Integration of emulsified nanoiron injection with the electrokinetic process for remediation of trichloroethylene in saturated soil

The objective of this research was to evaluate the treatment efficiency of a trichloroethylene (TCE)-contaminated soil by combined processes of the injection of emulsified nanoscale zero-valent iron (ENZVI) and electrokinetic (EK) remediation. In this work nanoiron (30–50 nm) was synthesized using the chemical reduction method employing industrial grade chemicals and characterized using various analytical instruments. The thus-prepared nanoiron pulp, soybean oil and mixed surfactants (Span 80 and Tween 40) were then used to prepare ENZVI. This study further evaluated the treatment efficiency of combining ENZVI and EK in remediating a TCE-contaminated sandy soil. Experimental conditions were as follows: (1) initial TCE concentration in the range of 95–119 mg/kg; (2) an electric potential gradient of 1 V/cm; (3) a daily injection of 20 mL ENZVI into an electrode reservoir; and (4) a treatment time of 10 days. Experimental results have shown that electroosmotic flow played a key role in removing TCE from the soil matrix to the cathode reservoir. Therefore, injection of ENZVI into the cathode reservoir would enhance the degradation of TCE therein. The integrated technology was capable of remediating TCE-contaminated soil to meet Taiwan EPA's Soil Pollution Control Standard of 60 mg/kg for TCE.

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► This paper reports the performance evaluation and its findings of using combined processes of the injection of emulsified nanoscale zero-valent iron (ENZVI) and the electrokinetic (EK) process for remediation of trichloroethylene (TCE)-contaminated soil.
► ENZVI was prepared using laboratory-synthesized nanoiron, soybean oil and mixed surfactants (Span 80 and Tween 40).
► It was found that injection of ENZVI into the cathode reservoir would enhance the degradation of TCE therein. Under the conditions employed in this work, the residual TCE concentration in soil met Taiwan EPA's Soil Pollution Control Standard of 60 mg/kg for TCE.