Photocatalytic materials development is very important in the environmental perspective. They can be employed in clean energy production by hydrogen generation as well as in wastewater treatment by photocatalysis. One of the key subjects in this area is the advancement of materials with low band gap, thus the catalyst can use the sunlight more efficiently. Based on this issue, this research aims to develop photocatalysts based on bismuth, niobium and iron (Bi2FexNbO7), analyze the influence of iron concentration (x = 0, 0.8, 1 and 1.2) and characterize through optical and structural analysis. The powder samples were synthetized by sol gel method. Band gap estimation was performed throw UV-Vis analysis and Kubelka-Munk method. XRD technique was employed to phase determination and structural characterization. The catalyst with no iron (Bi2NbO7) presented a mix of three phases from reagents and a band gap of 3.14 eV. The iron addition promotes crystalline photocatalysts with high visible light absorption ability and hence lower band gap, 2.09 eV. Further analysis must be performed; however, based on structural and optical proprieties, these materials can efficiently be employed both in wastewater treatment and hydrogen production.
The research developed a combined system in batch flow and in pilot scale for the treatment and reuse of urban effluents. The system was fed raw effluent from a university campus in Brazil and composed of four anaerobic reactors, three constructed wetlands (CWs) and an ozonation unit. The three sequential hybrid constructed wetlands were composed of a floating treatment wetland, an aerobic-anoxic baffled constructed wetland (CW) and a saturated vertifcal flow CW. Later, during the last trimester, weekly samples of the treated effluent were ozonated by bubbling with an application rate of 240 mg.h-1 O3. The system presented high removal rates efficiencies in terms of carbonaceous organic matter (78.9%), nitrogen (91.0%), color (96.7%) and turbidity (99.1%). In addition, it worked well for disinfection and acute ecotoxicity, but P was only efficiently (75%) removed in the first 8 months, with removing efficiency declining after this period. Ozonation provided significant color removal and an increased pH. The combination of floating, alternated upflow and downflow and saturated vertical flows improved the treatment of wastewater. This was due to the presence of both aerobic and anaerobic zones, as well as the filter substrate, through an integrated system with simple construction and operation and increased lifespan.
Adequacy to sustainable development standards requires the use of methods and tools that enable the quantification and monitoring of environmental impacts related to production processes. As a subsidy to the potential reduction of impacts by solar collectors, this paper proposes an environmental evaluation, considering an alternative solar collector scenario to be compared with a commercial one, from the life cycle perspective. Using the Life Cycle Assessment (LCA) tool, the scenarios were evaluated using the SimaPro 8.5 software. The functional unit definition was defined with real system verification through the system preparation and operation in the laboratory, which is characterized as heating 26 L of water utilizing a thermosyphon system at a temperature greater than or equal to 38 ºC. Analyzing the LCA results, it was observed that the alternative system use offers environmental impacts reduction in all impact categories selected when compared to the commercial system. In addition, a sensitivity analysis was proposed considering a variation in polyester resin mass used in the alternative system. The simulation of changes in the resin resulted in even more decreases in the environmental impacts. Regarding thermal efficiency, the industrial system excelled in terms of absorption capacity and thermal reserve. Thus, the present paper using the analyzes proposed within the defined scope, allowed the comparison between the systems in such a way that it was possible to know whether the use of the alternative solar collector results in environmental advantages without losing thermal efficiency.
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