Effect of operating conditions and interfering substances on photochemical degradation of a cationic surfactant

ABSTRACT

This work investigates the degradation kinetics of a recalcitrant organic pollutant, cetyltrimethylammonium bromide (CTAB), using direct UV and UV–H₂O₂ advanced oxidation processes. Direct photolysis at 253.7 nm showed only 55% degradation up to fluence dose of 40.65 J/cm² for an initial CTAB concentration of 100 mg/L. The apparent fluence-based pseudo-first-order rate constant and quantum yield were 2.29(±0.325) × 10⁻⁵ cm²/mJ and 0.305(±0.043) mol/Einstein, respectively. In case of UV–H₂O₂, >99% degradation was observed up to a fluence dose of 0.79 J/cm². The rate constant was ∼200 times higher compared to direct photolysis, which was due to hydroxyl radical generation in the UV–H₂O₂ process. The second-order hydroxyl radical rate constant for CTAB was found to be 1.59(±0.18) × 10⁹ M⁻¹ s⁻¹. The effects of H₂O₂ dose, initial CTAB concentration and relevant water quality parameters (pH, alkalinity and nitrate concentrations) were studied; all of these influenced the rate constants. CTAB degradation was also examined in the municipal wastewater matrix. It is concluded that UV–H₂O₂ represents an efficient treatment process for CTAB in environmental matrices.

KEYWORDS:

• Advanced oxidation
• CTAB
• kinetics
• UV
• scavenging effect

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Bijoli Mondal acknowledges the institute scholarship support received from the Ministry of Human Resources and Development, Govt. of India.