Enhanced Electrokinetic Remediation of Heavy Metals in Glacial Till Soils Using Different Electrolyte Solutions

Abstract

Previous electrokinetic remediation studies involving the geochemical characterization of heavy metals in high acid buffering soils, such as glacial till soil, revealed significant hexavalent chromium migration towards the anode. The migration of cationic contaminants, such as nickel and cadmium, towards the cathode was insignificant due to their precipitation under the high pH conditions that result when the soil has a high acid buffering capacity. Therefore the present laboratory study was undertaken to investigate the performance of different electrolyte ͑or purging͒ solutions, which were introduced to either dissolve the metal precipitates and/or form soluble metal complexes. Tests were conducted on a glacial till soil that was spiked with Cr͑VI͒, Ni͑II͒, and Cd͑II͒ in concentrations of 1,000, 500, and 250 mg/kg, respectively, under the application of a 1.0 VDC/cm voltage gradient. The electrolyte solutions tested were 0.1M EDTA ͑ethylenediaminetetraacetic acid͒, 1.0M acetic acid, 1.0M citric acid, 0.1M NaCl/0.1M EDTA, and 0.05M sulfuric acid/0.5M sulfuric acid. The results showed that 46-82% of the Cr͑VI͒ was removed from the soil, depending on the purging solution used. The highest removal of Ni͑II͒ and Cd͑II͒ was 48 and 26%, respectively, and this removal was achieved using 1.0M acetic acid. Although cationic contaminant removal was low, the use of 0.1M NaCl as an anode purging solution and 0.1M EDTA as a cathode purging solution resulted in significant contaminant migration towards the soil regions adjacent to the electrodes. Compared to low buffering capacity soils, such as kaolin, the removal of heavy metals from the glacial till soil was low, and this was attributed to the more complex composition of glacial till. Overall, this study showed that the selection of the purging solutions for the enhanced removal of heavy metals from soils should be primarily based upon the contaminant characteristics and the soil composition.

Ammonium citrate as enhancement for electrodialytic soil remediation and investigation of soil solution during the process

“…Even though Cr is mainly removed to the anode side in these experiments (table 4), the concentration profiles clearly show that transport towards the cathode also takes place. Migration of Cr(III) towards the cathode has also been found in previous works (Buchireddy et al, 2009;Reddy and Chintamreddy, 2004) in parallel with decreasing pH. In our experiments the original soil pH is 7-7.8, and final values are 8-9, so no acidification occurs.…”

“…Removals are nevertheless the highest reported in the literature so far, for a real Cu and Cr-contaminated calcareous soil (Ottosen et al, 2005b). Buchireddy et al (2009) and (Reddy and Chintamreddy, 2004) report higher Cr-removals (72% and 46-82%, respectively) with an artificially spiked soil, but these cannot be compared with our results, where contamination dates back to the 1960's . These results are encouraging and highlight the potential of EDR to remediate soils which are contaminated with a mixture of heavy metals at a neutral pH by choosing a good enhancement solution.…”

Pilot-scale ex situ electrokinetic restoration of saline greenhouse soil

“…However, these are only temporary solutions. Recently, electrokinetic (EK) treatment has been used as a method to remediate or control various contaminated media such as soils (Kim et al 2009a(Kim et al , 2009bOttosen et al 2006;Reddy and Chinthamreddy 2004;Reddy et al 2001;Ryu et al 2010;Zhou et al 2004), mine tailings Hansen et al 2005;Kim et al 2002a;Ryu et al 2009), and sludge (Kim et al 2002b;Park et al 2010). The major mechanisms responsible for the removal of contaminants in the EK treatment process are electromigration and electroosmosis (Acar and Alshawabkeh 1993;Acar et al 1995).…”

[Preprint] An overview of electrokinetic soil flushing and its effect on bioremediation of hydrocarbon contaminated soil

“…Faradic reaction will also occur on the surface of clay particles where DDL will become micro-"anode" and "cathode" so oxidation-reduction process can occur. The higher the concentration of electrolyte, the greater the possibility of oxidation process happen Cameselle, 2015;Reddy and Chinthamreddy, 2004;Yeung and Gu, 2011).…”

“…This biodegradation occurs on clay surface and corresponds to electrokinetic transformation process. Several researchers have suggested that the application of electric fields can increase the production of ATP in order to improve the performance of cells in consuming hydrocarbon compounds (Reddy and Chinthamreddy, 2004;Yeung and Gu, 2011).…”