APPLIED CLAY SCIENCE
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2018
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IF 3.641
Shun Wang,Peixin Du,Peng Yuan,Xuemin Zhong,Yaqi Liu,Dong Liu,Liangliang Deng
This work investigated changes in the chemical composition, structure and porosity of hollow spherical allophane under alkaline conditions, which are significant not only for understanding its fate in natural environment but also for its functional applications. Hollow spherical allophane with a silicon/aluminium (Si/Al) molar ratio of 0.77 was hydrothermally synthesised followed by treatment with dilute sodium hydroxide (NaOH) solutions with different concentrations (indicated by pH values). The allophane and its alkali-treated products were then characterized using a combination of techniques, such as Fourier-transform infrared spectroscopy, nuclear magnetic resonance and nitrogen physisorption analysis. Allophane showed a weak structural stability in alkaline conditions. At pH ≤ 11.0, the framework of allophane particles was almost intact; its polymerised silicates showed only slight dissolution. At a higher pH (> 11.0), desilication and dealumination enhanced, resulting in the destruction of the imogolite local structure (ImoLS) along the edges of defect pores and the formation of amorphous materials . Most of the defect pores increased in size, becoming accessible to nitrogen and the textural parameters of the micropores reached their maximum values at a pH of 12.5. However, the damage to some secondary pores and the collapse of some hollow spherules reduced total pore volume ( V total ). At a pH of 13.0, most of the hollow spherules were observed to have collapsed, resulting in remarkable decrease in the textural parameters. However, some unbroken and/or mildly broken allophane particles might remain, deduced from the relatively high BET specific surface area (SSA) and V total and the considerable proportion of micropores for Allo 13.0 . These results reveal the dissolution behaviour of allophane in alkaline conditions and the mechanism underlying this behaviour, providing essential insights into the mineral's potential applications.
研究领域:
土壤科学
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矿物学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
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2020
·Vol. 125
·期 12
·e2020JE006590
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IF 3.717
Peixin Du,Peng Yuan,Jiacheng Liu,Yixuan Yang,Hongling Bu,Shun Wang,Junming Zhou,Hongzhe Song,Dong Liu,Joseph R. Michalski,Chengshuai Liu
Allophane, a common component on Earth and a probable constituent of the amorphous component on Mars, is closely associated with Fe in the form of structural Fe and/or iron (oxyhydr)oxide coatings. However, until now, the formation and evolution of allophane as products of environmental Fe concentrations have rarely been studied. We investigated allophane precipitation from gels with different Fe/(Fe + Al) molar ratios ( n , 0 ≤ n ≤ 1.0). X-ray diffraction patterns and Fourier transform infrared spectra of the products showed that allophane was nearly the only product at n ≤ 0.2 and that the crystallinity of Fe-rich allophane decreased with increasing n . Combined with the results of transmission electron microscopy and Mössbauer spectroscopy, Fe was found to be mainly incorporated into the gibbsite-like sheet of allophane, forming clusters; the highest Fe-for-Al substitution content was roughly estimated to be 20 mol.%. As n increased further, the formation of allophane was increasingly suppressed, and the Fe phases began to separate from the Al-Si phases, resulting in mixtures of incipient allophane and incipient akaganeite and finally akaganeite. The near-infrared spectroscopic data (1.2–2.6 μ m) of the products showed incapability in identifying poorly ordered minerals in Al-Si-Fe systems, while the features in the range of 0.4–1.2 μ m were powerful for studying iron occurrence in the products. These findings not only offer insights into the formation, evolution and geological role of allophane in Al-Si-Fe systems on Earth but also help constrain the paleoenvironment of locations where allophane and akaganeite co-occur on Mars. Key Points Environmental Fe concentrations control the formation and evolution of allophane in Al-Si-Fe systems Near-infrared spectra (1.2–2.6 μ m) show incapability in identifying short-range ordered minerals in Al-Si-Fe systems Co-occurrence of allophane and akaganeite would constrain the local palaeoenvironment on Mars
研究领域:
地质学
·
行星科学
✓ 已验证
DOI
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
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2023
·
IF 8.6
Qiyi Ma,Ning Zhao,Yanfu Wei,Shun Wang,Dong Liu,Peng Yuan
Norfloxacin contamination in the water environment has garnered international attention due to the dire risks it poses to ecosystems and public health. Aerogel can be easily extracted or separated from aqueous solutions, and it can be used for norfloxacin practical wastewater treatment. In this study, allophane and β-cyclodextrin were prepared as copolymers, and sodium alginate as a cross-linking agent to prepare allophane aerogel microspheres (A-M) for the efficient separation of norfloxacin in an aqueous environment. The A-M provides a highly three-dimensional porous structure, allowing norfloxacin to effectively penetrate the aerogels and enhancing their adsorption capacity. At pH = 7, the adsorption capacity of allophane microspheres on norfloxacin was 529 mg/g, which was 429 and 209 mg/g higher than that of β-cyclodextrin and allophane, respectively. Adsorption capacity after 5 regeneration cycles was 78.5% of the initial adsorbents. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis showed that the key adsorption mechanisms of A-M are surface complexation and hydrophobic interaction. Therefore, the prepared A-M materials are excellent adsorbents for the effective separation and removal of norfloxacin from the aquatic environment.
研究领域:
环境科学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
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2023
·
IF 9.8
Qiyi Ma,Yanfu Wei,Ning Zhao,Shun Wang,Baifa Zhang,Dong Liu,Peng Yuan
The widespread presence of ciprofloxacin (CIP) antibiotic in the water and soil poses substantial potential risks to the environment, threatening both human and animal health. In this study, we used nanoclay mineral allophane (Allo), β-cyclodextrin (β-CD) as a bifunctional monomer , and sodium alginate as a cross-linking agent, to prepare 3D porous Allo-β-CD molecularly imprinted polymers (MIPs) for the efficient removal of CIP from aqueous solution. The prepared Allo-β-CD MIP was characterized by scanning electron microscopy, transmission electron microscopy , Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and zeta potential measurements. The effects of initial concentration, time, pH level, and ion concentration on CIP removal dynamics were systematically studied. The adsorption kinetics and equilibrium data of CIP were well-fitted by the pseudo-second-order kinetic model and Langmuir isotherm models, respectively. The Allo-β-CD MIP can efficiently remove CIP from an aqueous solution, with a maximal adsorption capacity of 635 mg/g. It also has impressive recyclability , and enhanced selectivity , and is widely adaptable to various environmental conditions. The adsorption mechanisms of the as-prepared adsorbent include H bonds, hydrophobic interactions, surface complexation, and n-π EDA interactions. Given the experimental evidence, as-prepared adsorbent is therefore a promising candidate for the effective removal of CIP from the aquatic environment.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）