maximum adsorption capacities. Compared to low-cost or residual materials,
nanomaterials present several advantages including faster and more efficient
removal of metals and organic CECs under a large range of pH and temperature,
a higher surface area-to-volume ratio, and a lower dose requirement. Recent
advances reported the potential use of biochar modified by KOH or H 2 SO 4 to
remove tetracycline from water with adsorption capacities of 23 and 59 mg/g for
acidic and basic treatments of biochar (Liu et al. 2012). Jing et al. (2014) showed
that the removal of tetracycline was improved by 46% in the presence of MeOHmodified biochar compared to the unmodified adsorbent.
Sulfate, as a major constituent of mine effluents acts as a competitor for Se
oxyanions leading to the rapid exhaustion of the ion exchange capacity of
materials, but Fe(III)-loaded sorbent, such as biochar, improves the sorption
capacity (Holmes and Gu 2016). Sulfate pre-treatment (e.g., precipitation as
gypsum) is necessary to minimize this limitation. Other factors to be considered
are TSS-induced plugging, organic fouling, and strong oxidants (Microbial
Technologies, Inc. 2006). Recent findings [synthetic effluents; pH 6, 1 mg/L As
(V) and 1 mg/L Sb(III)] showed that Fe-loaded biochar (by evaporation) tripled
and quintupled the raw biochar sorption capacity for As(V) and Sb(III), respectively (Calugaru et al. 2019). Other studies confirmed that Fe(III) impregnation of
biochar enhanced its As(V) removal capacity by more than 250 times (Calugaru
et al. 2018). Other approaches include the use of granular activated carbon
supported nanoscale zero-valent iron (Chowdhury and Mulligan 2013) and
other nanomaterials (such as Fe-Cu) (Babaee et al. 2018).
4. AOPs operate at near-ambient temperature and pressure, and involve the generation of powerful oxidants, which are able to break –C¼C– double bonds and
aromatic rings for effective treatment of organic contaminants in water (Bokare
and Choi 2014; Gogate and Pandit 2004). There is a growing interest in developing AOPs to remove CECs from wastewater because of their capabilities to
degrade organic contaminants and/or oxidize metals/metalloids. Common AOPs
include the use of ozone (O 3 ), hydrogen peroxide (H 2 O 2 ), and UV, or their
combination. AOPs are applied whenever conventional oxidation is insufficient,
kinetics are slow, and the contaminants are refractory or partially oxidized,
yielding stable by-products with greater toxicity than the original species.
AOPs have been used to enhance the degradation of pharmaceuticals and pesticides (Ikehata et al. 2006). For example, electro-Fenton and photo-Fenton
processes, which are based on the generation of hydroxyl radicals through
electrochemical reactions or UV irradiation, have been successfully applied for
the degradation of chlorophenols and pesticides (Adeleye et al. 2016; Brillas et al.
1995; Gözmen et al. 2003; Oturan et al. 2001). The use of ozonation alone or in
combination with H 2 O 2 or UV is of high interest because of the potential to
degrade CECs from municipal and industrial wastewater. As discussed by
Rodriguez-Narvaez et al. (2017), these processes have been applied to the
degradation of several CECs with satisfying efficiencies (> 80%). The degradation of CECs occurred through the direct oxidation of ozone or its decomposition
596
C. M. Neculita et al.
nanomaterials present several advantages including faster and more efficient
removal of metals and organic CECs under a large range of pH and temperature,
a higher surface area-to-volume ratio, and a lower dose requirement. Recent
advances reported the potential use of biochar modified by KOH or H 2 SO 4 to
remove tetracycline from water with adsorption capacities of 23 and 59 mg/g for
acidic and basic treatments of biochar (Liu et al. 2012). Jing et al. (2014) showed
that the removal of tetracycline was improved by 46% in the presence of MeOHmodified biochar compared to the unmodified adsorbent.
Sulfate, as a major constituent of mine effluents acts as a competitor for Se
oxyanions leading to the rapid exhaustion of the ion exchange capacity of
materials, but Fe(III)-loaded sorbent, such as biochar, improves the sorption
capacity (Holmes and Gu 2016). Sulfate pre-treatment (e.g., precipitation as
gypsum) is necessary to minimize this limitation. Other factors to be considered
are TSS-induced plugging, organic fouling, and strong oxidants (Microbial
Technologies, Inc. 2006). Recent findings [synthetic effluents; pH 6, 1 mg/L As
(V) and 1 mg/L Sb(III)] showed that Fe-loaded biochar (by evaporation) tripled
and quintupled the raw biochar sorption capacity for As(V) and Sb(III), respectively (Calugaru et al. 2019). Other studies confirmed that Fe(III) impregnation of
biochar enhanced its As(V) removal capacity by more than 250 times (Calugaru
et al. 2018). Other approaches include the use of granular activated carbon
supported nanoscale zero-valent iron (Chowdhury and Mulligan 2013) and
other nanomaterials (such as Fe-Cu) (Babaee et al. 2018).
4. AOPs operate at near-ambient temperature and pressure, and involve the generation of powerful oxidants, which are able to break –C¼C– double bonds and
aromatic rings for effective treatment of organic contaminants in water (Bokare
and Choi 2014; Gogate and Pandit 2004). There is a growing interest in developing AOPs to remove CECs from wastewater because of their capabilities to
degrade organic contaminants and/or oxidize metals/metalloids. Common AOPs
include the use of ozone (O 3 ), hydrogen peroxide (H 2 O 2 ), and UV, or their
combination. AOPs are applied whenever conventional oxidation is insufficient,
kinetics are slow, and the contaminants are refractory or partially oxidized,
yielding stable by-products with greater toxicity than the original species.
AOPs have been used to enhance the degradation of pharmaceuticals and pesticides (Ikehata et al. 2006). For example, electro-Fenton and photo-Fenton
processes, which are based on the generation of hydroxyl radicals through
electrochemical reactions or UV irradiation, have been successfully applied for
the degradation of chlorophenols and pesticides (Adeleye et al. 2016; Brillas et al.
1995; Gözmen et al. 2003; Oturan et al. 2001). The use of ozonation alone or in
combination with H 2 O 2 or UV is of high interest because of the potential to
degrade CECs from municipal and industrial wastewater. As discussed by
Rodriguez-Narvaez et al. (2017), these processes have been applied to the
degradation of several CECs with satisfying efficiencies (> 80%). The degradation of CECs occurred through the direct oxidation of ozone or its decomposition
596
C. M. Neculita et al.