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Mechanisms Controlling the Leaching Kinetics of Fixated Flue Gas Desulfurization (FGD) Material under Neutral and Acidic Conditions
Author(s) -
Cheng ChinMin,
Walker Harold W.,
Bigham Jerry M.
Publication year - 2007
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0327
Subject(s) - leaching (pedology) , flue gas desulfurization , dissolution , chemistry , lixiviant , chemical engineering , flue gas , chemical reaction , lessivage , kinetics , mineralogy , organic chemistry , soil water , environmental science , soil science , engineering , physics , quantum mechanics
A number of agricultural and engineering uses for fixated flue gas desulfurization (FGD) material exist; however, the potential for leaching of hazardous elements has limited widespread application and the processes controlling the leaching of this material are poorly understood. In this study, a flow‐through rotating‐disk system was applied to elucidate the relative importance of bulk diffusion, pore diffusion, and surface chemical reaction in controlling the leaching of fixated FGD material under pH conditions ranging from 2.2 to 6.8. Changing the hydrodynamics in the rotating disk system did not affect the leaching kinetics at both pH 2.2 and 6.8, indicating that bulk diffusion was not the kinetic‐limiting step. Application of the shrinking core model (SCM) to the data suggested a surface reaction‐controlled mechanism, rather than a pore diffusion mechanism. The leaching of fixated FGD material increased with decreasing pH, suggesting it can be described by a combination of an intrinsic hydration reaction and a proton‐promoted dissolution reaction. X‐ray diffraction (XRD) and elemental composition analyses before and after leaching suggests that for most elements a number of solid phases controlled the leaching process.