阅读说明：本技术 一种利用释镁-碱功能矿物材料回收废液中氮磷的方法 (Method for recovering nitrogen and phosphorus in waste liquid by using magnesium-alkali releasing functional mineral material ) 是由 赵旭 李学伟 乔梦 于 2021-02-04 设计创作，主要内容包括：本发明提出一种利用释镁-碱功能矿物材料回收废液中氮磷的方法,属于环境技术领域。所述方法,包括如下步骤：1)对含镁离子和氢氧根离子的矿物原料进行机械活化,得释镁-碱功能矿物材料；2)将上述释镁-碱功能矿物材料加入待处理废液中,采用沉淀结晶法,回收废液中的氮磷。本发明主要用于回收废液中氮磷,一步反应即可形成鸟粪石沉淀,实现氮磷的有效回收。该方法工艺简单,经济价值高,且氮磷回收率高。(The invention provides a method for recovering nitrogen and phosphorus in waste liquid by using a magnesium-alkali releasing functional mineral material, belonging to the technical field of environment. The method comprises the following steps: 1) mechanically activating mineral raw materials containing magnesium ions and hydroxyl ions to obtain a magnesium-alkali releasing functional mineral material; 2) adding the magnesium-alkali release functional mineral material into the waste liquid to be treated, and recovering nitrogen and phosphorus in the waste liquid by adopting a precipitation crystallization method. The invention is mainly used for recovering nitrogen and phosphorus in the waste liquid, and struvite sediment can be formed by one-step reaction, thereby realizing the effective recovery of nitrogen and phosphorus. The method has the advantages of simple process, high economic value and high nitrogen and phosphorus recovery rate.)

1. A method for recovering nitrogen and phosphorus in waste liquid by using a magnesium-alkali releasing functional mineral material is characterized by comprising the following steps:

1) mechanically activating mineral raw materials containing magnesium ions and hydroxyl ions to obtain a magnesium-alkali releasing functional mineral material;

2) adding the magnesium-alkali release functional mineral material into the waste liquid to be treated, and recovering nitrogen and phosphorus in the waste liquid by adopting a precipitation crystallization method.

2. The method of claim 1,

step 1) specifically, putting the mineral raw materials into a reaction tank, and performing ball milling activation by using grinding balls as grinding media to obtain the magnesium-alkali functional mineral material.

3. The method according to claim 1 or 2,

in the step 1), the mineral raw material containing magnesium ions and hydroxide ions is a natural mineral raw material; preferably, the mineral feedstock comprises pure serpentine.

4. The method according to claim 1 or 2,

in the step 1), the activation time is 10-150 min; preferably, the activation time is 60-120 min.

5. The method of claim 2,

in the step 1), the rotation speed of the ball mill is 100-800 rpm; preferably, the rotation speed of the ball mill is 500-600 rpm.

6. The method of claim 1,

in the step 2), when nitrogen and phosphorus in the waste liquid are recovered, the hydraulic retention time is 1-90 min; preferably, the hydraulic retention time is 40-60 min.

7. The method of claim 1,

in the step 2), the adding amount of the magnesium-alkali releasing functional mineral material to the waste liquid to be treated is 0.1-2.0 g/L; wherein the concentration of phosphorus in the waste liquid to be treated is 1mmol/L, and the molar ratio of nitrogen to phosphorus is more than 1.

8. The method of claim 1,

in the step 2), the pH value of the waste liquid to be treated is 1-10; preferably, the pH value of the waste liquid to be treated is 7-9.

Technical Field

The invention belongs to the technical field of environment, and particularly relates to a method for recovering nitrogen and phosphorus in waste liquid by using a magnesium-alkali releasing functional mineral material.

Background

Aiming at high-nitrogen and phosphorus waste liquid, the research of efficiently recovering and removing nitrogen and phosphorus in the waste liquid is carried out by taking source reduction and resource as targets, on one hand, the source emission reduction of typical pollutants in domestic sewage can be realized, the load on a subsequent biochemical treatment system is reduced, on the other hand, the recovered nitrogen and phosphorus compounds can be used as a slow-release fertilizer, the recovery and reutilization of phosphorus in the sewage can be realized, and the method has important significance.

