Valorization of the Residual Fraction of Coal Tailings: A Mineral Circularity Strategy for the Clay Ceramic Industry in the Carboniferous Region of Santa Catarina, Southern Brazil.

Mineral extraction of coal in the carboniferous region of southern Santa Catarina (Brazil) plays a significant role in the regional economy. However, this activity has severe environmental impacts, with approximately 65% of the extracted mineral being discarded as a rejected material (deposited in landfills). The identification of the technological potential of these materials, based on the geological aspects of the extraction site and the beneficiation operations applied to obtain coal, provides the opportunity to add value to different residual fractions that can be reused. Thus, waste valorization, the main objective of this work, has recently become a strategy for the application of these minerals in the production of clay ceramics using a systematic approach named CPQvA, which means "classification, potentiality, quantity/viability, and applicability". The use of these materials as secondary mineral sources can avoid the deposition of these materials in industrial landfills and help to reduce the pressure on landfills, which receive an average of four million tons of material annually. In this study, the residual fraction, part of the tailing from coal beneficiation, known as coal fines, was evaluated for formulation valorization in clay ceramics. This residual fraction was classified as non-hazardous (class II-A, non-inert). X-ray fluorescence spectrometry, X-ray diffraction, and thermogravimetric analysis were performed to characterize the moisture content, particle-size distribution, and coal content to be used in the development of different formulations using the residual fraction of coal tailings (ranging from 0 to 40%) that are of technological interest to the sector. Processing parameters, such as firing at different temperatures (750, 800, 850, and 900 °C), were also correlated with these formulations. The results were compared with those of a reference ceramic formulation from the local productive arrangement of Morro da Fumaça (Arranjo Produtivo Local Cerâmica Vermelha de Morro da Fumaça). The various relationships between the materials were characterized in terms of their thermal shrinkage, water absorption, and mechanical resistance. Leaching and solubilization environmental tests revealed that both the industrial standard formulation and formulations with the application of the residual fraction were classified as non-hazardous materials. Thus, the method of using a mining residual fraction in the formulation of clay ceramics proved to be beneficial for the circular economy in the regional mineral sector through productive and environmental gains; the primary mineral resource and energy consumptions and the impacts related to waste generation were reduced. The results of this study can be applied to similar situations in other parts of the world.

Sustainable Mining: Reuse of Clay from Abandoned Areas in the South of Brazil for Ceramic Production Based on a Simplex Design.

The environmental impact of clay mining can be minimized using extractive mineral circularity practices. Combining the available knowledge of the characteristics of different clays with statistical tools was a decisive step for the improved use of mining resources. Through blends, all the mined materials can be incorporated to produce quality ceramic products. This study identified two types of clay from abandoned mining areas in the southern state of Santa Catarina, Brazil. These raw materials were valued together with plastic clay, which is widely used in the region, to develop 10 different formulations using a mixture design method. The clays were characterized using average granulometric distribution, mineralogical composition, and chemical, thermal and plasticity analyses. The specimens were shaped by extrusion, dried in an oven, fired in a muffle furnace and characterized based on their shrinkage, water absorption and compressive strength values. Two clays with varying characteristics-one with low workability and the other with a high silica content-exhibited difficulties (generating defects) in the extrusion shaping process, which compromised the final quality of the ceramic paste. Results showed that incorporating up to 45% by mass of the low-workability clay resulted in an increase in water absorption. The more siliceous clay improved dimensional control; however, its use at high contents (~80%) decreased the mechanical resistance. Nevertheless, when used in controlled amounts, these clays can be beneficial to the production of blocks and bricks because they have the potential to improve some properties of the finished ceramic products.

Effect of Feldspar Substitution by Basalt on Pyroplastic Behaviour of Porcelain Tile Composition.

This work aims to evaluate the effects of feldspar substitution by basalt on porcelain tile composition with respect to its porosity, flexural strength, and pyroplastic deformation. Three ceramic formulations with different amounts of feldspar substituted with basalt, 50% (C1), 75% (C2), and 100% (C3), were evaluated at three different temperatures, 1200, 1220, and 1240 °C. Specifically, the effect of replacing feldspar with basalt on the pyroplastic deformation of ceramic bodies was analysed using optical fleximetry. The porosity of C1 at 1200 °C was 19.3 ± 2.9%, while that of composition C3 was 22.2 ± 0.7% at 1240 °C. The flexural strength was strongly influenced by the temperature. For C1 at 1200 and 1240 °C, flexural strengths of 11.1 ± 0.6 and 22.2 ± 1.9 MPa, respectively, were obtained. Regarding fleximetry, thermal deformation decreased with an increase in the amount of feldspar substituted with basalt. It was observed that C2 and C3 deformed less at high temperatures than the other combinations of compositions and temperature, probably owing to the lower amount of residual glass phase present during cooling. Compositions with higher substitution amounts of basalt (i.e., C2 and C3) exhibited more stable thermal behaviour than C0.

Aluminum anodizing waste and its uses: An overview of potential applications and market opportunities.

The aluminum anodizing process generates a large volume of waste composed mainly of amorphous aluminum hydroxide with chemical compatibility to be used in other industrial processes as an alternative starting raw material. This waste has several application possibilities such as the production of refractories, ceramic pigments, bricks, and many others. However, despite its potential features, its recycling process is far from well consolidated. This work highlights the most important contributions regarding Al-anodizing waste (AAW) features and their potential applications from the last 30 years. We provide the most complete and detailed characterization of AAW including chemical, physical, thermal, and microstructural analysis. The characterization analyzes were performed in a Brazilian waste sample and were compared with AAW worldwide. Additionally, our characterization results also considered differentiate previous processing; this, it many other possibilities are suggested that have not been explored thus far. The recycling feasibility of AAW is discussed according to the following criteria: classification, including legislation and standards; potentiality, including physical and chemical characteristics and purity; quantity, including production data; viability, including availability, costs regarding disposal and recycling process, and available technology for recycling; and applicability, including market opportunities. Moreover, alumina recovery from AAW and the related environmental aspects are discussed.