Affiliations 

  • 1 Università degli Studi di Milano, Dipartimento di Chimica, via Golgi, 19 - 20133 Milano, Italy
  • 2 University of La Rioja, Centro de Investigación en Síntesis Química (CISQ), Department of Chemistry, C/ Madre de Dios 51, E-26006 Logroño La Rioja, Spain
  • 3 Lappeenranta University of Technology, Laboratory of Green Chemistry, School of Engineering Science, Sammonkatu 12-50130, Mikkeli, Finland
  • 4 Universiti Teknologi PETRONAS, Fundamental & Applied Sciences Department, 32610 Seri Iskandar, Malaysia
  • 5 Polytechnique Montréal - Génie Chimique 2900 Boul, Edouard Montpetit - H3T 1J4, Montréal, QC, Canada
  • 6 Università degli Studi di Milano, Dipartimento di Chimica, via Golgi, 19 - 20133 Milano, Italy. Electronic address: carlo.pirola@unimi.it
Ultrason Sonochem, 2020 Oct;67:105123.
PMID: 32283492 DOI: 10.1016/j.ultsonch.2020.105123

Abstract

The nonsteroidal anti-inflammatory drug sodium diclofenac (DC) is an emerging water pollutant which resists conventional wastewater treatments. Here the sonophotocatalytic degradation of DC was carried out using micrometric TiO2 (both pristine and Ag-decorated), UV-A irradiation and 20 kHz pulsed ultrasound. Sonophotocatalytic tests were compared with photolysis, sonolysis, sonophotolysis, sonocatalysis and photocatalysis data performed in the same conditions. A synergy index of over 2 was determined for tests with pristine TiO2, while values close to 1.3 were observed for Ag-TiO2. Reaction intermediates were studied by HPLC-MS, showing degradation mechanisms activated by hydroxyl radicals. Similar pathways were identified for photocatalytic and sonophotocatalytic tests, although the latter led to more oxidized compounds. Different reactor configurations (static and dynamic set ups) were studied. Sequential and simultaneous application of UV light and ultrasound led to similar performance. The role of water matrix was investigated using ultrapure and drinking water, showing marked detrimental effects of electrolytes on the DC degradation. Overall, the combined treatment proved more efficient than photocatalysis alone especially in demanding working conditions, like in drinking water matrices.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.