Struvite (MgNH)₄PO₄·6H₂O, MAP) precipitation crystallization method to recover nitrogen and phosphorus in the waste liquid is one of the most promising phosphorus recovery ways. At present, the process for recovering phosphorus by adopting the MAP method internationally is applied in the engineering of countries such as the United states, the Netherlands, the British, the Japan, the Australia and the like. The first set of granular Crytalactor reactors is established in 2008 by adopting the fluidized bed crystallization process of the Crytalactor of the Holland DHV company in China at first, phosphorus and nitrogen containing waste liquid is treated, and the recovered high-purity struvite granular pellets can be used for agriculture.

In recent years, China has done much work on the aspect of phosphorus recovery by MAP precipitation crystallization, and the work mainly comprises the recovery of phosphorus in anaerobic digestion waste liquid of pig farms, urine, garbage percolate and sludge, the treatment of ammonia nitrogen waste liquid and the like. These studies have primarily investigated the operating parameters and reaction conditions for struvite crystallization, such as pH, supersaturation, Mg/N/P molar ratio, etc. But still has the problems of too high recovery cost, for example, the recovery cost (about $ 3500/ton P) is far higher than the economic value of struvite (about $ 765/ton P), and the large-area popularization and application of the struvite are restricted.

In a typical MAP precipitation crystallization process, the pH of the solution needs to be controlled within the range of 9.0-10.0, and when the actual waste liquid is treated, the MAP precipitates are generated and H is released at the same time⁺And the pH of the solution is reduced, so in practical operation, an alkaline agent (such as NaOH) is continuously added into the solution to maintain the optimal pH range for the struvite generation, and therefore, the alkali consumption cost in the process of recovering phosphorus by using the MAP precipitation crystallization method accounts for 97 percent of the total chemical cost. In addition, due to Mg in the waste liquid²⁺The concentration is usually very low or even 0, so that a large amount of magnesium salt, such as MgSO₄、MgCl₂MgO, etc., so that magnesium salts account for approximately 75% of the total production cost. The alkaline environment and magnesium ions are the crucial factors for struvite crystallization and precipitation, but the alkali consumption cost and the magnesium source cost greatly increase the MAP production cost.

At present, researchers have used electrochemical action to produce alkali and CO₂The blow-off device increases the pH value, and utilizes seawater, MgO-containing by-products, brine and the like as cheap magnesium sources and the like to reduce the problems of alkali consumption cost, high magnesium source cost and the like in the struvite production process, and the like, although a certain effect is obtained, the problems still existLimited application area, difficult industrialization and the like.

Disclosure of Invention

The invention provides a method for recovering nitrogen and phosphorus in waste liquid by using a magnesium-alkali releasing functional mineral material. Based on guanite technical current situation, combine zymotic fluid filtrating nitrogen phosphorus pollutant characteristic, researched and developed and possessed the novel functional mineral material who provides magnesium and alkali simultaneously, directly add the nitrogen and phosphorus waste liquid and can realize the guanite crystallization to retrieve phosphorus and nitrogen, unnecessary alkali can make partial ammonia nitrogen retrieve with the form of ammonia simultaneously, finally reach nitrogen and phosphorus low cost, green, efficient recovery and get rid of in the filtrating.

The invention provides a method for recovering nitrogen and phosphorus in waste liquid by using a magnesium-alkali releasing functional mineral material, which comprises the following steps:

1) mechanically activating mineral raw materials containing magnesium ions and hydroxyl ions to obtain a magnesium-alkali releasing functional mineral material;

2) adding the magnesium-alkali release functional mineral material into the waste liquid to be treated, and recovering nitrogen and phosphorus in the waste liquid by adopting a precipitation crystallization method.

Further, the step 1) is specifically that the mineral raw materials are put into a reaction tank, and grinding balls are used as grinding media to perform ball milling activation, so that the magnesium-alkali release functional mineral material is obtained.

Further, in the step 1), the mineral raw material containing magnesium ions and hydroxide ions is a natural mineral raw material; preferably, the mineral feedstock comprises pure serpentine.

Further, in the step 1), the activation time is 10-150 min; preferably, the activation time is 60-120 min.

