272
9.3.7 Adsorption Studies
The effects of amount of adsorbent, initial metal ion concentration, and the time of
adsorption were investigated. The percentage of removal of Cr(VI) ions is determined using Equation 9.1.
%R
J J
J
0
0
100
e
(9.1)
where γ 0 is the initial concentration of Cr(VI) ions in solution [mg/l] and γ e is equilibrium concentration [mg/l].
The adsorption capacity at time t, q t [mg/g], is determined using the Equation 9.2.
q
V
m
t
t
J J
0
(9.2)
where γ t [mg/l] is the concentration of the metal at time t, V is the volume of the
solution [l], and m is adsorbent mass [g].
9.3.7.1 Amount of Adsorbent
Examining the impact of the amount of adsorbent on the process of adsorption is a
very important parameter that determines the potential of the adsorbent for removal
of metal ions in particular initial concentrations. The influence of the amount of
clayey diatomite (0.5, 1.5, 2.5, 3.5, 4.5, and 5.5 g/l) in the degree of removal of
Cr(VI) ions was studied for the constant initial metal concentration of 0.5 mg/l, at
room temperature, pH 3, at 400 rpm. Results show that by increasing the amount of
adsorbent, the percentage of removal of Cr(VI) increases as well. Increasing the
amount of adsorbent provides greater contact area and the availability of multiple
active zones, leading to improve adsorption of test ions (Chatterjee et al. 2010). In
adsorbent amount of more than 2.5 g/l, the removal of Cr(VI) is reduced due to the
agglomeration of particles of clayey diatomite and thus resulting in the decrease of
active surface of the diatomite (Fig. 9.7).
9.3.7.2 Initial Metal Ion Concentration
The experiments for investigation of the influence of the initial metal ions concentration on the percentage of removal were performed with a constant amount of
clayey diatomite of 2.5 g/l at pH of the solution 3, at constant room temperature, and
different initial Cr(VI) ion concentrations of 0.3, 0.4, 0.5, and 0.6 mg/l. The impact
of the initial concentration in the percentage of removal of diatomite is shown in
Fig. 9.8. The figure shows that the rate of removal increases by decreasing of the
initial concentration of Cr(VI) ions. The lowest initial concentration of 0.3 mg/l has
H. Memedi et al.
9.3.7 Adsorption Studies
The effects of amount of adsorbent, initial metal ion concentration, and the time of
adsorption were investigated. The percentage of removal of Cr(VI) ions is determined using Equation 9.1.
%R
J J
J
0
0
100
e
(9.1)
where γ 0 is the initial concentration of Cr(VI) ions in solution [mg/l] and γ e is equilibrium concentration [mg/l].
The adsorption capacity at time t, q t [mg/g], is determined using the Equation 9.2.
q
V
m
t
t
J J
0
(9.2)
where γ t [mg/l] is the concentration of the metal at time t, V is the volume of the
solution [l], and m is adsorbent mass [g].
9.3.7.1 Amount of Adsorbent
Examining the impact of the amount of adsorbent on the process of adsorption is a
very important parameter that determines the potential of the adsorbent for removal
of metal ions in particular initial concentrations. The influence of the amount of
clayey diatomite (0.5, 1.5, 2.5, 3.5, 4.5, and 5.5 g/l) in the degree of removal of
Cr(VI) ions was studied for the constant initial metal concentration of 0.5 mg/l, at
room temperature, pH 3, at 400 rpm. Results show that by increasing the amount of
adsorbent, the percentage of removal of Cr(VI) increases as well. Increasing the
amount of adsorbent provides greater contact area and the availability of multiple
active zones, leading to improve adsorption of test ions (Chatterjee et al. 2010). In
adsorbent amount of more than 2.5 g/l, the removal of Cr(VI) is reduced due to the
agglomeration of particles of clayey diatomite and thus resulting in the decrease of
active surface of the diatomite (Fig. 9.7).
9.3.7.2 Initial Metal Ion Concentration
The experiments for investigation of the influence of the initial metal ions concentration on the percentage of removal were performed with a constant amount of
clayey diatomite of 2.5 g/l at pH of the solution 3, at constant room temperature, and
different initial Cr(VI) ion concentrations of 0.3, 0.4, 0.5, and 0.6 mg/l. The impact
of the initial concentration in the percentage of removal of diatomite is shown in
Fig. 9.8. The figure shows that the rate of removal increases by decreasing of the
initial concentration of Cr(VI) ions. The lowest initial concentration of 0.3 mg/l has
H. Memedi et al.