Water Hardness 1u3n5y

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Jill Bontrager Lab Performed on: March 17, 2009 Experiment 10: Exploring the Water Hardness of Bottled Waters Chem. 111-103 Group : Kirsten Bickhart, Adam Brous, Nick Bertsch, Jake Bezalel

TA: Ting-Hao Phan

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Introduction: Water hardness is determined by concentration of metallic solids, such as magnesium and calcium ions, dissolved in a water source. The degree of water hardness is determined by the concentration of ions in a source; hard water contains a high concentration of metallic ions while softer water contains a lower concentration. Since water is a universal solvent, it readily collects ions and impurities when moving over rocks and soils. The most prevalent ions collected in a 1

water source are Ca2+and Mg2+.

The hardness level of water is important for a number of reasons. Although hard water is not a health risk, it can negatively affect the performance of pipe efficiency, detergents in laundry, and the use of shampoo and soap for bathing. Deposits of Ca2+and Mg2+ in hard water can form limestone deposits that slow and block pipes, which is inefficient and costly. When washing clothing with hard water, clothing may become scratchy and harsh as the ions damage the cloth fibers. Hard water can create limestone film deposits in hair while bathing, as well as causing soap to be less effective at removing dirt and bacteria from the skin. On a larger scale, metallic ions in water can also cause metal corrosion and structural weakness of buildings and bridges.2 Water hardness is measured either in grains per gallon or parts per million. The Environmental Protection Agency (EPA) regulates the standards for drinking water based on primary conditions, which evaluate health and safety, while the secondary conditions are based on taste, color odor, and corrosivity. The following chart shows how the U.S. Department of the Interior and Water Quality Association classifies water2: Figure 1.1: Classification of Water Classification

mg/l or ppm

grains/gal

Soft

0 - 17.1

0–1

Slightly hard

17.1 – 60

1 - 3.5

Moderately hard

60 – 120

3.5 - 7.0

Hard

120 – 180

7.0 - 10.5

Very Hard

180 & over

10.5 & over

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Water hardness can be tested in a variety of ways. One of the easiest ways of determining the solutes present is to evaporate water from a sample and evaluate the remaining solids. The method is called finding the Total Dissolved Solids (TDS) of a sample. This type of analysis is good for determining the scale of how many ions are present in a sample, but is unable to determine a more exact amount of cations present. A more specific determinant of water hardness is determined through ethylenediaminetetracetic, or EDTA. The EDTA method calculates how many divalent cations (cations with a plus-two charge) are present in the sample of water through a complexation reaction, as shown below:3 HD2- (blue) + Mg2+ + Ca2+ MgD-(red) + H+ + Ca2+ CaEDTA + MgEDTA + HD2- (last:blue) To start the EDTA Titration, the pH of the water sample is adjusted by adding NH3/NH4 buffer. When EBT indicator is added, it is in the HD2- form, so the pH is high and the solution turns blue. If Mg2+ is in the water sample, it will react with the indicator and turn a red wine color. At this point, EDTA solution is added, which reacts with Ca2+ and the magnesium indicator to produce colorless MgEDTA chelate. A chelate forms multiple bonds with metal cations, inhibiting them from bonding with other elements or forming precipitates (or residue). Once the magnesium chelate is formed, the color of the solution returns to blue. EDTA is used in many commercial products like bathtub cleaners (dissolving limestone scum) and salad dressing (preserving the oil).3 Another method of water softening is Atomic Absorption Spectroscopy (AA), which is useful for determining dissolved metals in a solution. An AA Spectrometer has four main parts: an aspirator (to collect the liquid sample), lamps that emit specific wavelengths, a flame or other heat source, and a photon detector. Specific lamps are chosen according to what one wants to test, such as calcium for example. After the aspirator suctions a sample of the liquid being tested, any calcium ions in the flame will absorb light from the lamp before reaching the photon detector. High levels of the cation, such as calcium, render high absorbance values. Once an absorption level is determined (in nm), it can be used to calculate the concentration of the ion through the use of a calibration graph.4 AA and EDTA methods of determining water hardness are fairly different. AA analysis evaluates only one cation at a time with the use of a spectrometer machine. EDTA calculates the

