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Mineral phases and metals in baghouse dust from secondary aluminum production
Xiao-Lan, H., A. El Badawy, M. Arambewela, R. Adkins, AND T. Tolaymat. Mineral phases and metals in baghouse dust from secondary aluminum production. Jacob de Boer, and Shane Snyder (ed.), CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 134:25-30, (2015).
The objective of this study was to investigate BHD from SAP facilities in the U.S. by determining the mineral phases and the metal (Al, As, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Se and Zn) content of the samples. The study also examines the leachability of metals from BHD exposed to deionized water in an anaerobic and elevated temperature environment (Huang et al., 2014), which is designed to simulate key conditions in municipal solid waste (MSW) landfills. The U.S. Environmental Protection Agency (EPA) toxicity characteristic leaching procedure (TCLP) (USEPA, 1992) was also employed on these BHD samples. The information resulting from this study will help provide the scientific foundation to understand BHD waste material, its potential risk and strategies for its management.
Baghouse dust (BHD) is a solid waste generated by air pollution control systems during secondary aluminum processing (SAP). Management and disposal of BHD can be challenging in the U.S. and elsewhere. In this study, the mineral phases, metal content and metal leachability of 78 BHD samples collected from 13 different SAP facilities across the U.S. were investigated. The XRD semi-quantitative analysis of BHD samples suggests the presence of metallic aluminum, aluminum oxide, aluminum nitride and its oxides, spinel, elpasolite as well as diaspora. BHD also contains halite, sylvite and fluorite, which are used as fluxes in SAP activities. Total aluminum (Al) in the BHD samples averaged 18% by weight. Elevated concentrations of trace metals (>100 µgL-1 As; >1000 µgL-1 Cu, Mn, Se, Pb, Mn and Zn) were also detected in the leachate. The U.S. toxicity characteristic leaching procedure (TCLP) results showed that some samples leached above the toxicity limit for Cd, Pb and Se. Exceeding the TCLP limits in all sample is independent of facilities generating the BHD. From the metal content perspective only, it appears that BHD has a higher potential to exhibit toxicity characteristics than salt cake (the largest waste stream generated by SAP facilities).