TY - JOUR
T1 - Stabilization of borate by hot isostatic pressing after co-precipitation with hydroxyapatite using MAP
AU - Sasaki, Keiko
AU - Hayashi, Yoshikazu
AU - Nakamura, Takeshi
AU - Guo, Binglin
AU - Tian, Quanzhi
N1 - Funding Information:
Financial support was provided to KS by Japan Society for the Promotion of Science (JSPS) KAKENHI research grants ( JP19H00883 ). TEM-EDX observations were conducted at the High Voltage Electron Microscopy Center at Kyushu University.
Publisher Copyright:
© 2020 Elsevier Ltd
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/9
Y1 - 2020/9
N2 - Boric acid is one of the most mobile inorganic contaminant species in nature due to its pKa of 9.23. Co-precipitation of borate with hydroxyapatite (HAp: Ca5(PO4)3OH) facilitates the simultaneous removal of borate with co-existing oxoanions in natural waters. The cost of phosphate is an impediment to industrialize the co-precipitation of borate with HAp for treatment of geothermal waters. In the present work, an inexpensive industrial by-product of magnesium ammonium phosphate (MAP) derived from sewage sludge, was examined as a phosphate source. MAP includes 89% pure magnesium ammonium phosphate, resulting in better performance than the pure chemical form of NH4H2PO4, because Mg2+ and Al3+ (trace elements in MAP product) play roles in enhancing the removal rate of borate and lowering the equilibrium borate concentration. These ions have a good affinity with phosphate to nucleate crystal seeds independently of powdery Ca sources. To reduce the bulky volume of solid residues, hot isostatic pressing (HIP) was applied. There is structural water in HAp; therefore, the greatest volume reduction was achieved with 78.3 ± 2.0% (n = 3). Additionally, a synergic effect to suppress the released borate, greater than the sequential combination of calcination and cold isostatic pressing was accomplished in the toxicity contents leaching procedure (TCLP) test. This is not due to larger crystal sizes alone, but it is derived from boron stabilization in HAp at an atomic level by the synergic effect of heating and pressing simultaneously.
AB - Boric acid is one of the most mobile inorganic contaminant species in nature due to its pKa of 9.23. Co-precipitation of borate with hydroxyapatite (HAp: Ca5(PO4)3OH) facilitates the simultaneous removal of borate with co-existing oxoanions in natural waters. The cost of phosphate is an impediment to industrialize the co-precipitation of borate with HAp for treatment of geothermal waters. In the present work, an inexpensive industrial by-product of magnesium ammonium phosphate (MAP) derived from sewage sludge, was examined as a phosphate source. MAP includes 89% pure magnesium ammonium phosphate, resulting in better performance than the pure chemical form of NH4H2PO4, because Mg2+ and Al3+ (trace elements in MAP product) play roles in enhancing the removal rate of borate and lowering the equilibrium borate concentration. These ions have a good affinity with phosphate to nucleate crystal seeds independently of powdery Ca sources. To reduce the bulky volume of solid residues, hot isostatic pressing (HIP) was applied. There is structural water in HAp; therefore, the greatest volume reduction was achieved with 78.3 ± 2.0% (n = 3). Additionally, a synergic effect to suppress the released borate, greater than the sequential combination of calcination and cold isostatic pressing was accomplished in the toxicity contents leaching procedure (TCLP) test. This is not due to larger crystal sizes alone, but it is derived from boron stabilization in HAp at an atomic level by the synergic effect of heating and pressing simultaneously.
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U2 - 10.1016/j.chemosphere.2020.126860
DO - 10.1016/j.chemosphere.2020.126860
M3 - Article
C2 - 32957280
AN - SCOPUS:85084047153
SN - 0045-6535
VL - 254
JO - Chemosphere
JF - Chemosphere
M1 - 126860
ER -