Spectroscopic studies of hydrophobic acid with different origins

Hydrophobic acid (HPO-A) was isolated from two surface water samples, two secondary treated effluent samples taken from wastewater treatment plants, as well as two soil samples. Various spectroscopic techniques were employed for the comparison and characterization of HPO-A with different origins, including ultraviolet visible (UV/Vis), Fourier-transform infrared (FT-TR) and fluorescence spectroscopies. The results showed that the UV/Vis absorbance of the six HPO-A generally decreased as the wavelength increased. Both absorption coefficients at 280 nm (A₂₈₀) and at 600 nm (A₆₀₀) followed the order HPO-A from soils > HPO-A from surface waters > HPO-A from secondary treated effluents. A weak relationship existed between A₆₀₀ and the ratio of absorbances at 253 nm (E₂₅₃) and 203 nm (E₂₀₃) of HPO-A. There were no -CH₃ groups in HPO-A from soils. Both HPO-A from surface waters and from soils had greater CO content while HPO-A from secondary treated effluents had greater content of aliphatic compounds. HPO-A from secondary treated effluents contained amides. Humic acid- and fulvic acid- like organics were the predominant fluorescent materials in HPO-A. The content of fulvic acid-like fluorescent materials was relatively high in both HPO-A from surface waters and from secondary treated effluents. The presence or absence of soluble microbial byproduct-like materials in HPO-A, was irrelevant to the origin of HPO-A.