JPS6164388A - Removal of phosphorus in water - Google Patents

Abstract

PURPOSE:To efficiently adsorb the phosphorus component in water by a specific adsorbent, by contacting water with a chemical adsorbent wherein a specific amount of Al2O3 is contained and a specific amount of an Al-salt or iron salt is supported by an inorg. porous substrate having a specific pore size. CONSTITUTION:At least one of an Al-salt (e.g., aluminum sulfate) or iron salt (e.g., ferric sulfate) is supported by an inorg. porous substrate (e.g., activated alumina), wherein the content of Al2O3 is 30wt% or more and the volume of fine pores with a pore size of 2-30nm is 0.15ml/g or more, in an amount of 5X10<-5>-1X10<-3>mol per 1g of the substrate to prepare a chemical adsorbent. This chemical adsorbent is contacted with water containing a phosphorus component to adsorb said phosphorus component. As a result, phosphorus can be removed in a wide concn. range without requiring complicated control. This adsorbent is especially suitable for removing phosphorus from an intermediate and small scale living waste water and industrial waste water.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a new method for removing phosphorus from water such as wastewater, and more particularly to a new method for removing phosphorus from water such as domestic sewage, industrial wastewater and industrial water. The present invention relates to a method of removing phosphoric acid using a chemical adsorbent containing aluminum or iron, desorbing and recovering the adsorbed phosphoric acid, and repeatedly reusing the adsorbent.

Prior Art and Technical Problems of the Invention Due to an increase in nutrients, especially phosphorus, flowing into lakes, internal bays, etc., eutrophication progresses, and various damages are caused by abnormal growth of algae. Therefore, there is a need to develop a method for removing phosphorus from wastewater. Furthermore, there is a need to develop an excellent method for suppressing the generation of microbial slime in equipment, piping, etc. by removing phosphorus from industrial water. Furthermore 1. Phosphorus resources are in short supply worldwide, and Japan is almost entirely dependent on imports, so there is a need to develop an excellent method for recovering phosphorus from wastewater.

Conventional methods for removing phosphorus from water include the coagulation-sedimentation method, which involves adding aluminum salts, iron salts, or calcium salts to coagulate the phosphoric acid content as phlegmatic phosphates, and separating it by sedimentation, activated sludge, etc. The biological tax phosphorus method involves introducing phosphorus into microorganisms and then separating the microorganisms by precipitation, the crystallization method in which phosphoric acid is precipitated as hydroxyapatite on granular calcium phosphate, and the ion exchange method in which phosphoric acid is exchanged and adsorbed on an anion exchange resin. Attempts are being made to put the law into practical use.

However, each of these methods has fundamental problems and is difficult to economically apply, especially to small and medium scale water treatment. That is, the coagulation-sedimentation method requires large equipment and produces a large amount of settled sludge with a high moisture content, which is not only difficult to process and dispose of afterwards, but also difficult to recover phosphorus. The biological dephosphorization method is difficult to apply except when specific pollutants are being removed using activated sludge, etc., and not only does it require large equipment and complicated control, but it is also difficult to recover phosphorus. The crystallization method requires complex pretreatments such as decarboxylation by adding acid and increasing the degree of supersaturation by adding calcium, making it difficult to control the conditions.
Also, low concentrations of phosphorus cannot be removed. In the ion exchange method, there is a large interference with other coexisting inorganic ions and organic substances, making stable treatment difficult, and because the adsorption capacity is small, only a small amount of water can be treated even if expensive resins are used.

Purpose and Effect of the Invention The present invention has been made in view of the current situation, and according to the phosphorus removal method of the present invention, a chemical adsorbent and water containing phosphoric acid are brought into contact with each other using a simple device. It has the characteristic of being able to remove phosphorus in a wide range of concentrations without requiring complicated control, and is particularly suitable for removing phosphorus from small and medium-sized domestic wastewater, industrial wastewater, etc. In addition, phosphorus adsorbed on the adsorbent can be desorbed by a basic solution and recovered as a concentrated phosphorus solution, and the adsorbent can be repeatedly recycled and used. Another major feature is that it generates almost no sludge that requires post-treatment.

