Abstract
Phthalic acid esters (PAEs) are often detected in remediated groundwater using appropriate oxidant materials by in situ groundwater treatment. The study compares zero-valent iron–persulfate with a pyrite–persulfate system to degrade three PAEs—di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and dimethyl phthalate (DMP). Column experiments were conducted, and rapid oxidation occurred in a pyrite–persulfate system due to sulfate radical generation. DMP concentration was found at about 60.0% and 53.0% with zero-valent iron (ZVI) and pyrite activation of persulfate, respectively. DBP concentration was measured as 25.0–17.2% and 23.2–16.0% using ZVI–persulfate and pyrite–persulfate systems, respectively. However, DEHP was not detected. The total organic carbon concentration lagged behind the Ʃ3 PAEs. Persulfate consumption with ZVI activation was half of the consumption with pyrite activation. Both systems showed a steady release of iron ions. Overall, the oxidation–reduction potential was higher with pyrite activation. The surface morphologies of ZVI and pyrite were investigated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and XPS. Intensive corrosion occurs on the pyrite surface, whereas the ZVI surface is covered by a netting of iron oxides. The pyrite surface showed more oxidation and less passivation in comparison with ZVI, which results in more availability of Fe 2 + for persulfate activation. The pyrite–persulfate system is relatively preferred for rapid PAE degradation for contamination.
Highlights
Subsurface groundwater supplies can be contaminated by a variety of organic compounds, including phthalic acid esters (PAEs), that are released by anthropogenic activities [1,2]
PAEs are a group of chemical compounds that are extensively used as plasticizers and additives in commercial and industrial products [3,4,5]
The decomposition of PAEs occurred in the order dimethyl phthalate (DMP) < dibutyl phthalate (DBP) < di(2-ethylhexyl) phthalate (DEHP) with both zero-valent iron (ZVI) and pyrite activating materials
Summary
Subsurface groundwater supplies can be contaminated by a variety of organic compounds, including phthalic acid esters (PAEs), that are released by anthropogenic activities [1,2]. Water 2020, 12, 354 used in subsurface in-situ chemical activation of PS because of their availability, cost-effectiveness, ease of application, and catalytic properties. Zero-valent iron (ZVI) and pyrite showed efficient degradation on a wide range of organic pollutants among them [15,25]. Applications of persulfate activation using ZVI and pyrite are compared and categorized for the development of an in-situ subsurface chemical oxidation technology, e.g., permeable reactive barrier (PRB). 4 , PAEs oxidation behavior of ZVI and pyrite during in-situ groundwater treatment. To screen for a more suitable reactive medium for in-situ remediation of PAEs-contaminated groundwater, the study is aimed to compare the degradation of the PAEs with. The study focuses on the consumption behavior of PS, release of iron ions, and solution pH value to analyze the formation of iron corrosion products on the particle surface before and after the reaction
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