102
Recently, clay–biochar composites became popular for various purposes. Biochar
is obtained by pyrolysis of animal or plant residues. Biochar is a carbon and functional groups rich porous solid and is an environmentally friendly sorbent. Thus, it
is an excellent adsorbent for different types of pollutants (Han et al. 2019).
Montmorillonite–biochar composites were used by many researchers for organic
dye, pharmaceuticals, or anion removals (Yao et al. 2014; Chen et al. 2017; Pereira
et al. 2013). But, heavy metal adsorption onto montmorillonite–biochar composites
has not been encountered yet.
Apart from all these composites, there are many types of montmorillonite composites used for the purpose of heavy metal removal. The graphene oxide, which is
a single monomolecular layer graphite, has both hydrophilic and hydrophobic characteristics, enabling graphene oxide to adsorb heavy metals. Zhang et al. fabricated
montmorillonite–graphene oxide in the presence of stearyltrimethylammonium
chloride as cross-linking agent. The composite suspension had positive zeta potential. The kinetics of Pb(II) adsorption on fabricated composite fitted pseudo-secondorder model. The adsorption character showed metal-like adsorption. Although the
author expressed that the presence of stearyltrimethylammonium chloride did not
reduce the adsorption capacity, and hydrophilic functional groups of graphene oxide
gave more active sites, Pb(II) adsorption capacity on fabricated composite was
lower than given Pb(II) adsorption capacity in literature (Zhang et al. 2019).
Table 4.1 shows the data about adsorption properties of various heavy metals on
various types of montmorillonite composites. As seen from the table, however, the
heavy metal adsorption onto different kinds of montmorillonite composite has been
widely explored for approximately 10 years. More exploration should be performed
to serve industrial purposes.
4.6 Conclusion
As seen from so far examined studies, various composites of montmorillonite have
high affinity to heavy metal ions and have been widely used for heavy metal removal.
In general, composites show higher adsorption capacity for particular heavy metal
than parent sorbents/components of composite. Many montmorillonite composites
including organic functional groups or natural components such as humic acid, alginate, or bacteria may simulate environmental conditions. Determining heavy metal
adsorption parameters is decisive for the fortune of heavy metal in environment.
Biochar composite of montmorillonite as an adsorbent for heavy metals needs more
studies to achieve better understanding and to find convenient usage area. On the
other hand, efficient, reusable, and low-cost montmorillonite composites should be
used in industrial application.
J. Hızal and M. Yılmazoğlu
Recently, clay–biochar composites became popular for various purposes. Biochar
is obtained by pyrolysis of animal or plant residues. Biochar is a carbon and functional groups rich porous solid and is an environmentally friendly sorbent. Thus, it
is an excellent adsorbent for different types of pollutants (Han et al. 2019).
Montmorillonite–biochar composites were used by many researchers for organic
dye, pharmaceuticals, or anion removals (Yao et al. 2014; Chen et al. 2017; Pereira
et al. 2013). But, heavy metal adsorption onto montmorillonite–biochar composites
has not been encountered yet.
Apart from all these composites, there are many types of montmorillonite composites used for the purpose of heavy metal removal. The graphene oxide, which is
a single monomolecular layer graphite, has both hydrophilic and hydrophobic characteristics, enabling graphene oxide to adsorb heavy metals. Zhang et al. fabricated
montmorillonite–graphene oxide in the presence of stearyltrimethylammonium
chloride as cross-linking agent. The composite suspension had positive zeta potential. The kinetics of Pb(II) adsorption on fabricated composite fitted pseudo-secondorder model. The adsorption character showed metal-like adsorption. Although the
author expressed that the presence of stearyltrimethylammonium chloride did not
reduce the adsorption capacity, and hydrophilic functional groups of graphene oxide
gave more active sites, Pb(II) adsorption capacity on fabricated composite was
lower than given Pb(II) adsorption capacity in literature (Zhang et al. 2019).
Table 4.1 shows the data about adsorption properties of various heavy metals on
various types of montmorillonite composites. As seen from the table, however, the
heavy metal adsorption onto different kinds of montmorillonite composite has been
widely explored for approximately 10 years. More exploration should be performed
to serve industrial purposes.
4.6 Conclusion
As seen from so far examined studies, various composites of montmorillonite have
high affinity to heavy metal ions and have been widely used for heavy metal removal.
In general, composites show higher adsorption capacity for particular heavy metal
than parent sorbents/components of composite. Many montmorillonite composites
including organic functional groups or natural components such as humic acid, alginate, or bacteria may simulate environmental conditions. Determining heavy metal
adsorption parameters is decisive for the fortune of heavy metal in environment.
Biochar composite of montmorillonite as an adsorbent for heavy metals needs more
studies to achieve better understanding and to find convenient usage area. On the
other hand, efficient, reusable, and low-cost montmorillonite composites should be
used in industrial application.
J. Hızal and M. Yılmazoğlu