Sorption of hydrophobic organic compounds (HOCs) to inorganic surfaces in aqueous solutions Dissertation

Sorption of hydrophobic organic compounds (HOCs) to hydrophilic inorganic surfaces in aqueous systems is an important process, because HOCs are common contaminants and the sorption controls their concentration and rate of transport in the environment. Furthermore, in environmental chemistry and analysis, sorption of HOCs to inorganic surfaces, in particular to untreated (uncoated) glass surfaces, causes the loss of analyte and then confuses subsequent data interpretation. For a better understanding of the process and developing a predictive tool, five selected polycyclic aromatic hydrocarbons (PAHs, naphthalene, fluorene, phenanthrene, anthracene and pyrene) and four pairs of nand cycloalkanes (C5 to C8) have been used as chemical probes. Their sorption behaviors to different hydrophilic inorganic surfaces (e.g. borosilicate glass, silica gel, aluminum oxide and titanium oxide) were systematically investigated. From a practical point of view, glassware is the commonly used container in analysis. Therefore, sorption coefficients (Kd) of five selected PAHs to the frequently used laboratorial glass surfaces (borosilicate glass) were firstly investigated by using column chromatography. The validation of column method was carried out by comparing the data measured in column chromatography to that obtained in batch experiments. After validation, the influence of environmental factors on Kd, such as ionic strength, pH value, co-solvent, coated surface and temperature, were comprehensively studied. Our data revealed that (1) mass loss caused by sorption on glass walls strongly depends on the ratio of solution volume to contacted surface area (V/S) and (2) use of cosolvent or silane coated glass surfaces is often not sufficient to suppress sorption for large PAHs. Based on the successful application of column chromatography in glass surface studies, this method was extended to use in the further investigation of sorption to other mineral surfaces (e.g. silica gel, aluminum oxide and titanium oxide). Sorption coefficients (Kd) were determined under different environmental conditions (i.e. ionic strength, pH value and temperature). In particular, the influence of particle size and pore size, which played an important role for the extent of sorption for porous sorbent, was focused on. In this study, the most important observation is that for porous material, not all the N2-BET determined surface area was effective for sorption in water-mineral systems.