Degradation of TMAH treated aquatic humic matter at different temperatures

Abstract

Lake aquatic fulvic acid was investigated with tetramethylammonium hydroxide (TMAH) treatment and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). TMAH treatment was performed as an off-line procedure at 100°C without significant thermochemolytic degradation (ensured with a solvent extraction) and the product distributions at three different pyrolysis temperatures (300, 450 and 600°C) were studied. The degradation of TMAH treated fulvic acid was strongly thermally controlled. The number of degradation products and their total ion currents (TIC) increased significantly when the pyrolysis temperature was raised from 300 to 600°C. Furthermore, the highest temperature yielded significant amounts of aromatic structural constituents (especially alkylmethoxybenzenes) which were not found at lower sub-pyrolysis temperatures. According the results, the utilisation of high temperature pyrolysis of TMAH treated humic matter seems to be needful, because TMAH thermochemolysis is not necessarily enough to split off the most strictly bound aromatic subunits of the heterogeneous humic matter.