Lee Wonjae, Extended Essay

Wonjae Lee 003562–045 What is the effect of pH on the adsorption of caffeine by activated carbon?

International Baccalaureate

What is the effect of pH on the adsorption of caffeine by activated carbon?

Extended Essay – Chemistry

QUEENSLAND ACADEMY FOR HEALTH SCIENCES

Wonjae Lee

Date: 12/7/2013

Candidate number: 003562–045

Session number: November 2013

Word count: 3979

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Contents

Abstract

Introduction

Method

Results and Analysis

Results

Analysis

Conclusion

Evaluation

General evaluation

Evaluation of sources

Unresolved questions and direction for further investigation

Bibliography

Appendices

Appendix I: Apparatus

Appendix II: Raw Quantitative Data

Appendix III: Propagated uncertainty

Appendix IV: Information about chemicals

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Abstract

Caffeine is undoubtedly the most consumed and used drug in the world while the activated carbon is renowned for its applications in removal of undesirable organic chemicals. This experiment aims to investigate the effect of solvent (water) pH on the adsorption of 0.100g of caffeine onto 0.100g of powdered activated carbon (PAC) after undergoing 25 hour of batch treatment test. The research question that summarises this investigation is: “What is the effect of pH on the adsorption of caffeine by activated carbon?”

Caffeine solutions of were prepared by dissolving No-Doz® tablets (100mg caffeine per tablet) in 50ml of distilled water. The solutions underwent standard batch treatment with powdered activated carbon (PAC) after the manipulation of pH using hydrochloric acid and sodium hydroxide. The liquid-liquid separation technique with ethyl acetate was used separate the caffeine from water. The amount of caffeine separated from the solution via ethyl acetate was measured.

The results indicate that the decaffeination process through PAC is pH dependent process. The percentage removal of Caffeine via PAC was 16% for pH 2; 24% for pH 3; 22% for pH 6.3; 52% for pH 9 and 58% for pH 11. Percentage removal versus pH graph suggested two models: the exponential relationship, or the plateau model at a lower pH (< 6.31). Both models indicate that the adsorption of caffeine onto PAC is significantly higher at a higher pH. The PAC will adsorb the caffeine better from the basic solution then the acidic solution. The result was attributed to the basicity of the caffeine where caffeine deprotonates with the presence of strong base in the solution.

Word count: 266

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IntroductionThe aim of this experiment was to investigate whether the different pH of solution would improve the efficiency of the adsorption of caffeine onto powdered activated carbon (PAC). Hence the research question is: “What is the effect of pH on the adsorption of caffeine onto activated carbon?”

Caffeine

Caffeine (1, 3, 7-trimethylxanthine) is a xanthine alkaloid with three methyl groups attached (see appendix IV). In the room temperature, it forms a bitter tasting clear crystal and is the world’s most consumed and used drug (Shalmashi & Golmohammad 2010, pp. 283-285). It occurs in common food and beverages such as chocolate, coffee, tea and various energy drinks and is commonly used as a central nervous system (CNS) stimulant in the pharmaceutical industry (Silverman, K & Griffiths, R 2001). With increasing abuse of caffeine consumptions in urban society, its effect in human physiology and behaviour is subjected for extensive research. Decaffeinated product, therefore, has attracted significant attraction. For example, Swiss Water® decaffeination process1 is a method which is widely practiced in coffee industry that utilises activated carbon to remove caffeine from coffee bean.

The solubility of caffeine at room temperature (25°C) is approximately 0.105M (1020mg/50ml), therefore 100mg of caffeine will completely dissolve in 50ml (Open Notebook Science Challenge, 2013). According to Spiller (ed.1998, p. 5), caffeine act as a weak base with pKa value of is 14.2 at 19°C therefore reacts with acid. Its basic property is characterised by single nitrogen with lone pair of electron. In the reaction, the caffeine salt is formed which is readily hydrolysed. Spiller (ed.1998, p. 5), also found the evidence of protonated caffeine formation at pH 0. The measured pH is closely related to the solubility of caffeine in the water, typically due to the ionic bond form between water and caffeine to create conjugate salt. With the presence of acid, caffeine will act as a cation (Cammack, J 2012, p. 3) which increases its water solubility. Conversely in the basic solute, caffeine will remain neutral with little polarity.

