20
Q. T. Lai et al.
Among the three investigated factors, modifying temperature prompted the most
significant change in REE leaching efficiency due to the effective assistance in the
diffusion of FA particle’s layers. The condition for leaching time, HCl concentration,
and temperature at 60 min, 3 mol/L, and 70 °C was selected as the optimal condition
targeting REE dissolution. The leaching of scandium and yttrium was respectively
increased from 31 and 41% up to 48 and 45% after the leaching condition optimized.
REE leaching efficiency from the FA sample in the HCl medium was relatively
high. The reasons were the low combustion temperature in the CFBC boiler (800–
900 °C) and the addition of limestone for desulfurization. It resulted in the lower
amount of REE trapped in the acid-insoluble amorphous aluminosilicate matrix and
the higher REE combined to the acid-soluble form [18]. However, the optimization
process of rare earths leaching reveals that about 55% REE was entrapped in the
acid-insoluble aluminosilicate lattice. The remaining 45% of REE was adsorbed on
the surface of FA particle or bound to acid-soluble compounds.
Conclusion
REE is the critical and non-renewable material for the development of clean innovation technologies. The value of REE in the Korean FA has created the perspective
application of its FA with respect to REE recycling. This will not only mitigate the
burden on CA managing practices but also help to reduce the intensive need of REE.
The focal point in this study was the leaching of scandium and yttrium from the
CFBC Korean FA.
HCl was chosen prior subsequent optimization process after testing the performance of HCl, HNO 3 , and H 2 SO 4 on REE leaching. The REE leaching efficiency as
the function of HCl concentration, leaching time, and temperature was investigated.
Leaching efficiency was increased by about 17% for scandium and 4% for yttrium
after the leaching condition optimized. Yield of scandium and yttrium leaching were
48%, and 45% under the optimum condition, which was reaction time, concentration
of HCl, and leaching temperature at 60 min, 3 mol/L, and 70 °C, respectively.
Acknowledgements This research was supported by the National Strategic Project-Carbon Mineralization Flagship Center of the National Research Foundation of Korea (NRF) funded by the
Ministry of Science and ICT (MSIT), the Ministry of Environment (ME), and the Ministry of
Trade, Industry, and Energy (MOTIE) (2017M3D8A2084752).
References
1. Sahoo PK, Kim K, Powell MA, Equeenuddin SM (2016) Recovery of metals and other beneficial products from coal fly ash: a sustainable approach for fly ash management. Int J Coal Sci
Technol 3:267–283
Q. T. Lai et al.
Among the three investigated factors, modifying temperature prompted the most
significant change in REE leaching efficiency due to the effective assistance in the
diffusion of FA particle’s layers. The condition for leaching time, HCl concentration,
and temperature at 60 min, 3 mol/L, and 70 °C was selected as the optimal condition
targeting REE dissolution. The leaching of scandium and yttrium was respectively
increased from 31 and 41% up to 48 and 45% after the leaching condition optimized.
REE leaching efficiency from the FA sample in the HCl medium was relatively
high. The reasons were the low combustion temperature in the CFBC boiler (800–
900 °C) and the addition of limestone for desulfurization. It resulted in the lower
amount of REE trapped in the acid-insoluble amorphous aluminosilicate matrix and
the higher REE combined to the acid-soluble form [18]. However, the optimization
process of rare earths leaching reveals that about 55% REE was entrapped in the
acid-insoluble aluminosilicate lattice. The remaining 45% of REE was adsorbed on
the surface of FA particle or bound to acid-soluble compounds.
Conclusion
REE is the critical and non-renewable material for the development of clean innovation technologies. The value of REE in the Korean FA has created the perspective
application of its FA with respect to REE recycling. This will not only mitigate the
burden on CA managing practices but also help to reduce the intensive need of REE.
The focal point in this study was the leaching of scandium and yttrium from the
CFBC Korean FA.
HCl was chosen prior subsequent optimization process after testing the performance of HCl, HNO 3 , and H 2 SO 4 on REE leaching. The REE leaching efficiency as
the function of HCl concentration, leaching time, and temperature was investigated.
Leaching efficiency was increased by about 17% for scandium and 4% for yttrium
after the leaching condition optimized. Yield of scandium and yttrium leaching were
48%, and 45% under the optimum condition, which was reaction time, concentration
of HCl, and leaching temperature at 60 min, 3 mol/L, and 70 °C, respectively.
Acknowledgements This research was supported by the National Strategic Project-Carbon Mineralization Flagship Center of the National Research Foundation of Korea (NRF) funded by the
Ministry of Science and ICT (MSIT), the Ministry of Environment (ME), and the Ministry of
Trade, Industry, and Energy (MOTIE) (2017M3D8A2084752).
References
1. Sahoo PK, Kim K, Powell MA, Equeenuddin SM (2016) Recovery of metals and other beneficial products from coal fly ash: a sustainable approach for fly ash management. Int J Coal Sci
Technol 3:267–283