en |
Potential of anthracite, dolomite, limestone and pozzolan as reactive media for de-icing salt removal from road runoff
Santiago-Martın, A. de; Michaux, A.; Guesdon, G.; Constantin, B.; Despréaux, M. & Galvez-Cloutier, R.
Abstract
De-icing salt (NaCl) application is a common
practice during winter road maintenance in northern
countries, compromising ecosystem services. Ecoengineering
facilities, including reactive filter beds, are
becoming an effective strategy for road runoff management.
Different materials (anthracite coal, dolomite, limestone,
and pozzolan) were tested as reactive media of filter
beds. Characterization showed that dolomite has the best
physical properties (resistance to fragmentation, porosity)
for filter bed construction and maintenance, followed by
limestone. NaCl removal efficiency was investigated in
batch at different concentrations (150–5000 mg L-1 Cl).
Removal efficiency substantially varied depending on the
element (Cl or Na), the material, and the added NaCl
concentration. At the lowest NaCl concentration, Cl
removal was higher onto anthracite (48 %) and dolomite
(59 %); but greater Na removal was reached onto limestone
(54 %) and pozzolan (67 %). At higher concentrations,
Cl removal was similar (anthracite), decreased
(dolomite), or increased (limestone, pozzolan); and Na
removal increased (anthracite) or decreased (dolomite,
limestone, pozzolan). Parallel experiments at 4 °C showed
lower NaCl removal, anthracite being the most efficient.
Practical applicability was evaluated in columns using
synthetic runoff solution (NaCl and metals). NaCl removal
efficiency was much lower in column assays with respect
to batch. The highest NaCl removal was reached onto
dolomite, followed by limestone. Metals were successfully
removed, generally remaining over time in a wide range
(41–89 % Cd, 78–97 % Ni, 44–88 % Cu, and 3–83 % Zn)
depending on the material, being pozzolan the least efficient.
Further studies including a combination of materials
would be of high interest.
Keywords
Adsorption; Filter beds; Geomaterials; Highway pollution; NaCl; Surface water; Trace metals
|