Chemistry IA First Draft
RQ: To what extent do rice husk, wheat husk, coconut husk, sand, and cilantro differ in their
ability to filter polluted water, measured using spectrophotometry?
Introduction:
Ammonia is a chemical combination of elemental hydrogen (H) and nitrogen (N) occurring
extensively in nature. The physical state of ammonia is dependent on temperature and pH,
but pH normally is the determining factor. At a high pH, ammonia is expressed as NH3 and is
referred to as “free ammonia.” In this state, ammonia is a colorless gas that is partially
soluble in water.
At low pH or acidic conditions, ammonia becomes completely soluble in water and forms
ammonium (NH4+) that is referred to as “ionized ammonia.” In addition, ammonia and
ammonium also can be expressed as ammonia-nitrogen and ammonium-nitrogen,
respectively, which is the quantity of elemental nitrogen present in the form of ammonia,
expressed as NH3–N or ammonium, NH4+–N.
In high-nitrogen environments, free and ionized ammonia coexists and the quantities of
each are summed to measure the concentration of total ammonia in mg/L. The general
chemical behavior of free and ionized ammonia in water is described by the formula
NH3–N + H2O = NH4+–N + OH–
Ammonia-Nitrogen + Water = Ammonium-Nitrogen + Hydroxyl ion
Under conditions of low pH, the high concentration of hydrogen ions, H+, converts ammonia
to ammonium as described by the following equation.
NH3–N + H+ Æ NH4+–N
Ammonia-Nitrogen + Hydrogen Ion Æ Ammonium-Nitrogen
Under conditions of high pH, ammonium is converted to ammonia by the following
equation.
NH4+–N Æ NH3–N + H+
Ammonium-Nitrogen Æ
Ammonia-Nitrogen + Hydrogen Ion
Measuring Ammonia Levels
Treatment facilities use online ammonia analyzers to monitor and control treatment
processes. Controlling ammonia levels can make treatment processes more reliable and cost
effective.
Wastewater treatment plants use online ammonia analyzers to optimize activated sludge
and biological nutrient removal (BNR) processes. For example, ammonia is a nutrient,
byproduct or feed additive for all activated sludge wastewater treatment processes.
In addition, some advanced wastewater treatment plants use online ammonia analyzers to
monitor nitrification to meet ammonia discharge limits. Finally, some water treatment
plants use online ammonia analyzers when monitoring chloramination, a drinking water
treatment process used to create a disinfectant residual.
Types of Online Ammonia Analyzers
Currently, there are three major types of online ammonia analyzer technologies available to
measure ammonia concentration in a treatment process stream:
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Colorimetric,
Ion-selective electrodes (ISE), and
Ultraviolet (UV) absorbance or multiple wavelength UV absorbance
spectrophotometers.
Each technology detects ammonia concentrations using different analytical methods. In
addition, manufacturers of each technology utilize different methodologies for such
functions as sample transport, sample conditioning, chemical addition, primary
measurement and secondary signal conditioning and amplification.
All of these analyzers require the addition of chemical reagents to the sample. Therefore,
each analyzer has a sample cell and requires 3 to 15 minutes to perform a complete sample
analysis. Automatic calibration and cleaning cycles are available options with ammonia
analyzers.
Calibration and cleaning cycles may take 15 to 45 minutes per cycle and occur between
measurement cycles. The analyzer holds the output value from the last measurement cycle
while performing the next measurement, calibration or cleaning. If the process ammonia
concentration changes significantly during one of these cycles, the analyzer output will show
that change in concentration after the next measurement cycle. Figure 1 shows an example
of the analyzer output step change. In addition, each analyzer has an electronics module
that controls sample processing and converts signals from the sample cell to an output
signal.
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Colorimetric Ammonia Analyzers
Online colorimetric ammonia analyzers use a colorimeter (a light intensity meter capable of
measuring the intensity of light at a specific wavelength) to measure the color intensity of
sample solutions. The ammonia analyzer colorimeter is set to measure light intensity at a
wavelength within the range of 645–655 nm. The color is produced by the addition of
reagents to the sample and its intensity is proportional to the free ammonia concentration
in the sample. This method of measurement is based on the Standard Methods phenate
method 4500-NH3 – F (APHA et al., 1998).
The ammonia colorimeter compares the color intensity of two wastewater samples. The
first is a reference sample and is used as a basis for comparison with the second test
sample. To produce the color, the free ammonia in the sample is first converted to
monochloramine by the addition of hypochlorous acid.
