Materials Science Forum Vols. 798-799

Abstract: The blast furnace is one the main systems used in steelmaking plants operating with iron ores. In addition to the production of pig iron and slag, the blast furnace operation also generates a considerable amount of wastes such as dust usually collected in the upwards flowing gas. The dust collecting stage, without separation procedures, produces a sludge, which cannot be recycled inside the plant due to the concentration of undesirable earth alkaline metals as well as zinc. A possible solution for this so-called global blast furnace sludge (GFS) is its incorporation, outside the plant, into clayey ceramic products processed at high temperatures. Therefore, the objective of the present work was to investigate the effect of GFS incorporation, in amounts of 5 and 10 wt%, into kaolinitic clay ceramics fired at 750, 950 and 1050oC. Initially, the GFS was characterized and, after processing, incorporated into ceramics that were then tested for the water absorption, linear shrinkage and flexural strength. It was found significant improvements in the properties for GFS incorporated ceramics fired at 1050oC.

Abstract: The aim of this work was the obtaining coarse aggregate from red mud (RM) focused on the processing properties. RM and two clays (A and B) were selected from Pará state (Brazil) and characterized by XRD, XRF and HSM. Six compositions were planned by mixture design. RM amount varied from 80 to 100wt%. Compositions were pelletized in a pelletizer disc, resulting test pieces of 4 to 19 mm (diameter). Firing temperatures ranged from 1150 to 1190 oC and holding time from 15 to 90 min. Pelletizing humidity, dry friability, water absorption, and apparent density were determined. Clays A and B presented clay mineral content about 67 and 12 wt%, quartz 25 and 82wt%, respectively. The higher clay mineral contents the smaller dry friability and water absorption. Appropriated clay mineral contents and firing parameters is needed in order to satisfy processing and final properties requirements, being possible to obtain aggregates from pelletizing process.

Abstract: In Brazil, the majority of construction and demolition waste materials (CDW) is sent to waste dumps or landfill sites. Having low cost applications in mind, this work has the purpose of investigating the effect of the incorporation of fired ceramic rubble reclaimed from CDW obtained directly from the building construction industry on the final properties of compressed earth blocks, which are especially interesting in low-income and marginalized communities. To this aim, clay-based mixtures containing up to 5 wt.% of ceramic rubble were prepared. Lime and cement were added as binders (6, 8, 10 and 12 wt.%). Cylindrical test pieces were produced by uniaxial compression and left to harden at ambient conditions for 7, 28 and 56 days. The hardened specimens were characterized in terms of microstructure (SEM), compressive strength, water absorption and wear resistance. The results obtained in physical and mechanical evaluation tests demonstrated that small contents of ceramic rubble from the building construction industry can easily be incorporated into compressed earth blocks without degradation of typical properties, enabling savings in cement addition.

Abstract: Hydraulic fracturing is a very important technique to increase the productivity and recovery of oil reservoirs with low pressure or high depth. The hydraulic fracturing technique is a method of well stimulation in which liquid under high pressure is pumped down a well to fracture the reservoir rock adjacent to the wellbore. Propping agents are used to keep the fractures/cracks open. They can be made from the reject of mineral extraction processes when they present specifics characteristic. The aim of this paper is the evaluation of the use of industrial rejects to the development of ceramic synthetic proppants that are resistant to chemical corrosion and high mechanical strength in aqueous acid and salt water environment. In this study, industrial rejects from nickel sulfide ore flotation (grey mud - GM), red mud (RM) from Bayer process and black mud (BM) from Caron processing of nickel was used as raw material for the production of ceramic synthetic proppants. The material processing was performed through drying, milling, pressing, sintering and characterizing raw material. Several characterization techniques such as X-ray powder diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), high temperature dilatometry and compression strength test were performed after sintering to evaluate the technological potential of recycling these metallurgical and mineral rejects. Mechanical properties were improved after sample sintering. The results show that it is possible to manufacture ceramics of high strength and resistance to acidic/salt water environment as a result of processing minerals reject.

