Abstract
In this work, heterostructured catalyst Al2TiO5/TiO2 (ATO/Ti) was synthesized by a two-step method: low-temperature sol-gel process along with hydrothermal treatment in a neutral medium. Characteristics of the fabricated catalyst were analyzed by various techniques including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption, UV-Vis diffuse reflectance spectroscopy, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and the point of zero charges. The content of ATO strongly affected the activity of ATO/Ti catalysts for photocatalytic degradation of cinnamic acid (CA). The catalyst, in which 33% TiO2 was replaced by ATO (33ATO/Ti), exhibited the highest activity for the removal of CA. Compared with the bare titanium oxide synthesized in water (TiO2(w)) as well as Al2TiO5 (ATO), the hybrid 33ATO/Ti catalyst exhibited the enhanced photocatalytic activity in the CA degradation under ultraviolet light. The enhancement in the catalytic activity of ATO/Ti could be related to the increase of the specific surface area and the reduction of bandgap energy obtained from the hybridization of TiO2(w) and ATO. The factors as the catalyst dosage ( C cat ), the airflow rate ( Q air ), and the solution initial pH (pH) affected the CA removal efficiency were studied on 33ATO/Ti catalyst. The optimum condition for photodegradation efficiency of CA was found to be at C cat = 0.75 g L − 1 , Q air = 0.3 Lmi n − 1 , and pH = 3.8 . The highest 60-minute removal efficiency of CA reached 77.1% on 33ATO/Ti compared with 67.1% and 30.4% on TiO2(w) and on ATO, respectively. The recyclability of the 33ATO/Ti was also measured at the optimal parameters. The results showed that, compared with TiO2, the hybrid catalyst was easier to recover and reuse, and its activity decreased by 35% after 6 continuous cycles.
Highlights
Phenolic compounds are a member of the largest groups of environmental pollutants as gallic acid, protocatechuic acid, vanillic acid, syringic acid, and cinnamic acid
TiO2 only existed in the anatase phase on ATO/Ti catalysts, whereas there was an existence of anatase (A) and rutile (R) phases on ATO/Ti(a) samples
In comparison with the X-ray diffraction (XRD) pattern of bare ATO [22], the intensity of the characteristic peaks of ATO became weaker after hybridization with TiO2(w), which may due to the poorer crystallinity [26]
Summary
Phenolic compounds are a member of the largest groups of environmental pollutants as gallic acid, protocatechuic acid, vanillic acid, syringic acid, and cinnamic acid. They were widely used in the agroindustrial wastewaters from cork, olive oil mills, and wine distilleries as well as antimicrobial agents [1, 2]. The presence of the remaining phenolic in the water has been considered as priority pollutants due to their high toxicity for human health and nonbiodegradability on the environment at the extremely low concentration [3]. Titanium oxide has been considered as a conventional photocatalyst and attracted attention in photocatalytic applications thanks to its low cost, high stability, and environmentally friendly semiconductor [4]. Perovskites were evaluated as potential semiconductors in photocatalytic reactions under UV and visible lights based on low bandgap energy and good
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