JP2008023401A - Phosphorus adsorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal oxide which is not known to date and exhibits a practically sufficient adsorption rate, and a phosphorous adsorbent containing these as an active ingredient. <P>SOLUTION: The phosphorous adsorbent is a material for fixing/removing phosphorous in drainage such as domestic drainage and business drainage, and water of a closed water area such as pond water and an inner bay, and consists mainly of the metal oxide, and these composite oxides exhibiting a characteristic of peculiarly adsorbing orthophosphoric acid ions in water and desorbing orthophosphoric acid ions adsorbed by carrying out physical and chemical treatment, wherein the phosphorous adsorbent contains these as the active ingredient. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a phosphorus adsorbent for adsorbing and recovering wastewater such as domestic wastewater and various business establishment wastewater, and water in closed water such as pond water and inner bay.

  Conventionally, methods for removing phosphorus in water include biological dephosphorization methods that utilize the metabolism of microorganisms, coagulation precipitation methods that use metal salts and lime, crystallization dephosphorization methods that use phosphorus accumulation in seed crystals, Furthermore, an adsorption method is known.

  Among them, the biological dephosphorization method is performed by taking up and releasing phosphorus by microorganisms.

In addition, the coagulation sedimentation method removes phosphorus in water by adding slaked lime, ferric chloride, etc. to the wastewater, and solid-liquid separation of the metal phosphate with low solubility, which is generated by reaction of these with orthophosphoric acid. Is the method. The metal ion species used in this method are mainly Ca ²⁺ , Al ³⁺ , Fe ^3+, etc., but when the cation species is Ca ²⁺ , it is called a lime coagulation precipitation method.

The crystallization dephosphorization method applies a crystallization reaction in which phosphate crystals are precipitated from a supersaturated solution. Specifically, it is a method in which Ca ²⁺ supplied by addition of gypsum or slaked lime reacts with orthophosphate ions in water and precipitates as hydroxyapatite on the surface of seed crystals such as phosphate rock or bone charcoal. . Once the hydroxyapatite crystal is precipitated on the seed crystal, the precipitation is repeated on the surface of the seed crystal, so that sludge is not generated behind the dephosphorization tank, which is advantageous in comparison with the above two methods. It is.

As described above, several methods have already been proposed and put into practical use as means for removing phosphorus in water. However, these conventional techniques have technical problems that are desired to be solved. For example, the biological phosphorus removal method requires a delicate adjustment of the dissolved oxygen concentration, and the remaining treatment of excess sludge containing phosphorus remains a problem. In the coagulation sedimentation method, a large excess of Ca ²⁺ is added as slaked lime to the orthophosphoric acid in water, and the reaction product, poorly water-soluble hydroxyapatite (Ca ₁₀ (OH) ₂ (PO ₄ ) ₆ ), is added. Although coagulation sedimentation is required, it is necessary to eliminate and dispose of the generated sludge. Further, it is necessary to adjust the pH of the treated water and take measures against excess Ca ²⁺ . Furthermore, also in the crystallization dephosphorization method, it is necessary to add calcium ions that react with orthophosphoric acid to the inflow water and to precisely control the pH of the inflow water within a certain range.
Thus, in the prior art, there has been a problem that system management becomes complicated, such as processing of excess sludge and sludge, and supply of ionic species from outside the system. In particular, the treatment of sludge and sludge presents a problem that a further post-process is generated after the phosphorus removal process.
In recent years, an adsorption method has been proposed as a method for solving the above technical problems. The adsorption method uses a material that adsorbs phosphorus in water to immobilize phosphorus on the surface, remove phosphorus from the water, and remove the phosphorus immobilized on the surface by some physical and chemical means. Expected to lead to phosphorus recovery. If phosphorus recovery is performed at high concentration and high efficiency, it will be possible to open up the path to recovery of phosphorus resources.

  For example, Patent Document 1 reports a phosphorus adsorbent containing cerium oxide as an active ingredient or a phosphorus adsorbent containing a composite powder composed of cerium oxide and titanium oxide. Yes.