1 Swiss Water Decaffeinated Coffee Company n.d., Science of Decaffeination, http://www.swisswater.com/trade/the-swiss-water-experience/science-of-decaffeination

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Fig. 1 interaction of caffeine with water – When the caffeine is under acidic condition, because caffeine is basic, it attracts proton (hydrogen) from the environment and attach it to one of the lone pairs of nitrogen 2. (Cammack, J 2012, p. 3)

Adsorption

Bansal & Goyal (2005, p. 8) states that adsorption as the process which occurs “when a solid surface is brought into contact with a liquid or gas.” Due to the surface energy, this contact causes the surface between the solid surface and the gas/liquid to interact, which ultimately causes ions, atoms and molecules (adsorbate) to be attracted to the solid surface (adsorbent), such as activated carbon. This process accumulation of substances onto solid surface is known as adsorption.

Activated carbon

Activated carbon is a versatile adsorbent (Bansal & Goyal 2005) and its adsorptive properties characterised by its mesopores and macropores in the carbon structure. Activated carbon is applied extensively in the field of purification, including the removal of taste, order, colour and other organic and inorganic contaminant from food, waste water and air, while further applications to its use is still building up. In the food processing industry, use of activated carbon is also a safer alternative to the use of harmful chemicals such as chloroform and dichloromethane.

Adsorption isotherms can be described as amount of impurity absorbed from aqueous media by the absorbent such as activated carbon at an adsorptive equilibrium. This adsorptive character is readily affected by the various properties of the target contaminant such as molecular size, structure and mass, solubility and polarity. Experimental condition such as the ionic strength and pH also influences the adsorptive character. Activated carbon involves two types of adsorption: chemical and physical adsorption. Chemical adsorption refers to situation in which the adsorbent and adsorbate shares and exchange electron which creates much stronger bond then physical adsorption which involves van der Waals interaction. László et al. (2007, p. 95) claims that pH of the solvent may modify the adsorptive surface of the activated carbon. Interaction of water organic solute such as caffeine can alter with pH, which may also influence the strength of attraction with activated carbon.

Solvent extraction

2 Cammack, J 2012, Lab 5: Extraction of caffeine from tea, Chemeketa Community Collegehttp://faculty.chemeketa.edu/jcammack/CH241-3B%20Lab/CH241B%20Labs/CH241%205%20Caffeine%20Extraction.pdf[Accessed 28 May 2013]

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Solvent extraction is a common technique which is used to isolate the organic compound present in the targe aqueous media. Ethyl acetate is an organic solvent commonly used as an organic solvent due to its immiscibility with water, less toxic property then other organic solvents and its ability to attract caffeine due to its polarity. Caffeine readily dissolves in ethyl acetate. The solubility of caffeine on ethyl acetate at room temperature (25°C) is approximately 0.041M. 100mg of caffeine will therefore dissolve in 15ml of ethyl acetate (Open Notebook Science Challenge, 2013) which makes ethyl acetate a good organic solvent when isolating caffeine from its aqueous media. Caffeine, however, is much more soluble in water, therefore addition of base in the caffeine solution or the increase in the solvent pH will improve the extraction due to change in solubility. Addition of salt such as sodium chloride (NaOH) may also increase the efficiency of extraction as water is more attracted to salt then caffeine (Cammack, J 2012, p. 3). Since ethyl acetate has lower density then water, the ethyl acetate layer will be formed above the water.

MethodPreparation of caffeine solutionThe caffeine solution was prepared carefully using the appropriate apparatus and a method under a room temperature (25°C). On a single 100ml beaker, add approximately 40ml of distilled water and then drop one No-Doz® Caffeine tablet (100mg of caffeine). The 100ml beaker was left untouched until the tablet completely dissociated3. Undissolved solids were then filtered out onto a 50ml volumetric flask using a filter paper and a funnel. The distilled water was carefully added to the volumetric flask to 50ml margin. During this process distilled water was added through the filter paper and the funnel which was used to filter in order to flush down any caffeine solution remaining on the apparatus. Cap of the volumetric flask was closed to minimise the interaction between air and caffeine solution made. Repeat the above steps to prepare total of 18 identical caffeine solutions.

