Sorbents loaded with organic contaminants are regenerated by heating, lowering the
pressure or washing with solvents (Sufnarski 1999). When thermal reactivation of
the sorbent occurs at temperatures higher than 800
C, a marginal loss of sorbent
material may occur for organics. Inorganic contaminants are usually removed in
presence of a concentrated solution of competing ions.
The selectivity of phenanthrene removal from micellar solutions using activated
carbon has been studied in details for several neutral surfactants and their mixtures
with sodium dodecylsulfate (Ahn et al. 2007, 2008a, b, 2010). The reported selectivity for phenanthrene adsorption with respect to surfactant was up to 95 and it was
enhanced as the fraction of anionic surfactant increased in the mixture of tensionactive agents. In spite of high surfactant recovery yields ranging from 88 to 96%
were obtained, often relatively low removal yields for phenanthrene, ranging from
24 to 70%, were reported, but it may reach up to 90% for pure sodium dodecylsulfate
(SDS) surfactant. The effect of mesh size for activated carbon particles was studied
and it was observed that the selectivity increased with the size of adsorbent.
However, the contaminant concentration plays a critical role with respect to removal
yield and selectivity and only phenanthrene concentrations as low as 10 mg l
À1 gave
very good results, while PAHs concentrations in soil leachates are rather about
several hundreds of mg l
À1 during washing or flushing operations. Moreover,
kinetics for phenanthrene adsorption from micellar wastewater is long, with halflive for fastest conditions of approximately 16 h, since surfactant adsorption is faster.
The long time required to achieve equilibrium concentrations and satisfactory
removal rates for contaminants is not very practical with respect to residence time
in wastewater treatment facilities and surfactant biodegradability. Finally, the cost
for activated carbon is similar to the one for surfactant. Besides, Wan (2011) report
the selective removal of hexachlorobenzene (80–99%) from soil leachates using
activated carbon at 10 g l
À1 and the simultaneous recovery of a rhamnolipid
surfactant ranging from 80 to 90%. Ion exchange using the chelating resins
Amberlite IRC 748 has been studied to recover several chelating agents, like
EDTA, bound to divalent metals in contaminated soil leachates (Ahmed Mohamed
et al. 2013). The treated solutions were reused up to seven times with ligand recovery
ranging from 30 to 100%, allowing metal extraction from soils as high as 80–97%
using millimolar solutions of chelating agents. It was shown that the low toxicity and
highly biodegradable iminodissuccinic acid (IDSA) was suitable for field works
since it was completely and shortly recovered, and was very effective to extract the
divalent metal ions from the spiked soil. Alcaline-earth cations did not perturb the
process because, on the one hand, the selectivity of IDSA and of the chelating resin
for MTEs and on the other hand, they were rapidly displaced from chelates by
MTEs. The main problem is associated with inert contaminants such as Ni
2+ , since
their removal from soil and then from the extracting agents needs longer contact
times which limit the process efficiency. This technology can be easily implemented
for wastewater treatment because it does not need any pH modification and it has a
low energy consumption. Metal recovery from resins was carried out at pH 2 in the
form of concentrated solutions before the electrolytic reduction of free metal cations.
1 Contaminant Mobilization from Polluted Soils: Behavior and Reuse of Leaching. . .
37
pressure or washing with solvents (Sufnarski 1999). When thermal reactivation of
the sorbent occurs at temperatures higher than 800
C, a marginal loss of sorbent
material may occur for organics. Inorganic contaminants are usually removed in
presence of a concentrated solution of competing ions.
The selectivity of phenanthrene removal from micellar solutions using activated
carbon has been studied in details for several neutral surfactants and their mixtures
with sodium dodecylsulfate (Ahn et al. 2007, 2008a, b, 2010). The reported selectivity for phenanthrene adsorption with respect to surfactant was up to 95 and it was
enhanced as the fraction of anionic surfactant increased in the mixture of tensionactive agents. In spite of high surfactant recovery yields ranging from 88 to 96%
were obtained, often relatively low removal yields for phenanthrene, ranging from
24 to 70%, were reported, but it may reach up to 90% for pure sodium dodecylsulfate
(SDS) surfactant. The effect of mesh size for activated carbon particles was studied
and it was observed that the selectivity increased with the size of adsorbent.
However, the contaminant concentration plays a critical role with respect to removal
yield and selectivity and only phenanthrene concentrations as low as 10 mg l
À1 gave
very good results, while PAHs concentrations in soil leachates are rather about
several hundreds of mg l
À1 during washing or flushing operations. Moreover,
kinetics for phenanthrene adsorption from micellar wastewater is long, with halflive for fastest conditions of approximately 16 h, since surfactant adsorption is faster.
The long time required to achieve equilibrium concentrations and satisfactory
removal rates for contaminants is not very practical with respect to residence time
in wastewater treatment facilities and surfactant biodegradability. Finally, the cost
for activated carbon is similar to the one for surfactant. Besides, Wan (2011) report
the selective removal of hexachlorobenzene (80–99%) from soil leachates using
activated carbon at 10 g l
À1 and the simultaneous recovery of a rhamnolipid
surfactant ranging from 80 to 90%. Ion exchange using the chelating resins
Amberlite IRC 748 has been studied to recover several chelating agents, like
EDTA, bound to divalent metals in contaminated soil leachates (Ahmed Mohamed
et al. 2013). The treated solutions were reused up to seven times with ligand recovery
ranging from 30 to 100%, allowing metal extraction from soils as high as 80–97%
using millimolar solutions of chelating agents. It was shown that the low toxicity and
highly biodegradable iminodissuccinic acid (IDSA) was suitable for field works
since it was completely and shortly recovered, and was very effective to extract the
divalent metal ions from the spiked soil. Alcaline-earth cations did not perturb the
process because, on the one hand, the selectivity of IDSA and of the chelating resin
for MTEs and on the other hand, they were rapidly displaced from chelates by
MTEs. The main problem is associated with inert contaminants such as Ni
2+ , since
their removal from soil and then from the extracting agents needs longer contact
times which limit the process efficiency. This technology can be easily implemented
for wastewater treatment because it does not need any pH modification and it has a
low energy consumption. Metal recovery from resins was carried out at pH 2 in the
form of concentrated solutions before the electrolytic reduction of free metal cations.
1 Contaminant Mobilization from Polluted Soils: Behavior and Reuse of Leaching. . .
37