Transmission ft‐ir difference spectroscopic characterization of a fulvic acid from weathered coal in water

Abstract

Transmission FT‐IR difference spectroscopy has clearly revealed that a well‐characterized fulvic acid from weathered coal can exist in water as micelles or solutions. When the fulvic acid exists as micelles, it is strongly bound to some water molecules and thus there are only a few of inherent, poor‐resolved broad bands in the corresponding IR specra. However, when the fulvic acid is truely dissolved in water, the resolution of the IR spectra can be greatly improved with the help of second‐derivative technique and then some detailed information concerning the composition and structure of the fulvic acid can be extracted. Further, when H‐bonding and other interactions among molecules have weakened to a large extent, the hidden peaks assigned to aromatic C‐H stretch vibration can be clearly observed. Based on these novel results, this paper emphasizes the necessity and advantage of directly determining IR spectra of humic substances in water.