Manipulating pH Initially, pH probe was calibrated using the pH 7 and pH 4 buffers. Two pH titration stations were set up using the burette clamp and a retort stand: one for 1M hydrochloric acid solution (HCl) and the other for 1% sodium hydroxide solution (NaOH). The retort clamp was also used to hold the pH probe in a stationary position during the titration. The caffeine solution was first transferred into a 100ml beaker and was placed below the burette. pH probe was then placed inside the beaker so that the sensor of the probe is completely submerged inside the caffeine solution4. After the pH probe reached equilibrium on its measurement, add drops of either HCl or NaOH until desired pH has been reached (pH 2, 3, 9 and 11).

PAC batch treatmentPAC batch treatment (Norit Activated Carbon, 2001) refers to isotherm test where a certain amount of PAC is dosed to a solution to investigate the change in the mass of the target 3 May take up to 1 hour4 100ml beaker was swirled gently after every drop of HCl or NaOH

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molecule. Approximately 100mg of powdered activated carbon (PAC) was obtained through measurement using the electronic balance (±0.001g). The activated carbon was then added to the caffeine solution which has already undergone pH moderation as written in the “Manipulating pH” section. A stir bar was dropped gently into the beaker which was then placed on the magnetic stirrer and was set the medium stirring speed5. Watch glass was placed on top of each beaker to minimise its interaction of solution with air. The stirring underwent for 24 hours. Upon completing of stirring, the PAC was then filtered out from the caffeine solution using double layer of laboratory filter paper. This was done to minimise the amount of PAC which penetrate through the filter paper.

Controlling pHIn order to control the pH of the solvent, following procedures were performed before undergoing liquid solvent separation:

1. Additional HCl solution (1M) was added to caffeine solution that the total amount of HCl solution present in the solution is exactly 0.75ml. This means that if the solution already contained HCl solution due to “Manipulating pH” procedure, the amount of HCl added was 0.75ml subtracted by the amount HCl solution already present in the solution6.

2. The same rule was applied for NaOH solution as HCl so that the amount of NaOH solution present in the caffeine solution was always 6ml. This was done to maintain pH 11 for all trials to increase the effectiveness of liquid-liquid separation.

Liquid-liquid separationThe filtered caffeine solution was poured into a separatory funnel. 15ml of ethyl acetate was then added into a same separatory funnel using the 10ml graduated pipette. The separatory funnel was inverted 3 times and then the stop cock was opened to release the gas. This was repeated 4 times. The solution was then settled for 15 minute, and then the organic solvent (ethyl acetate) layer (upper layer) was collected onto 100ml beaker which its mass has been measured prior to this event. The beaker was placed in a water bath (80°C) to speed up the evaporation of ethyl acetate. When the ethyl acetate evaporated completely, clear and dry caffeine crystal complexes were formed. The mass of the beaker was measured again and was recorded. This procedure was repeated for all 17 other solutions.

(See appendix I for the full list of apparatus and materials used in the experiment)

5 6 stirring station was set up at once6 With 0.75ml HCl present in the caffeine solution, the pH is approximately 4.00

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Results and Analysis

Results

The mass of caffeine collected after the liquid-liquid separation process was determined by finding the difference between the mass of the beaker when it was empty and after the caffeine crystal is formed (see appendix 2 for Raw Data).

