TY - JOUR
T1 - Adsorption and mechanistic study for phosphate removal by rice husk-derived biochar functionalized with Mg/Al-calcined layered double hydroxides via co-pyrolysis
AU - Lee, Seon Yong
AU - Choi, Jae Woo
AU - Song, Kyung Guen
AU - Choi, Keunsu
AU - Lee, Young Jae
AU - Jung, Kyung Won
N1 - Funding Information:
This study was financially supported by a National Research Council of Science & Technology (NST) grant funded by the Korea government (MSIT) (No. CAP-18-07-KICT ) and an institutional program grant (No. 2E29660 ) from the Korea Institute of Science and Technology .
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/11/1
Y1 - 2019/11/1
N2 - Direct or indirect emissions of phosphate from point or non-point sources into aquatic ecosystem may pose serious adverse risks to human life and environmental sustainability. Owing to their environmental and economic benefits, biochar-based adsorption processes have recently emerged as an ideal approach. However, the surface of biochar is normally negatively charged, thus limiting its binding affinity toward anionic contaminants. Herein, in order to address this weakness and further improve adsorption performance, we developed rice husk (RH)-derived biochar functionalized with Mg/Al-calcined layered double hydroxides (RHB/MgAl-CLDHs) via the co-pyrolysis of MgAl-LDH preloaded RH, and we examined its phosphate adsorption properties in aqueous environments. Multiple analyses and phosphate adsorption experiments revealed that the Mg:Al molar ratio (2:1–5:1) and co-pyrolysis temperature (300–700 °C) control the physicochemical properties of synthesized samples and their phosphate adsorption affinities. The molar ratio affects the charge density, whereas the co-pyrolysis temperature determines the surface functionality and porosity. Specifically, RHB/MgAl-CLDHs(2:1/500) (molar ratio = 2:1, co-pyrolysis temperature = 500 °C) exhibited the highest phosphate removal of 97.6% due to the conversion of RH into biochar, decomposition of interlayer water/nitrate, transformation of LDH structures to mixed metal oxides (layered double oxides), and improved porosity, favoring stronger adsorption and intercalation of phosphate. Spectroscopic solid-phase analyses demonstrated that the adsorption mechanism involves the “memory effect” and the formation of both outer- and inner-sphere surface complexes via attractive electrostatic interactions and monodentate/bidentate complexations. In conclusion, considering its high selectivity and excellent recyclability, RHB/MgAl-CLDHs(2:1/500) is a promising material for mitigating eutrophication.
AB - Direct or indirect emissions of phosphate from point or non-point sources into aquatic ecosystem may pose serious adverse risks to human life and environmental sustainability. Owing to their environmental and economic benefits, biochar-based adsorption processes have recently emerged as an ideal approach. However, the surface of biochar is normally negatively charged, thus limiting its binding affinity toward anionic contaminants. Herein, in order to address this weakness and further improve adsorption performance, we developed rice husk (RH)-derived biochar functionalized with Mg/Al-calcined layered double hydroxides (RHB/MgAl-CLDHs) via the co-pyrolysis of MgAl-LDH preloaded RH, and we examined its phosphate adsorption properties in aqueous environments. Multiple analyses and phosphate adsorption experiments revealed that the Mg:Al molar ratio (2:1–5:1) and co-pyrolysis temperature (300–700 °C) control the physicochemical properties of synthesized samples and their phosphate adsorption affinities. The molar ratio affects the charge density, whereas the co-pyrolysis temperature determines the surface functionality and porosity. Specifically, RHB/MgAl-CLDHs(2:1/500) (molar ratio = 2:1, co-pyrolysis temperature = 500 °C) exhibited the highest phosphate removal of 97.6% due to the conversion of RH into biochar, decomposition of interlayer water/nitrate, transformation of LDH structures to mixed metal oxides (layered double oxides), and improved porosity, favoring stronger adsorption and intercalation of phosphate. Spectroscopic solid-phase analyses demonstrated that the adsorption mechanism involves the “memory effect” and the formation of both outer- and inner-sphere surface complexes via attractive electrostatic interactions and monodentate/bidentate complexations. In conclusion, considering its high selectivity and excellent recyclability, RHB/MgAl-CLDHs(2:1/500) is a promising material for mitigating eutrophication.
KW - Adsorption
KW - Biochar
KW - Mg/Al calcined layered double hydroxides
KW - One-step functionalization
KW - Phosphate
UR - http://www.scopus.com/inward/record.url?scp=85069669883&partnerID=8YFLogxK
U2 - 10.1016/j.compositesb.2019.107209
DO - 10.1016/j.compositesb.2019.107209
M3 - Article
AN - SCOPUS:85069669883
SN - 1359-8368
VL - 176
JO - Composites Part B: Engineering
JF - Composites Part B: Engineering
M1 - 107209
ER -