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Keywords
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Photocatalyst, Gd-doped Ag3PO4, Crystalline defect, Kinetic model, Anthraquinone dye, Byproducts
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Abstract
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tGadolinium (Gd)-doped silver orthophosphate (Ag3PO4) nanoparticles, with spherical morphology, weresynthesized by a co-precipitation method and their photocatalytic activities were evaluated in degrada-tion of Reactive Blue 19 (RB19), as a model organic pollutant. The synthesized Ag3PO4and Gd-dopedAg3PO4were characterized using X-ray diffraction pattern analysis, scanning electron microscopy,energy-dispersive X-ray spectroscopy, transmission electron microscopy, diffuse reflectance UV–visspectroscopy and photoluminescence spectroscopy. In comparison with Ag3PO4, the experimental resultsrevealed a considerable enhancement in photocatalytic activity of Gd-doped Ag3PO4. The optimum molefraction of Gd loading in Ag3PO4was 3%. Lower photocatalytic degradation efficiency of RB19 in thepresence of oxalate anion and p-benzoquinone indicated the crucial role of photogenerated holes andsuperoxide anion-radicals in photocatalysis on Gd-doped Ag3PO4. The enhancement of photocatalyticactivity was attributed to scavenge the photoexcited electrons, and to suppress their recombination withholes and generation of active oxygen species. A nonlinear empirical kinetic model was introduced to pre-dict the apparent first order rate constant (kapp) as a function of operational parameters, including initialRB19 concentration, Gd-doped Ag3PO4dosage and light intensity. Degradation byproducts were iden-tified using gas chromatography-mass spectrometry and a probable pathway was proposed. Moreover,Gd-doped Ag3PO4samples displayed adequate reusability after three successive experiments.
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