Photodegradation of Methylene Blue Dye in Aqueous Stream Using Immobilized TiO2 Film Catalyst: Synthesis, Characterization and Activity Studies

Abstract

Filem fotomangkin TiO₂ telah berjaya disentesiskan dan tersekat gerak pada reaktor kaca melalui kaedah sol–gel. Lapisan TiO₂ yang berlut–sinar membenarkan penembusan cahaya ultra–ungu (UV) ke atas permukaan mangkin. Reaktor foropemangkinan berbentuk tiub yang mempunyai mod kitar semula telah dibina. Formula sintesis TiO₂ yang baru telah dicadangkan, iaitu 1 titanium isoproposida : 8 isopropanol : 3 asetil aseton : 1.1 H₂O : 0.05 asid asetik (dalam nisbah molar) menunjukkan aktiviti proses berfotomangkin yang tinggi dalam proses penurunan bahan pencemaran metilena biru yang hadir di dalam air. Bagi reaktor fotomangkin yang berbentuk tiub, 5 pusingan kitar semula pada Ï„ = 1.4 min diperhatikan untuk 50% degradasi metilena biru pada kepekatan awal 40 μmol/L. Proses penurunan berfotomangkin didapati tidak peka terhadap perubahan suhu tindak balas. Tenaga pengaktifan bagi metilena biru adalah 10.72 kJ/mol. Dalam kajian ini, kepekatan awal bahan tindak balas, nilai pH, kehadiran hidrogen peroksida, udara dan suhu tindak balas merupakan pembolehubah proses yang dikaji. Pencirian ke atas lapisan TiO₂ dijalankan dengan menggunakan analisis SEM, XRD dan EDX. Analisis SEM menunjukkan lapisan TiO₂ yang serata pada sokongan kaca tanpa kemunculan retakan. Analisis XRD mendedahkan kemunculan fasa kehabluran anatasi TiO₂ pada suhu kalsinasi 500°C dan fasa rutil, fasa kehabluran TiO₂ yang kurang aktif pada suhu melebihi 600°C. Satu kajian perbandingan keaktifan diantara lapisan filem TiO₂ disintesis dan komersial serbuk TiO₂ (99% anatasi) dinilai pada keadaan eksperimen yang sama. Filem TiO₂ didapati sama aktif seperti mangkin serbuk TiO₂. Kata kunci: Film fotomangkin TiO, metilena biru, proses penurunan berfotomangkin, sintesis TiO₂ thin film photo catalyst was synthesized and immobilized on glass reactor through sol–gel method. The synthesized TiO₂ coating was transparent that enabled the penetration of ultra–violet (UV) light to the catalyst surface. A tubular photo–catalytic reactor with recirculation mode was designed, fabricated and used for activity measurements. TiO₂ film was synthesized using the formulation of 1 titanium iso–proproxide : 8 iso–propanol : 3 acetyl acetone : 1.1H₂O : 0.05 acetic acid (in molar ratio) and gave excellent photo–catalytic activity in degradation of methylene blue dye present in aqueous solution. 50% degradation of methylene blue dye at the initial dye concentration of 40 μmol/L was observed after 5 passes of recirculation with residence time of 1.4 min. Photo catalytic degradation of methylene blue dye was insensitive to the increase of reaction temperature. The activation energy for photo degradation of methylene blue dye was 10.72 kj/mol. The initial methylene blue dye concentration, pH value, presence of hydrogen peroxide, air bubbling, and reaction temperature were studied as the important process variables. The synthesized TiO₂ thin photo–film was characterized using SEM, XRD and EDX analysis methods. SEM analysis showed a uniform TiO₂ coating on glass support without fractured appearance. XRD analysis revealed the appearance of anatase TiO₂ crystalline phase at calcination temperature of 500°C and rutile phase, the less active TiO₂ crystalline phase was observed above 600°C. A comparative performance between the TiO₂ thin film and a commercial sample of TiO₂ powder (99% anatase) was evaluated under the same experimental conditions. The synthetic TiO₂ film was found equally active as TiO₂ powder catalyst. Key words: TiO film photo catalyst, methylene blue dye, photo catalytic degradation, synthesized