The application of thermally activated persulfate for degradation of Acid Blue 92 in aqueous solution

Abstract

Thermally activated persulfate (TAP) was applied for the degradation of Acid Blue 92 (AB92) dye in its aqueous solution. The effects of pH (3–11), temperature (298–333 K), contact time (15–75 min), sodium persulfate (SPS) concentration (0.05–0.5 mM) and initial AB92 concentration (50–400 mg/L) on the degradation of AB92 using TAP were examined. The initial and residual AB92 concentrations were determined spectrophotometrically at the wavelength of 260 nm and the dye mineralization was examined via the total organic carbon analysis. In addition, the chemical oxygen demand was also measured. The activation energy (Ea) of AB92 degradation was calculated as 17.38 kJ mol−1 based on the Arrhenius equation. Maximum degradation efficiency of 86.47% was reached after 75 min of treatment at a pH of 5, AB92 concentration of 200 mg/L, SPS concentration of 0.5 mM and temperature of 333 K. The degradation efficiency declined with the addition of different sodium chloride concentrations and organic radical scavengers. AB92 degradation was reduced from 86.5 to 74%, 65, and 59.1% using ethylenediaminetetraacetic acid, tert-butanol, and ethanol, respectively. A kinetic model was also developed to estimate the pseudo-first-order constants as a function of the main operational parameters (initial dye concentration and TAP concentration). Decolorization rate constants (k) of 0.0009, 0.001, 0.0012, 0.0014, and 0.0018 min−1 were obtained at 303, 308, 313, 328, and 333 K, respectively, using the Langmuir–Hinshelwood kinetic model. The results obtained indicate that the TAP degradation process has great potential for the reduction of azo dyes in aqueous environments.