Insight into Photodegradation of Diclofenac: Mechanism, Efficiency, Role of Parameters, Toxicity Assessment and Catalyst Stability

Pharmaceuticals and personal care products (PPCPs) are one of the emerging pollutants (EPs) groups that attracted the environmentalist’s attention according to the increase in their demand. Diclofenac (DFC) is an anti-inflammatory medication used as a first-line treatment for pain. Around 15% of DFC is unmetabolized after human consumption, leading to an increase in the opportunity to release DFC into the environment. DFC may build up in the environment over time, which increases its negative impacts on the ecosystem. Several biological, physical, and chemical techniques have been applied to treat DFC. This review provides an overview of the photodegradation of DFC including photodegradation efficiency, mechanism, the role of physicochemical parameters, and toxicity assessment. Generally, the photodegradation systems showed high efficiency in the removal. However, each experiment has been applied under different experimental conditions and different parameters such as the type and dosage of catalyst, the chosen wavelength of the radiation, pH, temperature, and additive concentration. This led to the differentiation in the photodegradation efficiency and photodegradation rate of DFC. We revealed that the physicochemical parameters of the photocatalytic process are a double edge sword. On the one hand, raising their values up to a certain point might help the treatment work well. On the other hand, a significant rise has a negative impact on the effectiveness of the treatment and raises the expense of the treatment operation. The toxicity tests indicated that most frequent DFC by-products are not safe, and their release into the environment may negatively affect the ecosystem. This review may provide a useful recommendation for future researchers who want to treat DFC by photodegradation and enables them to enhance the applicability of photodegradation.