Lei Cao,Jintang Guo,Jianhua Tian,Yang Xu,Miaomiao Hu,Meiyu Wang,Jinjie Fan
Ca/Al-Layered Double Hydroxide (Ca/Al-LDH), was a kind of important anionic clays with broad applications owing to its properties of exchangeable anion and adjustable particle size. In this study, Ca/Al-LDH had been successfully prepared by co-precipitation method, and it was found that the particle size, crystallinity and morphology of Ca/Al-LDH could be tuned via changing ethanol/water ratio of solution. More interestingly, with the increase of the Ca/Al-LDH’s dosage, the different crystal structure of Ca/Al-LDH had promoting effect on the development of the early strength of the cement slurries, however, the change trend of the strength growth rate of various kinds of cement slurries were quite different. Meanwhile, experimental results disclosed that the crystallinity and particle size of Ca/Al-LDH determined its interaction with cement hydration particles. That was likely to lead to a change in tricalcium silicate (C 3 S) and tricalcium aluminate (C 3 A) hydration process of accelerating or retarding under the different Ca/Al-LDH content, thus enabling the early strength development of slurry to exhibit different trends. And this finding could provide further interpretation for the effect of hydrotalcite-like materials on cement hydration process and offer a theoretical exploration for its practical application in the future.
In this paper, CaAl hydrotalcite or hydroxyapatite decorated invasive plant ( Solidago canadensis )-derived biochar were synthesized by co-precipitation and high temperature pyrolysis method. The three composites and bare biochar were characterized by Scanning electron microscopy (SEM), X-ray spectroscopy (EDX), the Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) techniques, and employed to remove Eu(III) from wastewater under a series of environmental conditions. The results indicated that the Eu(III) adsorption on BC@LDH@HAP was higher than that on BC, BC@LDH, and BC@HAP, and belonged to multi-layer adsorption, which was different from the monolayer adsorption of biochar. The adsorption could be fitted best by Langmuir model and the maximum adsorption capacity of Eu(III) on BC@LDH@HAP was up to 714 mg/g at pH ~ 6. The characterization results suggested that this excellent adsorption of BC@LDH@HAP arose from the abundant P-, C-, O-containing functional groups rather than larger specific surface area. The spectra of XPS, FT-IR, and XRD uncovered that the adsorption mechanisms of Eu(III) on BC@LDH@HAP involved surface complexation, ion exchange, and precipitation. Moreover, the absorbed Eu(III) was formed into two precipitate induced by P-containing groups and carbonate groups. This research confirmed BC@LDH@HAP is a promising material for the removal of Eu(III) in wastewater.
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