Wet air oxidation of linear alkylbenzene sulfonate 1. Effect of temperature and pressure

The semibatch wet air oxidation (WAO) of 1600 mg L-1 of a linear alkylbenze ne sulfonate (LAS) known as sodium dodecylbenzene sulfonate (SDBS) was inve stigated, for varying oxidation temperature from 180 to 240 degreesC and pr essure from 3.05 to 6.55 MPa. The major reaction products identified were l ow-molecular-weight volatile fatty acids (VFAs) such as formic and acetic a cids, sulfonated aromatics, and sulfate. For 120-min WAO at 1.5 MPa oxygen partial pressure, a temperature increase from 180 to 240 degreesC led to in creases in the liquid-phase LAS removal from 79 to 100%, in the COD removal from 23 to 70%, and in the desulfonation of the LAS molecule from 7.4 to 5 7% of the total theoretical sulfate. Increasing the overall oxidation press ure from 3.05 to 6.55 MPa had little effect on the overall TOC and COD degr adation, but increased the desulfonation. On the basis of these results, a reaction mechanism is proposed. Sulfonated aromatic WAO intermediates accum ulated under the conditions used, indicating that, to achieve further organ ic degradation, more effective desulfonation conditions will be required.