SITE REMEDIATION AND
EMERGENCY RESPONSE NEWSLETTER

November 2011

No. 158

Slovenia – Partners Sought for Commercializing New Technology to Remediate Soil and Sediment Contaminated by Metals

Slovene SME has developed a new technology for the remediation of metals-contaminated soil and sediment. The technology includes the on-site washing of soil or sediment, the recycling of processed water and the recycling of the chelating agent ethylenediamine tetraacetate (EDTA).  In addition, the company provides laboratory and pilot scale feasibility tests to find the optimal remedial solution for a given contaminated site.

Slovene SME is seeking partners from industry and municipalities to commercialize its technology.

The company says that for most types of contaminated soils and sediments, the removal of toxic metals with the chelating agent ethylenediamine tetraacetate (EDTA) is the most efficient remediation technique. EDTA desorbs toxic metals from soil solid phases by forming strong and water-soluble metal-chelant complexes. Following an initial screening of the excavated soil to remove the surface debris, the soil is vigorously mixed with the EDTA solution, separated by filtration and then returned to the ground. Spent washing solution is electrochemically treated for EDTA, and process water is recovered and reused in a closed cycle. The technology is developed as a prototype plant.

Toxic wastewaters generated during soil extraction and containing complex EDTA cannot be treated using conventional methods, such as filtration, flocculation, or precipitation. Other approaches have been demonstrated, but they are not practical and commercially available, according to Slovene SME. These include reverse osmosis (the soil particles tend to clog the membranes); separation of the EDTA anion using an anion exchange resin (expensive resin, recycling not practical); zero-valent bimetallic mixtures (Mg0-Pd0, Mg0-Ag0) precipitate Pb from EDTA in alkaline pH (economically prohibitive); separation of Pb from EDTA with Na2S recovers metals through precipitation as sulphides (the sludge produced is toxic); substitution of Pb with Fe3+ followed by Pb precipitation with phosphate and (at high pH) Fe3+ as hydroxides liberates EDTA (high reagent consumption); electrolytic recovery of metals and EDTA in a two-chamber cell separated with a cation exchange membrane (membrane fouling and degradation).

Electrochemical recovery and reuse of EDTA and process water from the spent solutions is new in soil remediation technology. Slovene SME says that it is the only company offering soil washing based on the chelating agent EDTA. 

Back To Site Remediation and Emergency Response No. 158