Instituto Superior de Tecnologías y Ciencias Aplicadas, University of Havana, Avenida Salvador Allende, 1110, Quinta de los Molinos, Plaza de la Revolución, A.P. 6163, La Habana, Cuba.
Laboratoire COVACHIM M2E, EA 3592, Université des Antilles, BP 250, 97157, Pointe à Pitre Cedex, Guadeloupe.
J Mol Graph Model. 2018 May;81:146-154. doi: 10.1016/j.jmgm.2018.02.012. Epub 2018 Mar 9.
A theoretical study of the influence of acidic surface groups (SG) of activated carbon (AC) on chlordecone hydrate (CLDh) adsorption is presented, in order to help understanding the adsorption process under basic pH conditions. A seven rings aromatic system (coronene) with a functional group in the edge was used as a simplified model of AC to evaluate the influence of SG in the course of adsorption from aqueous solution at basic pH conditions. Two SG were modeled in their deprotonated form: carboxyl and hydroxyl (COO and O), interacting with CLDh. In order to model the solvation process, all systems under study were calculated with up to three water molecules. Multiple Minima Hypersurface (MMH) methodology was employed to study the interactions of CLDh with SG on AC using PM7 semiempirical Hamiltonian, to explore the potential energy surfaces of the systems and evaluate their thermodynamic association energies. The re-optimization of representative structures obtained from MMH was done using M06-2X Density Functional Theory. The Quantum Theory of Atoms in Molecules (QTAIM) was used to characterize the interaction types. As result, the association of CLDh with acidic SG at basic pH conditions preferentially occurs between the two alcohol groups of CLDh with COO and O groups and by dispersive interactions of chlorine atoms of CLDh with the graphitic surface. On the other hand, the presence of covalent interactions between the negatively charged oxygen of SG and one hydrogen atom of CLDh alcohol groups (O⋯HO interactions) without water molecules, was confirmed by QTAIM study. It can be concluded that the interactions of CLDh with acidic SG of AC under basic pH conditions confirms the physical mechanisms of adsorption process.
本文提出了一种关于活性炭（AC）酸性表面基团（SG）对氯丹水合物（CLDh）吸附影响的理论研究，旨在帮助理解碱性 pH 条件下的吸附过程。采用带有边缘官能团的七个环芳香系统（coronene）作为 AC 的简化模型，评估了 SG 在碱性 pH 条件下从水溶液中吸附过程中的影响。两种 SG 以去质子化形式建模：羧基和羟基（COO 和 O），与 CLDh 相互作用。为了模拟溶剂化过程，所有研究的系统都使用多达三个水分子进行了计算。采用 PM7 半经验哈密顿量，利用多点最小超曲面（MMH）方法研究了 CLDh 与 AC 上 SG 的相互作用，以探索体系的势能面并评估其热力学缔合能。从 MMH 获得的代表性结构的重新优化使用 M06-2X 密度泛函理论进行。量子原子分子理论（QTAIM）用于表征相互作用类型。结果表明，CLDh 与碱性 SG 的缔合优先发生在 CLDh 的两个醇基团与 COO 和 O 基团之间，以及 CLDh 的氯原子与石墨表面之间的色散相互作用。另一方面，通过 QTAIM 研究证实了 SG 的带负电荷的氧与 CLDh 醇基团的一个氢原子（O⋯HO 相互作用）之间存在共价相互作用，而没有水分子。可以得出结论，CLDh 与碱性 pH 条件下 AC 酸性 SG 的相互作用证实了吸附过程的物理机制。
