Iron oxide coating of geosynthetic fibers for water treatment applications

Polypropylene fibers present favorable physical, hydraulic and specific surface area properties for use as a raw material or substrate in developing a novel iron-oxide-coated medium for the adsorption of heavy metals from drinking water. However, polypropylene fibers have not been explored for their ability to retain iron oxide coating under realistic flow rates for water treatment. This study evaluated the ability of polypropylene to retain its coating under flow rates used in water treatment, through column studies. A full factorial experimental design was used to evaluate the effects of flow rate, packing scheme (in-plane or cross-plane) and location within the column on iron retention. The polypropylene mat achieved an iron density of 86 mg Fe/g medium of material and retained 73% of this coating after being subjected to hydraulic flows in the cross-plane direction several times those used in water treatment. This is substantially higher than the amount of iron retained on sand as reported by previous researchers. Further investigation should evaluate pre-treatment methods which may facilitate strong chemical bonds between the iron and fiber to create a more consistent coating.