JP6989840B2 - Phosphoric acid recovery method - Google Patents
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- JP6989840B2 JP6989840B2 JP2017128613A JP2017128613A JP6989840B2 JP 6989840 B2 JP6989840 B2 JP 6989840B2 JP 2017128613 A JP2017128613 A JP 2017128613A JP 2017128613 A JP2017128613 A JP 2017128613A JP 6989840 B2 JP6989840 B2 JP 6989840B2
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims description 104
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims description 53
- 238000000034 method Methods 0.000 title claims description 30
- 238000011084 recovery Methods 0.000 title claims description 20
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 59
- 229910019142 PO4 Inorganic materials 0.000 claims description 46
- 239000010452 phosphate Substances 0.000 claims description 46
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 45
- 239000007864 aqueous solution Substances 0.000 claims description 32
- 239000003463 adsorbent Substances 0.000 claims description 29
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 25
- 239000000243 solution Substances 0.000 claims description 20
- 238000001816 cooling Methods 0.000 claims description 7
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 6
- 229940085991 phosphate ion Drugs 0.000 claims description 6
- -1 phosphoric acid ions Chemical class 0.000 claims description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims description 6
- 239000011574 phosphorus Substances 0.000 claims description 6
- CUPCBVUMRUSXIU-UHFFFAOYSA-N [Fe].OOO Chemical compound [Fe].OOO CUPCBVUMRUSXIU-UHFFFAOYSA-N 0.000 claims description 4
- 229910021519 iron(III) oxide-hydroxide Inorganic materials 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 2
- 150000002500 ions Chemical class 0.000 claims 1
- 239000007788 liquid Substances 0.000 description 15
- 239000001488 sodium phosphate Substances 0.000 description 15
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 15
- 235000011121 sodium hydroxide Nutrition 0.000 description 14
- 238000003795 desorption Methods 0.000 description 12
- 239000013078 crystal Substances 0.000 description 9
- 229910000406 trisodium phosphate Inorganic materials 0.000 description 9
- 235000019801 trisodium phosphate Nutrition 0.000 description 9
- 229910044991 metal oxide Inorganic materials 0.000 description 8
- 150000004706 metal oxides Chemical class 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 229910052783 alkali metal Inorganic materials 0.000 description 6
- 238000002425 crystallisation Methods 0.000 description 6
- 230000008025 crystallization Effects 0.000 description 6
- 229910000162 sodium phosphate Inorganic materials 0.000 description 6
- 235000011008 sodium phosphates Nutrition 0.000 description 6
- 150000003839 salts Chemical class 0.000 description 5
- 229920006395 saturated elastomer Polymers 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 229910001413 alkali metal ion Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- CPRMKOQKXYSDML-UHFFFAOYSA-M rubidium hydroxide Chemical compound [OH-].[Rb+] CPRMKOQKXYSDML-UHFFFAOYSA-M 0.000 description 2
- 239000010865 sewage Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- MFGOFGRYDNHJTA-UHFFFAOYSA-N 2-amino-1-(2-fluorophenyl)ethanol Chemical compound NCC(O)C1=CC=CC=C1F MFGOFGRYDNHJTA-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- MXZRMHIULZDAKC-UHFFFAOYSA-L ammonium magnesium phosphate Chemical compound [NH4+].[Mg+2].[O-]P([O-])([O-])=O MXZRMHIULZDAKC-UHFFFAOYSA-L 0.000 description 1
- HUCVOHYBFXVBRW-UHFFFAOYSA-M caesium hydroxide Inorganic materials [OH-].[Cs+] HUCVOHYBFXVBRW-UHFFFAOYSA-M 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
- 229910000389 calcium phosphate Inorganic materials 0.000 description 1
- 235000011010 calcium phosphates Nutrition 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000033444 hydroxylation Effects 0.000 description 1
- 238000005805 hydroxylation reaction Methods 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000010842 industrial wastewater Substances 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 229910021518 metal oxyhydroxide Inorganic materials 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 description 1
- 150000003018 phosphorus compounds Chemical class 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000010801 sewage sludge Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052567 struvite Inorganic materials 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
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- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Description
本発明は、リン酸吸着材を用いてリン酸を回収する方法に関し、特にリン酸をアルカリ金属塩として回収する方法に関する。 The present invention relates to a method for recovering phosphoric acid using a phosphoric acid adsorbent, and more particularly to a method for recovering phosphoric acid as an alkali metal salt.
