Diatomite/silver phosphate composite for efficient degradation of organic dyes under solar radiation
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Bull Mater Sci (2020) 43:295 https://doi.org/10.1007/s12034-020-02269-2
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Diatomite/silver phosphate composite for efficient degradation of organic dyes under solar radiation SANOSH KUNJALUKKAL PADMANABHAN*, SUDIPTO PAL and ANTONIO LICCIULLI Department of Engineering for Innovation, University of Salento, Lecce 73100, Italy *Author for correspondence ([email protected]) MS received 5 May 2020; accepted 24 July 2020 Abstract. In this study, an effort has been made to synthesize diatomite/silver phosphate (DT/AgP) composites and dye degradation test was carried out to evaluate the photocatalytic activity under solar light irradiation. Diatomite–silver phosphate composites with different DT/AgP ratios were prepared by precipitation of Ag3PO4 on diatomite that led to the formation of small Ag3PO4 particles on the diatomite surfaces. UV–visible diffuse reflectance analysis shows that DT/ AgP composites can absorb visible wavelength, whereas TiO2 catalyst only work under UV irradiance. Compared to pure AgP, the composite samples show higher specific surface area measured by Brunauer–Emmett–Teller analysis. Dye degradation test under solar light irradiation reveals that the photocatalytic reaction follows a pseudo-first-order rate law and the composite catalyst with DT/AgP ratio 1:0.8 shows better catalytic activity towards both rhodamine B and methyl orange degradation. As reference, a well-known commercial TiO2 (Evonik-P25) was used in dye degradation test. It could be presumed that deposition of silver phosphate clusters (Ag3PO4, AgP) on diatom frustules (diatomite) provided an efficient photocatalyst activated by solar light irradiation. Keywords.
1.
Ag3PO4; diatomite; solar photocatalysis; dye degradation.
Introduction
There has been many efforts to develop visible light photocatalysts for the remediation of air and water pollution [1–3]. Many candidates such as inorganic, molecular, and organic/inorganic hybrid materials, have been explored to meet specific requirements in photocatalytic reaction [4,5]. Among them, some semiconductors exhibit high photocatalytic activities towards decomposing organic pollutants, CO2 reduction as well as splitting water into hydrogen and oxygen for clean energy production [6]. Undoubtedly, TiO2 is the most popular photocatalyst developed till now, however, it only absorbs ultraviolet light (3–5% of entire solar spectrum) due to higher band gap (3.2 eV) limiting its applicability [7]. Recently it has been discovered that, silver orthophosphate (Ag3PO4) exhibits high photo-oxidative properties for generating O2 from water and the degradation of organic pollutants under visible-light irradiation due to the efficient separation of photoexcited electrons and holes [8]. Ag3PO4 has a band gap of 2.45 eV and under visible light irradiation, its quantum efficiencies achieve up to nearly 90% at wavelengths greater than 420 nm, which is significantly higher than that of other semiconductors [9,10]. However, the conversion of Ag? into
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