Page 473 - Polymer-based Nanocomposites for Energy and Environmental Applications

426 Polymer-based Nanocomposites for Energy and Environmental Applications

No doubt extensive research has been made in the preparation and characterization
of novel nanostructured polymer-based membranes. However, a careful evaluation
on the limitation of each membrane is required such as material availability, cost,
ease of processing, compatibility, scale-up prospect, and safety risks related with
nanomaterials.

15.10 Sodium titanate nanobelt membrane (Na-TNB)

In many useful applications, ion exchange is one of the most commonly used techno-
logies for the removal of toxic materials and the collection of valuable elements from
water [155].
Many ion exchangers have been extensively used for the removal of heavy metals
in wastewater and especially for the decontamination of radioactive waste generated
from nuclear accidents or uranium mining [156,157].
Additionally, in the nuclear industry, ion exchange is also the most promising
technique to transfer the radioactive content of a large volume of liquid into a small
volume of solid that can be hired in a given amount of repository space. Besides these,
organic resins have been extensively employed as ion exchangers for these
causes [158].
But recently, a novel class of materials, namely, titanate and its derivatives, has
2+
2+
paid much attention as they have strong affinity for heavy metal ions (Pb ,Cu ,
2+
and Hg ) and extremely an effective scavenger for radionuclides [159].
A numerous ordinary inorganic ion exchangers, such as titanate-based materials,
layeredmetalsulfideframeworks,clayminerals,andzeolite-associatedmaterials,have
been effectively employed for the removal of radionuclides from nuclear
wastewater [160].
Titanates, innovative layered materials with unique ion-exchange properties, have
the advantages over the traditional organic ion-exchange resins owing to their higher
resistance to thermal contact and radiation [158].
Nevertheless, all these layered materials have certain drawbacks that limit their
experimental applications:
(a) Time-consuming, in order to reach the sorbent-solution equilibrium.
(b) The interlayer ions cannot be substituted out completely, consequent in less exchange
capacities.
(c) After the collapse of layered structure, the renewal of materials and the recovery of
entrapped cations can scarcely be achieved, which limits their applications in the collection
of valuable cations and leads to a contamination of materials.

Consequently, in layered materials, the mechanism of the ion exchange and the factors
affecting the efficiency and selectivity of the ion exchange need to be explored further.
In this regard, Wen et al. [161] invented a multifunctional elastic free-standing
sodium titanate nanobelt (Na-TNB) membrane that was collected as progressive
radiation-contaminated water treatment and oil uptake. Under different environ-
+
mental circumstances, the adsorption performance of 137 Cs and 90 Sr 2+ on Na-TNB
membranes was investigated. A supreme adsorption coefficient value was extended