CN115814750B - Method for preparing porous calcium silicate adsorbent from phosphogypsum - Google Patents

Abstract

The invention discloses a method for preparing a porous calcium silicate adsorbent from phosphogypsum, and belongs to the technical field of gypsum recycling. Mainly comprises the following steps: mixing phosphogypsum, a silicon source, caustic alkali and water, uniformly stirring, and reacting under a closed condition to obtain filtrate and a solid product. And (3) drying the solid product, and then, adsorbing and enriching phosphorus in the phosphorus-containing wastewater, wherein after the adsorption is finished, the solid product can be converted into the calcium-silicon-phosphorus compound fertilizer. The filtrate is further purified, and sulfate in the filtrate can be recovered. The invention fully utilizes the resources of calcium, sulfur, phosphorus and the like in the phosphogypsum, realizes the recycling of the phosphogypsum and the phosphorus-containing wastewater, and has important significance for the high-value utilization of solid waste and wastewater.

Description

A method for preparing porous calcium silicate adsorbent from phosphogypsum

technical field

The invention belongs to the technical field of gypsum resource recycling, in particular to a method for preparing a porous calcium silicate adsorbent from phosphogypsum.

Background technique

The main component of solid waste generated in the phosphogypsum wet-process phosphoric acid process is calcium sulfate dihydrate, accounting for more than 90% of the total. my country's annual output of phosphogypsum is about 60-80 million tons, accounting for about 40% of the global total. Because phosphogypsum still contains a small amount of components such as phosphorus, fluorine, and organic matter, which seriously affect the hardening strength and setting time of phosphogypsum products, and limit the utilization of phosphogypsum. Phosphorus-containing wastewater is mostly produced in the mining and smelting of phosphate rock, domestic sewage and agricultural wastewater. The phosphorus content in these wastewater is low and the pH distribution is wide, making it difficult to effectively recycle and utilize. Adsorption method is one of the most promising and cheap extraction solutions one.

At present, most of the research is devoted to the removal of phosphorus in phosphogypsum. We have noticed that phosphorus is an essential nutrient element for crop growth. If phosphogypsum can be converted into fertilizer, it will not only eliminate the adverse effects of phosphorus in phosphogypsum, but also Turn waste into wealth and supplement the phosphorus that is urgently needed by crops.

Contents of the invention

In view of this, the present invention proposes a method for preparing a porous calcium silicate adsorbent from phosphogypsum, using phosphogypsum as a raw material to prepare a cheap adsorbent, which is used to absorb and enrich phosphorus in wastewater, and convert it into calcium-silicon-phosphorus compound fertilizer , not only can turn waste into treasure, but also simultaneously solve the two major problems of phosphogypsum solid waste and phosphorus-containing wastewater.

To achieve the above object, the present invention proposes the following technical solutions:

Technical solution 1: A porous calcium silicate adsorbent, which is obtained by reacting phosphogypsum, silicon source, caustic alkali and water as raw materials, wherein the molar ratio of calcium to silicon in the system is 0.8-3.0, sodium/potassium and The molar ratio of silicon is 1.0-2.0, and the solid-liquid ratio of phosphogypsum to water is 1g:(4-50)mL.

Further, the silicon source is sodium/potassium water glass, silicic acid or silicon-containing waste; the caustic is sodium hydroxide or potassium hydroxide.

Technical scheme two: a preparation method of porous calcium silicate adsorbent, comprising the following steps: mixing phosphogypsum, silicon source, caustic alkali and water, stirring evenly, and reacting under airtight conditions to obtain filtrate and solid product, obtained The solid product is dried to become porous calcium silicate adsorbent.

Further, the reaction temperature is from room temperature to 250° C., and the time is from 0.5 to 48 hours.

Technical scheme three: the application of a porous calcium silicate adsorbent in the treatment of phosphorus-containing wastewater.

Further, the phosphorous-containing wastewater includes wastewater, domestic sewage or agricultural wastewater generated during phosphate rock mining and smelting.

Technical solution 4: The application of a porous calcium silicate adsorbent as a fertilizer. The porous calcium silicate adsorbent is placed in phosphorus-containing wastewater to absorb phosphorus. After the adsorption is completed, a calcium-silicon-phosphorus compound fertilizer is obtained.

