JP2005001949A - Magnesium oxide powder and method of manufacturing the same - Google Patents
Magnesium oxide powder and method of manufacturing the same Download PDFInfo
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- JP2005001949A JP2005001949A JP2003168369A JP2003168369A JP2005001949A JP 2005001949 A JP2005001949 A JP 2005001949A JP 2003168369 A JP2003168369 A JP 2003168369A JP 2003168369 A JP2003168369 A JP 2003168369A JP 2005001949 A JP2005001949 A JP 2005001949A
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- magnesium oxide
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 128
- 239000000395 magnesium oxide Substances 0.000 title claims abstract description 104
- 239000000843 powder Substances 0.000 title claims abstract description 85
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims abstract description 80
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 235000012245 magnesium oxide Nutrition 0.000 claims abstract description 102
- 239000002245 particle Substances 0.000 claims abstract description 57
- 239000013078 crystal Substances 0.000 claims abstract description 13
- 239000002351 wastewater Substances 0.000 claims abstract description 11
- 239000003463 adsorbent Substances 0.000 claims abstract description 9
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 8
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 52
- 239000000347 magnesium hydroxide Substances 0.000 claims description 52
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 52
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 25
- 229910052796 boron Inorganic materials 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 19
- 229910052731 fluorine Inorganic materials 0.000 claims description 17
- 239000011737 fluorine Substances 0.000 claims description 17
- 238000004065 wastewater treatment Methods 0.000 claims description 11
- 238000010304 firing Methods 0.000 claims description 7
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims 1
- 239000013535 sea water Substances 0.000 description 24
- 239000002002 slurry Substances 0.000 description 16
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 15
- 238000000034 method Methods 0.000 description 13
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 10
- 239000000920 calcium hydroxide Substances 0.000 description 10
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 10
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 9
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 8
- 229910052749 magnesium Inorganic materials 0.000 description 8
- 239000011777 magnesium Substances 0.000 description 8
- 239000002562 thickening agent Substances 0.000 description 8
- 238000001179 sorption measurement Methods 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 239000008267 milk Substances 0.000 description 6
- 210000004080 milk Anatomy 0.000 description 6
- 235000013336 milk Nutrition 0.000 description 6
- 239000012085 test solution Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000001914 filtration Methods 0.000 description 4
- 239000008235 industrial water Substances 0.000 description 4
