Is imogolite a suitable adsorbent agent for the herbicides like diuron and atrazine?

Abstract

Nanotubular minerals are gained researchers’ interest for environmental applications and their use as adsorbents due to their structural characteristics. Imogolite mineral belongs to aluminosilicates and can be characterised as a promising sorbent due to its abundant nature as it has both natural and synthetic origins. In the present study, the potential interactions of imogolite mineral with the herbicides diuron and atrazine have been investigated via theoretical approaches to characterise the mineral as a potential adsorbent for water or soil treatment applications. Force Field calculations showed stronger interactions between imogolite outer surface and herbicides. Diuron molecules had a better adaptation to the nanotubular shape by torsion, unlike atrazine molecules, when herbicides interacted with the inner surface due to their molecule length and rigidity. The release of the herbicides from the imogolite nanotube showed the unstable nature of both herbicides when they were loaded on the inner part of imogolite, which is in agreement with the sorption studies that proved the preference for herbicides on the outer surface and the edges of the minerals. Water molecules played a crucial role in the complexes related to imogolite properties as its inner surface is more hydrophilic. When herbicides were loaded on the outer surface, water molecules were the intermediate medium for the sorption of herbicides creating hydrogen bonds. In contrast, on the inner surface, the herbicide molecules had a competed behaviour to water. From a theoretical point of view, imogolite is a feasible sorbent for herbicides, especially when loaded on the mineral's outer part, creating high stability of complexes.