The kinetics and efficiency of UV assisted advanced oxidation of various types of commercial organic dyes in water

Five model solutions formulated from the commercial dyes: C. I. Reactive Black 1 (RB1), C. I. Direct Red 23 (DR23), C. I. Acid Blue 25 (AB25), C. I. Basic Red 1 (BR1) and C. I. Mordant Orange 1 (MO1) were treated by UV-C assisted homogeneous AOPs: UV/Fe(II), UV/H2O2 and UV/Fe(II)/H2O2 (hereafter: UV/Fenton). Dye degradation in acidic medium (pH 3) was evaluated by the decrease in Total Organic Carbon (TOC) content and colour, measured by the decrease in chromophore absorption bands. In comparison to photolysis (UV alone), UV/Fe(II) and UV/H2O2, the highest extents were observed when UV/Fenton process was applied. l experimental conditions were taken from our previous work: 0.5 mM FeSO4·7H2O and 2.5 mM of hydrogen peroxide. Under these experimental conditions, more than 90% of TOC and 100% of colour removal were obtained for AB25 and MO1 dye after 60 min of UV/Fenton. The lowest extents were observed for DR32; only 34% of TOC and 48% of colour removal. lization and decolourization kinetics were modelled according to the comprehensive kinetic model introduced in our previous study [1], taking into account crucial reactions of Fenton catalytic cycle, UV-C induced photolysis and reaction between dye/organic molecule and OH radicals. Direct photolysis was modelled according to semiempirical model based on Lambert–Beerʹs law (LLM). The results were discussed in respect to each dye.