Further, in the step 1), the rotation speed of the ball milling is 100-800 rpm; preferably, the rotation speed of the ball mill is 500-600 rpm.

Further, in the step 2), when nitrogen and phosphorus in the waste liquid are recovered, the hydraulic retention time is 1-90 min; preferably, the hydraulic retention time is 40-60 min.

Further, in the step 2), the adding amount of the magnesium-alkali releasing functional mineral material to the waste liquid to be treated is 0.1-2.0 g/L; wherein the concentration of phosphorus in the waste liquid to be treated is 1mmol/L, and the molar ratio of nitrogen to phosphorus is more than 1.

Further, in the step 2), the pH value of the waste liquid to be treated is 1-10; preferably, the pH value of the waste liquid to be treated is 7-9.

The invention has the following advantages:

the invention provides a method for recovering nitrogen and phosphorus from waste liquid by using a magnesium-alkali releasing functional mineral material. The method has the advantages of simple process, high economic value and high nitrogen and phosphorus recovery rate.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a surface topography of a functional mineral material (a) and a recovered product (b) in test example 1 of the present invention;

FIG. 2 shows the phase (a) and the particle size characteristics (b) of the precipitated product produced after treatment of the filtrate in test example 1 according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

The inventor finds that magnesium-containing minerals such as serpentine and magnesite exist in large quantities in nature. Wherein, the serpentine mineral contains magnesium and hydroxyl, and can be used as a magnesium source and an alkali source at the same time. However, the natural mineral materials have stable chemical properties, cannot generate obvious dissolution behavior in neutral water environment, have low chemical reaction activity and are difficult to generate chemical reaction with ions in a solution.

An embodiment of the invention provides a method for recovering nitrogen and phosphorus in waste liquid by using a magnesium-alkali releasing functional mineral material, which comprises the following steps:

1) mechanically activating mineral raw materials containing magnesium ions and hydroxyl ions to obtain a magnesium-alkali releasing functional mineral material;

2) adding the magnesium-alkali release functional mineral material into the waste liquid to be treated, and recovering nitrogen and phosphorus in the waste liquid by adopting a precipitation crystallization method.

The method for recovering nitrogen and phosphorus from waste liquid by using the magnesium-alkali releasing functional mineral material provided by the embodiment of the invention comprises the steps of firstly activating the mineral material containing magnesium ions and hydroxyl ions, then adding the activated material into the waste liquid containing nitrogen and phosphorus, and reacting to form struvite precipitate, thereby realizing the recovery of nitrogen and phosphorus in one step. The method does not need to add a magnesium source and hydroxyl independently, greatly reduces the process cost, and has simple process, high nitrogen and phosphorus recovery rate and higher application value.

Specifically, in the activation stage, mineral raw materials containing magnesium ions and hydroxyl ions, such as serpentine, are mechanically activated, such as by using grinding balls for extrusion, impact and shearing force crushing, so that the size of the mineral raw materials is reduced initially, and as the activation continues, the crystal forms of the mineral particles are destroyed, so that the reaction activity of the mineral particles is obviously improved. During the milling process, a large amount of active Mg is generated²⁺And OH^-Causing them to be rapidly released from the mineral particles into an aqueous solution (equation I).

With Mg²⁺And OH^-To produce negatively charged amorphous silica particles (HSiO) in solution₃ ^-·SiO₂). PO in waste liquid₄ ^3-And NH₄ ⁺In the presence of (2) Mg²⁺And NH₄ ⁺Firstly, the silicon dioxide is gathered on the surface of the silicon dioxide particles through electrostatic adsorption and then is mixed with PO₄ ^3-Integral collision to form struvite MgNH₄PO₄·6H₂O (reaction formula II). In addition, the produced silica particles may also act as seed crystals to promote the crystallization of struvite. During struvite crystallization, a portion of the NH is present₄ ⁺And excess OH^-Generating escaped ammonia gas (NH)₃) (reaction formula III).

Thus, the activated mineral particles are continuously dissolved in the solution, stably providing Mg²⁺And OH^-So as to form struvite and ammonia, thereby achieving the high-efficiency recovery and removal of nitrogen and phosphorus.