Abstract: The red mud is a well known insoluble residue generated in the Bayer process to benefit bauxite ores. This residue is composed of ceramic related compounds such as iron oxide, sodium aluminum silicates, carbonates, calcium aluminates and titanium dioxide. The incorporation of industrial residues in clay ceramics has been extensively investigated, not only as an environmentally correct solution but also as an economic way to save raw materials. Therefore, the present work evaluated the properties of clay ceramics incorporated with up to 40 wt% of red mud. Clay bodies with different percentages of red mud were press-molded and fired at 750, 950 and 1050°C. The evaluated technological properties were linear shrinkage, water absorption and mechanical strength. Sensible changes in such properties were found with red mud addition. In particular, the ceramic fired at 1050°C displayed favorable water absorption with red mud incorporation.

Abstract: Red mud is a specific term applied for a residue generated during the processing of aluminum ores, mainly bauxite in the Bayer process, to produce alumina (Al₂O₃). In several countries where bauxite is mined and processed, distinct red muds are generated in ever growing amounts and becoming an environmental problem. This problem is also affecting the large bauxite processing plants in Brazil and a possible solution for the red mud is its addition to clay ceramics. Before an industrial scale addition is implanted, the specific red mud needs to be characterized for compatible behavior with the ceramic clay matrix. Therefore, the objective of the present work was to characterize a red mud generated in Brazil for an eventual addition to clay ceramic. This was conducted through the determination of density, chemical and mineralogical composition as well as size distribution and microscopic observation of particles. The results indicated that the specific red mud investigated is compatible with clays and has a potential for addition in common red ceramics.

Abstract: In this study, it was evaluated the potential use of commercial sodium bentonitic clay, called Fluidgel, chemically and thermally treated, as an adsorbent in the removal of zinc ions from aqueous effluents. The chemical treatment was carried out with 10 g of clay dispersed in 100 mL of acetic acid 4 %. The heat treatment was obtained by calcination at 750 °C for 24 hours in muffle. The adsorption experiments were performed in thermostatic bath system and fixed bed, both based on preliminary study of metallic cationic speciation. The kinetics of zinc ions adsorption by acid-treated clay was rapid, requiring a minimum time of 60 min to reach equilibrium. The adsorbed amount and percentage of total zinc removal, at equilibrium time, was 0.06 mmol/g and 45 %, respectively, using the acid-treated clay. There was no removal of zinc by Fluidgel calcined clay in bath system, but in fixed bed it was obtained the total amount of zinc removal of 0.11 mmol/g and 41 % of percentage of removal.

Abstract: The microstructural and technological properties of clay ceramic incorporated with 10 and 20 wt% of elephant grass ashes were investigated at different firing temperatures of 650, 850 and 1050oC. X-ray diffraction were used to obtain the minerals and phase compositions. The microstructure was analyzed by scanning electron microscopy. The technical properties related to water absorption, linear shrinkage and flexural rupture strength were obtained by standard test. The results showed significant changes in the microstructure and phasic composition with increasing firing temperature. A marked improvement in the water absorption, decreasing to 18% as well as increase in strength, above 5 MPa, was found at 1050°C. However, only a slight contribution might be attributed to the incorporation of elephant grass ash. Nevertheless, its use as a by-product and the associated saving in clay are relevant environmental and economical advantages.

Abstract: Several environmental studies have been dedicated to the correct management of industrial residues. The conventional clay ceramic productive sector became, in past decades, a growing alternative for these residues through their incorporation in products such as bricks and tiles. The firing temperatures for ceramic sintering usually transform the incorporated residue into an inert microstructural phase. In some cases, the residue may even improve the ceramic properties. However, during the firing stage, polluting gases might be emitted causing environmental impact. Therefore, the objective of the present work was to evaluate the gases emitted during sintering of a clay ceramic incorporated with 10 and 20 wt% of elephant grass ashes. The emission was investigated for firing temperature in the interval from 250 to 1100oC and the gases analyzed by photothermic technique. The ash incorporation promoted a significant increase in the emission of greenhouse gases such as CO and CO₂.

Abstract: The production of fabrics is one important sectors of the national economy, especially in jeans production. During dyeing step, in the production of jeans, it is generate a large amount of wastewater rich in indigo, a strong blue dye that when released directly into the environment is responsible for several environmental impacts. The aim of this work is to study the use of microfiltration ceramic membranes for indigo separation in effluents from textile industry. Initially the ceramic membranes were characterized in relation to the pore size and tangential flux. It was produced an indigo solution whose concentration and composition similar to the effluent of textile industry. The solution was characterized and submitted to a filtration through ceramic membranes by tangential flow, by applying a pressure of 3 Bar. At the end it was verified that 99% of the indigo was retained.