- 150000002681 magnesium compounds Chemical class 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000011164 primary particle Substances 0.000 description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 238000005273 aeration Methods 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 2
- 239000003830 anthracite Substances 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000006114 decarboxylation reaction Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- -1 fluorine ions Chemical class 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000003456 ion exchange resin Substances 0.000 description 2
- 229920003303 ion-exchange polymer Polymers 0.000 description 2
- 239000004571 lime Substances 0.000 description 2
- 238000000634 powder X-ray diffraction Methods 0.000 description 2
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000012086 standard solution Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- 235000011389 fruit/vegetable juice Nutrition 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000003703 image analysis method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000004255 ion exchange chromatography Methods 0.000 description 1
- 238000007561 laser diffraction method Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000011775 sodium fluoride Substances 0.000 description 1
- 235000013024 sodium fluoride Nutrition 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 235000012431 wafers Nutrition 0.000 description 1
Landscapes
- Water Treatment By Sorption (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、吸着剤や排水処理剤として有用な酸化マグネシウム粉末、及びその製造方法に関する。本発明はまた、上記の酸化マグネシウム粉末を用いた排水処理方法に関する。
【０００２】
【従来の技術】
従来より、水酸化マグネシウムなどのマグネシウム化合物を焼成して酸化マグネシウム粉末を製造することが行われている。このマグネシウム化合物の焼成温度を低くすると、ペリクレース結晶子のサイズが小さく、比表面積の大きい酸化マグネシウム粉末が得られることが知られている（非特許文献１）。
【０００３】
非特許文献１には、水酸化マグネシウム粉末を５００℃程度の温度で焼成すると、水酸化マグネシウムの板状結晶の形状を残した、ペリクレース結晶子の凝集体（結晶スケルトンと呼ばれている）が形成されると記載されている。なお、この非特許文献１には、ペリクレース結晶子径が２９ｎｍ、比表面積が４０〜７０ｍ２／ｇの酸化マグネシウム粉末が記載されている。
【０００４】
ペリクレース結晶子のサイズが小さく、比表面積の大きい酸化マグネシウム粉末は、一般に高い吸着能力を有する傾向にある。
例えば、特許文献１には、熱分解により酸化マグネシウム粒子の形成が可能なマグネシウム化合物を４００〜７００℃の温度で焼成して得た酸化マグネシウム粒子からなる吸着剤が開示されている。この特許文献の実施例によれば、水酸化マグネシウムと塩基性炭酸マグネシウムを上記の温度範囲で焼成して得たペリクレース結晶子のサイズが小さく、比表面積が大きい酸化マグネシウム粉末は、排水のＣＯＤ除去率及び色度除去率が高い値を示す。
【０００５】
特許文献２には、熱分解により酸化マグネシウム粒子の形成が可能なマグネシウム化合物を４００〜７００℃の温度で焼成して得た酸化マグネシウム粒子を主成分とする吸着剤により、水中に溶解するフッ素イオンを吸着させる技術が開示されている。
【０００６】
特許文献３には、ホウ素及び／又はフッ素含有排水の効率的な処理方法として、排水に約１４００℃以下の温度で焼成して得た酸化マグネシウムを添加し、３０℃以上の温度で処理した後、固液分離する方法が開示されている。
【０００７】
【非特許文献１】
「ニューセラミック粉体ハンドブック」，株式会社サイエンスフォーラム，１９８３年，ｐ．１１９−１２１
【特許文献１】
特公昭６１−４３０８９号公報
【特許文献２】
特公昭６０−２６５９５号公報
【特許文献３】
特開２００１−３４０８７２号公報
【０００８】
【発明が解決しようとする課題】
本発明の目的は、吸着剤や排水処理剤として有用な酸化マグネシウム粉末及びその製造方法を提供することにある。本発明の目的はまた、上記の酸化マグネシウム粉末を用いた排水の処理方法を提供することにもある。
【０００９】
【課題を解決するための手段】
本発明は、平均結晶子径が１〜２０ｎｍの範囲にあるペリクレース結晶子の凝集体であって、平均粒子径が０．１〜５μｍの範囲にある板状一次凝集体を含み、比表面積が８０ｍ２／ｇ以上であって、１４００℃で灼熱後の酸化マグネシウム含有量が９８．０質量％以上である酸化マグネシウム粉末にある。
【００１０】
本発明の酸化マグネシウム粉末の好ましい態様を下記に示す。
（１）ペリクレース結晶粒子の平均粒子径が、１〜１０ｎｍの範囲にある。
（２）板状一次凝集体の平均粒子径が、０．１〜３μｍの範囲にある。
（３）比表面積が８０〜４００ｍ２／ｇの範囲にある。
（４）１４００℃で灼熱後の酸化マグネシウム含有量が、９８．８〜９９．６質量％の範囲にある。
（５）板状一次凝集体が二次凝集体を形成している。
（６）上記二次凝集体の粒子径が３０μｍ以下である。
（７）吸着剤用である。
（８）排水処理剤用である。
【００１１】
本発明はまた、平均粒子径が０．１〜５μｍの範囲にある板状水酸化マグネシウム粒子を含み、１４００℃で灼熱後の酸化マグネシウム含有量が９８．０質量％以上にある水酸化マグネシウム粉末を、３５０〜９００℃の温度で焼成することを特徴とする上記の酸化マグネシウム粉末の製造方法にもある。
【００１２】
本発明はさらに、フッ素及び／又はホウ素を含む排水に、上記の酸化マグネシウム粉末を接触させることを特徴とする排水処理方法にもある。
【００１３】
【発明の実施の形態】
