4
3) Calculating Adsorption and Desorption
Table 3. Equations used for calculating adsorption and
desorption of the resins
Parameter Equation
Total adsorption of Xth ion in
loading process (A
x )
A
x (1)
Bed volume difference (Bxi) Bxi =BVi – BV(i–1) (2)
Total adsorption of Xth ion in
mili equivalent (Ax)meq
Axmeq =Ax/Mx *Vx (3)
Total desorption of Xth ion in
Regeneration process (D
x )
D
x =∑n (Cxi Vi) i =0
(4)
Total desorption of Xth ion in
mili equivalent
D
x(meq) =D
x /M
x *V
ex (5)
Percentage recovery (R%) Dx(meq)/Ax(meq) *100 (6)
where,
Cx feed =concentration of the ion x in the feed solution
Cxi =concentration of the ion x in the ith bed
volume
BVi =Bed volume number of ith sample
BV(i–1) =Bed volume number of the (i–1) sample
Mx =atomic weight of the element x
Vex =valency of ion x
Ci =concentration of the ith sample
Vi =volume of the ith sample
III. RESULTS
A. Results of the Soudan Mine in Minnesota
This is the case of the first iron mine in Minnesota which
has been operating since 1963. The mine is known to have
a depth of about 730 m and some 18 levels (Eger et al.,
2001). A 3,800 L pressurized tank containing 1,900L of the
peat-based sorption media was designed. This was meant to
allow the media to be freely backwashed to discard par-
ticulates. The water enters through the top lateral outlets,
comes down through the media into the gravel collection
unit and exits through the bottom lateral outlets. The back-
washing is then done by simply turning back the flow. This
experiment has treated more than 32,000 bed volumes. We
must appreciate that the total number of bed volumes is
correlated to volume of water being treated.
B. Result of the Small Column Tests 1) Experiment A:
APTsorb
The APTsorb material must be in a wet condition to be
directed into the column (Dorfner, 1963). The measured
values of zinc concentration show that after 18BV and
35BV, the initial value of the zinc in the solution is reached
and even surpassed. Previously, the curve for zinc shows a
small slope. Between 2BV and 18BV, the zinc content in
the solution rises quite sharp even flattening from BV18
and BV35 rising to the initial concentration before it falls
steeply. Initially, the pH is 7.4 but as the experiment goes
further, the pH finishes just slightly above 7.4. We can also
see from the graph that the Eh increases just around the
18BV and 35BV where the zinc concentration is higher
even above the initial concentration. This means that the
zinc precipitated due to the solution being in an oxidation
zone. The Eh curve further reduces along as the zinc con-
centrations also reduces showing less precipitation and
more zinc in solution. This is true for standard zinc because
it will always be in a reduced form.
When we look at the graph, we realize that break-
through was achieved over the entire experiment after the
flow through of 2BV. The total adsorbed zinc was 1.785 mg
and the total desorbed zinc was -0.068 mg all correspond-
ing to an adsorption capacity of 0.01 meq/g for the mate-
rial. This capacity is very less compared to what is provided
by the manufacturer which is 0.45 meq/g. Also in com-
parison to Lisa Johnke who worked with similar material
Figure 4. Result of the APTsorb resin with respect to Zinc
concentration, pH and Eh
Table 2. Table showing the various Resins used for the
experiment and their respective masses
Name of Resin Mass Used (g)
APT (sorp). (A) 7g
Activated Coke (B) 5g
Charred fermentation residue(C) 2,55
3) Calculating Adsorption and Desorption
Table 3. Equations used for calculating adsorption and
desorption of the resins
Parameter Equation
Total adsorption of Xth ion in
loading process (A
x )
A
x (1)
Bed volume difference (Bxi) Bxi =BVi – BV(i–1) (2)
Total adsorption of Xth ion in
mili equivalent (Ax)meq
Axmeq =Ax/Mx *Vx (3)
Total desorption of Xth ion in
Regeneration process (D
x )
D
x =∑n (Cxi Vi) i =0
(4)
Total desorption of Xth ion in
mili equivalent
D
x(meq) =D
x /M
x *V
ex (5)
Percentage recovery (R%) Dx(meq)/Ax(meq) *100 (6)
where,
Cx feed =concentration of the ion x in the feed solution
Cxi =concentration of the ion x in the ith bed
volume
BVi =Bed volume number of ith sample
BV(i–1) =Bed volume number of the (i–1) sample
Mx =atomic weight of the element x
Vex =valency of ion x
Ci =concentration of the ith sample
Vi =volume of the ith sample
III. RESULTS
A. Results of the Soudan Mine in Minnesota
This is the case of the first iron mine in Minnesota which
has been operating since 1963. The mine is known to have
a depth of about 730 m and some 18 levels (Eger et al.,
2001). A 3,800 L pressurized tank containing 1,900L of the
peat-based sorption media was designed. This was meant to
allow the media to be freely backwashed to discard par-
ticulates. The water enters through the top lateral outlets,
comes down through the media into the gravel collection
unit and exits through the bottom lateral outlets. The back-
washing is then done by simply turning back the flow. This
experiment has treated more than 32,000 bed volumes. We
must appreciate that the total number of bed volumes is
correlated to volume of water being treated.
B. Result of the Small Column Tests 1) Experiment A:
APTsorb
The APTsorb material must be in a wet condition to be
directed into the column (Dorfner, 1963). The measured
values of zinc concentration show that after 18BV and
35BV, the initial value of the zinc in the solution is reached
and even surpassed. Previously, the curve for zinc shows a
small slope. Between 2BV and 18BV, the zinc content in
the solution rises quite sharp even flattening from BV18
and BV35 rising to the initial concentration before it falls
steeply. Initially, the pH is 7.4 but as the experiment goes
further, the pH finishes just slightly above 7.4. We can also
see from the graph that the Eh increases just around the
18BV and 35BV where the zinc concentration is higher
even above the initial concentration. This means that the
zinc precipitated due to the solution being in an oxidation
zone. The Eh curve further reduces along as the zinc con-
centrations also reduces showing less precipitation and
more zinc in solution. This is true for standard zinc because
it will always be in a reduced form.
When we look at the graph, we realize that break-
through was achieved over the entire experiment after the
flow through of 2BV. The total adsorbed zinc was 1.785 mg
and the total desorbed zinc was -0.068 mg all correspond-
ing to an adsorption capacity of 0.01 meq/g for the mate-
rial. This capacity is very less compared to what is provided
by the manufacturer which is 0.45 meq/g. Also in com-
parison to Lisa Johnke who worked with similar material
Figure 4. Result of the APTsorb resin with respect to Zinc
concentration, pH and Eh
Table 2. Table showing the various Resins used for the
experiment and their respective masses
Name of Resin Mass Used (g)
APT (sorp). (A) 7g
Activated Coke (B) 5g
Charred fermentation residue(C) 2,55