et al. (2015) used nZVIs with the addition of bentonite (nZVI/Al-bent) for the
adsorption of Se(VI) from aqueous solutions. Efficiency of removal of Se(VI) was
reported to be 95.7%. Wang et al. (2009) demonstrated increased dehalogenation of
chlorinated organic compounds under the influence of nZVIs with the addition of
Pd. Su et al. (2012) showed there to be an 86% decrease in the total weight of
chlorinated volatile organic compounds (CVOCs) found in groundwater caused by
nanoparticles of emulsified zerovalent iron (EZVI) over a period of 2.5 years.
Mackenzie et al. (2016) used a composite made up of colloidal active carbon and
embedded nanoiron (carbo-iron) to remove tetrachloroethene (PCE) from polluted
land in Germany. The authors recorded a successful outcome, as the initial concentration of PCE was determined to be 20 mgÁL
À1 , while after 1000 days from the
application of nanoiron, the concentration had decreased to 8–9 mgÁL
À1 .
Poguberovic et al. (2016) successfully used nZVIs synthesized using extracts from
the leaves of oak, mulberry, and cherry to remove As(III), Cr(VI), Ni(II), and Cu
(II) from aqueous solutions. pH was to a large extent decisive in determining the
effectiveness of the process. The “green” synthesis of nZVIs demonstrated by the
authors makes them safer and contributes to sustainable development – the use of
extracts from leaves, which are considered to be waste, makes it an inexpensive
adsorbent of toxic metals. Such results are very promising, but further studies are
necessary in order for this technology to be deployed in sewage treatment.
Titanium compounds, which are used in photocatalytic processes, also have some
very interesting properties from the point of view of applications in protection of the
environment. Photocatalysis is an effective and advanced technology for the removal
of organic pollutants from water and air (Nakata and Fujishima 2012). TiO 2 NPs are
the most frequently studied photocatalysts due to the strong oxidation capacity,
superhydrophilicity, chemical stability, long-term stability, nontoxicity, and low
cost (Fujishima and Zhang, 2006). Rasalingam et al. (2014) demonstrated the high
activity TiO 2 -SiO 2 mixed oxide nanomaterials in degrading a chemical organic
compound – the dye methylene blue. This composite may have a potential application in industrial sewage treatment systems. The photodecomposition of harmful
perfluorooctanoic acid (PFOAs) from sewers also proved to be efficient, thanks to
the application of photocatalysts based on TiO 2 NPs, Ga 2 O 3 NPs, and In 2 O 3 NPs
under the conditions of UV radiation (da Silva et al. 2017). Compared to other
nano-photocatalysts, In 2 O 3 NPs showed the best potential for degrading PFOA while
using less energy over the same period of time (Gao and Chorover 2012,
Chularueangaksorn et al. 2014). TiO 2 NPs are also capable of producing reactive
oxidants, i.e., hydroxyl radicals, which can act as a disinfectant against various
pathogens (Zan et al. 2007).
In addition to metals, silica materials, carbon nanotubes, graphene, lime powder,
hydroxyapatite, and polymers can also be deployed to good effect in the process of
environmental remediation. Nano-silica have been used effectively for the removal
of aldehydes, ketones, heavy metals, CO 2 , H 2 S, and cationic dyes (Guerra et al.
2018). Nanocomposites of attapulgite proved to be repairing agent used in mining
areas and on agricultural land polluted with heavy metals (Medina-Pérez et al. 2019).
Carbon-based nanomaterials have been shown to be capable of adsorbing and highly
14
A. Gorczyca et al.
adsorption of Se(VI) from aqueous solutions. Efficiency of removal of Se(VI) was
reported to be 95.7%. Wang et al. (2009) demonstrated increased dehalogenation of
chlorinated organic compounds under the influence of nZVIs with the addition of
Pd. Su et al. (2012) showed there to be an 86% decrease in the total weight of
chlorinated volatile organic compounds (CVOCs) found in groundwater caused by
nanoparticles of emulsified zerovalent iron (EZVI) over a period of 2.5 years.
Mackenzie et al. (2016) used a composite made up of colloidal active carbon and
embedded nanoiron (carbo-iron) to remove tetrachloroethene (PCE) from polluted
land in Germany. The authors recorded a successful outcome, as the initial concentration of PCE was determined to be 20 mgÁL
À1 , while after 1000 days from the
application of nanoiron, the concentration had decreased to 8–9 mgÁL
À1 .
Poguberovic et al. (2016) successfully used nZVIs synthesized using extracts from
the leaves of oak, mulberry, and cherry to remove As(III), Cr(VI), Ni(II), and Cu
(II) from aqueous solutions. pH was to a large extent decisive in determining the
effectiveness of the process. The “green” synthesis of nZVIs demonstrated by the
authors makes them safer and contributes to sustainable development – the use of
extracts from leaves, which are considered to be waste, makes it an inexpensive
adsorbent of toxic metals. Such results are very promising, but further studies are
necessary in order for this technology to be deployed in sewage treatment.
Titanium compounds, which are used in photocatalytic processes, also have some
very interesting properties from the point of view of applications in protection of the
environment. Photocatalysis is an effective and advanced technology for the removal
of organic pollutants from water and air (Nakata and Fujishima 2012). TiO 2 NPs are
the most frequently studied photocatalysts due to the strong oxidation capacity,
superhydrophilicity, chemical stability, long-term stability, nontoxicity, and low
cost (Fujishima and Zhang, 2006). Rasalingam et al. (2014) demonstrated the high
activity TiO 2 -SiO 2 mixed oxide nanomaterials in degrading a chemical organic
compound – the dye methylene blue. This composite may have a potential application in industrial sewage treatment systems. The photodecomposition of harmful
perfluorooctanoic acid (PFOAs) from sewers also proved to be efficient, thanks to
the application of photocatalysts based on TiO 2 NPs, Ga 2 O 3 NPs, and In 2 O 3 NPs
under the conditions of UV radiation (da Silva et al. 2017). Compared to other
nano-photocatalysts, In 2 O 3 NPs showed the best potential for degrading PFOA while
using less energy over the same period of time (Gao and Chorover 2012,
Chularueangaksorn et al. 2014). TiO 2 NPs are also capable of producing reactive
oxidants, i.e., hydroxyl radicals, which can act as a disinfectant against various
pathogens (Zan et al. 2007).
In addition to metals, silica materials, carbon nanotubes, graphene, lime powder,
hydroxyapatite, and polymers can also be deployed to good effect in the process of
environmental remediation. Nano-silica have been used effectively for the removal
of aldehydes, ketones, heavy metals, CO 2 , H 2 S, and cationic dyes (Guerra et al.
2018). Nanocomposites of attapulgite proved to be repairing agent used in mining
areas and on agricultural land polluted with heavy metals (Medina-Pérez et al. 2019).
Carbon-based nanomaterials have been shown to be capable of adsorbing and highly
14
A. Gorczyca et al.