Page 455 - Polymer-based Nanocomposites for Energy and Environmental Applications

412 Polymer-based Nanocomposites for Energy and Environmental Applications

15.4 Nanomembrane combined with biodegradable
poly-gamma-glutamic acid (γ-PGA)

For human use and other vital processes, water pollution includes all of those com-
pounds that alter the quality of groundwater and surface water, therefore decreasing
the suitability of natural water. These compounds are produced by human activities,
especially those that are industrial, agricultural, and domestic.
Nowadays, hazardous waste materials comprising heavy metals have added in the
environment in appreciable amounts as a result of the rapid development of industry, a
practice that (though perhaps to a reduced extent) is ongoing. At low concentrations,
contamination of water by toxic heavy metals has become an increasingly serious
environmental and health problem [59]. Lead (Pb) is considered as one of the most
toxic among all most 20 heavy toxic metals. It is not biodegradable, and it can store
in the environment and in the body, indorsing diseases containing hypertension,
kidney failure, and nervous diseases through its nephron and neurotoxicity, respec-
tively [60]. To remove these toxic heavy metals from water, various methods have
been industrialized, including adsorption, complexation, ion exchange, chemical
precipitation, and membrane filtration.
Membrane filtration is progressively employed as a water and wastewater treat-
ment process for the removal of heavy metals [61]. Likewise, ultra- and nanofiltration
are extensively used because of their high separation selectivity and low-energy,
low-pressure, and room-temperature operational parameters. Currently, great effort
has been made to study heavy metal removal through surfactant [62], micellar [63]
or complexation-assisted filtration [64], and polyelectrolyte-enhanced [65] and
polymer-enhanced membrane filtration [66]. Biopolymers are extensively available
that are biocompatible or biodegradable and, therefore, eco-friendly, and because
of the presence of functional groups, they are capable of binding metal ions even
at low concentrations. These Pb biopolymers to growing interest in biosorption field
[67]. Biopolymers as adsorbents such as poly-γ-glutamic acid (γ-PGA) [68] and some
others [69,70] have been widely studied for the removal of heavy metals in water
treatment.
γ-PGA is a water-soluble, biodegradable, edible, and nontoxic biopolymer that
contains repetitive glutamic acid units connected by amide linkages between α-amino
and γ-carboxylic acid functional groups [71]. γ-PGA and its derivatives have been
employed in a wide range of industrial application, containing cosmetics, food,
medicine, and water treatment [72,73].
Radu et al. [74] prepared and characterized nanosized cross-linked γ-PGA particles
under various conditions to facilitate the planning of different applications for these
particles.
Similarly, Hajdu et al. [75] investigated the removal of toxic Pb ions from aqueous
solution using a combined nanomembrane separation technique. To capture the metal
ions by forming nanosized particles, biodegradable γ-PGA, linear biopolymer, and
its cross-linked nanoparticles were employed. The polymer-metal ion particles,
with sizes in the range of 80–350 nm, were then removed by membrane separation.