环境工程专业英语翻译

Electrodialytic Remediation of heavy Metal polluted Soil –treatment of

water saturated or suspended soil

Lisbeth.M. Ottosen, Pernille E. Jensen, Gunvor M. Kirkelund, Celia Dias- Ferreira, Henrik K. Hansen

Electrodialytic soil remediation is a method for removal of heavy metals. Good results have previously been obtained with both treatment of a stationary, water saturated soil matrix and with remediation of a stirred suspension of soil in water. The two different setups have different uses. The first as in-situ or on-site treatment when there is no requirement for fast remediation, as the removal rate of the heavy metals are dependent on the distance between the electrodes (everything else equal) and in such application the electrode spacing must have a certain distance (often meters). In the stirred setup it is possible to shorten the transport route to few mm and to have a faster and continuous process. The present paper for the first time reports a direct comparison of the two options. The remediation of the stirred suspension showed faster than remediation of the water saturated soil even without a short distance between the membranes. The acidification of the suspended soil was fastest and following the mobilization of heavy metals. This may indicate that water splitting at the anion exchange membrane is used more efficiently in the stirred setup.

1. Introduction

Heavy metals can be removed from polluted soil by application of an electric DC field and this forms the base for electrokinetic remediation (EKR) methods. Heavy metals are most often adsorbed to the soil particles or precipitated, and as the transport mechanism for heavy metals in the applied electric field is mainly electromigration (transport of ions in a liquid phase in a applied electric field), desorption of the heavy metals is crucial for a successful remediation. An acidic environment promotes desorption of heavy metals. During EKR the soil is acidified by electromigrating H+ ions from the anode reaction, and the heavy metals are subsequent mobilized and transported to the electrodes (positive ions towards the negative electrode and opposite). A comprehensive theoretical description of EKR can be found in (Yeung, 2006) and a review of results obtained with industrially polluted soil is given in (Ottosen et al., 2008).

A major advantage of EKR is the possibility to treat fine grained soils where mother methods tend to fail (Yeung, 2006).

Electrodialytic soil remediation (EDR) is one electrokinetic method for removal of heavy metals from soil (and particulate waste products). In EDR, ion exchange membranes are separating soil and processing solutions, while passive membranes are used in other EKR techniques. Remediation of suspended soil is possible when using ion exchange membranes, because they hinder direct mixing of ions from processing solutions and in the soil suspension. There are thus two options for application of EDR: (A) to treat the soil as a stationary, wet matrix (in-situ or on-site) or (B) to treat the soil in a suspension (with the possibility for combining EDR with soil washing and only