The document summarizes an experiment that tested factors affecting the efficiency of dye adsorption using batch and continuous separation processes. The experiments showed that as resin mass increases, the adsorption ratio (q) decreases, as the resin does not need to reach saturation to adsorb all the dye. To maximize adsorbent usage, it is best to use lower resin masses to take full advantage of the surface area before replacing it. While this leads to a higher q value, there is a tradeoff with a longer adsorption time. The maximum adsorption for the dye and resin combination tested was determined to be 21.69 mg of dye per gram of resin based on Langmuir equation analysis of the batch process results. More

1. 1
MEMORANDUM
Date: October 6, 2015
To: Scott Shearman
Dr. Nielsen, Professor, CHE451
From: Vanessa Ferrero, in conjunction with
Faisal Alsaid, Mathew Lee, Cindy Rivera, James White
Team 7 Section 70673
Subject: A study into factors affecting efficiency of dye adsorption
Summary
An experiment was run to determine the differences between batch and continuous
adsorption separation processes for dye adsorption. The batch process tested various initial resin
masses as well as dye concentrations while the continuous process tested various flow rates and
initial resin masses. The experiments showed that overall, as resin mass increases the ratio of
adsorption, q, decreases as the molecules do not need to reach saturation in order to adsorb all of
the dye. To get the most out of an adsorbent it would be best to include low amounts in a system
in order to use the full surface area before replacing the adsorbent. A balance must be found
between this higher q value and the longer time it takes to adsorb with lower adsorbent mass in
order to design the optimal system.
Introduction
 The purpose of this experiment was to test the effects of dye concentration and resin mass
on the adsorption of the dye, as well as comparing the effectiveness of batch versus
continuous systems (including the effects of flow rates in the continuous system).
 Adsorption is a common separation process in which a substance in one phase
accumulates onto the surface of another substance (see Figure 1)1
. The former, the
adsorbate, is generally a gas or liquid while the latter, the adsorbent, is generally a solid.2
This differs from absorption, where one substance is interpenetrated into the bulk of
another.
Figure 1: Diagram of Adsorption.1
 Common adsorption systems used in industry include column contact adsorbers, slurry
contact adsorbers, and pressure swing adsorbers.2
Column contact adsorbers generally
run continuously, while slurry contact adsorbers can run as either batch or continuous

2. 2
process depending on the desired application.2
Pressure swing adsorbers are generally
used for adsorption of substances in the gas phase.2
 For any given adsorption process, optimization is key: knowing whether to use a
continuous or batch system and which flow rates, concentrations, or masses to use are
important factors when deciding which process to implement. Because of this, these
factors were tested through a small-scale experiment in order to have a better
understanding of their relationships to adsorption.
 A key equation used to compare various adsorption levels is the Langmuir equation,
which is a derived relationship between C and k.3
For this equation, one must assume a
uniform surface, a single layer of adsorbed material (monolayer adsorption), and constant
temperature.3
Figure 2 depicts the difference between monolayer and multilayer
adsorption.
(a) (b)
Figure 2: Diagram of (a) monolayer adsorption and (b) multilayer adsorption.1
 The original Langmuir model derives expressions for the rate of adsorbate attachment to
the adsorbent as well as the rate of evaporation from the surface of the adsorbent.3
At
equilibrium these rates are equal, and through algebraic manipulation Equation 1 is
derived.3
1
𝑞
=
1
𝑞 𝑚
+
1
𝐾 𝑎 𝑞 𝑚 𝐶
[1]
 q is the mass of adsorbate adsorbed per mass of adsorbent, in the case of this experiment
the adsorbate is dye and the adsorbent is resin.4
It can be found by Equation 2 below,
based on the volume of solution, mass of resin, and concentration.4
𝑞 = (𝐶0 − 𝐶)(𝑉/𝑊) [2]
 The equations above will be used in analyzing the data to compare the maximum
adsorption ratios for the various systems.
Methodology
 For testing conditions in the batch process:
o Various masses of resin were added to beakers and 100mL of dye solution was
added to each beaker. The concentration of each beaker was measured as time
went on (every few minutes) by taking a sample of the solution and running it
through a spectrometer.
 For the 35mg/L dye solution, eight different resin masses were tested
while for the 14.7mg/L solution only four masses were tested.
o Samples were taken from each beaker until the data started leveling off and the
system reached equilibrium, at which point the trial for that mass amount ended.

