Chemical Regeneration of Manganese Oxide-Coated Sand for Oxidation of Organic Stormwater Contaminants

Abstract

Urban stormwater, municipal wastewater effluent, and agricultural runoff contain trace amounts of organic contaminants that can compromise water quality. To provide a passive, low-cost means of oxidizing substituted phenols, aromatic amines, and other electron-rich organic compounds during infiltration of contaminated waters, we coated sand with manganese oxide using a new approach involving the room-temperature oxidation of Mn with permanganate. Manganese oxide-coated sand effectively oxidized bisphenol A under typical infiltration conditions and sustained reactivity longer than previously described geomedia. Because geomedia reactivity decreased after extended operation, chlorine was evaluated for use as an in situ geomedia regenerant. Geomedia regenerated by HOCl demonstrated similar reactivity and longevity to that of virgin geomedia. Chemical analyses indicated that the average manganese oxidation state of the coatings decreased as the geomedia passivated. X-ray absorption spectroscopy and X-ray diffraction showed that the reactive virgin and regenerated geomedia coatings had nanocrystalline manganese oxide structures, whereas the failed geomedia coating exhibited greater crystallinity and resembled cryptomelane. These results suggest that it is possible to regenerate the oxidative capacity of manganese oxide-coated sands without excavating stormwater infiltration systems. These results also suggest that manganese oxide geomedia may be a cost-effective means of treating urban stormwater and other contaminated waters.

Hydrophilic trace organic contaminants in urban stormwater: occurrence, toxicological relevance, and the need to enhance green stormwater infrastructure

“…180 Recently, manganese oxide-coated sand has been proposed as cost-effective and regenerative geomedia for stormwater treatment to target the removal of hyphil-TrOCs. 181,182 Grebel et al 181 observed that birnessite (a layered MnO 2 ) was highly reactive towards aromatic compounds with electron-donating moieties (e.g., BPA and 2-mercaptobenzothiazole) and moderately reactive towards compounds with electron-withdrawing functional groups (e.g., diuron) or steric hindrance at the most likely reaction site (e.g., prometon). However, birnessite was unreactive towards numerous other hyphil-TrOCs (e.g., TCPP, benzotriazole, and fipronil).…”

“…181 Stormwater constituents such as dissolved organic matter or inorganic ions (e.g., calcium or carbonate) can contribute to exhaustion of the redox reactivity of manganese oxide-coated sands. 181 Charbonnet et al 182 found that exhausted manganese oxide-coated sand could be regenerated with HOCl leading to similar reactivity and longevity than the pristine MnO 2 . Geomedia regeneration in the field could be a main advantage as it prevents excavation of the exhausted material, reduces disposal costs, and helps to overcome implementation barriers.…”

“…More research is needed to develop cost-effective and sustainable management strategies for exhausted stormwater treatment materials, e.g., regeneration of MnO 2 or biochar replacement schedules. 182,212 • As stormwater biofilters often face prolonged dry periods and, thus, present underused water treatment potential, dual-mode biofilters for treatment of stormwater in wet seasons and greywater in dry seasons have been proposed. 143 The fate of greywater-derived hyphil-TrOCs in conventional and geomedia-amended biofilters needs to be investigated especially for infiltrating systems.…”

Identifying the mechanisms of cation inhibition of phenol oxidation by acid birnessite

“…The oxidation of organic contaminants by manganese oxides is an important reaction that influences contaminant fate in aqueous systems (Duckworth et al., 2017; Grebel, Charbonnet, & Sedlak, 2016; Li, Zhang, Ertunc, Schaeffer, & Ji, 2012; Post, 1999; Remucal & Ginder‐Vogel, 2014; Sim, Lee, Lee, Choi, & Oh, 2009; Siqueira, Nair, Hammerschmidt, Safir, & Putnam, 1991; Wang & Giammar, 2015). Because of their oxidative reactivity, manganese oxides have been proposed for passive water treatment for contaminants in urban stormwater runoff, green infrastructure, or water from contaminated sources (Charbonnet et al., 2018; Grebel et al., 2013, 2016; Huang et al., 2018; Klausen, Haderlein, & Schwarzenbach, 1997; Luthy & Sedlak, 2017; Pizzigallo, Ruggiero, Crecchio, & Mascolo, 1998; Shaikh et al., 2016; Stone, 1987; Stone & Morgan, 1984; Tebo et al., 2004; Ulrich & Stone, 1989). Here, we determine that surface‐bound cations, which include both sorbed and interlayer cations, have a large effect on manganese oxide reactivity.…”

“…The phenolic compounds used in this study include bisphenol A (BPA), 5-chloro-2-(2,4-dichlorophenoxy) phenol (triclosan), estrone, and 4-methylphenol (p-cresol) (Supplemental Figure S1). Phenolic compounds such as these are found in wastewater effluents that discharge into natural ecosystems (Bina, Mohammadi, Amin, Pourzamani, & Yavari, 2018;Bulloch et al, 2015;Charbonnet, Duan, van Genuchten, & Sedlak, 2018;Grebel et al, 2013Grebel et al, , 2016Huang, Zhong, Dai, Liu, & Zhang, 2018;Lin, Liu, & Gan, 2009b;Luthy & Sedlak, 2017;Montes-Grajales, Fennix-Agudelo, & Miranda-Castro, 2017;Yang, Ok, Kim, Kwon, & Tsang, 2017) and serve to show any differences in cation effects due to phenolic structure (Trainer, Ginder-Vogel, & Remucal, 2020). Cations can inhibit the reaction rate of phenols with manganese oxides (Remucal & Ginder-Vogel, 2014), which has implications for environmental oxidative degradation of phenolic contaminants because cations are ubiquitous in natural systems.…”