Adsorption of hydrophobic organic compounds (HOC) to inorganic surfaces in aqueous solutions
Final Report Abstract
For a better understanding of the sorption process of hydrophobic organic compounds (HOCs) to hydrophilic surfaces in fully submerged aqueous systems, five selected polycyclic aromatic hydrocarbons (PAHs) and four pairs of n- and cycloalkanes (C5 to C8) have been used as chemical probes. Their sorption to different inorganic surfaces (such as borosilicate glass, silica gel, aluminum oxide and titanium oxide) was systematically investigated. The determined sorption coefficients (Kd) at various environmental conditions showed that the solution pH and temperature had no significant effect on the sorption process. The presence of ionic strength could promote the Kd values. However, the increase of Kd values was only found at low ionic strength (for example, concentration of CaCl2 less than 0.005 M), further increasing the ionic strength had no obvious influence on the extent of sorption. Based on the measured Kd values, a linear relationship between Kd and sub-cooled water solubility of PAHs in logarithmic coordinates was found on all investigated inorganic surfaces. Similar slopes obtained from the correlations on all inorganic surfaces suggested that sorption was dominated by the same mechanism and provided a tool to predict sorption behavior of other PAHs to inorganic surfaces. After studying sorption of n- and cycloalkanes to silica gel and aluminum oxide, the conclusion that sorption of hydrophobic organic compounds (HOCs) to inorganic surfaces in aqueous is isothermally linear or nearly linear could be corroborated. By using the ratio of Kn /Kc in the characterization of sorption mode, results suggested that sorption in the water-inorganic surfaces system was dominated by absorption in the vicinal water layer. To measure in-situ the concentration gradient formed near to inorganic surfaces, a highly spatially resolved electrochemical method, scanning electrochemical microscopy (SECM), was applied. The concentration gradient was represented by measuring the change of conductivity in ionic solutions. The conductivity was observed to decrease significantly with increasing distance between 1 to 300 µm. However, a full explanation of this phenomenon needs further investigations.
Publications
- Adsorption of hydrophobic organic compounds to inorganic surfaces in aqueous solution. Wasser 2008, Jahrestagung der Wasserchemischen Gesellschaft. Trier, Germany
Qian, Y., Schmidt, T. C.
- An HPLC-based approach to evaluate adsorption of hydrophobic organic compounds (HOCs) on inorganic surfaces in aqueous solution. 27th International Symposium on Chromatography. 2008, Muenster, Germany
Qian, Y., Schmidt, T. C.
- Adsorption of hydrophobic organic compounds (HOCs) on inorganic surface in aqueous systems. The 25th Annual International Conference on Soils, Sediments, Water and Energy. 2009, Amherst, MA, USA
Qian, Y., Schmidt, T. C.
- Evaluation of the adsorption of hydrophobic organic compounds (HOCs) to inorganic surfaces in aqueous solution by using batch and column method. Wasser 2009, Jahrestagung der Wasserchemischen Gesellschaft. Stralsund, Germany
Qian, Y., Altergott, O., Schmidt, T. C.
- Characterizing the sorption mode to mineral surfaces in aqueous solution by using alkane and cycloalkane probe compounds. Wasser 2010, Jahrestagung der Wasserchemischen Gesellschaft. Bayreuth, Germany
Qian, Y., Posch, T., Jung, L. Schmidt, T. C.
- Sorption of polycyclic aromatic hydrocarbons (PAHs) on glass surfaces. Chemosphere
Qian, Y., Posch, T., Schmidt, T. C.
