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Abstract G. Kenanakis

Photocatalysis is a well-known technique with many applications in the degradation of organic pollutants [1]. Among other pollutants, detergents and unused or expired pharmaceuticals are commonly discharged into drains, and as a result, pharmaceutical compounds have recently been detected in surface, ground water, or even drinking water with many adverse impacts on both people and environment [2-5].

The disadvantage of photocatalysis when a semiconductor (such as ZnO, TiO₂ etc.) is used in the form of a powder is the need to remove it after the end of the treatment [6,7]. For this reason, international efforts are focused on photocatalytic systems, where the catalyst is used in the form of a film on inert substrates to eliminate the stage of powder removal [8,9]. Over and above that, photocatalytic efficiency increases with effective surface area, and consequently a nanostructured photocatalyst is beneficial. However, solid catalysts’ samples, such as thin films or nanostructured ones, in most cases cannot exceed an overall size of a few centimeters, due to the limitation of the fabrication techniques, limiting their potential use in real-life applications.

In the last few years, 3D printing technology become of great interest in several fields of research, such as medicine, chemistry and materials science, as an effective, fancy, quick and low-cost route for the production of 3D large-size samples [10-11]. The most common technique is fused deposition modeling (FDM) in which polymers are the usual materials used as filaments. It should be noted that although there are several reports on 3D structures for novel environmental applications [12], there are only a few in which custom-made filaments (with nanoparticles of inorganic materials into a polymeric matrix) are used in combination with FDM technology, i.e., in [13], and none for drug-residuals’ removal by photocatalysis.

This work discusses an investigation of the photocatalytic degradation of a commercially available liquid laundry detergent, based on synthetic, less foaming ingredients; Dixan (Henkel AG & Co. KGaA, Düsseldorf, Germany), and paracetamol (also known as acetaminophen, APAP), a medicine available in a huge number of countries worldwide, used to treat pain and fever, using 3D-printed photocatalysts enriched with nanostructured TiO₂.

It is worth mentioning that the FDM 3D printed photocatalytic devices can be successfully used at least three times for the photodegradation of Dixan and APAP aqueous solutions under UV-A irradiation, reaching an efficiency of ~90% and ~70%, respectively, after three cycles of reuse, offering a novel low-cost alternate way for fabricating large-scale photocatalysts, suitable for practical applications.

References

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