Electrodialytic Remediation of an Arsenic and Copper Polluted Soil - Continuous Addition of Ammonia During the Process

Abstract

Abstract Soil polluted by the wood preservation industry is a serious problem affecting both site use and groundwater quality. The sites are often polluted with copper, chromium and arsenic. Experiments with electrodialytic remediation of soil polluted with Cu (805 mg kg−1) and As (900 mg kg−1) from wood preservation have been made. During the remediation process the soil becomes acidified and an experiment showed that due to this acidification As was not removed from the soil probably because As was mainly present as uncharged species. Cu was removed to a level of less than 50 mg kg−1 in this case. In order to remove As and Cu at the same time ammonia was added to the soil. Ammonia causes the soil to be alkaline and As is mainly present as negatively charged species in the alkaline environment and thus As is mobile in the electric field. Cu can form charged complexes with ammonia and is thus mobile in the electric field, too. The addition of ammonia was tested in three experiments under the same conditions except for the amount of charge passed through the soil. The lowest concentration obtained for As was 90 mg kg−1. The Cu removal was not as efficient using ammonia as in the experiment with the acidified soil. Although Cu was nevertheless removed to a level of about 370 mg kg−1 which is an acceptable concentration. The results confirmed the expectations. As and Cu was removed at the same time. Keywords: Soil remediationelectrokineticsion exchange membraneswood preservation sites