Spectrophotometry
Spectrophotometry was used in the lab to determine whether non-magnetized zeolite, magnetized zeolite, or charcoal was the more effective sequestration agent for Procion Red Dye. A calibration curve was created with the known concentrations and the absorbances of the Procion Red Dye dilutions at λmax. The slope of the calibration curve was used to determine the concentration of the analytes. As a result, charcoal was shown to be the more effective sequestration agent.
Introduction PAHs, polycyclic aromatic hydrocarbons, are organic compounds that are toxic to the environment. They are inevitably produced from the incomplete combustion of gasoline or coal that originates in industrial and agricultural processes1. PAHs are also water pollutants and may be found in water supplies across the United States2. Research conducted on laboratory animals exposed to low levels of PAHs have shown that the animals commonly develop various types of cancer and other harmful health effects. The …show more content…
use of charcoal as a sequestration agent for PAHs is a common method used by companies3. The purpose of this lab was to design an experiment that tested whether charcoal’s, magnetized zeolite’s, or non-magnetized zeolite’s absorbency of PAHs was more effective.
Materials and Methods The synthesis of zeolite was first. A split cork, three-prong clamp, and ring stand with a hot plate on top were set up to hold a temperature probe. 50.0 mL of 3.0 M NaOH and a magnetic stir bar was placed into a 250 mL beaker. An analytical balance was used to weigh out 3.7529 g of NaAlO2·5H2O and 2.6543 g Na2SiO3·5H2O. The beaker was placed onto the hot plate and the NaAlO2·5H2O was added into the beaker, the solution was stirred until the NaAlO2·5H2O dissolved. As the solid dissolved, a 150 mL beaker that contained 50 mL distilled water was heated on another hot plate. When the distilled water solution boiled the Na2SiO3·5H2O was added. Both solutions were gently boiled and stirred. Tongs were used to transfer the content of the Na2SiO3·5H2O solution into the NaAlO2·5H2O solution. A temperature of 90°C was held constant for an hour. The solution was then cooled for 5 minutes, and equally dispensed into two centrifuge tubes. The centrifuge tubes were placed into a centrifuge and centrifuged for 10 minutes at 5000 rpm. The centrifuge tubes were decanted and the solids were placed into a container with a spatula. Magnetized zeolite was synthesized with nearly the same procedure. The only difference was that 0.7800 g FeCl3 and 0.3900 g FeSO4·7H2O were added, stirred, and dissolved in the beaker while it was heated at 90°C for an hour. Next, a series of three dilutions were made with the 0.05 mM Procion Red Dye stock solution. The concentrations of the dilutions were: 75%, 50%, and 25%. The dilution process for the 75% concentration dilution, consisted of the transfer of 7.50 mL of the Procion Red Dye stock solution with a volumetric pipette into a 10.0 mL volumetric flask. Distilled water was then added to the volumetric flask until it reached the 10.0 mL mark, which caused the solution to have a concentration of 0.0375 mM of Procion Red Dye. The next two dilutions were made with the same process, except with 5.00 mL and 2.50 mL of the Procion Red Dye stock solution respectively. They had concentrations of 0.0250 mM and 0.0125 mM. Four cuvettes were each filled with the 100%, 75%, 50%, and 25% dilutions. An extra cuvette was filled with distilled water to serve as the blank solution. The cuvettes were then ran through a spectrophotometer and a calibration curve for the red dye dilutions was collected. Finally, an analytical balance was used again to weigh out 0.1001 g of non-magnetized zeolite, 0.1000 g of magnetized zeolite, and 0.1002 g of charcoal. Then 10.0 mL of the Procion Red Dye stock solution was distributed into 3 separate beakers. In each of the beakers, the non-magnetized zeolite, magnetized zeolite, and charcoal were added. The beakers were stirred for 10 minutes with a magnetic stir bar and stir plate. The solutions were poured into their own centrifuge tube and placed into the centrifuge. Three more centrifuge tubes were filled with distilled water and put into the centrifuge to balance it. The solutions were centrifuged for 10 minutes at 5000 rpm. Once the centrifuge was done, the solids in the centrifuge tubes were disposed of and each of the liquids were poured into a cuvette. The cuvettes were ran through a spectrophotometer and a calibration curve was acquired.