3. 3
Two runs of each resin mass and dye solution concentration pairing were done to
verify repeatability of results.
o Figure 3 shows the concentration gradient by the time four different systems had
reached equilibrium, from 0.3g of resin on the left to 0.15g of resin on the right.
Figure 3: Image of batch set up showing concentration gradient between 0.3g and 0.15g of resin.
 For testing conditions in the continuous process:
o Various masses of resin were added to the column while running the same flow
rate of dye solution through the column. The concentration of the output solution
was measured every few minutes by taking a sample and running it through the
spectrometer until it reached a minimum and then eventually levelled out.
o A run was also done to see the effects of flow rate, keeping the mass of resin
around the same while changing the flowrate of solution going through the
column.
o Figure 4 shows the continuous set up and a close up of the adsorption process.
(a) (b)
Figure 4: (a) continuous adsorption tower set up and (b) close up of column during adsorption.

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Results and Discussion
For adsorption as a batch process…
Figure 5: Adsorption ratio graphed as a function of resin mass for different initial concentration values.
Figure 5 shows that as the resin mass increases the q value decreases. This is because
more resin means each individual resin sphere does not need to adsorb to saturation; in other
words, the lower the mass of resin, the more it will adsorb as it removes dye from the solution.
Had there been much more concentration of dye, it would be expected that the larger resin
masses would also become as saturated as the lower resin masses were at this lower
concentration value.
Figure 6: Relation between 1/q and 1/C used for linear fit to determine qm and Ka for system.
0
5
10
15
20
25
0 0.2 0.4 0.6 0.8
q(mgdye/gresin)
Resin Mass (g)
C0=35mg/L
C0=14.7mg/L
y = 0.0856x + 0.0461
R² = 0.9744
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 0.2 0.4 0.6 0.8 1 1.2
1/q(gresin/mgdye)
1/C (L/mg)

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Figure 6 shows the relationship between the concentration and q values found. When a
linear trend is set to this, the slope is equal to 1
𝐾𝑎 𝑞 𝑚
⁄ while the y-intercept gives the value of
1
𝑞 𝑚
⁄ . With this information, the value of qm for the resin can be determined for this specific dye
solution. From the linear equation, qm must be 21.69mg/g while the constant Ka is 0.54.
Calculations for these values can be found in Appendix A.
For adsorption as a continuous process…
Figure 7: Adsorption ratio q as a function of resin mass for continuous process.
Figure 7 shows that the adsorption ratio goes down as resin mass increases in the
continuous process. This is much like what was observed in Figure 5 for the batch process.
Conclusions and Recommendations
 As resin mass increases in a given concentration of solution, the adsorption ratio will
increase (due to the fact that the molecules will not need to become as saturated in order
to adsorb the same amount of material).
 Because of this, it would be best to conserve material by using less and adsorbing to
saturation as opposed to adsorbing faster but wasting material surface area. A balance
must be found between the time one waits for the resin to adsorb and the amount of resin
you want to fully use up.
 The maximum adsorption for this dye and resin combination was 21.69mg of dye per g of
resin.
 More tests should be run for the continuous set up because not enough data was gathered
for that to make any clear conclusions.
0
2
4
6
8
10
12
0 1 2 3 4 5 6
q(mgdye/gresin)
Resin Mass (g)

6. 6
References
[1] Adsorption Image http://www.intechopen.com/source/html/21847/media/image2.png
(accessed Oct 5, 2015).
[2] Catalano, S.; Lawrence, J.; Seadeek, C.; Palazzolo, J.; Wesorick, S.; Cotton, S. Adsorbers -
Separations: Chemical - MEL Equipment Encyclopedia
http://encyclopedia.che.engin.umich.edu/Pages/SeparationsChemical/Adsorbers/Adsorbers.ht
ml (accessed Oct 4, 2015).
[3] Langmuir equation http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Adsorb/langmuir.htm
(accessed Oct 5, 2015).
[4] Gamal, A. M. Nature and Science 2010, 95–110.
Notation
C0… initial concentration of dye (mg/L)
C… concentration of dye (mg/L)
Ka… Langmuir equation constant of adsorption
qm…maximum adsorption ratio (mg dye/g resin)
q…adsorption ratio (mg dye/g resin)
V… volume of system (mL)
W… mass of resin (g)

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Appendix A
Batch- Calculations of qm and Ka
From 𝑦 = 0.0461 + 0.0856𝑥
0.0461 =
1
𝑞 𝑚
Therefore 𝑞 𝑚 =
1
0.0461
= 21.69
0.0856 =
1
𝐾𝑎 𝑞 𝑚
Therefore 𝐾𝑎 =
1
0.0856𝑞 𝑚
=
1
(0.0856)(21.69)
= 0.54