Summary of the Invention In other words, the method for removing phosphorus of the present invention uses a natural or synthetic material that has a high content of aluminum oxide, which has the effect of chemically adsorbing phosphoric acid, and has many fine pores that are effective for adsorption and drug loading. The porous solid of is desorbed using a suitable basic bath solution at 0 degrees,
It is characterized by being regenerated.

Structure of the Invention According to the present invention, the aluminum bride content is 50% by weight or more, and the volume of pores with a pore diameter of 2 nm or more and 30 am or less is 0.15% per 1 g. y or more, 1 x at least 5 x 10-5 per gram of base material.
A chemical adsorbent carrying at least one type of aluminum salt or iron salt in an amount of 10-' mole or less is brought into contact with water containing phosphoric acid, and the phosphoric acid in the water is adsorbed onto the adsorbent. A method for removing phosphorus in water is provided.

Further, according to the present invention, in the above method, the chemical adsorbent on which phosphoric acid has been adsorbed is brought into contact with a basic solution of I x 10-2 normal or higher to remove the adsorbed phosphoric acid, and the regeneration treatment is performed. Provided is a method for removing phosphorus from water, which is characterized in that the chemical adsorbent thus prepared is repeatedly used for adsorption treatment of phosphoric acid components.

Preferred embodiments of the invention The present invention will be explained in detail below.

Substrate The substrate of the chemical adsorbent used in the present invention will be described below. Certain clay minerals in soil damage adsorb phosphoric acid, but the phosphorus adsorption ability of such clay minerals is
This is thought to be due to the fact that the porous and active aluminum oxide that forms the surface chemically adsorbs 1 liter of phosphorus.

Typical clay minerals kaolinite, montmorillonite, bentonite, two types of allophane and 3fm'l
The results of testing the phosphorus adsorption performance of synthetic alumina A from sodium phosphorus dihydrogen solution (1 g of adsorbent) are as follows:
Table 1 shows the adsorption amount in terms of phosphorus atoms per unit. Also,
Figure 1 shows the volume distribution of pores with a diameter of 6 or LrrL or less for these base materials, and shows that pores with a diameter of 2 nm or more and 50 a, which are considered effective for adsorption and drug loading, are shown in Figure 1.
Table 2 shows the pore volume of /n or less.

Kaolinite 0.2 or less Montmorillonite 0.2 or less Bentonite
0.2 or less Allofen A 10
．． 0 Allophane B1.5 C Old Notes Alumina A, 17.5 Activated Alumina B 14.8 Alumina C1,9 Table 2 Kaolinite 40,5 45.9 0.
03 Montmorillonite 21.9 58.0
0.08 bentonite 15.4 69.
5 0.167o Fe:yA 39.4 3a
1 0j1 aofe:,yB 35.5 2
a8 0.08 activated alumina A 80.4
1g. 6 0.25 Activated Alumina B 93.
7 0.3 0.30 aluminum f C9a5
0.0 0.0 tatami diameter 2nrn or more, 3Q nm
As shown in pore volume Table 1 below, among the base materials, montmorillonite and bentonite, which have an aluminum oxide content of less than 30 inches, hardly adsorb phosphorus.

In addition, even if the aluminum oxide content is 30% or more, the pore volume with a diameter of 2rLrn to 30rLrIL is 0.15- or less per gram, allophane B
and alumina C adsorbs only a small amount of phosphorus. On the other hand, it was found that Alofue/A, activated alumina A, and activated alumina B, which have a high aluminum oxide content and a large pore volume, have significantly high phosphorus adsorption performance. That is, the aluminum oxide content is 30 inches or more, and the A'lB hole volume is 1 with a diameter of 2rLm or more and 301 doors or less.
．． It has been found that a porous solid having a ratio of 0.15 to 9 or more adsorbs and removes phosphoric acid from water well.

