A modified attapulgite-reinforced sodium alginate hydrogel and its uses and usage methods

Abstract

The present invention provides a modified attapulgite-reinforced sodium alginate hydrogel and its uses and usage methods. Its preparation method includes: calcining the pretreated attapulgite clay; preparing a mixed solution of a titanium salt and a cerium salt, adding the attapulgite clay, adjusting the pH value to 6.75 - 7.25, subjecting the formed mixed suspension to heat treatment, and then obtaining titanium / cerium-modified attapulgite clay after filtration, washing, drying, and grinding and sieving; putting sodium alginate powder and titanium / cerium-modified attapulgite clay into deionized water, and obtaining a uniform suspension after stirring, ultrasonic treatment, and standing; dropping the uniform suspension into a crosslinking solution, and obtaining the modified attapulgite-reinforced sodium alginate hydrogel after the reaction beads are washed and freeze-dried. The modified attapulgite-reinforced sodium alginate hydrogel in the present invention has a significant selective adsorption effect on inositol hexaphosphate in water bodies.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a modified attapulgite reinforced sodium alginate hydrogel, its uses and usage methods. Background Art

[0002] Studies have shown that when the phosphorus concentration in water exceeds 10 μg / L, there is a risk of causing eutrophication. Eutrophication not only leads to water quality deterioration and a decrease in the stability of the ecosystem, but also affects the safety of water supply and endangers human health.

[0003] Phosphorus in the water environment can be divided into two parts: inorganic phosphorus and organic phosphorus. At present, a large number of studies have been carried out on inorganic phosphorus, mainly phosphates, in water environments such as lake sediments, and the methods are relatively mature. Organic phosphorus is an important part of phosphorus in the lake water environment. In lake sediments in different regions of China, the content of organic phosphorus can account for about 30% of the total phosphorus in lake sediments, and the proportion of organic phosphorus in eutrophic lakes is even higher. Organic phosphorus is an important part of the phosphorus cycle in the water environment. In particular, the biogeochemical cycle process of organic phosphorus has become one of the important sources of endogenous phosphorus in some eutrophic lakes, and may become one of the important factors for the self-regulation of the phosphorus nutrient level in lake water. However, due to the complex composition and structural characteristics of organic phosphorus, compared with inorganic phosphorus, the understanding of the composition and biogeochemical cycle process of organic phosphorus and its relationship with water eutrophication and the process of cyanobacterial bloom is still very limited so far.

[0004] Among the components of organic phosphorus, inositol phosphates are one of the main components of organic phosphorus in sediments. According to the number of phosphate groups in the molecule, inositol phosphates include inositol monophosphate to inositol hexaphosphate, and also include various isomers such as myo-inositol hexaphosphate, scyllo-inositol hexaphosphate and neo-inositol hexaphosphate in inositol hexaphosphate. Among them, myo-inositol hexaphosphate is the most common isomer, generally called phytic acid phosphorus. Phytic acid phosphorus has high biological availability and can even be directly absorbed and utilized by some microorganisms in the water environment. Therefore, inositol hexaphosphate is an effective phosphorus source that causes algal blooms in lakes. For example, existing studies have shown that there is a direct relationship between inositol hexaphosphate and algal blooms in Dianchi Lake, China. In addition to being an important factor causing algal blooms, inositol hexaphosphate also widely exists in fishpond effluent or livestock manure wastewater. As phytic acid salt, inositol hexaphosphate widely exists in plant-based feeds. Since inositol hexaphosphate cannot be directly absorbed by fish or herbivores, it will be excreted with feces, resulting in an increase in the content of inositol hexaphosphate in fishpond effluent and causing the problem of phosphorus exceeding the standard. In addition, inositol hexaphosphate is easily complexed with metal ions in natural water bodies to form precipitates, stored in sediments, and released again under specific conditions, increasing the difficulty of water treatment.

