Water Treatment Combined Chlorine (Monochloramine) Degradation using Direct Photolysis and Homogeneous Photocatalysis (UV/H2O2, UV/NaOCl) with a Medium Pressure (MP) Lamp as a Source of UV

Abstract

Abstract The objective of this study is to investigate the use of photochemical systems (photolysis, H2O2/UVMP and NaOCl/UVMP) to deplete monochloramine compound with a medium pressure lamp as an irradiation source (200–600 nm). First, it was found that the direct photolysis treatment was a suitable method to degrade the given compound and that this degradation was greatly enhanced by H2O2/UVMP. This could be attributed to radical •OH produced in great amount by the photolysis of H2O2. However, no big advantages were observed when we used NaOCl/UVMP system. Indeed, this process generated radical •OH (but in feeble amount) and also radical Cl• (to form chloramins) and leading consequently to a less degradation rate comparatively to that obtained with H2O2/UVMP. This could be explained by a competition between the two species: •OH and Cl• for the compound. In addition, kinetics data for the three systems were best represented by a pseudo-first-order model and the photodecomposition of NH2Cl has led to the formation of nitrite, nitrate without forming ammonia. It is essential to mention that •OH radicals produced from H2O2/UVMP and NaOCl/UVMP was detected by a photoluminescence (PL) technic using terephthalic acid (TA) as a probe molecule.