汚水や工業廃水に多量のリンや窒素が含まれると、富栄養化の原因となるため、このような汚水を排出することは環境に好ましくなく、適切な廃水処理が必要とされている。
リンは肥料成分として、また化学工業にも不可欠の成分であるが、日本においてはほぼ１００％を輸入に頼っており、世界的にもリン鉱石の産出国が限定されるため、その他のリン源が求められている。
以上の諸問題を解決するために、廃水中に含まれるリン酸等のリン化合物の除去及び回収が注目されている。
If a large amount of phosphorus or nitrogen is contained in sewage or industrial wastewater, it causes eutrophication. Therefore, it is not preferable for the environment to discharge such sewage, and appropriate wastewater treatment is required.
Phosphorus is an indispensable component for the chemical industry as well as a fertilizer component, but in Japan, almost 100% of it depends on imports, and the countries that produce phosphate ore are limited worldwide, so other sources of phosphorus. Is required.
In order to solve the above problems, attention is being paid to the removal and recovery of phosphorus compounds such as phosphoric acid contained in wastewater.
リン酸又はその塩を回収する方法としては、重金属等の不要又は有害な物質を含まず純度の高いリン酸又はその塩が得られることから、リン酸吸着材を用いる方法が優れている。例えば、特許文献１～４等には、リン酸を特に高効率で吸着するオキシ水酸化鉄系吸着材が記載されている。これらのリン酸吸着材からは、アルカリ性水溶液によりリン酸を脱着することが可能である。
またリン酸は、リン酸カルシウムあるいはリン酸マグネシウムアンモニウムといった難水溶性化合物として回収されることがこれまで一般的であったが、その後の工業的利用にはリン酸ナトリウム等のアルカリ金属塩の方が適している。
As a method for recovering phosphoric acid or a salt thereof, a method using a phosphoric acid adsorbent is excellent because high-purity phosphoric acid or a salt thereof can be obtained without containing unnecessary or harmful substances such as heavy metals. For example, Patent Documents 1 to 4 and the like describe iron oxyhydroxide-based adsorbents that adsorb phosphoric acid with particularly high efficiency. Phosphoric acid can be desorbed from these phosphoric acid adsorbents with an alkaline aqueous solution.
In addition, phosphoric acid has been generally recovered as a poorly water-soluble compound such as calcium phosphate or magnesium ammonium phosphate, but alkali metal salts such as sodium phosphate are more suitable for subsequent industrial use. ing.
特許文献５には、下水汚泥焼却灰から酸によって抽出したリン酸溶液から、リン酸分を金属水和酸化物に吸着させ、次いでこの金属水和酸化物からリン酸イオンをアルカリ溶液に移行させ回収する方法が記載されている。具体的には、ジルコニウム鉄水和酸化物からなる吸着材を用い、１％水酸化ナトリウム水溶液を用いて３５℃で脱着を行い、脱着液を１５℃に冷却してリン酸三ナトリウムを析出させている。また析出後の水酸化ナトリウム溶液に、適当量の水酸化ナトリウムを補充して脱着に再利用することも記載されている。
特許文献６には、排水に由来するリン酸をジルコニウムフェライト系吸着材に吸着させ、７％水酸化ナトリウムでリン酸を脱着させ、析出により回収する方法が記載されている。析出工程では脱着液を加温し水分の一部を蒸発させる方法をとっており、これは多量のエネルギー消費を要する。
特許文献７には、リン酸ソーダ含有廃液をｐＨ４以上にした後、冷却晶析してリン酸ソーダ含水結晶を分離する、リン酸ソーダの回収方法が記載されている。例として、リン酸ソーダ廃液を苛性ソーダでｐＨ１２．５に調整し、該液を約７℃に冷却し、高純度結晶を得るために、第三リン酸ソーダ・１２水塩の種結晶を添加して撹拌した後、一昼夜放置して析出した結晶を回収している（実施例３）。
In Patent Document 5, a phosphoric acid component is adsorbed on a metal hydrated oxide from a phosphoric acid solution extracted from sewage sludge incineration ash with an acid, and then phosphoric acid ions are transferred from this metal hydrated oxide to an alkaline solution. The method of recovery is described. Specifically, using an adsorbent made of zirconium iron hydrate, desorption is performed at 35 ° C using a 1% aqueous sodium hydroxide solution, and the desorbed solution is cooled to 15 ° C to precipitate trisodium phosphate. ing. It is also described that the sodium hydroxide solution after precipitation is supplemented with an appropriate amount of sodium hydroxide and reused for desorption.
Patent Document 6 describes a method of adsorbing phosphoric acid derived from wastewater on a zirconium ferritic adsorbent, desorbing phosphoric acid with 7% sodium hydroxide, and recovering by precipitation. In the precipitation step, a method of heating the desorption liquid to evaporate a part of the water is adopted, which requires a large amount of energy consumption.
