Student Project - Gordon College - Green Chemistry

Summary Assessment Report
Experiment: Hydrolysis of Post-Consumer Polylactic Acid Waste
Background: This laboratory exercise was evaluated as part of the design of a hands-on
workshop entitled Implementing Green Chemistry in the Laboratory for the Biannual Conference
on Chemical Education delivered on Tuesday, July 29, 2008
Workshop design focused on selecting a core of six laboratory exercises that could be
implemented in a variety of learning contexts (general, organic, non-majors etc.) and be
adapted to a “cooking show” format. This format was developed so that participants could set up
the reactions and then work with previously prepared materials to complete the laboratory
experience within 30 minutes.
During the final phase of development, three undergraduate chemistry students from Gordon
College tested and optimized the revised laboratory procedures for the workshop during spring
semester 2008. This work was completed as part of a Green Organic Literacy Forum (GOLuM)
project associated with their sophomore organic chemistry course taught by Professor Irv Levy
at Gordon College.
• Bethany Corcoran, Gordon College
• Zackary Schwamb, Gordon College
• Christopher Tanga, Gordon College
This BCCE workshop was collaboratively designed, tested, and delivered by members of the
Green Chemistry Education Network (GCEdNet) and undergraduate chemistry students at
Gordon College. The Green Chemistry Education Network (GCEdNet) serves as a catalyst for
integrating green chemistry in chemical education at all levels. As a network of educators, we
support opportunities to research, develop, implement and disseminate green educational
materials. The GCEdNet reaches out to all chemistry educators through collaborating and
mentoring, facilitating professional growth, and fostering the synergistic integration of green
chemistry in education.
Experiment: Hydrolysis of Post-Consumer Polylactic Acid Waste 1

Experiment: Hydrolysis of Post-Consumer Polylactic Acid Waste
Reviewed by: Zack Schwamb, organic chemistry student at Gordon College and submitted to
GEMs May 2008.
Assessment Summary (number of replications = 2)
Answer the following on a scale of 1-5 where 1 is strongly disagree and 5 is strongly agree.
Lowest to Highest
As I prepared the method, it was very clear: 1 2 3 4 5
The method worked as expected when I performed it: 1 2 3 4 5
The method worked as expected when I ran it for someone else: 1 2 3 4 5
This is a useful way to introduce principles of green chemistry: 1 2 3 4 5
The estimated time was consistent each time I performed it: 1 2 3 4 5
Cost of starting materials:
Item Name Cost Unit
PLA cups free Dependent on size of cups
Sodium Hydroxide pellets $36 100 grams
50% Ethanol $25 1 liter ethanol
50% HCl (6 HCl) $15 250 grams/liter HCl
Safety concerns: safety data was found from http://www.chemexper/.
NaOH
• C: Corrosive
• 35: Causes severe burns
• 26: In case of contact with eyes, rinse immediately with plenty of water and seek medical
advice
• 37/39: Wear suitable gloves and eye/face protection
• 45: In case of accident or if you feel unwell, seek medical advice immediately (show the
label where possible
HCl
• C: Corrosive
• 34: Causes burns
• 37: Irritating to respiratory system
• 26: In case of contact with eyes, rinse immediately with plenty of water and seek
medical advice
• 45: In case of accident or if you feel unwell, seek medical advice immediately (show the
label where possible)
Experiment: Hydrolysis of Post-Consumer Polylactic Acid Waste 2

Ethanol
• F: Highly flammable
• 11: Highly flammable
• 20/21/22: Harmful by inhalation, in contact with skin and if swallowed
• 68/20/21/22: Harmful: possible risk of irreversible effects through inhalation, in contact
with skin and if swallowed.
• 7: Keep container tightly closed
• 16: Keep away from sources of ignition- no smoking
• 36/37: Wear suitable protective clothing and gloves
• 45: In case of accident or if you feel unwell, seek medical advice immediately (show the
label where possible)
Safety
• Sodium hydroxide is corrosive to the skin. Goggles and gloves should be worn
throughout the experiment.
• Hydrochloric acid is also harmful and corrosive. Goggles and gloves should be worn
when handling this chemical.
• Ethanol is not extremely harmful or corrosive. However, to be safe goggles and gloves
should be worn to remain safe and protected.
Quantity of hazards and waste: This measurement can vary between experiments depending
on how much ethanol and HCl is added to the solution.
Special equipment/materials needed: Besides the PLA cups and a hot plate with a magnetic
stirrer, there is no special equipment necessary for the experiment to be run.
Materials:
• PLA cup
• 250 mL Erlenmeyer flask
• 500 mL beaker
• Sodium hydroxide pellets
• 50% HCl (6 M HCl)
• 50% ethanol
• Magnetic stir bar
• Hot plate with a magnetic stirrer
• Stirring rod
• Watch glass
• pH paper or meter
• Filter paper
• Equipment necessary for a vacuum filtration
• Scale
Notes/Comments: The actual lab time for the experiment was about an hour and a half to two
hours. As a result, if this was done as a presentation for others within a 15-20 minute window,
multiple experiments must be going on at different steps. This would skip long periods of waiting
and mixing, and would make presenting to an audience easier to handle. Possibly 3-4
experiments may need to go on at once.
A few areas of the experiment worth pointing out are about the 50% HCl and the alternative step
of using a microwave. There is no such thing as 50% HCl and this may be confusing for some to
figure out. It would be more clear to write 50% HCl as 6 M HCl instead. In step 8a there is the
Experiment: Hydrolysis of Post-Consumer Polylactic Acid Waste 3

alternative step of using a microwave to speed up the chemical process. I did not try this step in
my own experiments because it seemed too dangerous. It does not seem like a very good idea
to put a solution with alcohol into a microwave. This could be dangerous.
Although listed in the above procedure, I did not do step 11 and recommend that it not be done
during demonstration. Performing step 11 would take up a lot of time and would result in the
experiment being well over two hours.
Besides the notes above, the experiment extremely well and ran very smoothly. It is very clear
and easy to follow and understand. It is also a great example of green chemistry.
Hydrolysis of Post-Consumer Polylactic Acid Waste (tested base hydrolysis procedure)
1. Measure 5.0 g (0.07 mol) of shredded PLA
2. Measure 5.6 g (0.14 mol) of NaOH
3. Retrieve a 250 mL Erlenmeyer flask
4. Have the Erlenmeyer flask containing a magnetic stir bar
5. Put everything into the Erlenmeyer flask
a. When the PLA is added to the base hydrolysis solution, the chips of PLA should
go into solution relatively quickly. If not, then you have not performed the correct
stoichiometric calculation for adding the appropriate amount of base to react with
all of the PLA
6. Add enough 50% ethanol to cover the contents in the flask
7. Cover the mouth of the flask with a small watch glass
8. Heat the reaction to a brisk boil with constant stirring for one hour to ensure complete
hydrolysis of the PLA
a. Alternatively, you can use a household microwave to speed up the process.
Microwave the reaction mixture on high for no more than 4 minutes at a time.
Allow the reaction to cool for 4 minutes before repeating the process. 4 to 5
cycles are generally required on a 650 Watt household microwave. Use of a
microwave with a turntable is recommended
9. Cool the reaction in an ice bath and acidify the resulting solution to a pH of 3.8 using
50% HCl using pH meter
10. Filter the cold solution to remove any residual particulate matter
a. The filtrate is an aqueous solution of lactic acid and NaCl
11. Water, ethanol and NaCl can be removed by rotary evaporation followed by vacuum
filtration
Experiment: Hydrolysis of Post-Consumer Polylactic Acid Waste 4