JP2007001835A - Phosphorus adsorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to remove or recover phosphorus in water efficiently. <P>SOLUTION: A method for removing phosphorus in a phosphorus-containing waste water by using a phosphorus adsorbent which is represented by general formula (1): Fe(OH)<SB>m</SB>(SO<SB>4</SB>)<SB>n</SB>lH<SB>2</SB>O (wherein, 2≤m<3; 0<n≤0.5; 0≤l≤0.5) or its hydrate formed in an aqueous solution is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a compound that adsorbs phosphorus, a phosphorus adsorbent, a method for producing them, and a method for removing or recovering phosphorus.

  Phosphorus in wastewater discharged from factories and households causes eutrophication of rivers, lakes, and seawater, and causes environmental destruction. Therefore, technology development to remove and recover this has been required.

Various phosphorus adsorbents have been proposed so far (Patent Documents 1 to 3), but their phosphorus adsorption capacity is insufficient, or the production cost of the phosphorus adsorbent is high and not practical. was there. Furthermore, phosphorus adsorption capacity tends to decrease in wastewater with a high salt concentration such as seawater, and a phosphorus adsorbent having an excellent phosphorus adsorption capacity is required even in wastewater with a high salt concentration such as seawater.
JP2004-89760 JP 2005-28247 A Japanese Patent Laid-Open No. 7-60261

  An object of the present invention is to provide a technique for efficiently removing or recovering phosphorus in water.

  As a result of repeated studies in view of the above problems, the present inventors have made a basic to alkaline solution by adding a base to an aqueous solution in which iron (II) sulfate and iron (III) are dissolved. It has been found that it has an adsorption capacity.

  The present invention relates to the following compounds, phosphorus adsorbents and methods for producing them, and methods for removing phosphorus from waste water.

1. formula:
Fe (OH) _2.6 (SO ₄ ) _0.2
And the hydrate formed in an aqueous solution. General formula (1):
Fe (OH) _m (SO ₄ ) _n · lH ₂ O (1)
(In the formula, 2 ≦ m <3, 0 <n ≦ 0.5, 0 ≦ l ≦ 0.5.)
And a hydrate formed in an aqueous solution.

3. General formula (1):
Fe (OH) _m (SO ₄ ) _n · lH ₂ O (1)
(In the formula, 2 ≦ m <3, 0 <n ≦ 0.5, 0 ≦ l ≦ 0.5.)
And the use for adsorption of phosphorus of the hydrate formed in an aqueous solution.

4). A general formula (1) characterized in that a base is added to a mixed aqueous solution containing FeSO ₄ and Fe ₂ (SO ₄ ) ₃ to produce a precipitate from neutral to alkaline.
Fe (OH) _m (SO ₄ ) _n · lH ₂ O (1)
(In the formula, 2 ≦ m <3, 0 <n ≦ 0.5, 0 ≦ l ≦ 0.5.)
And a method for producing the hydrate formed in an aqueous solution.

  5. Item 3. A method for removing phosphorus, comprising treating phosphorus-containing wastewater using the phosphorus adsorbent according to Item 2.

  According to the present invention, an inexpensive iron sulfate raw material can be used to obtain a phosphorus adsorbent having high phosphorus adsorption ability.

  The phosphorus adsorbent of the present invention can efficiently adsorb and remove phosphorus even in high-salt phosphorus-containing wastewater such as seawater.

In the present specification, as the phosphorus adsorbent, the following general formula (1):
Fe (OH) _m (SO ₄ ) _n · lH ₂ O (1)
(In the formula, 2 ≦ m <3, 0 <n ≦ 0.5, 0 ≦ l ≦ 0.5.)
And the hydrates formed in aqueous solutions can be used.

  m is 2 or more and less than 3, preferably 2.2 to 2.8, more preferably 2.5 to 2.7, and particularly preferably about 2.6.

n is larger than 0 and 0.5 or less, preferably 0.1 to 0.4, more preferably 0.15 to 0.25, and particularly preferably about 0.2.
l is 0 or more and 0.5 or less, preferably 0 to 0.4, more preferably 0.05 to 0.20, and particularly preferably about 0.1.

  A compound of the general formula (1) in which m is about 2.6 and n is about 0.20 is particularly preferable because of its excellent phosphorus adsorption ability.

  In the present specification, preferred examples of phosphorus adsorbed include phosphoric acid and phosphoric acid dissociated products, but phosphorous acid or ions thereof can also be adsorbed.

  Examples of phosphorus adsorption targets include phosphorus-containing aqueous solutions such as phosphorus-containing wastewater. The aqueous solution may be an aqueous solution containing a large amount of salts such as seawater. The phosphorus adsorbent of the present invention can effectively adsorb and remove phosphorus even when the salt concentration is high. The pH of the aqueous solution is not particularly limited, but is usually about 2 to 9, preferably about 3 to 8.5, more preferably about 4 to 8, and particularly preferably about 4.5 to 7.5. When carrying out phosphorus adsorption, the pH of the phosphorus removal target aqueous solution can be adjusted as necessary.

The compound of the general formula (1) is prepared by preparing a mixed aqueous solution containing, for example, FeSO ₄ and Fe ₂ (SO ₄ ) _3, and adjusting the pH of the aqueous solution to neutral to alkaline by adding a base with stirring or shaking. It can be obtained by precipitating the compound of the general formula (1) having adsorption performance, filtering and drying.

