Photocatalytic Degradation of Methyl Orange

A clean, dry reactor with a quartz window was used for MO dye degradation tests. In a typical reaction, the total liquid volume was 45 mL, containing 20 ppm (61 µM) MO concentration and 1 mL of 6% H₂O₂, with 2 mM H₂SO₄ acid used to maintain a medium pH of 3.0. The protonation or deprotonation of the dye is important depending on the mechanistic pathway of degradation and affect the adsorption capacity of the dye to the catalyst [41 (link)]. A 2 × 1 cm² area of the annTNA catalyst film was immersed in the solution facing the quartz window to maximize light absorption. In experiments studying the H₂O₂ effect, the amount of H₂O₂ was varied appropriately. Radical scavengers such as isopropyl alcohol (IPA), formic acid (FA), tertiary butyl alcohol (TBA), and ascorbic acid (AA) were used in an amount equivalent to that of the H₂O₂ in the medium. In a comparative study with other types of titania, 200 mg of powdered TiO₂ catalyst was used, which is equivalent to the Ti content of the immersed annTNA film catalyst. The photoelectrochemical reaction was carried out for up to 60 min at a light intensity of 100 mW cm⁻² irradiated with a solar simulator (ABET Technologies, Milford, CT, USA) equipped with a Xe Arc lamp. Test aliquots of 1 mL were collected at regular intervals, diluted with 2 mL of DI, and tested directly using a UV–Visible spectrometer (Biochrom, Cambridge, UK).