[0005] The above water problems caused by inositol hexaphosphate have caused great troubles to environmental governance. In the prior art, the adsorption and phosphorus removal method is one of the most mature and effective methods in the field of phosphorus-containing wastewater treatment. The adsorption and phosphorus removal technology uses solid materials with a high specific surface area or specific adsorption effects on target pollutants, and adsorbs phosphates in water to the surface or internal pores of the material through physical or chemical adsorption forces to achieve the separation and removal of phosphates in water. However, most of the current phosphorus removal adsorbents are applied to the removal of inorganic phosphates, and rarely applied to the adsorption and removal of organic phosphorus. Especially for inositol hexaphosphate, there is a lack of phosphorus removal adsorbents with practical application value. Therefore, the preparation of an inositol hexaphosphate adsorbent with high adsorption capacity and the potential for adsorbent recovery is of great significance in this field. Summary of the Invention

[0006] The technical problem solved by the present invention is the lack of a phosphorus adsorbent in the prior art that can achieve efficient recovery and resource utilization of organic phosphorus. Furthermore, a modified attapulgite-reinforced sodium alginate hydrogel with high adsorption capacity and the potential for adsorbent recovery, its uses, and methods of use are provided.

[0007] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0008] A preparation method of a modified attapulgite-reinforced sodium alginate hydrogel, comprising the following steps: (1) Calcining the pretreated attapulgite clay at 400-700 °C for 2-4 h; (2) Preparing a mixed solution of a titanium salt and a cerium salt, wherein the molar ratio of the titanium salt to the cerium salt in the mixed solution is 1-6, stirring the mixed solution and adding the attapulgite clay prepared in step (1), adding a NaOH solution to adjust the pH value of the solution to 6.75-7.25, and subjecting the formed mixed suspension to heat treatment at 160-180 °C and a pressure of 3-8 Mpa for 20-24 h; (3) Filtering the heat-treated suspension, washing, drying, and sieving the filtered solid to obtain titanium / cerium-modified attapulgite clay; (4) Putting sodium alginate powder and the titanium / cerium-modified attapulgite clay into deionized water according to a mass ratio of 6:1-2:1, and obtaining a uniform suspension through stirring, ultrasonic treatment, and static treatment; (5) Dropping the uniform suspension obtained in step (4) into a CaCl2 cross-linking solution with a mass concentration of 3 wt%-5 wt% to complete the gel reaction; the obtained gel beads are washed and freeze-dried to obtain the modified attapulgite-reinforced sodium alginate hydrogel.

[0009] In step (1), the method for pretreating the attapulgite clay is: immersing the attapulgite clay in a HCl solution with a mass concentration of 5 wt%, and after standing for 12 h, washing the attapulgite clay to neutral.

[0010] In step (2), the titanium salt is titanium sulfate and the cerium salt is cerium nitrate.

[0011] In step (2), the molar concentration of titanium sulfate in the mixed solution is 0.1 - 0.2 mol / L, and the addition amount of attapulgite clay in the mixed solution is 0.01 - 0.05 g / ml.

[0012] In step (3), the solid obtained by filtration is washed successively with ethanol and deionized water until the pH of the solid is washed to neutral, and then dried at 80°C - 100°C until constant weight is achieved; the dried solid is ground and sieved to obtain the titanium / cerium modified attapulgite clay.

[0013] In step (4), sodium alginate powder and the titanium / cerium modified attapulgite clay are put into deionized water, stirred at 40°C - 50°C for 20 - 24 h, then ultrasonically treated for 30 min - 60 min, and finally left standing to obtain a uniform suspension.

[0014] In step (5), the uniform mixture is dropped into a 3 wt% CaCl2 cross-linking solution and left for 36 h - 48 h to complete the gel reaction; the obtained gel beads are washed with deionized water and then freeze-dried at -49°C to obtain the modified attapulgite reinforced sodium alginate hydrogel.

[0015] The modified attapulgite reinforced sodium alginate hydrogel prepared by the described preparation method.

[0016] Use of the modified attapulgite reinforced sodium alginate hydrogel for removing / recovering inositol hexaphosphate in water bodies.

[0017] The usage method of the modified attapulgite reinforced sodium alginate hydrogel includes the following steps: adding the modified attapulgite reinforced sodium alginate hydrogel to the water body, and the addition concentration is 0.4 - 1 g / L.