Table 1: Table of yields of caffeine after PAC batch treatment procedure (0.100 ±0.001g of PAC) for different pH

pH ±0.01Mass of Caffeine collected (trial 1)

/g ±0.002

Mass of Caffeine collected (trial 2)

/g ±0.002


/g ±0.002

Average mass of caffeine collected

/g ±0.0022.11 0.013 0.014 0.015 0.0143.10 0.013 0.014 0.011 0.0136.31 0.012 0.012 0.015 0.0139.14 0.008 0.009 0.007 0.00811.03 0.008 0.005 0.008 0.007

Table 2: Control for comparison: Table of yields of caffeine without PAC batch treatment procedure (0.100 ±0.001g of PAC) without the manipulation of pH

pH ±0.01Mass of Caffeine collected (trial 1)

/g ±0.002


/g ±0.002


/g ±0.002

Average mass of caffeine collected

/g ±0.0026.17 0.015 0.019 0.016 0.017

It is important to analyse the effectiveness of liquid-liquid separation of caffeine in an aqueous state using ethyl acetate. Single caffeine tablet contained 100mg of caffeine, therefore the efficiency of the ethyl acetate liquid separation of caffeine was found in percentage.

Efficiency=100× mass of caffeine collected0.100 g

¿100 × 0.0170.100

¿17%

Therefore ethyl acetate can absorb 17% of caffeine present in 50ml of distilled water containing 0.100g of caffeine at a standard condition7. Therefore in order to fully understand the effectiveness PAC on caffeine removal, the percentage removal of caffeine was found and compared to observe the effect of pH on adsorption of caffeine onto PAC.

7 Temperature of 25°C, atmospheric pressure and no manipulation of pH

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Percentage removal of caffeine is defined as:

100 × control for comparison−averagemass of caffeinecollectedcontrol for comparison

*Control for comparison is always 0.017g

For example, if this is applied to pH 2.11, the percentage removal of caffeine is determined as:

100 × 0.017−0.0130.017

≈ 16%**NOTE: the stated value of “control for comparison” or the “average mass of caffeine collected” is only an estimate up to three decimal places. Exact value may differ due to averaging.

Table 3: Percentage removal of caffeine after PAC batch treatment procedure for different pH

pH ±0.01Average mass of

caffeine collected /g ±0.002

Average mass of caffeine removed from

0.017g /g ±0.004

Percentage removal of caffeine via PAC (%)

2.11 0.014 0.003 163.10 0.013 0.004 246.31 0.013 0.004 229.14 0.008 0.009 52

11.03 0.007 0.010 58

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The pH can be plotted against the percentage removal of caffeine via PAC on a scatter gram to investigate the interrelationship between each other and independent and dependent variable.

1 2 3 4 5 6 7 8 9 10 11 12 13 140

10

20

30

40

50

60

70

80

90

100

Graph 1: Caffeine removed from the water via adsorption onto PAC with varying pH

pH/ ±0.01

Caf

fein

e re

mov

ed /%

The above graph establishes exponential relationship between pH and the percentage of caffeine removed via adsorption onto PAC. In the graph, it is evident that with increasing pH of the solution increases the amount caffeine adsorbed onto 0.100g of PAC when exposed for 24 hours.

Analysis

Uncertainties

The propagated uncertainty of the average value of both solvent pH and the caffeine removed (%) was found and was used for the error bars on graph 1 instead of instrumental error for. The uncertainty of weighing scale was particularly high due to small quantity of caffeine extracted and low precision of the scale. The table 3 shows the uncertainty of the average mass of caffeine removed which was ±0.004g which is extremely high compared to the actual measurement (e.g. 0.003g).

See appendix III for more information on the propagated uncertainty

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General discussion of trend

Instead of the mass of caffeine removed from water, the in percentage removal was plotted against pH as it provides information on effectiveness of the use of activated carbon. Percentage removal indicates the amount of caffeine removed relative to the initial amount of caffeine present in the solution. The increasing percentage removal also suggests that more caffeine is adsorbed into same amount of activated carbon, which proposes increase in the efficiency of PAC.

From Graph 1, it can be seen that while increasing the pH may increase the adsorption of caffeine onto PAC, however it is difficult to conclude whether decreasing the pH would reduce the adsorption of caffeine. There are two suggested interpretations of results from the graph. Firstly, if the exponential relationship is true, then the percentage removal of caffeine via PAC and the rate of increase of the removal augment with increasing pH, therefore decreasing pH reduce the percentage removal of caffeine but considerably at a much slower pace.

