Effectiveness of soil washing, nanofiltration and electrochemical treatment for the recovery of metal ions coming from a contaminated soil

The remediation of heavy metals contaminated sediment

“…This technology is most appropriate for the weaker bound metals in the form of exchangeable, hydroxides, carbonates and reducible oxides fraction. Residual fractions, the most difficult ones to remove, are not affected during the washing process [38,39]. Additionally, fine grain sediments are difficult to decontaminate through washing solutions, therefore washing is most applicable to sands and gravels.…”

Extraction behavior of As, Pb, and Zn from mine tailings with acid and base solutions

“…With sulfuric acid, the amount of lead dissolution decreased with an increase in acid concentration. Because the lead forms insoluble PbSO 4 in the presence of SO 4 2− , an increase in the acid concentration led to the formation of PbSO 4 precipitants. Though PbSO 4 is an insoluble precipitant, some amount of it is dissolved in a strong acid solution.…”

“…These methods are not a permanent treatment method because (a) continuous monitoring is needed, (b) the metals are not removed from the soil, and (c) the longterm stability of the solidification/stabilization is questionable [3]. The alternative technologies (in opposition to conventional options based on ex situ stabilization/solidification and off-site disposal) mostly selected for treating metal-contaminated soils and mine tailings include: (1) metal extraction techniques such as soil washing, phytoextraction, and electrokinetic remediation; (2) in-situ metal immobilization techniques such as phytostabilization and in situ bio-chemical fixation/stabilization (soil amendments with inorganic and organic compounds) [4][5][6][7]. Among these alternative technologies, a wide array of physical, chemical or biological techniques of soil washing processes have been evaluated and successfully used in numerous field-scale remediation projects for permanently removing the metals from contaminated soils [3][4][5][6][7].…”

“…The alternative technologies (in opposition to conventional options based on ex situ stabilization/solidification and off-site disposal) mostly selected for treating metal-contaminated soils and mine tailings include: (1) metal extraction techniques such as soil washing, phytoextraction, and electrokinetic remediation; (2) in-situ metal immobilization techniques such as phytostabilization and in situ bio-chemical fixation/stabilization (soil amendments with inorganic and organic compounds) [4][5][6][7]. Among these alternative technologies, a wide array of physical, chemical or biological techniques of soil washing processes have been evaluated and successfully used in numerous field-scale remediation projects for permanently removing the metals from contaminated soils [3][4][5][6][7]. In recent years, attention has focused on the development of in situ alternative methods (such as phytoremediation, in situ chemical stabilization, bioremediation and soil flushing) that are generally less expensive and disruptive than conventional excavation, treatment and disposal methods [8].…”

“…In recent years, attention has focused on the development of in situ alternative methods (such as phytoremediation, in situ chemical stabilization, bioremediation and soil flushing) that are generally less expensive and disruptive than conventional excavation, treatment and disposal methods [8]. However, the soil washing via chemical extraction methods presents several advantages compared to in situ immobilization and phytoremediation techniques: (1) the rapid revitalization of the site since the contaminated materials are excavated; (2) the short duration of the soil washing process; (3) the volume reduction of contaminated soil; (4) the possibility of metal recovery by extracting the dissolved metals from the washing effluents [3,4]. The migration of metals from soil to aqueous solutions occur by (a) changes in the pH, (b) changes in the ionic strength, (c) changes in the redox potential, and (d) the formation of complexes, and (e) the ligands/ions exchange reactions [3,9].…”