Two newly discovered halloysite in China and their contrasts with some typical minerals

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Marco E. Ciriotti
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Two newly discovered halloysite in China and their contrasts with some typical minerals

Messaggio da Marco E. Ciriotti » gio 08 mar, 2018 11:43

Referenza:
▪ Ouyang, J., Mu, D., Zhang, Yi, Yang, H. (2018): Mineralogy and Physico-Chemical Data of Two Newly Discovered Halloysite in China and Their Contrasts with Some Typical Minerals. Minerals, 8(3), 108; doi:10.3390/min8030108.

Abstract:
We report in this article the systematical acquisition of physico-chemical parameters for two newly discovered halloysite (Hal) minerals from Shiyan and Tongling in China. As the comparative reference, the data from Hal in Linfen, Chenxi, and the salt lake in Australia (samples were abbreviated as Hal-AU, Hal-SY, Hal-LF, Hal-CX and Hal-TL, respectively) were also investigated using X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FTIR), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray fluorescence, surface zeta potential measurements and N2 adsorption-desorption isotherms. The newly found minerals were probably formed in hydrothermal leaching and sedimentary circumstances. The Hal-SY contains 7 Å-halloysite and dickite, while Hal-TL contains 10 Å-halloysite with some alunite (similar with Hal-CX). Other impurities found in the samples include quartz, gibbsite, iron oxide and anatase. All of them showed tubular morphology with diameter in the range of 30–90 nm and a length of 300–2500 nm, while the Hal-SY has the largest inner diameter to about 150 nm. Specific surface areas varied from 26.0~59.0 m2·g−1. In addition, maximum CEC (cation exchange capacity) of the newly found Hal was about 40 cmol/kg, while that of Hal-AU was relatively low (8 cmol/kg) due to the sedimentary nature of Salt Lake circumstances. The surface charge was predominantly negative over most of the relevant pH range (>2.0). It can be concluded that the different morphology and impurity content of halloysite will greatly affect the surface area, pore volume, and cationic exchange capacity (CEC) of the minerals.
Marco E. Ciriotti

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