Electrodialytic remediation of soil slurry-removal of Cu, Cr, and As

• Severe soil contamination is often found at old wood preservation sites and a common combination of pollutants is Cu, Cr, and As. In the present work it is tested if simultaneous removal of Cu, Cr, and As can be obtained in an electrodialytic cell where the polluted soil is remediated as a stirred suspension (placed as the desalination compartment in accordance to the position of the ion exchange membranes). The soil for the experiments was sampled at an abandoned wood preservation site and contained 2170mg Cu/kg, 710mg Cr/kg and 3200mg As/kg. SEM-EDX analysis showed that Cu, Cr, As and oxygen formed particles that were cementing soil minerals together. The soil was suspended in distilled water, distilled water with I2 crystals to have an oxidizing environment, or in an acidified environment at pH about 1.0. The experiments lasted from 1 to 3 weeks. Good results were obtained in two experiments; an experiment where the soil was suspended in distilled water and the remediation lasted 3 weeks with 2.5mA and an experiment with acidification of the soil suspension with HNO3 to pH about 1.0 (2 weeks and 5mA). The best separation of pollutants and soil was obtained in the experiment with suspension in distilled water. Based on soil concentrations, good Cu removal (95%) was obtained in both experiments. Removal of Cr was most efficient from the acidified soil suspension (74%). Both Cu and Cr concentrations were below the limiting values after the remediation. The As concentration, however, was not even although 61% was removed. In the soil remained about 1070mg As/kg soil and since the limiting value is 40mg As/kg, the removal was not efficient enough. So simultaneous removal was possible, but the target values were only met in the case of Cu and Cr, and more research is needed to remove As to a sufficiently low concentration, as well.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Electrokinetics

electromigration

heavy metals

soil pollution

wood preservation

Chemistry

Kemi

Chemistry

Kemi

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vet (ämneskategori)

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