Low frequency US and UV-A assisted Fenton oxidation of simulated dyehouse wastewater.

The scope of the present study was to explore the treatment possibilities for the simulated dyehouse wastewater (WW) by the Fenton oxidation ultrasonic (US) or UV-A assisted. Composition of WW included reactive azo dye, C.I. Reactive Violet 2 (RV2), anionic surfactant (LAS) and auxiliary chemicals. An emphasis was put on the influence of the LAS on the treatment efficiency. To explore the pseudo-catalytic effect of LAS and reagent dosages on the extents of decolourization and mineralization, different experimental design techniques were utilized. Box-Behnken design was used as a base for optimization and determination of the influencing factors; numerical (Fe(2+/3+), H(2)O(2) and LAS concentration) and categorical factors (iron oxidation state and type of additional energy; US or UV-A). Furthermore, a mixture design methodology was applied. This two-step optimization approach lead to a single optimal point for two advanced oxidation processes studied in comparison. Models describing the dependency of the overall efficiency on influencing factors were obtained. Application of US/Fe(2+)/H(2)O(2) and UV-A/Fe(2+)/H(2)O(2) processes for the treatment of WW was assessed. Only 26% of mineralization was achieved by Fenton process alone applied for the treatment of the dyehouse effluent in 10-fold dilution, while 43% of mineralization was achieved by US or UV-A assisted Fenton after the 60 min.