本発明の酸化マグネシウム粉末は、複数個のペリクレース結晶子が板状に凝集した板状一次凝集体を含んでいる。ペリクレース結晶子の平均結晶子径は１〜２０ｎｍの範囲、好ましくは１〜１０ｎｍの範囲にある。ペリクレース結晶子の平均結晶子径は、内部標準にシリコンを用いたＸ線粉末回折法により測定することができる。
【００１４】
板状一次凝集体は、平均粒子径（板状一次凝集体表面の長軸方向の長さの平均）が、０．１〜５μｍの範囲、好ましくは０．１〜３μｍの範囲にある。板状一次凝集体の平均アスペクト比（長軸方向の長さ／厚さ）は、５〜２０の範囲にあることが好ましく、５〜１２の範囲にあることがより好ましい。板状一次凝集体の粒子径及び厚さは、電子顕微鏡の拡大画像から測定することができる。
【００１５】
本発明の酸化マグネシウム粉末は、比表面積が８０ｍ２／ｇ以上、好ましくは８０〜４００ｍ２／ｇの範囲、より好ましくは１００〜４００ｍ２／ｇの範囲にある。
【００１６】
本発明の酸化マグネシウム粉末は、１４００℃で灼熱後の酸化マグネシウム含有量が９８．０質量％以上、好ましくは９８．８〜９９．６質量％の範囲にある。１４００℃で灼熱後の酸化マグネシウム粉末は、酸化カルシウムを０．２〜０．６質量％の範囲で、酸化ケイ素とアルミナとをその合計量として０．１〜０．３質量％の範囲で含んでいてもよい。
【００１７】
本発明の酸化マグネシウム粉末は、板状一次凝集体を６０質量％以上含んでいることが好ましく、８０質量％以上含んでいることがより好ましい。板状一次凝集体は、板状一次凝集体が二次凝集体を形成していてもよい。二次凝集体は、レーザ回折法による粒子径が３０μｍ以下であることが好ましく、１０μｍ以下であることがより好ましく、８μｍ以下であることが特に好ましい。
【００１８】
本発明の酸化マグネシウム粉末は、例えば、平均粒子径が０．１〜５μｍの範囲にある板状水酸化マグネシウム粒子を含み、１４００℃で灼熱後の酸化マグネシウム含有量が９８．０質量％以上にある水酸化マグネシウム粉末を、３５０〜９００℃（好ましくは、４００〜６００℃）の温度で焼成することによって製造することができる。
前述の通り、水酸化マグネシウム粉末を５００℃程度の温度で焼成することにより、水酸化マグネシウムの板状結晶の形状を残した、ペリクレース結晶子の凝集体を得ることができることは、従来より知られている。しかしながら、本発明者の研究によれば、１４００℃で灼熱後の酸化マグネシウム含有量が９８．０質量％未満の水酸化マグネシウム粉末を焼成しても、本発明の酸化マグネシウム粉末のような平均結晶子径が２０ｎｍ以下の微細なペリクレース結晶子を形成させることは難しい。この原因は必ずしも明確ではないが、水酸化マグネシウム粉末に含まれている不純物がペリクレース結晶子の粒成長に何らかの影響を与えているものと考えられる。
【００１９】
酸化マグネシウム粉末の製造に用いる水酸化マグネシウム粉末は、例えば、海水、苦汁及びかん水などのマグネシウムを含む水に、水酸化カルシウムなどのアルカリを添加することにより製造することができる。
水酸化マグネシウム粉末の焼成炉には特には制限はない。例えば、ロータリーキルン、ヘレシヨフ炉、及び電気炉を用いることができる。
【００２０】
本発明の酸化マグネシウム粉末は、フッ素及び／又はホウ素の吸着材として、あるいはフッ素及び／又はホウ素を含む排水の処理剤として有利に使用することができる。例えば、フッ素化合物の製造及びフッ素による処理などのフッ素化学工程、シリコンウェハや電子部品の洗浄工程、アルミニウム電解製錬工程、リン酸肥料製造工程、ステンレス鋼などの金属製品ピクリング工程、電解メッキ工程、石炭を燃料とする発電所での排ガス脱硫工程などの各種の工程から排出される排水の排水処理剤として有用である。
【００２１】
本発明の酸化マグネシウム粉末を用いてフッ素及び／又はホウ素を含む排水処理を行う場合は、排水中のフッ素及び／又はホウ素量に対して質量比で１０〜１０００倍、特に好ましくは１０〜２００倍の量の酸化マグネシウム粉末を添加することが好ましい。
【００２２】
【実施例】
以下、本発明を実施例により説明する。
本実施例において、酸化マグネシウムのペリクレース結晶粒子の平均粒子径、板状一次凝集体の平均粒子径、二次凝集体の最大粒子径、比表面積、及び１４００℃の灼熱後の化学成分は、下記の方法により測定した。
【００２３】
（１）ペリクレース結晶粒子の平均粒子径：粉末Ｘ線回折法（内部標準物質にシリコンを使用）により測定した。
（２）板状一次凝集体の平均粒子径、及びアスペクト比：電子顕微鏡を用いた画像解析法により測定した。
（３）二次凝集体の最大粒子径：エタノールに試料を投入し、超音波にて試料を分散させた後、レーザー回折粒度分布測定装置により測定した。
（４）比表面積：ＢＥＴ法により測定した。
（５）１４００℃の灼熱後の化学成分：試料を１４００℃の温度で１間加熱して、酸化マグネシウム（ＭｇＯ）、酸化カルシウム（ＣａＯ）、シリカ（ＳｉＯ２）、及びアルミナ（Ａｌ２Ｏ３）の含有量を定量した。
【００２４】
［実施例１］
（１）水酸化マグネシウム粉末の製造
海水（マグネシウム濃度：１３００ｍｇ／Ｌ、炭酸濃度：８０ｍｇ／Ｌ、ホウ素成分濃度（Ｂ２Ｏ３換算）：１３ｍｇ／Ｌ）をアンスラサイトが充填されたろ過塔に通水し、海水の浮遊物を除去した。次に、海水に硫酸を加えて弱酸性とした後、エアレーションによる脱炭酸処理を行なって、海水中の炭酸濃度を１ｍｇ／Ｌとした。さらに、海水をホウ素選択性イオン交換樹脂を充填した吸着塔に空間速度ＳＶ＝６０（／Ｈ）にて通水して、海水中のホウ素成分濃度を５ｍｇ／Ｌとした。この炭酸濃度とホウ素成分濃度を低減させた海水に、水酸化カルシウム（粒径：３５０メッシュ以下）の濃度が１５質量％の石灰精製乳（水酸化カルシウムスラリー）を、海水中のマグネシウム１００モルに対してカルシウム量８４モルとなる量にて添加して、水酸化マグネシウムを生成した。次いで、シックナーを用いて水酸化マグネシウムを沈降濃縮して、濃度３５質量％の水酸化マグネシウムスラリーを得た。この水酸化マグネシウムスラリーを工業用水で洗浄し、再度シックナーにて濃度３５質量％に濃縮した。この水酸化マグネシウムスラリーをろ過脱水した後、２００℃の温度で乾燥して水酸化マグネシウム粉末を得た。得られた水酸化マグネシウム粉末は、一次粒子が六角板状（平均粒子径：０．５μｍ、平均アスペクト比：８）であって、１４００℃の灼熱後の酸化マグネシウム含有量が９９．１質量％であった。
【００２５】
（２）酸化マグネシウム粉末の製造
上記の水酸化マグネシウム粉末をロータリー型間接キルンを用いて、５３０℃の温度で３０分間焼成して酸化マグネシウム粉末を得た。得られた酸化マグネシウム粉末のペリクレース結晶粒子の平均粒子径、板状一次凝集体の平均粒子径、二次凝集体の最大粒子径、比表面積、及び１４００℃で灼熱後の化学成分を、表１に示す。
【００２６】
［実施例２］
（１）水酸化マグネシウム粉末の製造
