Environmental Engineering Reference
In-Depth Information
The adsorption behavior of Ni(II), Cd(II) and Pb(II) from aqueous
solutions by shells of hazelnut and almond were investigated by Bulut and Tez
[83]. The equilibrium time was found to be 120 min. Results showed that
maximum adsorption capacities of the hazelnut shell and almond shell
decreased from 16.23 to 5.47 and from 5.43 to 3.74 mg g
-1
, respectively, when
temperature increased from 25 to 40 ºC. The thermodynamics results confirm
the spontaneous nature and the endothermic nature of the adsorption process.
Green coconut shell powder was used to remove Cd
2+
from aqueous
solution [84]. The monolayer adsorption capacity was found to be 285.7 mg g
-
1
at 27 ºC. The kinetic data obtained fitted very well a pseudo second order
kinetic model and 5 min contact time was considered enough to achieve
equilibrium conditions.
Coconut copra meal, a waste product of coconut oil production, was
investigated for its potential use as a biosorbent for cadmium ions from
aqueous solution [85]. The composition of dry copra meal was: moisture 8.9%,
protein 26.7%, crude fiber 10.0%, ash 3.9%, lipid 12.1%, and carbohydrate
38.4%. The saturated monolayer biosorption capacity was found to decrease
from 5 to 2 mg g
-1
for an increase in solution temperature from 26 to 60 ºC.
Ofomaja and Ho [86] studied the adsorption of Cd
2+
and they observed that the
Cd
2+
adsorption was dependent on the pH and cadmium concentration of
aqueous solutions. The adsorption process of Cd
2+
onto copra meal followed a
pseudo second order rate expression.
The sorption of cadmium and lead from aqueous solutions by spent grain,
a byproduct of the brewing process, was investigated by Low
et al
. [87].
Treatment with NaOH greatly enhanced metal sorption, whereas HCl treated
spent grain showed lower sorption than the control material (water-washed
spent grain). The equilibrium process was well described by a Langmuir
isotherm model with maximum sorption capacities of 17.3 mg g
-1
of cadmium
on NaOH-treated spent grain. The initial uptake was fast and thermodynamics
equilibrium was established in less than 120 min.
The Cd
2+
and Cu
2+
adsorptions onto soybean waste and wheat bran were
studied by Kawasaki
et al.
[88]. The amounts of Cd
2+
and Cu
2+
adsorbed onto
untreated soybean waste and wheat bran were larger than those adsorbed onto
defatted substrate. This indicates that the adsorption of Cd
2+
and Cu
2+
onto
vegetable biomass may depend on the fat content. They also observed that the
elution percentage of vegetable biomass increased with the concentration of
hydrochloric acid. As the elution is due to protein degradation in the biomass,
they concluded that Cd
2+
and Cu
2+
are adsorbed on vegetable biomass by their
adsorption onto protein.
Search WWH ::
Custom Search