Patent Document 7 describes a method for recovering sodium phosphate, in which a waste liquid containing sodium phosphate is adjusted to pH 4 or higher and then cooled and crystallized to separate sodium phosphate-containing crystals. As an example, the sodium phosphate waste liquid is adjusted to pH 12.5 with caustic soda, the liquid is cooled to about 7 ° C., and seed crystals of sodium phosphate 12 hydroxide are added to obtain high-purity crystals. After stirring, the crystals were left for a whole day and night to recover the precipitated crystals (Example 3).
本発明の課題は、リン酸吸着材によってリン酸を吸着させ、さらに高効率で高品位のリン酸分を回収する方法を提供することである。 An object of the present invention is to provide a method for adsorbing phosphoric acid with a phosphoric acid adsorbent and recovering a high-quality phosphoric acid content with high efficiency.
本発明者は、リン酸吸着材を用い、リン酸をアルカリ金属塩として高効率で回収する方法を鋭意検討した。そして、特定のリン酸吸着材を用い、脱着用のアルカリ水溶液をこれまで知られたものより高濃度にして使用すると、冷却によるリン酸塩の回収効率が劇的に向上して、種結晶の使用や、別法でのリン酸回収は不要となり、しかもリン酸塩除去後のアルカリ溶液をそのまま再度脱着に利用でき、経済的にも優れた方法となることを見出し、本発明を完成した。 The present inventor has diligently studied a method for recovering phosphoric acid as an alkali metal salt with high efficiency by using a phosphoric acid adsorbent. Then, when a specific phosphoric acid adsorbent is used and the desorption alkaline aqueous solution is used at a higher concentration than previously known, the recovery efficiency of the phosphate by cooling is dramatically improved, and the seed crystal is used. The present invention has been completed by finding that it does not require use or recovery of phosphoric acid by another method, and that the alkaline solution after removing the phosphate can be used for desorption again as it is, which is an economically excellent method.
すなわち本発明は、
（１）少なくとも、
（Ａ）リン酸イオンを吸着したリン酸吸着材を、３０℃以上で３質量％以上のアルカリ金属水酸化物水溶液と接触させ、当該リン酸イオンをリン酸塩水溶液として脱着させる工程、及び
（Ｂ）工程（Ａ）で得られたリン酸塩水溶液を１５℃以下に冷却することによりリン酸塩を晶出させ、当該リン酸塩と、リン酸濃度が１質量％以下であるアルカリ金属水酸化物水溶液とを回収する工程、
の両工程を有する、リン酸塩回収方法、
（２）前記アルカリ金属水酸化物水溶液の濃度が６質量％以下であることを特徴とする、（１）に記載のリン酸塩回収方法、
（３）前記アルカリ金属水酸化物が水酸化ナトリウムであることを特徴とする、（１）又は（２）に記載のリン酸塩回収方法、
（４）リン酸吸着材が、無機系吸着材であることを特徴とする、（１）～（３）のいずれかに記載のリン酸塩回収方法、及び、
（５）（１）～（４）のいずれかに記載のリン酸塩回収方法であって、前記工程（Ｂ）の後に、
（Ａ’）工程（Ａ）における３質量％以上のアルカリ金属水酸化物水溶液に代えて、工程（Ｂ）で得られたリン酸濃度が１質量％以下であるアルカリ金属水酸化物水溶液を用い、リン酸イオンをリン酸塩水溶液として脱着させる工程、及び工程（Ｂ）をこの順に実施することを特徴とする、リン酸塩回収方法。
That is, the present invention
(1) At least
(A) A step of bringing the phosphate adsorbent adsorbing phosphate ions into contact with an alkali metal hydroxide aqueous solution of 3% by mass or more at 30 ° C. or higher, and desorbing the phosphate ions as a phosphate aqueous solution, and ( B) The phosphate aqueous solution obtained in the step (A) is cooled to 15 ° C. or lower to crystallize the phosphate, and the phosphate and the alkali metal water having a phosphate concentration of 1% by mass or less. The process of recovering the oxide aqueous solution,
Phosphate recovery method, which has both steps of
(2) The phosphate recovery method according to (1), wherein the concentration of the aqueous alkali metal hydroxide solution is 6% by mass or less.
(3) The phosphate recovery method according to (1) or (2), wherein the alkali metal hydroxide is sodium hydroxide.
(4) The phosphate recovery method according to any one of (1) to (3), wherein the phosphoric acid adsorbent is an inorganic adsorbent.
(5) The phosphate recovery method according to any one of (1) to (4), after the step (B).
(A') Instead of the alkali metal hydroxide aqueous solution of 3% by mass or more in the step (A), an alkali metal hydroxide aqueous solution having a phosphate concentration of 1% by mass or less obtained in the step (B) is used. , A method for recovering a phosphate, comprising a step of desorbing a phosphate ion as a phosphate aqueous solution and a step (B) in this order.
