TY - JOUR
T1 - Rapid boron removal from wastewater using low-crystalline magnesium oxide
AU - Fukuda, Hiroki
AU - Tsuchiya, Kosuke
AU - Toba, Yuichiro
AU - Eguchi, Masahiro
AU - Tokoro, Chiharu
N1 - Publisher Copyright:
© 2020 Elsevier Ltd. All rights reserved.
PY - 2020/10
Y1 - 2020/10
N2 - Boron has applications in industries such as the glass and semiconductor industries. However, boron is toxic and has a significant effect on agriculture, and wastewater contaminated with boron should be treated before being discharged. Magnesium oxide (MgO) can remove boron but has not been used much in practical wastewater treatment systems because it requires between several hours and several days to immobilize boron. We have discovered a method to rapidly remove boron from wastewater by using highly reactive MgO. The MgO, in the form of low-crystalline magnesium oxide (LC-MgO), was obtained from basic magnesium carbonate (BMC) by low-temperature calcination at 500-700°C, while normal MgO is usually formed at over 1000°C. Solid analyses showed that LC-MgO had lower crystallinity and a higher specific surface area than normal MgO, both of which helped LC-MgO immobilize boron faster than normal MgO. Studies of the reaction kinetics showed that boron removal by MgO was a three-step process; (i) magnesium ions from MgO first dissolve into the aqueous phase, (ii) the dissolved magnesium ions form complexes with borate ions in the wastewater, (iii) these complexes precipitate out of solution as hydroxides when they react with free borate ions. The kinetic model also revealed that the higher surface area of LC-MgO enhanced the rate of dissolution and precipitation of magnesium ions, which increased the rate of boron removal.
AB - Boron has applications in industries such as the glass and semiconductor industries. However, boron is toxic and has a significant effect on agriculture, and wastewater contaminated with boron should be treated before being discharged. Magnesium oxide (MgO) can remove boron but has not been used much in practical wastewater treatment systems because it requires between several hours and several days to immobilize boron. We have discovered a method to rapidly remove boron from wastewater by using highly reactive MgO. The MgO, in the form of low-crystalline magnesium oxide (LC-MgO), was obtained from basic magnesium carbonate (BMC) by low-temperature calcination at 500-700°C, while normal MgO is usually formed at over 1000°C. Solid analyses showed that LC-MgO had lower crystallinity and a higher specific surface area than normal MgO, both of which helped LC-MgO immobilize boron faster than normal MgO. Studies of the reaction kinetics showed that boron removal by MgO was a three-step process; (i) magnesium ions from MgO first dissolve into the aqueous phase, (ii) the dissolved magnesium ions form complexes with borate ions in the wastewater, (iii) these complexes precipitate out of solution as hydroxides when they react with free borate ions. The kinetic model also revealed that the higher surface area of LC-MgO enhanced the rate of dissolution and precipitation of magnesium ions, which increased the rate of boron removal.
KW - Boron removal
KW - Crystallinity
KW - Kinetics
KW - Magnesium oxide
KW - Surface area
KW - Wastewater treatment
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U2 - 10.1016/j.jece.2020.104171
DO - 10.1016/j.jece.2020.104171
M3 - Article
AN - SCOPUS:85089303914
VL - 8
JO - Journal of Environmental Chemical Engineering
JF - Journal of Environmental Chemical Engineering
SN - 2213-3437
IS - 5
M1 - 104171
ER -