Al Lafi Abdul G, Khuder Ali
Polymer Chemistry Division, Department of Chemistry, Atomic Energy Commission, P. O. Box: 9061, Damascus, Syrian Arab Republic.
Nuclear Chemistry Division, Department of Chemistry, Atomic Energy Commission, P. O. Box: 9061, Damascus, Syrian Arab Republic.
Heliyon. 2025 Jan 10;11(2):e41862. doi: 10.1016/j.heliyon.2025.e41862. eCollection 2025 Jan 30.
Molecular scale information is needed to understand ions coordination to mineral surfaces and consequently to accelerate the design of improved adsorbents. The present work reports on the use of two-dimensional correlation Fourier Transform infra-red spectroscopy (2D-COS-FTIR) and hetero 2D-COS-FTIR- X-ray diffraction (XRD) to probe the mechanism of Cr(VI) removal from aqueous solutions by activated carbon (AC) and its composite with PWO (AC-composite). The adsorption data at an initial Cr(VI) concentration of 320 mg L (320 ppm) revealed maximum adsorption capacities of 65 mg g for AC and 73 mg g for AC-composite, corresponding to removal percentages of 83 % and 94 %, respectively. The adsorption mechanism of Cr(VI) onto AC involved electrostatic attraction of charged ions, reduction of Cr(VI), orientation of O-H groups, complex formation and ion exchange reaction. On the other hand, ion exchange reactions were not observed in the case of AC-composite, but increasing reduction and complex formation due to the presence of W were more pronounced. Moreover, a monosubstituted compound; i.e. KPCrW O·nHO, having chromium in its maximum oxidation state (Cr(VI)) was formed. These resulted in an improved adsorption capacity of AC-composite towards Cr(VI) in comparison to AC, and could explain the differences in adsorption thermodynamics and capacity of the two studied adsorbents. High value information could be extracted from both FTIR spectroscopy and XRD patterns when combined with available 2D-COS routines and subsequently powerful tools to investigate the mechanisms of adsorption are obtained.
为了理解离子与矿物表面的配位作用，并进而加速改进型吸附剂的设计，需要分子尺度的信息。本工作报道了利用二维相关傅里叶变换红外光谱（2D-COS-FTIR）和异质二维相关傅里叶变换红外光谱- X射线衍射（XRD）来探究活性炭（AC）及其与PWO的复合材料（AC-复合材料）从水溶液中去除Cr(VI)的机理。初始Cr(VI)浓度为320 mg L（320 ppm）时的吸附数据表明，AC的最大吸附容量为65 mg g，AC-复合材料的最大吸附容量为73 mg g，对应的去除率分别为83%和94%。Cr(VI)在AC上的吸附机理涉及带电离子的静电吸引、Cr(VI)的还原、O-H基团的取向、络合物形成和离子交换反应。另一方面，在AC-复合材料的情况下未观察到离子交换反应，但由于W的存在，还原和络合物形成的增加更为明显。此外，还形成了一种单取代化合物；即KPCrW O·nHO，其中铬处于其最高氧化态（Cr(VI)）。与AC相比，这些导致AC-复合材料对Cr(VI)的吸附容量提高，并且可以解释两种研究吸附剂在吸附热力学和容量方面的差异。当与可用的二维相关程序相结合时，可以从傅里叶变换红外光谱和XRD图谱中提取高价值信息，从而获得研究吸附机理的强大工具。
