Pigments used in ceramic glazes have been obtained by chromium ions extraction from galvanic sludge and their precipitation as barium chromate and lead chromate from technological solutions. The chemical composition was determined by XRF method. Complex thermal analysis TG-DSC, XRD and SEM methods have been used for microstructural characterization and thermal treatment behaviour evaluation, in order to establish the compatibility with the ceramic matrix. XRD spectra have highlighted only lead chromate specific interferences in the monoclinic phase and barium chromate in the orthorhombic phase, suggesting an advanced degree of purity. Weight losses of 2.2% for barium chromate and 3.1% for lead chromate have been recorded on the TG curve at 800�C. As a result of thermal treatment, barium chromate has changed its colour from yellow to green.
This paper presents the numerical modeling results of the pollutant dispersion in the Danube riverbed, using experimental data recorded monthly on the Borcea - Bala - Old Danube sector, for a 2 years period. The water samples were collected from the left bank, center and right bank of the river, and the follwing indicators were analyzed: lead, nickel, chromium, cadmium and copper. Heavy metals were determined by atomic absorption spectrophotometry with graphite furnace (GFAAS). Numerical modeling was performed using Delft3D software, taking into account a reference situation (a scenario regarding the pollutant dispersion for known concentrations) and a scenario that simulates an accidental pollution (where the concentrations of pollutants were increased by 50 % compared to the values corresponding to Class V of water quality according to M.O. 161-2006). In order to properly assess the pollutant dispersion, the construction of the numerical model was developed taking into account a number of complex hydraulic works (bottom sill, dredging operations on the Danube in the area of confluence and downstream, on the whole width of the fairway). The results of numerical modeling generated the pollutant dispersion maps and the dispersion coefficients (indicating the transport of substances). Higher levels of the monitored indicators were observed on Borcea, caused by water coming from different sources of pollution (industry, agriculture, etc.) and discharged at a low flow, limiting the dilution.
In this research, the identification of the influence of several methods of rice husk ashes preparation over their structure was followed, by varying the synthesis parameters, as well as by subsequent application of the grinding process. The obtained rice husk ash samples with high silica composition, were characterized by X-ray diffraction (XRD) to determine the compositional phases and crystalline structure of the samples, by scanning electron microscopy (SEM) to observe the microstructure and the particle sizes, and by laser granulometry to establish the granulometric distribution. Thus, it was possible to conclude that the technological process used for rice husk ash preparation shows influences on the samples microstructure and composite phases, as well as differences in particle sizes by decreasing their values as a result of mechanical process application. Based on these analyses, it was verified which of the obtained rice husk ash samples present a suitable microstructure, in order to capitalize them in environmental applications.
The impact of the marine environment on the coastal structures was reported since the middle of the XIX century. In order to test the aggressiveness potential of the Black Sea water on the coastal constructions, between the years 2009-2010, a seawater sampling program was carried out in the Navodari -Vama Veche sector of the Romanian coastline. Therefore, seawater samples were collected from 15 locations situated along the Black Sea coastline in order to determine their action on coastal constructions. For all the samples the pH, electrical conductivity, salinity were determined in-situ and presented normal values. The aggressiveness of the seawater samples was determined in laboratory, through a parallel analysis of the SO4 2-and Mg 2+ ions concentrations in seawater compositions. The results showed the presence of MgSO4 in the analyzed samples, which affected the mortars used in determinations even after 3 months of storage. It was also observed that the only materials resistant to the water aggressiveness were the mortars with 20% dolomitic limestone. Additionally, the investigation determined that the seawater aggressiveness affects not only the concrete structure but also has a great impact on the metallic parts found in these structures by highly corroding them, as seen for the Mamaia Bridge, build in 1935, the hydrotechnics nodes and other coastal structures.
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