A technological approach using a metal-free immobilized photocatalyst for the removal of pharmaceutical substances from urban wastewaters

Abstract

The presence of micropollutants (MPs) in aquatic compartments poses a great risk to the ecosystems and human health. Advanced oxidation processes (AOPs), such as light-induced systems employing a variety of powder optical semiconductors, have been widely investigated to remove MPs from water and wastewater. In this work, a metal-free photocatalyst (GCN-T) immobilized in the form of a film (GCN-T/PVDF) was activated by visible light (λexc = 417 nm) and successfully tested in both batch and continuous flow mode reactors for the degradation of two pharmaceutical model compounds (metoprolol and venlafaxine) spiked in ultrapure water (UP) and urban wastewater (WW) samples. A total removal of MPs was reached after 3 h reaction using GCN-T/PVDF film in a batch reactor. Under continuous mode operation, a steady state was attained after 2 h, with ca. 64 % removal for both MPs being obtained. The photocatalytic system was also examined using a non-spiked WW sample to study its performance to remove trace concentrations of these and other MPs in this type of complex matrix. MPs, such as bezafibrate, carbamazepine, diclofenac, isoproturon, and tramadol, were detected and efficiently degraded using the GCN-T/PVDF film. Finally, the ecotoxicity of the WW samples was also investigated using the aquatic invertebrate microcrustacean Daphnia magna. The results showed that the toxicity of WW samples decreases with the photocatalytic treatment.