Interaction between carbon nanotubes and soil colloids studied with X-ray spectromicroscopy

To improve the understanding of the effect of carbon nanotubes (CNTs) on the environment, the characterization of CNTs and their interaction with soils needs to be assessed. Here, we demonstrate an analysis of pristine and modified CNTs, in dry and wet state using soft X-ray spectromicroscopy with energies around the C 1s K-shell edge (280 eV–300 eV). Apart from that, suspensions of the CNTs and the colloidal fraction as well as the extracted humic substances of a chernozem soil sample were studied. The effect of the different sample environments on the CNTs were observable both in the microscopic images and the spectral data, e.g., in aqueous environment the CNTs built clusters. Since CNTs are mainly analyzed under sterile laboratory conditions, this study intends to show how to investigate CNTs and their interaction with other substances under ambient conditions. One of the major objectives was, whether differences between CNTs and organic soil particles are distinguishable at all, and subsequently, how to describe the observed interactions.