Sodium dodecyl (lauryl) sulfate (SDS), an important anionic surfactant used in a variety of textile and biotechnology operations, frequently ends up in stationary water bodies where it promotes the formation of blue-green algae, an environmentally offensive species. The catalytic wet oxidation of SDS has been studied over alumina-supported cobalt-zinc oxide catalysts under relatively mild conditions of pressure (<1.3 MPa) and temperature (403-448 K). Five catalyst compositions examined showed a decreasing total (BET) surface area with increasing ZnO loading suggesting possible loss of surface area as a result of the formation of a zinc aluminate phase during calcination at 923 K. Catalytic activity also decreased with addition of ZnO; however, a 15 Co/5 Zn/ 80 δ-alumina catalyst exhibited the most superior performance. Total degradation of the organic substrate could be achieved in about 5 h. The kinetics of SDS autoxidation on this catalyst revealed a first-order dependency on both the dodecyl sulfate concentration and the O 2 partial pressure. The observed increase in acidity of the reaction medium with SDS conversion paralleled the production of SO 4 2or (HSO 4 -) species. Indeed, the rate of sulfate production followed the same kinetics with SDS degradation albeit with different estimates of the pseudo-first-order rate constants. Independent measurement of the total organic carbon (TOC) oxidation rate also showed a linear correlation with SDS concentration but attained a plateau at high O 2 partial pressure (>900 kPa). A temperature-dependent expression for the degree (extent) of mineralization, R, in terms of the activation energy for SDS degradation and TOC oxidation was derived as R ) 1.43 × 10 -2 e 1503.8/T , valid between 403 and 473 K. A mechanism was also proposed to explain the oxidative degradation of SDS.
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