Degradação fotocatalítica de cloridrato de propranolol em meio aquoso empregando nanocompósitos de bentonita e TiO2

Abstract

The increasing presence of contaminants, including pharmaceuticals, in water resources represents a challenge for water quality and public health. Pharmaceuticals, such as propranolol, have been associated with adverse effects on aquatic organisms due to their persistence in the environment. Decontamination techniques are essential, and Advanced Oxidation Processes (AOPs), such as heterogeneous photocatalysis, have emerged in this scenario. This technique uses semiconductors like titanium dioxide (TiO2) to form reactive oxygen species, which transform pollutants into less toxic substances. Bentonite, a clay mineral, has been associated with TiO2 to increase the specific area and pollutant adsorption capacity, improving photocatalytic efficiency. The aim of this study is to evaluate the efficacy of TiO2 associated with bentonite in removing propranolol from water. Nanoparticles were synthesized using the solvothermal method following an experimental design aimed at evaluating the effect of three synthesis variables: temperature, heating time, and TiO2/Bentonite mass ratio, on the efficiency of propranolol removal from the aqueous medium. Based on the information obtained from the experimental design, specific synthesis conditions were employed, allowing the obtainment of a photocatalyst with optimized efficiency for propranolol removal from the aqueous medium. In the removal of propranolol in aqueous medium by heterogeneous photocatalysis, the most effective sample was treated at 180°C for 20 hours, with a TiO2/bentonite ratio of 2, removing 99.3% of propranolol in 210 minutes. This superior performance is attributed to the thermal treatment of this sample at the highest temperature, forming the anatase phase of TiO2, which is more active in photocatalysis. The combination of bentonite and TiO2 resulted in significant improvement, compared to the 61.1% obtained with pure TiO2. The presence of bentonite favored the dispersion of TiO2 particles, increasing the specific area available for the reaction, which in this case was crucial in producing more efficient photocatalysts in the removal of pollutants such as propranolol. Furthermore, the process proved to be reproducible, allowing for the separation and reuse of the photocatalyst in multiple cycles with little loss of efficiency.