172
large channels and cavities are able to accommodate a variety of ions, ranging from
monovalent to multivalent ones, while the ion exchange may be either diffusioncontrolled or electrochemically driven. While distribution coefficients are shown to
be key parameters in the diffusion driven process, resulting in high affinities of
PBAs toward metals such as Cs
+
, Tl
+
, Cu
2+
, and Zn
2+
, electrochemical ion exchange
is considered to be promising due to the effectiveness in the removal of metals and
the possibility to reversibly restore the adsorbent to its initial state. Related examples concerning the capture of Cs
+
from wastewaters and the recovery of rare earth
elements are herein presented and commented.
Keywords Prussian blue analogs · Cesium · Thallium · Ion exchange · Insertion
and release · Electrochemically driven ion exchange · Metal removal · Metal
sequestration · Metal uptake · Rare earth
7.1 Introduction
During the last decades, the increased request of energy worldwide and concerns
over global warming made the nuclear power as a carbon-free energy source contributing to the moderation of global warming. However, the occurrence of nuclear
accidents has warned us of the extent of radioactive waste. Several metals and radionuclides such as
134
Cs,
137
Cs,
90
Sr, and
131
I have been contaminated the environment
due to nuclear energy activities, causing irreversible damage not only to the environment but also to human health (Park et al. 2010; Abdi et al. 2008; Shi and
Fernandez-Jimenez 2006). Cesium, with its high solubility and mobility, can easily
combine with aquatic and terrestrial organisms. It can be therefore accumulated,
through the nutrition, into the human body and eventually placed into tissues
(Yasunari et al. 2011). Even nonradioactive cesium can be considered toxic since its
chemistry similar to the potassium one favors competition between the two ions in
biological interactions, possibly causing hyperirritability and spasms.
Among the methods nowadays used for the removal of radioactive
137
Cs from
liquid waste, precipitation, coagulation, membrane usage, and electrodialysis occupied a leading position (Iwanade et al. 2012). However, the process of choice for the
remediation of
137
Cs in contaminated water can be considered the adsorption: it is
simple and efficient as is capable of processing large volumes of radioactive liquid.
This requires a selection of the potential adsorbent. Silicotitanates (Liu et al. 2015a,
b), aluminum molybdophosphate and zeolites (Borai et al. 2009) have been extensively studied so far but their they poor Cs selectivity limits the application.
In this chapter, we highlight the efficacy of materials based on Prussian blue for
the large-scale remediation of wastewater due to pollution not only by cesium but
also by other metals, including the rare earth recovery and valorization.
M. Berrettoni et al.
large channels and cavities are able to accommodate a variety of ions, ranging from
monovalent to multivalent ones, while the ion exchange may be either diffusioncontrolled or electrochemically driven. While distribution coefficients are shown to
be key parameters in the diffusion driven process, resulting in high affinities of
PBAs toward metals such as Cs
+
, Tl
+
, Cu
2+
, and Zn
2+
, electrochemical ion exchange
is considered to be promising due to the effectiveness in the removal of metals and
the possibility to reversibly restore the adsorbent to its initial state. Related examples concerning the capture of Cs
+
from wastewaters and the recovery of rare earth
elements are herein presented and commented.
Keywords Prussian blue analogs · Cesium · Thallium · Ion exchange · Insertion
and release · Electrochemically driven ion exchange · Metal removal · Metal
sequestration · Metal uptake · Rare earth
7.1 Introduction
During the last decades, the increased request of energy worldwide and concerns
over global warming made the nuclear power as a carbon-free energy source contributing to the moderation of global warming. However, the occurrence of nuclear
accidents has warned us of the extent of radioactive waste. Several metals and radionuclides such as
134
Cs,
137
Cs,
90
Sr, and
131
I have been contaminated the environment
due to nuclear energy activities, causing irreversible damage not only to the environment but also to human health (Park et al. 2010; Abdi et al. 2008; Shi and
Fernandez-Jimenez 2006). Cesium, with its high solubility and mobility, can easily
combine with aquatic and terrestrial organisms. It can be therefore accumulated,
through the nutrition, into the human body and eventually placed into tissues
(Yasunari et al. 2011). Even nonradioactive cesium can be considered toxic since its
chemistry similar to the potassium one favors competition between the two ions in
biological interactions, possibly causing hyperirritability and spasms.
Among the methods nowadays used for the removal of radioactive
137
Cs from
liquid waste, precipitation, coagulation, membrane usage, and electrodialysis occupied a leading position (Iwanade et al. 2012). However, the process of choice for the
remediation of
137
Cs in contaminated water can be considered the adsorption: it is
simple and efficient as is capable of processing large volumes of radioactive liquid.
This requires a selection of the potential adsorbent. Silicotitanates (Liu et al. 2015a,
b), aluminum molybdophosphate and zeolites (Borai et al. 2009) have been extensively studied so far but their they poor Cs selectivity limits the application.
In this chapter, we highlight the efficacy of materials based on Prussian blue for
the large-scale remediation of wastewater due to pollution not only by cesium but
also by other metals, including the rare earth recovery and valorization.
M. Berrettoni et al.