A gel ball adsorbent for selective phosphorus removal and its preparation method and application

Abstract

The present invention provides a gel ball adsorbent for selective phosphorus removal and its preparation method and application. The preparation method of the present invention comprises the steps of: 2 O 3 ) is fully dispersed in water to obtain a yttrium oxide dispersion; sodium alginate (SA) is added and fully dissolved to obtain a mixed solution; the mixed solution is added dropwise to the CaCl 2 In the aqueous solution, gel balls are formed, and then the gel ball adsorbent is obtained by washing. The preparation method of the present invention is simple; the obtained adsorbent has good stability, can selectively and efficiently remove phosphate in water, and is easy to separate from water, and the separation process is simple.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a gel ball adsorbent for selective phosphorus removal, and a preparation method and application thereof. Background Art

[0002] Phosphorus (P), as a nutrient element, is one of the key elements necessary for life. However, if the phosphorus content in water is too high, it will lead to eutrophication and other problems, seriously endangering aquatic organisms and the aquatic environment. Phosphorus mainly exists in the form of phosphate in natural water environments. In recent years, with the rapid development of the economy, phosphorus-containing pesticides, fertilizers, detergents and other products are widely used in agriculture and industry. If excessive phosphate is directly discharged into the water without treatment, it will accelerate the eutrophication process, thereby causing abnormal growth of aquatic organisms such as algae, which makes it important to effectively remove and recover phosphate in water.

[0003] At present, a variety of treatment technologies have been developed in the field of phosphorus-containing wastewater treatment, including chemical coagulation, precipitation, biological treatment, ion exchange and adsorption. However, increasingly stringent phosphorus removal regulations have posed challenges to traditional phosphorus removal technologies. For example, chemical precipitation faces the problem of high dosage requirements of metal salts and significantly increased sludge generation rate; biological degradation faces the impact of system stability, such as organic load, toxic substances and reactor operating parameters; physical methods such as electrodialysis face high energy consumption and low selectivity. Because adsorption technology is relatively simple, relatively low cost, and does not produce sludge, it is generally considered to be an effective technology. However, low selective removal rate, poor stability, difficult separation process, and complex preparation methods limit the practical application of some adsorbents in phosphate adsorption.

[0004] Therefore, there is an urgent need to develop an adsorbent with high phosphate selective removal rate, good stability, simple separation process and simple preparation method. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a gel ball adsorbent for selective phosphorus removal and its preparation method and application. The preparation method of the present invention is simple; the obtained adsorbent has good stability, can selectively and efficiently remove phosphate in water, and is easy to separate from water, and the separation process is simple.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A gel ball adsorbent for selective phosphorus removal, wherein the adsorbent is spherical gel particles with a particle size of 1.8-2.4 mm and a wrinkled and rough surface.

[0008] Preferably, according to the present invention, the gel ball adsorbent is prepared from sodium alginate and nano-yttrium oxide as main raw materials; in the spherical gel particles, the nano-yttrium oxide is uniformly dispersed on the surface or inside of the spherical gel particles.

[0009] The preparation method of the gel ball adsorbent for selective phosphorus removal comprises the following steps:

[0010] (1) Nano yttrium oxide (Y 2 O 3 ) is fully dispersed in water to obtain a yttrium oxide dispersion; sodium alginate (SA) is added and fully dissolved to obtain a mixed solution;

[0011] (2) Add the mixed solution dropwise to the CaCl 2 In the aqueous solution, gel balls are formed, and then the gel ball adsorbent is obtained by washing.

[0012] Preferably, according to the present invention, in step (1), the mass concentration of the yttrium oxide dispersion is 1% to 2%.

[0013] Preferably, according to the present invention, in step (1), the mass ratio of nano yttrium oxide to sodium alginate is 0.25:1 to 1.5:1; preferably, the mass ratio of nano yttrium oxide to sodium alginate is 0.75:1 to 1:1. This ratio can ensure that the surface of the gel ball is uniformly coated with nano yttrium oxide particles to the maximum extent, reduce the loss of effective adsorption sites of the adsorbent, and make the adsorbent have excellent selective phosphorus removal effect; it can also ensure that the prepared gel ball adsorbent has good mechanical strength. And provide sufficient viscosity so that the nano yttrium oxide can overcome the gravity in the mixed solution and can be evenly dispersed in the gel ball adsorbent. If the addition ratio of SA is too low, the cross-linking degree is insufficient and the gel ball particles are difficult to form. If the addition ratio is too high, the cross-linking degree is too large, which reduces the effective adsorption sites of the adsorbent and affects the final adsorption effect of the gel ball adsorbent.

[0014] According to the preferred embodiment of the present invention, in step (1), the dissolution of sodium alginate is carried out under stirring at 40-50° C. This ensures that SA is completely dissolved in water at 40-50° C.

