Surface Characteristics of Sorptive-Filtration Storm Water Media. II: Higher Specific Gravity ((rho)s > 1.0) Oxide-Coated Fixed Media

Most current control strategies for storm water treatment utilize fixed or filter-bed media with specific gravity ((rho)s) greater than 1.0. In contrast to Part I, Part II focuses on such higher density ((rho)s > 1.0) manganese-oxide-coated media that can be used in combined unit operations and processes for in-situ treatment of storm water. Methods were developed to coat manganese oxides onto sand and cementitious media for storm water treatment. With respect to manganese, coatings of ramsdellite produced a point of zero charge (PZC) of 5.2, while mixtures of birnessite and cryptomelane produced a PZC of 2.6 Manganese oxide increased the specific surface area (SSA) of sand and cementitious media. Manganese-oxide-coated sand (MOCS) produced a larger SSA (2.48-m2/g), as compared with birnessite-coated media (BCM) (1.51 m2/g), while the two have a similar surface charge (PZC = 6.4). Manganese-oxide-coated cementitious media (MOCM) produced a significantly larger SSA (19.49 m2/g), as compared with coated sand, and SEM analyses indicated the surface contained manganese oxide and calcite of thickness 10-30 µm. Based on the results, coated cementitious media provided surface characteristics that can significantly enhance filtration and adsorption of heavy metal in storm water, in comparison to sand.