Aluminum Voice C1g□ Next, we will discuss how to further improve the performance of porous substrates whose phosphorus adsorption performance has deteriorated. Is there a salt that reacts with phosphoric acid to the above-mentioned Alofe/A and activated alumina A? The resulting aqueous solution of calcium, magnesium, aluminum or iron chloride or sulfur salt is
Table 6 shows the results of testing the phosphorus adsorption performance from a phosphorus salt solution for motsu impregnated, impregnated, and supported in an amount of 1.5 x 10 -' equivalent per J.

Table 6 As shown in Table 6, those impregnated with calcium salts and magnesium salts showed only a slight improvement in phosphorus adsorption performance, but those impregnated with aluminum salts and iron salts, especially aluminum sulfate and ferric sulfate, did not improve. It was found that the phosphorus adsorption performance was significantly improved.

Table 4 shows the results obtained by testing the phosphorus adsorption performance of

Table 4 As shown in Table 4, if the impregnated amount of aluminum sulfate or iron sulfate is less than 5 x 10-5 mol/g, the impregnated amount is insufficient and the improvement in phosphorus adsorption performance is small; It has been found that when /y or more, the pores of the base material are blocked by the impregnated material, making it difficult to react to the inside, so that the improvement in phosphorus adsorption performance is rather reduced. Furthermore, even when approximately 500 I'n9/l of chloride ions and sulfate ions were present in the adsorption solution, there was almost no change in the adsorption performance, and it was confirmed that the adsorption of phosphoric acid was hardly hindered by these ions.

In addition, similar phosphorus adsorption performance was shown when a sodium tripolyphosphate water bath solution was used. In addition, bentonite contains 3.4
Even when x10-'mol/y of aluminum sulfate was impregnated, the phosphorus adsorption performance was 5m9/9 or less.

Water Treatment The treatment method of the present invention can be applied to any water containing phosphoric acid, such as urban sewage, chemical factory wastewater, food industry wastewater, etc. The chemical adsorbent used can be used in any form such as powder or granules, but from the standpoint of separation from treated water and regeneration treatment, granules are preferable, especially those with a diameter of 0.5 to 0. It is preferable to use it in the form of 5-ounce granules.

Contact treatment of water and chemical adsorbent can be carried out, for example, by mixing the water to be treated with the chemical adsorbent and separating the adsorbent that has adsorbed phosphoric acid by sedimentation, or by treating it in a packed bed of adsorbent. This can be carried out by a method of adsorbing the phosphoric acid content in the water by passing it through the water.

In the latter process, the adsorbent can be used as a fixed bed or as a moving or fluidized bed. Additionally, multiple packed beds of chemical adsorbent may be used, one for the adsorption process and the other for the regeneration process described below. FIG. 6 is a process diagram for the former mixing-precipitation separation method, and FIG. 4 is a process diagram for the latter packed bed method.

Since the contact treatment between water and the chemical adsorbent proceeds satisfactorily at room temperature, special operations such as heating are unnecessary, but of course the present invention can also be applied to high temperature water.

The contact time between water and the chemical adsorbent varies depending on the temperature and the desired degree of phosphoric acid removal, but is generally selected from a range of 10 minutes to 10 hours.

Regeneration of adsorbent and recovery of phosphorus A method for desorbing and recovering the phosphoric acid adsorbed on the chemical adsorbent and regenerating the adsorbent will be described below. It is known that aluminum phosphate is easily dissolved in a basic solution with a high pH or in an acidic solution with a low pH. Therefore, 1 g of activated alumina A contains 3.4x of aluminum.
10-mol or 2.5 x 10-4 ferric sulfate
For a chemical adsorbent with molar loading, the phosphorus adsorption p
The results of examining changes due to H are shown in Figure 2. From now on P
At H9 or below or pH1 or below, the adsorption of phosphorus becomes extremely small, and it was thought that phosphorus could be removed using a basic solution with a pH of 9 or above or an acidic solution with a pH of 1 or below. It was thought that the desorption rate would increase at higher temperatures.

However, in order to almost completely desorb the adsorbed phosphorus,
It is necessary to add a sufficient amount of base to replace the adsorbed phosphorus. That is, the chemical adsorbent used in the present invention has 1
about 1 x 10-' moles of phosphorus per g, or about 3
Since x 10''-' equivalents of phosphorus are adsorbed, more base needs to be added.