Secondly, the graph may also be interpreted as a curve with one plateau reaching the minimum at lower (acidic) pH (< pH 6.31). The data from pH 2.11, 3.10 and 6.31 shares extremely similar results (0.014, 0.013 and 0.013 respectively) where all data falls into an error bar. The percentage removal of caffeine is only slightly higher for pH 3.10 then pH 6.31, which is a signal that the decrease in pH after a specific pH may have no influence on the efficiency of adsorption of caffeine onto activated carbon. This indicates that the percentage removal of caffeine plateaus and move towards its minimum as pH decreases. Considering the pKa of caffeine which is 14.2 at 19°C (ed.1998, p. 5) most caffeine maybe already protonated due to acidic condition therefore further decrease in pH have lesser effect on the solution and solubility of caffeine. According to the graph, the equivalence point may exist between pH 6.31 and 9.14 where the removal of caffeine is at its average efficiency. At a higher pH (pH 9 and pH 11) shares rather similar results as well (52% and 58% respectively) and therefore it can be suggested that the percentage removal of caffeine also plateaus and move towards its maximum as pH increases. The explanation is similar to the one on acidic pH this as most caffeine maybe deprotonated at a high pH, however there is lack of data point at a basic pH (> pH 7) to reach this conclusion. The fact that no pH over 14.2 was tested does not give us clear indication as to whether the percentage removal of caffeine is only influenced by the change in solubility due to pH.

In both of the interpretation agree that when the pH of caffeine solution is higher, the percentage removal of caffeine via adsorption onto PAC increases, therefore the decaffeination process will be more effective under basic condition above pH 9.14.

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Conclusion

The results showed that the increase in pH to the basic region (> pH 7) significantly improved the adsorption of caffeine by powdered activated carbon (PAC) after being exposed to PAC for 24 hours; hence answering the research question: “What is the effect of pH on the adsorption of caffeine by activated carbon?”

The percentage removal of Caffeine was 16% for pH 2.11; 24% for pH 3.10; 22% for pH 6.31; 52% for pH 9.14 and 58% for pH 11.03. Graph 1 suggested exponential relationship or a curve with plateau at a lower pH (< 6.31). These relationships suggest that the increasing basicity of solution increases the adsorption of caffeine via PAC, and as the solution becomes more acidic, adsorption decreases only slightly or plateaus to the minimum. This suggests that the adsorption of caffeine most efficient when the pH of the solvent (water) is higher than pH 11.

Evaluation

General evaluation

There were generally a lot more problems during the experiment then predicted. These problems involve both random and systematic errors as well as assumptions which may have impacted the results significantly.

The possible random error was identified in the mass of caffeine isolated and measured. The weighing scale could read up to a milligram while the mass of caffeine extracted was mostly just over or below 10mg, therefore the results was found in either one or two significant figures. After several subtractions of between the results to find the mass of caffeine removed from the solution, the measurement error and the propagated uncertainty increase, while the propagated uncertainty reached 130% for the percentage removal of caffeine at pH 3.10. This random error impacted the precision of the data significantly, which questions whether the results of this experiment are reliable. Nonetheless the solution for this problem is rather simple. It is recommended that more caffeine tablets are used for each caffeine solution (e.g. 2 caffeine tablets per 50ml). This will increase the overall magnitude of the data where more caffeine is adsorbed or extracted, therefore increasing the precision of the data. It is also suggested that the amount PAC and used is increased as well. With 200mg of caffeine per 50ml, 0.200mg of activated carbon should be used to match the mass with the mass of caffeine present in the solution. Another alternative solution is to use much more precise weighing scale to increase precision, possibly the one that can measure down to 0.1mg.

It was extremely difficult to control same stirring speed for all PAC batch treatment test due to inconsistency in the stirring apparatus. Some stirring bar worked much more efficiently while some magnetic stirrer produced much stronger magnetic field. Out of 6 magnetic stirrers which were used in the experiment, one of the magnetic stirrers was exceptionally fast

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even if when the stirring speed was set to low. It is implied that slight difference in the stirring speed may have contributed to the overall lower precision of the results.