  Patent Document 2 reports that an attempt was made to remove phosphorus from wastewater using a material composed of zirconium ferrite hydrate as a phosphorus adsorbent. It has been proposed as a phosphorus removal method with low processing costs and no generation of aggregated precipitates.

Further, Patent Document 3 proposes a phosphate ion recovery material made of titanium hydroxide gel produced from TiOSO ₄ · xH ₂ O, and phosphate ions that adsorb and desorb phosphate ions by adjusting pH. The recovery method is described.

JP-A-8-10610 JP-A-11-147088 JP, 2005-118614, A In this way, phosphorus removal using an adsorbent has already been proposed, but there is little description about the phosphorus removal rate, which is practically important as a phosphorus remover, and therefore the above-mentioned patent. Information is considered inadequate to determine whether the technology introduced in the literature can truly be used to remove phosphorus in water.

  Therefore, the present invention has been made to solve the above-mentioned problems, and has found a material exhibiting a phosphorus removal rate sufficient for practical use for metal oxide powder samples other than the materials introduced in the patent literature. The present invention relates to a phosphorus adsorbent.

  As a result of examining the phosphorus removal characteristics of various metal oxides that have not been reported so far, the present inventors have solved the problems on or after the phosphorus removal treatment as described above. , Silver oxide, bismuth oxide, cobalt oxide, chromium oxide, dysprosium oxide, erbium oxide, gadolinium oxide, holmium oxide, indium oxide, lanthanum oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, samarium oxide, The inventors have found that tin, tantalum oxide, terbium oxide, yttrium oxide, ytterbium oxide, zinc oxide, and zirconium oxide exhibit sufficient phosphorus immobilization ability for removing phosphorus, and have completed the present invention.

That is, the present invention
It is a material that fixes and removes wastewater such as domestic wastewater and industrial wastewater, and water in closed water such as pond water and inner bay, and specifically adsorbs orthophosphate ions in water and performs physical and chemical treatment. It is characterized by being mainly composed of metal oxides and composite oxides that exhibit the property of desorbing orthophosphate ions adsorbed by application. Further, the phosphorus adsorbent according to the present invention has a metal oxide of silver oxide, bismuth oxide, cobalt oxide, chromium oxide, dysprosium oxide, erbium oxide, gadolinium oxide, holmium oxide, indium oxide, lanthanum oxide, niobium oxide, neodymium oxide. And nickel oxide, lead oxide, praseodymium oxide, samarium oxide, tin oxide, tantalum oxide, terbium oxide, yttrium oxide, ytterbium oxide, zinc oxide, and zirconium oxide. Furthermore, the present invention provides a phosphorus adsorbent comprising the phosphorus removing material described above as an active ingredient.

  In addition, although all the said metal oxides show the adsorption characteristic of orthophosphate ion, indium oxide, zinc oxide, cobalt oxide, erbium oxide, terbium oxide, holmium oxide, samarium oxide, neodymium oxide, and yttrium oxide are preferable.

The metal oxide is insoluble or sparingly soluble in an aqueous solution in a neutral region. However, in water containing orthophosphoric acid ions, it is partly due to the physical and chemical conditions of phosphorus-containing water, particularly the surface portion. May become hydrated (hydroxide). Such a case can also be used as a phosphorus adsorbent.

  That is, in the present invention, the metal oxide includes metal oxides, hydroxides, hydrated oxides, oxo acid salts and the like. These metal oxides can be obtained by a known method of heating or neutralizing a metal simple substance or a metal compound such as a chloride, nitrate, carbonate, sulfate, oxalate or the like.

