Simulating And Predicting Adsorption Of Organic Pollutants On Single-walled Carbon Nanotubes In Water

Carbon nanotubes (CNTs) are considered to be good adsorbents to remove organic pollutants from water. However, adsorption by CNTs may affect the transformation, transport, and fate of pollutants and CNTs in the environment. Thus understanding the adsorption mechanism and capacity of organic pollutants on CNTs is of crucial importance for exploring the application of CNTs and assessing the ecological risks of both CNTs and pollutants.Based on density fuctional theory, Dmo13 module in Materials Studio 4.3 was used to simulate the interaction between (10,0) single-walled carbon nanotube (SWNT) with 20 different organic chemicals (including aliphatic, aromatic and substitutied aromatic chemicals) and calculate binding energies. The results showed that organic chemicals adsorption on SWNT were physical adsorption. The calculated binding energies increased in the order of substituted aromatic hydrocarbon> aromatic hydrocarbon> aliphatic chemicals. As for aromatic compounds, their binding energies increased with the donor ability or withdrawing ability of fuctional groups. Along with conductor-like screening model (COSMO), adsorption of organic chemicals on SWNT was investigated in different solvent (n-hexane, acetonitrile, acetone, water). The results indicated that solvent weakened the interaction. The bigger the dielectric constant was, the larger the influence was.According to the possible adsorption mechanism, a model to estimate the Freundlich adsorption coefficient was developed by partial least square regression. The final predictive model included three parameters:binding energy of SWNT and chemical in water, molecular volume and n-decahexane/water partition coefficient. The model had good goodness-of-fit with a squared correlation coefficient R2 of 0.926 and good robustness and predictivty (cumulative Q2 of 0.861 and root mean square error of 0.083 log units). The applicability domain was defined as Hotelling T2 method. Mechanisms governing organic chemical adsorption on SWNT wereπelectron involved interaction (CH-πinteraction andπ-πinteraction), van der Waals force and hydrophobic force, the former two of which were the most significant mechanisms for the studied chemicals. The developed model has good performace and clear mechanism interpretation, thus it can be used to predict the adsorption ability of organic chemicals on SWNT and then provide fundamental data for environmental risk assessment for CNTs and organic chemicals.