NH3–N + HOCl Æ NH2Cl + H2O
Ammonia-Nitrogen + Hypochlorous Acid Æ Monochloramine + Water
The ammonia colorimeter first treats the sample with reagent (1) that acts as a buffer to
adjust the pH to a value greater than 12. Raising the pH of the sample forces any ammonium
ions to convert to free ammonia.
NH4+–N Æ NH3–N + H+
Ammonium-Nitrogen Æ
Ammonia-Nitrogen + Hydrogen Ion
After reagent (1) is added, reagent (2) is added to the reference sample as a color indicator,
specific for monochloramine. When reagent (2) combines with any monochloramine in the
first sample, the solution turns green. The color intensity increases in direct proportion to
the concentration of monochloramine. The colorimetric analyzer reads the color intensity.
Since no hypochlorous acid was added to the reference sample, the color intensity is a
measure of the amount of monochloramine initially present in the wastewater and also
ensures that the colorimeter corrects for any other interference.
The colorimetric analyzer then takes a second sample solution and adds reagent (1), a buffer
that converts ammonium ions to free ammonia. The analyzer then adds hypochlorous acid
(HOCl) that converts any available free ammonia to monochloramine. Finally, the analyzer
adds the monochloramine specific reagent, which turns the second sample solution green.
At this time, the colorimetric analyzer reads the color intensity in the second sample
solution that is a measure of the amount of monochloramine produced by the reaction of
free ammonia in the sample with the hypochlorous acid.
Free ammonia concentration is calculated by subtracting the first sample solution’s
reference monochloramine concentration from the second sample solution’s
monochloramine concentration. Total ammonia concentration is calculated by adding the
first sample solution’s reference monochloramine concentration to the second sample
solution’s monochloramine concentration. Figure 2 illustrates a generic colorimetric
ammonia analyzer and its basic components.
Ion-Selective Electrode (ISE) Ammonia Analyzer
Online ISE ammonia analyzers are probe-type analyzers that use an ammonia ISE and a
reference electrode. This method of measurement is similar to Standard Methods
ammonia—selective electrode reference 4500-NH3–D (APHA et al., 1998).
The ISE ammonia analyzer feeds sample through a flow cell or sample chamber. Sodium
hydroxide (NaOH) is added to the sample to raise its pH to a value greater than 11, to
convert all ammonia to free ammonia, NH3. (Note that the sample chamber is not pictured
in Figure 3 due to variations in manufacturers’ designs.)
Any free ammonia released in the sample chamber from the reaction with the sodium
hydroxide reagent permeates into the ISE ammonia analyzer membrane cap. The
membrane cap’s internal solution of ammonium chloride (NH4Cl) reacts with the free
ammonia and changes the pH of the membrane cap’s ammonium chloride solution.
The ISE analyzer probe measures the change in pH of the membrane cap’s ammonium
chloride solution that is proportional to the amount of free ammonia concentration in the
sample solution. The ISE ammonia analyzer electronics module uses the change in pH to
calculate the concentration of free ammonia in the sample.
The ISE ammonia analyzer probe measures the change in pH of the membrane cap’s
ammonium chloride solution (similar to a standard pH probe) using three sensors; a pH or
measuring electrode sensor, a reference electrode sensor and a resistance temperature
device or detector (RTD) sensor.
The pH or measuring electrode sensor consists of a thin glass membrane filled with a neutral
buffer solution (i.e., a solution that has a pH of 7) that is immersed in the membrane cap’s
ammonium chloride solution. The pH sensor’s thin glass membrane contains a silver wire
coated with silver chloride that is suspended in the neutral buffer solution. When the
sample solution from the ISE ammonia analyzer sample chamber releases free ammonia
into the membrane cap’s ammonium chloride solution, hydrogen ions pass through the pH
sensor’s thin glass membrane and cause the silver wire to conduct. Charged hydrogen ions
flow through the wire to produce an output voltage in logarithmic proportion to the
hydrogen ion concentration present in the membrane cap’s ammonium chloride solution.
The reference electrode sensor establishes a stable reference voltage output for the ISE
ammonia analyzer’s electronics module. This reference electrode connects to a porous
reference junction filled with an electrolyte solution (gel or liquid). The electrolyte solution
contains a predetermined concentration of hydrogen ions that provides a stable reference
voltage output to the electronics module.
The temperature sensor allows the electronics module to compensate for temperature
changes in the sample solution. An RTD most often is used to measure temperature
changes.
All of these ISE ammonia analyzer components—the membrane cap filled with NH4Cl
solution, the pH sensor, the reference electrode sensor, the porous reference junction and
the temperature (RTD) sensor—may be contained inside a single ammonia ISE probe. The
ISE ammonia analyzer consists of the single ammonia ISE probe and an electronics module.