That is, in the case of an α-defined base, it is necessary to use a solution of 3/c or more per 1 g. However, if a too dilute solution is used, the amount of desorbed liquid will be large and the phosphorus concentration in the desorbed liquid will be low.

When using a base solution of 3/c-/g, the 0 degree phosphorus in the desorbed solution is approximately 64 mol/l, or approximately 1×10 α
n9/I! However, in general, in order to properly perform the post-treatment of the desorbed ly and the recovery and utilization of phosphorus, the phosphorus concentration in the desorbed liquid must be at least 102m9/1 or higher. Therefore, it is necessary to use a basic temperature of 10-2 normal or more for desorption.

Therefore, 6 phosphorus was added to a chemical adsorbent impregnated with 3.4 x 10-' moles of aluminum sulfate per gram of activated alumina A.
After adsorption of 1 m9, a phosphorus desorption test was performed by adding 10 rnt per 0.5N sodium hydroxide aqueous i'fl [kl, F], and as a result, more than 98% of the adsorbed phosphorus was desorbed, approximately 6ooom9 It was found that a phosphorus-rich solution of /z was recovered. In addition, when the adsorbent after desorbing phosphorus was again impregnated with sulfuric acid acidic aluminum sulfate and supported on it to adsorb phosphorus repeatedly, it was confirmed that the adsorbent had an adsorption performance of 96% or more of the new adsorbent.

In the present invention, as described above, an appropriate amount of aluminum salt that reacts with phosphoric acid is applied to a porous base material that has a high aluminum oxide content, has many pores, has excellent phosphorus adsorption performance, and has excellent drug support performance. Alternatively, by using a chemical adsorbent impregnated and supported with iron salt, phosphorus in water can be efficiently removed.In addition, a large amount of phosphorus can be removed by using a basic solution with an appropriate concentration. The phosphorus adsorbent is desorbed and recovered as a containing liquid, and the phosphorus adsorbent can be used repeatedly by impregnating it with aluminum salt or iron salt.

Example Examples of the present invention will be described below.

Example 1゜Allophane A per unit amount, 0.15 mol/I! After adding 21 ml of aluminum sulfate aqueous solution and mixing thoroughly, 12
In apparatus 2, in which a chemical adsorbent prepared by drying at 0° C. for 1 hour was arranged as shown in the flowchart of FIG. 6, phosphorus was absorbed on average by 3.
When 80 mg/z was added to activated sludge treated water from a certain food factory wastewater containing 2 my/z and mixed for 2 hours, it was allowed to precipitate in a device filter.The phosphorus concentration was 1.0rn9/z or less, and the adsorbent was quickly released. The volume of sludge produced is approximately 3 times smaller than that of coagulation and sedimentation using aluminum sulfate.
It became less than 1/0. In addition, after separating the precipitated adsorbent, 10 times the amount of 0.4 N sodium hydroxide was added in apparatus 6 and mixed for 6 hours, resulting in approximately 2000 m9/I! A liquid containing phosphorus was recovered. Furthermore, after separating the adsorbent, double the amount of aluminum sulfate sulfate is added, and about 10% of the new adsorbent is added.
In addition, when it was used again for wastewater treatment, sufficient phosphorus removal was achieved.

Example 2゜ Diameter of about 2 to 6 0.2 per 9 to the same activated alumina A1
1.51 mol/l of aluminum sulfate solution! In addition, the chemical adsorbent produced by sufficiently mixing and supporting the chemical adsorbent was filled into the device 8 arranged as shown in the flowchart of FIG.
When coagulation-sedimentation treated water of a certain chemical factory wastewater containing 1m9/l was passed through at a space velocity of about 5/hour, the filling volume was about 7000.
The phosphorus concentration in the treated water was below 1 .mu./l until the water flow was doubled. In addition, when a 0.6 N sodium hydroxide solution was passed through the adsorbent from which a large amount of phosphorus had been removed at a space velocity of approximately 1/hour, the amount of adsorption was approximately 5 times the filling volume. Approximately 90% of phosphorus is approximately 3000m9/I! It was desorbed and recovered as a liquid containing concentrated phosphorus. In addition, after extracting the IJium hydroxide solution remaining after desorption, it is filled with a sulfuric acid acidic aluminum sulfate solution to impregnate and support it.
When the wastewater was passed through again, the phosphorus could be removed repeatedly.

