(177c) Graphene Oxide Quantum Dots Coupled with Advanced Oxidation Processes for the Removal of Pharmaceuticals and Disinfection of Wastewater

Graphene oxide quantum dots (GQDs) are an interesting class of zero-dimensional, oxygen-rich materials with size less than 20 nm. GQDs exhibit the phenomena of quantum confinement and edge effects which bestow them with outstanding physico-chemical properties. These features have made GQDs suitable materials for various applications including the catalytic removal of organic pollutants and the disinfection of microbes. On the other hand, peracetic acid (PAA) is a strong disinfectant with a wide spectrum of antimicrobial activity. Due to its bactericidal, virucidal, fungicidal, and sporicidal effectiveness as demonstrated in various industries, the use of PAA as a disinfectant for wastewater effluents has attracted much recent attention. PAA is referred to as green disinfectant widely used in wastewater treatment.

This study aimed to investigate the synergy advantage of combining GQDs and PAA based advanced oxidation processes (AOPs) for the removal of pharmaceuticals and disinfection of wastewater at tertiary stage of the treatment plant.

A series of experiments were carried out: a) degradation efficiency and kinetics of GQDs/PAA system against pharmaceuticals in real wastewater; b) identification of the main reactive radicals responsible for the degradation of pharmaceuticals, c) photodegradation mechanistic pathway based on the detected reaction by-products determined by LC-Q-TOF-MS; d) antimicrobial activity; e) Genotoxicity and mutagenicity test.

The results indicated that the same degradation trends of pharmaceuticals were observed for the influence of PAA dosage; influence of water matrix and influence of initial concentration as a function of contact time.

Furthermore, the main reactive radicals responsible for the degradation of pharmaceuticals in wastewater were identified as hydroxy (•OH) as well as peroxy radicals CH3C(=O)OO• and CH3C(=O)O•. The genotoxic and mutagenic potential of the degradation products formed during the degradation of pharmaceuticals were confirmed to be non-mutagenic. GQDs/PAA was further tested as a potential disinfectant and S. aureus was completely inactivated. GQDs/PAA also eliminated more than 90% of bacteria present in real wastewater.

This contribution presents an opportunity to simultaneously degrade pharmaceuticals and their active metabolites as well as inactivate microorganisms using GQDs/PAA. These results are crucial and might find application in water/wastewater treatment plants.