海水（マグネシウム濃度：１３００ｍｇ／Ｌ、炭酸濃度：８０ｍｇ／Ｌ、ホウ素成分濃度（Ｂ２Ｏ３換算）：１３ｍｇ／Ｌ）をアンスラサイトが充填されたろ過塔に通水し、海水の浮遊物を除去した。次に、海水に硫酸を加えて弱酸性とした後、エアレーションによる脱炭酸処理を行なって、海水中の炭酸濃度を１ｍｇ／Ｌとした。そして、海水をホウ素選択性イオン交換樹脂を充填した吸着塔に空間速度ＳＶ＝２０（／Ｈ）にて通水して、海水中のホウ素成分濃度を１ｍｇ／Ｌとした。この炭酸濃度とホウ素成分濃度を低減させた海水に、水酸化カルシウム（粒径：３５０メッシュ以下）の濃度が１５質量％の石灰精製乳（水酸化カルシウムスラリー）を、海水中のマグネシウム１００モルに対してカルシウム量８０モルとなる量にて添加して、水酸化マグネシウムを生成した。次いで、シックナーを用いて水酸化マグネシウムを沈降濃縮して、濃度３５質量％の水酸化マグネシウムスラリーを得た。この水酸化マグネシウムスラリーを工業用水で洗浄し、再度シックナーにて濃度３５質量％に濃縮した。この水酸化マグネシウムスラリーをろ過脱水した後、２００℃の温度で乾燥して水酸化マグネシウム粉末を得た。得られた水酸化マグネシウム粉末は、一次粒子が六角板状（平均粒子径：０．２μｍ、平均アスペクト比：６）であって、１４００℃の灼熱後の酸化マグネシウム含有量が９９．５質量％であった。
【００２７】
（２）酸化マグネシウム粉末の製造
上記の水酸化マグネシウム粉末をロータリー型間接キルンを用いて、４２０℃の温度で３０分間焼成して酸化マグネシウム粉末を得た。得られた酸化マグネシウム粉末のペリクレース結晶粒子の平均粒子径、板状一次凝集体の平均粒子径、二次凝集体の最大粒子径、比表面積、及び１４００℃で灼熱後の化学成分を、表１に示す。
【００２８】
［実施例３］
（１）水酸化マグネシウム粉末の製造
海水（マグネシウム濃度：１３００ｍｇ／Ｌ、炭酸濃度：８０ｍｇ／Ｌ、ホウ素成分濃度（Ｂ２Ｏ３換算）：１３ｍｇ／Ｌ）を石灰乳（２００メッシュ以下）で充填した層を通過させ、海水中の炭酸量を１５ｍｇ／Ｌとした。この炭酸濃度を低減させた海水に、水酸化カルシウム（粒径：３５０メッシュ以下）の濃度が１５質量％の石灰精製乳（水酸化カルシウムスラリー）を、海水中のマグネシウム１００モルに対してカルシウム量８８モルとなる量にて添加して、水酸化マグネシウムを生成した。次いで、シックナーを用いて水酸化マグネシウムを沈降濃縮して、濃度３７質量％の水酸化マグネシウムスラリーを得た。この水酸化マグネシウムスラリーを工業用水で洗浄し、再度シックナーにて濃度３７質量％に濃縮した。水酸化マグネシウムスラリーをろ過脱水した後、２００℃の温度で乾燥して水酸化マグネシウム粉末を得た。得られた水酸化マグネシウム粉末は、一次粒子が六角板状（平均粒子径：０．８μｍ、平均アスペクト比：１１）であって、１４００℃の灼熱後の酸化マグネシウム含有量が９８．２質量％であった。
【００２９】
（２）酸化マグネシウム粉末の製造
上記の水酸化マグネシウム粉末をロータリー型間接キルンを用いて、５５０℃の温度で３０分間焼成して酸化マグネシウム粉末を得た。得られた酸化マグネシウム粉末のペリクレース結晶粒子の平均粒子径、板状一次凝集体の平均粒子径、二次凝集体の最大粒子径、比表面積、及び１４００℃で灼熱後の化学成分を、表１に示す。
【００３０】
［比較例１］
（１）水酸化マグネシウム粉末の製造
海水（マグネシウム濃度：１３００ｍｇ／Ｌ、炭酸濃度：８０ｍｇ／Ｌ、ホウ素成分濃度（Ｂ２Ｏ３換算）：１３ｍｇ／Ｌ）を石灰乳（６０メッシュ以下）で充填した層を通過させ、海水中の炭酸量を２０ｍｇ／Ｌとした。この炭酸濃度を低減させた海水に、水酸化カルシウム（粒径：２００メッシュ以下）の濃度が１５質量％の石灰乳（水酸化カルシウムスラリー）を、海水中のマグネシウム１００モルに対してカルシウム量８８モルとなる量にて添加して、水酸化マグネシウムを生成した。次いで、シックナーを用いて水酸化マグネシウムを沈降濃縮して、濃度４０質量％の水酸化マグネシウムスラリーを得た。この水酸化マグネシウムスラリーを工業用水で洗浄し、再度シックナーにて濃度４０質量％に濃縮した。水酸化マグネシウムスラリーをろ過脱水した後、１０５℃の温度で乾燥して水酸化マグネシウム粉末を得た。得られた水酸化マグネシウム粉末は、一次粒子が六角板状（平均粒子径：５．３μｍ、平均アスペクト比：２１）であって、１４００℃の灼熱後の酸化マグネシウム含有量が９７．３質量％であった。
【００３１】
（２）酸化マグネシウム粉末の製造
上記の水酸化マグネシウム粉末をロータリー型間接キルンを用いて、５００℃の温度で３０分間焼成して酸化マグネシウム粉末を得た。得られた酸化マグネシウム粉末のペリクレース結晶粒子の平均粒子径、板状一次凝集体の平均粒子径、二次凝集体の最大粒子径、比表面積、及び１４００℃で灼熱後の化学成分を、表１に示す。
【００３２】
【表１】
［性能試験］
実施例１乃至３、及び比較例１にて製造した酸化マグネシウム粉末のフッ素吸着能力、及びホウ素吸着能を評価した。
【００３４】
（１）フッ素吸着能力の評価
イオンクロマト用フッ素イオン標準液（フッ化ナトリウム溶液）を純水で希釈して、フッ素濃度４０ｍｇ／Ｌの試験液を作成した。この試験液１００ｍＬに、８ｇの酸化マグネシウム粉末を添加し、マグネチックスターラを用いて所定の時間撹拌した。撹拌終了後、試験液をガラスフィルターでろ過し、そのろ液中のフッ素濃度を測定した。なお、試験は気温２０℃の試験室内にて行なった。その結果を表２に示す。
【００３５】
【表２】
（２）ホウ素吸着能力の評価
原子吸光分析用ホウ素標準液（ホウ酸溶液）を純水で希釈して、ホウ素濃度５０ｍｇ／Ｌの試験液を作成した。この試験液１００ｍＬに、１０ｇの酸化マグネシウム粉末を添加し、マグネチックスターラを用いて所定の時間撹拌した。撹拌終了後、試験液をガラスフィルターでろ過し、そのろ液中のホウ素濃度を測定した。なお、試験は気温２０℃の試験室内にて行なった。その結果を表３に示す。
【００３７】
【表３】
【発明の効果】
本発明の酸化マグネシウム粉末は、従来の酸化マグネシウム粉末と比べて、微細なペリクレース結晶子の凝集体を含んでいることからフッ素、ホウ素、及び硫酸などを効率よく吸着することができる。このため、本発明の酸化マグネシウム粉末は、吸着剤、特に排水処理剤として有利に使用することができる。また、本発明の酸化マグネシウム粉末の製造方法によれば、微細なペリクレース結晶子の凝集体を含む酸化マグネシウム粉末を製造することができる。本発明のフッ素及び／又はホウ素を含む排水の処理方法によれば、効率よく排水のフッ素濃度及び／又はホウ素濃度を低減することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnesium oxide powder useful as an adsorbent or a wastewater treatment agent, and a method for producing the same. The present invention also relates to a wastewater treatment method using the magnesium oxide powder.
[0002]
[Prior art]
Conventionally, a magnesium compound powder such as magnesium hydroxide is calcined to produce a magnesium oxide powder. It is known that when the firing temperature of this magnesium compound is lowered, a magnesium oxide powder having a small periclase crystallite size and a large specific surface area can be obtained (Non-patent Document 1).
