(Zhao et al. 2016). Various polymers/polyelectrolytes or mixture of polymers can be
used, such as starch (He and Zhao 2005), carboxymethyl cellulose (He and Zhao
2007; Dong et al. 2011), guar gum and xanthan gum (Tiraferri et al. 2008; Comba
et al. 2011a; Xue and Sethi 2012), butyl methacrylate or polymethacrylic acid (Sirk
et al. 2009), poly(4-styrenesulfonate) (Hydutsky et al. 2007), polymethylmethacrylate or polyacrylic acid (Laumann et al. 2013; Wang et al. 2013; Colombo
et al. 2015), polyethylene glycol (San Román et al. 2016), agar agar (Velimirovic
et al. 2016), polyphosphate (Kim et al. 2017), polyethylenimine (Lin et al. 2018), or
copolymers (Wang et al. 2017). The use of emulsified nZVI with a hydrophobic
membrane is also reported and applied in field experiments (Quinn et al. 2005;
Borden 2007; Berge and Ramsburg 2009). In addition, particles can be supported on
a solid (Fang et al. 2018), such as bentonite (Su et al. 2011), activated carbon such as
Carbo-Iron
® (Mackenzie et al. 2012), zeolite, carbon nanotubes (Xu et al. 2013),
membranes/resins (Xu and Bhattacharyya 2006; Ni and Yang 2014; Zhou et al.
2016), mesoporous silica (Sun et al. 2017), cellulose nanocrystal (Bossa et al. 2017),
or clay (Ezzatahmadi et al. 2017; Su et al. 2017). The use of activated carbon as
support can promote the sorption of hydrophobic pollutants to reduce the aqueous
concentration of the pollutant, and the interspecies electron transfer for the remediation process (Liu et al. 2012).
In addition to rheological characterization (Han et al. 2016a), zeta potential
measurements are good indicators of the stability of the particles. Stabilizers and
supports are also known to enhance the mobility of nZVI and mZVI particles to a
few meters in porous sand media and in heterogeneous aquifer sediment in column
(Hydutsky et al. 2007; Li et al. 2016b; Kumar et al. 2017) and field experiments
(Johnson et al. 2013; Kocur et al. 2014; Busch et al. 2015), as confirmed by
rheological characterization (Gastone et al. 2014). It has been possible to observe
high mobility of particles at low particles concentration (<30 mg L
À1 ) (Schrick et al.
2004; He et al. 2007; Saleh et al. 2008). However, surface modification is reported to
highly affect iron reactivity by site blocking, mass transfer inhibition, and interfacial
concentration decrease (Saleh et al. 2007; Phenrat et al. 2009a; Velimirovic et al.
2012, 2016). It is therefore important to investigate the best compromise between
concentration of surface modifier and iron available surface for reduction, such as
experimentations performed by Wang et al. (2015) for 2,4-dichlorophenol
dechlorination.
6.3.2.3 Polymetallic Particles
To improve ZVI reactivity, especially for the dechlorination of low molecular weight
chlorinated hydrocarbons, the use of polymetallic particles (nano- and microscale)
has been studied. Iron particles are generally coated with a second metal by its
reduction on iron surface in an ethanol solution (Wang and Zhang 1997). Other
techniques include radiolysis, mechanical alloying method, electrochemical synthesis, and green synthesis (Smuleac et al. 2011; Liu et al. 2014b; Luo et al. 2016; Weng
6 In Situ Chemical Reduction of Chlorinated Organic Compounds
309
used, such as starch (He and Zhao 2005), carboxymethyl cellulose (He and Zhao
2007; Dong et al. 2011), guar gum and xanthan gum (Tiraferri et al. 2008; Comba
et al. 2011a; Xue and Sethi 2012), butyl methacrylate or polymethacrylic acid (Sirk
et al. 2009), poly(4-styrenesulfonate) (Hydutsky et al. 2007), polymethylmethacrylate or polyacrylic acid (Laumann et al. 2013; Wang et al. 2013; Colombo
et al. 2015), polyethylene glycol (San Román et al. 2016), agar agar (Velimirovic
et al. 2016), polyphosphate (Kim et al. 2017), polyethylenimine (Lin et al. 2018), or
copolymers (Wang et al. 2017). The use of emulsified nZVI with a hydrophobic
membrane is also reported and applied in field experiments (Quinn et al. 2005;
Borden 2007; Berge and Ramsburg 2009). In addition, particles can be supported on
a solid (Fang et al. 2018), such as bentonite (Su et al. 2011), activated carbon such as
Carbo-Iron
® (Mackenzie et al. 2012), zeolite, carbon nanotubes (Xu et al. 2013),
membranes/resins (Xu and Bhattacharyya 2006; Ni and Yang 2014; Zhou et al.
2016), mesoporous silica (Sun et al. 2017), cellulose nanocrystal (Bossa et al. 2017),
or clay (Ezzatahmadi et al. 2017; Su et al. 2017). The use of activated carbon as
support can promote the sorption of hydrophobic pollutants to reduce the aqueous
concentration of the pollutant, and the interspecies electron transfer for the remediation process (Liu et al. 2012).
In addition to rheological characterization (Han et al. 2016a), zeta potential
measurements are good indicators of the stability of the particles. Stabilizers and
supports are also known to enhance the mobility of nZVI and mZVI particles to a
few meters in porous sand media and in heterogeneous aquifer sediment in column
(Hydutsky et al. 2007; Li et al. 2016b; Kumar et al. 2017) and field experiments
(Johnson et al. 2013; Kocur et al. 2014; Busch et al. 2015), as confirmed by
rheological characterization (Gastone et al. 2014). It has been possible to observe
high mobility of particles at low particles concentration (<30 mg L
À1 ) (Schrick et al.
2004; He et al. 2007; Saleh et al. 2008). However, surface modification is reported to
highly affect iron reactivity by site blocking, mass transfer inhibition, and interfacial
concentration decrease (Saleh et al. 2007; Phenrat et al. 2009a; Velimirovic et al.
2012, 2016). It is therefore important to investigate the best compromise between
concentration of surface modifier and iron available surface for reduction, such as
experimentations performed by Wang et al. (2015) for 2,4-dichlorophenol
dechlorination.
6.3.2.3 Polymetallic Particles
To improve ZVI reactivity, especially for the dechlorination of low molecular weight
chlorinated hydrocarbons, the use of polymetallic particles (nano- and microscale)
has been studied. Iron particles are generally coated with a second metal by its
reduction on iron surface in an ethanol solution (Wang and Zhang 1997). Other
techniques include radiolysis, mechanical alloying method, electrochemical synthesis, and green synthesis (Smuleac et al. 2011; Liu et al. 2014b; Luo et al. 2016; Weng
6 In Situ Chemical Reduction of Chlorinated Organic Compounds
309