JP2015120167A - Phosphorus removal material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphorus removal material comprising a metal oxide which is heretofore unknown and exhibits a phosphorus adsorption rate sufficient for practical use, or a phosphorus adsorbent containing the same as an active ingredient.SOLUTION: There is provided a phosphorus removal material which fixes and removes phosphorus contained in waste water such as domestic waste water and business office waste water, and water in closed water area such as a pond and an inner bay. The phosphorus removal material exhibits characteristics of specifically adsorbing orthophosphate ions in water and desorbing the adsorbed orthophosphate ions by physical and chemical treatments, and is mainly composed of an oxide of a metal belonging to the transition metal group and a complex oxide thereof. Also there is provided a phosphorus adsorbent containing the same as an active ingredient.

Description

  The present invention relates to a phosphorus removing material for adsorbing and collecting phosphorus in domestic closed water such as domestic wastewater and various business establishments and 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, slaked lime, or the like is reacted with orthophosphoric acid ions in water and precipitated as hydroxyapatite on the surface of a seed crystal 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.

JP-A-8-10610 JP-A-11-147088 JP 2005-118614 A

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 precipitation method, a large excess of Ca ²⁺ is added as slaked lime to the orthophosphoric acid in water, and the poorly water-soluble hydroxyapatite (Ca ₁₀ (OH) ₂ (PO ₄ ) ₆ ), which is the reaction product, is coagulated. Although 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 to 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 influent 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 manufactured from TiOSO ₄ xH ₂ O, and phosphate ions that adsorb and desorb phosphate ions by adjusting pH. The recovery method is described.

  Thus, phosphorus removal using an adsorbent has already been proposed, but the description of the phosphorus removal rate, which is practically important as a phosphorus remover, is very small. Therefore, there is a technique introduced by the above patent document. Information is considered insufficient to determine whether it can be truly utilized for removing 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 removing material.

  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. The present inventors have found that cobalt oxide and zinc oxide, which are oxides of metals belonging to transition metals, exhibit sufficient phosphorus immobilization ability for removing phosphorus, and have further researched to complete the present invention. It was.

  That is, the present invention is a phosphorus removal material that fixes and removes wastewater such as domestic wastewater and industrial wastewater, and water in closed water areas such as pond water and inner bay, adsorbing orthophosphate ions in water, and It is characterized by comprising mainly oxides of metals belonging to transition metals and their complex oxides, which exhibit the property of desorbing orthophosphate ions adsorbed by physical and chemical treatment. Moreover, the phosphorus removal material which concerns on this invention consists of zinc oxide among the cobalt oxide and zinc oxide which are the oxides of the metal which belongs to the said transition metal, It is characterized by the above-mentioned. Furthermore, the present invention provides a phosphorus adsorbent comprising the phosphorus removing material described above as an active ingredient.

  In addition, although the oxide of the metal which belongs to the said transition metal shows the adsorption | suction characteristic of orthophosphate ion, in this invention, zinc oxide is used as an active ingredient of a phosphorus removal material.

  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 removal material.

  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 the composite oxide can be used as they are as a phosphorus removal material, but titanium oxide, iron oxide, silicon oxide, aluminum oxide, zeolite, charcoal, etc. 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 removing material can be obtained. According to this method, by changing the concentration of the aqueous solution, it becomes possible to control the coating amount and thickness of the metal oxide on the substrate surface of the finally obtained phosphorus removing material, as well as a large ratio. It is extremely effective because it is coated with a surface area. The phosphorus removing material thus obtained can adsorb phosphorus in the same manner as when the metal oxide is used as it is as the phosphorus removing material.

  Moreover, the phosphorus removal material of this invention can desorb | suck the adsorbed phosphorus by performing a physical and chemical process. 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 removing material. 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 removing material of the present invention, metal oxide that adsorbs orthophosphate ions is contacted to wastewater such as domestic wastewater and industrial wastewater containing orthophosphate 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 removing material of the present invention, it is possible to adsorb and remove orthophosphate ions from a solution containing orthophosphate ions at an extremely high speed. From this, the phosphorus processing apparatus using this removal material can be designed more compactly than the conventional apparatus.