Mg₃Si₂O₅(OH)₄+H₂O→3Mg²⁺+5OH^-+HSiO₃ ^-·SiO₂I Mg²⁺+NH₄ ⁺+H_nPO₄ ^3-n+6H₂O→MgNH₄PO₄·6H₂O↓+nH⁺II

NH₄ ⁺+OH^-→NH₃(aq)+H₂O III

In step 1) of the embodiment of the invention, the magnesium-alkali releasing functional mineral material is prepared by adopting a method of mechanically activating a mineral raw material.

Specifically, in the step 1), the mineral raw material containing magnesium ions and hydroxide ions is a natural mineral raw material. For example, it may comprise pure serpentine and mineral with a small amount of gangue (gangue content)<20%) natural serpentine raw ore, the effective chemical component of the raw mineral material is Mg₆[(OH)₄Si₂O₅]₂. That is, the mineral feedstock may include a minor amount of other gangue mineral components such as brucite, but the major portion is still Mg₆[(OH)₄Si₂O₅]₂. Preferably, the mineral feedstock comprises pure serpentine.

Specifically, in the step 1), the activation time is 10-150 min; the activation time is 60-120 min. Specifically, the time period can be 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, etc. The difference of the activation time directly influences the mechanical acting force intensity of the mineral raw materials, and further influences the activation effect and the effect on nitrogen and phosphorus in the waste liquid.

In one embodiment of the invention, the rotation speed of the ball mill is 100-800 rpm; preferably, the rotation speed of the ball milling is 500-600 rpm; specifically, the rotation speed of the ball mill may be 300rpm, 400rpm, 450rpm, 500rpm, 600rpm, or the like. More preferably, the rotation speed is 500 rpm. The activation strength is positively correlated with the ball milling rotation speed, the activation time is fixed, the higher the rotation speed is, the stronger the activation strength is, the high activation strength promotes the efficiency of mineral raw material matter structure recombination, the functional material with more excellent magnesium-alkali releasing function can be prepared, and then the direct influence is generated on the subsequent nitrogen and phosphorus recovery and removal effect.

In an embodiment of the invention, in the step 1), the diameter of the grinding ball is 1 mm-20 mm; preferably, the grinding balls with the same diameter or the grinding balls with different diameters are used for mixing; for example, grinding balls with diameters of 14mm, 7mm and 3mm can be mixed according to the weight ratio of 1-5: 1: 1.

In one embodiment of the invention, in the step 1), the ratio of balls to materials is 20-100: 1; preferably, the ball-to-feed ratio is optimally 60: 1.

In an embodiment of the present invention, in step 1), the material of the reaction tank may be zirconium, corundum, stainless steel, or agate. The grinding balls are zirconium balls, corundum balls, stainless steel balls or agate balls and the like.

In the step 2) of the embodiment of the invention, the magnesium-alkali release functional mineral material is added into the waste liquid containing nitrogen and phosphorus, and a precipitation crystallization method is adopted to realize the recovery of the nitrogen and phosphorus in the waste liquid.

In one embodiment of the invention, in the step 2), when nitrogen and phosphorus in the waste liquid are recovered, the hydraulic retention time HRT is 1-90 min; specifically, the hydraulic retention time HRT may be 10min, 20min, 30min, 40min, 50min, 60min, etc.; preferably, the hydraulic retention time HRT is 40-60 min. Hydraulic retention time can affect Mg in solution²⁺、PO₄ ^3-And NH₄ ⁺The interaction time between the ions, in turn, affects the progress of the struvite crystallization reaction. Under the appropriate conditions of the reaction environment, sufficient reaction time guarantees the formation of struvite crystals, and the recovery effect of nitrogen and phosphorus in the waste liquid is directly influenced.