[0015] According to the preferred embodiment of the present invention, in step (2), CaCl 2 The mass concentration of the aqueous solution is 0.1% to 4%.

[0016] According to the preferred embodiment of the present invention, in step (2), the mixed solution and CaCl 2 The volume ratio of the aqueous solution is 1:1-10.

[0017] Preferably, in step (2), a peristaltic pump is used to drip the mixed solution drop by drop; the flow rate is 1 to 5 mL / min, preferably 2 to 3 mL / min. This flow rate range can ensure that the nano-yttrium oxide of the gel ball is evenly wrapped on the gel ball. If the dripping flow rate is too slow, yttrium oxide will be deposited on one side of the gel ball at the outlet nozzle of the hose due to factors such as gravity, resulting in uneven dispersion of nano-yttrium oxide in the gel ball. If the dripping flow rate is too fast, the mixed solution will flow out in strips, which is not conducive to the formation of gel balls.

[0018] According to a preferred embodiment of the present invention, in step (2), the mixed solution is added dropwise to the CaCl 2 After being dissolved in aqueous solution, stir for 20-30h.

[0019] According to the present invention, in step (2), washing is performed to remove excess Ca 2+ .

[0020] The gel ball adsorbent for selective phosphorus removal is used as an adsorbent to adsorb and remove phosphates in phosphorus-containing liquids.

[0021] Preferably according to the present invention, the pH of the phosphorus-containing liquid is 2-7; preferably, the pH of the phosphorus-containing liquid is 2.

[0022] Preferably according to the present invention, the phosphate is potassium dihydrogen phosphate.

[0023] According to the preferred embodiment of the present invention, CO can also be added to the phosphorus-containing liquid. 3 2- , SO 4 2- or Cl - To improve the adsorption effect of the gel ball adsorbent; in the phosphorus-containing liquid, the CO 3 2- The concentration of SO is 0.01-0.1 mol / L; in phosphorus-containing liquids, SO 4 2- Or the concentration of Cl- is 0.001-0.1 mol / L, preferably 0.01-0.1 mol / L.

[0024] Technical features and beneficial effects of the present invention:

[0025] (1) The present invention combines nano yttrium oxide and sodium alginate, because Y 2 O 3 There are a lot of hydroxyl groups on the surface, which have good dispersibility and hydrophilicity, and enhance the Y 2 O 3 The interfacial interaction between Y and sodium alginate material 2 O 3 It has good compatibility with sodium alginate.

[0026] (2) The gel ball adsorbent prepared by the present invention has obvious wrinkles and roughness on the surface of the ball, has a large specific surface area, is easy to recycle, does not cause pollution of nanoparticles, and has a good adsorption effect on phosphate, and can effectively adsorb phosphate in water.

[0027] (3) The preparation method of the present invention is simple; in the gel ball adsorbent prepared by the present invention, Y 2 O 3 The adsorption performance can still maintain a good effect. It works together with sodium alginate, so that the obtained adsorbent has a good phosphate adsorption effect, has good ion selectivity for phosphate, and maintains stability in a wide pH range; compared with Y alone, 2 O 3 Or calcium alginate gel balls have better adsorption effect.

[0028] (4) When the gel ball adsorbent of the present invention is used to adsorb and remove phosphate in phosphorus-containing liquids, it maintains relatively stable adsorption performance under strong acidic conditions (pH 2) and has a relatively stable adsorption effect within the acidic range. - , CO 3 2- or SO 4 2- In the coexisting phosphorus-containing liquid, the above ions show a certain promoting effect on the adsorption effect of the adsorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 and 2 are the SEM images and appearance pictures of the gel ball adsorbent prepared in Example 1 of the present invention.

[0030] Figure 2 The adsorption data of phosphate adsorption reaction of the gel ball adsorbent prepared in Examples 1-7 of the present invention and Comparative Example 1 are shown.

[0031] Figure 3 The figure shows the effect of different pH conditions on the adsorption of phosphate by the gel ball adsorbent prepared in Example 1 of the present invention.

[0032] Figure 4 This is the influence of common anions on the phosphate adsorption of the gel ball adsorbent prepared in Example 1 of the present invention.

[0033] Figure 5 is the N of the gel ball adsorbent prepared in Example 1 of the present invention 2 Adsorption / desorption isotherms and corresponding pore size distribution curves. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0035] Meanwhile, the experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents, materials and devices described are all commercially available unless otherwise specified.

