Highly Efficient catalyst of TiO۲/chitosan for Photodegradation and Sonodegradation of Organic Pollutants

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 TiO۲ to degrade dyes in an effective method. In this research, TiO۲ nanoparticles prepared via sol–gel low-temperature method was successfully immobilized within chitosan and used as heterogeneous catalyst for the degradation of Acid Orange ۷ (AO۷) as an anionic dye. Transmission electron microscopy, scanning electron microscopy, and X-ray diffraction analysis were employed to characterize TiO۲/chitosan catalyst. Photodegradation and sonodegradation of AO۷ by TiO۲/chitosan catalyst has been studied. XRD analysis indicated that prepared samples were ۱۰۰% anatase phase and that chitosan interacted with TiO۲ nanoparticles and possessed good compatibility. TiO۲/chitosan nanocomposite showed high sonocatalytic and photocatalytic activities for the degradation of AO۷. 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 AO۷ via TiO۲/chitosan nanocomposite needs more time. Negative ΔG۰ and ΔH۰ values yielded from thermodynamic investigation proposed that the removal of AO۷ via TiO۲/chitosan nanocomposite was simultaneous and exothermic in nature, respectively.

Keywords:

Sol-gel low-temperature , TiO۲/chitosan nanocomposite , Sonocatalysis , Photocatalysis