Carbon Capture From Air

Megan Logue

Is a .1 M or a 1 M solution of sodium hydroxide more effective at extracting and absorbing carbon dioxide from air?

Will carbon dioxide be absorbed more efficiently by sodium hydroxide at 16°C or 32°C?

Problem

The increasing amount of CO2 in the Earth’s atmosphere has the potential to severely harm the environment and affect society.

The purpose of carbon capture is to remove CO2 that would otherwise build up in the atmosphere.

One method of carbon capture is the implementation of artificial trees in the environment. ◦ An artificial tree operates by enabling air to filter through its structure and

removing the air’s CO2 with a sorbent material, such as sodium hydroxide, or NaOH.

The initial pH value of a solution of NaOH will decrease as it captures CO2 from air.

This change in pH can be used to determine the exactly how many molecules of CO2 are extracted from air over a period of time.

Background Research

A solution of NaOH and water can be used to extract CO2 from air. The reaction between a solution of NaOH and CO2 is as follows:

◦ CO2 + H2O = H2CO3

◦ NaOH + H2CO3 = NaHCO3 + H2O

◦ NaHCO3 + NaOH = Na2CO3 + H2O

Overall reaction:

◦ CO2 + 2 NaOH = Na2CO3 + H2O

This indicates that for every two moles of NaOH, one mole of CO2 is extracted from air.

Background Research

As the concentration of the NaOH solution increases, the amount of CO2 absorbed will increase as well.

Also, as the temperature of the system increases, the amount of CO2 extracted from the air will also increase.

Hypothesis

2 L of 1 M solution of NaOH 2 250 mL Erlenmeyer flasks 2 100 mL graduated

cylinders 2 aquarium pumps 2 stirring rods Small weights Water bath Incubator 2 Vernier pH probes 2 Vernier temperature probes

Logger Pro Date Logger Computer Water Paper towels Safety gloves Safety goggles Safety apron Calculator Sink

Materials

A .1 M solution of NaOH and a 1 M solution of NaOH were prepared in separate Erlenmeyer flasks. Both flasks were placed in the water bath set at 20°C.

Separate tubes connected to aquarium pumps, a Vernier temperature probe, and a Vernier pH probe were placed in each flask.

The probes were set to collect samples at increments of 10 minutes over a time period of 24 hours with Logger Pro Data Logger.

After 24 hours, the collected data was recorded. The procedure at 20°C was repeated twice to perform a total of three trials.

Next, an incubator was set at 40°C. The .1 M and 1 M solutions of NaOH were placed in the incubator. An aquarium pump, a Vernier temperature probe, and a Vernier pH probe, were placed in each flask.

Once the temperature of each flask was stable at 40°C, the data collection was promptly started on Logger Pro Data Logger. After 24 hours, the collected data was recorded. The procedure at 40°C was repeated twice to perform a total of three trials.

After each trial was successfully completed, the changes in the pH of the solutions over time were calculated. Mathematical models were used to determine the amount of CO2 molecules extracted from the air and removed by each solution.

The final results of the experiment were compared and analyzed.

Procedure

Independent Variable◦ Temperature◦ Concentration of NaOH solution

Dependent Variable◦ Amount of CO2 removed

Constants◦ Erlenmeyer flasks, aquarium pumps, Vernier

temperature probes, Vernier pH probes, stirring rods, small weights, Logger Pro Data Logger, computer

Variables

Average Decrease in pH

Average Grams of CO2 Removed

Stabilizing temperature

Limited materials

Evaporation of the NaOH solutions over the 24-hour time period

Time restrictions

Sources of Error

At 16°C, the .1 M NaOH solutions were more effective than the 1 M solutions.

At 32°C, the .1 M solutions produced similar results, but the 1 M solutions removed more molecules of CO2. The final results suggested that the 1 M solutions were more effective at 32°C.

This refutes the hypothesis that the CO2 extracted would increase as the concentration of the NaOH solution increased.

It was also hypothesized that the CO2 extracted would increase as the temperature of the system increased. This was rejected for the .1 M solutions but accepted for the 1 M solutions.

Lower concentrations of NaOH are likely to be more effective at cooler temperatures, and greater concentrations of NaOH at warmer temperatures.

Further Research◦ Cost-effectiveness, carbon disposal and storage, different concentrations of NaOH solutions

Conclusion

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Lackner, K. S., Grimes, P., & Ziock, H. (n.d.). Capturing Carbon Dioxide From Air. Retrieved from National Energy Technology Laboratory website: http://www.netl.doe.gov////_seq/.pdf

Lenntech Index. (2009). Retrieved October 23, 2011, from Lenntech website: http://www.lenntech.com/.htm

Ophardt, C. E. (2003). Virtual ChemBook. Retrieved October 22, 2011, from Elmherst College website: http://www.elmhurst.edu/~chm//.html

Works Cited