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Chemical and environmental compatibility of red mud liners for hazardous waste containment
Rubinos, D. A.; Spagnoli, G. & Barral, M. T.
Abstract
Red mud residue from alumina production has
been proposed as an alternative liner material. The chemical
and environmental compatibility of red mud upon
exposure to representative organic (methanol, heptane,
TCE, and acetic acid) and inorganic liquids (CaCl2 and
seawater) was studied. Chemical compatibility assays
comprised Atterberg limits and sedimentation and
hydraulic conductivity tests for red mud interacted with the
chemical liquids, whereas the environmental compatibility
was assessed through the leaching of metals from red mud
as permeated with the liquids. Methanol greatly reduced
the plasticity at concentrations C80 % by volume, but it
did not increase the hydraulic conductivity of compacted
red mud. High concentrations (C60 % v/v) of acetic acid
reduced the plasticity and enhanced the sedimentation of
red mud. Conversely, acetic acid concentrations B40 %
caused dispersion, but damaged the hydraulic properties
and structure of red mud. The percolation of a pH 2 acetic
acid solution did not adversely affect the hydraulic performance
of the red mud liner. Neither diluted heptane nor
TCE affected the red mud. However, pure organics
suppressed the plasticity and induced aggregation of red
mud, suggesting a great detrimental effect on red mud
liners. The red mud exhibited great resistance to attack by
inorganic salt solutions. Some concerning leaching of
metals (primarily Al and Cr) occurred as water, acetic acid,
and CaCl2 solutions percolated through red mud, but
effluent metals concentration quickly dropped to permissible
levels. In general, red mud exhibited a high resistance
against chemical attack; nevertheless, exposure to low-dielectric-
constant organic chemicals should be avoided.
Keywords
Bauxite waste; Barrier; Hazardous chemicals; Permeability; Leaching; Environmental impact
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