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sum of all cations and cannot differentiate between them. EDTA involves titrating the sample with indicators and the chelate-forming EDTA, while AA relies on a lamp source, a flame and a detector. AA is more exact, since the machine calculates the absorbance level of one ion, which limits chances to make both human and calculation error. EDTA, however, requires titrations of different solutions, which leaves room for error in the precision of the experiment.5 As discussed before, water hardness can be a hindrance at industrial, economic and residential levels. Cation exchange resins are therefore very useful in softening water. In both the commercial softening agent and the resin, cation exchange was the means to which the water samples did soften. The resin takes up calcium and magnesium ions (divalent cations) and releases sodium and hydrogen ions (monovalent cations), which makes water ―softer‖. Therefore, both of the softening techniques worked to lower hardness (in ppm) significantly.6 In this experiment, five bottled water brands were tested: Evian, Fiji, Kirkland, Aquafina, and Deer Park. The market for bottled water has dramatically increased over the last twenty years, due to its portability and ―purer‖ taste. Bottled water regulations and governed by a different set of rules than municiple water that are usually more lenient. The chemical treatment used to keep municipal water hardness at the correct level can have an unpleasant taste, so bottled water manufacturers try to avoid such stipulations.7 Within bottled water, there is mineral water, such as Evian and Fiji, which contain a hardness level of at least 250ppm. Spring water, on the other hand, is usually softened through cation exchange, so it has a lower hardness level. The hypothesis of this experiment is that the Evian and Fiji waters will have the highest hardness levels, due to the more natural process of filtering. As for Evian, the water spends 15 years filtering through an aquifier on a mountain, and should therefore have a stronger mineral composition than the spring waters, Deer Park, Aquafina, and Kirkland. Spring waters differ in hardness depending on their geological location but are treated chemically for hardness before being marketed, so are softer than mineral waters.8 Procedure: The full explanation of the procedure for Experiment 10: The Chemistry of Natural Waters, can be found in chapter 10 of PSU Chemtrek.3 In this experiment, each of the five bottled water samples—Evian, Fiji, Kirkland, Aquafina and Deer Park—was tested for hardness through a number of methods including TDS, AA, and EDTA.

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The first method measures the Total Dissolved Solids (TDS) of an evaporated water sample. By placing a drop of each sample (as well as two references) on aluminum foil and heating the source with a hot plate, the water evaporated, leaving white solid residue. The white solids remaining are the salts of the original water sample, which helped determine the hardness of the samples. High TDS results correlated with the harder water samples. The salts that are likely to be present in the remaining residue are ions like Ca2+and Mg2+. The second method is Atomic Absorption (AA) Spectroscopy. In the AA analysis, the samples were tested by a machine that measures calcium and magnesium levels separately. By inserting the aspirator into each water sample, the absorption level (in nanometers) of Ca2+ and Mg2+ was calculated. Using the absorption level, as well as the calibrated equations for both ions, the hardness (in ppm) of the samples was calculated. These ppm values were then converted into their ―equivalent concentration‖ of CaCO3, and then added together for a resulting total hardness. The third method used was EDTA titration used, in which a series of dilutions was performed. EDTA is used in a complexation reaction with the water samples in order to determine the concentration of ions such as Ca2+ and Mg2+ , as well as other resulting minerals and ions. The first well that changes to a blue color is considered the volume of EDTA necessary in the titration. Results are subject to human error in this method of testing specifically, due to the titration. In addition to the hardness calculated in the initial EDTA method, the samples were observed by EDTA titration with a commercial softening agent and with resin. Results: The results and information gathered is from the lab notebooks of group as follows: Jill Bontrager9, Jake Bezalel10, Kirsten Bickhart11, Adam Brous12, and Nick Bertsch.13 Total Dissolved Salts (TDS) Results: By using TDS as a means of investigating water hardness, we obtained the following results: Figure 1.2: Total Dissolved Salts (TDS) of Each Water Sample: Water Sample: Observations: Distilled Water No residue 1 x 10-3 M Ca2+ - reference White residue Evian Heavier residue than reference Fiji Lighter residue than reference Kirkland Heavier residue than reference Aquafina No residue Deer Park Lighter residue than reference

