Solutions of Acid Red 1 and Acid Red 114 were treated in H2
O2
-modified subcritical water in the
temperature range of 100°C–200°C for up to 60 min. Response surface methodology based on the
Box-Behnken design was used to optimize the process. For Acid Red 1, optimum decolorization of
97% can be achieved at 192°C, 181 mM H2
O2
, 51.3 min treatment time, and 121 mg/L dye concentration. For Acid Red 114, the optimum conditions were 195°C, 157 mM H2
O2
, 38 min treatment time and
110 mg/L dye concentration, where 91% decolorization could be obtained from the proposed model.
It was determined that temperature is the most important factor, followed by the oxidant concentration. Degradation was less efficient for AR114 due to the double azo bonds, compared to the single
azo bond of AR1. Application of the optimum treatment conditions on real reactive dye wastewater
resulted in 92.7, 79.1 and 20.4% removal of BOD5
, COD and TSS, respectively.