[0018] The advantages of the technical solution of the modified attapulgite reinforced sodium alginate hydrogel, its usage and usage method described in the present invention are as follows:

[0019] The modified attapulgite reinforced sodium alginate hydrogel described in the present invention loads titanium / cerium on pretreated attapulgite clay. After hydrothermal treatment under high pressure, it forms a homogeneous mixed solution with sodium alginate, and then is dropped into a CaCl2 cross-linking solution. Finally, the prepared modified attapulgite reinforced sodium alginate hydrogel has a significant selective adsorption effect on inositol hexaphosphate in water and can realize the recycling of the adsorbent. Among them, in this application, by loading titanium / cerium, the active sites of the composite adsorbent can be significantly increased. Due to the specific adsorption ability of titanium / cerium to the phosphate groups of inositol hexaphosphate, the adsorption selectivity of the composite adsorbent for inositol hexaphosphate is improved; the combination of titanium metal and cerium metal, and at the same time, through hydrothermal treatment under high pressure, the crystal structure of titanium oxide / cerium metal develops better, thus further increasing the adsorption performance for organic phosphorus. In this application, the adsorbent is made into a hydrogel, realizing the recycling after the application of the adsorbent. At the same time, the micron-scale hydrogel adsorbent prepared in this application has a three-dimensional network structure. This type of adsorbent swells when it meets water, and its three-dimensional size increases accordingly. Therefore, the mass transfer resistance during the adsorption process can be greatly reduced, enabling the adsorption system to quickly reach adsorption equilibrium. Compared with traditional adsorbents, this adsorbent mainly uses the three-dimensional network and the titanium / cerium groups loaded on the network for adsorption. Compared with other types of adsorbents, the super adsorbent has obvious advantages such as large adsorption capacity, fast adsorption rate and recyclability, and will not cause secondary pollution. It is an adsorption material for removing inositol hexaphosphate with environmental friendliness and sustainable development.

[0020] In order to make the technical solutions of a modified attapulgite reinforced sodium alginate hydrogel and its uses and usage methods described in the present invention clearer and more understandable, the following further illustrates the present invention in conjunction with specific embodiments. Specific embodiments

[0021] Example 1

[0022] This embodiment provides a modified attapulgite reinforced sodium alginate hydrogel. The preparation method of the modified attapulgite reinforced sodium alginate hydrogel includes the following steps:

[0023] (1) Pretreatment of attapulgite clay: Immerse the powdered attapulgite clay in a 5% by mass HCl solution. The particle size range of the attapulgite clay is 20 - 75 microns; soak it in the HCl solution for 12 hours, then wash the attapulgite clay with deionized water until it is neutral, and then place the attapulgite clay in a muffle furnace and calcine it at 700 °C for 2 h.

[0024] (2) Titanium / Cerium Modified Attapulgite: A 0.2 mol / L titanium sulfate (Ti(SO4)2) solution and a 0.2 mol / L cerium nitrate (Ce(NO3)3) solution were mixed in a volume ratio of 6:1. The molar ratio of titanium sulfate to cerium nitrate in the mixed solution was 6:1, and the total volume of the mixed solution was 49 mL. The mixed solution was continuously stirred, and 2 g of the attapulgite clay prepared in step (1) was added during the stirring process, and further stirred evenly. The pH value of the solution was adjusted to 7.0 with 4 mol / L NaOH solution. The formed mixed suspension was transferred to a stainless-steel autoclave with a PTFE liner. The temperature of the autoclave was set to 180 °C, and it was pressurized at 5 Mpa for 24 h.

[0025] (3) Drying: The liquid after the pressure treatment in step (2) was filtered, and then the precipitate was washed successively with ethanol and deionized water until the pH of the precipitate reached neutral. Then it was dried at 80 °C until constant weight, ground and sieved to obtain titanium / cerium modified attapulgite clay. The obtained modified attapulgite clay was stored in a desiccator for further hydrogel synthesis.

[0026] (4) 2 g of sodium alginate powder and 1 g of the titanium / cerium modified attapulgite clay were put into 150 ml of deionized water, stirred at 40 °C for 24 h, and then ultrasonically treated for 30 min to remove bubbles, obtaining a uniform suspension.

