Degradation of surfactant SLS in water by singlet oxygen generated by the reaction between hydrogen peroxide and hypochlorite

• Published in: Water science & technology. Water supply 2012-01, Vol.12 (6), p.810-817
• Main Authors: CESAR TEIXEIRA, Luiz Alberto, DE FARIA GARDINGO, Mariana, YOKOYAMA, Lidia, DA FONSECA ARAUJO, Fabiana Valeria
• Format: Article
• Language: English
• Subjects: Anions; Applied sciences; Buildings. Public works; Degradation; Empirical equations; Exact sciences and technology; Hydrogen peroxide; Mathematical models; Oxidants; Oxidation; Oxidizing agents; Oxygen; pH effects; Reaction time; Singlet oxygen; Sodium; Sodium dodecyl sulfate; Sodium lauryl sulfate; Surfactants; Water supply. Pipings. Water treatment
• ISSN: 1606-9749; 1607-0798
• DOI: 10.2166/ws.2012.057

The synergistic aqueous combination of hydrogen peroxide and hypochlorite which results in the formation of the highly oxidizing intermediate species singlet oxygen (1O2) was effective in the degradation of the anionic surfactant sodium lauryl sulphate (SLS) in water. The process was effective in the near neutral pH range of 6–8, and up to initial SLS concentration values of 10 mg/L. For initial [SLS] = 5 or 10 mg/L, pH = 6–8, and excess molar ratio ([H2O2] + [NaClO])/[SLS] = 5:1 it was possible to achieve a final concentration of [SLS] < 0.5 mg/L (95% degradation) in t = 60 min at 25 °C in a batch reaction. By comparison, the same reaction with either of the separate oxidants (only H2O2 or only NaClO) at the same excess molar ratio oxidant/SLS of 5:1 gave a maximum of about 50% degradation of the SLS over the same 60 min reaction time. An empirical rate equation was derived: −d[SLS]/dt = k[SLS]0.8([H2O2] + [NaClO])0.3, with k = 4.8 (±1.0) × 10–1 L/mol s at 25 °C.