Photodegradation of New Methylene Blue N in Aqueous Solution Using Zinc Oxide and Titanium Dioxide as Catalyst

Abstract

Dalam kajian ini, ZnO dan TiO2 digunakan sebagai fotomangkin dalam pendegradasian pewarna New Methylene Blue N (NMBN). Kadar fotodegradasi diukur menggunakan alat spektrofotometer UV-Vis. Dalam kajian ini, New Methylene Blue N menunjukkan nilai serapan pada λ = 590 nm dan λ = 286 nm. Lampu UV (λ = 354 nm) digunakan dalam proses fotodegradasi. Dalam proses degradasi menggunakan ZnO menunjukkan 81.42% NMBN terdegradasi pada λ = 590 nm dan 77.75% pada λ = 286 nm. Sebaliknya, degradasi menggunakan TiO2 adalah 25.68% pada λ = 590 nm dan 26.37% pada λ = 286 nm. Peratus degradasi New Methylene Blue N ialah 88.89% dan 68.94% pada masing-masing λ = 590 nm dan λ = 286 nm apabila ditambahkan dengan H2O2. Campuran ZnO dan TiO2 dalam nisbah 85: 15 (0.085 g; 0.015 g) merupakan campuran fotomangkin yang paling optimum iaitu dengan peratus degradasi NMBN sebanyak 96.97% dan 93.61% pada λ = 590 nm dan λ = 286 nm. Penambahan ion logam Cu2+ memberikan peratus degradasi tertinggi berbanding ion logam lain iaitu 83.83% pada λ = 590 nm. Penambahan ion logam Pb2+ memberikan peratus degradasi tertinggi pada λ = 286 nm iaitu 81.25% pewarna terdegradasi. Keadaan optimum dicapai pada pH 5.90, dengan peratus degradasi tertinggi iaitu 92.84% dan 89.30% pada masing-masing λ = 590 nm dan λ = 286 nm. Kata kunci: New Methylene Blue N; fotodegradasi; larutan; ZnO; TiO2 In this study, ZnO and TiO2 are used as photocatalyst to degrade the dye, New Methylene Blue N (NMBN). The photodegradation rate was measured using UV-Visible spectrophotometer. In this study, New Methylene Blue N showed absorption values at λ = 590 nm and λ = 286 nm. UV lamp (λ = 354 nm) is used in the photodegradation process. Results showed that ZnO is a better photocatalyst compared to TiO2. The degradation by ZnO showed that 81% of NMBN was degraded at λ = 590 nm and 77.75% at λ = 286 nm. In contratst, the degradation using TiO2 was 25.68% at λ = 590 nm and 26.37% at λ = 286 nm. The percent degradation of New Methylene Blue N is 88.89% and 68.94% at λ = 590 nm and λ = 286 nm respectively when H2O2 was added. A mixture of ZnO and TiO2 in the ratio of 85: 15 (0.085 g: 0.015 g) is the most optimum ratio for the mixed photocatalyst where the degradation percentage of NMBN are 96.97% and 93.61% at λ = 590 nm and λ = 286 nm. The addition of Cu2+ metal ion gave the highest percentage of degradation (83.83% at λ = 590 nm) compared to other metal ions. The addition of Pb2+ gave the highest percentage of degradation at λ = 286 nm with 81.25% degradation of the dye. The optimum condition was achieved at pH 5.90, which gave the highest percentage degradation, 92.84% and 89.30% at λ = 590 nm and λ = 286 nm respectively. Key words: New Methylene Blue N; photodegradation; aqueous; ZnO; TiO2