TY - JOUR
T1 - Effect of calcination temperature for magnesite on interaction of MgO-rich phases with boric acid
AU - Sasaki, Keiko
AU - Moriyama, Sayo
N1 - Funding Information:
Financial support was provided to KS by JSPS Funding Program for Next-Generation World Leading Researchers (NEXT Program) GR078. TEM observation was conducted in high voltage electron microscopy (HVEM), Kyushu University.
PY - 2014/1
Y1 - 2014/1
N2 - Magnesia (MgO), which can be obtained by calcination of natural magnesite, is one of the most effective known sorbents for borate in aqueous solutions. Here we examine the effect of calcination temperature on sorption of borate for MgO-rich phases produced by calcination of magnesite at 873-1373 K. Calcination at or above 1273 K produced a single magnesium oxide phase, whereas basic magnesium carbonates (mMgCO3·nMg(OH)2· xH2O) formed in association with magnesium oxide at or below 1073 K. Calcination temperature directly affected the efficiency of decarbonation of magnesium carbonate, and the solubility and basicity of magnesium oxide in the resultant calcined products. These factors (along with the boron concentration) essentially control the immobilization mechanism of borate on the calcined MgO-rich phases. After sorption of borate on products calcined at lower temperatures, different types of basic magnesium carbonates were formed that are less effective at immobilizing borate. At low borate concentrations, under saturation for magnesium borate hydrate (Mg7B4O 13·7H2O), co-precipitation of borate with Mg(OH)2 predominates. However, as magnesium borate hydrate becomes supersaturated, both precipitation of Mg7B4O 13·7H2O and co-precipitation with Mg(OH) 2 contribute significantly to borate immobilization. Calcination temperature is a key practical factor affecting the borate sorption efficiency by changing the immobilization mechanism.
AB - Magnesia (MgO), which can be obtained by calcination of natural magnesite, is one of the most effective known sorbents for borate in aqueous solutions. Here we examine the effect of calcination temperature on sorption of borate for MgO-rich phases produced by calcination of magnesite at 873-1373 K. Calcination at or above 1273 K produced a single magnesium oxide phase, whereas basic magnesium carbonates (mMgCO3·nMg(OH)2· xH2O) formed in association with magnesium oxide at or below 1073 K. Calcination temperature directly affected the efficiency of decarbonation of magnesium carbonate, and the solubility and basicity of magnesium oxide in the resultant calcined products. These factors (along with the boron concentration) essentially control the immobilization mechanism of borate on the calcined MgO-rich phases. After sorption of borate on products calcined at lower temperatures, different types of basic magnesium carbonates were formed that are less effective at immobilizing borate. At low borate concentrations, under saturation for magnesium borate hydrate (Mg7B4O 13·7H2O), co-precipitation of borate with Mg(OH)2 predominates. However, as magnesium borate hydrate becomes supersaturated, both precipitation of Mg7B4O 13·7H2O and co-precipitation with Mg(OH) 2 contribute significantly to borate immobilization. Calcination temperature is a key practical factor affecting the borate sorption efficiency by changing the immobilization mechanism.
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U2 - 10.1016/j.ceramint.2013.07.056
DO - 10.1016/j.ceramint.2013.07.056
M3 - Article
AN - SCOPUS:84888008185
SN - 0272-8842
VL - 40
SP - 1651
EP - 1660
JO - Ceramics International
JF - Ceramics International
IS - 1 PART B
ER -