[0003]
In Non-Patent Document 1, when magnesium hydroxide powder is baked at a temperature of about 500 ° C., an aggregate of periclase crystallites (called a crystal skeleton) that retains the shape of a magnesium hydroxide plate crystal remains. It is described as being formed. This Non-Patent Document 1 describes a magnesium oxide powder having a periclase crystallite diameter of 29 nm and a specific surface area of 40 to 70 m 2 / g.
[0004]
Magnesium oxide powders having a small periclase crystallite size and a large specific surface area generally tend to have a high adsorption capacity.
For example, Patent Document 1 discloses an adsorbent composed of magnesium oxide particles obtained by baking a magnesium compound capable of forming magnesium oxide particles by thermal decomposition at a temperature of 400 to 700 ° C. According to the example of this patent document, magnesium oxide powder having a small periclase crystallite size and a large specific surface area obtained by firing magnesium hydroxide and basic magnesium carbonate in the above temperature range is used for COD removal of waste water. The rate and the chromaticity removal rate are high.
[0005]
Patent Document 2 discloses fluorine ions dissolved in water by an adsorbent mainly composed of magnesium oxide particles obtained by calcining a magnesium compound capable of forming magnesium oxide particles by thermal decomposition at a temperature of 400 to 700 ° C. A technique for adsorbing is disclosed.
[0006]
In Patent Document 3, as an efficient treatment method for boron and / or fluorine-containing wastewater, magnesium oxide obtained by firing at a temperature of about 1400 ° C. or lower is added to the wastewater, and then treated at a temperature of 30 ° C. or higher. A method of solid-liquid separation is disclosed.
[0007]
[Non-Patent Document 1]
“New Ceramic Powder Handbook”, Science Forum, Inc., 1983, p. 119-121
[Patent Document 1]
Japanese Patent Publication No. 61-43089 [Patent Document 2]
Japanese Patent Publication No. 60-26595 [Patent Document 3]
Japanese Patent Laid-Open No. 2001-340872
[Problems to be solved by the invention]
An object of the present invention is to provide a magnesium oxide powder useful as an adsorbent or a wastewater treatment agent and a method for producing the same. Another object of the present invention is to provide a wastewater treatment method using the magnesium oxide powder.
[0009]
[Means for Solving the Problems]
The present invention is an aggregate of periclase crystallites having an average crystallite diameter in the range of 1 to 20 nm, including plate-like primary aggregates having an average particle diameter in the range of 0.1 to 5 μm, and having a specific surface area. The magnesium oxide powder is 80 m 2 / g or more and the magnesium oxide content after heating at 1400 ° C. is 98.0% by mass or more.
[0010]
Preferred embodiments of the magnesium oxide powder of the present invention are shown below.
(1) The average particle diameter of the periclase crystal particles is in the range of 1 to 10 nm.
(2) The average particle diameter of the plate-like primary aggregate is in the range of 0.1 to 3 μm.
(3) The specific surface area is in the range of 80 to 400 m 2 / g.
