343
In a study of the Langmuir isotherm for banana peels on the biosorption of Cd
2+
and Pb
2+
, a maximum capacity of 2.18 mg g
−1
for Pb
2+
and 5.71 mg g
−1
for Cd
2+
was
obtained. The R
2
was also reported to be approaching 1 suggesting that the Langmuir
isotherm can best explain the biosorption of Cd
2+
and Pb
2+
on banana peel (Anwar
et al. 2010). In comparison, a study for biosorption of Cd
2+
and Pb
2+
using mango
peel waste showed an adsorption capacity of 68.92 and 99.05 mg/g. The maximum
adsorption capacity Q max and concentration of metal ions at equilibrium C eq were fit
into a Langmuir isotherm model.
The correlation coefficient of for both Cd
2+
and Pb
2+
was found to be close to 1
confirming that the Langmuir isotherm is the best fit model for the mango peel
waste adsorption of the metals (Iqbal et al. 2009b). The R
2
obtained for the Langmuir
adsorption models of banana, kiwi, and tangerine waste fruit cortexes all showed
close to 1 for Cd
2+
, Cr
3+
, and Zn
2+
, confirming the favorable uptake of the heavy
metals by waste fruit cortexes (Al-Qahtani 2016). Although some studies were done
to fit the adsorption of the waste fruit cortexes into a Freundlich isotherm (Iqbal
et al. 2009b), the best fit has always been reported for Langmuir isotherm.
13.7 Conclusions
As a conclusion, this chapter reviewed extensively on the usage of waste fruit cortexes in the removal of heavy metals from water. In a rapidly developing world,
heavy metal contamination from the industries seems rather inevitable. The cost of
removal or treating wastewater is high using common conventional methods; hence,
small holders are taking the easy way out to release the untreated water into the
environment. Heavy metals in water have been found to cause various health issues
to humans such as skin and kidney damages, potentially carcinogenic, damage to
the liver, and gastrointestinal issues.
In view of the detrimental effects of heavy metal contaminants and the high cost
of conventional wastewater treatment methods, researchers embarked on investigating the usage of waste fruit cortexes for the removal of heavy metals from water.
The removal is achieved due to the presence of the hydroxyl and carboxyl groups in
the cellulose and pectin in the cortexes of the fruits. The functional groups take part
in the complexation and ion-exchange mechanism to remove the heavy metals from
water. Many different waste fruit cortexes were reviewed in this chapter. Over all,
citrus fruits were found to have the highest maximum adsorption for the
selected metals.
Various factors were investigated for the biosorption of heavy metals. A pH of
5–6.5 was found to be the most optimum for biosorption while an initial metal concentration should be low. A higher pH value will cause the release of H ions from
the functional groups on the biosorbents, hence making way for the uptake of the
metallic cations in the medium. Low initial metal concentration ensures that the
active sites are not saturated for the uptake of the metal ions from the medium. A
more robust surface mass transfer was achieved which resulted in more rapid
13 Waste Fruit Cortexes for the Removal of Heavy Metals from Water
In a study of the Langmuir isotherm for banana peels on the biosorption of Cd
2+
and Pb
2+
, a maximum capacity of 2.18 mg g
−1
for Pb
2+
and 5.71 mg g
−1
for Cd
2+
was
obtained. The R
2
was also reported to be approaching 1 suggesting that the Langmuir
isotherm can best explain the biosorption of Cd
2+
and Pb
2+
on banana peel (Anwar
et al. 2010). In comparison, a study for biosorption of Cd
2+
and Pb
2+
using mango
peel waste showed an adsorption capacity of 68.92 and 99.05 mg/g. The maximum
adsorption capacity Q max and concentration of metal ions at equilibrium C eq were fit
into a Langmuir isotherm model.
The correlation coefficient of for both Cd
2+
and Pb
2+
was found to be close to 1
confirming that the Langmuir isotherm is the best fit model for the mango peel
waste adsorption of the metals (Iqbal et al. 2009b). The R
2
obtained for the Langmuir
adsorption models of banana, kiwi, and tangerine waste fruit cortexes all showed
close to 1 for Cd
2+
, Cr
3+
, and Zn
2+
, confirming the favorable uptake of the heavy
metals by waste fruit cortexes (Al-Qahtani 2016). Although some studies were done
to fit the adsorption of the waste fruit cortexes into a Freundlich isotherm (Iqbal
et al. 2009b), the best fit has always been reported for Langmuir isotherm.
13.7 Conclusions
As a conclusion, this chapter reviewed extensively on the usage of waste fruit cortexes in the removal of heavy metals from water. In a rapidly developing world,
heavy metal contamination from the industries seems rather inevitable. The cost of
removal or treating wastewater is high using common conventional methods; hence,
small holders are taking the easy way out to release the untreated water into the
environment. Heavy metals in water have been found to cause various health issues
to humans such as skin and kidney damages, potentially carcinogenic, damage to
the liver, and gastrointestinal issues.
In view of the detrimental effects of heavy metal contaminants and the high cost
of conventional wastewater treatment methods, researchers embarked on investigating the usage of waste fruit cortexes for the removal of heavy metals from water.
The removal is achieved due to the presence of the hydroxyl and carboxyl groups in
the cellulose and pectin in the cortexes of the fruits. The functional groups take part
in the complexation and ion-exchange mechanism to remove the heavy metals from
water. Many different waste fruit cortexes were reviewed in this chapter. Over all,
citrus fruits were found to have the highest maximum adsorption for the
selected metals.
Various factors were investigated for the biosorption of heavy metals. A pH of
5–6.5 was found to be the most optimum for biosorption while an initial metal concentration should be low. A higher pH value will cause the release of H ions from
the functional groups on the biosorbents, hence making way for the uptake of the
metallic cations in the medium. Low initial metal concentration ensures that the
active sites are not saturated for the uptake of the metal ions from the medium. A
more robust surface mass transfer was achieved which resulted in more rapid
13 Waste Fruit Cortexes for the Removal of Heavy Metals from Water