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  • Author: Jaroslav Nosek x
  • Energy Engineering x
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Abstract

Zero-valent iron is very effective in the treatment of groundwater contaminated with chlorinated hydrocarbons and solvents broadly used in industrial production. In terms of its sustainability and cost, a legitimate effort has been devoted to the optimization of the remediation process, which can be demanding and expensive. In this study, the application potential and fundamental properties of several commercial micro-sized zero-valent iron (μZVI) were investigated. Although the manufacturers report the basic parameters of μZVI, it has been shown that the actual reactivity of apparently similar products varies notably. This work was focused on monitoring of frequently occurring contaminants. The actual contaminated water from the Pisecna locality -former landfill of industrial waste, with high levels of chlorinated ethenes and ethanes (PCE, TCE, cis-1,2-DCE and 1,2-DCA) was used for the experiment. The degree of dechlorination reached over 85 % 32 days after the application of μZVI in several samples and a far higher reaction rate for smaller particles was observed. Also, the amount of cis-1,2-DCE, which is characterized by slow decomposition, decreased by more than 95 % over the course of the experiment. Smaller particles showed a much longer sedimentation rate and gradual fractionation was also observed. Monitoring of ORP and pH also suggested that the smaller particles possessed a reduction capacity that was sufficiently high even at the end of the experiment. Laboratory tests with apparently similar μZVI samples indicated considerable differences in their reaction rate and efficiency.

Abstract

Amongst all of the reducing agents that can be used in environmental remediation, zero valent iron (ZVI) is one of the most common due to its environmental acceptance, high reaction rate, good availability, and long-term stability. Moreover, ZVI mobility, stability and reactivity can be enhanced by the application of a DC electric current, ie electrokinetics (EK). In the study, six various slurries containing different ZVI were tested for their efficacy for chlorinated ethenes and ethanes degradation. Chlorinated compound concentrations, pH, oxidation-reduction potential (ORP) and conductivity were determined during the long-term kinetic test. Kinetic rate constants calculated for the degradation of three chlorinated ethenes (PCE, TCE and cis-DCE) concluded that EK brings substantial contribution to chlorinated compounds degradation. Nano-scale zero valent iron STAR had the highest reaction rates compare to the other ZVI tested. The performed study could serve as a preliminary assessment of various available ZVI before in-situ application.