SELECTED ASPECTS OF REMEDIATION OF HEAVY METAL-CONTAMINATED SOIL AND OPTIMIZED TREATMENT OF HEAVY METAL CONTAMINATED WASTE WATER

摘要

In the first part of the paper we report about a successful remediation of heavy metal-contaminated soil in Germany in the laboratory scale by means of citric and tartaric acid. Heavy metal-contaminated soil material is encountered in many existing or former industrial areas. In by far most cases the heavy metals are neither chemically immobilised nor physically encapsulated.. As a consequence, the heavy metals present a problem for groundwater and/or drinking water. In the investigations presented in this paper natural complexing agents like tartaric and citric acid, respectively, have been applied. Both chemicals are available in large amounts and to various degrees of purity. Furthermore both acids and their heavy metal complexes are biodegradable (1, 2). The basic concept of a process using tartaric or citric acid is an on-site treatment in a reactor. By this mean there is a controlled elution and any direct impact on the natural environment is avoided. The first step consists of an elution followed by a separation of metal species by means of ion exchangers. After compensating for losses of complexing agents the liquid phase can be recycled. The heavy metals might be removed from the spent regenerant of the ion exchange resins, e.g. by electrolysis, if the concentrations are high enough and the recovery is economic (3, 4). Otherwise they have to be precipitated by standard methods.