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Safety Procedures
Safety Procedures
Please be aware of any potential hazards prior to operating any experiment. Methylene blue is a potent textile dye that will stain clothing (and skin, temporarily), so handle with caution and ensure that all connections are properly secure. Hydrogen peroxide is limited to 6% solution and may cause skin irritation. In the even of exposure, run water over the affected areas, contact lab personnel, and if additional medical attention is required use the emergency protocols at the exits to contact EH&S or dial 911. DO NOT DUMP ANY WASTE DOWN THE SINK!
Name
Name
Formula
Formula
Hazard
Hazard
Supplier
Supplier
SKU
SKU
water
H2O
n/a
n/a
hydrogen peroxide (6%)
H2O2
any
n/a
methylene blue
C₁₆H₁₈N₃SCl
Sigma-Aldrich
titanium (IV) oxide
TiO₂
Alfa Aesar
Other Safety Concerns:
Other Safety Concerns:
Wear a lab coat and safety glasses at all times
Beware of pump speed: leaks may occur at high flow rates
If used, keep the centrifuge balanced.
Never fully submerge the conductivity probe in the tank; submerge only the metal tip.
Programs, Equipment, and Instruments
Programs, Equipment, and Instruments
UV reactor
Pump with speed controller
Spectrophotometer
Centrifuge (if TiO₂ present in solution)
Balance
Objectives
Objectives
Create a calibration curve for spectrophotometer.
Determine the apparent rate law for the photocatalytic degradation of methylene blue.
Tips
Tips
Plan your experiments before coming to the lab.
The spectrophotometer has a limited range of about 10 ppm methylene blue.
Make enough solution (~500-1000 mL) so that you can sample regularly.
High flow rates can break down the catalyst (TiO2) pellets, which will cause the solution to be slightly cloudy. This can cause erroneous readings in the spectrophotometer.
A typical reaction "run" takes about 45 min. You'll still need to work efficiently to finish an experimental run in the allotted time.
You can produce a calibration curve while simultaneously running the reactor as long as all absorbance measurements are made at the same wavelength.
Don't try to derive a full mechanism or its coefficients. Focus on the apparent (observed) rate law.
NOTE: You must determine what weight of methylene blue is necessary to produce 1L of a 10 ppm solution (by mass). You are not allowed to start this experiment until you confirm that number with a TA, Professor, or James.
References
References
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