Photocatalytic degradation of methyl blue by silver ion-doped titania: Identification of degradation products by GC-MS and IC analysis

Abstract

An anionic triphenyl methane dye, methyl blue ((disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate) was degraded photocatalytically with undoped micro-TiO₂- and Ag⁺-doped micro TiO₂ in a slurry-type batch reactor under UV irradiation and the efficiency was compared with that obtained using nano-TiO₂- and Ag⁺-doped nano-TiO₂. The influence of different parameters, i.e., photocatalyst loading, dye concentration, initial pH, temperature, depth of solution, interfering ions and electron acceptors on the dye degradation was investigated. The decolorization and mineralization efficiency was better for Ag⁺-doped micro-TiO₂ than undoped micro-TiO_2. Nano-TiO₂ was more efficient than micro-TiO₂, while Ag⁺-doped nano-TiO₂ was the most efficient of all. Cost analysis showed degradation using micro-TiO₂- and Ag⁺-doped micro-TiO₂ are much cheaper than that using nano-TiO₂ and Ag⁺-doped nano-TiO_2. Therefore Ag⁺-doped micro-TiO₂ was used for the detailed study. The degradation products formed were identified using GC-MS analysis after photocatalytic degradation for 180 min with Ag⁺ -doped micro TiO₂. Ion chromatography analysis was carried out for anions to identify the end products of degradation.

Keywords:

• Chromatograph
• cost estimation
• degradation
• GC-MS
• kinetics
• mineralization