The ammonia analyzer electronics module uses sensitive input electronics and a
microprocessor to analyze all of the input signals from the sensors and calculate the free
ammonia concentration. The ISE ammonia analyzer electronics module usually is remotely
mounted and can be connected to a control and automation system. ISE ammonia analyzer
components vary by manufacturer. Figure 3 illustrates a generic ISE ammonia analyzer and
its basic components.
Background Information:
In short, filtration and separation can be any mechanical, physical or biological operation
used to separate solids from liquids, by causing the latter to pass through the pores of some
substance, called a filter. This filter can be paper, cotton-wool, sand or any other porous
material.
This processes are used both in nature and in engineered systems. For example, one type of
filtration that is useful for all of us is the filtration of the water we are drinking – it’s
extremely important to confirm your water has been purified or treated before drinking.
This type of separation is relatively easy and water purification can be done by boiling,
filtration, distillation or chlorination. While filtration is an important separation technique in
engineered systems, it’s also common in everyday life.
Besides filtrating the water we are drinking, there are many more everyday activities where
this process can be used:
Many aquariums use filters
The kidneys are also an example of a biological filter
Air conditioners and vacuum cleaners use filter to remove dust
Brewing coffee involves passing hot water through the ground coffee and a filter
Typically, filtration is an imperfect and a not-so-easy process when it comes to mechanical
or physical operations. For example, the two problems that usually occur are that part of
the liquid can somehow stay stuck in the filter or some of the small solid parts can find their
way through the filter. That’s why, there are different types of filtration. Which method will
be used depends largely on whether the solid is a particulate (suspended) or dissolved in the
fluid. The important thing is that they all aim to attain the separation of substances. The
selection of the appropriate method or technique is usually determined by the nature of the
situation. Usually, there are four methods commonly used for filtration and separation:
General, Vacuum, Hot and Cold Filtration.
General Filtration
General Filtration, also known as Gravity Filtration , it is the most commonly used method to
remove an insoluble solid material from a solution. It is the most basic form that uses
gravity to filter a mixture. This mixture is poured from above onto a filter and gravity pulls
the liquid down. It uses a polyethylene or glass funnel with a stem and filter paper. Most of
the solid in the mixture should settle before filtering. The solid will stay in the filter, while
the liquid will flow below it.
Vacuum Filtration
In this type of filtration, the solution that needs to be filtered is drawn through a filter paper
by applying a vacuum to a filter flask with a side arm adaptor. It is usually very fast and
efficient way of filtering. Related to this, there is a similar technique that uses a pump to
form a pressure difference on both sides of the filter. Lastly, when applying vacuum
filtration, it is very important that the correct size of filter paper is used.
Cold Filtration
This method uses an ice bath to rapidly cool down the solution instead of leaving it out to
slowly cool down in room temperature. In general, it is used to quickly cool a solution when
the solid is initially dissolved, prompting the formation of small crystals instead of getting
large crystals when cooling the solution down at room temperature.
Hot Filtration
Sometimes during a Gravity Filtration, crystals can grow in the filter and stop the process of
separation. This is where Hot Filtration comes in handy. By using Hot Filtration, the solution,
filter and funnel are heated to minimize the formation of crystals in the filter. It is best
carried out using a fluted filter paper and a stemless filter funnel. Due to the absence of
stem in the filter the re- crystallization of solid in the funnel is prevented. This is one of the
most efficient and commonly used measures used to prevent the formation of crystals.
What are the alternatives to filtration?
As with every technique and method, there are many alternatives and separation methods
other than filtration. Although filtration is a very efficient method for separation, it can be
much more time consuming. For example, if very small amounts of solution are involved,
the filter may soak up too much of the fluid and cause a problem. In other cases, the solid
material can stay trapped in the filter. That’s why, two other processes that are usually used
rather than filtration are decantation and centrifugation. In short, centrifugation involves
spinning a sample, rather than filtering the mixture of solid and liquid particles. It can be
extremely useful for solids which don’t filter well. In decantation, the layer closer to the top
of the container which is less dense of the two liquids is poured off, leaving the other
component or the more dense liquid of the mixture behind. It is also known as incomplete
separation. Although there are many other alternatives, Filtration is still one of the most
efficient and commonly used techniques.
Methodology:
1. Make a small paper container and place it on the weighing balance and tarre it. Take
an appropriate amount of salicylic acid for the trial and weigh it on the weighing
balance.
