ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
RESUMO Este artigo busca avaliar e comparar qual material (PET ou vidro) proporciona um ciclo de vida mais sustentável para os recipientes utilizados no envase de refrigerantes. Foram comparados quatro recipientes de vidro - três retornáveis e um descartável - com cinco recipientes em polietileno tereftalato (PET) - três descartáveis produzidos com material virgem, um descartável produzido com 20% de material reciclado e um retornável (RefPET). Utilizou-se como ferramenta o programa CES-Selector/EcoAudit, o qual considera cinco etapas principais do ciclo de vida do produto - material (obtenção de matéria-prima), produção, transporte, uso e descarte. Os indicadores resultantes foram a energia incorporada e a quantidade de CO2 emitida. Os resultados, para cada 1.000 L de refrigerante envasado, comprovam que a reutilização do recipiente é a escolha ambientalmente mais correta e mostram que, nas garrafas de PET, quanto maior a capacidade do recipiente, menor a quantidade de material de PET utilizado, menor a energia incorporada e menor a emissão de CO2. Por outro lado, para as garrafas de vidro, o resultado é oposto, ou seja, quanto maior a capacidade do recipiente, maior a quantidade de material utilizado, maior a energia incorporada e maior será a quantidade de CO2 emitida. Considerando a energia incorporada e o CO2 gerado, o resultado final mostra que, para envasar pequenos volumes (vidro de 290 mL e PET de 250 mL), os recipientes de vidro apresentam resultados melhores, enquanto, para envasar volumes maiores (acima de 600 mL), os recipientes de PET são os mais indicados.
ABSTRACT The present paper aims to assess and compare which material (PET or glass) provides a more sustainable life cycle for soft drink containers. Four glass containers, three returnable ones and one disposable were compared to five PET containers (polyethylene terephthalate), three disposable ones made from virgin material, one disposable made from 20% of recycled material and one returnable (RefPet). The CES-Selector/EcoAudit program, which considers five main stages of the product life cycle - material (obtaining raw material), production, transportation, use and disposal - , was used. The resulting indicators were the energy and the amount of CO2 emission. The results, for every 1,000 liters of soft drink bottled, prove that the reuse of containers is the most environmentally correct choice and show that in PET bottles the larger the container capacity the smaller the amount of PET material used, lower the energy and the lower the CO2 emission. On the other hand, for glass bottles, the result is opposite, that is, the larger the container capacity, the greater the amount of material used, the greater the embodied energy and the greater the CO2 emission. Considering the incorporated energy and the CO2 generated, the final result shows that glass containers present better results when filling small-volume packages (290 ml glass and 250 ml PET), while PET containers are the most suitable ones for larger volumes (above 600 ml).
