Abiotic degradation and environmental toxicity of ibuprofen: Roles of mineral particles and solar radiation. (15th March 2018) - Rubasinghege, Gayan
Abstract: The growing medical and personal needs of human populations have escalated release of pharmaceuticals and personal care products into our natural environment. This work investigates abiotic degradation pathways of a particular PPCP, ibuprofen, in the presence of a major mineral component of soil (kaolinite clay), as well as the health effects of the primary compound and its degradation products. Results from these studies showed that the rate and extent of ibuprofen degradation is greatly influenced by the presence of clay particles and solar radiation. In the absence of solar radiation, the dominant reaction mechanism was observed to be the adsorption of ibuprofen onto clay surface where surface silanol groups play a key role. In contrast, under solar radiation and in the presence of clay particles, ibuprofen breaks down to several fractions. The decay rates were at least 6-fold higher for irradiated samples compared to those of dark conditions. Toxicity of primary ibuprofen and its secondary residues were tested on three microorganisms: Bacillus megaterium, Pseudoaltermonas atlantica ; and algae from the Chlorella genus. The results from the biological assays show that primary PPCP is more toxic than the mixture of secondary products. Overall, however, biological assays carried out using only 4-acetylbenzoic acid, the most abundant secondary product, show a higher toxic effect on algae compared to its parent compound. Graphical abstract: Highlights: Adsorption of ibuprofen yields monodentate and bidentate complexes on clay. Adsorption of ibuprofen results bathochromic shifts in absorption bands of ibuprofen. Decay rate is 6-fold higher for irradiated ibuprofen compared to the dark condition. Ibuprofen is more toxic compared to a mixture of its secondary residues. 4-acetylbenzoic acid, a major secondary product, is more toxic to Chlorella compared to ibuprofen.