The research team working under the leadership of Prof. Anna Zielińska-Jurek from the Faculty of Chemistry at Gdańsk University of Technology, in cooperation with scientists from ASTRA beamline, developed and characterized a new semiconductor material based on bismuth orthovanadate (BiVO₄) and copper oxide sub-nanoclusters (CuO_x). This material, when exposed to visible light, is able to effectively remove pharmaceuticals in water. Measurements made at the SOLARIS synchrotron using X-ray absorption spectroscopy (XAS) revealed the oxidation state of copper oxides. The research results were published in the journal "Separation and Purification Technology" from Elsevier publisher.

The rapid development of medicine and the pharmaceutical industry has made pharmaceutical pollution one of the greatest environmental dangers. Some of the most frequently detected pharmaceuticals in Polish sewage are naproxen, a popular painkiller, and ofloxacin, an antibiotic. These compounds, found in rivers, lakes or seas, are persistent and not susceptible to biological degradation, and conventional methods used in sewage treatment plants are insufficient to remove them.

A promising way to remove pharmaceuticals from the aqueous phase is their degradation in the process of heterogeneous photocatalysis supported by peroxymonosulfate ions (HSO₅−, PMS). These processes are based on the generation of highly reactive radicals under sunlight, which, as a result of reaction with pollutants, are able to purify water.

The requirement for carrying out this process is the use of a semiconductor-based material that will both initiate a chemical reaction under illumination and activate the PMS. For this purpose, the research team proposed a CuO_x/BiVO₄ photocatalyst, which with the addition of PMS shows high removal efficiency of naproxen (100% degradation in 60 min) and ofloxacin (98.2% in 120 min) under visible light. The results performed using X-ray absorption spectroscopy at the ASTRA  beamline indicated that copper oxides exist in the form of sub-nanoclusters and their total oxidation state is 1.48. The high activity of the proposed photocatalyst was maintained in subsequent process cycles, which has a positive effect on the reusability of the photocatalyst.

Fig 1. Photocatalytic degradation of a) naproxen (NPX) and b) ofloxacin (OFL) using BiVO₄ (BVO_NHV_W) and CuO_x/BiVO₄ (Cu/0.1 BVO_NHV_W) under visible light (λ > 420 nm) with addition of PMS solution. Conditions: [NPX]₀ = 15 ppm, [OFL]₀ = 20 ppm, [PMS] = 0.1 mM

Author: Marta Kowalkińska

Link to the publication: Marta Kowalkińska, Alexey Maximenko, Aleksandra Szkudlarek, Karol Sikora, Anna Zielińska-Jurek, Addressing challenges of BiVO4 light-harvesting ability through vanadium precursor engineering and sub-nanoclusters deposition for peroxymonosulfate-assisted photocatalytic pharmaceuticals removal, Separation and Purification Technology, Volume 351, 24 December 2024, 127643 DOI:10.1016/j.seppur.2024.127643