(4) The magnesium oxide content after heating at 1400 ° C. is in the range of 98.8 to 99.6% by mass.
(5) The plate-like primary aggregates form secondary aggregates.
(6) The secondary aggregate has a particle size of 30 μm or less.
(7) For adsorbent.
(8) For waste water treatment agent.
[0011]
The present invention also includes a magnesium hydroxide powder containing plate-like magnesium hydroxide particles having an average particle diameter in the range of 0.1 to 5 μm and having a magnesium oxide content of 98.0% by mass or more after heating at 1400 ° C. Is also calcined at a temperature of 350 to 900 ° C., and there is also a method for producing the magnesium oxide powder.
[0012]
The present invention further resides in a wastewater treatment method characterized by bringing the magnesium oxide powder into contact with wastewater containing fluorine and / or boron.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The magnesium oxide powder of the present invention includes a plate-like primary aggregate in which a plurality of periclase crystallites are aggregated in a plate shape. The average crystallite diameter of the periclase crystallite is in the range of 1 to 20 nm, preferably in the range of 1 to 10 nm. The average crystallite diameter of the periclase crystallite can be measured by an X-ray powder diffraction method using silicon as an internal standard.
[0014]
The plate-like primary aggregate has an average particle diameter (average length in the major axis direction of the plate-like primary aggregate surface) in the range of 0.1 to 5 μm, preferably in the range of 0.1 to 3 μm. The average aspect ratio (length / thickness in the major axis direction) of the plate-like primary aggregate is preferably in the range of 5 to 20, and more preferably in the range of 5 to 12. The particle diameter and thickness of the plate-like primary aggregate can be measured from an enlarged image of an electron microscope.
[0015]
Magnesium oxide powder of the present invention has a specific surface area of 80 m 2 / g or more, preferably in the range of 80~400m 2 / g, more preferably in the range of 100 to 400 m 2 / g.
[0016]
The magnesium oxide powder of the present invention has a magnesium oxide content after heating at 1400 ° C. of 98.0% by mass or more, preferably 98.8 to 99.6% by mass. The magnesium oxide powder after heating at 1400 ° C. contains calcium oxide in the range of 0.2 to 0.6% by mass, and the total amount of silicon oxide and alumina in the range of 0.1 to 0.3% by mass. You may go out.
[0017]
The magnesium oxide powder of the present invention preferably contains 60% by mass or more, and more preferably 80% by mass or more of the plate-like primary aggregate. In the plate-like primary aggregate, the plate-like primary aggregate may form a secondary aggregate. The secondary aggregate preferably has a particle size of 30 μm or less, more preferably 10 μm or less, and particularly preferably 8 μm or less, as measured by a laser diffraction method.
[0018]
The magnesium oxide powder of the present invention includes, for example, plate-like magnesium hydroxide particles having an average particle diameter in the range of 0.1 to 5 μm, and the magnesium oxide content after heating at 1400 ° C. is 98.0% by mass or more. A certain magnesium hydroxide powder can be produced by firing at a temperature of 350 to 900 ° C. (preferably 400 to 600 ° C.).
As described above, it has been conventionally known that an aggregate of periclase crystallites that retains the shape of magnesium hydroxide plate crystals can be obtained by firing magnesium hydroxide powder at a temperature of about 500 ° C. ing. However, according to the study of the present inventor, even if magnesium hydroxide powder having a magnesium oxide content of less than 98.0% by mass at 1400 ° C. is calcined, the average crystal like the magnesium oxide powder of the present invention is calcined. It is difficult to form fine periclase crystallites having a diameter of 20 nm or less. Although this cause is not necessarily clear, it is considered that impurities contained in the magnesium hydroxide powder have some influence on the grain growth of the periclase crystallite.
[0019]
The magnesium hydroxide powder used for the production of the magnesium oxide powder can be produced, for example, by adding an alkali such as calcium hydroxide to water containing magnesium such as seawater, bitter juice and brine.
There is no particular limitation on the firing furnace for magnesium hydroxide powder. For example, a rotary kiln, a Heleshov furnace, and an electric furnace can be used.
[0020]
The magnesium oxide powder of the present invention can be advantageously used as an adsorbent for fluorine and / or boron or as a treatment agent for wastewater containing fluorine and / or boron. For example, fluorine chemical processes such as the manufacture of fluorine compounds and treatment with fluorine, cleaning processes for silicon wafers and electronic parts, aluminum electrolytic smelting processes, phosphate fertilizer manufacturing processes, pickling processes for metal products such as stainless steel, electrolytic plating processes, It is useful as a wastewater treatment agent for wastewater discharged from various processes such as an exhaust gas desulfurization process at a power plant using coal as fuel.
[0021]
When wastewater treatment containing fluorine and / or boron is performed using the magnesium oxide powder of the present invention, the mass ratio is 10 to 1000 times, particularly preferably 10 to 200 times, relative to the amount of fluorine and / or boron in the wastewater. It is preferable to add the amount of magnesium oxide powder.
[0022]
【Example】
Hereinafter, the present invention will be described with reference to examples.
In this example, the average particle diameter of the periclase crystal particles of magnesium oxide, the average particle diameter of the plate-like primary aggregate, the maximum particle diameter of the secondary aggregate, the specific surface area, and the chemical components after 1400 ° C. heating are as follows: It measured by the method of.
[0023]
(1) Average particle diameter of periclase crystal particles: measured by a powder X-ray diffraction method (silicon is used as an internal standard substance).
