Sunlight-Driven AO7 Degradation with Perovskites (La,Ba)(Fe,Ti)O3 as Heterogeneous Photocatalysts.

Ana Sofia Rodrigues,Sandra Mogo,Annabel Fernandes,Maria José Pacheco,Lurdes Ciríaco,Ana Lopes

doi:10.3390/nano11113142

Ana Sofia Rodrigues, Sandra Mogo + Show 4 more

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https://doi.org/10.3390/nano11113142

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Abstract

Perovskites of the (La,Ba)(Fe,Ti)O3 family were prepared, characterized, and utilized as heterogeneous photocatalysts, activated by natural sunlight, for environmental remediation of Acid Orange 7 (AO7) aqueous solutions. Catalysts were prepared by the ceramic (CM) and the complex polymerization (CP) methods and characterized by XRD, SEM, EDS, and band gap energy. It was found that catalytic properties depend on the synthesis method and annealing conditions. In the photocatalytic assays with sunlight, different AO7 initial concentrations and perovskite amounts were tested. During photocatalytic assays, AO7 and degradation products concentrations were followed by HPLC. Only photocatalysis with BaFeO3-CM and BaTiO3-CP presented AO7 removals higher than that observed for photolysis. However, photolysis leads to the formation of almost exclusively amino-naphthol and sulfanilic acid, whereas some of the perovskites utilized form less-toxic compounds as degradation products, such as carboxylic acids (CA). Partial substitution of Ba by La in BaTiO3-CM does not produce any change in the photocatalytic properties, but the replacement of Ti by Fe in the La0.1Ba0.9TiO3 leads to reduced AO7 removal rate, but with the formation of CAs. The best AO7 removal (92%) was obtained with BaFeO3-CM (750 mg L−1), after 4 h of photocatalytic degradation with solar radiation.

Highlights

Photocatalytic oxidation technology has high potential for the degradation of the wastewater’s organic load due to its high efficacy and energy-saving advantages, wide application range, and no secondary pollution [1,2,3]
Regarding BaTiO3 crystallite size, it increases with the annealing temperature, and it is higher for complex polymerization (CP), probably because the rearrangement of the ions in the perovskite structure is facilitated by the increase in temperature and because the use of the CP method involves a much more fluid medium for the powder’s preparation
Several perovskite powders were tested for their catalyst ability in suspension under sunlight for Acid Orange 7 (AO7) photodegradation

Summary

Introduction

Photocatalytic oxidation technology has high potential for the degradation of the wastewater’s organic load due to its high efficacy and energy-saving advantages, wide application range, and no secondary pollution [1,2,3]. Perovskite oxides, with high structural stability even under aggressive conditions, a flexible chemical composition, and elemental abundance, are regarded as promising catalysts for many different reactions [5,6,7,8]. They are a class of compounds presenting the general formula ABO3 , where A is an alkali or alkaline earth metal or a member of the lanthanides’ family and B a transition metal [5,9].

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