Biotechnology Group, Chemical Engineering Department, Tarbiat Modares University, P.O. Box 14115-114, Tehran, Iran.
Biotechnology Group, Chemical Engineering Department, Tarbiat Modares University, P.O. Box 14115-114, Tehran, Iran.
Int J Biol Macromol. 2020 Dec 15;165(Pt A):883-901. doi: 10.1016/j.ijbiomac.2020.09.217. Epub 2020 Oct 1.
Herein, for the first time, the adsorption mechanism of HCrO and CrO (as models of Cr(VI)) by bacterial cellulose (BC), polyaniline (PANI), and BC/PANI was performed using Density Functional Theory (DFT) in both acidic and neutral pH. For this purpose, three forms of neutral, partially (pp), and fully protonated (fp) were assumed for PANI in neutral and acidic media to elucidate the influence of pH. The results indicated that the formation of hydrogen bonds (H-bond) had the main contribution in the adsorption of CrO and HCrO onto both BC and PANI. Besides, the adsorption energy of PANI was nearly 3 times as much as BC in both acidic and neutral pH. The design of the BC/PANI complex improved the stability of PANI by increasing in HOMO-LUMO energy gap from 1.1 eV to 1.97 eV. The establishment of more H-bonds, and the appearance of two different types of H-bonds, O⋯H and N⋯H, and their smaller distances (average 1.5 Å), were observed in HCrO/BC-fp-PANI complexes, while one type of hydroxyl H-bond (average 2 Å) was detected in CrO/BC-pp-PANI. It proved the adsorption of Cr(VI) is more favorable in acidic pH. The small value of charge transferred (-0.001-0.01) showed that interfacial interaction was governed by physisorption.
本文首次采用密度泛函理论（DFT）研究了细菌纤维素（BC）、聚苯胺（PANI）及其复合物在酸性和中性 pH 下对 HCrO 和 CrO（分别作为 Cr(VI)的模型）的吸附机理。为此，在中性和酸性介质中分别假设了 PANI 的三种形式：中性、部分（pp）和完全质子化（fp），以阐明 pH 的影响。结果表明，氢键（H-bond）的形成是 CrO 和 HCrO 吸附到 BC 和 PANI 上的主要贡献。此外，在酸性和中性 pH 下，PANI 的吸附能几乎是 BC 的 3 倍。BC/PANI 复合物的设计通过增加 HOMO-LUMO 能隙（从 1.1 eV 增加到 1.97 eV）来提高 PANI 的稳定性。在 HCrO/BC-fp-PANI 复合物中观察到更多的氢键（O⋯H 和 N⋯H）的形成，以及两种不同类型氢键（O⋯H 和 N⋯H）的出现，并且其距离更小（平均 1.5 Å），而在 CrO/BC-pp-PANI 中检测到一种类型的羟基氢键（平均 2 Å）。这证明了 Cr(VI)在酸性 pH 下的吸附更有利。电荷转移量（-0.001-0.01）较小表明界面相互作用受物理吸附控制。