Technical solution five: a magnetic porous calcium silicate adsorbent, which is obtained by adding ferroferric oxide to react on the basis of phosphogypsum, silicon source, caustic alkali and water as raw materials, wherein ferric ferric oxide and phosphorus in the system The mass ratio of gypsum is (0.1-2):1. The reaction temperature is room temperature-250°C, and the time is 0.5-48h.

Technical scheme six: a preparation method of a magnetic porous calcium silicate adsorbent, comprising the following steps: mixing phosphogypsum, silicon source, caustic alkali, ferric oxide and water, stirring evenly, and reacting under airtight conditions to obtain filtrate and solid product, and the obtained solid product is dried to be magnetic porous calcium silicate adsorbent.

Technical scheme seven: the application of a magnetic porous calcium silicate adsorbent in the treatment of phosphorus-containing wastewater. The phosphorus-containing wastewater includes wastewater generated during the mining and smelting of phosphate rock, domestic sewage or agricultural wastewater.

Technical solution eight: A magnetic porous calcium silicate adsorbent is used as a fertilizer. The magnetic porous calcium silicate adsorbent is placed in phosphorus-containing wastewater to absorb phosphorus. After the adsorption is completed, a magnetic calcium-silicon-phosphorus compound fertilizer is obtained.

Technical solution 9: A method for preparing sulfate, using the filtrate prepared by the preparation method of the porous calcium silicate adsorbent and the multimagnetic porous calcium silicate adsorbent to obtain sulfate after purification.

Compared with prior art, the beneficial effect of the present invention is:

The invention is simple in operation, the phosphogypsum used can be directly used in production without washing or stockpiling pretreatment, has low requirements on equipment, and can simultaneously solve the two major pollution problems of phosphogypsum solid waste and phosphorus-containing wastewater. In addition, the sulphate in it can be recovered, further extending the economic advantages.

The invention uses phosphogypsum as a cheap calcium source, prepares a porous calcium silicate adsorbent through a metathesis reaction in one step, then absorbs and enriches phosphorus in phosphorus-containing wastewater, and finally transforms it into a calcium-silicon-phosphorus compound fertilizer. The sulfate remaining in the filtrate can be recovered by _CO removal of impurities and crystallization to obtain a higher purity sulfate product (greater than 99%). The method of the invention is simple to operate, and can realize large-scale consumption and high-value utilization of the phosphogypsum, and at the same time obtain a sulfate product with high value of by-products and wide application. By adding Fe ₃ O ₄ in the preparation process, the magnetic porous calcium silicate adsorbent can be prepared, and the magnetic calcium-silicon-phosphorus compound fertilizer can be further prepared, and the application range is wider.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the microscopic morphology figure of the porous calcium silicate adsorbent prepared in Example 1 of the present invention;

Fig. 2 is the variation diagram of the adsorption performance of the porous calcium silicate adsorbent prepared in Example 1 of the present invention to phosphate at different pHs;

Fig. 3 is the total content and effective content of calcium, silicon and phosphorus after the porous calcium silicate adsorbent prepared in Example 1 of the present invention is saturated with phosphate adsorption under the condition of pH=3;

Fig. 4 is the variation diagram of the adsorption performance of the porous calcium silicate adsorbent prepared in Examples 1-7 of the present invention to phosphate;

Fig. 5 is the variation figure of the adsorption performance of the porous calcium silicate adsorbent prepared in Examples 8-16 of the present invention to phosphate;

Fig. 6 is the microscopic morphology figure of the ferric oxide prepared by the present invention;

Fig. 7 is a diagram showing the variation of the adsorption performance of the magnetic porous calcium silicate adsorbent prepared in Examples 17-21 of the present invention for phosphate.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail. The detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features and embodiments of the present invention.

It should be understood that the terminology described in the present invention is only used to describe specific embodiments, and is not used to limit the present invention. In addition, regarding the numerical ranges in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents are described. In case of conflict with any incorporated document, the contents of this specification control.

It will be apparent to those skilled in the art that various modifications and changes can be made in the specific embodiments of the present invention described herein without departing from the scope or spirit of the present invention. Other embodiments will be apparent to the skilled person from the description of the present invention. The specification and examples in this application are exemplary only.

As used herein, "comprising", "comprising", "having", "comprising" and so on are all open terms, meaning including but not limited to.

"Room temperature" in the present invention refers to 25°C unless otherwise specified.

