title: Remediating 1,4-dioxane-contaminated water with slow-release persulfate and zerovalent iron.
abstract: 1,4-dioxane is an emerging contaminant that was used as a corrosion inhibitor with chlorinated solvents. Metal-activated persulfate can degrade dioxane but reaction kinetics have typically been characterized by a rapid decrease during the first 30 min followed by either a slower decrease or no further change (i.e., plateau). Our objective was to identify the factors responsible for this plateau and then determine if slow-release formulations of sodium persulfate and Fe0could provide a more sustainable degradation treatment. We accomplished this by conducting batch experiments where Fe0-activated persulfate was used to treat dioxane. Treatment variables included the timing at which the dioxane was added to the Fe0-persulfate reaction (T = 0 and 30 min) and including various products of the Fe0-persulfate reaction at T = 0 min (Fe2+, Fe3+, and SO42-). Results showed that when dioxane was spiked into the reaction at 30 min, no degradation occurred; this is in stark contrast to the 60% decrease observed when added at T = 0 min. Adding Fe2+at the onset (T = 0 min) also severely halted the reaction and caused a plateau. This indicates that excess ferrous iron produced from the Fe0-persulfate reaction scavenges sulfate radicals and prevents further dioxane degradation. By limiting the release of Fe0in a slow-release wax formulation, degradation plateaus were avoided and 100% removal of dioxane observed. By using14C-labeled dioxane, we show that ∼40% of the dioxane carbon is mineralized within 6 d. These data support the use of slow-release persulfate and zerovalent iron to treat dioxane-contaminated water.
authors.affiliation: Department of Civil Engineering, University of Nebraska, Lincoln, NE 68583-0531, USA. Electronic address: annkambhu@gmail.com.
authors.forename: Ann
authors.initials: A
authors.lastname: Kambhu
authors.affiliation: Department of Biological Systems Engineering, University of Nebraska, Lincoln, NE 68583-0726, USA. Electronic address: gren.r.megan@gmail.com.
authors.forename: Megan
authors.initials: M
authors.lastname: Gren
authors.affiliation: School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0915, USA. Electronic address: wei.tangv@gmail.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Tang
authors.affiliation: School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0915, USA. Electronic address: scomfort@unl.edu.
authors.forename: Steve
authors.initials: S
authors.lastname: Comfort
authors.affiliation: Department of Chemistry, Albion College, Albion, MI 49224, USA. Electronic address: charris@albion.edu.
authors.forename: Clifford E
authors.initials: CE
authors.lastname: Harris
mesh_terms: D002244:Carbon; D004146:Dioxanes / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D017670:Sodium Compounds / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D013997:Time Factors; D014874:Water Pollutants, Chemical
chemical_list: D004146:Dioxanes; D017670:Sodium Compounds; D013431:Sulfates; D014874:Water Pollutants, Chemical; C069025:sulfate radical; D002244:Carbon; D007501:Iron; C024625:sodium persulfate; C025223:1,4-dioxane
keywords: Chlorinated solvents; Dioxane; Persulfate; Slow-release oxidants; TCE