanical strength, washing and drying at room temperature to obtain a biomass-based-modified iron-based organic framework composite material.

2. The method for removing polymorphic inorganic phosphorus according to claim 1, characterized in that: The mmol / mmol / mmol / mL ratio of benzoic acid, terephthalic acid, ferric chloride hexahydrate and N,N-dimethylformamide is 3.2:12.8:16:

100.

3. The method for removing polymorphic inorganic phosphorus according to claim 1, characterized in that: The calcination is carried out in a nitrogen atmosphere at a temperature of 400° C. for a time of 4-6 hours.

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