186
7.2.4 Prussian Blue as Medical Treatment for Cesium
and Thallium Poisoning
Because of the high affinity for cesium and thallium cations (Zadronecki et al.
2001), Prussian blue has found therapeutical applications as a medical treatment of
people poisoned by radioactive cesium or thallium. The health and environmental
hazard of Cs-137 concerns the radioactive decays which produce γ photons and β
particles. Capsules of Prussian blue have been approved by the US Food and Drug
Administration as the active chemical in Radiogardase
®
(Heyltex Corporation,
Katy, TX) and a study performed by Faustino et al. (2008) pointed out the basic
physicochemical phenomenon at the basis of the cesium and Prussian blue binding.
Thallium intoxication is considered mainly accidental and the second most frequent cause of human poisoning. The main chemical form of thallium is thallium sulfate (Tl 2 SO 4 ) which is colorless, tasteless, and odorless. Thallium sulfate
might still be used nowadays as rodenticide, so accidental human poisoning is possible. In analogy with the cesium, thallium also is retained from and dispersed
throughout the body, mimicking the potassium uptake, but blocking its enzymatic
action. Kravzov et al. (1993) studied the effect of the crystalline size and the morphology of several different Prussian blue analogs on their medical efficacy, exploiting in vivo experiments, verifying that the smaller the size the better the capacity.
7.2.5 Rare Earth Element Recovery and Valorization by
Metal Hexacyanoferrates
The use of rare earth elements in the electronic industry is growing. For instance,
digital displays are fabricated by using rare earth oxides. The limited availability of
rare earth elements also plays a decisive role in the current geopolitics. In this perspective, their recovery from waste of the electronic industry can be valuable from
both the environmental and the social perspectives. In the earth’s crust rare earth
elements are not available as free metals but as minerals, containing various rare
earth metals combined to other transition metals. Therefore, there is a strong motivation in searching for technologies for the recovery and valorization of rare earth
elements from waste of the electronic industry.
A recent paper reports the ability of the nickel hexacyanoferrate to host in reversible way cations with nominal charge up to 3
+
, namely, Al
3+
, Cr
3+
, In
3+
, Gd
3+
, and
Er
3+
(Ciabocco et al. 2018). This feature makes the nickel hexacyanoferrate a suitable material for all electrochemical processes based on the host/guest mechanism
also involving trivalent cations. The procedure here proposed allows a separation
erbium (III) by means of a two-step electrochemical process.
The proof of concept is visualized in the Fig. 7.7 which displays the polarization
profile of a nickel hexacyanoferrate film cycled in 1.0 M KNO 3 . The observed electrochemical response is due to the K 2 Ni
II
[Fe
II
(CN) 6 ] and KNi
II 1.5 [Fe
II
(CN) 6 ] phases
M. Berrettoni et al.
7.2.4 Prussian Blue as Medical Treatment for Cesium
and Thallium Poisoning
Because of the high affinity for cesium and thallium cations (Zadronecki et al.
2001), Prussian blue has found therapeutical applications as a medical treatment of
people poisoned by radioactive cesium or thallium. The health and environmental
hazard of Cs-137 concerns the radioactive decays which produce γ photons and β
particles. Capsules of Prussian blue have been approved by the US Food and Drug
Administration as the active chemical in Radiogardase
®
(Heyltex Corporation,
Katy, TX) and a study performed by Faustino et al. (2008) pointed out the basic
physicochemical phenomenon at the basis of the cesium and Prussian blue binding.
Thallium intoxication is considered mainly accidental and the second most frequent cause of human poisoning. The main chemical form of thallium is thallium sulfate (Tl 2 SO 4 ) which is colorless, tasteless, and odorless. Thallium sulfate
might still be used nowadays as rodenticide, so accidental human poisoning is possible. In analogy with the cesium, thallium also is retained from and dispersed
throughout the body, mimicking the potassium uptake, but blocking its enzymatic
action. Kravzov et al. (1993) studied the effect of the crystalline size and the morphology of several different Prussian blue analogs on their medical efficacy, exploiting in vivo experiments, verifying that the smaller the size the better the capacity.
7.2.5 Rare Earth Element Recovery and Valorization by
Metal Hexacyanoferrates
The use of rare earth elements in the electronic industry is growing. For instance,
digital displays are fabricated by using rare earth oxides. The limited availability of
rare earth elements also plays a decisive role in the current geopolitics. In this perspective, their recovery from waste of the electronic industry can be valuable from
both the environmental and the social perspectives. In the earth’s crust rare earth
elements are not available as free metals but as minerals, containing various rare
earth metals combined to other transition metals. Therefore, there is a strong motivation in searching for technologies for the recovery and valorization of rare earth
elements from waste of the electronic industry.
A recent paper reports the ability of the nickel hexacyanoferrate to host in reversible way cations with nominal charge up to 3
+
, namely, Al
3+
, Cr
3+
, In
3+
, Gd
3+
, and
Er
3+
(Ciabocco et al. 2018). This feature makes the nickel hexacyanoferrate a suitable material for all electrochemical processes based on the host/guest mechanism
also involving trivalent cations. The procedure here proposed allows a separation
erbium (III) by means of a two-step electrochemical process.
The proof of concept is visualized in the Fig. 7.7 which displays the polarization
profile of a nickel hexacyanoferrate film cycled in 1.0 M KNO 3 . The observed electrochemical response is due to the K 2 Ni
II
[Fe
II
(CN) 6 ] and KNi
II 1.5 [Fe
II
(CN) 6 ] phases
M. Berrettoni et al.