Mixing an aqueous solution containing FeSO ₄ and Fe ₂ (SO _{4) 3,} for example also solid FeSO ₄ and Fe ₂ (SO _{4) 3} (which may be respectively hydrate or anhydride) dissolved in water It is also possible to prepare by mixing each aqueous solution. It may also prepared using double salt of FeSO ₄ and Fe ₂ (SO ₄₎ one or FeSO ₄ in the presence or absence of both ₃ and Fe ₂ (SO _{4) 3.} The ratio (molar ratio) between Fe ²⁺ and Fe ^{3+ in} the mixed aqueous solution is as follows: Fe ²⁺ : Fe ³⁺ = 0.98 to 0.02 mol: 0.02 to 0.98 mol, preferably 0.98 to About 0.5 mol: about 0.02 to 0.5 mol, more preferably about Fe ²⁺ : Fe ³⁺ = about 0.95 to 0.7 mol: about 0.05 to 0.3 mol.

The present invention is characterized in that a compound of the general formula (1) is obtained by using a combination of FeSO ₄ and Fe ₂ (SO ₄ ) ₃ , and the obtained compound of the general formula (1) is excellent. Has phosphorus adsorption capacity. In particular, a compound represented by the formula: Fe (OH) _2.5 (SO ₄ ) _0.25 is preferable because of its excellent phosphorus adsorption ability.

Preferred examples of the base for making the aqueous solution containing FeSO ₄ and Fe ₂ (SO ₄ ) ₃ neutral to alkaline include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide.

  The pH of the aqueous solution when the base is added is usually about 6.5 to 13, preferably about 6.8 to 11, more preferably about 7.0 to 10, and further preferably about 7.0 to 8.0. . The alkali is added for the purpose of precipitating the compound having the phosphate adsorption ability of the present invention. The obtained precipitate can be obtained by filtration, washing and drying.

  The phosphorus adsorbent of the present invention can be subjected to operations such as granulation to form a molded body, filled in a column or the like, and phosphorus can be adsorbed or recovered by flowing waste water containing phosphorus through the column.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples.
Example 1
0.5 M FeSO ₄ (200 mL) and 0.1 M Fe ₂ (SO ₄ ) ₃ (200 mL) were mixed, and 1 M NaOH was added with stirring to adjust the pH to 7-8. The resulting precipitate was filtered, washed with deionized water and dried to obtain a compound represented by Fe (OH) _2.6 (SO ₄ ) _0.2 · 0.1H ₂ O. The chemical formula of the obtained compound was confirmed by dissolving in water content and 5N hydrochloric acid from DTA-TG measurement, and quantifying the Fe content by atomic absorption method and sulfate ion by pressurized hot water extraction / ion chromatography.

Further, an XRD adsorption pattern of a compound represented by Fe (OH) _2.6 (SO ₄ ) _0.2 · 0.1H ₂ O is shown in FIG. 1, and a DTA-TG curve is shown in FIG. Furthermore, the FT-IR spectrum is shown in FIG.
Comparative Example 1
To 0.1M FeCl ₃ (500 mL), 0.1M NaOH (500 mL) was added with stirring to adjust the pH to 8-10. The resulting precipitate was filtered, washed with deionized water and dried to obtain a compound represented by Fe (OH) ₃ .

The XRD adsorption pattern of the obtained compound represented by Fe (OH) ₃ is shown in FIG. 1, and the DTA-TG curve is shown in FIG. Furthermore, the FT-IR spectrum is shown in FIG.
Test example 1
Using 0.05 g of the phosphorus adsorbent composed of the iron compound obtained in Example 1 and Comparative Example 1, the amount of phosphorus adsorbed from an aqueous solution containing 0.33 mg-P / g phosphoric acid in 2 L of seawater was measured. The results are shown in FIG.

  Moreover, the pH dependence of the pH phosphorus adsorption capacity of the phosphorus adsorbent comprising the iron compound obtained in Example 1 is shown in FIG. 5, and the phosphorus adsorbent comprising the iron compound obtained in Example 1 and Comparative Example 1 The adsorption isotherm is shown in FIG.

The XRD pattern of an adsorbent is shown. The DTA-TG curve of an adsorbent is shown. The FT-IR spectrum of the adsorbent is shown. The time dependence of the adsorption of phosphoric acid by the adsorbent is shown. The pH dependence of the adsorption of phosphate by the adsorbent is shown. The adsorption isotherm of the phosphoric acid from the seawater about an adsorbent is shown.

Claims (5)

The active ingredient is the formula:
Fe (OH) _2.6 (SO ₄ ) _0.2
And the hydrates formed in aqueous solution The active ingredient is general formula (1):
Fe (OH) _m (SO ₄ ) _n (1)
(Wherein 2 ≦ m <3 and 0 <n ≦ 0.5)
And a hydrate formed in an aqueous solution. General formula (1):
Fe (OH) _m (SO ₄ ) _n (1)
(Wherein 2 ≦ m <3 and 0 <n ≦ 0.5)
And the use for adsorption of phosphorus of the hydrate formed in an aqueous solution. General formula (1) characterized in that a base is added to a mixed aqueous solution containing FeSO ₄ and Fe ₂ (SO ₄ ) ₃ to produce a precipitate from neutral to alkaline:
Fe (OH) _m (SO ₄ ) _n (1)
(Wherein 2 ≦ m <3 and 0 <n ≦ 0.5)
And a method for producing the hydrate formed in an aqueous solution. A method for removing phosphorus, comprising treating phosphorus-containing wastewater using the phosphorus adsorbent according to claim 2.

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