Document Type : Research Article
Department of Chemistry, Payame Noor University, PO box 19395-3697, Iran
In the last decades, wastewater from the textile industry has become a major problem which leads to increase the concentration of pollution, which in turn represents environmental risks. The presence of dyes at even very low levels in effluent is highly visible and decomposition materials of these textile dyes are often carcinogenic. Due to the complex nature of synthetic dyes, conventional biological treatment processes are ineffective. Therefore there is a need of developing treatment methods that can lead to the complete degradation of the dye molecules from waste stream. Over the last few years, advanced oxidation processes (AOPs), especially sonocatalysis and photocatalysis, have proven to be effective processes for the wastewater treatment. The current study focused to develop a catalytic reactor via immobilized TiO2 to degrade dyes in an effective method. In this research, TiO2 nanoparticles prepared via sol–gel low-temperature method was successfully immobilized within chitosan and used as heterogeneous catalyst for the degradation of Acid Orange 7 (AO7) as an anionic dye. Transmission electron microscopy, scanning electron microscopy, and X-ray diffraction analysis were employed to characterize TiO2/chitosan catalyst. Photodegradation and sonodegradation of AO7 by TiO2/chitosan catalyst has been studied. XRD analysis indicated that prepared samples were 100% anatase phase and that chitosan interacted with TiO2 nanoparticles and possessed good compatibility. TiO2/chitosan nanocomposite showed high sonocatalytic and photocatalytic activities for the degradation of AO7. The rate constant of sonocatalysis was higher than that of photocatalysis. Sonocatalytic degradation of organic dye using prepared nanocomposite could be described by the mechanisms of hot spots and sonoluminescence. Furthermore, the photocatalytic degradation of AO7 via TiO2/chitosan nanocomposite needs more time. Negative ΔG0 and ΔH0 values yielded from thermodynamic investigation proposed that the removal of AO7 via TiO2/chitosan nanocomposite was simultaneous and exothermic in nature, respectively.