[0036] Example 1

[0037] A method for preparing a gel ball adsorbent for selective phosphorus removal comprises the following steps:

[0038] (1) Preparation of 2.0 wt% CaCl 2 Aqueous solution: weigh 2.0 g of anhydrous calcium chloride and dissolve it in 100 mL of deionized water;

[0039] (2) preparing a mixed solution 1: adding 1.5 g of nano-yttrium oxide to 100 ml of deionized water, stirring in a constant temperature heating magnetic stirrer for 20 to 30 min to obtain a uniformly mixed mixed solution 1;

[0040] (3) Preparation of mixed solution 2: Weigh 2.0 g of SA and add it to the uniformly stirred mixed solution 1, heat and stir in a 40° C. water bath to dissolve, and mix thoroughly to obtain mixed solution 2;

[0041] (4) Preparation of gel ball adsorbent: The prepared mixed solution 2 was pumped into one end of the hose through a peristaltic pump and dripped dropwise into the prefabricated 2.0 wt% CaCl 2 In the aqueous solution, the flow rate is 2.5 ml / min, and uniform gel balls are formed. Stir and stabilize in the cross-linking solution for 24 hours, wash with deionized water for many times, filter out the gel balls, and then use absorbent paper to absorb excess water on the surface to obtain the gel ball adsorbent, which is sealed and placed in a refrigerator for low temperature storage.

[0042] Figure 1 The following are the SEM images and appearance pictures of the gel ball adsorbent prepared in this embodiment. As can be seen from the figure, the surface of the gel ball is rough and wrinkled, and the granularity is obvious, which may provide a site for phosphate to be more easily accessible and adsorbed. In addition, obvious pores can be observed in the cross section of the gel ball adsorbent. This porous structure is conducive to the swelling reaction, which facilitates the diffusion of phosphate ions into the gel ball material, provides a larger specific surface area, and is conducive to the adsorption of phosphate anions.

[0043] Figure 5 is the N of the gel ball adsorbent prepared in this example 2 Adsorption / desorption isotherms and corresponding pore size distribution curves. According to the basic BET model analysis, the specific surface area of ​​yttrium oxide sodium alginate gel ball adsorbent is 17.90m 2 / g. According to the BJH model analysis, the pore volume and average pore size of the yttrium oxide sodium alginate gel ball adsorbent are 0.053 cm 3 / g and 31.29nm.

[0044] Example 2

[0045] A method for preparing a gel ball adsorbent for selective phosphorus removal, as described in Example 1, except that: the addition of Y in (2) is changed 2 O 3 The mass of is 0.5 g; other steps and conditions are consistent with those in Example 1.

[0046] Example 3

[0047] A method for preparing a gel ball adsorbent for selective phosphorus removal, as described in Example 1, except that: the addition of Y in (2) is changed 2 O 3 The mass of is 1.0 g; other steps and conditions are consistent with those in Example 1.

[0048] Example 4

[0049] A method for preparing a gel ball adsorbent for selective phosphorus removal, as described in Example 1, except that: the addition of Y in (2) is changed 2 O 3 The mass of is 2g; other steps and conditions are consistent with those in Example 1.

[0050] Example 5

[0051] A method for preparing a gel ball adsorbent for selective phosphorus removal, as described in Example 1, except that: the addition of Y in (2) is changed 2 O 3 The mass of is 2.4 g; other steps and conditions are consistent with those in Example 1.

[0052] Example 6

[0053] A method for preparing a gel ball adsorbent for selective phosphorus removal, as described in Example 1, except that: the addition of Y in (2) is changed 2 O 3 The mass of is 2.5 g; other steps and conditions are consistent with those in Example 1.

[0054] Example 7

[0055] A method for preparing a gel ball adsorbent for selective phosphorus removal, as described in Example 1, except that: the addition of Y in (2) is changed 2 O 3 The mass of is 3.0 g; other steps and conditions are consistent with those in Example 1.

[0056] Comparative Example 1

[0057] A method for preparing a gel ball adsorbent, as described in Example 1, except that: the addition of Y in (2) is changed 2 O 3 The mass is 0 g; other steps and conditions are consistent with those in Example 1.

[0058] Application Example 1

[0059] Phosphate adsorption: 0.5 g (dry weight of about 0.05 g) of the gel ball adsorbent prepared in Examples 1-7 and Comparative Example 1 was placed in 50 mL of an aqueous solution of potassium dihydrogen phosphate with an initial concentration of 50 mg / L, and the reaction was shaken at 25±0.5°C to ensure uniform mass transfer. After 24 hours, samples were taken at 1 cm below the liquid surface. The samples were filtered through a 0.45 μm filter membrane and the phosphorus content was determined using the molybdenum antimony anti-spectrophotometric method.