  In the present invention, the metal oxide and these composite oxides can be used as they are as a phosphorus adsorbent, but titanium oxide, iron oxide, silicon oxide, aluminum oxide, zeolite, charcoal and the like are usually used in this field. It can be molded by being supported on or mixed with the substance being used. In synthesizing the molded body, the metal oxide may be in the form of a metal oxide at the stage of the starting material, or can be converted into a metal oxide by oxidizing the metal. That is, using a water-soluble metal salt as a starting material, immersing the base material in an aqueous solution using the metal salt, supporting the metal on the surface, and then oxidizing the metal oxide on the base material surface by various methods. A dispersed phosphorus adsorbent can be obtained. According to this method, by changing the concentration of the aqueous solution, it becomes possible not only to control the coating amount and thickness of the metal oxide on the substrate surface of the finally obtained phosphorus adsorbent, but also a large ratio. It is extremely effective because it is coated with a surface area. The phosphorus adsorbent thus obtained can adsorb phosphorus in the same manner as when the metal oxide is used as it is as the phosphorus adsorbent.

  Moreover, the phosphorus adsorbent of the present invention can be desorbed by adsorbing phosphorus by performing physical and chemical treatments. Examples of physical treatment include ultrasonic waves, heating, applied voltage, atmospheric pressure / water pressure control, and examples of chemical treatment include pH control with acid / alkali. The detached phosphorus component can be separated and recovered from the phosphorus adsorbent. Furthermore, the recovered phosphorus component can be concentrated and / or reacted with calcium ions, sodium ions, etc. to form insoluble phosphorus compounds, which can be used not only for general purposes such as fertilizer but also in various industrial fields. Make it possible.

  According to the phosphorus adsorbing material of the present invention, metal oxide that adsorbs orthophosphoric acid surface is contacted to wastewater such as domestic wastewater and industrial wastewater containing orthophosphoric acid ions and closed water areas such as pond water and inner bay. By doing so, orthophosphate ions can be effectively adsorbed and removed, and treated water having a low orthophosphate ion concentration can be obtained.

  According to the phosphorus adsorbent of the present invention, it is possible to adsorb and remove orthophosphate ions at a very high speed from a solution containing orthophosphate ions. From this, the phosphorus processing apparatus using this adsorbent can be designed more compactly than the conventional apparatus.

  In addition, the phosphorus adsorbent according to the present invention can be desorbed by performing physical and chemical treatment on orthophosphate ions adsorbed on the surface thereof, and phosphorus can be recovered as a resource.

  Hereinafter, the present invention will be described in more detail with reference to some typical examples of the phosphorus adsorption ability of metal oxides which form the basis of the present invention. However, the present invention is not limited to these examples. It is not something. It should be noted that, in the metal oxides that fall within the scope of the present invention, it is possible to conduct experiments similar to the examples for substances not listed in the examples, and to show phosphorus adsorption characteristics and phosphorus desorption characteristics by physical and chemical treatment. Already confirmed.

After heating the metallic silver powder in an oxidizing atmosphere, the silver (I) oxide powder is added, and the concentrated aqueous solution of sodium nitrate and potassium peroxodisulfate is added to the concentrated aqueous solution of silver nitrate. By performing the treatment, a silver (II) oxide powder was obtained. Any method for obtaining these metal oxides is known. The obtained powder was further pulverized with a mortar to obtain a fine powder. The specific surface areas of these samples by the BET method were 0.57 m ² / g for silver oxide (I) and 1.4 m ² / g for silver oxide (II).

After obtaining cobalt oxide (II) powder by a known method of heating metallic cobalt in an oxidizing atmosphere, it was further pulverized into a fine powder by a mortar. The specific surface area of this sample by the BET method was 24 m ² / g.

After indium (III) hydroxide is heated to 850 ° C. to a constant weight, indium (III) oxide powder is obtained by a known method of heating to 1000 ° C. and holding for 30 minutes, and then further pulverized in a mortar A fine powder was obtained. The specific surface area of this sample by the BET method was 3.6 m ² / g.

After obtaining neodymium (III) oxide powder by a known method of igniting neodymium (III) hydroxide, it was further pulverized into a fine powder by a mortar. The specific surface area of this sample by the BET method was 0.76 m ² / g.

