Mechanisms And Influence Factors Of The Interaction Between Natural Organic Matter And Carbon Nanotubes

Carbon nanotubes (CNTs) have the potential to be released into the aquatic environment during their life-cycles. The ubiquitous natural organic matter (NOM) in the aquatic environment can interact with CNTs and consequently affect their aquatic environmental behavior and ecological effect. Therefore, the interaction between NOM and CNTs has caused wide concern, and the mechanism and influencing factors of the interaction required more studies. In this study, four humid acids (HAs, as a model NOM) with different polarity and three multi-walled carbon nanotubes (MWCNTs) with various diameters were selected to explore HAs adsorption on and stabilizing MWCNTs in wate, with a focus on the effects of HA, MWCNT and solution properties. Styrene sulfonic acid sodium salt (SS) and poly(styrene sulfonic acid sodium salt)(PSS) with different molecular weight were used to study SS/PSS adsorption and MWCNT stabilization. The main results are as follows:(1) HAs can adsorb on the surfaces of MWCNTs and consequently enhance the MWCNT stabilization. The stabilization of MWCNTs increased with increasing QSA (MWCNT-surface area-normalized adsorption of HAs), but the increase leveled off when QSA exceeded a threshold value markedly lower than the maximum QSA (QSA-T).It was found that the stabilization of MWCNTs with larger outer-diameters needed less QSA-T.The capability of the MWCNT-adsorbed HAs for the MWCNT stabilization (QSA-normalized MWCNT stabilization) increased with increasing HA polarity and pH but with decreasing Ca2+concentration.(2) The adsorption of PSS on MWCNTs was higher than SS. The adsorption of PSS and SS on MWCNTs could increase the surface negativity of the MWCNTs. MWCNTs were stabilized in2.5mg/L PSS solution, howerve, MWCNTs could not be dispersed and stabilized even in100mg/L SS solution, which were probably correlated with the lack of steric repulsion by SS.