Photocatalysis is one of the methods which may be applied for the degradation of environmental water pollutants using the energy of solar light. The problem with its application is, however, that solar light is accessible only at the surface layer of water, especially in the case of heavily polluted water.

This problem may be overcome with the application of floating photocatalysts able to float on the surface of water for a period of time long enough to to carry out photochemical degradation of the pollutants. The advantage of this solution is that the photocatalysts can be easily removed and usually they can be reused.

Goals of the research

The goal of the studies was to obtain photocatalysts based on a nontoxic floating support of natural origin and titanium dioxide as the photoactive compound and use them for the photodegradation of organic pollutants, pharmaceuticals in particular.

Results of the research

Floating photocatalysts were obtained using expanded perlite which is produced by calcination of perlite, a volcanic rock, which contains a large amount of water. At elevated temperatures water expands the perlite yielding a foamy structure with air-filled bubbles. Titanium oxide was supported onto perlite grains by direct hydrolysis of titanium isopropoxide. The photocatalyst obtained could float on water and gradually sank. The floating fraction decreased linearly down to about 30% within 10 days. It efficiently photodegraded phenol and methylene blue used as model pollutants under irradiation with near UV ligth. It could also photocatalyze the degradataion of sulfamethoxazole, the most commonly used antibiotic of the sulfonamide group,  which is widely spread and persistent in theenvironment, frequently detected in water resources, and very difficult to eliminate The degradation was mediated by photogenerated hydroxyl radicals. The primary degradation products, which were identified using UPLC-MS technique, were mainly hydroxylation and hydrolysis products.

Collaboration

Dr Paweł Żmudzki, Jagiellonian University, Faculty of Pharmacy, Department of Medicinal Chemistry