About the metal oxide powder sample obtained in Examples 1-4, the batch type adsorption experiment of orthophosphate ion was performed as follows. An orthophosphoric acid aqueous solution with a phosphorus concentration of 5 mg / L was prepared using potassium dihydrogen phosphate (KH ₂ PO ₄ ) as the orthophosphoric acid component. To 100 mL of this orthophosphate ion aqueous solution, 1 g of the above powder sample was added, and then stirred with a magnetic stirrer while maintaining the solution system at 20 ° C. With stirring, the supernatant was sampled with a syringe after 1 hour, 6 hours, and 24 hours from the contact between the aqueous orthophosphate ion solution and the above powder sample, and this was filtered through an ortholine solution of the solution filtered through a filter with a nominal pore size of 0.45 μm. The concentration of acid ions was measured with a spectrophotometer by the molybdenum blue method. The result is shown in FIG. In any case, a decrease in the orthophosphate ion concentration is observed, indicating that phosphorus was immobilized by the powder sample. As is clear from FIG. 1, both silver oxide (I) and silver oxide (II) prepared in Example 1 were immobilized with phosphorus. The concentration change that leads to the immobilization of phosphorus is 0.21 mg / L for the orthophosphate ion concentration after 1 hour contact with phosphoric acid aqueous solution and almost 0 mg / L after 6 hours contact with phosphoric acid aqueous solution. In silver (II) oxide, it was 2.4 mg / L in 1 hour after contact, and was almost 0 mg / L after 6 hours in contact. That is, in the metal oxide that adsorbs orthophosphate ions, it can be seen that phosphorous immobilization basically occurs in the same manner even if the chemical state of the metal is different. Moreover, in FIG. 1, the immobilization of phosphorus by the cobalt (II) oxide produced in Example 2 was shown. The orthophosphate ion concentration after 1 hour of contact with the phosphoric acid aqueous solution was 4.6 mg / L, 6 hours after contact was 2.8 mg / L, and 24 hours after contact was almost 0 mg / L. In addition, as shown in FIG. 1, the indium (III) oxide produced in Example 3 also exhibits phosphorus adsorption characteristics, and the orthophosphate ion concentration for 1 hour after contact with the phosphoric acid aqueous solution is 3.1 mg / L, and for 6 hours after contact. The dose was 2.7 mg / L and approximately 2.3 mg / L at 24 hours after contact. That is, indium (III) oxide is not large in phosphorus adsorption amount, but its adsorption rate is large. Furthermore, from FIG. 1, the neodymium (III) oxide produced in Example 4 also showed phosphorus adsorption characteristics, and the orthophosphate ion concentration after 1 hour after contact with the phosphoric acid aqueous solution was almost 0 mg / L. . That is, neodymium (III) oxide exhibits a large phosphorus adsorption amount, and its adsorption rate is extremely high.

