Kinetics studies on photodegradation of methyl orange in the presence of C-N-codoped TiO2 catalyst

Abstract

This work investigated the photodegradation of azo dye, methyl orange, without and with the addition of C-N-codoped TiO2 catalyst using a visible halogen-lamp as a light source. C-N-codoped TiO2 was prepared by free-organic solvent peroxo sol-gel method. The effects of initial dye concentration, catalyst dosage, and pH solution on the photodegradation of methyl orange were studied. Photodegradation process for methyl orange solution at acidic condition showed high removal percentage. 5 mg L-1 methyl orange achieved color removal until 94% for 180 min irradiation in photodegradation process with the presence of C-N-codoped TiO2 catalyst, and approximately 70% TOC removed as the results of mineralization process. The kinetics reaction rate of photodegradation of methyl orange dye with the addition of C-N-codoped TiO2 followed pseudo-first order represented by Langmuir-Hinshelwood model, the kinetics constant of photodegradation became higher by decreasing the initial concentration of methyl orange. Three organic byproducts of methyl orange formed during photodegradation process was identified by LC-MS/MS system then degradation pathway of methyl orange photodegradation in the presence of C-N-codoped TiO2 catalyst was proposed.