Beneficial use of aluminium and iron components of sludge incineration residues in ceramic materials

Abstract

A huge amount of sludge is generated from sewage treatment and waterworks. With the development of sludge incineration technology, most of the produced residues are buried in landfills, resulting in the loss of major constituents such as aluminium and iron that are present in the sludge residue. Moreover, toxic metals can leach out, causing further pollution. The need for “waste-to-resource” technology provides an incentive to develop economically viable reuse options. This study investigated the feasibility of beneficially incorporating aluminium and iron into marketable ceramic products. With CuO in the system, the CuAl₂O₄ spinel predominantly incorporated aluminium from waterworks sludge residues, while the CuFe₂O₄ spinel was a major iron-containing phase in the sewage sludge residue series. The maximum fraction of aluminium in the CuAl₂O₄ reached 98% and 83% for the α-Al₂O₃ + CuO and kaolinite + CuO systems, respectively. Using Fe₂O₃, iron was transformed into both tetragonal and cubic CuFe₂O₄, reaching complete incorporation. With various colours and microstructures formed, the products can be used as pigments, in construction, and as ceramic membranes. The findings of this study suggest a promising process for the beneficial use of waste aluminium and iron as ceramic raw materials, and may provide an economical means of reducing environmental concern over solid wastes.

Keywords:

• sludge incineration residues
• sewage
• waterworks
• aluminium
• iron
• ceramics

Funding

The authors gratefully acknowledge the funding for this research provided by the General Research Fund scheme (715612, 17206714) from the Research Grants Council of Hong Kong, and The University of Hong Kong Strategic Research Themes on Clean Energy and Earth as a Habitable Planet.

Additional information

Dr Yuanyuan Tang was a Postdoctoral Fellow till August 2014 at The University of Hong Kong (HKU) and received her Ph.D. training from 2008 to 2012 at HKU. Her research interest is applying environmental material technology for solid waste and wastewater treatments. She studied hazardous metal stabilisation via ceramic formation, sludge/ash reuse for construction materials, metal leaching mechanisms, and water–solid interfacial chemistry of environmental contaminants. She has published 11 Science Citation Index (SCI) journal papers (3 on Environmental Science & Technology), 17 conference papers, and 1 book chapter. Dr Tang is now an Assistant Professor in the South University of Science and Technology of China.

Ir Dr Kaimin Shih is an Associate Professor at The University of Hong Kong (HKU). He is the Vice President of the Overseas Chinese Environmental Engineers and Scientists Association; a member of the Executive Committee in the Hong Kong Waste Management Association; an Editor of HKIE Transactions; and an Associate Editor of Waste Management. He has published 61 Science Citation Index (SCI) journal articles, over 80 conference papers, 5 book chapters, and edited 1 book. His research is primarily on engineering and employing material properties for innovative waste and water treatment applications. He was awarded “Faculty of Engineering 2013 Teaching Award” and “HKU 2013 Outstanding Teaching Award”.