Light induced synthesis of ceria based materials and their applications for photocatalysis

The dissertation focuses on a simple, sustainable and low-cost approach to design Ag-CeO2 nanoheterostructures in aqueous solutions via photochemical UV-light driven process. The proposed synthesis method comprises two steps: photochemical CeO2 synthesis using sodium azide and a photochemical synthesis of Ag-CeO2 nanoheterostructures, where previously synthesized CeO2 nanoparticles are applied as a photoactive compound. No organic solvents or additives were applied in order to obtain particles with an uncoated, thus more reactive surface expecting to further apply the as-prepared structures for photocatalysis. Moreover, since no organic solvents but ethanol are used and no toxic waste is formed during the reaction, the proposed synthesis method could be defined as a sustainable route to the formation of nanoparticles. The as-prepared Ag-CeO2 nanoheterostructures. demonstrated visible light driven photocatalytic activity on photocatalysis of TBT and are expected to find applications in environmental processes

Cerio oksido nanodalelių ir nanoheterostruktūrų su plazmoninėmis nanodalelėmis fotocheminė sintezė bei gautų darinių pritaikymas fotokatalizėje

The dissertation focuses on a simple, sustainable and low-cost approach to design Ag-CeO2 nanoheterostructures in aqueous solutions via photochemical UV-light driven process. The proposed synthesis method comprises two steps: photochemical CeO2 synthesis using sodium azide and a photochemical synthesis of Ag-CeO2 nanoheterostructures, where previously synthesized CeO2 nanoparticles are applied as a photoactive compound. No organic solvents or additives were applied in order to obtain particles with an uncoated, thus more reactive surface expecting to further apply the as-prepared structures for photocatalysis. Moreover, since no organic solvents but ethanol are used and no toxic waste is formed during the reaction, the proposed synthesis method could be defined as a sustainable route to the formation of nanoparticles. The as-prepared Ag-CeO2 nanoheterostructures. demonstrated visible light driven photocatalytic activity on photocatalysis of TBT and are expected to find applications in environmental processes

On the effectiveness of tributyltin ban part II: Temporal and spatial trends of organotin pollution in intense sediment accumulation areas and dumping sites of the Baltic Sea

Based on the knowledge gained from our previous study, our aim is to observe the current levels of butyltin (BTs) pollution, changes during different seasons, and the factors that affect these trends in the areas of highest concern. These areas include semi-enclosed bays in the Port that were previously affected by large tributyltin (TBT) inputs, as well as the dumping sites of dredged sediment in the Baltic Sea. Compared to previous studies, there has been a significant decrease in the levels of BTs in the Klaipeda Port. However, the sediment in the semi-enclosed bays still contained BTs, ranging from less than 0.5 ng Sn g−1 dw to as high as 728.5 ng Sn g−1 dw. Some BTs were also detected in the currently exploited dumping sites of the Baltic Sea. Moreover, butyltin degradation index (BDI) revealed occasional fresh TBT input or slow degradation both in the Port and in the Sea. Some trends in butyltin concentrations were indicative of the impact of climate change in Lithuania, which are consistent with global trends. We also found that variations in BTs concentrations were closely related to dredging and cleaning activities taking place in the Klaipeda Port. Correlation, principal component, and cluster analysis revealed close relationship between TBT and its degradation products, as well as between TBT and Zn, Pb, Cu. Ship cleaning/maintenance activities were identified as the main source of pollution in the study area. Despite the gradually decreasing BTs concentration in the Klaipeda Port, the problem is not yet completely solved

Oil pollution and geochemical hydrocarbon origin markers in sediments of the Curonian Lagoon and the Nemunas River Delta

The continuous research on anthropogenized coastal zones determined qualitative and quantitative characteristics of aliphatic hydrocarbons in the Curonian Lagoon and the Nemunas River Delta. The concentration of aliphatic hydrocarbons varied from 9.1 to 187.6 mu g g(-1) d.w. The Curonian Lagoon could be classi- fied as a slightly contaminated water basin with some moderately polluted areas, while both rivers and Lake Kroku Lanka were found to be slightly contaminated with aliphatic hydrocarbons. The prevailing unresolved complex mixture and geochemical markers suggested the existence of mixed biogenic-anthropogenic aliphatic hydrocarbon sources in the area studied. The biogenic impact was found to be more pronounced in Lake Kroh!. Lanka, the south-eastern part of the Curonian Lagoon and in the River Minija, while the Nemunas River Avan-delta demonstrated the highest loading of anthropogenic hydrocarbons. The same trends were confirmed by the principal component analysis

Solvothermal synthesis of calcium-deficient hydroxyapatite via hydrolysis of α-tricalcium phosphate in different aqueous-organic media

In the present work, the effects of various organic solvents (solvent nature and fraction within the solution) and solvothermal conditions on the formation of calcium-deficient hydroxyapatite (CDHA) via hydrolysis of α-tricalcium phosphate (α-TCP) are investigated. The wet precipitation method is applied for α-TCP synthesis, and the hydrolysis reaction is performed in solutions with different water-to-organic solvent ratios under solvothermal conditions at 120 °C for 3 h and at 200 °C for 5 h. Ethyl alcohol, isopropyl alcohol, and butyl alcohol did not inhibit the hydrolysis of α-TCP, while methyl alcohol and ethylene glycol have a more prominent inhibitory effect on the hydrolysis, hence the formation of single-phased CDHA. From all the solvents analysed, ethylene glycol has the highest impact on the sample morphology. Under certain water to ethylene glycol ratios and solvothermal conditions, samples containing a significant fraction of rods are obtained. However, samples prepared with ethylene glycol are characterised by a particularly low BET surface area

Ga-substituted cobalt-chromium spinels as ceramic pigments produced by sol–gel synthesis

For the first time to the best of our knowledge, cobalt-chromium spinels CoCr2–xGaxO4 with different amounts of gallium (x = 0−2 with a step of 0.5) were synthesized via the aqueous sol–gel route as ceramic pigments. The phase composition, crystallite size, morphological features, and color parameters of new compositions and their corresponding ceramic glazes were investigated using XRD, CIELab, SEM, and optical microscopy. It was demonstrated that the formation of single-phase CoCr2–xGaxO4 samples was problematic. Full substitution of Cr3+ by Ga3+ ion in the spinel resulted in the formation of light blue powders, which yielded violetish blue color for the corresponding ceramic glaze