Electrokinetic remediation of metal-polluted marine sediments: experimental investigation for plant design

Abstract

This paper presents the results of an extensive set of laboratory experiments performed to design a demonstrative electrokinetic plant for extracting heavy metals from marine sediments dredged from the Livorno marine harbour. The investigated sediments displayed a high salinity, a high acid neutralization capacity, a low electrical resistivity (0.5 Ωm), a high alkalinity (pH ≈ 8) and a large fraction of fine particles. The target metals were Cd, Cr, Cu, Ni, Pb and Zn at relatively weak and inhomogeneous concentrations with high non-mobile fractions. After an accurate characterization, several screening and full electrokinetic tests were performed using cells of two different sizes, several conditioning agents (HNO3, HCl, H2SO4, citric acid, oxalic acid, ascorbic acid, EDTA), different applied current intensities and durations. The tests highlighted the need for long treatment times in order to obtain a significant pH reduction, with some appreciable metal removal being attained only after several weeks. The best results were obtained with strong acids used as the conditioning agents, with significant specific effects of each acid, including pronounced resistivity increase (from 0.5 up to 10 Ωm) and a high electroosmotic flow (EOF) with H2SO4, or a reversed EOF (electroendosmosis), and minor resistivity changes with HNO3. The use of the obtained data to design a demonstrative plant is also presented in the paper, with considerations on operating parameters such as energy and reagent consumption, characteristics of plant components and required safety measures.\ud buffer capacity, conditioning agent

The influence of sediment properties and experimental variables on the efficiency of electrodialytic removal of metals from sediment

“…Metal partitioning of the targeted heavy metal in the individual models 2a-2c yield VIP values in the range 0.61-1.33, indicating that how the metals are chemically bound in the sediment highly influences the efficiency of EDR, building on previous findings of metal partitioning influencing the mobilisation of metals during electrokinetic remediation [44,45]. Coefficient plots of Cu removal (figure 8) reveals similar correlations in metal partitioning during all phases of EDR.…”

Electro-kinetic remediation coupled with phytoremediation to remove lead, arsenic and cesium from contaminated paddy soil

“…Acidification of soil pH was beneficial for solubilization and removal of metal(loid)s such as Pb, Cr, Cd, As, Cu and Zn (Altin and Degirmenci, 2005; Iannelli et al, 2015; Lu et al, 2012; Virkutyte et al, 2002). It was reported that the SOL Pb was dramatically increased in soil stimulated by EKF and the phytoremediation could remove 95% of Pb with the optimization of electrical field intensity and stimulation period (Yang and Lin, 1998).…”

Performance of electroremediation in real contaminated sediments using a big cell, periodic voltage and innovative surfactants

“…Considering its numerous applications both in the laboratory [32][33][34][35][36] as well as any attempt of pilot scale or scaling up [4,5,[37][38][39][40], EK appears to be one of the most sufficient and cost-effective alternatives for treating, even, real sediments (dredged or surficial) which often come with the simultaneous presence of multiple contaminants which interact with the constituents of solid matrices, thereby creating other compounds that limit and/or incommode even more the EK process. However, when all contaminants and/or substances are dissolved, they are, then, easily transported (flushed) into the electrolyte chambers, thus obtaining their desirable removal from the polluted soil/sediment sample.…”