本発明により、高品位のリン酸塩を経済的に回収することが可能となった。 INDUSTRIAL APPLICABILITY According to the present invention, it has become possible to economically recover high-grade phosphate.
本発明の方法は、少なくとも、
（Ａ）リン酸イオンを吸着したリン酸吸着材を、３０℃以上で３質量％以上のアルカリ金属水酸化物水溶液と接触させ、当該リン酸イオンをリン酸塩水溶液として脱着させる工程、及び
（Ｂ）工程（Ａ）で得られたリン酸塩水溶液を１５℃以下に冷却することによりリン酸塩を晶出させ、当該リン酸塩と、リン酸濃度が１質量％以下であるアルカリ金属水酸化物水溶液とを回収する工程、
の両工程を有する、リン酸塩回収方法である。
The method of the present invention is at least
(A) A step of bringing the phosphate adsorbent adsorbing phosphate ions into contact with an alkali metal hydroxide aqueous solution of 3% by mass or more at 30 ° C. or higher, and desorbing the phosphate ions as a phosphate aqueous solution, and ( B) The phosphate aqueous solution obtained in the step (A) is cooled to 15 ° C. or lower to crystallize the phosphate, and the phosphate and the alkali metal water having a phosphate concentration of 1% by mass or less. The process of recovering the oxide aqueous solution,
It is a phosphate recovery method having both steps of.
本発明に用いられるリン酸吸着材は、特に限定されるものではなく、３０℃以上で３質量％以上のアルカリ金属水酸化物水溶液に耐えるものであればよい。
このようなリン酸吸着材としては、無機系吸着材（無機化合物をリン酸吸着成分として含有する吸着材。）が好ましい。特に、金属酸化物系吸着材（金属酸化物、金属水酸化物、金属オキシ水酸化物を包含する金属酸化物系成分をリン酸吸着成分として含有する吸着材。）が好ましい。金属酸化物系吸着材は、金属酸化物系成分を主成分とするか、またはリン酸イオンを吸着する金属酸化物系吸着材をリン酸吸着成分として含有し、補助成分として結着剤及び／又は担体を含有する吸着材であることが好ましい。
吸着成分の具体例としては、酸化鉄、水酸化鉄、オキシ水酸化鉄、活性アルミナ、酸化チタン、酸化ジルコニウム、酸化セリウム等が挙げられ、これらの成分から選ばれる２種以上を併用してもよい。この中で、オキシ水酸化鉄が好ましい。
金属酸化物系成分を主成分とする場合には、金属酸化物系成分の含有量は、９９質量％以上であることが好ましく、実質的に１００質量％であることがより好ましい。
結着剤及び／又は担体としては、水不溶性であり、３０℃以上で３質量％以上のアルカリ金属水酸化物水溶液に耐える、無機成分、若しくはポリオレフィン系成分が好ましい。
The phosphoric acid adsorbent used in the present invention is not particularly limited as long as it can withstand an alkali metal hydroxide aqueous solution of 3% by mass or more at 30 ° C. or higher.
As such a phosphoric acid adsorbent, an inorganic adsorbent (an adsorbent containing an inorganic compound as a phosphoric acid adsorbent component) is preferable. In particular, a metal oxide-based adsorbent (an adsorbent containing a metal oxide-based component including a metal oxide, a metal hydroxide, and a metal oxyhydroxide as a phosphoric acid adsorbing component) is preferable. The metal oxide-based adsorbent contains a metal oxide-based adsorbent as a main component or a metal oxide-based adsorbent that adsorbs phosphate ions as a phosphoric acid adsorbent, and as an auxiliary component, a binder and / Alternatively, it is preferably an adsorbent containing a carrier.
Specific examples of the adsorbed component include iron oxide, iron hydroxide, iron oxyhydroxide, activated alumina, titanium oxide, zirconium oxide, cerium oxide and the like, and even if two or more kinds selected from these components are used in combination. good. Of these, iron oxyhydroxide is preferable.
When the metal oxide-based component is the main component, the content of the metal oxide-based component is preferably 99% by mass or more, and more preferably substantially 100% by mass.
As the binder and / or carrier, an inorganic component or a polyolefin-based component that is water-insoluble and can withstand an alkali metal hydroxide aqueous solution of 3% by mass or more at 30 ° C. or higher is preferable.
工程（Ａ）におけるリン酸イオンの脱着温度は、３０℃以上とすることにより、脱着が促進され、またリン酸の溶解度が高いため途中で晶析する恐れなく使用することができる。この温度は３５～７０℃とすることがさらに好ましい。 By setting the desorption temperature of the phosphate ion in the step (A) to 30 ° C. or higher, desorption is promoted, and since the solubility of phosphoric acid is high, it can be used without fear of crystallization in the middle. This temperature is more preferably 35 to 70 ° C.
