title: Degradation of aqueous and soil-sorbed estradiol using a new class of stabilized manganese oxide nanoparticles.
abstract: Manganese oxide (MnO₂) was reported to be effective for degrading aqueous pharmaceutical chemicals. However, little is known about its potential use for degrading soil-sorbed contaminants. To bridge this knowledge gap, we synthesized, for the first time, a class of stabilized MnO₂ nanoparticles using carboxymethyl celluloses (CMC) as a stabilizer, and tested their effectiveness for degrading aqueous and soil-sorbed estradiol. The most desired particles (highest reactivity and soil deliverability) were obtained at a CMC/MnO₂ molar ratio of 1.39 × 10(-3), which yielded a mean hydrodynamic size of 39.5 nm and a narrow size distribution (SD = 0.8 nm). While non-stabilized MnO₂ particles rapidly aggregated and were not transportable through a soil column, CMC-stabilized nanoparticles remained fully dispersed in water and were soil deliverable. At typical aquatic pH (6-7), CMC-stabilized MnO₂ exhibited faster degradation kinetics for oxidation of 17β-estradiol than non-stabilized MnO₂. The reactivity advantage becomes more evident when used for treating soil-sorbed estradiol owing to the ability of CMC to complex with metal ions and prevent the reactive sites from binding with inhibitive soil components. A retarded first-order rate model was able to interpret the oxidation kinetics for CMC-stabilized MnO₂. When used for degrading soil-sorbed estradiol, several factors may inhibit the oxidation effectiveness, including desorption rate, soil-MnO₂ interactions, and soil-released metals and reductants. CMC-stabilized MnO₂ nanoparticles hold the potential for facilitating in situ oxidative degradation of various emerging contaminants in soil and groundwater.
authors.affiliation: Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Han
authors.affiliation: Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA.
authors.forename: Man
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA. Electronic address: zhaodon@auburn.edu.
authors.forename: Dongye
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Department of Agronomy and Soils, Auburn University, Auburn, AL 36849, USA.
authors.forename: Yucheng
authors.initials: Y
authors.lastname: Feng
mesh_terms: D000327:Adsorption; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry*; D004958:Estradiol / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017895:Manganese Compounds / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; D012987:Soil; D012989:Soil Pollutants; D004958:Estradiol; D002266:Carboxymethylcellulose Sodium; C016552:manganese dioxide
keywords: Emerging contaminants; Estrogen; Hormone; Pharmaceutical and personal care products; Soil remediation