Abou-El-Sherbini Khaled S, Morsi Reham M M, Elzahany Eman A M, Nour Mohamed A, Drweesh Elsayed A
Department of Inorganic Chemistry, National Research Centre, 33 El Bohouth st. (former Eltahrir st.), Dokki, Giza P.O.12622, Egypt.
Physical Chemistry Department, National Research Centre, 33 El Bohoth St., Dokki, P.O. 12622 Giza, Egypt.
Spectrochim Acta A Mol Biomol Spectrosc. 2025 Jan 5;324:124990. doi: 10.1016/j.saa.2024.124990. Epub 2024 Aug 17.
Kaolin, a naturally occurring clay mineral renowned for its distinctive properties, holds significant importance across various industries. The integration of dimethyl sulfoxide (DMSO) into kaolin matrices, both in the presence and absence of water, has been extensively explored for its potential to enhance material characteristics. Addressing debates surrounding the proposed adsorption mechanism for the type I structure of DMSO, this study undertook a comprehensive physicochemical characterization of DMSO-kaolin complexes (DMSO-KCs) derived from untreated (UnK) and HCl-treated (HK) Egyptian ore, with a focus on elucidating the loading mechanism facilitated by water. Key insights gleaned from electrical conductivity, dielectric constant, and Fine Testing Technology - Fourier-transform infrared (FTT-FTIR) measurements, shedding light on the bonding nature of DMSO-KCs. FTT-FTIR analysis revealed two stages of water departure at 180 °C, with the final stage coinciding with the release of pyrolysis gases, confirming the catalytic degradation of DMSO. Through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), two distinct bonding types of DMSO molecules with kaolinite were identified: amorphous adsorbed (type I) and lattice-oriented intercalated (type II). Electrical characteristic evaluations within the temperature range of room temperature (RT) to 260 °C and frequency range of 42 Hz-1 MHz revealed that DMSO intercalation enhances the electrical properties of kaolin. Hydrated DMSO-KCs exhibited higher values of σ and ɛ' compared to non-hydrated samples. The activation energy (E) values for HCl-treated samples were smaller than those of untreated ones. Alternating current (AC) conductivity analysis indicated predominantly ionic behavior with frequency and temperature dependency in both HCl-treated and untreated kaolin. Our findings substantiate the adsorption mechanism of Type I DMSO, highlighting its amorphous nature, instability, and catalytic degradation over time, in contrast to the intercalated type II. This elucidation is pivotal for understanding the behavior of DMSO-KCs across diverse applications, including electronics, ceramics, and materialsscience.
高岭土是一种以其独特性质而闻名的天然粘土矿物，在各个行业都具有重要意义。在有水和无水的情况下，将二甲基亚砜（DMSO）融入高岭土基质中，因其增强材料特性的潜力而受到广泛研究。为了解决围绕DMSO I型结构提出的吸附机制的争论，本研究对源自未处理（UnK）和HCl处理（HK）的埃及矿石的DMSO-高岭土复合物（DMSO-KCs）进行了全面的物理化学表征，重点是阐明水促进的负载机制。从电导率、介电常数和精细测试技术 - 傅里叶变换红外（FTT-FTIR）测量中获得的关键见解，揭示了DMSO-KCs的键合性质。FTT-FTIR分析显示在180°C时有两个水逸出阶段，最后阶段与热解气体的释放相吻合，证实了DMSO的催化降解。通过X射线衍射（XRD）、傅里叶变换红外光谱（FTIR）和热重分析（TGA），确定了DMSO分子与高岭石的两种不同键合类型：无定形吸附（I型）和晶格取向插层（II型）。在室温（RT）至260°C的温度范围内和42 Hz - 1 MHz的频率范围内进行的电特性评估表明，DMSO插层增强了高岭土的电学性质。与未水合的样品相比，水合的DMSO-KCs表现出更高的σ和ɛ'值。HCl处理样品的活化能（E）值小于未处理样品的活化能值。交流电（AC）电导率分析表明，在HCl处理和未处理的高岭土中，主要表现为离子行为，且与频率和温度有关。我们的研究结果证实了I型DMSO的吸附机制，突出了其无定形性质、不稳定性以及随时间的催化降解，这与插层的II型形成对比。这一阐释对于理解DMSO-KCs在包括电子、陶瓷和材料科学在内的各种应用中的行为至关重要。
