Controlling phosphate release from treatment of fluoride in wastewater by using dicalcium phosphate dihydrate (DCPD)

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  • Tafu Masamoto
    Department of Industrial Chemistry and Chemical Engineering, National Institute of Technology, Toyama College
  • Muroyama Shunki
    Advanced Course, National Institute of Technology, Toyama College
  • Takamatsu Saori
    Department of Industrial Chemistry and Chemical Engineering, National Institute of Technology, Toyama College
  • Toshima Takeshi
    Department of Mechanical Engineering, National Institute of Technology, Toyama College
  • Chohji Tetsuji
    National Institute of Technology, Kagoshima College
  • Matsushita Yuya
    Chiyoda Ute Co. Ltd.
  • Fujita Takumi
    Chiyoda Ute Co. Ltd.

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Other Title
  • 第二リン酸カルシウム二水和物（DCPD）を用いたフッ素排水処理に伴うリン酸溶出の抑制技術開発
  • ダイニ リンサン カルシウム ニ スイワブツ(DCPD)オ モチイタ フッソ ハイスイ ショリ ニ トモナウ リンサン ヨウシュツ ノ ヨクセイ ギジュツ カイハツ

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<p>Calcium hydrogen phosphate dihydrate (DCPD) reacts with fluoride ion in an aqueous solution and forms stable fluorapatite (FAp). In previous studies, we have found that the reaction of DCPD is applicable to treatment of fluoride in waste water efficiently and economically. However, release of phosphate ions from the reaction of DCPD is serious problem for the application of DCPD to waste water treatment. Previously, we developed addition of calcium carbonate was effective to decrease of phosphate ions concentration in the treated water, but the mechanism of controlling phosphate ions and suitable conditions are not cleared. In this paper, we investigated the effect of addition of calcium salts on the inhibition of the release of phosphate ions from the reaction of DCPD by analyzing the mechanism of phosphate release and the effect addition of calcium ion in reaction of the DCPD with fluoride ion. We found that increasing calcium ion concentration in the solution was effective to inhibit dissolving DCPD in initial periods, and that controlling pH value between 8 to 9 had an effect for the inhabitation of the release of phosphate ions from the reaction of DCPD. We found that addition of calcium carbonate in the reaction of DCPD was effective for both of suppling calcium ion and controlling value of pH. From the results, it was concluded that usage of DCPD under controlling pH and calcium concentration was useful for treatment of fluoride in waste water.</p>

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