In one embodiment of the invention, the adding amount of the magnesium-alkali releasing functional mineral material to the waste liquid to be treated is 0.1-2.0 g/L; preferably, the adding amount of the magnesium-alkali releasing functional mineral material to the waste liquid to be treated is 0.5-1.0 g/L respectively; wherein the concentration of phosphorus in the waste liquid to be treated is 1mmol/L, and the molar ratio of nitrogen to phosphorus is more than 1. The dosage of the magnesium-alkali release functional mineral material can influence the dosage of magnesium ions and hydroxyl ions, and for nitrogen and phosphorus in the waste liquid, at least equimolar magnesium ions are needed to achieve effective nitrogen and phosphorus recovery, so that the dosage of the magnesium-alkali release functional mineral material directly influences the recovery effect of the nitrogen and phosphorus in the waste liquid. Correspondingly, if the concentration of phosphorus in the waste liquid to be treated is more than 1mmol/L, the magnesium-alkali functional mineral material also needs to be increased by corresponding times.

In one embodiment of the present invention, the pH of the waste liquid to be treated is 1 to 10. Specifically, the pH of the waste liquid to be treated may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or the like. The invention has wider pH range, so the applicable waste liquid has wider pH range.

It is to be noted that the waste liquid to be treated is a waste liquid containing nitrogen and phosphorus, and may contain, for example, NH₄ ⁺And PO₄ ^3-And the like. The method for recovering nitrogen and phosphorus from the waste liquid by using the magnesium-alkali releasing functional mineral material provided by the embodiment of the invention can be suitable for removing nitrogen and phosphorus in public toilet fermentation liquid and the like.

The present invention will be described in detail with reference to examples.

Example 1A method for recovering nitrogen and phosphorus by using a novel magnesium-alkali releasing energy mineral material comprises the following steps:

1) preparing a magnesium-alkali functional mineral material: mixing mineral raw material (90 wt% serpentine Mg)₃Si₂O₅(OH)₄9 wt% of Mg (OH)₂And 1 wt% of other compounds) were placed in a reaction tank, and ball milling activation was performed using milling balls as milling media;

wherein the activation time is 120 min; the rotation speed of the ball mill is 500 rpm;

2) adding the magnesium-alkali release functional mineral material into the waste liquid to be treated for nitrogen and phosphorus recovery;

wherein the pH of the waste liquid to be treated is 7 and the NH of the waste liquid to be treated₄ ⁺And PO₄ ^3-The concentrations are respectively 10mM and 1mM, and the hydraulic retention time HRT is 30 min; adding amount of magnesium-alkali releasing functional mineral material to waste liquid to be treatedIs 0.8 g/L.

Testing the nitrogen and phosphorus recovery effect specifically as follows:

the phosphorus concentration in the solution samples was measured using ammonium molybdate spectrophotometry (GB 11893-89).

And (4) measuring the concentration of ammonia nitrogen in the solution sample by using a nano-reagent spectrophotometry (HJ 535-2009).

And calculating the recovery rate of nitrogen and phosphorus according to the residual amount of nitrogen and phosphorus in the solution before and after treatment.

The result shows that the recovery rate of phosphorus in the solution reaches 97.69 percent, and the recovery rate of ammonia nitrogen reaches 53.78 percent.

Example 2A method for recovering nitrogen and phosphorus by using a novel magnesium-alkali releasing energy mineral material comprises the following steps:

1) preparing a magnesium-alkali functional mineral material: mixing serpentine (100% Mg)₃Si₂O₅(OH)₄) Putting the mixture into a reaction tank, and performing ball milling activation by using grinding balls as grinding media;

wherein the activation time is 120 min; the rotation speed of the ball mill is 500 rpm;

2) adding the magnesium-alkali release functional mineral material into the waste liquid to be treated to remove nitrogen and phosphorus;

wherein the pH of the waste liquid to be treated is 7 and the NH of the waste liquid to be treated₄ ⁺And PO₄ ^3-The concentrations are respectively 10mM and 1mM, and the hydraulic retention time HRT is 30 min; the adding amount of the magnesium-alkali releasing functional mineral material to the waste liquid to be treated is 0.8 g/L.

The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1. The result shows that the recovery rate of phosphorus in the solution reaches 98.87 percent, and the recovery rate of ammonia nitrogen reaches 54.67 percent.

Examples 3 to 7

The difference from example 1 is that the hydraulic retention times HRT are 5, 15, 25, 40 and 60min, respectively.

The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1. As shown in Table 1, the recovery rates of phosphorus and ammonia nitrogen increased with the increase of the hydraulic retention time, HRT increased from 5min to 60min, the recovery rate of phosphorus increased from 40.56% to 99.98%, and the recovery rate of ammonia nitrogen increased from 5.31% to 78.98%.

