Abstract: In this work, samples of 10 mol% Mg-doped SnO2 were synthesized by Pechini's method and calcined at 500°C. Previous analysis suggests that the additive is preferentially located on the surface of nanoparticles as a surface excess. Since MgO is highly soluble even in weak acid medium, the samples were "washed" with concentrated nitric acid for a few hours in order to remove Mg from the surface. After the lixiviation, the sample was thermally treated again. This procedure was carried out five times using the same sample, and the dependence between macroscopic properties and surface excess was demonstrated, since it was detected a direct relationship on particle size and isoelectric point on each new washing. Also, a new method to measure surface excess in solids was applied.
Abstract: Nowadays, with increase amounts of sludge derived from the treatment of domestic sewage put pressure into research on systems for the adequate use of these materials. The aim of the present work is to study the use of sludge ash, from sintering and calcinated process, as a raw material for the ceramic industry. Using the sewage sludge ashes as ceramic raw material there will be no contamination of soil and underground water. Metals and toxic compounds like Al, Fe, Ba, Cr, Cu, Mn and Zn oxides were analyzed and characterized by X-ray fluorescence (XRF), scanning electron microscopy (SEM) and plasma emission spectroscopy (ICP-OES). The leached material was chemically analyzed where the integration of oxides into the ceramic matrix of sludge ash was observed. Residual decomposition was analyzed by TG, DTG and DTA curves.
Abstract: The possibility of thermal treatment plants of municipal wastewater is an alternative solution for the final disposition of the sludge produced on small cities as Barueri, a small town of São Paulo State, Brazil. Combustion and pyrolysis of that municipal waste, occurring respectively in air and nitrogen, have been studied by thermogravimetry (TG) and differential thermal analysis (DTA). The main steps of each case were analyzed and Kissinger plots were used to estimate respective activation energies. DTG peaks are more indicated to represent the condition of maximum reaction rates than DTA peaks.
Abstract: This paper reports an investigation on the effect of thermal activation of kaolinite. It is well known that during calcinations (400–650°C), kaolinite loses the OH lattice water and is transformed into metakaolinite or amorphous material. Arsenic is trace element that is toxic to animals including humans. The adsorption of arsenic on kaolinite was investigated at varying pH and thermal pretreatment. Calcination of sample is carried out at 650 °C for 3 h. The decomposition of kaolinite is recorded using methods of thermal analysis. The resultant product is identified by XRD. Laboratory experiments were conducted examining the effect of arsenic by thermally modified kaolinite. The Langmuir isotherm was used to describe arsenite and arsenate sorption by the calcined kaolinite. The equilibrium parameters used were based on experimental data obtained for the dynamic adsorption process of arsenic. Removal of arsenate using natural kaolinite was satisfactory, whereas arsenic was not removed by adsorption with thermally modified kaolinite. Moreover, the adsorption of arsenic by kaolinite and metakaolinite decreases with increasing pH.
Abstract: The ceramic material found at the archeological site in Caninhas, shows funerary structures of combustion and various objects of Tupi-Guarani indigenous use. These pieces and fragments were saved and cataloged, in approximately 4000 units. The ceramics present a gradient of color, from ochre to dark gray, when from the surface to the center of the piece, indicating compositional variation caused by inefficient sintering carried out by indigenous people. The goal of this study was to observe the phase transition temperature, decomposition, mass variation and reactions that occur in the archeological and nowadays ceramics (by DSC/TG), together with micro structural analysis (by SEM), phase analysis (by XRD) and chemical composition (by EDS). Ceramics nowadays are sintered with air, in a temperature ranging between 400-800 °C for one hour, and presents heterogeneous microstructure. The archeological ceramics were identified by the ilitte, hydrated alumina, lutecite and quartz phase, and the caulinite, lutecite and quartz phase in clay produced today from that region differs in all characteristics and aspects according to time. The interaction between different areas of expertise is fundamental to aggregate knowledge: the use of ceramic material engineering to archeological application.
