For organophosphates pesticides such as parathion methyl the degradation is fast
(half-life 0.9 min), in a pseudo-first-order behavior (Šťastný et al. 2016). The
reactions involve cleavage of the P–O-aryl bond in the pesticide molecule in
nonpolar solvent. The reaction mechanisms are similar to hydrolysis since the –
OH groups on the surface of the sorbent MnO 2 act as a very strong nucleophile
toward P atoms. The final degradation products are mainly composed of
4-nitrophenol.
7.4.4 Types of Useful Mn Oxides for Soil Remediation
This review pointed out the wide variety of Mn oxides that can be used for
decontamination and soil remediation. Natural Mn oxides come from mine tailings,
natural ores, or Mn-removing water treatment works (Bagherifam et al. 2014; Clarke
et al. 2010; McCann et al. 2015; O’Reilly and Hochella Jr 2003). Mn oxides can also
be synthetized to better control their properties. Synthesis of amorphous Mn oxides
allows the formation of high specific surfaces (Ettler et al. 2015). The synthetic Mn
oxides used for remediation have generally a poorly crystalline structure (δ-MnO 2 ),
equivalent to birnessite-family minerals with a layer structure (Ettler et al. 2015; Gao
et al. 2012; O’Reilly and Hochella Jr 2003). Tunnel structure such as cryptomelane
is also interesting for Pb decontamination and the degradation of chemical warfare
agents (O’Reilly and Hochella Jr 2003; Stengl et al. 2012). The specificity of the
synthetic Mn oxides allows efficient decontamination, generally better than the
natural Mn oxides (see O’Reilly and Hochella Jr 2003 for Pb). However, wellchosen natural Mn oxides, i.e., with a well-characterized structure, can have very
efficient remediation potentials (McCann et al. 2015).
A novel and promising remediation technique using the properties of Mn oxides
is based on Mn oxide nanoparticles. Nanoparticles can be used for oxidation of
organic compounds (Han et al. 2015), reactive sorption of chemical warfare agents
(Mahato et al. 2010; Prasad et al. 2007a, b), or metal/metalloid sorption (Michalkova
et al. 2014; Xie et al. 2015). These engineered nanoparticles have a local structure
similar to birnessite (Han et al. 2015). Nanoparticles can associate Mn oxides to
other compounds such as ceria, iron oxides, and graphite (Gupta et al. 2011; Luo
et al. 2012). Such composite nanoparticles are efficient for As immobilization, since
they increase its sorption behavior.
It is also interesting to note that for As removal, Mn oxides can be used as a load
in a polystyrene matrix for a better As immobilization (Lenoble et al. 2004). Several
studies also exist on engineered biochar–Mn oxide composites that enhance adsorption properties of original biochar for As (Yu et al. 2015), Cu (Song et al. 2014), and
Pb (Wang et al. 2015b).
A summary of the potential uses of Mn oxides for soil remediation, as well as the
type of Mn oxides and the maturity of each technique are listed in Table 7.3.
7 The Nature of Manganese Oxides in Soils and Their Role as Scavengers of Trace. . .
419
(half-life 0.9 min), in a pseudo-first-order behavior (Šťastný et al. 2016). The
reactions involve cleavage of the P–O-aryl bond in the pesticide molecule in
nonpolar solvent. The reaction mechanisms are similar to hydrolysis since the –
OH groups on the surface of the sorbent MnO 2 act as a very strong nucleophile
toward P atoms. The final degradation products are mainly composed of
4-nitrophenol.
7.4.4 Types of Useful Mn Oxides for Soil Remediation
This review pointed out the wide variety of Mn oxides that can be used for
decontamination and soil remediation. Natural Mn oxides come from mine tailings,
natural ores, or Mn-removing water treatment works (Bagherifam et al. 2014; Clarke
et al. 2010; McCann et al. 2015; O’Reilly and Hochella Jr 2003). Mn oxides can also
be synthetized to better control their properties. Synthesis of amorphous Mn oxides
allows the formation of high specific surfaces (Ettler et al. 2015). The synthetic Mn
oxides used for remediation have generally a poorly crystalline structure (δ-MnO 2 ),
equivalent to birnessite-family minerals with a layer structure (Ettler et al. 2015; Gao
et al. 2012; O’Reilly and Hochella Jr 2003). Tunnel structure such as cryptomelane
is also interesting for Pb decontamination and the degradation of chemical warfare
agents (O’Reilly and Hochella Jr 2003; Stengl et al. 2012). The specificity of the
synthetic Mn oxides allows efficient decontamination, generally better than the
natural Mn oxides (see O’Reilly and Hochella Jr 2003 for Pb). However, wellchosen natural Mn oxides, i.e., with a well-characterized structure, can have very
efficient remediation potentials (McCann et al. 2015).
A novel and promising remediation technique using the properties of Mn oxides
is based on Mn oxide nanoparticles. Nanoparticles can be used for oxidation of
organic compounds (Han et al. 2015), reactive sorption of chemical warfare agents
(Mahato et al. 2010; Prasad et al. 2007a, b), or metal/metalloid sorption (Michalkova
et al. 2014; Xie et al. 2015). These engineered nanoparticles have a local structure
similar to birnessite (Han et al. 2015). Nanoparticles can associate Mn oxides to
other compounds such as ceria, iron oxides, and graphite (Gupta et al. 2011; Luo
et al. 2012). Such composite nanoparticles are efficient for As immobilization, since
they increase its sorption behavior.
It is also interesting to note that for As removal, Mn oxides can be used as a load
in a polystyrene matrix for a better As immobilization (Lenoble et al. 2004). Several
studies also exist on engineered biochar–Mn oxide composites that enhance adsorption properties of original biochar for As (Yu et al. 2015), Cu (Song et al. 2014), and
Pb (Wang et al. 2015b).
A summary of the potential uses of Mn oxides for soil remediation, as well as the
type of Mn oxides and the maturity of each technique are listed in Table 7.3.
7 The Nature of Manganese Oxides in Soils and Their Role as Scavengers of Trace. . .
419