Arsenic, chromium and mercury removal using mussel shell ash or a sludge/ashes waste mixture
2013
Seco-Reigosa, Natalia | Peña-Rodríguez, Susana | Nóvoa-Muñoz, Juan Carlos | Arias-Estévez, Manuel | Fernández-Sanjurjo, María J. | Álvarez-Rodríguez, Esperanza | Núñez Delgado, Avelino
Different batches of valued mussel shell and waste mussel shell ash are characterised. Shell ash has pH > 12 and high electrical conductivities (between 16.01 and 27.27 dS m⁻¹), while calcined shell shows pH values up to 10.7 and electrical conductivities between 1.19 and 3.55 dS m⁻¹. X-ray fluorescence, nitric acid digestion and water extractions show higher concentrations in shell ash for most parameters. Calcite is the dominant crystalline compound in this ash (95.6 %), followed by aragonite. Adsorption/desorption trials were performed for mussel shell ash and for a waste mixture including shell ash, sewage sludge and wood ash, showing the following percentage adsorptions: Hg(II) >94 %, As(V) >96 % and Cr(VI) between 11 and 30 % for shell ash; Hg(II) >98 %, As(V) >88 % and Cr(VI) between 30 and 88 % for the waste mixture. Hg and As desorption was <5 % for both shell ash and the waste mixture, while Cr desorption was between 92 and 45 % for shell ash, and between 19 and 0 % for the mixture. In view of that, mussel shell ash and the mixture including shell ash, sewage sludge and wood ash could be useful for Hg(II) and As(V) removal.
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