Enhanced ozonation of selected pharmaceutical compounds by sonolysis.

In search of new options to achieve removal of pharmaceuticals in the environment, combined ultrasound and ozonation has become a focus of intense investigation for wastewater treatment. In this study, three pharmaceuticals were selected as model compounds for degradation experiments: diclofenac (DCF), sulfamethoxazole (SMX) and carbamazepine (CBZ). Comparison of the degradation rates for both ozonation and combined ultrasound/ozonation treatments was performed on single synthetic solutions as well as on a mixture of the selected pharmaceuticals, under different experimental conditions. For single synthetic solutions, the efficiency removal for ozonation reached 73%, 51% and 59% after 40 min for DCF, SMX and CBZ, respectively. Comparable results were obtained for pharmaceuticals in mixture. However, the combined ultrasound/ozone treatment was found to increase degradation efficiencies for both DCF and SMX single solutions up to 94% and 61%, respectively, whereas lower removal yields, up to 56%, was noted for CBZ. Likewise, when the combined treatment was applied to the mixture, relatively low removal efficiencies was found for CBZ (44%) and 90% degradation yield was achieved for DCF.

An integrated chemical and ecotoxicological assessment for the photocatalytic degradation of vancomycin.

The photocatalytic degradation of an antibiotic, vancomycin B hydrochloride (VAN-B), has been investigated in aqueous suspensions of titanium dioxide (TiO2) by monitoring the change in its concentration as well as the production of ammonia and chlorides as a function of irradiation time. The removal of 50mg L(-1) VAN-B solution yields maximum concentrations of 2.45 and 2.53 mg N-NH3 L(-1) after 120 min of photocatalytic oxidation using 0.1 and 0.2 g TiO2 L(-1), respectively. When 0.2 g TiO2 L(-1) were applied up to 87% of the stoichiometric amount of chloride was reached within 120 min of irradiation, corresponding to 0.087 mmol L(-1). A set ofbioassays (Daphnia magna, Pseudokirchneriella subcapitata and Ceriodaphnia dubia) was performed to evaluate the potential detoxification of VAN-B and its by-products of oxidation under chronic and acute tests. The toxicity of the treated VAN-B samples varied during the oxidation, due to the formation of some intermediate products more toxic than VAN-B. Despite almost total removal of VAN-B that was achieved within 120 min of irradiation, a significant increase in toxicity was observed in chronic tests proving that the chronic assays are more appropriate than acute ones to detect the impact of by-products formed during the photocatalytic degradation of antibiotics.

An insight into PANI-TiO2 photocatalysis of refractory organic matter through molecular size fractionation.

Refractory organic matter (RfOM) is ubiquitous in aquatic environment and plays various roles in regulating the fate, transport, toxicity, and bioavailability of chemical species, such as metals, emerging organic contaminants, and nanomaterials. RfOM is mainly represented by humic acids (HA) as the acid insoluble fraction of organic matrix. Considering the complex and multicomponent characteristic of HA, a detailed study was designed to elucidate the fate of molecular size fractions (MSFrs) of humic under solar irradiation in the presence of polyaniline (PANI)-modified TiO2 composites. Humic acid as a consortium of diverse molecular size fractions with different tendencies towards oxidation requires further assessment by UV-vis and fluorescence spectroscopic parameters complementary to previous studies on the photocatalytic degradation of RfOM by using TiO2 and PANI-TiO2 composites. Absorbance-based removal efficiencies under initial and post-photocatalytic conditions showed a re-formation trend during photocatalysis in the presence of PANI and TiO2 where higher MSFrs were transformed to lower MSFrs that was apparent for < 3 kDa fraction. Completely different profiles were observed for PT-41 and PT-81 indicating similar degradation pathways independent of PANI ratio in the composite. As confirmed by the investigated parameters, formation of both 450 kDa and 220 kDa MSFrs were evident under all conditions indicating in situ generation of higher MSFrs. The eligibility of coupled absorbance-fluorescence measurements to discern molecular size distribution of humic acid via oxidative degradation was also investigated. Excitation-emission matrix (EEM) contour plots emphasized the ratio dependency of PANI modification of TiO2 and revealed sample specific variations that were more pronounced in terms of the emergence of tyrosine- and tryptophan-like aromatic proteins.

A comprehensive review on the use of second generation TiO2 photocatalysts: Microorganism inactivation.

Photocatalytic disinfection practices have been applied for decades and attract current interest along with the developments in synthesis of novel photocatalysts. A survey based investigation was performed for elucidation of photocatalytic treatment details as well as disinfection mechanism of microorganisms. The present work brings significant information on the utilization of second generation TiO2 photocatalysts for inactivation of microorganisms typically using E. coli as the model microorganism. Special interest was devoted to the role of organic matrix either generated during treatment or as a natural component. Studies on photocatalytic disinfection were extensively reviewed and evaluated with respect to basic operational parameters related to photocatalysis, and types and properties of microorganisms investigated. Degradation mechanism and behavior of microorganisms towards reactive oxygen species during disinfection and organic matrix effects were also addressed. For successful utilization and effective assessment of visible light active photocatalysts, standard protocols for disinfection activity testing have to be set. Further improvement of the efficiency of these materials would be promising for future applications in water treatment processes.