In-situ activation of persulfate by iron filings and degradation of 1,4-dioxane

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.

Degradation of flumequine in aqueous solution by persulfate activated with common methods and polyhydroquinone-coated magnetite/multi-walled carbon nanotubes catalysts

“…4B, the characteristic peaks of DMPO-OH adducts (with hyperfine splitting constants of a N ¼ a H ¼ 14.9 G) and DMPO-SO 4 adducts (with hyperfine splitting constants of a N ¼ 13.2 G, a H ¼ 9.6 G, a H ¼ 1.48 G and a H ¼ 0.78 G) were observed, revealing the simultaneous presence of both radicals. These results were consistent with some prior observations (Fang et al, 2013b;Zhong et al, 2015). By combination of the EPR analysis and the results of the classical quenching tests, it can be inferred that SO 4 À and OH participated in the PS oxidation of FLU collectively, while SO 4 À may have a larger contribution to the activation of PS by Fe 3 O 4 / MWCNTs/PHQ for FLU removal.…”

Remediating 1,4-dioxane-contaminated water with slow-release persulfate and zerovalent iron

“…As an alternative to Fe 2+ , some researchers have switched to using zerovalent iron (Fe 0 ) as an activator for persulfate (Lee et al, 2010; Kambhu et al, 2012; Oh et al, 2010; Xiong et al, 2014; Zhong et al, 2015). Zerovalent iron has the advantage of being a solid that can serve as electron donor by itself as well as provide a longer term supply of Fe 2+ for persulfate activation.…”

“…Zerovalent iron has the advantage of being a solid that can serve as electron donor by itself as well as provide a longer term supply of Fe 2+ for persulfate activation. Zhong et al (2015) used iron-activated persulfate to treat dioxane and observed rapid decomposition during the first 30 min followed by a slower rate of decay. Kambhu et al (2012) and Chokejaroenrat et al (2015) also used Fe 0 to activate persulfate but did so by mixing persulfate and Fe 0 separately with wax to produce slow-release formulations (i.e., oxidant and iron candles).…”

Degradation of landfill leachate compounds by persulfate for groundwater remediation

“…For example, effective degradation was also reported for petroleum-hydrocarbons [20, 22] chlorinated ethylenes [24-26], chlorinated alkanes [27, 28], dioxane [29, 30], methyl tert-butyl ether (MTBE) [20, 31], polycyclic aromatic hydrocarbons (PAHs) [32-34]. Several studies have reported that persulfate was applied to remove COD and color, and improve biodegradability for landfill leachate in above-ground treatment systems.…”