[0027] (5) After standing for 2 h, the uniform suspension prepared in step (4) was dropped into the cross-linking solution through an automatic injection pump to generate hydrogel beads. The cross-linking solution was a CaCl2 solution, and the mass concentration of CaCl2 in the CaCl2 solution was 3 wt%. The newly formed hydrogel beads were placed in the cross-linking mother liquor for 48 h to ensure complete gel reaction. Then the obtained wet gel beads were washed with deionized water to remove excess reagents, and freeze-dried at -49 °C to obtain dry beads, which were the modified attapulgite reinforced sodium alginate hydrogel.

[0028] Example 2

[0029] This embodiment provides a modified attapulgite reinforced sodium alginate hydrogel. The preparation method of the modified attapulgite reinforced sodium alginate hydrogel includes the following steps:

[0030] (1) Pretreatment of Attapulgite Clay: The powdery attapulgite clay with a particle size range of 20 - 75 microns was immersed in a 5% HCl solution for 12 hours, then washed with deionized water until neutral, and then placed in a muffle furnace and calcined at 400 °C for 4 h.

[0031] (2) Titanium / Cerium Modified Attapulgite: A 0.2 mol / L titanium sulfate (Ti(SO4)2) solution and a 0.2 mol / L cerium nitrate (Ce(NO3)3) solution were mixed in a volume ratio of 1:1. The molar ratio of titanium sulfate to cerium nitrate in the mixed solution was 1, and the total volume of the mixed solution was 50 mL. The mixed solution was continuously stirred, and 2 g of the attapulgite clay prepared in step (1) was added during the stirring process, and then further stirred evenly; the pH value of the solution was adjusted to 7.0 with 4 mol / L NaOH solution; the formed mixed suspension was transferred to a stainless steel autoclave with a polytetrafluoroethylene liner, the temperature of the autoclave was set at 180 °C, and it was pressurized at 3 Mpa for 24 h.

[0032] (3) Drying: The liquid after the pressure treatment in step (2) was filtered, and then the precipitate was washed successively with ethanol and deionized water until the pH of the precipitate reached neutral, and then dried at 80 °C until constant weight, ground and sieved to obtain titanium / cerium modified attapulgite clay. The obtained modified attapulgite clay was stored in a desiccator for further hydrogel synthesis.

[0033] (4) 6 g of sodium alginate powder and 1 g of the titanium / cerium modified attapulgite clay were put into 150 ml of deionized water, stirred at 40 °C for 24 h, and then ultrasonically treated for 30 min to remove bubbles to obtain a uniform suspension.

[0034] (5) After standing for 2 h, the uniform suspension prepared in step (4) was dropped into the crosslinking solution through an automatic injection pump to generate hydrogel beads. The crosslinking solution was a CaCl2 solution, and the mass concentration of CaCl2 in the CaCl2 solution was 5 wt%; the newly formed hydrogel beads were placed in the crosslinking mother liquor for 48 h to ensure complete gel reaction; then the obtained wet gel beads were washed with deionized water to remove excess reagents, and freeze-dried at -49 °C to obtain dry beads, which were the modified attapulgite reinforced sodium alginate hydrogel.

[0035] Example 3

[0036] This embodiment provides a modified attapulgite reinforced sodium alginate hydrogel. The preparation method of the modified attapulgite reinforced sodium alginate hydrogel includes the following steps:

[0037] (1) Pretreatment of Attapulgite Clay: The powdery attapulgite clay with a particle size range of 20 - 75 microns was immersed in a 5% HCl solution for 12 hours, then washed with deionized water until neutral, and then the attapulgite clay was placed in a muffle furnace and calcined at 600 °C for 2 h.

