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Industry and everyday activities generate huge amounts of waste, some of which are toxic or environmentally harmful; historically, this would have been dumped, leading to contamination.
Environmental pollution can be attributed to many industrial sectors, but mineral extraction and processing represent the greatest proportion, producing solid, liquid and gaseous by-products. Mining is an important source of mineral commodities for all countries and has been essential for maintaining and improving living standards over the years; it’s necessary for building roads, homes, hospitals cars, computers and so much more.
Although some recycling occurred, it wasn’t until the environmental movement of the 1960s and 1970s that it emerged as a popular and necessary idea. Today, waste management strategies focus on source reduction and resource recovery, reuse and recycling during processing. Not only is it cost-effective in the long term, but it is also less damaging to the environment to prevent or minimize waste generated.
Mining and Ceramics
Traditional ceramics - brick, roof and floor tiles - other construction materials, and technical ceramics such as porcelain and mullite bodies are usually highly diverse due to the wide compositional range of natural clays used as raw materials. As a result, there is the potential to use large amounts of waste of suitable composition produced from mining processing as raw materials in the ceramic industry.
For example, the granite processing industry produces large amounts of waste containing feldspar, quartz, mica, metallic dust and lime. Likewise, kaolin processing also produces immense amounts of waste; around 70% of the total waste is produced during processing when sand is separated from the ore, and during wet sieving when the kaolin is purified. Kaolin is an important raw material for various industries, including rubber, plastic, paper, cement and ceramics.
Utilizing waste products from the mining industry as additives in ceramics is nothing new and the addition of waste materials can impart beneficial properties during the fabrication process. However, manufacturing ceramics solely from waste is becoming increasingly likely.
Research conducted in the Paraíba region in Brazil, collected samples of granite sawing waste from local companies and characterized them to determine their density, particle size distribution, surface area, and chemical composition. Furthermore, their ceramic composition was tested to evaluate their suitability for adding into the mix for use in ceramic bricks and tiles. The study showed granite wastes have physical and mineralogical characteristics similar to those of conventional ceramic raw materials and could be an important means of reducing waste.
Further studies have demonstrated the potential for waste materials to be used as more than just an additive in the ceramics industry – they could be used as the only raw materials in their manufacture. Exploratory research in Brazil and Portugal focused on producing porcelain-like ceramics – namely floor tiles – for the construction industry, although researchers say it could be adapted to any part of the sector using other types of waste.
The researchers studied clay-mining tail, sludge from potable water treatment and sludge from gneiss – a widely distributed type of metamorphic rock – and varvite stone-cutting processes, and characterized them for chemical and mineral composition, thermal behavior and particle size distribution.
The study illustrated the obvious environmental and cost benefits. Recovering and recycling waste means there is no need to dispose of it, and it is cheaper than using raw materials. Energy-wise, utilizing recycled waste or raw materials, the cost was the same.
Recovering and recycling waste from mining operations by utilizing it as an alternative raw material has the potential to create diversification among products, reduce production costs, and conserve non-renewable resources and save energy. Rather than mine raw materials, waste can replace it and be used to create building materials, ceramic bricks and tiles, roof tiles, mortars and much more.
References and further reading
Recycling of Mine Wastes as Ceramic Raw Materials: An Alternative to Avoid Environmental Contamination
Use of granite sawing wastes in the production of ceramic bricks and tiles
Mineral to clay, waste to waste - industrial by-products replace virgin material