Amount of caffeine extracted from liquid-liquid separation using ethyl acetate was much less than which was expected. The use of ethyl acetate which was used as a solvent during the liquid-liquid separation was only 17% efficient from isolating caffeine from its aqueous state. This Ethyl acetate can also be changed for more effective organic solvent. The investigation by Shalmashi (2010, p.283-285) concludes that caffeine is most soluble in chloroform (CHCl3). Caffeine is also extremely soluble in dichloromethane (CH2Cl2) and acetone (CH3COCH3) which any of these three organic solvent can be a perfect and better alternative to ethyl acetate. If the solvent is more soluble, it is possible that more caffeine is extracted from the liquid-liquid separation technique, which will increase the overall precision of the data.

Atomssa and Gholap (2011, p.1-8) have proposed that the concentration of for caffeine present in various solvent including water can be investigated using the UV-vis spectroscopy at ultra violet region. When caffeine is dissolved in water, λmax occurs at 272.8 nm, and using the calibration curve, the concentration of caffeine can be found. This procedure can replace liquid-liquid separation process and provide much more precise measurement of the amount of caffeine present after the filtration.

The way in which the caffeine solutions were prepared has implication which may have influenced the data significantly. Despite the fact that the 50ml volumetric flask in which the caffeine solution was stored was sealed with the glass cap, most of the solution contained small culture of fungi which all had similar visible structure. Its green colour and a shape resembled those of Penicillium expansum, which further research into this area, showed that the particular penicilium called Penicillium commune, is capable of degrading the caffeine (Long, 2013). This systematic error maybe the explanation for the small mass of caffeine (< 0.020g) extracted from liquid-liquid separation procedure for all trials, therefore it was appropriate to use percentage removal of caffeine rather than the mass of caffeine removed. However it is extremely difficult to conclude which direction of problem is caused by the presence of fungi. The culture may be indicating the possible impurities in the caffeine solution such as glucose, which is the common filler in the tablet and main food for fungi. The growth of fungi can be controlled and prevented by simply storing all the caffeine solutions in a laboratory refrigerator, then let the solution reach the room temperature just before the experimentation.

One of the biggest assumptions in the experiment regarding with the caffeine solution was its purity. It was assumed that simple filtration with the standard laboratory filter paper maybe enough to remove all the unnecessary fillers from the caffeine tablet out of the caffeine solution. It is possible that the impurities in the caffeine solution may have interacted with the activated carbon and therefore reducing the overall percentage removal of caffeine due to competitive adsorption. This systematic error may decrease overall accuracy of the results.

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However it is difficult to conclude whether the results were accurate or inaccurate due to absence of literature value which can be compared with.

Evaluation of sources

The sources generally can divide into two categories: primary and secondary sources. Primary sources are considered more reliable, however the secondary sources were only used after examining references mention and see whether the statement is reliable, therefore the uncertainty of using the secondary sources decreased. Books generally conceived more reliable than the webpages, the reliability of the information from the webpage is rather debatable. The use of journal articles was most successful as they are primary sources.

Wide variation of literature value of pKa was found from various sources. The pKa value was taken from a book written by Spiller (ed.1998, p. 5); however it is important to question its validity. It is suggested that prior to the experiment, the pKa value of caffeine should be found through experimentation by creating a pH titration curve, which will provide valid pKa of caffeine to be considered in the introduction and discussion. Investigation into pKa of caffeine and its isoelectric point may also be an interesting approach for a further investigation.

Unresolved questions and direction for further investigation

The lack of data point for the graph 1 left one fundamental question as to what exactly is the relationship between pH and the adsorption of caffeine onto activated carbon. Whether the relationship is one of the two theories suggested (exponential relationship, or the plateau at low pH) or the other relationship. If more results from wide variety of pH are plotted, the relationship between the percentage removal of caffeine and the pH will be more distinct.

Many research in the field of adsorption investigate adsorption isotherms (Bansal & Goyal 2005). Finding the adsorptive isotherms of caffeine on powdered activated carbon may give more useful information. Adsorptive isotherm will provide with adsorption equilibrium of caffeine solution at a specific pressure and temperature, general adsorptive characteristics of caffeine as well as the properties of PAC such as its pores volume, the surface area and the size distribution. Since the properties of PAC that was used in the experiment provided itself with no written physical properties, it will be interesting to investigate the properties of the PAC and perhaps compare with the activated carbon with the different property.