2. Add the chemical to a 100ml conical flask from the paper container
3. Pour distilled water in a 250ml beaker and pipette out 25ml of distilled water adding
it to a 25ml measuring cylinder.
4. Pour the distilled water in the measuring cylinder in the conical flask and allow the
salicylic acid to dissolve in the distilled water.
5. Pour n-octanol in a 250ml beaker and pipette out 25ml of n-octanol and add it to a
25ml measuring cylinder.
6. Pour the n-octanol in the measuring cylinder in the conical flask and put a rubber
cork at the mouth of the conical flask
7. Shake the flask continuously for 7 minutes and then allow the flask to sit on a table
for the 2-phase separation between n-octanol and water to occur.
8. Once the octanol and water in the conical flask separates in the flask, slowly remove
the rubber cork.
9. Use a 10ml pipette to pipette out 10ml of aliquot from lower phase (water) from the
conical flask and transfer it to another 100ml conical flask. Add 2 drops of
phenolphthalein indicator solution to the solution in the new conical flask
10. Fill a burette with 50ml of 0.1M NaOH solution with the stop cock below closed
11. Place the new conical flask mentioned step 9 below the burette and slowly allow the
NaOH solution to fall drop by drop in the new conical flask to titrate the salicylic acid
solution in
water. Continue to swirl the conical flask while adding NaOH solution
12. Once the color of the solution in the conical flask changes to pink close the stop cock
of the burette and take a reading of the amount of NaOH required to titrate the
salicylic acid
solution.
13. Repeat this using salicylic acid taking readings for 5 trials
14. Taking an appropriate amount of chemical for each of the other acids repeat the
above steps
for citric acid, folic acid, tartaric acid, malic acid. The appropriate amounts for each
chemical can be decided by performing a Trial 0 for each acid.
Apparatus and Reagents:
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100ml conical flask
50ml burette (±0.05ml) (Least Count: 0.1ml)
0.1M Sodium hydroxide solution (NaOH)
10ml pipette (±0.03ml)
25ml pipette (±0.05ml)
Pipette pump
Spatula
Rubber cork
Weighing balance (±0.01g) (Least Count: 0.01g)
25ml measuring cylinder (Least Count: 1ml)
250ml beakers
Salicylic acid powder
n-octanol
Distilled water
Folic acid powder
Tartaric acid powder
Citric acid powder
Malic acid powder
Variables:
Independent variable: The acids used were varied. 5 different types of acids were chosen to
mimic different natural (tartaric acid in papaya pulp, citric acid in the juice of lemons, malic
acid in apple skins, folic acid in ground spinach) and chemical treatments of acne (salicylic
acid in acne creams).
Dependent variable: The octanol-water partition coefficient. The octanol-water partition
coefficient indicates the lipophilicity of the acid and ability to dissolve lipids. The volume of
0.1M NaOH solution used to titrate the acid dissolved in the water phase of the octanolwater two-phase system was used to find the octanol-water partition coefficient.
Raw Data:
Data Processing:
Conclusion:
Evaluation:
References:
References:
https://openprairie.sdstate.edu/cgi/viewcontent.cgi?article=1145&context=jur
https://www.labonline.com.au/content/lab-equipment/article/analytical-determination-ofions-in-water-80359249
https://www.who.int/news-room/fact-sheets/detail/arsenic
https://www.coleparmer.com/tech-article/kjeldahl-method-for-determining-nitrogen
https://w4ww.wwdmag.com/disinfection/article/10917719/measuring-ammonia-withonline-analyzers
Raw Data:
Material
Optical Density at 950 nm
Trial 1
Initial Final
Trial 2
Initial Final
Trial 3
Initial Final
Trial 4
Initial Final
Trial 5
Initial Final
Trial 6
Initial Final
Coconut
Husk
0.053 0.002 0.046 0.003 0.061 0.006 0.061 0.034 0.046 0.005 0.074 0.021
Rice
Husk
0.021 0.000 0.028 0.018 0.053 0.000 0.048 0.003 0.079 0.004 0.067 0.005
Wheat
Husk
0.017 0.001 0.041 0.011 0.081 0.023 0.054 0.001 0.061 0.022 0.055 0.026
Cilantro
0.063 0.002 0.051 0.009 0.047 0.002 0.064 0.004 0.049 0.003 0.062 0.002
Sand
0.056 0.004 0.057 0.038 0.059 0.061 0.043 0.004 0.056 0.002 0.049 0.011
Observations:
- Wheat husk took significantly longer to allow water to pass through
- The sad also took time to pass through the water
- Pre-filtration, water has a brownish color