In figure 1, the three dilutions and stock solution of Procion Red Dye were ran through the spectrophotometer. The λmax is shown on the plot, and it was determined by the data points that were located at the peak of each dilution. The region where the absorbance is the highest is the λmax point, which was 536.7 nm. Furthermore, Appendix 3 of the lab manual stated that the λmax of procion red dye is in the range of 538 +/- 3 nm3. The calibration curve in Figure 2 was made from the concentrations and absorbances of the dilutions and stock solution of Procion Red Dye at λmax from Figure 1. This graph was used to determine a variable in Beer’s Law equation, Ɛ. Beer’s Law equation is A = Ɛbc, where A represents the absorbance, Ɛ is molar absorptivity, b is path length, and c is concentration. In the graph, the equation is A = 13.802c since the path length is 1 cm. Therefore, the molar absorptivity is 13.802 mM-1·cm-1 or 13802 M-
Figure 3 helped correct the measured absorbance. In order to correct the absorbance, the absorbance in the region where the slope was flat must be subtracted from the absorbance at the λmax. This is due to the fact that a flat line on the graph represents a large change in concentration or in similar terms, a large amount of Procion Red Dye removed. The wavelength where the slope was flat for each substance was at 675.2 nm. Then Beer’s Law equation, A = 13802c was be used to obtain the remainder of Procion Red Dye concentration. The calculations of the data are displayed in Table 1.
Table 2 determines which analyte is the more effective sequestration agent of PAHs through a series of calculations. The first step is to compute the initial moles of Procion Red Dye used for each substance. Next, the final moles of Procion Red Dye is calculated with the volume obtained from the solution of the substance that was centrifuged. The final moles of Procion Red Dye is subtracted from the intial moles of Procion Red Dye to obtain the moles of Procion Red Dye removed. Finally, the moles of Procion Red Dye removed is divided by the grams of the substance that was initially dissolved in the 10 mL of Procion Red Dye solution. Therefore, charcoal is the more effective sequestration agent since it removed 4.93 x 10-6 moles of Procion Red Dye/g charcoal. Magnetized zeolite and non-magnetized zeolite removed 3.36 x 10-6 moles of Procion Red Dye/g magnetized zeolite and 2.67 x 10-6 moles of Procion Red Dye removed/g non-magnetized zeolite which is less than the amount of moles of Procion Red Dye that charcoal eradicated. There are three different parameters that could be used to compare the magnetized and non-magnetized zeolites to charcoal.
The first parameter is absorbance. By experimentation, it is apparent that charcoal is more effective in the area of adsorption than both of the zeolites. The second parameter is the cost of the sequestration agent. There are several methods used to produce zeolites since they are made for commercial use. These various methods are able to synthesize large quantities of zeolites at low costs. The third parameter is the rate of production. The production of charcoal requires a delicate process, whereas zeolite can be synthesized easily. The Procion Red dye was a suitable PAH model, because the structure of a PAH and Procion Red Dye both contain benzene rings. Since both compounds have similar structures they both can be affected by intercalation from charcoal or zeolite. Intercalation is a process where a sequestration agent, such as charcoal, can adsorb PAH
molecules.
There are various sources of error that could have occurred with the data collected. The absorbance values could be deemed inaccurate if there were particles of the substances in the cuvettes when they were ran through the spectrophotometer. Another error could have been the spectrophotometer itself; the spectrophotometer could have reported imprecise readings or the cuvette could have had fingerprints on its exterior.
Conclusion The purpose of this experiment was to compare non-magnetized zeolite, magnetized zeolite, and charcoal amongst one another to determine which substance was the more effective adsorber of PAH. Accordingly, charcoal was found to contain the highest amount of moles of Procion Red Dye removed/g of charcoal than the other two substances as shown in Table 2. All in all, the experiment was a success. All of the substances adsorbed the model PAH and charcoal was proven to be the more effective sequestration agent.
