A safer disposal of hazardous phosphate coating sludge by formation of an amorphous calcium phosphate matrix
Keywords: 
Solidification/stabilization
Leaching
Zinc
Waste management
Heavy metals
Calcium aluminate cement
Issue Date: 
15-Aug-2015
Publisher: 
Elsevier
OpenAIRE: 
This work was fully funded by Fundación Universitaria de Navarra (grant FUNA2013-15108402). We are also grateful to LURESA for providing complementary funding (grant LUR-2010). Dr. M.C. Jimenez de Haro (ICMS) for helping in SEM analyses. Leaching experiments were carried out by P. Margallo as part of her final degree project.
ISSN: 
0301-4797
Citation: 
Navarro-Blasco I, Duran A, Perez-Nicolas M, Fernandez JM, Sirera R, Alvarez JI. A safer disposal of hazardous phosphate coating sludge by formation of an amorphous calcium phosphate matrix. J. Environ. Manage. 2015;159:288-300.
Abstract
Phosphate coating hazardous wastes originated from the automotive industry were efficiently encapsulated by an acid-base reaction between phosphates present in the sludge and calcium aluminate cement, yielding very inert and stable monolithic blocks of amorphous calcium phosphate (ACP). Two different compositions of industrial sludge were characterized and loaded in ratios ranging from 10 to 50 wt.%. Setting times and compressive strengths were recorded to establish the feasibility of this method to achieve a good handling and a safe landfilling of these samples. Short solidification periods were found and leaching tests showed an excellent retention for toxic metals (Zn, Ni, Cu, Cr and Mn) and for organic matter. Retentions over 99.9% for Zn and Mn were observed even for loadings as high as 50 wt.% of the wastes. The formation of ACP phase of low porosity and high stability accounted for the effective immobilization of the hazardous components of the wastes

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