The porous calcium silicate prepared by the present invention is a green adsorbent that is simple to prepare, high in adsorption capacity, non-toxic, harmless and easy to recycle. In the present invention, phosphogypsum is used as a cheap calcium source and prepared by a simple metathesis method to obtain low-cost, Porous calcium silicate adsorbent with strong adsorption performance is used to absorb and enrich phosphorus in phosphorus-containing wastewater. After the adsorption is completed, the adsorbent is transformed into calcium-silicon-phosphorus compound fertilizer, which can be used for crop production. It can not only eliminate the environmental damage caused by phosphogypsum and phosphorus-containing wastewater, but also realize the large-scale consumption and high-value utilization of phosphogypsum.

Adding Fe ₃ O ₄ during the preparation of the adsorbent can prepare the phosphogypsum-based Fe ₃ O ₄ /porous calcium silicate composite adsorbent, which is easier to recover the adsorbent during the adsorption process and has more application scenarios. After the adsorption is completed, it can be Converting it into magnetic calcium-silicon-phosphorus compound fertilizer is more conducive to increasing the yield of crops.

The specific technical scheme is as follows:

Technical solution 1: a porous calcium silicate adsorbent, which is obtained by reacting phosphogypsum, silicon source, caustic alkali and water as raw materials, wherein the molar ratio of calcium to silicon in the system is 0.8-2.0, more preferably, 0.8, 1.0, 1.1, 1.2, 1.5, 2.0; the molar ratio of sodium/potassium to silicon is 1.0-2.0, more preferably, 1.0, 1.2; the solid-liquid ratio of phosphogypsum to water is 1g:(4-50)mL , more preferably, 1g:20mL, 1g:15mL.

In some preferred embodiments, the silicon source is sodium/potassium water glass, silicic acid or silicon-containing waste, more preferably, sodium water glass, silicic acid; the caustic alkali is sodium hydroxide or potassium hydroxide, more preferably Preferably, sodium hydroxide.

Technical scheme two: a preparation method of porous calcium silicate adsorbent, comprising the following steps: mixing phosphogypsum, silicon source, caustic alkali and water, stirring evenly, and reacting under airtight conditions to obtain filtrate and solid product, obtained The solid product is dried to become porous calcium silicate adsorbent.

In some preferred embodiments, the reaction temperature is from room temperature to 250°C, more preferably, 40°C, 60°C, 80°C, 90°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C ; The reaction time is 0.5-48h, more preferably, 5h, 6h.

Technical scheme three: the application of a porous calcium silicate adsorbent in the treatment of phosphorus-containing wastewater.

In some preferred embodiments, the phosphorus-containing wastewater includes wastewater generated during phosphate rock mining and smelting, domestic sewage or agricultural wastewater.

Technical solution 4: The application of a porous calcium silicate adsorbent as a fertilizer. The porous calcium silicate adsorbent is placed in phosphorus-containing wastewater to absorb phosphorus. After the adsorption is completed, a calcium-silicon-phosphorus compound fertilizer is obtained.

Technical solution five: a magnetic porous calcium silicate adsorbent, which is obtained by adding ferroferric oxide to react on the basis of phosphogypsum, silicon source, caustic alkali and water as raw materials, wherein ferric ferric oxide and phosphorus in the system The mass ratio of gypsum is (0.1-2):1, more preferably 0.1:1, 0.2:1, 0.5:1, 1:1, 2:1.

Technical scheme six: a preparation method of a magnetic porous calcium silicate adsorbent, comprising the following steps: mixing phosphogypsum, silicon source, caustic alkali, ferric oxide and water, stirring evenly, and reacting under airtight conditions to obtain filtrate and solid product, and the obtained solid product is dried to be magnetic porous calcium silicate adsorbent. The reaction temperature is room temperature-250°C, more preferably 60°C, and the reaction time is 0.5-48h, more preferably 6h.

Technical scheme seven: the application of a magnetic porous calcium silicate adsorbent in the treatment of phosphorus-containing wastewater. The phosphorus-containing wastewater includes wastewater generated during the mining and smelting of phosphate rock, domestic sewage or agricultural wastewater.

Technical solution eight: A magnetic porous calcium silicate adsorbent is used as a fertilizer. The magnetic porous calcium silicate adsorbent is placed in phosphorus-containing wastewater to absorb phosphorus. After the adsorption is completed, a magnetic calcium-silicon-phosphorus compound fertilizer is obtained.