工程（Ａ）におけるリン酸イオンの脱着には、アルカリ金属水酸化物の水溶液を用いる。
一般にこのような脱着には、アルカリ性水溶液を使用することが可能であり、特にｐＨ１３以上であることが好ましい。アンモニア水やアルカリ土類金属水酸化物の水溶液を用いることも想定し得るが、アンモニア水はｐＨ１３以上にすることが困難であり、また高温で高濃度にすることが困難であるため脱着効率が低く、アルカリ土類金属水酸化物はリン酸イオンと反応して工程（Ａ）の途中で水難溶性塩が析出する恐れが大きい。アルカリ金属水酸化物水溶液を用いればこのようなことがなく、高温で高濃度の水溶液として使用することが可能である。
アルカリ金属水酸化物としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウム、水酸化ルビジウム、水酸化セシウム等が挙げられ、このうちで水酸化ナトリウムが好ましい。
An aqueous solution of an alkali metal hydroxide is used for the desorption of phosphate ions in the step (A).
Generally, it is possible to use an alkaline aqueous solution for such desorption, and it is particularly preferable that the pH is 13 or higher. It is conceivable to use aqueous solution of ammonia water or alkaline earth metal hydroxide, but it is difficult to make the pH of ammonia water 13 or higher, and it is difficult to make it high in concentration at high temperature, so the desorption efficiency is high. It is low, and there is a high possibility that the alkaline earth metal hydroxide reacts with the phosphate ion to precipitate a poorly water-soluble salt in the middle of the step (A). If an aqueous alkali metal hydroxide solution is used, this does not occur, and it can be used as a high-concentration aqueous solution at a high temperature.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and the like, of which sodium hydroxide is preferable.
工程（Ｂ）におけるリン酸塩晶出のための冷却温度は、１５℃以下、好ましくは５～１０℃にすることにより、高効率でリン酸塩を晶出させ、溶液中に残存するリン酸濃度を低くすることができる。特に、残存リン酸濃度を１質量％以下とすることができ、晶出したリン酸塩と分離して得られる液分をそのまま後述の工程（Ａ’）に用いることができる。残存リン酸濃度は、０．５質量％以下とすることが好ましい。
工程（Ｂ）では、撹拌により温度を均一にしながら、リン酸塩を晶出させることが好ましい。また冷却時間は２４時間以内とすることが効率面で好ましい。なお、結晶の粒度を調整する等の必要があれば、晶出開始前にリン酸塩の種結晶を加えることもできるが、本発明ではリン酸吸着材からの高純度の脱着液をリン酸塩原料液として使用しているため、不要成分を多量に含有する原料液を用いる場合のように、純度を高める目的で種結晶を使用する必要は特にない。
By setting the cooling temperature for phosphate crystallization in step (B) to 15 ° C or lower, preferably 5 to 10 ° C, phosphate is crystallized with high efficiency, and phosphoric acid remaining in the solution. The concentration can be lowered. In particular, the residual phosphoric acid concentration can be 1% by mass or less, and the liquid component obtained by separating from the crystallized phosphate can be used as it is in the step (A') described later. The residual phosphoric acid concentration is preferably 0.5% by mass or less.
In the step (B), it is preferable to crystallize the phosphate while making the temperature uniform by stirring. Further, it is preferable that the cooling time is within 24 hours in terms of efficiency. If it is necessary to adjust the particle size of the crystal, a seed crystal of phosphate can be added before the start of crystallization, but in the present invention, a high-purity desorbing solution from the phosphoric acid adsorbent is phosphoric acid. Since it is used as a salt raw material liquid, it is not particularly necessary to use seed crystals for the purpose of increasing the purity as in the case of using a raw material liquid containing a large amount of unnecessary components.
