22.4 Commonly Functionalized Biomaterials and Their Role in Remediation

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with only a few types of having oxide azo, which occur in nature. Photodegradation

of methyl orange was successfully demonstrated by Zainal et al. using combined

TiO2-chitosan/glass under illuminated visible light [19]. The modified double-layer

system made by chitosan functionalized on the glass then, TiO2, and epoxidized

natural rubber is used for the removal of “Reactive red 4” dye under illumination

[20]. Cellulose-based biopolymer doped with nanoparticles is widely used for

fabricating filter membranes and adsorption of various kinds of pollutants. A hybrid

film synthesized from flexible cellulose acetate coated with TiO2 is able to reduce

Methylene blue dye [21, 22]. Biopolymers having an affinity for metal binding

utilize elastin-like polypeptide made of single or double hexahistidine groups.

These configurable biopolymers preserve the feature of the elastin group even when

they undergo a phase transition at high temperature. Dynamic aggregation can be

achieved by adjusting the biopolymer’s length at varying temperatures. Cadmium

ions present in water attach to the biopolymer strongly due to the presence of

histidine group in polymer. Recovery of polymeric biomaterial can be ensured

by doping them with magnetic nanoparticles. Iron-doped chitosan fabricated by

electrospinning was successfully demonstrated by Min et al. for effective arsenic

filtration [23]. Similarly, numerous biopolymers can be tuned with variety of

nanoparticles for environmental remediation as the combination of biology with

chemistry has immense potential and never-ending possibilities.

22.4.2

Surfactants

Surfactants are the compounds that lower the surface tension between the liquid

and liquid/gas/solid. Surfactants are used in bionanotechnology for tuning the

surface properties and providing stability to nanoparticles. Surfactant as stabilizer

prevents agglomeration of nanoparticles by combined electrostatic and steric forces.

Surfactant-coated nanoparticles are generally used to clean up hydrocarbon-based

pollutants from the environment. The surfactant-conjugated nanoparticles and

their self-assembly help in combating various pollutants by interaction like π–π

stacking, charge-based binding, or hydrophobic effect. The zeolite nanoparticles

were modified with a cationic surfactant like hexadecyltrimethylammonium

chloride (HDTMA-Cl), and N-cetylpyridinium bromide (CPB) can be used to

separate various components of aromatic compounds occurring in petroleum-like

xylene, toluene, benzene, and ethylbenzene [24]. Silica and magnetic nanoparticles

like Fe3O4 are often pore-functionalized with cetyltrimethylammonium bromide

(CTAB) for the removal of PAH from water bodies [25]. Mesoporous silica nanopar-

ticles fabricated with hydroxypropyl-β-cyclodextrin or native β-cyclodextrin and

condensed tetraethyl orthosilicate, catalyzed with the help of acid and alkali,

can also be used for the removal of different PAH-based pollutants [26]. Many

microorganisms like Ustilagomaydis, Pseudomonas aeruginosa, Rhodococcus ery-

thropolis, Candida bombicola, Bacillus subtilis, Bacillus licheniformis, Acinetobacter

calcoaceticus, and Microbacterium produce biosurfactants like cellobiose lipids,

rhamnolipids, trehalose lipids, sophoro lipids, surafactin, lichenysin, emulsan

glycolipopeptide, and microbactan glycolipopeptide, respectively. Many of these