Technical solution 9: A method for preparing sulfate, using the filtrate prepared by the preparation method of the porous calcium silicate adsorbent and the porous magnetic calcium silicate adsorbent to obtain sulfate after purification. A small amount of silicon and calcium remain in the filtrate, and carbon dioxide needs to be introduced to precipitate calcium and silicon in the form of calcium carbonate and silicon dioxide respectively to obtain purified sulfate.

The following examples are used as a further description of the technical solutions of the present invention.

Example 1

The phosphogypsum used in this example was taken from a phosphogypsum storage yard in Henan. It was stored for about one year and dried at 80°C to constant weight before use. The chemical composition was analyzed by XRF. The results are shown in Table 1.

The main chemical composition (wt.%) in the phosphogypsum of table 1

SO ₃ CaO SiO ₂ P ₂ O ₅ Al ₂ O ₃ MgO _{Fe2O3 _} K ₂ O other 50.80 38.41 6.15 1.93 0.83 0.73 0.54 0.31 0.30

1. A preparation method of porous calcium silicate adsorbent:

1) Weigh 10 grams of phosphogypsum raw material, add a certain mass of sodium water glass and sodium hydroxide, so that the molar ratio of Ca and Si is 1.0, and the molar ratio of Na and Si is 1.2.

2) Add 200 mL of distilled water, and continue to stir for 2 hours with a magnetic stirrer, so that the raw materials are evenly mixed. Then the well-mixed raw materials were transferred to a closed reaction kettle, and the reaction was continued at 90° C. for 6 hours. After the temperature dropped to room temperature, they were taken out and filtered. The filtrate and solid product are collected, and the solid product is dried to obtain a porous calcium silicate adsorbent.

2. A method for preparing calcium-silicon-phosphorus compound fertilizer from phosphogypsum:

The porous calcium silicate adsorbent prepared above is used to treat phosphorus-containing wastewater produced in the phosphate rock smelting process, and the phosphorus content is about 150 mg/L. The pH value of phosphorus-containing wastewater was adjusted to 2-11 with 0.1mol/L hydrochloric acid and sodium hydroxide, and the effect of initial concentration on phosphorus adsorption capacity was studied. After the adsorption is completed, filter and dry to obtain an adsorbent that can be used as a calcium-silicon-phosphorus compound fertilizer. Analyze the content of available phosphorus, silicon and calcium.

3. A preparation method of vitriol:

After collecting the filtrate produced by the preparation method of the porous calcium silicate adsorbent, _CO2 is introduced to remove impurities, so that the residual silicon and calcium in the filtrate are converted into silicon dioxide and calcium carbonate respectively, and the impurities are removed by filtration. The filtrate after impurity removal was evaporated and crystallized, and the sodium sulfate product was recovered. The components were analyzed by XRF, and the results were shown in Table 2. The content of sodium sulfate in the product reached 99.48%.

The chemical analysis (wt.%) of table 2 sodium sulfate product

SO ₃ Na ₂ O SiO ₂ K ₂ O CaO Cl other 52.57 46.91 0.24 0.17 0.06 0.03 0.02

The determination method is as follows:

The amount of porous calcium silicate adsorbent added was 1.0g/L. Through batch adsorption experiments, the porous calcium silicate adsorbent prepared from phosphogypsum was evaluated for its ability to absorb and enrich phosphorus in phosphorus ore smelting wastewater. After treating phosphorus-containing wastewater, the porous calcium silicate adsorbent The microscopic morphology of calcium silicate adsorbent is shown in Fig. 1. It can be seen from Figure 1 that phosphorus is mainly enriched on the surface of the porous calcium silicate adsorbent, this is because the adsorbent spontaneously releases Ca ²⁺ and OH ^- in phosphorus-containing wastewater, and the released Ca ²⁺ and phosphoric acid in the solution Roots bind and attach to the surface of the adsorbent.