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By comparing the residue results as compared to the reference, Aquafina showed no residue, Fiji and Deer Park showed lighter residue, and Evian and Kirkland showed a heavier residue. This loosely follows the TDS analysis of the softer waters having lighter residue and hard waters having heavier residues. Atomic Absorption (AA) Results: Each group member sampled a different bottled water brand for the experiment. After running the samples through the AA water device, the following results were obtained: Figure 1.3: Bottled Water Samples and Absorption rates according to AA Sample Name Ca2+Absorbance (@ Mg2+ Absorbance 422.7nm) (@202.5nm) Evian 0.1390nm 0.1131nm Fiji 0.4060nm 0.1943nm Kirkland 0.0378nm 0.0336nm Aquafina 0.0004nm 0.0038nm Deer Park 0.0738nm 0.0873nm The AA device, run by the Penn State Chemistry Department, obtained the standard values of calibration of Ca2+ and Mg2+ concentrations: Figure 1.4: AA Standards of Ca2+ concentration Ca2+ Concentration (ppm) Ca2+Absorbance (@ 422.7nm) 0 -1.000 0.01609 5.000 0.08087 10.000 0.16286 25.000 0.32177 50.000 0.57016

Check Standard for Ca2+ (ppm) -0.99 4.82 10.16 23.37 50.89

Figure 1.5: AA Standards of Mg2+ concentration Mg2+ Concentration (ppm) Mg2+Absorbance (@ Check Standard for Mg2+ 202.5nm) (ppm) 0 --1.000 0.03229 1.27 5.000 0.12431 4.99 10.000 0.23623 9.84 25.000 0.54136 25.25 30.000 0.61989 30.53 The absorbance standards from the AA device were used to calculate the calibration curve shown on the following graphs. These linear equations are used to calculate hardness (in ppm) for both Ca2+ and Mg2+.

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Figure 2.1: Calibration of Ca2+Concentration by AA Calibration of Ca2+ Concentration by AA y = 0.011x + 0.020 Absorbance Value (at 422.7 nm)

y = 0.0113x + 0.0206 R² = 0.9911

Series1 Linear (Series1) Linear (Series1)

Calcium Ion Concentration (ppm)

This graph, like the one below, shows that as concentration (in ppm) increases, absorbance value (in nm) increases. This direct relationship between concentration and absorbance provides a linear equation that can be used to determine the hardness value of the Ca2+ and Mg2+ Figure 2.2: Calibration of Mg2+Concentration by AA Calibration of Mg2+ Concentration by AA

Absorbance Value (at 202.5 nm)

y = 0.020x + 0.014

Series1 Linear (Series1)

Magnesium Concentration (ppm)

Example equations for calibration graphs: y-value=absorbance (nm) x-value=concentration (ppm) For Ca2+: y = 0.011x + 0.020 (0.1390nm)=0.011x+0.020 0.119=0.011x

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x=10.818 ppm For Mg2+: y=0.020x+0.014 (0.1131nm)=0.020x+0.014 0.0991=0.020x x=4.955ppm In the Evian sample, it was necessary to dilute by 50 drops of distilled water due to its hardness. Therefore, in order to obtain an accurate concentration, one has to multiply the ppm value calculated by 50. The resulting hardness for the Evian sample is then: For Ca2+: 10.818 x 50=540.9ppm For Mg2+: 4.995 x 50=249.75ppm For the other water samples, it was not necessary to dilute with distilled water, so the resulting ppm values are the same as the calculated calibrations. The next step is converting the concentration values into their ―equivalent concentration of calcium carbonate,‖ which determines the hardness of the sample. A sample calculation of calculating hardness is as follows: Ca2+ hardness: 100g CaCO3 / 1 mole 540.9 ppm Ca2+ x ---------------------------- = 1352.25 ppm hardness 40.0g Ca2+ / 1 mole Mg2+ hardness: 100g CaCO3 / 1 mole 249.75 ppm Mg2+ x ---------------------------- = 624.375 ppm hardness 24.3g Ca2+ / 1 mole The Ca2+ and Mg2+ hardness must be added together for the total hardness value from AA analysis. Total hardness: 1352.25ppm + 624.38ppm = 1976.63 ppm The following chart compiles all group results of the hardness results from AA analysis: Figure 1.6: Hardness calculated from AA Analysis: Sample

Ca2+ hardness (ppm)