[0038] (2) Titanium / Cerium Modified Attapulgite: A 0.2 mol / L titanium sulfate (Ti(SO4)2) solution and a 0.2 mol / L cerium nitrate (Ce(NO3)3) solution were mixed according to a volume ratio of 3:1. The molar ratio of titanium sulfate to cerium nitrate in the mixed solution was 3, and the total volume of the mixed solution was 50 mL. The mixed solution was continuously stirred, and 2 g of the attapulgite clay prepared in step (1) was added during the stirring process, and further stirred evenly; the pH value of the solution was adjusted to 7 with 4 mol / L NaOH solution; the formed mixed suspension was transferred to a stainless-steel autoclave with a polytetrafluoroethylene lining, the temperature of the autoclave was set at 180 °C, and it was treated under 8 Mpa for 24 h.

[0039] (3) Drying: The liquid after the pressure treatment in (2) was filtered, and then the precipitate was washed successively with ethanol and deionized water until the pH of the precipitate reached neutral, and then dried at 80 °C until constant weight, ground and sieved to obtain titanium / cerium modified attapulgite clay. The obtained modified attapulgite clay was stored in a desiccator for further hydrogel synthesis.

[0040] (4) 3 g of sodium alginate powder and 1 g of the titanium / cerium modified attapulgite clay were put into 150 ml of deionized water, stirred at 40 °C for 24 h, and then ultrasonically treated for 30 min to remove bubbles to obtain a uniform suspension.

[0041] (5) After standing for 2 h, the uniform suspension prepared in step (4) was dropped into the cross-linking solution through an automatic injection pump to generate hydrogel beads. The cross-linking solution was a CaCl2 solution, and the mass concentration of CaCl2 in the CaCl2 solution was 5 wt%; the newly formed hydrogel beads were placed in the cross-linking mother liquor for 48 h to ensure a complete gel reaction; then the obtained wet gel beads were washed with deionized water to remove excess reagents, and freeze-dried at -49 °C to obtain dry beads, which were the modified attapulgite reinforced sodium alginate hydrogel.

[0042] When the cerium / titanium modified attapulgite reinforced hydrogel sphere phosphorus adsorbent prepared in the above Examples 1-3 was used, the phosphorus adsorbent was added to the water body at a dosage concentration of 0.2 - 0.6 g / L. After adsorption, the phosphorus adsorbent was filtered out from the water body to obtain the phosphorus adsorbent after adsorbing phosphorus.

[0043] Experimental Example

[0044] In order to verify the technical effect of the phosphorus adsorbent described in this application, a phosphorus adsorption experiment was carried out on the phosphorus adsorbents prepared in Examples 1-3. The experimental method was as follows:

[0045] Three groups of phytic acid solutions were prepared. The concentration of phytic acid in each group of solutions was 5 - 90 mg / L in terms of P, and the concentration gradients in each group were set as 5 mg / L, 10 mg / L, 15 mg / L, 25 mg / L, 40 mg / L, 60 mg / L, and 90 mg / L respectively. The three groups of phosphorus-removing adsorbents prepared in Examples 1 - 3 were respectively put into the three groups of solutions. The dosage of the phosphorus-removing adsorbent in each concentration of the solution was 0.4 g / L. When the adsorption reached equilibrium, the maximum adsorption capacity of the phosphorus-removing adsorbent added to each group of solutions in the three groups of solutions was measured. The calculation method of the phosphorus adsorption capacity of the phosphorus-removing adsorbent added to each solution is as follows:

[0046] Phosphorus adsorption capacity = (phosphorus content in the original solution - phosphorus content in the solution after treatment with the phosphorus-removing adsorbent) / mass of the phosphorus-removing adsorbent;

[0047] The results showed that the maximum adsorption capacities of the phosphorus-removing adsorbents in Examples 1, 2, and 3 were 42 mg P / g, 47 mg P / g, and 49 mg P / g in sequence.

[0048] Comparative example

[0049] To further verify the technical effects of the phosphorus-removing adsorbent described in this application, the following comparative examples were set up for comparative experiments.

