TY - JOUR
T1 - Removal mechanism of arsenate by bimetallic and trimetallic hydrocalumites depending on arsenate concentration
AU - Takaki, Yu
AU - Qiu, Xinhong
AU - Hirajima, Tsuyoshi
AU - Sasaki, Keiko
N1 - Funding Information:
Financial support was provided to KS by Grant-in-Aid for Scientific Research 16H02435 from Japan Society of Promotion of Science ( JSPS ) and Funding Program for Progress 100 (entitled with "Development of novel adsorbents for oxoanions using organo-modified layered compounds") through the operating expense grants of the Ministry of Education, Culture, Sports, Science, and Technology . XAFS/EXAFS spectra were collected at SAGA Light Source Kyushu Synchrotron Light Source Center (no. 2013IIK022).
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2016/12/1
Y1 - 2016/12/1
N2 - We investigated the influence of initial arsenate concentration (C0) in the 5th order of magnitude on removal of arsenate by hydrocalumite (bimetallic layered double hydroxide, LDH) and Mg-doped hydrocalumite (trimetallic LDH) from aqueous solution. These hydrocalumites were prepared by the microwave-assisted hydrothermal treatment. There is a trend that the larger adsorption density of arsenate (Qe) values is observed with bimetallic LDH under low C0 values and with trimetallic LDH under high C0 values. The transitional C0 values ranged at 2.10–2.96 mM. Comprehensively understanding characterization results for the solid residues after adsorption of arsenate by X-ray diffraction, 27Al-nuclear magnetic resonance, and scanning electron microscopy–energy dispersive X-ray, the mechanism to remove arsenate was dependent on arsenate concentrations. At low arsenate concentration, partial intercalation and dissolution–reprecipitation (DR) happened together. With increasing C0, full intercalation and DR happened to bring out one phase of arsenate-bearing hydrocalumite. Under the very high C0, DR mechanism happened at the edge sites of LDH sheets, leading that the newly formed massive precipitates block the further intercalation with nitrate. As a result, two phases of LDH were observed. The greater Qe with bimetallic LDH in low concentration comes from high crystallinity to enhance partial ion-exchange, and greater Qe with trimetallic LDH in high concentration is derived from more fragile properties to enhance DR mechanism.
AB - We investigated the influence of initial arsenate concentration (C0) in the 5th order of magnitude on removal of arsenate by hydrocalumite (bimetallic layered double hydroxide, LDH) and Mg-doped hydrocalumite (trimetallic LDH) from aqueous solution. These hydrocalumites were prepared by the microwave-assisted hydrothermal treatment. There is a trend that the larger adsorption density of arsenate (Qe) values is observed with bimetallic LDH under low C0 values and with trimetallic LDH under high C0 values. The transitional C0 values ranged at 2.10–2.96 mM. Comprehensively understanding characterization results for the solid residues after adsorption of arsenate by X-ray diffraction, 27Al-nuclear magnetic resonance, and scanning electron microscopy–energy dispersive X-ray, the mechanism to remove arsenate was dependent on arsenate concentrations. At low arsenate concentration, partial intercalation and dissolution–reprecipitation (DR) happened together. With increasing C0, full intercalation and DR happened to bring out one phase of arsenate-bearing hydrocalumite. Under the very high C0, DR mechanism happened at the edge sites of LDH sheets, leading that the newly formed massive precipitates block the further intercalation with nitrate. As a result, two phases of LDH were observed. The greater Qe with bimetallic LDH in low concentration comes from high crystallinity to enhance partial ion-exchange, and greater Qe with trimetallic LDH in high concentration is derived from more fragile properties to enhance DR mechanism.
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U2 - 10.1016/j.clay.2016.05.010
DO - 10.1016/j.clay.2016.05.010
M3 - Article
AN - SCOPUS:84971291513
SN - 0169-1317
VL - 134
SP - 26
EP - 33
JO - Applied Clay Science
JF - Applied Clay Science
ER -