工程（Ａ）に用いるアルカリ金属水酸化物水溶液濃度は、３質量％以上とすることにより、工程（Ｂ）における冷却条件でのリン酸の飽和溶解度が特に低くなるため、リン酸塩の晶出効率を高めることができる。アルカリ金属水酸化物水溶液濃度は４質量％以上であることが好ましい。
一方、アルカリ金属水酸化物水溶液濃度を過度に高くすると、３０℃以上の高温であってもリン酸の飽和溶解度が低くなる。これを避けることにより、工程（Ａ）及び（Ｂ）におけるリン酸溶解度差を大きく、すなわちリン酸回収効率を高くすることができる。具体的には、工程（Ａ）は、リン酸の飽和溶解度が２質量％以上である条件で行うことが好ましい。このためには、アルカリ金属水酸化物水溶液濃度が１０質量％以下であることが好ましく、６質量％以下であることがより好ましい。
特に、工程（Ａ）及び工程（Ｂ）の条件におけるリン酸の飽和溶解度（各ＣＡ、ＣＢ）の比ＣＢ／ＣＡは、アルカリ金属水酸化物水溶液濃度が５質量％付近で最低値となり、冷却による回収効率が最高となる。この比は０．２以下であることが好ましく、０．１５以下であることがより好ましい。
By setting the concentration of the aqueous alkali metal hydroxide solution used in the step (A) to 3% by mass or more, the saturated solubility of phosphoric acid under the cooling conditions in the step (B) becomes particularly low, so that the crystallization of the phosphate is performed. Efficiency can be increased. The concentration of the aqueous alkali metal hydroxide solution is preferably 4% by mass or more.
On the other hand, if the concentration of the aqueous alkali metal hydroxide solution is excessively high, the saturated solubility of phosphoric acid becomes low even at a high temperature of 30 ° C. or higher. By avoiding this, the difference in phosphoric acid solubility in the steps (A) and (B) can be increased, that is, the phosphoric acid recovery efficiency can be increased. Specifically, the step (A) is preferably performed under the condition that the saturated solubility of phosphoric acid is 2% by mass or more. For this purpose, the concentration of the aqueous alkali metal hydroxide solution is preferably 10% by mass or less, more preferably 6% by mass or less.
In particular, the ratio C B / CA of the saturated solubility of phosphoric acid (each CA, C B ) under the conditions of step ( A ) and step ( B ) is the lowest when the concentration of the aqueous alkali metal hydroxide solution is around 5% by mass. It becomes a value, and the recovery efficiency by cooling becomes the highest. This ratio is preferably 0.2 or less, more preferably 0.15 or less.
工程（Ｂ）では、リン酸塩の晶出に続き、晶出したリン酸塩と液分とに分離する。これには、沈殿、ろ過等の公知の方法を使用することができる。ここで液分に含有されるリン酸濃度は１質量％以下である。この液分は、後述の工程（Ａ’）に再使用することが好ましいが、必要に応じ中和、濃縮、希釈等の工程を経て、さらに他の工程に用いるか、若しくは環境・安全上の問題がなければ廃棄することもできる。 In the step (B), the crystallization of the phosphate is followed by separation into the crystallization phosphate and the liquid component. For this, known methods such as precipitation and filtration can be used. Here, the concentration of phosphoric acid contained in the liquid content is 1% by mass or less. It is preferable to reuse this liquid in the step (A') described later, but if necessary, it may be used for other steps after undergoing steps such as neutralization, concentration and dilution, or for environmental and safety reasons. If there is no problem, it can be discarded.
本発明では、工程（Ｂ）の後に、工程（Ａ’）及び工程（Ｂ）を行うことが好ましく、この工程（Ａ’）及び工程（Ｂ）を複数回反復することがさらに好ましい。
工程（Ａ’）とは、脱着液として、工程（Ａ）における３質量％以上のアルカリ金属水酸化物水溶液の代わりに、工程（Ｂ）で得られたリン酸濃度が１質量％以下であるアルカリ金属水酸化物水溶液を用い、リン酸イオンをリン酸塩水溶液として脱着させる工程である。
ここで、工程（Ｂ）で得られたリン酸濃度が１質量％以下であるアルカリ金属水酸化物水溶液に含有されるアルカリ金属イオン（リン酸塩を含む。）の濃度は、アルカリ金属水酸化物に換算して、３質量％以上であることが好ましく、４質量％以上であることがより好ましく、また６質量％以下であることが好ましい。
工程（Ｂ）ではリン酸塩として一部のアルカリ金属イオンが除かれているため、その後の工程（Ａ’）に使用する脱着液としてはアルカリ金属イオンが不足している場合がある。この場合には、脱着液にアルカリ金属水酸化物を補充し、好ましくはアルカリ金属イオンの濃度を上記範囲に調整して、工程（Ａ’）を行ってもよい。
In the present invention, it is preferable to carry out the step (A') and the step (B) after the step (B), and it is more preferable to repeat the step (A') and the step (B) a plurality of times.
In the step (A'), the phosphoric acid concentration obtained in the step (B) is 1% by mass or less as the desorption liquid instead of the alkali metal hydroxide aqueous solution of 3% by mass or more in the step (A). This is a step of desorbing phosphate ions as a phosphate aqueous solution using an alkali metal hydroxide aqueous solution.
