Investigation of H2O Purification Catalyst and

Commercial FiltersR. Leonard, T. Steele

J. Wilcox, D. Drake, C. Neal

Outline• Water filtration vs. purification

• Granular Activated Carbon - “GAC”

• Adsorption

• SEM Investigation

• Plain GAC

• GAC with Pd-Au catalyst

• Brita water filter

• PUR water filter

Groundwater Contamination

• Wide use of DNAPL solvents in industry leading to groundwater contamination.

• trichloroethylene (TCE)• Abundance in groundwater and soil.• kidney stones, constipation, liver damage, pregnancy issues

cancer.• Effective low cost groundwater remediation has been an ongoing

challenge for decades.

• Cleanup of groundwater contamination is invasive and very expensive.

Filtration vs. Purification

• Purification - chemically alter contaminants• GAC with Pd-Au catalyst turns TCE into

ethane.• Filtration - physically block contaminants through

adsorption

• GAC

• Brita

• PUR

Granular Activated Carbon (GAC)

• Granular activated carbon works through adsorption.• High surface

• Total surface area and adsorption activity of GAC can be measured through the iodine capacity.

• GAC is positively charged and therefore able to remove negative ions (ozone, chlorine, fluorides, dissolved organic solutes) through adsorption.

• GAC is not effective in removing heavy metals.• Removes low concentration of radon gases in water.

• Various mesh sizes used to determine particle size distribution. • 20 mesh size = 0.85mm = (850 µm)• 40 mesh size = 0.425mm (425 µm)

Sample Grain Sizes 20-40 mesh GAC Pd-Au cat. GAC

GAC Map Spectrum

Uncatalyzed GAC Spectrum

Uncatalyzed GAC Spectrum (zoomed)

Catalyzed GAC

Catalyst Particles

Palladium particles

Gold particles

Catalyzed GAC Spectrum

Zoomed Catalyzed GAC Spectrum

• Coconut based GAC with ion exchange resin beads.• Coconut shells are heat treated with steam to produce pores within each carbon grain.

• 1,000 m2 of surface area per gram of carbon. (200,000 ft2 in each PUR faucet filter).

• PUR company claim: “MAXION Technology”• 2X more contaminants than comparable Brita filter• 96% of mercury.• 95% of industrial pollutants.• 96% of trace levels of 12 pharmaceuticals.• Pesticides (2,4-D and Atrazine)• Reduces chlorine (taste and odor)• Yet it still leaves behind beneficial fluoride.• Some microbial cysts but should not be used to filter unsafe

drinking water

PUR Water Filter

https://relianceproducts.com/docs/msds_2010/PUR%20Purifier%20of%20Water%20MSDS.pdf

PUR GAC● Mesh size about is 12 by 40 (.42mm to 1.76mm) which is

industry standard● Grain size is a balance between flow rate and removal rate

PUR GAC● Claims to reduce chlorine and some

hazardous organics

Brita Water Filter

Adsorption in action!

● According to Brita, pitcher filter contains resin beads, faucet contains zeolite. Zeolites are aluminosilicates and act as molecular sieves - sorting molecules by size exclusion

• Coconut based GAC with ion exchange resin beads. • Silver impregnated GAC.• Ion exchange resins beads are used to capture heavy elements in drinking

water.• Mesh screen filters out large particles and prevents GAC from escaping through

top of filter.• Company Claim:

• Coconut based GAC is used to reduce chlorine and improve taste.• Not designed to remove fluoride or most heavy metals. Company claim for

faucet filter (msds):•Lead: birth and cognitive defects.•Microbial Cysts: Gastrointestinal illness.•Asbestos: Chromosomal aberrations.•Benzene: Central nervous system disfunction.•Trichloroethylene and Tetrachloroethylene: Everything bad•Others

Brita Water Filter

Brita - Granular Activated Carbon

Coconut based material, potentially < 0.05 weight percent of Ag (msds)

14,400 ft2 of surface area per gram of carbon (two tennis courts)

Brita - Granular Activated CarbonC

O

Si S● Small quantity of Si could be from dissolved silica in the tap water. Silica is found in all types of soil, and it would be safe for adults to consume 3.5 g / day

Cou

nts

Cou

nts

Brita - Granular Activated Carbon● Largest grain ~ 0.8 mm● Smallest grain ~0.4 mm

● From mesh definition, 0.42 mm to 1.7 mm is 12 by 40.

● Roughly the same as Pur filter

Brita - Ion Exchange BeadsCrosslinked polymer likely made of polystyrene and attached sulfonate groups, ~0.8 mm

diameter

Ions, such as Ca2+ and Mg2+ from MgSO4 and calcium chloride (responsible for “hardness”), preferentially exchanged for Na+

Total dissolved solids (50-500 mg/L), residue from boiling water

Brita - Ion Exchange Beads

● Calcium and magnesium trapped on bead. Ca deposit ~0.5 um seen above ● Polymer base is actually porous, but appears solid

Cou

nts

Mg Ca

C

O

Brita - Ion Exchange Beads

● Magnesium, calcium, chlorine trapped on bead (Mg and Ca are contained in asbestos which Brita removes)

● The Brita filter contains Ag (1 um particle pictured above), but was not found everywhere● Silver is antimicrobial and antimicrobial. Can prevent biofilm growth

C

O

Mg

Ca

AgCl

http://www.who.int/water_sanitation_health/dwq/chemicals/Silver_water_disinfection_toxicity_2014V2.pdf

Cou

nts

PUR Resin Bead

-● The size of the beads were ~400um - 800um in diameter● Iron sulfate and sodium carbonate composition (according to MSDS)

PUR Resin Bead

Future Work

• Use known size of EDX maps to characterize areal dispersion of catalyst. Are there a lot of chunks?

• Use EDX weight percentage data to figure out the atomic ratio between palladium and gold

ReferencesM. O. Nutt, J.B. Hughes, M.S. Wong. “Designing Pd-on-Au Bimetallic Nanoparticle Catalysts for Trichloroethene Hydrodechlorination.” Environ. Sci. Technol. 2005, 39, 1346-1353

T. Li, S. Li, Y. Li, Z. Jin. “Dechlorination of Trichloroethylene in Groundwater by Nanoscale Bimetallic Fe/Pd Particles.”

“BRITA® ON TAP FAUCET FILTER.” http://msdsdigital.com/brita%C2%AE-tap-faucet-filter-msds-0. (Accessed 03-09-2016)

“PUR Purifier of Water MSDS” http://msdsdigital.com/brita%C2%AE-tap-faucet-filter-msds-0. (Accessed 03-09-2016)

“Ferrous Sulfate” http://www.kemira.com/en/industries-applications/pages/ferrous-sulfate.aspx

“Silica Fact Sheet” http://www.mylongview.com/modules/showdocument.aspx?documentid=1400 (Accessed 03-10-16)

“Ion Exchange for Dummies” http://www.lenntech.com/Data-sheets/Ion-Exchange-for-Dummies-RH.pdf (Accessed 03-10-16)

“Ion Exchange Resins” http://nzic.org.nz/ChemProcesses/water/13D.pdf (Accessed 03-10-16)

“Here’s What Brita Reduces or Removes from Tap Water” https://www.brita.com/why-brita/what-we-filter/ (Accessed 03-10-16)

R. Catabay, J. Jiao. “Palladium-based bimetallic catalysis and applications in groundwater remediation.” Portland State Univ. Aug 17 2015.

“Brita Water Filters” https://www.brita.com/. (Accessed 03-09-2016)

http://www.pur.com/