Introduction PAHs, polycyclic aromatic hydrocarbons, are organic compounds that are toxic to the environment. They are inevitably produced from the incomplete combustion of gasoline or coal that originates in industrial and agricultural processes1. PAHs are also water pollutants and may be found in water supplies across the United States2. Research conducted on laboratory animals exposed to low levels of PAHs have shown that the animals commonly develop various types of cancer and other harmful health effects. The …show more content…
use of charcoal as a sequestration agent for PAHs is a common method used by companies3. The purpose of this lab was to design an experiment that tested whether charcoal’s, magnetized zeolite’s, or non-magnetized zeolite’s absorbency of PAHs was more effective.
Materials and Methods The synthesis of zeolite was first. A split cork, three-prong clamp, and ring stand with a hot plate on top were set up to hold a temperature probe. 50.0 mL of 3.0 M NaOH and a magnetic stir bar was placed into a 250 mL beaker. An analytical balance was used to weigh out 3.7529 g of NaAlO2·5H2O and 2.6543 g Na2SiO3·5H2O. The beaker was placed onto the hot plate and the NaAlO2·5H2O was added into the beaker, the solution was stirred until the NaAlO2·5H2O dissolved. As the solid dissolved, a 150 mL beaker that contained 50 mL distilled water was heated on another hot plate. When the distilled water solution boiled the Na2SiO3·5H2O was added. Both solutions were gently boiled and stirred. Tongs were used to transfer the content of the Na2SiO3·5H2O solution into the NaAlO2·5H2O solution. A temperature of 90°C was held constant for an hour. The solution was then cooled for 5 minutes, and equally dispensed into two centrifuge tubes. The centrifuge tubes were placed into a centrifuge and centrifuged for 10 minutes at 5000 rpm. The centrifuge tubes were decanted and the solids were placed into a container with a spatula. Magnetized zeolite was synthesized with nearly the same procedure. The only difference was that 0.7800 g FeCl3 and 0.3900 g FeSO4·7H2O were added, stirred, and dissolved in the beaker while it was heated at 90°C for an hour. Next, a series of three dilutions were made with the 0.05 mM Procion Red Dye stock solution. The concentrations of the dilutions were: 75%, 50%, and 25%. The dilution process for the 75% concentration dilution, consisted of the transfer of 7.50 mL of the Procion Red Dye stock solution with a volumetric pipette into a 10.0 mL volumetric flask. Distilled water was then added to the volumetric flask until it reached the 10.0 mL mark, which caused the solution to have a concentration of 0.0375 mM of Procion Red Dye. The next two dilutions were made with the same process, except with 5.00 mL and 2.50 mL of the Procion Red Dye stock solution respectively. They had concentrations of 0.0250 mM and 0.0125 mM. Four cuvettes were each filled with the 100%, 75%, 50%, and 25% dilutions. An extra cuvette was filled with distilled water to serve as the blank solution. The cuvettes were then ran through a spectrophotometer and a calibration curve for the red dye dilutions was collected. Finally, an analytical balance was used again to weigh out 0.1001 g of non-magnetized zeolite, 0.1000 g of magnetized zeolite, and 0.1002 g of charcoal. Then 10.0 mL of the Procion Red Dye stock solution was distributed into 3 separate beakers. In each of the beakers, the non-magnetized zeolite, magnetized zeolite, and charcoal were added. The beakers were stirred for 10 minutes with a magnetic stir bar and stir plate. The solutions were poured into their own centrifuge tube and placed into the centrifuge. Three more centrifuge tubes were filled with distilled water and put into the centrifuge to balance it. The solutions were centrifuged for 10 minutes at 5000 rpm. Once the centrifuge was done, the solids in the centrifuge tubes were disposed of and each of the liquids were poured into a cuvette. The cuvettes were ran through a spectrophotometer and a calibration curve was acquired.