[0050] Comparative example 1

[0051] The preparation method of the phosphorus removal adsorbent in this comparative example includes the following steps: (1) Mix a 0.2 mol / L titanium sulfate (Ti(SO4)2) solution and a 0.2 mol / L cerium nitrate (Ce(NO3)3) solution according to a volume ratio of 6:1. The molar ratio of titanium sulfate to cerium nitrate in the mixed solution is 6:1, and the volume of the mixed solution is 49 mL. Continuously stir the mixed solution and add 2 g of untreated attapulgite clay powder during the stirring process, and further stir evenly; adjust the pH value of the solution to 7.0 with a 4 mol / L NaOH solution; transfer the formed mixed suspension to a stainless steel autoclave with a polytetrafluoroethylene liner, set the temperature of the autoclave to 180 °C, and carry out pressure treatment at 5 Mpa for 24 h. (2) Drying: Filter the liquid after the pressure treatment in step (1), then wash the precipitate with ethanol and deionized water in sequence, wash the precipitate to a neutral pH, and then dry it at 80 °C until constant weight is achieved, grind it and sieve it to obtain titanium / cerium modified attapulgite clay. (3) Put 2 g of sodium alginate powder and 1 g of the titanium / cerium modified attapulgite clay into 150 ml of deionized water, stir at 40 °C for 24 h, and then carry out ultrasonic treatment for 30 min to remove bubbles to obtain a uniform suspension. (4) After standing for 2 h, drop the uniform suspension prepared in step (3) into the cross-linking solution through an automatic injection pump to generate hydrogel beads. The cross-linking solution uses a CaCl2 solution, and the mass concentration of CaCl2 in the CaCl2 solution is 3 wt%; the newly formed hydrogel beads are placed in the cross-linking mother liquor for 48 h to ensure a complete gel reaction; then wash the obtained wet gel beads with deionized water to remove excess reagents, and obtain dry beads by freeze-drying at -49 °C, which is the phosphorus removal adsorbent.

[0052] Comparative Example 2

[0053] The preparation method of the phosphorus removal adsorbent in this comparative example includes the following steps: (1) Pretreatment of attapulgite clay: Immerse the powdery attapulgite clay with a particle size range of 20-75 microns in a 5% HCl solution for 12 hours, then wash the attapulgite clay until it is neutral, and then place the attapulgite clay in a muffle furnace and calcine it at 700 °C for 2 hours. (2) Titanium / cerium modified attapulgite: Mix a 0.2 mol / L titanium sulfate (Ti(SO4)2) solution and a 0.2 mol / L cerium nitrate (Ce(NO3)3) solution according to a volume ratio of 6:1. The molar ratio of titanium sulfate to cerium nitrate in the mixed solution is 6:1, and the total volume of the mixed solution is 49 mL. Continuously stir the mixed solution and add 2 g of the attapulgite clay prepared in step (1) during the stirring process, and further stir evenly; adjust the pH value of the solution to 7.0 with a 4 mol / L NaOH solution. (3) Drying: Filter the solution after the reaction in step (2), then wash the precipitate with ethanol and deionized water in sequence until the precipitate is washed to a neutral pH, and then place it in an 80 °C environment and dry it until it reaches constant weight, grind it and pass it through a sieve to obtain titanium / cerium modified attapulgite clay. (4) Put 2 g of sodium alginate powder and 1 g of the titanium / cerium modified attapulgite clay into 150 ml of deionized water, stir at 40 °C for 24 hours, and then perform ultrasonic treatment for 30 minutes to remove bubbles to obtain a uniform suspension. (5) After standing for 2 hours, drop the uniform suspension prepared in step (4) into the crosslinking solution through an automatic injection pump to generate hydrogel beads. The crosslinking solution uses a CaCl2 solution, and the mass concentration of CaCl2 in the CaCl2 solution is 3 wt%; the newly formed hydrogel beads are placed in the crosslinking mother liquor for 48 hours to ensure a complete gel reaction; then wash the obtained wet gel beads with deionized water to remove excess reagents, and freeze-dry them at -49 °C to obtain dry beads, which are the phosphorus removal adsorbent.