[0060] Figure 2 The adsorption data of phosphate adsorption reaction of the gel ball adsorbent prepared in Examples 1-7 of the present invention and Comparative Example 1 are as follows: Figure 2 It can be seen that Example 1 has the best adsorption capacity of 42.52 mg / g for phosphate. 2 O 3 The amount of addition is an important factor affecting its phosphorus removal effect. Under the premise of a certain amount of gel ball addition, the Y 2 O 3 The content of Y increases, and the active sites increase, which is conducive to the adsorption reaction. 2 O 3 When the addition ratio increased from 0:1 to 0.75:1, the adsorption of phosphate increased significantly, from 0.92 mg / g to 42.52 mg / g and from 1.3% to 80.0%, respectively; 2 O 3 The addition ratio continues to increase from 0.75:1 to 1.5:1. Since the effective adsorption sites are gradually saturated and no longer restrict the phosphorus removal effect, the adsorption amount gradually decreases within this range. In practical applications, it is necessary to comprehensively consider the adsorption amount and the cost of use to finally determine the optimal Y 2 O 3 :SA ratio.

[0061] Application Example 2

[0062] Effect of pH on adsorption: 0.5 g (dry weight of about 0.05 g) of the gel ball adsorbent prepared in Example 1 was placed in 50 mL of an aqueous solution of potassium dihydrogen phosphate with an initial concentration of 50 mg / L and different pH values, and the reaction was shaken at 25±0.5°C to ensure uniform mass transfer. Other test conditions were consistent with those in Application Example 1.

[0063] Figure 3The results of phosphate adsorption under different pH conditions by the gel ball adsorbent prepared in Example 1 are analyzed. It is found that the gel ball adsorbent prepared in Example 1 maintains a relatively stable adsorption performance under strong acidic conditions (pH 2) and has a relatively stable adsorption effect within the acidic range. After the reaction is completed, the end point pH of the reaction solution system is maintained between 9 and 11.

[0064] Application Example 3

[0065] Effect of coexisting ions on adsorption: 0.5 g (dry weight of about 0.05 g) of the gel ball adsorbent prepared in Example 1 was placed in 50 mL of CO 3 2- , SO 4 2- and Cl - In the potassium dihydrogen phosphate aqueous solution (where the phosphate concentration is 50 mg / L, CO 3 2- The concentration is 0.001mol / L or 0.01mol / L or 0.1mol / L, SO 4 2- The concentration is 0.001mol / L or 0.01mol / L or 0.1mol / L, Cl - The concentration is 0.001mol / L or 0.01mol / L or 0.1mol / L), and the reaction is shaken at 25±0.5℃ to ensure uniform mass transfer. Other test conditions are consistent with Application Example 1.

[0066] Figure 4 The results of the gel ball adsorbent prepared in Example 1 for the adsorption of phosphate in different anion coexistence systems are compared. Through the analysis of the experimental results, compared with the single system with only phosphate, at low concentrations of SO 4 2- In the Cl - and CO 3 2- and high concentrations of SO 4 2- The coexistence system of phosphate and phosphate showed a certain promoting effect, which can indicate that the gel spheres prepared in Example 1 have good selectivity for phosphate. (Blank refers to the adsorption effect obtained by the single phosphate system without other anions coexisting)

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An application of a gel ball adsorbent for selective phosphorus removal, which is used as an adsorbent to adsorb and remove phosphate in a phosphorus-containing liquid; the pH of the phosphorus-containing liquid is 2; the phosphate is potassium dihydrogen phosphate; CO3 is added to the phosphorus-containing liquid 2- , SO4 2- or Cl - To improve the adsorption effect of the gel ball adsorbent; in the phosphorus-containing liquid, the CO3 2- The concentration is 0.01-0.1 mol / L; in phosphorus-containing liquids, SO4 2- or Cl - The concentration is 0.01-0.1 mol / L; The adsorbent is a spherical gel particle with a particle size of 1.8-2.4 mm and a wrinkled and rough surface; The preparation method of the gel ball adsorbent for selective phosphorus removal comprises the steps of: (1) fully dispersing nano yttrium oxide (Y2O3) in water to obtain a yttrium oxide dispersion; adding sodium alginate (SA) and fully dissolving it to obtain a mixed solution; the mass ratio of nano yttrium oxide to sodium alginate is 0.75:1 to 1:1; (2) Add the mixed solution drop by drop into the CaCl2 aqueous solution to form gel balls, which are then washed to obtain a gel ball adsorbent; use a peristaltic pump to add the mixed solution drop by drop; the flow rate is 2 to 3 mL / min.

2. The use according to claim 1, characterized in that: The step (1) of the method for preparing the gel ball adsorbent includes any one of the following conditions: i. The mass concentration of yttrium oxide dispersion is 1% to 2%; ii. The dissolution of sodium alginate is carried out under stirring conditions at 40-50°C.

3. The use according to claim 1, characterized in that: Step (2) of the method for preparing the gel ball adsorbent includes any one of the following conditions: i. The mass concentration of CaCl2 aqueous solution is 0.1% to 4%; ii. The volume ratio of the mixed solution to the CaCl2 aqueous solution is 1:1-10; iii. Add the mixed solution dropwise into the CaCl2 aqueous solution and stir for 20-30 hours.

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