Nanoscale water behavior and its impact on adsorption: A case study with CNTs and diclofenac

Abstract

Water is a fundamental component of life, playing a critical role in regulating metabolic processes and facilitating the dissolution and transport of essential molecules. However, emerging contaminants, such as pharmaceuticals, pose significant challenges to water quality and safety. Nanomaterial-based technologies emerge as a promising solution for removing those contaminants from water. Nevertheless, interfacial water plays a major role in the adsorption of chemical compounds in nanomaterials—as it plays in biological processes such as protein folding, enzyme activity, and drug delivery. To understand this role, in this study, we employ molecular dynamics simulations to explore the adsorption dynamics of potassium diclofenac on single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs), considering both dry and wet conditions. Our findings reveal that the structuring of water molecules around CNTs creates hydration layers that significantly influence the accessibility of active sites and the interaction strength between contaminants and adsorbents. Our analysis indicates higher energy barriers for adsorption in DWCNTs compared to SWCNTs, which is attributed to stronger water–surface interactions. This research highlights the importance of understanding nanoscale water behavior for optimizing the design and functionality of nanomaterials for water purification. These findings can guide the development of more efficient and selective nanomaterials, enhancing contaminant removal and ensuring safer water resources while contributing to a deeper understanding of fundamental biological interactions.