N28

Electrochemical Remediatlon Tekea to the Field

Jeanne Trombly reports on the March workshop at the Electnc Power Research Institute (EPRI) In Palo Alto, CA, In Envrron-

mental Science and Technology More than 60 representattves of the pnvate and publtc sectors dlscussed the use of elec- tric currents to clean contamrnated soils

and groundwater in situ Although electro- chemical remedratron generally IS skII In rts

infancy, Wefal presentations suggested that the process IS inching toward com- merciallsatton In certain applicatrons in the removal of inorganic contaminants

Approximately none field demonstra- tions are being launched in the Untted

States thre summer to analyze the effec- trueness of electroremediatron in treating a wldevanety of pollutants The field demon- strations follow on the heels of laboratory tests in which scientists reported having achieved removal efficiencies ranging from 44% to 99% for a wide variety of contaminants, including sulfates, nrtrates, chromium, uranium, mercury, soluble or- ganics such as phenol and benzene-to- luene-xylene, and polycycl~c aromatic hy- drocarbons

Electrochemrcal remediation has gar- nered considerable interest from US sclen- tists and business representatives be- cause rt isthe only in SW method that could work in low-permeability clays and silt- laden so& - condrtions that charactense et least half of the toxic waste sites in the country “Except for soil vapour extraction, which works only on certain contaminants in unsaturated SOIIS, in srtu remediatron technologies are for the most part only in the development stage”

Some researchers reported costs of $90-!6130 per ton, which are comparable

to, if not lower than, conventional remedt- ation methods

In Europe, Geokrnetics IS currently stripping mixed toxic metals from Rhrne sludges in Rotterdam, one of Europe’s most environmentally damaged manufac- tunng areas

Electrochemical remediatron IS charac- tensed by electromrgratron, electroos- most-s and, less commonly, electro- phoresls Electromlgratron IS the move- ment of ions In an electnc field from one electrode to another Because most or- ganics are not ionised, this process works primarily on highly soluble ronlsed rnor- ganics including alkalr metals, chlorides,, nitrates, and phosphates In morst so11 en- vironments Adddronally, heavy metals

such as lead, mercury, cadmium, and chromium have responded favourably, some wrth the aid of complexrng agents Most electromigratron tests have taken place in low-permeabrltty, nearly saturated soils Dry soils, however, require more electncrty, which IS likely to increase re- mediation costs

Electroosmosls IS the other primary transport mechanism whereby water moves through charged soil Electroos- mosls works efficiently only with fine-

grained soils and clays The process has shown good results In removing soluble organics Even though Insoluble organlcs such as heavy hydrocarbons pose more of a challenge for electroosmosls, Slbel Pamukcu, professor at Lehigh Unrverslty (Bethlehem, PA), reported removal effl- ciencies of 44 to 70% for some compo- nents of coal tar-contaminated soil wrth the aid of surfactant Injectron

[Source Environ SCI Technol , 28 (6) (1994) 289A]

applied catalysis 6. environmental Volume 4 No 4 - 8 November 1994