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 (H 2 O 2 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 H 2 O 2 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 FeTiO 3 ). 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 H 2 O 2 systems, respectively, when the initial concentration of TBZ was 37 µM. Pointing out that both pseudo-first order rate constants ( k ′ ),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 H 2 O 2 , thus the capacity of treatment plants can be increased. Furthermore, better results of mineralization (54%), DQO (76%), DBO 5 (44%) and acute toxicity (74%) removal were observed when NaClO was used as an oxidant compared to H 2 O 2 , 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 H 2 O 2 in the heterogeneous photo Fenton like process.