| Abstract
| - Sodium dodecyl (lauryl) sulfate (SDS), an important anionic surfactant used in a variety of textileand biotechnology operations, frequently ends up in stationary water bodies where it promotesthe formation of blue-green algae, an environmentally offensive species. The catalytic wetoxidation of SDS has been studied over alumina-supported cobalt−zinc oxide catalysts underrelatively mild conditions of pressure (<1.3 MPa) and temperature (403−448 K). Five catalystcompositions examined showed a decreasing total (BET) surface area with increasing ZnO loadingsuggesting possible loss of surface area as a result of the formation of a zinc aluminate phaseduring calcination at 923 K. Catalytic activity also decreased with addition of ZnO; however, a15 Co/5 Zn/ 80 δ-alumina catalyst exhibited the most superior performance. Total degradationof the organic substrate could be achieved in about 5 h. The kinetics of SDS autoxidation onthis catalyst revealed a first-order dependency on both the dodecyl sulfate concentration andthe O2 partial pressure. The observed increase in acidity of the reaction medium with SDSconversion paralleled the production of SO42- or (HSO4-) species. Indeed, the rate of sulfateproduction followed the same kinetics with SDS degradation albeit with different estimates ofthe 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 plateauat high O2 partial pressure (>900 kPa). A temperature-dependent expression for the degree(extent) of mineralization, α, in terms of the activation energy for SDS degradation and TOCoxidation was derived as α = 1.43 × 10-2 e1503.8/T, valid between 403 and 473 K. A mechanismwas also proposed to explain the oxidative degradation of SDS.
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