Example 6゜The same chemical adsorbent as in Example 2 was filled into the same apparatus,
When treated water from a septic tank for underground water containing 3.27 #/hr of phosphorus on average was passed through the water at a space velocity of about 6/hour after 5 hours, the phosphorus concentration in the treated water remained at 1 until about 8,000 times the filling volume was passed. ~/ was below. The adsorbent that removed this phosphorus is
The adsorbent was periodically removed and replaced with regenerated adsorbent. The extracted adsorbent was collected together with other adsorbents used to remove phosphorus from wastewater, and about 7 times the amount of 0.5 N sodium hydroxide solution was added to collect the liquid containing about 4000 μ/L of phosphorus. After the adsorbent was neutralized with sulfuric acid, aluminum sulfate was again impregnated and supported, and the adsorbent was used repeatedly. Furthermore, when calcium hydroxide was added to the desorption recovery solution, most of the phosphorus was precipitated and separated as calcium phosphate, and the remaining concentrated sodium hydroxide solution could be used again as a desorption solution.

Example 4 The same chemical adsorbent as in Example 2 was filled in a similar small device, and tea-based chemical industrial water containing an average of 0.07 m/h of phosphorus was passed through it at a space velocity of about 6/h. The phosphorus concentration in the treated water remains 0.0 until approximately 30,000 times the filling volume is passed through.
1/cm or less, and the occurrence of microorganisms such as bacteria in the storage tank was significantly reduced. The used chemical adsorbent was discarded and replaced with a new chemical adsorbent.

[Brief explanation of drawings]

Figure 1 shows the cumulative pore volume distribution curve of the chemical adsorbent base material used in the present invention, Figure 2 shows an example of the change in phosphorus adsorption performance of the chemical adsorbent of the present invention due to pH, and Figure 6 shows , an example of a process diagram for removing phosphorus from wastewater using the chemical adsorbent of the present invention in powder form; FIG. This is an example of a diagram. Reference number 1 is waste water, 2 is adsorbent mixing tank, 3 is sedimentation separation tank, 4 is filtration tower, 5 is treated water, 6 is adsorbent desorption regeneration tank, 7
8 is a phosphorus recovery tank, 8 is an adsorption/desorption device filled with an adsorbent, 9 is a hydroxide (IJ) solution tank, and 10 is a sulfuric acid acidic aluminum sulfate solution tank.

Claims (2)

[Claims] (1) An inorganic porous base material in which the aluminum oxide content is 30% by weight or more and the volume of pores with a pore diameter of 2 nm or more and 30 nm or less is 0.15 ml or more per 19,
5 x 10^-5^mol or more per 1g of base material, 1 x 10^-
A chemical adsorbent carrying at least one type of aluminum salt or iron salt in an amount of 3 moles or less is brought into contact with water containing phosphoric acid, and the phosphoric acid in the water is adsorbed by the adsorbent. A method for removing phosphorus from water. (2) An inorganic porous base material having an aluminum oxide content of 30% by weight or more and a volume of pores with a pore diameter of 2 nm or more and 30 nm or less of 0.15 ml or more per 1 g;
5 x 10^-^5 moles or more per 1g of base material, 1 x 10^-
A chemical adsorbent carrying at least one type of aluminum salt or iron salt in an amount of 3 moles or less is brought into contact with water containing a phosphoric acid content, and the phosphoric acid content in the water is adsorbed onto the adsorbent, 1 x 10 ^-^ chemical adsorbent with phosphoric acid adsorbed
A method for removing phosphorus from water, which comprises contacting with a basic solution of 2N or more to remove adsorbed phosphoric acid, and repeatedly using the regenerated chemical adsorbent for adsorption treatment of phosphoric acid. .