(Hong et al. 2002). Saponin showed selectivity for target metals and mainly reacted
with heavy metals in fraction bound to carbonates and in fraction bound to Fe-Mn
oxides. The subsequent metal recovery was achieved by precipitation in alkaline
solution and reached 89.7%, 91.1% and 99.1% for Pb
2+ , Ni
2+ and Cr
3+ , respectively.
Batch extraction is a simple separation technique used in environmental analysis.
In its simplest form, a batch extraction system consists of an agitated mixing vessel
where the solids are being mixed with the solvent and a solid-liquid separation
device. Decanter centrifuges are advantageously used as separators (Berk 2013).
Song et al. (2008) conducted the batch experiments with soils spiked with phenanthrene and cadmium to evaluate pollutant removal efficacy of saponin. Phenanthrene
partitioned into a surfactant micelle, thus becoming directly bioavailable to
organisms capable of degrading PAHs, whereas Cd
2+ was effectively removed
from soil via its complexation with the external carboxyl groups of saponin micelle.
At saponin concentration of 3.75 g L
À1 , a removal yield of 87.7% for Cd
2+ and
76.2% for phenanthrene was obtained. The removal efficacy of saponin was greater
than that of Triton X-100 and citric acid. EDTA removed Cd
2+ effectively at low
concentration; however, this substance is quite persistent in the environment due to
its low biodegradability and may have a toxicity effect on soil microorganisms and
plants (Hauser et al. 2005). The removal of Cd
2+ was not constraining the removal of
phenanthrene which demonstrates a substantial potential of saponins for the removal
of heavy metals and PAHs from soils.
Cao et al. (2013) investigated the simultaneous desorption of metal elements (Pb
2
+
, Cu
2+ ) and polychlorinated biphenyl (PCB) from the combined contaminated soil
with a novel combination of saponin and S,S-ethylenediamine disuccinic acid
(EDDS) – an aminopolycarboxylic acid that can be used as a chelating agent, thus
offering a biodegradable alternative to synthetic EDTA (Kaushik 2015). The maximal desorption of contaminants was achieved by addition of 10 mmol L
À1 EDDS
and 3 g L
À1 saponin, and was 99.8%, 85.7% and 45.7% for Pb
2+ , Cu
2+ and PCB,
respectively. In the presence of the mixed solution of 5 mmol L
À1 EDTA and
20 mmol L
À1 Triton X-100, the maximal desorption was only 88%, 74.4% and
53.3% for Pb
2+ , Cu
2+ and PCB, respectively. These results suggest the combination
of saponin and EDDS may have practical application in remediation of soils
co-contaminated by hydrophobic organic compounds and metals.
5.5
Experimental: A Solid-Liquid Extraction with Synthetic
and Biological Surfactants for the Removal of Cu, Pb, Ni
and Zn from Contaminated Soils and Sediments
As an example of solid-liquid extraction with the use of synthetic and biological
surface-active agents for the removal of heavy metals from contaminated soils and
river sediments, the extraction of Cu, Pb, Ni and Zn with two synthetic non-ionic
surfactants Triton X-100 and Triton X-114 (octyl-phenoxy-poly-ethoxy-ethanol
with polyoxyethylene chain length of 9.5 and 7.5, respectively), biosurfactant
saponin (isolated from the bark of Quillaja saponaria tree) and secondary
5 The Recent Strategies Employed in Chemical Analysis of Contaminated Waters,. . .
155
with heavy metals in fraction bound to carbonates and in fraction bound to Fe-Mn
oxides. The subsequent metal recovery was achieved by precipitation in alkaline
solution and reached 89.7%, 91.1% and 99.1% for Pb
2+ , Ni
2+ and Cr
3+ , respectively.
Batch extraction is a simple separation technique used in environmental analysis.
In its simplest form, a batch extraction system consists of an agitated mixing vessel
where the solids are being mixed with the solvent and a solid-liquid separation
device. Decanter centrifuges are advantageously used as separators (Berk 2013).
Song et al. (2008) conducted the batch experiments with soils spiked with phenanthrene and cadmium to evaluate pollutant removal efficacy of saponin. Phenanthrene
partitioned into a surfactant micelle, thus becoming directly bioavailable to
organisms capable of degrading PAHs, whereas Cd
2+ was effectively removed
from soil via its complexation with the external carboxyl groups of saponin micelle.
At saponin concentration of 3.75 g L
À1 , a removal yield of 87.7% for Cd
2+ and
76.2% for phenanthrene was obtained. The removal efficacy of saponin was greater
than that of Triton X-100 and citric acid. EDTA removed Cd
2+ effectively at low
concentration; however, this substance is quite persistent in the environment due to
its low biodegradability and may have a toxicity effect on soil microorganisms and
plants (Hauser et al. 2005). The removal of Cd
2+ was not constraining the removal of
phenanthrene which demonstrates a substantial potential of saponins for the removal
of heavy metals and PAHs from soils.
Cao et al. (2013) investigated the simultaneous desorption of metal elements (Pb
2
+
, Cu
2+ ) and polychlorinated biphenyl (PCB) from the combined contaminated soil
with a novel combination of saponin and S,S-ethylenediamine disuccinic acid
(EDDS) – an aminopolycarboxylic acid that can be used as a chelating agent, thus
offering a biodegradable alternative to synthetic EDTA (Kaushik 2015). The maximal desorption of contaminants was achieved by addition of 10 mmol L
À1 EDDS
and 3 g L
À1 saponin, and was 99.8%, 85.7% and 45.7% for Pb
2+ , Cu
2+ and PCB,
respectively. In the presence of the mixed solution of 5 mmol L
À1 EDTA and
20 mmol L
À1 Triton X-100, the maximal desorption was only 88%, 74.4% and
53.3% for Pb
2+ , Cu
2+ and PCB, respectively. These results suggest the combination
of saponin and EDDS may have practical application in remediation of soils
co-contaminated by hydrophobic organic compounds and metals.
5.5
Experimental: A Solid-Liquid Extraction with Synthetic
and Biological Surfactants for the Removal of Cu, Pb, Ni
and Zn from Contaminated Soils and Sediments
As an example of solid-liquid extraction with the use of synthetic and biological
surface-active agents for the removal of heavy metals from contaminated soils and
river sediments, the extraction of Cu, Pb, Ni and Zn with two synthetic non-ionic
surfactants Triton X-100 and Triton X-114 (octyl-phenoxy-poly-ethoxy-ethanol
with polyoxyethylene chain length of 9.5 and 7.5, respectively), biosurfactant
saponin (isolated from the bark of Quillaja saponaria tree) and secondary
5 The Recent Strategies Employed in Chemical Analysis of Contaminated Waters,. . .
155