Molecular simulation of carbon nanotubes as sorptive materials: sorption effects towards retene, perylene and cholesterol to 100 degrees Celsius and above

Abstract

New water purification technologies are being developed as the world’s water sources are increasingly being polluted and experience a dramatic consumption with the increasing world population. In this context, the emerging era of nanotechnology has introduced a series of innovations and materials with promising potential as sorptive materials for water decontamination. The application of nanomaterials for the purification of ground/surface water introduces nevertheless a series of important challenges, such as health and safety, cost, process-efficiency and chemical sorption properties. In this study, we consider the latter class and present a study of the sorptive properties of carbon nanotubes (CNTs) as potential water decontaminating materials. Molecular dynamics simulations are used and three molecular candidates of the water contaminants, cholesterol, perylene and retene were selected for interaction study with CNTs at different diameters. The results show that CNTs form densely packed clusters with retene, perylene and cholesterol, binding each strongly to their tubular surfaces, as well as in their hollow tubular spaces. Cholesterol and perylene bind more strongly than retene, accounting for the calculated binding energies in vacuo, however the planar geometries of polycyclics may in general favour binding to CNTs over semi-polar molecules and can require further studies. Our studies show furthermore that the CNTs retain the adsorbed molecules also at 100 degrees Celsius, and require therefore additional steps of separation for eventual recycling and reusing the nanomaterials for additional decontamination. This study is important in providing data for initiating studies and developments of water purification approaches based on using CNTs.