Application of nanostructured aluminium titanate (Al2TiO5) photocatalyst for removal of organic pollutants from water: Influencing factors and kinetic study

Abstract

In this study, aluminum titanate (Al2TiO5)-based nanostructure with the outstanding photocatalytic performance was prepared via the simple citrate sol-gel method. The effects of thee operational variables such as pH, temperature, catalyst dosage, and initial dye concentration on the photodegradation efficiency of methylene blue (MB) were explored in some details. The results showed that compared to TiO2, AT benefits a superior photocatalytic activity due to its narrow band gap (2.88 eV) and low recombination rate of charge carriers. Increasing the wastewater temperature from 25 to 60 °C can improve the degradation percent from 22.15 to 52%. Based on the thermokinetic calculations, the Arrhenius activation energy, ΔH, and ΔS values were also estimated as +24.69 kJ mol−1, 21.78 J mol−1, and 222.48 J K−1.mole−1, respectively. According to the Langmuir-Hinshelwood kinetic model, the photocatalyst follows a first-order equation in a wide range of temperatures. In addition, escalating the pH value from 4 to 9.5 may noticeably enhance the photodegradation efficiency from 7.1 to 46.6%. The enhanced photocatalytic activity at alkaline media was mainly attributed to the excessive generation of hydroxyl ions, improved adsorption of cationic dye on the catalyst surfaces, and effective separation of involved charge carriers. The maximum performance was obtained for the AT dosage of 20 mg/lit and MB concentration of 2.5 mg/lit. Finally, the recycling experiments after 6 runs verified the high stability of the photocatalyst.