Effect of molecular structure on the adsorption of natural organic matter surrogates on carbon nanotubes

Abstract

Natural organic matters (NOM) with diverse molecular weights and structures are ubiquitous in the environment. NOM-mediated dispersion and stabilization of carbon nanotubes (CNTs) has been reported in previous studies. However, the effects of the NOM structures on the adsorption mechanism of CNTs are not clear. Understanding the sorption mechanisms of organic compounds on CNTs is a crucial process for assessing their environmental behavior and risks. In this study, gallic acid (GA), tannic acid (TA) and sodium dodecyl benzene sulfonate (SDBS) were chosen as the structural surrogates of NOM. Adsorption of TA on CNT was lower than the other two surrogates, prohably due to its structural rigidity. SDBS with a flexible long chain structure and GA with aplanar structure showed higher adsorption on CNTs surface due to alkane chain entanglement and subsequent surface alignment. The results showed that the molecular structure of the model compounds is dominant for their adsorption on CNTs. Therefore, molecular morphology of NOM must be considered regarding NOM mediated environmental behavior of CNTs.