for removal of salts in field soil. They concluded that overall removal efficiency was
not sufficiently higher because of the short operation time.
Most of the investigators (Cho et al. 2011; Jo et al. 2015) experienced a problem
with the removal of sulfate in the contaminated soil that directly affects electrical
conductivity and reduces the efficiency of the EK process. Sulfate is highly reactive
with available metal ions such as calcium, aluminum, iron, or magnesium ions
present in the contaminated soil. However, chloride and nitrate are easily removed
from the soil. Annamalai et al. (2015) successfully achieved more than 96% of
sulfate removal from a real contaminated soil collected from Tirupur, India, and
concluded that the pH of the electrolyte is vital in the removal of sulfate in actual
contaminated soil. The acidic pH of the electrolyte (0.01 M HCl) provoked the
ionization of the sulfate ion, which can be easily removed from the soil.
2.4 Electrokinetic Removal of Organic Dye Compounds
Ricart et al. (2008) initiated dye removal from an artificial soil, and recently
Annamalai et al. (2014a, b, 2016) tried to remove textile reactive dyes from a real
contaminated soil. It was established that the EK process is a useful technique for
elimination of these organic contaminants from a solid matrix. Several investigators
(Cameselle et al. 2013; Maini et al. 2000; Maturi and Reddy 2006; Ribeiro et al.
2005; Ricart et al. 2008; Wang et al. 2007) tried to remove uncharged organic
pollutants [PAH, trichlorobenzene (TCB)] from a model soil. The persistent organic
molecules, which are not soluble in water, became stuck in the voids of the porous
material and did not form ionized or ionic molecules. These organic molecules were
removed by electro-osmosis, the transport of organic pollutant along with pore fluid
water, but they cannot be removed by electromigration. The textile reactive dye
components are easily adsorbed on the surface of the soil, which can affect soil
quality. Generally, triazine and vinyl sulfone groups are the most important of the
reactive dyes (Carmen and Daniela 2010). The reactive dyes contain at least one
vinyl sulfone moiety (–SO 2 –CH¼CH 2 ) or a 2-sulfatoethylsulfone moiety (–SO 2 –
CH 2 –CH 2 –OSO 2 Na), which can be hydrolyzed into the vinyl sulfone moiety. The
reactive blue 19 (RB 19), copper phthalocyanine (Cu-Phy), reactive black 5 (RB 5),
etc., are important industrial dyes that are used frequently. RB 19, Cu-Phy, and RB
5 dyes are based on anthraquinone, porphyrin, and naphthalene group dyes, respectively, which are more resistant to biodegradation because of the fused aromatic
structures compared with azo-based reactive dyes (Pazos et al. 2008; Rajkumar et al.
2007). Pazos et al. (2008) explained the enhanced EK remediation of RB5 in
kaolinite-polluted model soil. When they tried to remove RB5 from the polluted
matrix, initially RB5 was removed by EK treatment, which was collected to the
anolyte chamber and simultaneously oxidized by an electrochemical process. In the
EK process, the electrolyte solution is the key parameter for enhancing the conductivity of the matrix and it favors the desorption of the pollutants from the surface of
the soil matrix. Without a pH adjustment in the EK process, removal efficiency was
8 Electro-bioremediation: An Advanced Remediation Technology for the. . .
195
not sufficiently higher because of the short operation time.
Most of the investigators (Cho et al. 2011; Jo et al. 2015) experienced a problem
with the removal of sulfate in the contaminated soil that directly affects electrical
conductivity and reduces the efficiency of the EK process. Sulfate is highly reactive
with available metal ions such as calcium, aluminum, iron, or magnesium ions
present in the contaminated soil. However, chloride and nitrate are easily removed
from the soil. Annamalai et al. (2015) successfully achieved more than 96% of
sulfate removal from a real contaminated soil collected from Tirupur, India, and
concluded that the pH of the electrolyte is vital in the removal of sulfate in actual
contaminated soil. The acidic pH of the electrolyte (0.01 M HCl) provoked the
ionization of the sulfate ion, which can be easily removed from the soil.
2.4 Electrokinetic Removal of Organic Dye Compounds
Ricart et al. (2008) initiated dye removal from an artificial soil, and recently
Annamalai et al. (2014a, b, 2016) tried to remove textile reactive dyes from a real
contaminated soil. It was established that the EK process is a useful technique for
elimination of these organic contaminants from a solid matrix. Several investigators
(Cameselle et al. 2013; Maini et al. 2000; Maturi and Reddy 2006; Ribeiro et al.
2005; Ricart et al. 2008; Wang et al. 2007) tried to remove uncharged organic
pollutants [PAH, trichlorobenzene (TCB)] from a model soil. The persistent organic
molecules, which are not soluble in water, became stuck in the voids of the porous
material and did not form ionized or ionic molecules. These organic molecules were
removed by electro-osmosis, the transport of organic pollutant along with pore fluid
water, but they cannot be removed by electromigration. The textile reactive dye
components are easily adsorbed on the surface of the soil, which can affect soil
quality. Generally, triazine and vinyl sulfone groups are the most important of the
reactive dyes (Carmen and Daniela 2010). The reactive dyes contain at least one
vinyl sulfone moiety (–SO 2 –CH¼CH 2 ) or a 2-sulfatoethylsulfone moiety (–SO 2 –
CH 2 –CH 2 –OSO 2 Na), which can be hydrolyzed into the vinyl sulfone moiety. The
reactive blue 19 (RB 19), copper phthalocyanine (Cu-Phy), reactive black 5 (RB 5),
etc., are important industrial dyes that are used frequently. RB 19, Cu-Phy, and RB
5 dyes are based on anthraquinone, porphyrin, and naphthalene group dyes, respectively, which are more resistant to biodegradation because of the fused aromatic
structures compared with azo-based reactive dyes (Pazos et al. 2008; Rajkumar et al.
2007). Pazos et al. (2008) explained the enhanced EK remediation of RB5 in
kaolinite-polluted model soil. When they tried to remove RB5 from the polluted
matrix, initially RB5 was removed by EK treatment, which was collected to the
anolyte chamber and simultaneously oxidized by an electrochemical process. In the
EK process, the electrolyte solution is the key parameter for enhancing the conductivity of the matrix and it favors the desorption of the pollutants from the surface of
the soil matrix. Without a pH adjustment in the EK process, removal efficiency was
8 Electro-bioremediation: An Advanced Remediation Technology for the. . .
195