(2) Average particle diameter and aspect ratio of plate-like primary aggregates: measured by an image analysis method using an electron microscope.
(3) Maximum particle size of secondary aggregate: A sample was put into ethanol, and the sample was dispersed with ultrasonic waves, and then measured with a laser diffraction particle size distribution analyzer.
(4) Specific surface area: measured by the BET method.
(5) Chemical components after heating at 1400 ° C .: The sample is heated for 1 minute at a temperature of 1400 ° C., and magnesium oxide (MgO), calcium oxide (CaO), silica (SiO 2 ), and alumina (Al 2 O 3) ) Content was quantified.
[0024]
[Example 1]
(1) Manufacture of Magnesium Hydroxide Powder Seawater (magnesium concentration: 1300 mg / L, carbonic acid concentration: 80 mg / L, boron component concentration (converted to B 2 O 3 ): 13 mg / L) into a filtration tower filled with anthracite Water was passed through to remove seawater suspended matter. Next, sulfuric acid was added to seawater to make it weakly acidic, followed by decarboxylation by aeration, so that the carbonic acid concentration in seawater was 1 mg / L. Further, seawater was passed through an adsorption tower packed with boron-selective ion exchange resin at a space velocity of SV = 60 (/ H), so that the boron component concentration in the seawater was 5 mg / L. Lime refined milk (calcium hydroxide slurry) with a calcium hydroxide (particle size: 350 mesh or less) concentration of 15% by mass is added to 100 mol of magnesium in the seawater to the seawater with reduced carbonate and boron component concentrations. On the other hand, calcium hydroxide was added in an amount of 84 mol to produce magnesium hydroxide. Next, magnesium hydroxide was precipitated and concentrated using a thickener to obtain a magnesium hydroxide slurry having a concentration of 35% by mass. This magnesium hydroxide slurry was washed with industrial water and again concentrated to a concentration of 35% by mass with a thickener. The magnesium hydroxide slurry was dewatered by filtration and then dried at a temperature of 200 ° C. to obtain a magnesium hydroxide powder. The obtained magnesium hydroxide powder has hexagonal plate-like primary particles (average particle size: 0.5 μm, average aspect ratio: 8), and the magnesium oxide content after heating at 1400 ° C. is 99.1% by mass. Met.
[0025]
(2) Production of magnesium oxide powder The magnesium hydroxide powder was fired at a temperature of 530 ° C for 30 minutes using a rotary indirect kiln to obtain a magnesium oxide powder. Table 1 shows the average particle diameter of the periclase crystal particles of the obtained magnesium oxide powder, the average particle diameter of the plate-like primary aggregate, the maximum particle diameter of the secondary aggregate, the specific surface area, and the chemical composition after heating at 1400 ° C. Shown in
[0026]
[Example 2]
(1) Manufacture of Magnesium Hydroxide Powder Seawater (magnesium concentration: 1300 mg / L, carbonic acid concentration: 80 mg / L, boron component concentration (converted to B 2 O 3 ): 13 mg / L) into a filtration tower filled with anthracite Water was passed through to remove seawater suspended matter. Next, sulfuric acid was added to seawater to make it weakly acidic, followed by decarboxylation by aeration, so that the carbonic acid concentration in seawater was 1 mg / L. Then, seawater was passed through an adsorption tower filled with boron-selective ion exchange resin at a space velocity of SV = 20 (/ H), so that the boron component concentration in seawater was 1 mg / L. Lime refined milk (calcium hydroxide slurry) with a calcium hydroxide (particle size: 350 mesh or less) concentration of 15% by mass is added to 100 mol of magnesium in the seawater to the seawater with reduced carbonate and boron component concentrations. On the other hand, magnesium hydroxide was produced by adding calcium in an amount of 80 mol. Next, magnesium hydroxide was precipitated and concentrated using a thickener to obtain a magnesium hydroxide slurry having a concentration of 35% by mass. This magnesium hydroxide slurry was washed with industrial water and again concentrated to a concentration of 35% by mass with a thickener. The magnesium hydroxide slurry was dewatered by filtration and then dried at a temperature of 200 ° C. to obtain a magnesium hydroxide powder. The obtained magnesium hydroxide powder has a primary particle hexagonal plate shape (average particle size: 0.2 μm, average aspect ratio: 6), and the magnesium oxide content after heating at 1400 ° C. is 99.5% by mass. Met.
[0027]
(2) Production of magnesium oxide powder The magnesium hydroxide powder was fired at a temperature of 420 ° C for 30 minutes using a rotary indirect kiln to obtain a magnesium oxide powder. Table 1 shows the average particle diameter of the periclase crystal particles of the obtained magnesium oxide powder, the average particle diameter of the plate-like primary aggregate, the maximum particle diameter of the secondary aggregate, the specific surface area, and the chemical composition after heating at 1400 ° C. Shown in
[0028]
[Example 3]
(1) Manufacture of magnesium hydroxide powder Seawater (magnesium concentration: 1300 mg / L, carbonate concentration: 80 mg / L, boron component concentration (converted to B 2 O 3 ): 13 mg / L) filled with lime milk (200 mesh or less) The amount of carbonic acid in the seawater was 15 mg / L. Lime refined milk (calcium hydroxide slurry) in which the concentration of calcium hydroxide (particle size: 350 mesh or less) is 15% by mass is added to the seawater in which the carbonic acid concentration is reduced. An amount of 88 mol was added to produce magnesium hydroxide. Subsequently, the magnesium hydroxide was precipitated and concentrated using a thickener to obtain a magnesium hydroxide slurry having a concentration of 37% by mass. This magnesium hydroxide slurry was washed with industrial water and again concentrated to a concentration of 37% by mass with a thickener. The magnesium hydroxide slurry was filtered and dehydrated, and then dried at a temperature of 200 ° C. to obtain a magnesium hydroxide powder. The obtained magnesium hydroxide powder has a primary particle hexagonal plate shape (average particle diameter: 0.8 μm, average aspect ratio: 11), and the magnesium oxide content after heating at 1400 ° C. is 98.2% by mass. Met.