In step 3), under different initial pH conditions, the adsorption capacity of the porous calcium silicate adsorbent for phosphorus is shown in Figure 2. As can be seen from Figure 2, the porous calcium silicate adsorbent prepared by phosphogypsum has a strong adsorption capacity for phosphorus in a wide pH range (3-11), and the adsorption capacity is the best when the pH is 3. This is due to the fact that acidic conditions make more use of the adsorbent to release Ca ²⁺ and OH ^- , but when the aqueous solution is more acidic (pH<3), it exceeds the tolerance of porous calcium silicate, a large amount of calcium ions are leached, and the porous structure is affected. Destruction, the adsorption effect on phosphorus is poor. Under the condition that the initial pH is 3, the total content and effective content of calcium, silicon and phosphorus after the adsorbent is saturated are analyzed.

Under the condition of initial pH 3, the total content and effective content of calcium, silicon and phosphorus in the adsorbent after adsorption saturation are shown in Figure 3. As can be seen from Figure 3, the adsorbent after adsorption saturation contains higher available calcium and available silicon (both greater than 30%), and the available phosphorus content is > 20% (calculated as P ₂ O ₅ ), which is an excellent calcium silicon phosphorus compound fertilizer.

Example 2

The preparation method of the porous calcium silicate adsorbent is the same as in Example 1, the difference being that the Ca and Si molar ratios in the raw materials of step 1) are 0.8.

Example 3

The preparation method of the porous calcium silicate adsorbent is the same as in Example 1, the difference is that the molar ratio of Ca and Si in the raw material of step 1) is 0.9.

Example 4

The preparation method of the porous calcium silicate adsorbent is the same as in Example 1, the difference is that the Ca and Si molar ratios in the raw materials of step 1) are 1.1.

Example 5

The preparation method of the porous calcium silicate adsorbent is the same as in Example 1, the difference being that the Ca and Si molar ratios in the raw materials of step 1) are 1.2.

Example 6

The preparation method of the porous calcium silicate adsorbent is the same as in Example 1, the difference being that the Ca and Si molar ratios in the raw materials of step 1) are 1.5.

Example 7

The preparation method of the porous calcium silicate adsorbent is the same as that in Example 1, the difference being that the molar ratio of Ca and Si in the raw material of step 1) is 2.0.

The determination method is as follows:

The porous calcium silicate prepared in Examples 1-7 was used as an adsorbent for treating phosphorus-containing wastewater. Phosphorus-containing wastewater was prepared in the laboratory. The water used was the surface water of Huaxi River in Guiyang City. The concentration of PO ₄ ^3- -P was prepared by adding potassium dihydrogen sulfate to 100mg/L, and adjusted with 0.1M hydrochloric acid and NaOH. The initial pH of phosphorus-containing wastewater is 6. During the adsorption process, the amount of adsorbent added was 1.0 g/L, the temperature was 25°C, and the adsorption time was set at 24 h. The adsorption effect is shown in Figure 4.

As can be seen from Figure 4, within a wide range of calcium-silicon molar ratios, the synthetic porous calcium silicate has a strong adsorption capacity for phosphorus (removal is greater than 90%), and the calcium-silicon molar ratio is within the range of 0.8-1.2 , as the calcium-silicon molar ratio increases, the adsorption capacity for phosphorus is stronger. When the calcium-silicon molar ratio is greater than 1.2, the adsorption capacity for phosphorus begins to weaken with the increase of the molar ratio. This is due to the large molar ratio At this time, the calcium sulfate in phosphogypsum cannot be completely converted into porous calcium silicate, thereby reducing the adsorption capacity of phosphorus. This will affect the content of available phosphorus in the product after adsorption.

Example 8

The phosphogypsum used in this example was taken from the fresh phosphogypsum in Jiaoyishan Phosphogypsum Depository, Guizhou. Before use, it was dried at 105°C to constant weight, and its chemical composition was analyzed by XRF. The results are shown in Table 3. Compared with phosphogypsum that has been stacked for a long time (as shown in Table 1), fresh phosphogypsum contains higher P ₂ O ₅ , which is more conducive to conversion into calcium-silicon-phosphorus compound fertilizer.

The main chemical composition (wt.%) in the phosphogypsum of table 3

SO ₃ CaO SiO ₂ P ₂ O ₅ Al ₂ O ₃ Na ₂ O _{Fe2O3 _} K ₂ O 51.66 39.64 2.25 5.11 0.40 0.16 0.63 0.15

A kind of preparation method of porous calcium silicate adsorbent:

1) Weigh 20 grams of phosphogypsum raw material, add a certain mass of silicic acid and sodium hydroxide, so that the molar ratio of Ca and Si is 1.2, and the molar ratio of Na and Si is 1.0.