[0054] Comparative Example 3

[0055] This comparative example provides a modified attapulgite-reinforced sodium alginate hydrogel. The preparation method of the modified attapulgite-reinforced sodium alginate hydrogel includes the following steps: (1) Pretreatment of attapulgite clay: Immerse powdery attapulgite clay with a particle size range of 20-75 microns in a 5% (by mass) HCl solution for 12 hours, then wash the attapulgite clay until neutral, and then place the attapulgite clay in a muffle furnace and calcine it at 700 °C for 2 h. (2) Titanium-modified attapulgite: Prepare 49 mL of a 0.2 mol / L titanium sulfate (Ti(SO4)2) solution, add 2 g of the attapulgite clay prepared in step (1) under stirring, and stir evenly; adjust the pH value of the solution to 7.0 with a 4 mol / L NaOH solution; transfer the formed mixed suspension to a stainless steel autoclave with a polytetrafluoroethylene liner, set the temperature of the autoclave to 180 °C, and carry out pressure treatment at 5 Mpa for 24 h. (3) Drying: Filter the liquid after the pressure treatment in step (2), then wash the precipitate with ethanol and deionized water in sequence until the precipitate is washed to a neutral pH, then place it at 80 °C and dry until constant weight, grind and sieve to obtain titanium-modified attapulgite clay. (4) Put 2 g of sodium alginate powder and 1 g of the titanium-modified attapulgite clay into 150 ml of deionized water, stir at 40 °C for 24 h, and then carry out ultrasonic treatment for 30 min to remove bubbles to obtain a uniform suspension. (5) After standing for 2 h, drop the uniform suspension prepared in step (4) into a crosslinking solution through an automatic injection pump to generate hydrogel beads. The crosslinking solution uses a CaCl2 solution, and the mass concentration of CaCl2 in the CaCl2 solution is 3 wt%; the newly formed hydrogel beads are placed in the crosslinking mother liquor for 48 h to ensure a complete gel reaction; then wash the obtained wet gel beads with deionized water to remove excess reagents, and obtain dry beads by freeze-drying at -49 °C, which is the phosphorus adsorption agent.

[0056] Comparative Example 4

[0057] This comparative example provides a modified attapulgite-reinforced sodium alginate hydrogel. The preparation method of the modified attapulgite-reinforced sodium alginate hydrogel comprises the following steps: (1) Pretreatment of attapulgite clay: Immerse the powdered attapulgite clay in a 5% (by mass) HCl solution for 12 hours, then wash the attapulgite clay until neutral, and then place the attapulgite clay in a muffle furnace and calcine it at 700 °C for 2 h. (2) Cerium-modified attapulgite: Prepare 49 mL of a 0.2 mol / L cerium nitrate (Ce(NO3)3) solution, continuously stir the mixed solution and add 2 g of the attapulgite clay prepared in step (1) during the stirring process, and further stir evenly; adjust the pH value of the solution to 7.0 with a 4 mol / L NaOH solution; transfer the formed mixed suspension to a stainless steel autoclave with a PTFE liner, set the temperature of the autoclave to 180 °C, and carry out pressure treatment at 5 Mpa for 24 h. (3) Drying: Filter the liquid after the pressure treatment in step (2), then wash the precipitate with ethanol and deionized water in sequence until the precipitate is washed to a neutral pH, then place it in an 80 °C oven and dry it until it reaches a constant weight, grind it and sieve it to obtain cerium-modified attapulgite clay. (4) Put 2 g of sodium alginate powder and 1 g of the cerium-modified attapulgite clay into 150 ml of deionized water, stir at 40 °C for 24 h, and then carry out ultrasonic treatment for 30 min to remove bubbles to obtain a uniform suspension. (5) After standing for 2 h, drop the uniform suspension prepared in step (4) into a crosslinking solution through an automatic injection pump to generate hydrogel beads. The crosslinking solution is a CaCl2 solution, and the mass concentration of CaCl2 in the CaCl2 solution is 3 wt%; the newly formed hydrogel beads are placed in the crosslinking mother liquor for 48 h to ensure a complete gel reaction; then wash the obtained wet gel beads with deionized water to remove excess reagents, and freeze-dry them at -49 °C to obtain dry beads, which are the phosphorus adsorption agent.