There exists alternative ways of investigating the effectiveness of adsorption of caffeine dissolved in water onto activated carbon. Granular activated carbon (GAC), characterised by bigger carbon particle size compared to PAC, is also commonly used in a waste water treatment due to its high surface area and volume ratio (Sotelo et al. 2012). Sotelo et al. (2012, p.967-974) investigated the removal of caffeine in fixed bed column design utilising GAC which is also an interesting and reliable method of investigating the adsorption of caffeine onto activated carbon.

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The question as to whether the caffeine crystals extracted using the liquid-liquid separation is pure remains unresolved. It had been assumed in the experiment that the caffeine extracted using the liquid-liquid separation was pure caffeine crystals and it would be interesting to investigate the purity of the content. The purity can be examined using a melting point determination test which is designed specifically to investigate the purity of crystals such as caffeine8, although the difficulties lies in caffeine’s ability to sublime at an atmospheric pressure. Alternatively, temperature in which sublimation of caffeine occurs can be found to detect the purity of the solution. Further research discovered that Moyé (1972, p.194) have developed a design of extracting mostly pure caffeine crystals from No-Doz® tablet. The author also suggests the recrystallization of caffeine to extract pure caffeine from the mixture crude caffeine and benzene using Büchner funnels.

With more advanced equipment such as Büchner funnels and potentially dangerous chemical reagents such as chloroform and dichloromethane which is not provided in school laboratory, it is possible to explore further and develop better method for the experiment. The concept of this experiment is no doubt worthy of further investigation with more access to advanced equipment.

Word count: 3979

8 The melting point of caffeine is 238°C (K) see appendix 4

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Bibliography

Atomssa, T & Gholap, A 2011, Characterization of caffeine and determination of caffeine in tea leaves using UV-visible spectrometer, African journal of pure and applied chemistry, Vol. 5, no. 1, p. 1-8.

Bansal, R & Goyal, M 2005, Activated Carbon Adsorption, CRC press Francis & Taylor group, United State of America

Cammack, J 2012, Lab 5: Extraction of caffeine from tea, Chemeketa Community Collegehttp://faculty.chemeketa.edu/jcammack/CH241-3B%20Lab/CH241B%20Labs/CH241%205%20Caffeine%20Extraction.pdf [Accessed 28 May 2013]

Dews, P 1982, Caffeine, Annual Review of Nutrition, Vol. 2, p. 323-341

Guetta, D 2006, Acidity, Basicity and pKa, Columbia University, http://www.columbia.edu/~crg2133/Files/CambridgeIA/Chemistry/AcidityBasicitykPa.pdf[Accessed 5 May 2013]

László, K, Tombácz, E & Novák, C 2007, pH-dependent adsorption and desorption of phenol and aniline on basic activated carbon, Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 306, no. 1-3, p. 95-101

Long, R 2013, Caffeine Pathway Map (fungal), 19 April, University of Minnesota, http://umbbd.ethz.ch/caf2/caf2_map.html[Accessed 5 May 2013]

Moyé, A 1972, Extraction of Caffeine, Journal of chemical education, vol. 49, no. 3, p. 194

Norit Activated Carbon 2001, Measuring adsorptive capacity of powdered activated carbon, Carbot Corp.http://www.norit.com/files/documents/Isotherm_Test_rev2.pdf [Accessed 17 November 2012]

Norit Activated Carbon 2001, Granular activated carbon evaluation, Carbot Corp.http://www.norit.com/files/documents/Pilot_Col_Testing_rev2.pdf [Accessed 17 November 2012]

Open Notebook Science Challenge 2013, Solubility of caffeine in organic solvents, http://lxsrv7.oru.edu/~alang/onsc/solubility/allsolvents.php?solute=caffeine[Accessed 5 May 2013]