In figure 1, the three dilutions and stock solution of Procion Red Dye were ran through the spectrophotometer. The λmax is shown on the plot, and it was determined by the data points that were located at the peak of each dilution. The region where the absorbance is the highest is the λmax point, which was 536.7 nm. Furthermore, Appendix 3 of the lab manual stated that the λmax of procion red dye is in the range of 538 +/- 3 nm3. The calibration curve in Figure 2 was made from the concentrations and absorbances of the dilutions and stock solution of Procion Red Dye at λmax from Figure 1. This graph was used to determine a variable in Beer’s Law equation, Ɛ. Beer’s Law equation is A = Ɛbc, where A represents the absorbance, Ɛ is molar absorptivity, b is path length, and c is concentration. In the graph, the equation is A = 13.802c since the path length is 1 cm. Therefore, the molar absorptivity is 13.802 mM-1·cm-1 or 13802 M-
Figure 3 helped correct the measured absorbance. In order to correct the absorbance, the absorbance in the region where the slope was flat must be subtracted from the absorbance at the λmax. This is due to the fact that a flat line on the graph represents a large change in concentration or in similar terms, a large amount of Procion Red Dye removed. The wavelength where the slope was flat for each substance was at 675.2 nm. Then Beer’s Law equation, A = 13802c was be used to obtain the remainder of Procion Red Dye concentration. The calculations of the data are displayed in Table 1.
Table 2 determines which analyte is the more effective sequestration agent of PAHs through a series of calculations. The first step is to compute the initial moles of Procion Red Dye used for each substance. Next, the final moles of Procion Red Dye is calculated with the volume obtained from the solution of the substance that was centrifuged. The final moles of Procion Red Dye is subtracted from the intial moles of Procion Red Dye to obtain the moles of Procion Red Dye removed. Finally, the moles of Procion Red Dye removed is divided by the grams of the substance that was initially dissolved in the 10 mL of Procion Red Dye solution. Therefore, charcoal is the more effective sequestration agent since it removed 4.93 x 10-6 moles of Procion Red Dye/g charcoal. Magnetized zeolite and non-magnetized zeolite removed 3.36 x 10-6 moles of Procion Red Dye/g magnetized zeolite and 2.67 x 10-6 moles of Procion Red Dye removed/g non-magnetized zeolite which is less than the amount of moles of Procion Red Dye that charcoal eradicated. There are three different parameters that could be used to compare the magnetized and non-magnetized zeolites to charcoal.
The first parameter is absorbance. By experimentation, it is apparent that charcoal is more effective in the area of adsorption than both of the zeolites. The second parameter is the cost of the sequestration agent. There are several methods used to produce zeolites since they are made for commercial use. These various methods are able to synthesize large quantities of zeolites at low costs. The third parameter is the rate of production. The production of charcoal requires a delicate process, whereas zeolite can be synthesized easily. The Procion Red dye was a suitable PAH model, because the structure of a PAH and Procion Red Dye both contain benzene rings. Since both compounds have similar structures they both can be affected by intercalation from charcoal or zeolite. Intercalation is a process where a sequestration agent, such as charcoal, can adsorb PAH
molecules.
There are various sources of error that could have occurred with the data collected. The absorbance values could be deemed inaccurate if there were particles of the substances in the cuvettes when they were ran through the spectrophotometer. Another error could have been the spectrophotometer itself; the spectrophotometer could have reported imprecise readings or the cuvette could have had fingerprints on its exterior.
Conclusion The purpose of this experiment was to compare non-magnetized zeolite, magnetized zeolite, and charcoal amongst one another to determine which substance was the more effective adsorber of PAH. Accordingly, charcoal was found to contain the highest amount of moles of Procion Red Dye removed/g of charcoal than the other two substances as shown in Table 2. All in all, the experiment was a success. All of the substances adsorbed the model PAH and charcoal was proven to be the more effective sequestration agent.