[0058] Perform a phosphorus adsorption experiment on the phosphorus adsorption agents prepared in Comparative Examples 1-4. The experimental method is the same as that in the experimental example. The results show that the maximum adsorption capacities of the phosphorus adsorption agents in Comparative Examples 1, 2, 3, and 4 are 28 mg P / g, 26 mg P / g, 31 mg P / g, and 34 mg P / g, respectively.

[0059] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the claims.

Claims

1. Use of a modified attapulgite reinforced sodium alginate hydrogel for removing inositol hexaphosphate from water, characterized in that, The preparation method of the modified attapulgite reinforced sodium alginate hydrogel comprises the following steps: (1) Calcining the pretreated attapulgite clay at 400-700 °C for 2-4 h; (2) Preparing a mixed solution of a titanium salt and a cerium salt, wherein the molar ratio of the titanium salt to the cerium salt in the mixed solution is 1-6, stirring the mixed solution and adding the attapulgite clay prepared in step (1), adding NaOH to adjust the pH value of the mixed solution to 6.75-7.25, and subjecting the formed mixed suspension to heat treatment at 160-180 °C and a pressure of 3-8 Mpa for 20-24 h; (3) Filtering the suspension after heat treatment, washing, drying and sieving the obtained solid by grinding to obtain titanium / cerium modified attapulgite clay; (4) Putting sodium alginate powder and the titanium / cerium modified attapulgite clay into deionized water according to a mass ratio of 2-6, and performing stirring, ultrasonic treatment and static treatment to obtain a uniform suspension; (5) Dropping the uniform suspension obtained in step (4) into a CaCl2 crosslinking solution with a mass concentration of 3 wt%-5 wt% to complete the gel reaction; the obtained gel beads are washed and freeze-dried to obtain the modified attapulgite reinforced sodium alginate hydrogel.

2. Use of the modified attapulgite reinforced sodium alginate hydrogel according to claim 1 for removing inositol hexaphosphate from water, characterized in that, In step (1), the method for pretreating the attapulgite clay is: immersing the attapulgite clay in a HCl solution with a mass concentration of 5 wt%, and after standing for 12 h, washing the attapulgite clay to neutrality.

3. Use of the modified attapulgite reinforced sodium alginate hydrogel according to claim 1 for removing inositol hexaphosphate from water, characterized in that, In step (2), the titanium salt is titanium sulfate and the cerium salt is cerium nitrate.

4. Use of the modified attapulgite reinforced sodium alginate hydrogel according to claim 1 for removing inositol hexaphosphate from water, characterized in that In step (2), the molar concentration of titanium sulfate in the mixed solution is 0.1-0.2 mol / L, and the addition amount of the attapulgite clay in the mixed solution is 0.01-0.05 g / ml.

5. Use of the modified attapulgite-reinforced sodium alginate hydrogel according to claim 1 for removing inositol hexaphosphate from water, characterized in that, In step (3), the obtained solid is washed successively with ethanol and deionized water, the pH of the solid is washed to neutrality, and then dried at 80-100 °C until constant weight is reached; the dried solid is sieved by grinding to obtain the titanium / cerium modified attapulgite clay.

6. Use of the modified attapulgite reinforced sodium alginate hydrogel according to claim 1 for removing inositol hexaphosphate from water, characterized in that, In step (4), sodium alginate powder and the titanium / cerium modified attapulgite clay are put into deionized water, stirred at 40-50 °C for 20-24 h, then ultrasonically treated for 30-60 min, and finally a uniform suspension is obtained after standing.

7. Use of the modified attapulgite reinforced sodium alginate hydrogel according to claim 5 for removing inositol hexaphosphate from water, characterized in that In step (5), the uniform suspension is dropped into a CaCl2 crosslinking solution with a mass concentration of 3 wt%, and the gel reaction is completed after standing for 36-48 h; the obtained gel beads are washed with deionized water and then freeze-dried at -49 °C to obtain the modified attapulgite reinforced sodium alginate hydrogel.

8. Use of the modified attapulgite-reinforced sodium alginate hydrogel according to any one of claims 1-7 for removing inositol hexaphosphate from water, characterized in that, When in use, the modified attapulgite reinforced sodium alginate hydrogel is added to the water body, and the addition concentration is 0.4-1 g / L.