Journal
COMPOSITES PART B-ENGINEERING
Volume 176, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.compositesb.2019.107209
Keywords
Biochar; Mg/Al calcined layered double hydroxides; One-step functionalization; Phosphate; Adsorption
Funding
- National Research Council of Science & Technology (NST) - Korea government (MSIT) [CAP-18-07-KICT]
- Korea Institute of Science and Technology [2E29660]
- National Research Council of Science & Technology (NST), Republic of Korea [CAP-18-07-KICT] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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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 degrees 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 degrees 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.
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