As water is essential to life and is an indispensable resource for ecosystems and their services and for nearly all human activities, the goal of this research was to evaluate the surface water quality of the Danube as it passes through the Romania–Serbia border in the nature reservations Djerdap and Iron Gate. The study aimed to assess the oxygen regime, nutrients and heavy metals contamination of the surface waters of the Danube on a length of about 240 km, between Bazias and Iron Gate II. Reference sampling and analytical methods (UV-VIS and AAS) were deployed to reach this goal. In addition, sediments were analyzed through back scattered SEM-EDAX for the elemental analysis of the sediment surface. Results obtained show a low environmental impact of heavy metals, while the Danube’s oxygen regime is under stress due to nutrients’ (nitrites and orthophosphates) significant concentration in the Danube surface water in the analyzed sector. Our approach can be applied to other water bodies in the area, to increase available scientific data together with societal awareness of the Danube’s environmental risks.
The literature was reviewed with respect to deinking flotation methods with toner samples, specifically emphasizing the speciation of copy machine and laser printing, which produce an increasing quantity of paper that is difficult to recycle. Speciation here refers to the physical-chemical characteristics of the toner, which change because of the polymerization (fusion) and oxidation process, due to exposure to heat, light and oxygen (air) during the printing process. To simulate the deinking flotation, after the ideal disintegration process, samples of toner were prepared in order to provide free toner particles. Synthetic toner has iron content and the same physical-chemical features as free disintegrated printed toner particles.We report the toner (I) and fibre (Y) recovery and the brightness (B) of laboratory filter pads formed of deinked product as deinking efficiencies. The application of oleic acid as the collector in the flotation stage gives a better flotation recovery in alkaline than in acidic conditions. The highest brightness (BF = 93.66%) and flotation recoveries (I = 90, Y = 92.82%) were achieved during testing at an oleic acid concentration of 3.38·10(-6) mol l(-1), which is the lowest dose used. This makes the use of oleic acid economical and environmentally friendly.
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