Ultrafiltration of Arsenic Using Regenerated Cellulose Membranes By Kyle Heckel April 19 th, 2008

Arsenic Arsenic and many of its compounds are highly toxic. Arsenic and many of its compounds are highly toxic. Commonly found in groundwater, wastewater, natural rivers, and mine tailings. Commonly found in groundwater, wastewater, natural rivers, and mine tailings. Current maximum contaminant level is 10ppb(10 μg/L) Current maximum contaminant level is 10ppb(10 μg/L)

Problem? Arsenic Levels in Groundwater

Ultrafiltration Uses hydrostatic pressure to force a liquid through a semi-permeable membrane. High molecular weight solutes are then retained while water and low molecular weight solutes pass through. Uses hydrostatic pressure to force a liquid through a semi-permeable membrane. High molecular weight solutes are then retained while water and low molecular weight solutes pass through. Membrane pore sizes range from Daltons. Membrane pore sizes range from Daltons. Unlike reverse osmosis or microfiltration, it uses low pressures (<100psi). Unlike reverse osmosis or microfiltration, it uses low pressures (<100psi).

Surfactants Molecules that are characterized by having a hydrophobic end and a hydrophilic end. Molecules that are characterized by having a hydrophobic end and a hydrophilic end. When the concentration of surfactant in water reaches a certain point, the hydrophobic ends aggregate to form micelles. When the concentration of surfactant in water reaches a certain point, the hydrophobic ends aggregate to form micelles. This concentration is known as the critical micelle concentration, CMC. This concentration is known as the critical micelle concentration, CMC.

Micelles Concentration below CMCConcentration above CMC AsO

Objective Assess micellar enhanced ultrafiltration using the surfactant Cetylpyridinium Chloride (CPC). Assess micellar enhanced ultrafiltration using the surfactant Cetylpyridinium Chloride (CPC). Determine membrane pore size necessary to remove the majority of arsenic from solution Determine membrane pore size necessary to remove the majority of arsenic from solution Determine how ionic salts affect the removal rates of arsenic Determine how ionic salts affect the removal rates of arsenic

Experimental setup The cell is maintained at a constant pressure which varies according to the pore size of the membrane. 1kDa – 60psi 10kDa – 30psi kDa- 10psi Seven 10mL samples are taken from each experiment. The first being from the original solution, five of which are incrementally filtered through the membrane, and the last being from the solution that is retained in the cell.

Measurements CPC levels were measured using absorption spectroscopy and a wavelength of 254nm (UV region) CPC levels were measured using absorption spectroscopy and a wavelength of 254nm (UV region) Arsenic levels were measured using an Inductively Coupled Plasma (ICP) machine located at the Arizona Department of Health Services lab in Phoenix. Arsenic levels were measured using an Inductively Coupled Plasma (ICP) machine located at the Arizona Department of Health Services lab in Phoenix.

Results SolutionMaximum MembraneCompositionRemoval 100kDa RC10mM CPC7.30% 30kDa RC0.5mM CPC10.2% 30kDa RC10mM CPC84.90% 30kDa RC10mM CPC42.50% 10mM NaCl 10kDa RC10mM CPC92.40% 10kDa RC10mM CPC63% 10mM NaCl 1kDa RC10mM CPC98.40% 1kDa RC10mM CPC44.60% 20mM NaCl

Application in Real World Membrane H2OH2O H 2 O + As +Surfactant Groundwater Feed + Surfactant FeCl 3 Sludge Fe(OH) 3 + AsO 4 H 2 O + Surfactant

Conclusions Arsenic removal rates significantly increases once the concentration of CPC added to the solution is larger than the CMC. Arsenic removal rates significantly increases once the concentration of CPC added to the solution is larger than the CMC. The ideal membrane size is around 10-30kDa due to high removal rates but lower pressures. The ideal membrane size is around 10-30kDa due to high removal rates but lower pressures. The addition of NaCl drastically decreases the removal of arsenic. The addition of NaCl drastically decreases the removal of arsenic.

Acknowledgements NASA Space Grant Fellowship NASA Space Grant Fellowship Dr. Wendell Ela Dr. Wendell Ela Dr. Eduardo Saez Dr. Eduardo Saez Miklos Szidarovszky Miklos Szidarovszky

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