Interactions of pharmaceutical compounds in water matrices under visible-driven photocatalysis

In this work, graphite-like carbon nitride (CN) materials were activated with 417 nm light from a LED device for the photocatalytic decomposition of commonly prescribed pharmaceuticals that are recurrent as organic micropollutants (MPs) in environmental waters. The decomposition resistance of diclofenac (DCF) and metoprolol (MET) was investigated by spiking these MPs in different water matrices: ultrapure water, river water, and wastewater. The photochemical stability of both MPs, each constituent ionic species' impact, and the MPs' competitive effect during the photocatalytic treatment were investigated. The target MPs had some photochemical instability under visible light in real water samples, suggesting that the organic matter present on it may act as a photosensitizer and promote these MPs' photodegradation. Besides, competition between the MPs was verified. A noteworthy decrease in the MET kinetic constants was observed when DCF was co-occurring in solution, independently of the water matrix and the initial concentration of the competing MP. By trapping photogenerated holes and radicals with selective scavengers, we found that different ratios of the reactive species are generated during the photocatalytic process, which relies on the presence of each or both MPs.