Abstract: Nowadays the polishing products for finishing procedures have a high cost in the finishing process, once these products are imported or made by synthetic diamond. This study shows the polishing effects of several of low cost abrasives ceramic powders available on the national market. The material used in this study were silicon carbide and aluminum oxide, the variables of particle diameter and surface roughness were analyzed. The test samples materials used in the experiments were aluminum, carbon steel 1020, stainless steel 304 and polycarbonate. Finally, a comparative evaluation was showed using metallographic polishers already existent on the market.
Abstract: Brasgel clay has been modified via cation exchange reaction using quaternary ammonium chlorides (stearyl dimethylammonium chloride, Praepagen). Basal spacing, interlamellar structure clay have been characterized using X-ray diffraction (XRD) technique. The organoclay was characterized by the Foster Swelling test. The results indicated that the quaternary ammonium salts were intercalated between the layers of clay. The Foster Swelling Test results indicated that the affinity of stearyl dimethylammonium chloride, Praepagen occurred in the treated clay tested in all organic solvents (diesel, gasoline, toluene and p-xylene), without and with agitation. the treated sample presented a high swelling capacity (with and without agitation) when tested in gasoline. On the other hand, when inserted in diesel oil without agitation, the treated samples presented low swelling capacity, but when the assay was performed under agitation, it yielded an intermediate swelling capacity. In Toluene, the samples presented intermediate swelling, both without and with agitation. In p-xylene, the samples presented low swelling, without and intermediate swelling, with agitation. Therefore, this clay can be used for the removal of oils and greases from polluted aqueous effluents of the petroleum industry.
Abstract: Brasgel clay and Gray clay has been been subjected to modification through ion-exchange reaction by quaternary ammonium (cetyltrimethyl ammonium bromide, CTAB). The samples were studied by X-Ray Diffraction, Infrared Spectroscopy, Scanning Electron Microscopy (SEM) and the Foster’s Swelling test. The results indicated that the quaternary ammonium salts were intercalated between the layers of clay. The basal spacing of unmodified Brasgel clay, determined by XRD, was 1.329 nm and after modification it increased up to 2.101 nm. By analyzing the results obtained in this study, particularly those provided by infrared spectroscopy, it was concluded that the treated, organophilic sample (modified with CTAB) comprised CH2 and CH3 groups in its structure, which provides evidence of the efficiency of the organophilization process. Foster´s swelling was carried out with and without agitation in gasoline, diesel, toluene and lubricating oil. The results indicated the samples was organophilic materials, with improved efficiency of Brasgel clay in gasoline and diesel and when compared to Gray clay in the test of capacity for adsorption and Foster´s swelling, the results were similar to kerosene and lubricating oil.
Abstract: As the preservation of the environment is a big concern nowadays, plenty of studies have arisen in order to decrease the production or reuse the waste from human activities. In this context, the civil construction industry comes up, as it is able to incorporate waste to mortar, being a great alternative for the reuse of solid waste. The scope of this work has been the characterization of Construction and Demolishment Waste (RCD) and its incorporation to the mortar aiming at the development of alternative construction materials in the future for the economical reutilization of waste discharged in embankments and landfills so far preserving the environment so far. The experimental studies taken with sample bodies, such as water absorption, resistance to compression, X-ray diffraction, X-ray fluorescence and scanning electronic microscopy, elicits the viability of the partial substitution of cement by RCD mixed waste, taking its different applications into consideration.
Abstract: The objective of this work is to characterization of sugarcane bagasse ash waste aiming the use it in red ceramic industry. The characterization was done in terms of chemical composition, X-ray diffraction, particle size distribution, morphology, and plasticity. The results show that the cane bagasse ash waste is a non plastic material, which contains high content of silica and minor amounts of Al, Fe, Ca, Mg, and K oxides. Thus, the sugar cane bagasse ash waste presents high potential for application in the manufacture of ceramic products such as bricks, roofing tiles, and ceramic tiles.