25.32 mg/g for Mn. In another study, Zareei and Hosseini (2019) reported an
increased performance of polyethersulfone-based nanofiltration membranes that
were prepared by composite CoFe 2 O 4 /CuO nanoparticles for Ni, Pb, and Cu
removal.
11.4.2 Nanotechnology
Nanoparticles (NPs), nanomaterials (NMs), or nano-adsorbents (NAs) including
nanofilms, nanowires, quantum dots, nanotubes, and various colloids are now
gaining popularity in in situ and ex situ HM water treatment. HMs can be removed
by adopting nanotechnologies where nanoscale biosensors detect the HMs in surface
and groundwater and accelerate the efficiency of the chemical and photocatalytic
processes. NMs such as nanomembranes, nanocatalysts, nanoscale metal oxides,
graphenes, carbon nanotubes, nanobiological processes and iron oxides (FeO,
Fe 2 O 3, and Fe 3 O 4 ), aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), and silicon
dioxide (SiO 2 ) are used to remediate the HMs from contaminated water systems.
Several NAs such as clay materials, activated carbon, metal oxides, nano-titanates,
silica, magnetic iron oxide nanoparticles (MNPs), and alginate biopolymer have also
been employed to eliminate the HMs toxicity (Kumar et al. 2019).
Nanomaterial-induced phytoremediation techniques have also been studied to
decontaminate the water systems where co-uptake of the NMs and the HMs occur
by the particular plants and NMs enhance the accumulation capability of the plants
by enhancing the cell wall permeability, regulating the transporter gene expression,
and co-transportation. For example, graphene oxide NM can enhance the As uptake
capability of Triticum aestivum (Hu et al. 2014), and TiO 2 NPs can improve the Cd
uptake capability of Glycine max (Singh and Lee 2016). A recent experiment by
Arshad et al. (2019) reported that 1 gram of polyethylenimine-modified graphene
oxide hydrogel composite (functionalized GOCA) can remove up to 602 mg of Pb,
374 mg of Hg, and 181 mg of Cd from wastewater at 25
C. Li et al. (2015) reported
maximum adsorption capacity of chitosan/sulfhydryl-functionalized graphene oxide
composites for Pb, Cd, Cu, and Mn as 568.18 mg/g, 253.81 mg/g, 68.68 mg/g, and
18.29 mg/g. Amino siloxane oligomer-modified graphene oxide composite also
exhibited the maximum adsorption capacity of 310.63 mg/g for U and 243.90 mg/
g for Eu in aqueous solution (Zhao et al. 2017). In another study Najafi et al. (2012)
reported the maximum adsorption capacity of amino-functionalized silica
nanohollow sphere (NH 2 -SNHS) as 96.79 mg/g for Pb, 40.73 mg/g for Cd, and
31.29 mg/g for Ni.
268
I. Mukherjee et al.
increased performance of polyethersulfone-based nanofiltration membranes that
were prepared by composite CoFe 2 O 4 /CuO nanoparticles for Ni, Pb, and Cu
removal.
11.4.2 Nanotechnology
Nanoparticles (NPs), nanomaterials (NMs), or nano-adsorbents (NAs) including
nanofilms, nanowires, quantum dots, nanotubes, and various colloids are now
gaining popularity in in situ and ex situ HM water treatment. HMs can be removed
by adopting nanotechnologies where nanoscale biosensors detect the HMs in surface
and groundwater and accelerate the efficiency of the chemical and photocatalytic
processes. NMs such as nanomembranes, nanocatalysts, nanoscale metal oxides,
graphenes, carbon nanotubes, nanobiological processes and iron oxides (FeO,
Fe 2 O 3, and Fe 3 O 4 ), aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), and silicon
dioxide (SiO 2 ) are used to remediate the HMs from contaminated water systems.
Several NAs such as clay materials, activated carbon, metal oxides, nano-titanates,
silica, magnetic iron oxide nanoparticles (MNPs), and alginate biopolymer have also
been employed to eliminate the HMs toxicity (Kumar et al. 2019).
Nanomaterial-induced phytoremediation techniques have also been studied to
decontaminate the water systems where co-uptake of the NMs and the HMs occur
by the particular plants and NMs enhance the accumulation capability of the plants
by enhancing the cell wall permeability, regulating the transporter gene expression,
and co-transportation. For example, graphene oxide NM can enhance the As uptake
capability of Triticum aestivum (Hu et al. 2014), and TiO 2 NPs can improve the Cd
uptake capability of Glycine max (Singh and Lee 2016). A recent experiment by
Arshad et al. (2019) reported that 1 gram of polyethylenimine-modified graphene
oxide hydrogel composite (functionalized GOCA) can remove up to 602 mg of Pb,
374 mg of Hg, and 181 mg of Cd from wastewater at 25
C. Li et al. (2015) reported
maximum adsorption capacity of chitosan/sulfhydryl-functionalized graphene oxide
composites for Pb, Cd, Cu, and Mn as 568.18 mg/g, 253.81 mg/g, 68.68 mg/g, and
18.29 mg/g. Amino siloxane oligomer-modified graphene oxide composite also
exhibited the maximum adsorption capacity of 310.63 mg/g for U and 243.90 mg/
g for Eu in aqueous solution (Zhao et al. 2017). In another study Najafi et al. (2012)
reported the maximum adsorption capacity of amino-functionalized silica
nanohollow sphere (NH 2 -SNHS) as 96.79 mg/g for Pb, 40.73 mg/g for Cd, and
31.29 mg/g for Ni.
268
I. Mukherjee et al.