Description
Endocrine disrupting compounds (EDCs) have received considerable worldwide attention, as they can mimic or/and block the activity of natural hormones disruptors on reproductive functions. Environmental hazards properties related with endocrine activity occurring at low concentrations (pg/g – ng/g), coupled with occurrence in water at trace concentrations (1ng/L - 1μg/L), emerge as a major concern for water quality. Butylparaben and benzylparaben are put on the list of suspected endocrine disrupting chemicals by several organizations e.g. US Environmental Health Science and WWF. Because conventional treatment methods are ineffective in removing EDCs at low concentration, approaches for the removal of these toxins during drinking water treatment are needed. This project will be focused on photodegradation of butylparaben and benzylparaben using photosensitized oxidation process. The photosensitized oxidation is especially attractive method of degradation because it use oxygen from air and solar photons in visible range. Photosensitized oxidation may occur in homogeneous and heterogeneous system. Disadvantages of this process in homogenous system are low photostability of the sensitizers and difficulty in removing them from the solution after the reaction. These problems can be overcome by conducting studies using immobilized sensitizers, where it can be easily recovered and re-used significantly thereby reducing the cost of photodegradation. In project the polymeric polyurethane nanofabrics prepared by the electrospinning method will be used as a carrier for the immobilized sensitizer. Due to the proven harmful environmental and health effects of the EDCs, the understanding of possible pathways of their phototransformation in reservoirs can be important to protect the health of present and future generations. Up to now there are no publication on the kinetics of photosensitized degradation of parabens in heterogeneous system.
Summary of project results
Scientific objective of the project was to examine the effectiveness of an photochemical degradation processes based on visible light for hardly biodegradable butyl- and benzylparaben)–Endocrine Disrupting Compounds (EDCs) present both in municipal and industrial wastewater. It is well-established that aquatic wildlife in marine and freshwater of the European Union is exposed to natural and synthetic EDCs which are able to interfere with the hormonal system. Although, the majority of these cases have been observed among animals, the implications of the environmental risk to wildlife, livestock and human populations cannot be underestimated. Therefore, the precautionary principle requires to take appropriate steps to eliminate these compounds from the environment. It was shown that a polyurethane polymer nanofabrics with immobilized meso-tetraphenylporphyrin is capable of degrading parabens in the presence of visible light and molecular oxygen. The major role of singlet molecular oxygen in this process was proved. The experiments confirmed that the degradation is occurring due to Type II reaction mechanisms. The efficiency of the parabens removal is strongly depended on pH reaction solution, the initial photosensitizers concentration as well as the nanofabrics area weight. A slight addition to nanofabrics another photosensitizer - zinc phthalocyanine (Zn-Pc) resulted in intensification of the reaction and increasing the reaction rate. It has been found that increasing the amount of incorporated TPP on to nanofabrics as well as area weight of nanofabrics significantly increases the rate of BuP and BeP photodegradation. The obtained results allowed us to estimate the kinetic and adsorption parameters. Dependence of initial degradation rates on initial concentration confirms Langmuir–Hinshelwood kinetics The obtained results allowed for a proposed kinetic model and determination of the kinetic constants that physically describe the process in a heterogeneous system. Hydroxylation of parabens was found to be the major reaction that occurred during the photosensitized oxidation. The main photoproducts of the photodegradation of parabens via singlet oxygen were identified. The toxicity test showed a significant reduction of toxicity after photosensitized oxidation, indicating that reduction of parabens concentration corresponds to an actual detoxification of the treated reaction solution.
Summary of bilateral results