Page 48 - ACCB 2020

Revista de la Asociación Colombiana de Ciencias Biológicas
issn impreso 0120-4173, issn en línea 2500-7459
contaminants (74). composite which exhibited similarity with fi lter papers.

Although each nanostructure described above shows 4.2. Nanoparticles with photocatalytic activity for
exceptional properties for adsorption of several types water and wastewater decontamination
of contaminants from water and wastewater, they also Alternatively, to adsorb contaminants from water and
show limitations that involve cost of production, low wastewater, NPs have been used as photocatalyst mate-
dispensability at water, need of physical support for rials to degrade contaminants. It is observed that the ex-
water fi ltration or pollutant aggregation. In this regard, tracellular polymeric substance of bacterial cells is res-
nanocomposites are important since they combine pro- ponsible for the development of resistance against the
perties from NPs with other materials or from two or antimicrobial activity of catalyst through the bacterici-
more nanoparticles. Thereafter, the application of na- dal activity of photocatalyst. Hence, during wastewater
nocomposites into water decontamination has been ex- treatment, removal of such extracellular material from
tensively reported. Thus, Qin et al reported adsorption bacterial biofi lm could help the antimicrobial activity
of rhodamine B (RhB), a traditional dye, by using na- of photocatalysts (78). In this regard, nano - titanium
nocomposites made of reduced graphene oxide (RGO) dioxide (TiO2) is commonly deposited on surfaces ai-
and SPIONS (75). This nanocomposite was obtained by ming photodegradation of compounds such as phenols
in situ technique that GO was added into SPIONS’ syn- (79), volatile compounds (VOCs) (80), dyes,(81).
thesis medium. In the same environment, GO was redu-
ced by the addition of ammonium hydroxide. These na- Furthermore, Chong et al (82) used TiO and nano - ti-
2
nocomposites were effi cient to adsorb RhB, and for its tanium dioxide in photocatalytic membranes for lar-
re-utilization after regeneration by methanol washing. ge - scale water decontamination. Other NPs such as
These data suggest the application of SPIONS@RGO ZnONPs (83) and AuNPs (84) have been also applied
nanocomposites into pre-concentration of RhB. Herein, to photocatalysis; however, their cost of production still
SPIONS also have been coated with polystyrene (PS) elevates.
to remove oil spills from water (76). In this case, it was
taken advantage of the high hydrophobicity of those
nanocomposites aiming oil adsorption with subsequent 4.3. Nanoparticles and nanocomposites as sensors
removal by aggregation under the action of a magnetic for contaminant monitoring
fi eld. An important step of water and wastewater treatment
consists of pollutant detection. Several techniques (85)
The application of cited nanocomposites depends on and sensors (86,87) have been used with this aim. Ne-
secondary steps for water cleaning, that means, use of vertheless, NPs are changing the way of pollutant de-
centrifugation, aggregation by a magnetic fi eld, or fi l- tection. AuNPs have been extensively used to detect
tration of the mixture (water/nanocomposites) through ions of heavy metals from water and wastewater. In this
water fi ltration membrane. Furthermore, those nano- regard, Ding et al (88) developed a new method for vi-
2+
composites are specifi c for some organic contaminants sual detection of Hg by anti-aggregation of AuNPs.
2+
or unique cations of heavy metals, which also increase That means Hg acts as a competitor to interact with
the cost of water treatment. In this context, Alves et al the aggregating agent (cysteine) of AuNPs. This tech-
(77) developed self-supported nanocomposites made of nique could be useful for qualitative assays for fi eld
2+
cerium hydrogen - phosphate (CeP) and functionalized identifi cation of Hg into water. Similarly, Li et al (89)
CNTs and GO. These nanocomposites were capable to developed a colorimetric technique for Hg detection
2+
remove several cations of heavy metal from water, even from water, using the anti-aggregation of AuNPs by the
2+
when they were into a mixture as well as at different interaction of Hg with O-phenylenediamine (OPD);
pH. The advantage of such nanocomposites includes a a known aggregation agent of AuNPs. Briefl y, citrate-
self-supported character that avoids additional steps for stabilized AuNPs get aggregated in presence of OPD;
2+
water decontamination. Indeed, decontamination oc- however, when the water is contaminated with Hg ,
curs by fi ltering the water or wastewater through the such aggregation doesn’t occur (Figure 2-a) and the co-
lour of the solution turns into pink (Figure 2-b).

48
Rev. Asoc. Col. Cienc.(Col.), 2020; 32: 42-62.