Here, the concentration of the alkali metal ion (including the phosphate) contained in the alkali metal hydroxide aqueous solution having the phosphoric acid concentration of 1% by mass or less obtained in the step (B) is alkali metal hydroxylation. In terms of a substance, it is preferably 3% by mass or more, more preferably 4% by mass or more, and preferably 6% by mass or less.
Since some alkali metal ions are removed as the phosphate in the step (B), the alkali metal ions may be insufficient as the desorption liquid used in the subsequent step (A'). In this case, the desorbing solution may be supplemented with an alkali metal hydroxide, preferably the concentration of the alkali metal ion may be adjusted to the above range, and the step (A') may be performed.
次に、本発明の実施例によってさらに詳細に説明するが、本発明はこれにより限定されるものではない。 Next, the present invention will be described in more detail by way of examples of the present invention, but the present invention is not limited thereto.
（参考例１）
純水に水酸化ナトリウムを溶解し、所定濃度の水酸化ナトリウム水溶液を作製した。各水酸化ナトリウムを、温度を４０℃（工程（Ａ）の条件として想定）及び１０℃（工程（Ｂ）の条件として想定）に調整しながら撹拌し、リン酸三ナトリウム１２水塩を過剰量添加してさらに２時間撹拌した。その後各温度で静置し、上清を採取して適宜希釈し、パックテスト（共立理化学研究所製）でリン酸イオン濃度を測定し、飽和リン酸イオン濃度を求めた（各条件２連）。各条件での平均値を表１に示した。
(Reference example 1)
Sodium hydroxide was dissolved in pure water to prepare a sodium hydroxide aqueous solution having a predetermined concentration. Stir each sodium hydroxide while adjusting the temperature to 40 ° C. (assumed as the condition of step (A)) and 10 ° C. (assumed as the condition of step (B)), and add an excess amount of trisodium phosphate 12 hydroxide. The mixture was added and stirred for another 2 hours. After that, the mixture was allowed to stand at each temperature, the supernatant was collected, diluted appropriately, and the phosphate ion concentration was measured by a pack test (manufactured by Kyoritsu Rikagaku Kenkyusho) to determine the saturated phosphate ion concentration (two stations under each condition). .. Table 1 shows the average value under each condition.
以上から、１０℃及び４０℃におけるリン酸の飽和溶解度（各Ｃ１０、Ｃ４０）の比Ｃ１０／Ｃ４０は、水酸化ナトリウム水溶液濃度が５質量％付近で最低値となり、冷却による回収効率が最高となると考えられる。 From the above, the ratio C 10 / C 40 of the saturated solubility of phosphoric acid (C 10 , C 40 , respectively) at 10 ° C and 40 ° C is the lowest value when the sodium hydroxide aqueous solution concentration is around 5% by mass, and the recovery efficiency by cooling is achieved. Is considered to be the best.
（実施例１）
純水に水酸化ナトリウムを溶解し、５質量％水酸化ナトリウム水溶液を作製した。この水溶液５００ｍＬに、リン酸三ナトリウム１２水塩８０．１ｇを添加し、撹拌しながら加温して液温を４０℃に調整し、完全に溶解したことを確認した。これを撹拌しながら液温低下速度を１０℃／時間として３時間、１０℃まで冷却した。これを減圧濾過して析出物と濾液とに分離した。濾液におけるリン酸濃度（下記方法によりリンを定量しリン酸濃度に換算した。）は０．５０６質量％であった。
濾別した析出物に、過剰のアルカリ分を除去するため、２～３℃に調整した純水約１００ｍＬを加えて減圧濾過し洗浄した。洗浄した析出物からエバポレーターにより水分を除去し、リン酸三ナトリウムを回収した。
以上により分離された濾液、洗液、及び回収されたリン酸三ナトリウムを、適宜希釈又は溶解し、含有されるリンをＩＣＰ（誘導結合プラズマ）発光分光法により定量し、仕込量（リン酸三ナトリウム１２水塩８０．１ｇ）に対する回収率として算出した結果は、以下の通りであった。
濾液：１２．０％
洗液：１２．５％
リン酸三ナトリウム：７３．７％
(Example 1)
Sodium hydroxide was dissolved in pure water to prepare a 5% by mass sodium hydroxide aqueous solution. To 500 mL of this aqueous solution, 80.1 g of trisodium phosphate 12 water salt was added, and the mixture was heated with stirring to adjust the liquid temperature to 40 ° C., and it was confirmed that the solution was completely dissolved. While stirring this, the liquid temperature was cooled to 10 ° C. for 3 hours at a liquid temperature decrease rate of 10 ° C./hour. This was filtered under reduced pressure and separated into a precipitate and a filtrate. The phosphoric acid concentration in the filtrate (phosphorus was quantified by the following method and converted into a phosphoric acid concentration) was 0.506% by mass.