[0029]
(2) Production of magnesium oxide powder The magnesium hydroxide powder was fired at a temperature of 550 ° C for 30 minutes using a rotary indirect kiln to obtain a magnesium oxide powder. Table 1 shows the average particle diameter of the periclase crystal particles of the obtained magnesium oxide powder, the average particle diameter of the plate-like primary aggregate, the maximum particle diameter of the secondary aggregate, the specific surface area, and the chemical composition after heating at 1400 ° C. Shown in
[0030]
[Comparative Example 1]
(1) Manufacture of magnesium hydroxide powder Seawater (magnesium concentration: 1300 mg / L, carbonic acid concentration: 80 mg / L, boron component concentration (converted to B 2 O 3 ): 13 mg / L) is filled with lime milk (60 mesh or less) The amount of carbonic acid in seawater was 20 mg / L. Lime milk (calcium hydroxide slurry) having a calcium hydroxide (particle size: 200 mesh or less) concentration of 15 mass% is added to the seawater in which the carbonic acid concentration is reduced, and the calcium amount is 88 with respect to 100 mol of magnesium in the seawater. Addition in a molar amount produced magnesium hydroxide. Subsequently, the magnesium hydroxide was precipitated and concentrated using a thickener to obtain a magnesium hydroxide slurry having a concentration of 40% by mass. This magnesium hydroxide slurry was washed with industrial water and again concentrated to a concentration of 40% by mass with a thickener. The magnesium hydroxide slurry was filtered and dehydrated, and then dried at a temperature of 105 ° C. to obtain a magnesium hydroxide powder. The obtained magnesium hydroxide powder has a primary particle hexagonal plate shape (average particle size: 5.3 μm, average aspect ratio: 21), and the magnesium oxide content after heating at 1400 ° C. is 97.3% by mass. Met.
[0031]
(2) Production of magnesium oxide powder The magnesium hydroxide powder was fired at a temperature of 500 ° C for 30 minutes using a rotary indirect kiln to obtain a magnesium oxide powder. Table 1 shows the average particle diameter of the periclase crystal particles of the obtained magnesium oxide powder, the average particle diameter of the plate-like primary aggregate, the maximum particle diameter of the secondary aggregate, the specific surface area, and the chemical composition after heating at 1400 ° C. Shown in
[0032]
[Table 1]
[performance test]
The fluorine adsorption ability and the boron adsorption ability of the magnesium oxide powder produced in Examples 1 to 3 and Comparative Example 1 were evaluated.
[0034]
(1) Evaluation of fluorine adsorption capacity A fluorine ion standard solution (sodium fluoride solution) for ion chromatography was diluted with pure water to prepare a test solution having a fluorine concentration of 40 mg / L. To 100 mL of this test solution, 8 g of magnesium oxide powder was added and stirred for a predetermined time using a magnetic stirrer. After the stirring, the test solution was filtered with a glass filter, and the fluorine concentration in the filtrate was measured. The test was conducted in a test room at an air temperature of 20 ° C. The results are shown in Table 2.
[0035]
[Table 2]
(2) Evaluation of boron adsorption ability A boron standard solution (boric acid solution) for atomic absorption analysis was diluted with pure water to prepare a test solution having a boron concentration of 50 mg / L. To 100 mL of this test solution, 10 g of magnesium oxide powder was added and stirred for a predetermined time using a magnetic stirrer. After completion of stirring, the test solution was filtered with a glass filter, and the boron concentration in the filtrate was measured. The test was conducted in a test room at an air temperature of 20 ° C. The results are shown in Table 3.
[0037]
[Table 3]
【The invention's effect】
The magnesium oxide powder of the present invention can adsorb fluorine, boron, sulfuric acid, and the like more efficiently than the conventional magnesium oxide powder because it contains fine aggregates of periclase crystallites. For this reason, the magnesium oxide powder of the present invention can be advantageously used as an adsorbent, particularly as a wastewater treatment agent. Moreover, according to the manufacturing method of the magnesium oxide powder of this invention, the magnesium oxide powder containing the aggregate of a fine periclase crystallite can be manufactured. According to the method for treating wastewater containing fluorine and / or boron of the present invention, the fluorine concentration and / or boron concentration of wastewater can be efficiently reduced.
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| JP2007022902A (en) * | 2005-06-17 | 2007-02-01 | Ube Ind Ltd | Latent crystalline magnesia and method for producing the same |
| JP2007070219A (en) * | 2005-08-10 | 2007-03-22 | Ube Material Industries Ltd | High specific surface area magnesium oxide powder and method for producing the same |
| JP2007084360A (en) * | 2005-09-20 | 2007-04-05 | Ube Material Industries Ltd | Magnesium oxide powder for soil hardening material |
| JP2007136424A (en) * | 2005-11-22 | 2007-06-07 | Kyowa Chem Ind Co Ltd | Method for treating waste water containing fluorine ion |
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