Evian Fiji Kirkland Aquafina Deer Park

540.9ppm 34.10ppm 3.8ppm N/A (too soft) 4.80ppm

Mg2+ hardness (ppm) 249.75ppm 8.69ppm 3.79ppm N/A (too soft) 3.54ppm

Total Hardness— converted to CaCO3 1976.63 ppm 121.01ppm 25.1ppm N/A (too soft) 26.57ppm

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EDTA Results: In addition to the AA analysis, divalent cation analysis was conducted through EDTA Titration. The following results were obtained and samples are given for each unique calculation: Ppm calculated through titration: (2.0x10^-4 M)(2 drops EDTA)=(sample concentration)(1 drop) 4.40x10-4M x 50*=2.0x10-2=2000ppm *=sample diluted by 50 drops Molarity of water sample: (2.0x10-2M) (100g CaCO3) (1000mgCaCO3) 2000mg CaCO3 ------------- x ------------------ x ------------------- = ------------------( 1 L) (1 MCaCO3) (1g CaCO3) 1 L Solution Grains per gallon of water sample: (2000mg CaCO3) (1 grain) (3.785 L) 117.0 grain ---------------- x --------------- x ------------------- = ------------------( 1 L) (64.7g) (1 gallon) 1 gallon Ppm of water sample: (117.0 grain) (17.1ppm) ---------------- x --------------- = 2000.7ppm (1 gallon) (1 grain/gal) Figure 1.7: Compiled EDTA Results Sample VolumeEDTA EDTA initial (drops) (ppm) Evian 2 drops 2000.7 ppm*

Molarity Grains per (mg/L) gallon 2000mgCaCO3 117.0 grains ------------------ ------------1 L Solution 1 gallon Fiji 4 drops 80.0ppm 80mgCaCO3 4.68 grains ------------------ -------------1 L Solution 1 gallon Kirkland 2 drops 40.0ppm 40mgCaCO3 2.34 grains ------------------ -------------1 L Solution 1 gallon Aquafina N/A N/A N/A N/A Deer Park 2 drops 40.0ppm 40mgCaCO3 2.34 grains ------------------ --------------1 L Solution 1 gallon *Dilution: multiplied by 50 distilled water drops due to extreme hardness Using a commercial water-conditioning agent, hardness levels were calculated as follows: Softening Agent (Arm + Hammer) results: (Evian sample changed after 6 drops at 12.0x10-4 M, determined by EDTA titration)

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Molarity of water sample with softening agent: (12.0x10-4 M) (100g CaCO3) (1000mg CaCO3) 120mg CaCO3 ---------------- x --------------- -- x ------------------- = ------------------(1 L) (1 M CaCO3) (1g CaCO3) 1 L Solution Grains per gallon: (120mg CaCO3) (1grain) (3.785 L) 7.02 grain ---------------- x --------------- -- x ------------------- = ------------------(1 L) (64.7mg) (1 gallon) 1 gallon Ppm: 17.1ppm 7.02 grain/gal x -------------- = 120.04ppm 1 grain/gal. To determine how much softer the Evian sample became, keeping in mind the dilution, the following calculation gives a percentage of the change in water softness:

Figure 1.8: Water Softening Agent EDTA titration results: Sample

Volume (drops) of Softening Agent 6 drops

Water Water Water Softening Softening Softening Molarity Grains/gallon Hardness (mg/L) (ppm) Evian 120mgCaCO3 7.02 grains 120.04ppm ---------------- --------------1 L Solution 1 gallon Fiji 3 drops 60mgCaCO3 3.51 grains 60.0ppm -----------------------------1 L Solution 1 gallon Kirkland 1 drop 20mgCaCO3 1.17 grains 20ppm ----------------------------1 L Solution 1 gallon Aquafina N/A N/A N/A N/A Deer Park 1 drop 20mgCaCO3 1.17 grains 20ppm ----------------------------1 L Solution 1 gallon From the softening agent results, show that the hardness (in ppm) is reduced by the initial EDTA titrations. By using the cation exchange resin in the removal of Ca2+ and Mg2+ to investigate the softening effect on the hard water samples, the following results were obtained: Resin: (Evian sample changed after 4 drops at 8.0x10-4 M, determined by EDTA titration)

