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The photodegradation of methyl orange (MO) was studied with ZnO as a photocatalyst under UV irradiation. Solutions of MO of 10 and 500 ppm were prepared for photocatalytic degradation. Three different wavelengths (254, 302, 365 nm) were used for the photocatalysis of solutions of MO. The experimental results show that the solution of 10 ppm of MO after 2 hours under UV light irradiation was completely decolourised with 20.7 mg of ZnO photocatalyst. While the solution of MO 500 ppm after 6 hours of illumination was not ecolourised considerable using 1.5 g ZnO photocatalyst. Particular attention was devoted in the pathways of the photocatalytic reaction of MO when exposed to UV light at three different wavelengths (254, 302, 365 nm). The samples collected during the photodegradation of MO 10 ppm were analysed by using HPLC-UV at 466 nm. The experimental results demonstrated that the photodegradation of MO 10 ppm at different wavelengths (254, 302 and 365 nm) followed the same pathway, but in different photodegradation rate. Whereas the samples of MO at 500 ppm collected during the photocatalytic reaction were analysed by mass HPLCMS.

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Pedro Kuende, Júlio Honório
Júlio Honório Pedro Kuende - Nationality: Angolan, MSc in Analytical Chemistry in 2017 at University of Huddersfield; BSc (Hons) Chemistry in 2010 at Agostinho Neto University; from 2012 till present - Assistant Lecturer at ISPTEC, Angola.

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