2) Add 300mL of distilled water and continue to stir with a magnetic stirrer for 1h, so that the raw materials are mixed evenly. Then the well-mixed raw materials were transferred to a closed reaction kettle, and the reaction was continued at 100° C. for 5 hours. After the temperature dropped to room temperature, they were taken out and filtered. The filtrate and solid product are collected, and the solid product is dried to obtain a porous calcium silicate adsorbent.

Example 9

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 40°C.

Example 10

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 60°C.

Example 11

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 80°C.

Example 12

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 120°C.

Example 13

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 140°C.

Example 14

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 160°C.

Example 15

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 180°C.

Example 16

The preparation method of the porous calcium silicate adsorbent is the same as in Example 8, except that the reaction temperature in step 2) is 200°C.

The determination method is as follows:

The porous calcium silicate prepared in Examples 8-16 was used as an adsorbent for treating phosphorus-containing wastewater. Phosphorus-containing wastewater was prepared in the laboratory. The water used was the surface water of Huaxi River in Guiyang City. The concentration of PO ₄ ^3- -P was adjusted to 200mg/L by adding potassium dihydrogen sulfate, and adjusted with 0.1M hydrochloric acid and NaOH. The initial pH of phosphorus-containing wastewater was 8. During the adsorption process, the amount of adsorbent added was 1.5g/L, the temperature was 30°C, and the adsorption time was set at 24h. The adsorption effect is shown in Figure 5.

It can be seen from Figure 5 that the adsorption capacity of the adsorbent synthesized from phosphogypsum decreases gradually with the increase of synthesis temperature, which is because the crystallinity of the adsorbent gradually increases with the increase of synthesis temperature, and the The release capacity of calcium ions and hydroxide ions gradually weakened, which reduced the adsorption performance of the adsorbent. But the overall adsorption capacity is still very considerable, all higher than 100mg/g.

Example 17

As a new type of fertilizer, magnetic fertilizer is a combination of "fertilizer" and "magnetism". It is formulated from fertilizers (such as nitrogen, phosphorus, potassium, etc.) and magnetized magnetic carriers (such as fly ash, pyrite slag and yellow phosphorus slag, etc.). Magnetic fertilizer can adjust the biological magnetic environment, thereby stimulating the growth of crops, activating the nutrients in the soil and fertilizers, improving the absorption of nutrients by crops, increasing the air permeability of the soil, so as to achieve the purpose of increasing plant production.

The phosphogypsum used in this example is the same as that used in Embodiment 1, and its composition is shown in Table 1.

A preparation method of magnetic porous calcium silicate adsorbent:

1) Weigh 10 grams of phosphogypsum raw material, add a certain quality of sodium silicate, sodium hydroxide and ferric oxide suspension, so that the molar ratio of Ca and Si is 1.0, the molar ratio of Na and Si is 1.0, and the molar ratio of triferrous oxide is 1.0. The mass ratio of iron to phosphogypsum is 0.5:1.

Ferroferric oxide is prepared by coprecipitation method in the laboratory. The specific method is: weigh 0.2mol anhydrous ferric sulfate and 0.2mol ferrous sulfate heptahydrate, and dissolve them in 1.5L anaerobic water (boiling in advance for 5 Minutes, then sealed and cooled to room temperature), the solution was mechanically stirred. Prepare 3mol/L sodium hydroxide solution, add sodium hydroxide solution drop by drop to adjust the pH value of the solution to 9.5, keep stirring during the dropping process, and pass nitrogen protection to prevent oxidation. The process lasts for about 1 hour. The reacted ferroferric oxide is attracted and aggregated with a magnet, concentrated, washed with anaerobic water several times, and finally 250 mL of high-concentration ferric ferric oxide suspension is obtained.

The microscopic topography is shown in Figure 6. It can be seen from Fig. 6 that the obtained particles of ferric oxide are uniform in size and are all nanoparticles.

2) Add 200 mL of distilled water, and continue to stir for 2 hours with a magnetic stirrer, so that the raw materials are evenly mixed. Then the well-mixed raw materials were transferred to a closed reaction kettle, and the reaction was continued at 60° C. for 6 hours. After the temperature dropped to room temperature, they were taken out and filtered. The filtrate and solid product are collected, and the solid product is dried to obtain a magnetic porous calcium silicate adsorbent.

