Surface Characteristics of Sorptive-Filtration Storm Water Media. I: Low-Density (ρ s < 1.0) Oxide-Coated Buoyant Media

Control strategies for storm water that combine unit operations and processes can offer distinct advantages for many in situ applications in the built environment. Examples include a variety of control strategies that utilize engineered buoyant media to provide filtration and adsorption for heavy metals transported by storm water. With the goal of producing such media, methods were developed to coat iron and manganese oxide onto the surface of common polymeric media. Surface characteristics of coating media were determined by powder X-ray diffraction, infrared spectroscopy, and scanning electron microscopy analyses. Results indicated that oxide coatings ranged from 20 to 200 μm in depth, and surface areas were increased from 0.05 m2/g for uncoated spherical polymeric media to 27 m2/g for the same media after oxide coating. All manganese oxide coated media generated a net negative surface charge in the typical storm water pH range of 6–8. Media specific gravity (ρs) remained less than 0.93 even with oxide coatings. A multiple-layer oxide coating provided surface characteristics that enhance filtration and adsorption of heavy metals using coated buoyant polymeric spherical media in storm water treatment systems such as sorptive buoyant media clarifiers.