In order to remove excess alkaline content from the separated precipitate, about 100 mL of pure water adjusted to 2 to 3 ° C. was added, and the mixture was filtered under reduced pressure and washed. Moisture was removed from the washed precipitate by an evaporator, and trisodium phosphate was recovered.
The filtrate, washing solution, and recovered trisodium phosphate separated as described above are appropriately diluted or dissolved, and the contained phosphorus is quantified by ICP (inductively coupled plasma) emission spectroscopy, and the amount charged (trisodium phosphate 3). The results calculated as the recovery rate for sodium 12-hydrogen salt (80.1 g) were as follows.
Filtration: 12.0%
Washing solution: 12.5%
Trisodium Phosphate: 73.7%
以上の実施例は吸着材を使用していないが、リン酸三ナトリウム１２水塩を使用することで、吸着材に吸着されたリン酸イオンとみなすことができるから、本発明の回収方法により、高純度のリン酸三ナトリウムが効率よく生産できることが示された。 Although the above embodiment does not use an adsorbent, it can be regarded as a phosphate ion adsorbed on the adsorbent by using trisodium phosphate 12-hydrate. Therefore, according to the recovery method of the present invention. It was shown that high-purity trisodium phosphate can be produced efficiently.
Claims (3)
（Ａ）リン酸イオンを吸着した、オキシ水酸化鉄をリン酸吸着成分として含有するリン酸吸着材を、３０℃以上で３～６質量％のアルカリ金属水酸化物水溶液と接触させ、当該リン酸イオンをリン酸塩水溶液として脱着させる工程、及び
（Ｂ）工程（Ａ）で得られたリン酸塩水溶液を１５℃以下に冷却することによりリン酸塩を晶出させ、当該リン酸塩と、リン酸濃度が１質量％以下であるアルカリ金属水酸化物水溶液とを回収する工程、
の両工程を有する、リン酸塩回収方法。 at least,
(A) A phosphoric acid adsorbent containing iron oxyhydroxide, which has adsorbed phosphoric acid ions, as a phosphoric acid adsorbing component is brought into contact with an alkali metal hydroxide aqueous solution of 3 to 6% by mass at 30 ° C. or higher, and the phosphorus is concerned. The phosphate solution is crystallized by cooling the phosphate aqueous solution obtained in the steps (B) and (A) to 15 ° C. or lower in the step of desorbing the acid ion as a phosphate aqueous solution, and the phosphate is combined with the phosphate solution. , A step of recovering an aqueous alkali metal hydroxide having a phosphoric acid concentration of 1% by mass or less,
Phosphate recovery method having both steps.
（Ａ’）工程（Ａ）における３～６質量％のアルカリ金属水酸化物水溶液に代えて、工程（Ｂ）で得られたリン酸濃度が１質量％以下であるアルカリ金属水酸化物水溶液を用い、リン酸イオンをリン酸塩水溶液として脱着させる工程、及び
工程（Ｂ）、
をこの順に実施することを特徴とする、リン酸塩回収方法。 The phosphate recovery method according to claim 1 or 2 , after the step (B).
(A') Instead of the 3 to 6% by mass of the alkali metal hydroxide aqueous solution in the step (A), an alkali metal hydroxide aqueous solution having a phosphoric acid concentration of 1% by mass or less obtained in the step (B) is used. The step of desorbing the phosphate ion as an aqueous phosphate solution, and the step (B),
A phosphate recovery method, characterized in that the above steps are carried out in this order.
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| JP2002370086A (en) | 2001-06-15 | 2002-12-24 | Bio Oriented Technol Res Advancement Inst | Dephosphorization method for wastewater |
| JP2006130420A (en) | 2004-11-05 | 2006-05-25 | Yuuhei Inamori | Phosphorus component recovery method |
| WO2006088083A1 (en) | 2005-02-16 | 2006-08-24 | Japan Science And Technology Agency | Method for producing iron oxyhydroxide and adsorbing material comprising iron oxyhydroxide |
| JP2008049240A (en) | 2006-08-23 | 2008-03-06 | Teijin Engineering Ltd | Phosphorus recovery and phosphorus adsorbent disattacment measure in treatment for wastewater |
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| JP2006130420A (en) | 2004-11-05 | 2006-05-25 | Yuuhei Inamori | Phosphorus component recovery method |
| WO2006088083A1 (en) | 2005-02-16 | 2006-08-24 | Japan Science And Technology Agency | Method for producing iron oxyhydroxide and adsorbing material comprising iron oxyhydroxide |
| JP2008049240A (en) | 2006-08-23 | 2008-03-06 | Teijin Engineering Ltd | Phosphorus recovery and phosphorus adsorbent disattacment measure in treatment for wastewater |
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