Example 18

The preparation method of the magnetic porous calcium silicate adsorbent is the same as in Example 17, the difference is that the mass ratio of ferric oxide to phosphogypsum in the raw material in step 1) is 0.1:1.

Example 19

The preparation method of the magnetic porous calcium silicate adsorbent is the same as in Example 17, the difference is that the mass ratio of ferric oxide to phosphogypsum in the raw material in step 1) is 0.2:1.

Example 20

The preparation method of the magnetic porous calcium silicate adsorbent is the same as that in Example 17, except that the mass ratio of ferric oxide and phosphogypsum in the raw materials in step 1) is 1:1.

Example 21

The preparation method of the magnetic porous calcium silicate adsorbent is the same as in Example 17, the difference is that the mass ratio of ferric oxide and phosphogypsum in the raw materials in step 1) is 2:1.

The determination method is as follows:

The porous calcium silicate prepared in Examples 17-21 was used as an adsorbent to treat phosphorus-containing wastewater. Phosphorus-containing wastewater was prepared in the laboratory. The water used was the surface water of Huaxi River in Guiyang City. The concentration of PO ₄ ^3- -P was prepared by adding potassium dihydrogen sulfate to 100mg/L, and adjusted with 0.1M hydrochloric acid and NaOH. The initial pH of phosphorus-containing wastewater is 8 (close to the pH value of natural water). During the adsorption process, the amount of adsorbent added was 1.0 g/L, the temperature was 25°C, and the adsorption time was set at 24 h. The adsorption effect is shown in Figure 7.

It can be seen from Figure 7 that with the gradual increase in the amount of ferroferric oxide added, the adsorption capacity of the prepared adsorbent gradually decreases. gradually decreases.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention within.

Claims (3)

1. The application of the porous calcium silicate adsorbent in treating the phosphorus-containing wastewater is characterized in that the concentration of the phosphorus-containing wastewater is 100mg/L, and 0.1M hydrochloric acid and NaOH are used for adjusting the initial pH value of the phosphorus-containing wastewater to 6; the addition amount of the adsorbent is 1.0g/L, the temperature is 25 ℃, and the adsorption time is 24 hours;

the porous calcium silicate adsorbent is prepared by taking phosphogypsum, a silicon source, caustic alkali and water as raw materials to react, wherein the molar ratio of calcium to silicon in a system is 1.0, the molar ratio of sodium/potassium to silicon is 1.2, and the solid-liquid ratio of phosphogypsum to water is 1g (4-50) mL;

the preparation method of the porous calcium silicate adsorbent comprises the following steps: mixing phosphogypsum, a silicon source, caustic alkali and water, uniformly stirring, reacting under a closed condition to obtain filtrate and a solid product, and drying the obtained solid product to obtain the porous calcium silicate adsorbent; the reaction temperature is 90 ℃ and the reaction time is 6h.

2. The use according to claim 1, wherein the silicon source is sodium/potassium water glass, silicic acid or silicon-containing waste; the caustic alkali is sodium hydroxide or potassium hydroxide.

3. The application of the magnetic porous calcium silicate adsorbent in the treatment of the phosphorus-containing wastewater is characterized in that the concentration of the phosphorus-containing wastewater is 100mg/L, and 0.1M hydrochloric acid and NaOH are used for adjusting the initial pH value of the phosphorus-containing wastewater to 8; the addition amount of the adsorbent is 1.0g/L, the temperature is 25 ℃, and the adsorption time is 24 hours;

the preparation method of the magnetic porous calcium silicate adsorbent comprises the following steps:

1) 10 g of phosphogypsum raw material is weighed, and sodium silicate, sodium hydroxide and ferroferric oxide suspension with certain mass are added so that the molar ratio of Ca to Si is 1.0, the molar ratio of Na to Si is 1.0, and the mass ratio of ferroferric oxide to phosphogypsum is 0.5:1;

2) Adding 200mL of distilled water, continuously stirring for 2 hours by using a magnetic stirrer to uniformly mix raw materials, transferring the uniformly mixed raw materials into a closed reaction kettle, continuously reacting for 6 hours at 60 ℃, taking out and filtering after the temperature is reduced to room temperature, collecting filtrate and solid products, and drying the solid products to obtain the magnetic porous calcium silicate adsorbent.

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