Abstract
The photocatalytic degradation of paracetamol (a common analgesic also known as acetaminophen) in ultrapure water with different photocatalytic systems was performed under ultraviolet or visible irradiation. The photocatalysts employed were: commercial Degussa-P25 TiO2 and Au–TiO2 under UVA irradiation (365 nm) and g-C3N4 and Au-g-C3N4 under visible light irradiation (low-power (4 × 10 W) white light LEDs), improving the effectiveness of degradation rates when the gold nanoparticles (Au NPs) were combined with the semiconductors. The nanostructured photocatalysts were synthesised and characterised by transmission electron microscope (TEM), UV–vis diffuse reflectance spectroscopy and, in the case of g-C3N4 photocatalysts by X-ray photoelectron spectroscopy (XPS). The influence of the pH in the depletion of paracetamol with g-C3N4 and visible light was evaluated. In addition, the stability and lifetime of the photocatalyst g-C3N4 in the degradation of paracetamol were studied.Graphical abstract
Highlights
In recent decades, myriad pharmaceuticals have been found in sewage, groundwater, surface water and drinking/tap water [1]
The bandgap of g-C3N4 appears at lower energy than T iO2, 2.75 eV and 3.23 eV, respectively, this agrees with the fact that g-C3N4 absorbs lower-energy light, in the visible range
The heterojunction between the gold nanoparticles and the semiconductors produces a slight decrease of the T iO2 and g-C3N4 band gaps (2.67 eV for g-C3N4 and 3.1 eV for TiO2) (Fig. S2)
Summary
Myriad pharmaceuticals have been found in sewage, groundwater, surface water and drinking/tap water [1]. Graphitic carbon nitride (g-C3N4) has attracted increasing attention as a novel photocatalyst due to its properties, namely: narrower bandgap than TiO2, facile synthesis from the abundance of inexpensive materials, good adsorption ability, high physical and chemical stability or -conjugated structure [10, 13] This promising material has some important drawbacks: (i) it might undergo fast recombination of charge carriers or (ii) it displays a narrow visible light absorption window. When an organometallic complex is employed as a metal source, mild reaction conditions can be applied, avoiding the use of strong reducing agents such as NaBH4 This methodology allows a good control over size, shape, composition and surface state of the obtained nanoparticles. We describe a novel single-step strategy to prepare photocatalysts with enhanced visible-light activity for the removal of paracetamol by the grafting of gold nanoparticles, which are formed in situ through the controlled decomposition of an organometallic complex such as [Au(C6F5)(tht)] (tht = tetrahydrothiophene). The efficiency of g-C3N4 under different pH conditions and its reusability and stability as a photocatalyst was evaluated
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