10
by adding the appropriate dose of oxidizing agent and at the desired experimental
conditions like reaction time and temperature (Yang et al. 2019). Many reports on
the oxidation of activated carbon with H 2 O 2 concluded that minimal textural modifications are impacted at the carbon surface, although both increase and decrease in
surface area were reported (Rivera-Utrilla et al. 2011).
1.4.2 Surface Modification by Sulfuration
Functional groups with sulfur attachment such as C–S, S=O, and C=S are introduced to carbon sorbent surfaces through sulfuration treatment. This can be achieved
through reaction of carbon with sulfur or sulfur-containing compounds such as H 2 S,
SO 2 , K 2 S, and N 2 S (Yang et al. 2019). Depending on the treatment conditions, this
technique also alters the porous structure of the carbon sorbent either with increasing or declining specific surface area or volume of the pores. Carbon-sulfur complexes show similarities in terms of non-stoichiometry character and physicochemical
performance. These complexes can neither be completely extracted with solvent nor
heat treatment decomposition under vacuum, but they can rather be eliminated as
hydrogen sulfide by heat treatment in hydrogen at temperature range of 973–1046 K
(Rivera-Utrilla et al. 2011). Activated carbon modified with sulfur-containing
groups has proven to be effective in adsorbing many metal species such as Cd(II),
Cu(II), Cr(VI), HgCl 2 , Hg(II), Pb(II), and Zn(II) in solutions (Rivera-Utrilla
et al. 2011).
1.4.3 Surface Modification by Nitrogenation
The introduction of nitrogen-containing functional groups such as –NH, –NH 2 ,
–C–N, and –C ≡ N onto the surface of carbon sorbent matters is done by nitrogenation, and this is usually achieved through reactions with ammonia (NH 3 ), urea
(CH 4 N 2 O), and amines (RNH 2 ) (Li et al. 2017). The incorporation of nitrogen-based
functional groups on carbon sorbent surface increases its basic properties and hence
enhances its metal adsorption capacity (Yang et al. 2019). The presence of these
functional groups on carbon surface has been reported to have insignificant effect on
porosity of the carbon material (Kasnejad et al. 2012). Activated carbon modified
with nitrogenated agents has shown to have higher adsorption capacity for Pb(II)
and Cu(II) compared to commercial activated carbon (Budaeva and Zoltoev 2010).
Ammonia has been widely chosen as the nitrogenated agent for activated carbon
surface modification, and it has been effectively tested in various applications ranging from toxic heavy metals, anions, and organic compound contaminants (RiveraUtrilla et al. 2011).
B. Oladipo et al.
by adding the appropriate dose of oxidizing agent and at the desired experimental
conditions like reaction time and temperature (Yang et al. 2019). Many reports on
the oxidation of activated carbon with H 2 O 2 concluded that minimal textural modifications are impacted at the carbon surface, although both increase and decrease in
surface area were reported (Rivera-Utrilla et al. 2011).
1.4.2 Surface Modification by Sulfuration
Functional groups with sulfur attachment such as C–S, S=O, and C=S are introduced to carbon sorbent surfaces through sulfuration treatment. This can be achieved
through reaction of carbon with sulfur or sulfur-containing compounds such as H 2 S,
SO 2 , K 2 S, and N 2 S (Yang et al. 2019). Depending on the treatment conditions, this
technique also alters the porous structure of the carbon sorbent either with increasing or declining specific surface area or volume of the pores. Carbon-sulfur complexes show similarities in terms of non-stoichiometry character and physicochemical
performance. These complexes can neither be completely extracted with solvent nor
heat treatment decomposition under vacuum, but they can rather be eliminated as
hydrogen sulfide by heat treatment in hydrogen at temperature range of 973–1046 K
(Rivera-Utrilla et al. 2011). Activated carbon modified with sulfur-containing
groups has proven to be effective in adsorbing many metal species such as Cd(II),
Cu(II), Cr(VI), HgCl 2 , Hg(II), Pb(II), and Zn(II) in solutions (Rivera-Utrilla
et al. 2011).
1.4.3 Surface Modification by Nitrogenation
The introduction of nitrogen-containing functional groups such as –NH, –NH 2 ,
–C–N, and –C ≡ N onto the surface of carbon sorbent matters is done by nitrogenation, and this is usually achieved through reactions with ammonia (NH 3 ), urea
(CH 4 N 2 O), and amines (RNH 2 ) (Li et al. 2017). The incorporation of nitrogen-based
functional groups on carbon sorbent surface increases its basic properties and hence
enhances its metal adsorption capacity (Yang et al. 2019). The presence of these
functional groups on carbon surface has been reported to have insignificant effect on
porosity of the carbon material (Kasnejad et al. 2012). Activated carbon modified
with nitrogenated agents has shown to have higher adsorption capacity for Pb(II)
and Cu(II) compared to commercial activated carbon (Budaeva and Zoltoev 2010).
Ammonia has been widely chosen as the nitrogenated agent for activated carbon
surface modification, and it has been effectively tested in various applications ranging from toxic heavy metals, anions, and organic compound contaminants (RiveraUtrilla et al. 2011).
B. Oladipo et al.