Comparison of Sorption Energetics for Hydrophobic Organic Chemicals by Synthetic and Natural Sorbents from Methanol/Water Solvent Mixtures

摘要

Reversed-phase liquid chromatography (RPLC) was used to investigate the thermodynamics and mechanisms of hydrophobic organic chemical retention from methanol/water solvent mixtures. The enthalpy-entropy compensation model was used to infer that the hydrophobic sorptive mechanisms were different for polycyclic aromatic hydrocarbons (PAHs) and monohalobenzenes compared with alkylbenzenes in methanol/water RPLC systems. The estimated compensation temperatures beta for the two retention mechanisms were essentially independent of the organic cosolvent content (35-80% methanol by volume) and RPLC chain length (C-2-C-8). Sorption of four PAHs by Webster surface soil from 30/70 methanol/water solution at three temperatures was measured by the batch equilibration technique. A beta value of 506 K was calculated by using these data and was within the range of beta values estimated from the RPLC data (471-762K). This suggests that the sorptive mechanisms were similar for PAH retention by the RPLC sorbents and the Webster soil from the binary mixed solvent.