Page 47 - ACCB 2020

Nanotechnology for Combating Microbial Contamination. do Nascimento et al

nostructures (CNS) are important materials to interact exfoliation to synthesize graphene sheets which are si-
with organic or hydrophobic pollutants (44,45). In this milar to the common water fi lters (64). Those materials
regard, carbon nanotubes (CNTs) were one of the fi rst were used for simultaneous removal of species of arse-
CNS used for the adsorption of pollutants (46). Indeed, nic and sodium from aqueous solution. Additionally, the
+
the high surface area provides potential to adsorb con- membranes were used for desalination of seawater (Na ,
2+
+
taminants such as complexes of benzene, toluene, and Mg , Ca , K ). Both applications were successful for
2+
xylene (BTX) (47) and trihalomethanes (THMs)(48, the removal of almost 60% of all studied cations. These
49). However, in the aqueous medium, CNTs form bun- preliminary data encourage the application of CNS into
dle (50) that decreases its effective surface area, and as the pre-concentration of metals, as well as obtainment
a consequence, could affect its adsorption capacity (51). of multifunctional nanocomposites.
Nevertheless, those aggregates present high adsorption
energy sites through its interstitial spaces and groves CNS application into water and wastewater treatment
created during this aggregation process. CNTs are more is not limited to the adsorption of heavy metals or des-
effi cient adsorbent than activated carbon (AC) in the alination. CNSs have been used to adsorb dyes, antibio-
same condition and same surface area (52). tics, among others from water (65). Thus, anthraquino-
ne dye, Reactive blue 29 (RB29), were removed from
Another advantage of CNTs is its functionalization that water by advanced oxidation process that also results in
generates new functional groups at the external surfa- a sub-product with high interaction in CNT’s curvature
ce. These groups can also promote better dispersion at zone (66) known as a region of high energy at CNTs.
the water, as well as, creation of hydrogen bonds with Furthermore, Fan et al (67) removed methylene blue
hydrophilic pollutants, such as antibiotics (53), hor- from water combining chitosan with GO.
mones (54), and cations of heavy metals (55), among
others. Despite its great adsorption capacity, CNTs need Inorganic nanoparticles (e.g. iron oxide, titanium dioxi-
an immobilizing matrix (56) to avoid its spreading at de, among others) also play an important role in the
potable water or wastewater with the potential produc- adsorption of contaminants from water because of its
tion of secondary contaminants by interaction with the low-cost production and high interaction with cations
recalcitrant pollutant. Thus, functionalization of CNTs of heavy metals. Magnetic iron oxide nanoparticles
with specifi c functional groups (e.g. carboxylic acids, (magnetite) are gaining considerable attention from
amides, amines, phenols, etc.) with the creation of com- the scientifi c community regarding its application into
posites, allows targeting of special contaminants (e.g. water and wastewater treatment as a result of its high
pesticides) as well as its use into sensors (28,57) or biocompatibility and safe degradation by environment
photocatalytic materials (58). In as much, those applica- (68,69). Therefore, those NPs have been used for arse-
tions need a small quantity of CNTs for high effi ciency. nic removal from water (70). Thus, by controlling its
size it was also possible to increase the adsorption ca-
Compared to CNTs, graphene oxide (GO) and reduced pacity of arsenic up to 100 times. Such adsorption was
graphene oxide (RGO) have demonstrated exceptional also attributed to the “nanoscale effect” which change
adsorbent capacity (59,60) Their advantage over CNTs nanoparticles surface creating new sites for adsorption.
consists of generation of self-supported materials (61) For instance, Fe-S nanocomposite was shown to remo-
as well as, in the case of GO also has shown the natural ve cadmium up to a greater extent as compared to the
presence of functional groups at its surface (62). In this pure adsorbents. In this case, the adsorption rate rea-
regard, Yang et al (63) interacted GO with solutions of ched over 98.5% at pH 7, resulting in the fast removal
CuCl and observed its immediate aggregation confi r- of cadmium from water (71). Moreover, by dramatica-
2
med by UV-Vis spectra, which showed a peak at 800 lly size decreasing (below ~40 nm), magnetite can turn
2+.
nm that corresponds to Cu Likewise, a complemen- from magnetic to supermagnetic nanoparticles having
+
tary experiment for the interaction of GO with Na was high magnetic susceptibility. Superparamagnetic iron
performed (with equivalent ion strength) that showed oxide nanoparticles (SPIONS) have been used to adsorb
electrostatic interaction instead of aggregation; indica- ions of heavy metals,(72), as well as other inorganic po-
ting that, GO could be useful for selective removal of llutants (73). However, the main application of SPIONS
Cu . into water treatment depends upon functionalization at
2+
its surface. Indeed, silica core-shell SPIONS are an in-
Mishra and Ramaprabhu applied hydrogen inducted teresting platform for trapping complexes or emergent

47
Rev. Asoc. Col. Cienc.(Col.), 2020; 32: 42-62.