Surface response methodology for optimizing the degradation kinetics and efficiency removal of sulfamethazine in a UV/S2O8 2- oxidation process.

In this study, a comparison of two advanced oxidation treatments (UV/H2O2 and UV/S2O8 2-) for the degradation of Sulfamethazine (SMT) is presented. A Box-Behnken experimental design was used to assess the effect of different oxidation process variables on degradation efficiency and degradation rate, such as: process temperature, oxidizing agent concentration and pH. Surface response methodology was used to find the best operating conditions of both systems, where the maximum degradation rate and the maximum degradation efficiency were achieved. Under these optimum conditions, similar degradation efficiencies (>99%) were obtained in both systems. The UV/S2O8 2- system showed shorter treatment times than the UV/H2O2 system. A maximum SMT degradation rate (k) of 0.8056 min-1 was obtained for UV/S2O8 2- system, which was almost three times more than the maximum rate observed in UV/H2O2 system (k = 0.3181 min-1) when using the same photocatalytic conditions. The energy consumption obtained for UV/S2O8 2- system under optimum conditions (EEO = 0.402 kWhm-3 order-1) was lower compared to UV/H2O2 process. Based on EEO, this UV/S2O8 2- process could be classified as an AOP-like process and demonstrated a better performance than other alternatives for SMT removal reported in the literature.