756 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
The column bed height was varied at 1 m and 0.5 m.
For the varying flow rate systems, 1000 mL/min and 200
mL/min were investigated. Finally, the initial concentration
of As(V) was varied according to the DENR maximum
allowable concentration of 0.08 mg/L, and 1 mg/L.
The breakthrough curve of of Ct/Co vs. t for each com-
bination of parameters was generated based on the column
outflow concentration values computed by COMSOL.
Here, Ct is the As(V) concentration at the effluent, and Co
is the initial As(V) concentration introduced to the column.
Metal Removal
The formula to compute for the concentration of the total
effluent is defined in Equation 1. This value was compared
to the DENR limit for arsenic.
Ceffluent t
C dt
total
t
t
t 0
total
==
8
(1)
Ceffluent (mg/L) is the concentration of the total treated efflu-
ent, Ct (mg/L) is the concentration of the heavy metal spe-
cies at the effluent at time t, ttotal (mins) is the time when Ct
is equal to the influent concentration Co. The performance
of the column can also be described by the metal removal
percentage from the treated wastewater. The percent metal
removal is computed using Equation 2.
C
C C
100% %Removal
o
o effluent #=
-
(2)
RESULTS AND DISCUSSION
Modifying the column bed height, flow rate, and initial
species concentration significantly influences the overall
adsorption behavior of the column. A key response that can
be measured is the saturation time. The saturation time is
defined as the time in which the fixed-bed column is satu-
rated with adsorbate and thus can no longer adsorb more
adsorbate from the wastewater, resulting in an equal adsor-
bate concentration at the outlet and in the feed wastewa-
ter. This occurs at the saturation point. At this point, the
column has been fully utilized with respect to the adsorp-
tion of a particular adsorbate.
Knowing the saturation point of a column is important
since it is at this condition that the column needs to be
replaced or regenerated. This may also aid in determining
the optimal column size and operating conditions.
Effect of Varying Column Bed Height on Column
Saturation Time
The column bed height was found to have a significant
effect on the saturation time, independent of the flow rate
and initial concentration. The breakthrough curves provide
a visual representation of the exhaustion of the fixed-bed
column. The column reaches its saturation point for As(V)
at an earlier time with a shorter column bed, as seen in
Figure 1, from the endpoints of each breakthrough curve.
Table 5 shows saturation times for different column
bed heights for constant flow rates and initial As(V) con-
centrations. As the column bed height increases, the satura-
tion time for As(V) removal also increases.
An increase in the column bed height leads to an
increase in the amount of adsorbent, leading to an increase
in the number of available adsorption sites in the column.
While keeping the column radius constant, longer columns
also increase the residence time of the fluid within the col-
umn. Increasing the contact time between the fluid and the
adsorbent enhances the likelihood of adsorption. This, in
turn, also increases the adsorption capacity of the column.
(Al-Mahbashi et al., 2022)
Effect of Varying Flow Rate on Column
Saturation Time
Independent of the column bed height and the initial con-
centration, the flow rate affects the contact time of the
heavy metal species with the adsorbent. Figure 2 illustrates
the breakthrough curve for As(V) adsorption in a fixed-bed
column with varying flow rates. Here, the saturation time
decreases with increasing fluid flow rates through the col-
umn. This is also observed in the values shown in Table 6.
A higher flow rate results in a shorter contact time
between the wastewater and the adsorbent, and a lower
flow rate increases the contact time. The longer time that
the wastewater is in contact with the adsorbent, the more
time that the heavy metal species also have to diffuse into
the adsorbent pores and bind to the active sites. (Lin et al.,
2017) With an increased contact time or retention time in
the column, there is a greater degree of adsorption.
Table 4. Simulation range and levels for As(V)-containing
wastewater
Variables v High Value
Column bed height (m) 0.5 1
Flow rate (mL/min) 200 1000
Initial concentration (mg/L) 0.08 1
The column bed height was varied at 1 m and 0.5 m.