TABLE 1 Effect of different hydraulic retention times on phosphorus and Ammonia Nitrogen recovery

Examples 8 to 11

The difference from example 1 is that the addition amount of the magnesium-alkali releasing functional mineral material to the waste liquid to be treated is 0.1, 0.3,0.5 and 1g/L, respectively.

The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1. As shown in Table 2, the recovery rates of phosphorus and ammonia nitrogen increase with the addition amount, wherein the recovery rate of phosphorus is kept above 93.51% and the recovery rate of ammonia nitrogen is kept above 46.78% when the addition amount is higher than 0.5 g/L.

TABLE 2 influence of different addition amounts on phosphorus and ammonia nitrogen recovery

Examples 12 to 14

The difference from example 1 is that the activation time was 15min, 30min and 60 min.

The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1. As a result, as shown in Table 3, the recovery rates of phosphorus and ammonia nitrogen increased with the increase of the activation time from 15min to 60min, the recovery rate of phosphorus increased from 4.67% to 78.54%, and the recovery rate of ammonia nitrogen increased from 1.45% to 45.78%.

TABLE 3 Effect of different activation times on phosphorus and Ammonia Nitrogen recovery

Examples 15 to 17

The same as example 1, except that the pH of the waste liquid to be treated was 3, 5 and 9, respectively.

The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1. As shown in Table 4, the recovery rate of ammonia nitrogen increased with the increase of the activation time, the pH value increased from 3 to 9, the recovery rate of ammonia nitrogen increased from 35.67% to 67.86%, the fluctuation of pH did not affect the recovery of phosphorus much, and the recovery rate was stabilized at about 98%. Indicating that the present technique is applicable to a wider pH range.

TABLE 4 Effect of different pH on phosphorus and Ammonia Nitrogen recovery

Examples 18 to 21

The same as example 1, except that the rotation speeds of the ball mill were 200, 300, 400 and 600rpm, respectively.

The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1. The results are shown in Table 5, where phosphorus recovery and ammonia nitrogen recovery both increased with increasing ball mill rotation speed. The rotating speed is increased from 200rpm to 600rpm, the recovery rate of phosphorus is increased from 23.21 percent to 99.98 percent, and the recovery rate of ammonia nitrogen is increased from 3.31 percent to 61.96 percent.

TABLE 5 influence of different ball milling speeds on the recovery of phosphorus and ammonia nitrogen

Examples 22 to 25

The difference from example 1 is that the addition amount of the magnesium-alkali releasing functional mineral material to the waste liquid to be treated is 0.1, 0.3,0.5 and 1g/L, respectively. The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1.

As shown in Table 6, the recovery rates of phosphorus and ammonia nitrogen increased with the increase of the added amount, wherein the recovery rate of phosphorus was maintained above 95.81% when the added amount was higher than 0.5g/L, and the recovery rate of ammonia nitrogen was higher than 48.87%.

TABLE 6 influence of different dosage on phosphorus and Ammonia Nitrogen recovery

Comparative example 1

The difference from example 1 is that the activation time was 0. The nitrogen and phosphorus recovery effect was tested in the same manner as in example 1.

The results show that the recovery rate of phosphorus is 2.37 percent and the recovery rate of ammonia nitrogen is 0.56 percent.

Test example 1Morphological and elemental characterization of functional mineral materials and post-reaction precipitated products

The functional mineral material prepared in example 1 is morphologically characterized as shown in fig. 1(a), and it can be seen that the mechanical activation causes the product particles to assume an irregular shape. And after the reaction is finished in the added filtrate, collecting the precipitate at the bottom as a recovered product. In the recovered product, most of the particles are in a regular columnar shape as shown in FIG. 1 (b). These regular particles are the newly formed compound. The results of the phase analysis of the recovered product are shown in FIG. 2 (a). The diffraction peak characteristics indicate that the recovered product is struvite that crystallizes well without other crystalline material. The particle size characteristics of the recovered product are shown in FIG. 2 (b). The particle size distribution range of the product is 0.2-100 μm, and the median particle size (D50) is 32.96 μm.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.