Porphyrin@Lignin nanoparticles: Reusable photocatalysts for effective aqueous degradation of antibiotics
Giusi Piccirillo, Nidia Maldonado-Carmona, Diana L. Marques, Nicolas Villandier, Claude-Alain Calliste, Stéphanie Leroy‐Lhez, M. Ermelinda S. Eusébio, Mário J. F. Calvete, Mariette M. Pereira
Abstract
The aqueous photocatalyzed degradation of trimethoprim (TMP) and sulfamethoxazole (SMX), highly prescribed antibiotics, often found in hospital wastewaters and/or surface/ground waters in high concentrations, is described, using a 400 W medium pressure mercury lamp as irradiation source, air as oxidant and a porphyrin based photocatalyst. The new photocatalyst was prepared by encapsulation of stable meso-tetra(2,6-dichlorophenyl)porphyrin photosensitizer into acetylated lignin nanoparticles, which are derived from a bio-based cellulose industry byproduct. This is a reusable stable catalyst (after at least 7 cycles, no loss of activity or degradation/leaching, was observed) capable of promoting the nearly complete degradation of TMP and SMX antibiotics, with unprecedented total organic carbon (TOC) removal, namely 75 % and 85 %, respectively. Mechanistic studies of these reactions, using singlet oxygen and radical scavengers, followed by HPLC-MS analysis allowed the identification of only two residual TMP photoproducts.