Metal Stabilization Mechanisms in Recycling Metal-Bearing Waste Materials for Ceramic Products

Abstract

Ceramic materials are essential to a wide range of marketable products, and are of diverse compositions and characteristics. The effective thermal reaction capable of achieving mineral phase transformation is a unique and beneficial opportunity to convert many types of metals into more environment-ally friendly forms. This characteristic may be of particular value to the sustainable development in the 21st century, when more and more attention is focused on environment protection. It is well known that discharge of hazardous metals into natural environments, such as water bodies and soils, is detrimental to human health and the ecosystem. For example, nickel and copper enter the human body via food and water consumption. For human beings, continued inhalation of nickel and its compounds can cause lung cancer, while acute nickel exposure can lead to a variety of clinical symptoms, such as gastrointestinal disturbances, visual disturbance, headache and giddiness, and so on. For animals, prolonged exposure to nickel can lead to adverse effects on haematological parameters, decreased body weights and cancer and, therefore, nickel compounds are often treated as carcinogenic substances (Gang & Zhuang, 2007). Similarly, high accumulation of copper in human body is detrimental to liver and may even cause deadly cirrhosis (European Copper Institute [ECI], 2008). A large amount of waste containing hazardous metals is generated in a wide variety of industries, such as mining and ore processing, metallurgy, chemical industry, alloys industry, paint industry, glass industry, pulp and paper mills, leather tanning, textile dyeing and printing, chemical fertilizer, chloro-alkali industry, petroleum refining and coal burning (Agarwal, 2009). Some municipal solid wastes also contain hazardous metals, such as electrical and electronic equipments waste, barriers, paints and so on. In 2000, the total amount of hazardous waste in China was as much as 830 million tons (State Environmental Protection Administration of China, 2001). It’s reported that hazardous waste of up to 963 million tons was generated in 2004, which was 116% of that in 2000 (State Environmental Protection Administration of China, 2005). In the United States, it has been reported that about 40% of hazardous wastes contain heavy metals (Hirschhorn & Oldenburg, 1991). Traditional wastewater treatment methods use physiochemical processes, such as precipitation, coagulation, reduction, ion exchange, and membrane processes such as ultrafiltration, electrodialysis, and reverse osmosis to remove the pollutants (Park et al.,