Supporting of pristine TiO2 with noble metals to enhance the oxidation and mineralization of paracetamol by sonolysis and sonophotolysis

Abstract

The presence of pharmaceutical residues in fresh water bodies has been of significant environmental concern due to their undesirable effects on aquatic organisms even at very low concentrations. The present study is about the elimination and overall degradation of a common anti-inflammatory pharmaceutical-paracetamol in water by catalytic oxidation using high-frequency ultrasound, UV-irradiation and both. The catalysts were synthesized sonolytically by immobilization of Pd, Au and both on commercial TiO 2 (P-25) to produce very fine nanoparticles with excellent surface porosity. It was found that immobilization of precious metals was an effective means of enhancing the catalytic activity of TiO 2 in the presence of ultrasound and UV-irradiation, but sonication was more effective than photolysis for the activation of Pd-TiO 2 and Pd/Au-TiO 2 , owing to their smaller particle size (than that of Au-TiO 2 ) that facilitated the formation of cavitation bubbles and reactive species on the catalysts. Moreover, Pd-TiO 2 was the most stable nanocomposite in terms of recovery and reuse (in sonocatalysis), exhibiting closely the same degree of catalytic activity as that in the previous use within very short time. No difference was observed between sonolysis and photolysis when using commercial TiO 2 , due to the slight turbidity of the solution and the competion for photons arising from photoreactivity of PCT. Application of sonolysis and photolysis simultaneously resulted in enhanced rate of PCT elimination and TOC decay in the presence of all catalysts. However, synergistic enhancements were observed only with Pd/Au-TiO 2 and Au-TiO 2 during oxidation and mineralization of the compound, respectively. Enhanced activity of Au-TiO 2 for the longer mineralization process was attributed to complete elimination of PCT (reduced photon competition) and the individual activity of gold in the UV-vis region.

Merging Metallic Catalysts and Sonication: A Periodic Table Overview

“…In order to assess the electrocatalytic action, indium-doped tin oxide (ITO) electrodes were modified with Pd or Pd-Sn NPs, which involve the initial oxidation of the electrode to make it OH-terminated, followed by aminosilanization with 3-aminopropyl-triethoxysilane (APS) and subsequent polymerization at 100 • C. The resulting APS-modified ITO electrode was immersed in a citrate solution of Pd-Sn NPs (Scheme 19). to the zero-valent oxidation state followed by immobilization of the resulting nanoparticles on TiO2 surfaces [69]. The sonolytic oxidation of paracetamol in aqueous solution catalyzed by Pd-TiO2 and Pd/Au-TiO2 was especially effective due to their considerably smaller size (than that of Au-TiO2).…”

“…In a more-oriented synthetic application, Safari et al reported a convenient synthesis of 1,2,4,5-tetrasubstituted imidazoles (70) through a four-component one-step condensation of a substituted aromatic aldehyde (67), benzyl (68), phenyl amine (69), and ammonium acetate with nanocrystalline magnesium aluminate (MgAl 2 O 4 ) in ethanol under ultrasound (Scheme 22) [115]. The protocol show the typical advantages of sonochemically accelerated reactions in terms of high yields, mild conditions, short reaction times, and easy work-up.…”

“…Heterometallic NPs can also be prepared by similar strategies of stabilization and deposition, which are enhanced by ultrasonic irradiation, such as the sonochemical reduction of Pd and Au salts to the zero-valent oxidation state followed by immobilization of the resulting nanoparticles on TiO 2 surfaces [69]. The sonolytic oxidation of paracetamol in aqueous solution catalyzed by Pd-TiO 2 and Pd/Au-TiO 2 was especially effective due to their considerably smaller size (than that of Au-TiO 2 ).…”

Degradation of pharmaceuticals by ultrasound-based advanced oxidation process

“…Similarly, the sonochemical degradation of acetaminophen was enhanced with the addition of catalysts like Pd-TiO 2 and Pd/Au-TiO 2 . This is owing to the significantly smaller size of these particles, which promoted the formation and collapse of cavitation bubbles on their surface and the incidence of solute contact with the active sites (Ziylan-Yavas et al 2015).…”

Visible Light Photocatalytic Degradation of Azo Dye and a Real Textile Wastewater Using Mn, Mo, La/TiO2 /AC Nanocomposite

“…Usually, titanium dioxide can exist as three crystalline polymorphs, namely, anatase (tetragonal), brookite (orthorhombic), and rutile (tetragonal) 17,18,19 . However, they have shown various photocatalytic activities, due to variations in their physical and crystallographic properties 20,21 . Anatase is the most photoactive phase of TiO 2 , due to its particular crystallographic structure, which increases electron-hole recombination times 22,23 .…”