Dual Removal Process of Phosphate on Ca-Layered Double Hydroxide with Substitution of Fe for Al

AbstractUptake of phosphate (PO43−, P) was investigated on two kinds of Ca-layered double hydroxides (LDHs) containing Fe and Al, respectively. The P removal amount was 3.37  mmol/g over Ca-Al-LDH and 2.71  mmol/g over Ca-Fe-LDH. Our results reveal that the removal of P was correlated to the dissolu...

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Bibliographic Details
Published in:Journal of hazardous, toxic and radioactive waste toxic and radioactive waste, 2014-10, Vol.18 (4)
Main Authors: Xu, Yunfeng, Lv, Huafang, Qian, Guangren, Zhang, Jia, Zhou, Ji Zhi
Format: Article
Language:English
Subjects:
Apatite
Dissolution
Hydroxides
Iron
Phosphates
Precipitates
Precipitation
Technical Papers
Uptakes
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Summary:AbstractUptake of phosphate (PO43−, P) was investigated on two kinds of Ca-layered double hydroxides (LDHs) containing Fe and Al, respectively. The P removal amount was 3.37  mmol/g over Ca-Al-LDH and 2.71  mmol/g over Ca-Fe-LDH. Our results reveal that the removal of P was correlated to the dissolution of LDH as Ca2+ precipitating P to form apatite [Ca5(PO4)3OH] in both cases. It resulted in a constant molar ratio of removed Ca2+ to P(Ca2+/P)=1.8 in the precipitate, which was close to the Ca2+/P ratio in apatite. In particular, the P adsorption on CaxFe(OH)(3+2x) from the hydrolyzed Ca-Fe-LDH was also observed with the corresponding removal amount up to 1.1  mmol/g. This decreased the Ca2+/P ratio in the case of Ca-Fe-LDH from 1.8 to 1.3, when free Ca2+ was unavailable. Consequently, we propose that the dual removal mechanism over Ca-Fe-LDH was attributed to the high aqueous solubility of Fe from the LDH dissolution.
ISSN:2153-5493
2153-5515
DOI:10.1061/(ASCE)HZ.2153-5515.0000193