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Penn State University Department of Chemistry, 2006, Liquid/Liquid Extraction, Penn State department of Chemistry, Pennsylvania, http://courses.chem.psu.edu/chem36/Experiments/PDF%27s_for_techniques/Liquid_Liquid.pdf [Accessed 11 July 2013]

Silverman, K & Griffiths, R 2001, Caffeine, Encyclopedia of Drugs, Alcohol, and Addictive Behavior second edition, Vol.1, ed. Carson, R, Macmillan Reference USA, New York, pp. 209 – 215

Sotelo, J, Rodríguez, A, Álvarez, S & García J 2012 Removal of caffeine and diclofenac on activated carbon in fixed bed column, Chemical engineering research and design, vol. 90, no. 7, pp. 967-974

Spiller, G (ed.) 1998, Caffeine, CRC Press, United State of America

Swiss Water Decaffeinated Coffee Company n.d., Science of Decaffeination, Swiss water decaf, http://www.swisswater.com/trade/the-swiss-water-experience/science-of-decaffeination [Accessed 16 November 2012]

Ye, J, Liang, Y, Jin, J, Liang, H , Du, Y , Lu, J , Ye, Q & Lin, C 2007, Preparation of Partially Decaffeinated Instant Green Tea, Journal of agriculture and food chemistry, vol. 55, no. 9, p. 3498-3502

Sigma-Aldrich 1999, Caffeine (anhydrous), Product information, Sigma-Aldrich, Missourihttp://www.sigmaaldrich.com/etc/medialib/docs/Sigma-Aldrich/Product_Information_Sheet/c0750pis.Par.0001.File.tmp/c0750pis.pdf [Accessed 9 June2013]

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Appendix I

ApparatusList of equipment used in the experiment:

Glassware(36) Beaker (100ml)(18) Volumetric flask (50 ±0.2ml)(6) Watch glass(1) Glass Funnel(1) Measuring cylinder (100 ±0.10ml)(1) Separatory funnel (100ml)(1) Graduated pipette (10 ±0.1ml)(1) Stirring rod(2) Burette (50 ±0.05ml) with a stopcock

Electronic supply(6) Hot plate/magnetic stirrer(6) Stir bar(1) Water bath(1) Pasco® pH probe/laptop(1) Weighing scale

Other equipment(33) Standard laboratory filtration paper(3) Retort stand/boss head/retort clamp(2) Burette clamp(2) Spatula

Reagents and Chemicals No-Doz ® Caffeine tablet

100mg caffeine per tabletPowdered Activated Carbon – PAC

Atomic weight: 12.01Impurities: Water ≤ 4%

Ash ≤ 13%Particle size: 44μm 9

Ethyl Acetate (CH3COOCH2CH3)Hydrochloric acid (HCl), 1MSodium hydroxide (NaOH), 1%Distilled water9 Generally accepted value proposed by Bansal & Goyal 2005

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Appendix II

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Raw

dataThe experim

ental recording of data is written here:

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Appendix III

Propagated uncertainty table

Table 3′: absolute and percentage uncertainty - Percentage removal of caffeine after PAC batch treatment procedure for different pH

pH ±0.01Average mass of

caffeine collected /g ±0.002

Average mass of caffeine removed from

0.017g /g ±0.004

Percentage removal of caffeine via PAC (%)

2.11 ±0.02 (1%) ±0.001 (7%) ±0.003 (82%) (82%)3.10 ±0.05 (1%) ±0.002 (12%) ±0.004 (130%) (130%)6.31 ±0.35 (6%) ±0.002 (12%) ±0.005 (88%) (88%)9.14 ±0.04 (0%) ±0.001 (12%) ±0.004 (34%) (34%)11.03 ±0.03 (0%) ±0.002 (21%) ±0.004 (36%) (36%)

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Appendix IV

Information about chemicals

Caffeine

(Silverman & Griffiths 2001, p.209)

Molecular formula: C6H10N4O2

Molecular Weight: 194.2Sublimation: 178°C at 1 ATMMelting point: 238°CpKa: 14.2 at 19°C

(Sigma-Aldrich, 1999)

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Lee Wonjae, Extended Essay

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Transcript of Lee Wonjae, Extended Essay