Assessment of the Use of NaClO as an Alternative to H2O2 in the Oxidant-Titanium Ore-Simulated Solar Light System for Thiabendazole Degradation

Abstract

The use of the magnetic fraction (MF) of a low-grade titanium ore (TO) and two oxidants (H2O2 and NaClO), testing each one separately, were compared in photo-Fenton like systems to degrade thiabendazole (TBZ) as a model micropollutant. As far as the author’s knowledge goes, this work presents for the first time the assessment of NaClO as an alternative to H2O2 in heterogeneous systems, where the Fenton-type photocatalyst is a natural mineral; TO has a Mexican origin and its magnetic fraction is mainly composed of Ilmenite (47.8% w/w FeTiO3). The experiments were carried out at bench scale in a solar simulator, using a batch raceway pond reactor. Oxidant and MF concentrations were optimized by a composite experimental design, which allowed to achieve 97% TBZ degradation at 15 and 30 min for NaClO and H2O2 systems, respectively, when the initial concentration of TBZ was 37 µM. Pointing out that both pseudo-first order rate constants ( $$k^{\prime}$$ ), $$k_{NaClO}^{^{\prime}}$$ = 0.226 min−1 and $$k_{{H_{2} O_{2} }}^{^{\prime}}$$ = 0.065 min−1, are in the order of homogeneous photo-Fenton applied to degrade TBZ; however, the time to achieve the same level of TBZ degradation is halved when NaClO is used instead of H2O2, thus the capacity of treatment plants can be increased. Furthermore, better results of mineralization (54%), DQO (76%), DBO5 (44%) and acute toxicity (74%) removal were observed when NaClO was used as an oxidant compared to H2O2, whose values were 42, 67, 38 and 58% for the parameters aforementioned. These positive results demonstrate the feasibility of the use of NaClO as an alternative oxidant to H2O2 in the heterogeneous photo Fenton like process.