For the varying flow rate systems, 1000 mL/min and 200
mL/min were investigated. Finally, the initial concentration
of As(V) was varied according to the DENR maximum
allowable concentration of 0.08 mg/L, and 1 mg/L.
The breakthrough curve of of Ct/Co vs. t for each com-
bination of parameters was generated based on the column
outflow concentration values computed by COMSOL.
Here, Ct is the As(V) concentration at the effluent, and Co
is the initial As(V) concentration introduced to the column.
Metal Removal
The formula to compute for the concentration of the total
effluent is defined in Equation 1. This value was compared
to the DENR limit for arsenic.
Ceffluent t
C dt
total
t
t
t 0
total
==
8
(1)
Ceffluent (mg/L) is the concentration of the total treated efflu-
ent, Ct (mg/L) is the concentration of the heavy metal spe-
cies at the effluent at time t, ttotal (mins) is the time when Ct
is equal to the influent concentration Co. The performance
of the column can also be described by the metal removal
percentage from the treated wastewater. The percent metal
removal is computed using Equation 2.
C
C C
100% %Removal
o
o effluent #=
-
(2)
RESULTS AND DISCUSSION
Modifying the column bed height, flow rate, and initial
species concentration significantly influences the overall
adsorption behavior of the column. A key response that can
be measured is the saturation time. The saturation time is
defined as the time in which the fixed-bed column is satu-
rated with adsorbate and thus can no longer adsorb more
adsorbate from the wastewater, resulting in an equal adsor-
bate concentration at the outlet and in the feed wastewa-
ter. This occurs at the saturation point. At this point, the
column has been fully utilized with respect to the adsorp-
tion of a particular adsorbate.
Knowing the saturation point of a column is important
since it is at this condition that the column needs to be
replaced or regenerated. This may also aid in determining
the optimal column size and operating conditions.
Effect of Varying Column Bed Height on Column
Saturation Time
The column bed height was found to have a significant
effect on the saturation time, independent of the flow rate
and initial concentration. The breakthrough curves provide
a visual representation of the exhaustion of the fixed-bed
column. The column reaches its saturation point for As(V)
at an earlier time with a shorter column bed, as seen in
Figure 1, from the endpoints of each breakthrough curve.
Table 5 shows saturation times for different column
bed heights for constant flow rates and initial As(V) con-
centrations. As the column bed height increases, the satura-
tion time for As(V) removal also increases.
An increase in the column bed height leads to an
increase in the amount of adsorbent, leading to an increase
in the number of available adsorption sites in the column.
While keeping the column radius constant, longer columns
also increase the residence time of the fluid within the col-
umn. Increasing the contact time between the fluid and the
adsorbent enhances the likelihood of adsorption. This, in
turn, also increases the adsorption capacity of the column.
(Al-Mahbashi et al., 2022)
Effect of Varying Flow Rate on Column
Saturation Time
Independent of the column bed height and the initial con-
centration, the flow rate affects the contact time of the
heavy metal species with the adsorbent. Figure 2 illustrates
the breakthrough curve for As(V) adsorption in a fixed-bed
column with varying flow rates. Here, the saturation time
decreases with increasing fluid flow rates through the col-
umn. This is also observed in the values shown in Table 6.
A higher flow rate results in a shorter contact time
between the wastewater and the adsorbent, and a lower
flow rate increases the contact time. The longer time that
the wastewater is in contact with the adsorbent, the more
time that the heavy metal species also have to diffuse into
the adsorbent pores and bind to the active sites. (Lin et al.,
2017) With an increased contact time or retention time in
the column, there is a greater degree of adsorption.
Table 4. Simulation range and levels for As(V)-containing
wastewater
Variables v High Value
Column bed height (m) 0.5 1
Flow rate (mL/min) 200 1000
Initial concentration (mg/L) 0.08 1