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Molarity of water sample with resin: (8.0x10-4 M) (100g CaCO3) (1000mg CaCO3) 80mg CaCO3 ---------------- x --------------- -- x ------------------- = ------------------(1 L) (1 M CaCO3) (1g CaCO3) 1 L Solution Grains per gallon: (80mg CaCO3) (1grain) (3.785 L) 4.68 grain ---------------- x --------------- -- x ------------------- = ------------------(1 L) (64.7mg) (1 gallon) 1 gallon Ppm: 17.1ppm 4.68 grain/gal x -------------- = 80.03ppm 1 grain/gal. To determine how much softer the Evian sample became, keeping in mind the dilution, the following calculation gives a percentage of the change in water softness: The following chart compiles all of the information for EDTA titrations for resin: Figure 1.9: Resin EDTA Titration Results: Sample Volume Resin Resin Resin (drops) of Molarity Grains/gallon Hardness Resin (mg/L) (ppm) Evian 4 drops 80mgCaCO3 4.68 grains 80 ppm ---------------- -------------1 L Solution 1 gallon Fiji 3 drops 60mgCaCO3 3.51 grains 60ppm ---------------- --------------1 L Solution 1 gallon Kirkland Less than 1 Less than Less than Less than 20 drop 20mgCaCO3 1.17 grains ppm ---------------- ---------------1 L Solution 1 gallon Aquafina N/A N/A N/A N/A Deer Park Less than 1 Less than Less than Less than 20 drop 20mgCaCO3 1.17 grains ppm ----------------- ----------------1 L Solution 1 gallon Overall, the resin softened the water even more than the commercial softening agent, according to the results above.

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Discussion: Each water sample was tested for hardness with the AA and EDTA methods. For the Evian sample, the AA value was 1973.63ppm and the EDTA value was 2000.7ppm.9 For the Fiji sample, the AA value was121 ppm and the EDTA value was 80ppm.10 The Kirkland sample has an AA value of 25.1ppm and an EDTA value of 40 ppm.11 The Aquafina sample was too soft to retrieve hardness data for either AA or EDTA, so the values are obviously 0.0ppm for both. For the Deer Park sample, the AA value was 23.57ppm and the EDTA value was 40.0ppm. The initial hardness values for both AA and EDTA for the five samples my hypothesis for the most part. Evian and Fiji have the highest hardness values, as Evian would be considered very hard and Fiji would be considered hard, according to the U.S. Department of the Interior and Water Quality Association classifies water (see Figure 1.1). The Evian sample was initially so hard that it had to be diluted with 50 drops of distilled water before titrating the well samples with EDTA. Due to the dilution, all the hardness calculations for both AA and EDTA had to be multiplied by 50, making the hardness levels significantly higher than the other samples, including Fiji. According to the Evian website, the mineral water goes through a 15 year filtering process, but the aquifier has glacial sand content and other minerals which gives it such a high hardness value.8 In comparing the data between AA and EDTA methods, all of the AA values were less than the EDTA values. These results make sense, because the AA Spectrometer measures the absorbance of one cation at a time, white EDTA s for the hardness value of all cations at once. AA is more accurate because it gives machine-calculated results that leave less room for human error, in addition to calculating a much more specific absorbance rate, such as one cation at a time. EDTA involves a lot of human calculation from counting the titrating drops, to handdropping into the 1x12 well. The precision of the results can be skewed even if just one drop is miscalculated. Also, the EDTA results for all impurities and salts in the sample, making it harder to distinguish the key cations present in the sample. In our experiment with bottled waters, the AA calculations were both more accurate and precise than the EDTA titrations.

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―Ion Exchange Resins.‖ http://www.nzic.org.nz/ChemProcesses/water/13D.pdf (accessed April 2008)

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Technology of bottled water, 2nd edition. Edited by Dorothy Senior and Nicholas Dege. Oxford, UK: Blackwell Publishing Ltd. 2004. Pp 1-5.

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―Bottled Water of the World.‖ http://www.finewaters.com/Bottled_Water//Evian.asp (accessed April 2008)

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Bontrager, Jill, Chem 111 Laboratory Notebook, pp.35-41

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Bezalel, Jake, Chem 111 Laboratory Notebook, pp.38-42

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Bickhart, Kirsten, Chem 111 Laboratory Notebook, pp. 35-41

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Brous, Adam, Chem 111 Laboratory Notebook, pp.27-31

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Bertsch, Nick, Chem 111 Laboratory Notebook, pp. 25-27