  Next, the phosphorus desorption experiment was performed as follows on the sample after use in the adsorption experiment of orthophosphate ions, that is, the phosphorus adsorbent in a state where phosphorus was adsorbed on the surface. The desorption treatment solution used in the phosphorus desorption experiment is an aqueous sodium hydroxide solution. The aqueous sodium hydroxide solution was prepared at two concentrations of 0.1 N and 0.01 N. 0.5 g of the sample obtained in the example was added to 50 mL of these sodium hydroxide aqueous solutions, and then stirred with a magnetic stirrer while maintaining the solution system at 20 ° C. With stirring, the supernatant was sampled with a syringe after 1 hour, 6 hours, and 24 hours from the contact between the aqueous orthophosphate ion solution and the above powder sample, and this was filtered through an ortholine solution of the solution filtered through a filter with a nominal pore size of 0.45 μm. The concentration of acid ions was measured with a spectrophotometer by the molybdenum blue method. The results for cobalt (II) oxide and indium oxide are shown in FIG. An increase in orthophosphate ion concentration indicates desorption of orthophosphate ions from the sample surface. FIG. 2 shows phosphorus release characteristics in cobalt (II) oxide. The concentration change that leads to the elimination of phosphorus is 0.38 mg / L for 1 hour after contact with 0.01N sodium hydroxide aqueous solution, 0.62 mg / L for 6 hours after contact, and approximately 0.76 for 24 hours after contact. An increase in orthophosphate ion concentration with increasing mg / L and contact time was measured. The theoretical concentration of orthophosphate ion that is considered to be measured when the total amount of phosphorus adsorbed on cobalt (II) oxide is desorbed is 5.2 mg / L. That is, by bringing cobalt (II) oxide into contact with a 0.01N sodium hydroxide aqueous solution for 24 hours, about 15% of the adsorbed phosphorus can be eliminated. On the other hand, in the case of contact with a 0.1N aqueous sodium hydroxide solution, the orthophosphate ion concentration for 1 hour after contact is 0.50 mg / L, 6 hours after contact is 0.96 mg / L, and 24 hours after contact is approximately 1.6 mg / L. The increase in orthophosphate ion concentration with increasing contact time was measured. The theoretical concentration of orthophosphate ion that is considered to be measured when the total amount of phosphorus adsorbed on cobalt (II) oxide is desorbed is 5.2 mg / L. That is, by bringing cobalt (II) oxide into contact with a 0.1N aqueous sodium hydroxide solution for 24 hours, about 31% of the adsorbed phosphorus can be eliminated. Further, FIG. 2 shows phosphorus desorption characteristics in indium (III) oxide. The orthophosphoric acid ion concentration for 1 hour after contact with 0.01N sodium hydroxide aqueous solution was 1.6 mg / L, and rapid desorption of phosphorus was measured. Then, 6 hours after contact was 1.8 mg / L, and 24 hours after contact. In the case of 1.9 mg / L, a slight increase in orthophosphate concentration was measured as the contact time increased. When the total amount of phosphorus adsorbed on indium (III) oxide is desorbed, the theoretical concentration of orthophosphate ions is 3.0 mg / L. That is, by bringing indium (III) oxide into contact with a 0.01N sodium hydroxide aqueous solution for 24 hours, about 63% of the adsorbed phosphorus can be desorbed. On the other hand, in the case of contact with a 0.1N sodium hydroxide aqueous solution, the orthophosphate ion concentration after 1 hour of contact was 2.0 mg / L, and rapid desorption of phosphorus was measured. L, 24 hours after contact, a slight increase in orthophosphate ion concentration was measured as the contact time increased to approximately 2.3 mg / L. When the total amount of phosphorus adsorbed on indium (III) oxide is desorbed, the theoretical concentration of orthophosphate ions is 3.0 mg / L. That is, by bringing indium (III) oxide into contact with a 0.1N aqueous sodium hydroxide solution for 24 hours, about 77% of the adsorbed phosphorus can be desorbed. From the above results, the concentration of the treatment liquid used for the desorption treatment of orthophosphate ions adsorbed on the adsorbent surface is preferably 0.1 N rather than 0.01 N, and a high phosphorus desorption effect was obtained.

The phosphorus adsorbent according to the present invention is a closed water environment in which eutrophication has progressed in recent years and there is a concern about the occurrence of blue sea cucumber and red tide, etc. Purify agricultural wastewater. In particular, it is considered to be effectively used for removing phosphorus.

It is the graph which showed a part of phosphorus adsorption | suction experiment result by the metal oxide of this invention. It is the graph which showed a part of phosphorus desorption experiment result by the metal oxide of this invention.

Claims (3)

  It is a material that fixes and removes wastewater such as domestic wastewater and industrial wastewater, and water in closed water such as pond water and inner bay, and specifically adsorbs orthophosphate ions in water and performs physical and chemical treatment. A phosphorus adsorbent comprising mainly a metal oxide and a composite oxide thereof exhibiting a property of desorbing orthophosphate ions adsorbed by application.   The metal oxide is silver oxide, bismuth oxide, cobalt oxide, chromium oxide, dysprosium oxide, erbium oxide, gadolinium oxide, holmium oxide, indium oxide, lanthanum oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, The phosphorus adsorbent according to claim 1, comprising at least one of samarium oxide, tin oxide, tantalum oxide, terbium oxide, yttrium oxide, ytterbium oxide, zinc oxide, and zirconium oxide. A phosphorus adsorbent comprising the phosphorus adsorbent according to claim 1 or 2 as an active ingredient.

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