Chlordecone Adsorption on Functionalized Activated Carbons: Computational Chemistry as a Tool for Understanding the Adsorption Process

Abstract

Chlordecone (CLD) has been used as a pesticide for a long time to control the proliferation of various insects in tropical countries like the French West Indies. CLD was included in 2009 in the list of persistent organic pollutants (POPs) by the Stockholm Convention, prohibiting its production and use worldwide. Thus, its removal from water and soils is a sanitary emergency. With the purpose of limiting impregnation of the population by chlordecone in Martinique and Guadeloupe, since 1999 production and drinking water purification installations have been equipped with activated carbon filters without much knowledge on the adsorption mechanism of these pollutants on activated carbons (AC) surface. This article reviews the available information about how functionalized activated carbons can be used for improving the decontamination of polluted with CLD waters. The recent computational investigations about the CLD interactions with functionalized AC by molecular modeling are well-reviewed, considering geometrical and energetic features with the purpose of better understand the adsorption process. Finally, some aspects, trends, and perspectives on using computational tools for understanding the adsorption of CLD on AC and designing more efficient AC are also discussed.

Role of Basic Surface Groups of Activated Carbon in Chlordecone and β-Hexachlorocyclohexane Adsorption: A Molecular Modelling Study

“…Previous studies of similar systems showed that 700 configurations are sufficient for the association energy of the molecular complexes to converge on a fixed value [23,50]. The hypothesis of a maximum of three water molecules was considered, as previous studies show that for similar systems, this number is sufficient to saturate the surface OH and COOH groups [23,[29][30][31]39,51]. Considering that the adsorption of CLD and β-HCH takes place in an aqueous medium, the GS/(H 2 O) n=0-3 systems were also studied as reference.…”

“…These may provide a first selection criterion for the preparation of AC with suitable surface properties. Later, MMH, high-level quantum calculations based on density functional theory (DFT) [25,26], and a topological exploration of the electron density based on the quantum theory of atoms in molecules (QTAIM) [27,28] approach were successfully used to identify the main interactions types of CLD with acidic SGs (hydroxyl and carboxyl) under different pH and solvation conditions [29][30][31]. These theoretical results are consistent with experimental findings [22], indicating that the AC with the highest content of COOH SGs showed the strongest CLD/SG interaction under slightly acidic and neutral pH conditions, considering Nakanishi's criteria [32,33].…”

“…Now, it is important to focus the attention on finding the best surface groups and operational conditions that enhance the adsorption process of pesticides into activated carbon, which is the main goal of the present work. To our knowledge, there are not molecular modeling studies of the interaction of CLD and β-HCH with AC basic surface groups [31]. Taking into account the above-mentioned experimental and theoretical results, the present work focuses on evaluating, for the first time, the influence of some of the functionalities of AC basic surface groups, such as nitrogen-containing groups, over the adsorption of CLD and β-HCH, considering pH and solvent effects.…”