reactivity terms. Yang and Chang (2011) analyzed the removal efficiency of emulsified nZVI combined with electrokinetic remediation technique, providing promising insights into the application of such integrated methods. Gomes et al. (2013)
tested the transport properties of polymer coated nZVI when it is combined with EK,
indicating that nZVI mobility in various porous media can be enhanced with the use
of direct current.
2.3.5 nZVI Supported on Various Materials
Immobilization and stabilization of highly active nZVI can be achieved by synthetically entrapping them onto a matrix. Aggregation phenomena are reported to be
considerably reduced when a matrix or the support material is used for the synthesis
of nZVI. In this case, nZVI possesses a higher specific area, colloidal stability,
homogeneous dispersion, and narrower size distribution (Ponder et al. 2000). Therefore, supported nZVI display higher activity compared with non-supported systems
(Ponder et al. 2001). Additionally, a support material can serve as a “host” for the
byproducts that are formed during the nZVI reaction with the pollutants, e.g.,
degraded pollutant/Fe(III) hydroxides precipitates. Thus, the surface of nZVI
remains longer and highly active.
The synthesis and investigation of the stability and mobility of nZVI has been
achieved with great results in the presence of various support materials such as clays
(Zhang et al. 2012; Üzüm et al. 2009; Wu et al. 2012; Olson et al. 2012), polymer
resins (Ponder et al. 2000, 2001), amorphous silica and silica sand (Oh et al. 2007;
Dorathi and Kandasamy 2012), exfoliated graphite (Zhang et al. 2006), watersoluble starch (He and Zhao 2005), cationic exchange membranes (Kim et al.
2008), cellulose acetate membranes (Meyer et al. 2004), alginate bead (Kim et al.
2010), activated carbon (Mackenzie et al. 2012), mesoporous silica (OMS) (Li et al.
2011), mesoporous silica microspheres (Qiu et al. 2011), nanostructured silica
SBA-15 (Saad et al. 2010), zeolites (Zhang et al. 2002), chitosan (Geng et al.
2009; Liu et al. 2012), graphene, and ordered mesoporous carbon (Ling et al.
2012). In Table 2.3 are listed some of the support materials and their functions
that have been used according the literature; in Fig. 2.10 are shown some results that
compare the efficacy of bare nZVI with supported nZVI.
Besides the benefits that arise from limiting the aggregation of nZVI, synergetic
effects can boost the total degradation ability of these materials even more
(Table 2.4). When an appropriate support material is used, absorption; reduction;
or photocatalytic properties can be added and multiply the effects. Thus, the use of a
support material is a matter of high technological importance because it can extend
the use and sustainability of nZVI. Moreover, the range of the targeted pollutants can
be widened, involving nZVI in a larger variety of environmental scenarios.
2 Nanoscale Zero-Valent Iron Particles for Water Treatment: From Basic. . .
37
tested the transport properties of polymer coated nZVI when it is combined with EK,
indicating that nZVI mobility in various porous media can be enhanced with the use
of direct current.
2.3.5 nZVI Supported on Various Materials
Immobilization and stabilization of highly active nZVI can be achieved by synthetically entrapping them onto a matrix. Aggregation phenomena are reported to be
considerably reduced when a matrix or the support material is used for the synthesis
of nZVI. In this case, nZVI possesses a higher specific area, colloidal stability,
homogeneous dispersion, and narrower size distribution (Ponder et al. 2000). Therefore, supported nZVI display higher activity compared with non-supported systems
(Ponder et al. 2001). Additionally, a support material can serve as a “host” for the
byproducts that are formed during the nZVI reaction with the pollutants, e.g.,
degraded pollutant/Fe(III) hydroxides precipitates. Thus, the surface of nZVI
remains longer and highly active.
The synthesis and investigation of the stability and mobility of nZVI has been
achieved with great results in the presence of various support materials such as clays
(Zhang et al. 2012; Üzüm et al. 2009; Wu et al. 2012; Olson et al. 2012), polymer
resins (Ponder et al. 2000, 2001), amorphous silica and silica sand (Oh et al. 2007;
Dorathi and Kandasamy 2012), exfoliated graphite (Zhang et al. 2006), watersoluble starch (He and Zhao 2005), cationic exchange membranes (Kim et al.
2008), cellulose acetate membranes (Meyer et al. 2004), alginate bead (Kim et al.
2010), activated carbon (Mackenzie et al. 2012), mesoporous silica (OMS) (Li et al.
2011), mesoporous silica microspheres (Qiu et al. 2011), nanostructured silica
SBA-15 (Saad et al. 2010), zeolites (Zhang et al. 2002), chitosan (Geng et al.
2009; Liu et al. 2012), graphene, and ordered mesoporous carbon (Ling et al.
2012). In Table 2.3 are listed some of the support materials and their functions
that have been used according the literature; in Fig. 2.10 are shown some results that
compare the efficacy of bare nZVI with supported nZVI.
Besides the benefits that arise from limiting the aggregation of nZVI, synergetic
effects can boost the total degradation ability of these materials even more
(Table 2.4). When an appropriate support material is used, absorption; reduction;
or photocatalytic properties can be added and multiply the effects. Thus, the use of a
support material is a matter of high technological importance because it can extend
the use and sustainability of nZVI. Moreover, the range of the targeted pollutants can
be widened, involving nZVI in a larger variety of environmental scenarios.
2 Nanoscale Zero-Valent Iron Particles for Water Treatment: From Basic. . .
37