In-situ activation of persulfate by iron filings and degradation of 1, 4-dioxane. (15th October 2015)

• Record Type: Journal Article
• Authors: Zhong, Hua; Brusseau, Mark L.; Wang, Yake; Yan, Ni; Quig, Lauren; Johnson, Gwynn R.
• Is Part Of: Water research. Volume 83(2015)
• Page Start: 104
• Page End: 111
• Publication Date: 2015-10-15
• Subjects: Persulfate -- Iron filings -- Dioxane -- Radical -- Surface reaction -- Permeable reactive barrier; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2015.06.025
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Activation of persulfate by iron filings and subsequent degradation of 1, 4-dioxane (dioxane) was studied in both batch-reactor and column systems to evaluate the potential of a persulfate-enhanced permeable reactive barrier (PRB) system for combined oxidative-reductive removal of organic contaminants from groundwater. In batch experiments, decomposition of persulfate to sulfate and degradation of dioxane both occurred rapidly in the presence of iron filings. Conversely, dioxane degradation by persulfate was considerably slower in the absence of iron filings. For the column experiments, decomposition and retardation of persulfate was observed for transport in the columns packed with iron filings, whereas no decomposition or retardation was observed for transport in columns packed with a reference quartz sand. Both sulfate production and dioxane degradation were observed for the iron-filings columns, but not for the sand column. The pH of the column effluent increased temporarily before persulfate breakthrough, and significant increases in both ferrous and ferric iron coincided with persulfate breakthrough. Multiple species of free radicals were produced from persulfate activation as determined by electron paramagnetic resonance (EPR) spectroscopy. The impact of the oxidation process on solution composition and iron-filings surface chemistry was examined using ICP-MS, SEM-EDS, and XRD analyses. A two-stage reaction mechanism is proposed to describe the oxidation process, consisting of a first stage of rapid, solution-based, radical-driven decomposition of dioxane and a second stage governed by rate-limited surface reaction. The results of this study show successful persulfate activation using iron filings, and the potential to apply an enhanced PRB method for improving in-situ removal of organic contaminants from groundwater. Graphical abstract: Highlights: Persulfate is activated by iron filings to degrade dioxane. Dioxane may undergo a surface reaction mechanism in persulfate/iron-filings system. Persulfate is superior to H2 O2 for dioxane degradation. Persulfate-enhanced permeable reactive barrier was successful in treating dioxane.