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

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

  Hereinafter, the present invention will be described in more detail with reference to examples of phosphorus adsorption ability of metal oxides (cobalt oxide, zinc oxide, etc.) belonging to transition metals, but the present invention is not limited in any way by the following examples. It is not something. In addition, with respect to the metal oxides that are subject to the examples of the present invention and the metal oxides that are in the range of other reference examples, the same experiment was conducted for substances not listed in the examples, and the phosphorus adsorption characteristics In addition, the phosphorus release characteristics by physical and chemical treatment were confirmed. Among the following examples, Examples 1 and 3 to 4 are shown as reference examples, that is, reference examples.

After heating the metallic silver powder in an oxidizing atmosphere, the silver (I) oxide powder is added, and the concentrated aqueous solution of sodium hydroxide 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. B. of these samples E. T.A. The specific surface area by law is 0.57 m ² / g in silver oxide (I), was silver (II) oxide in 1.4 m ² / g.

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. B. of this sample E. T.A. The specific surface area determined by the 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 in which the temperature is raised to 1000 ° C. and held for 30 minutes, and further pulverized in a mortar. A fine powder was obtained. B. of this sample E. T.A. The specific surface area determined by the method was 3.6 m ² / g.

A neodymium (III) oxide powder was obtained by a known method of igniting neodymium hydroxide (III), and then further pulverized into a fine powder by a mortar. B. of this sample E. T.A. The specific surface area determined by the 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. By using potassium dihydrogen phosphate (KH ₂ PO ₄ ) as the orthophosphoric acid component, an orthophosphoric acid aqueous solution having a phosphorus concentration of 5 mg / L was prepared. 1 g of the above powder sample was added to 100 mL of this orthophosphate ion aqueous solution, 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 the 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 (I) oxide and silver (II) oxide prepared in Example 1 were phosphorus-immobilized. As for the concentration change leading to the immobilization of phosphorus, in silver oxide (I), the orthophosphate ion concentration after 1 hour of contact with the phosphoric acid aqueous solution is 0.21 mg / L, and after 6 hours after contact, it is almost 0 mg / L. 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, for 6 hours after contact. 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 approximately 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 used for the orthophosphoric acid ion adsorption experiment, that is, the phosphorus removing material in which 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 0.1N and 0.01N. 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 the 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 24 hours after contact. Then, an increase in orthophosphate ion concentration with an increase in contact time of approximately 0.76 mg / L 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 an aqueous 0.01N sodium hydroxide 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 sodium hydroxide aqueous solution, the orthophosphate ion concentration after 1 hour of contact is 0.50 mg / L, 6 hours after contact is 0.96 mg / L, and 24 hours after contact is almost 1 An increase in orthophosphate ion concentration with an increase in contact time of .6 mg / L 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. In addition, FIG. 2 shows phosphorus desorption characteristics in indium (III) oxide. The orthophosphate 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, 1.8 mg / L for contact. After 24 hours, a slight increase in orthophosphate ion concentration was measured as the contact time increased to approximately 1.9 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 0.01N aqueous sodium hydroxide solution for 24 hours, about 63% of the adsorbed phosphorus can be eliminated. 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. .1 mg / L, 24 hours after contact, approximately 2.3 mg / L, a slight increase in orthophosphate ion 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 0.1N aqueous sodium hydroxide solution for 24 hours, about 77% of the adsorbed phosphorus can be eliminated. 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.

  Phosphorus removal material 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 bream and red tide, etc., or domestic and industrial wastewater flowing into it, livestock farmers, etc. Purify agricultural wastewater. In particular, it is considered to be effectively used for removing phosphorus.

Claims (3)

Phosphorus removal material that fixes and removes phosphorus in water made of metal oxide,
1) The metal oxide is composed of an oxide of a metal belonging to a transition metal that exhibits the property of adsorbing orthophosphate ions in water and desorbing the adsorbed orthophosphate ions by performing physical and chemical treatments. 2) The phosphorus removing material, wherein the oxide of the metal belonging to the transition metal is made of zinc oxide, and 3) its usage is in the form of powder.   The phosphorus removing material according to claim 1, which adsorbs orthophosphate ions in water and desorbs the adsorbed orthophosphate ions by contact with a low concentration alkaline aqueous solution of 0.01 to 0.1N.   A phosphorus adsorbent comprising the phosphorus removing material according to claim 1 or 2 as an active ingredient.