Extraction efficiency of chloroethenes from contaminated dry cleanerʹs sludge with three different methods

The three most easily available extraction methods were compared to study the binding effect of chloroethenes (chloroethylenes) to a sludge sample. First, the chlorinated ethenes were extracted from the sludge sample with a Soxhlet method using either an acetone–hexane mixture or tetrahydrofuran (THF). Second, simultaneous distillation–extraction with an iso-octane–water mixture was applied. Finally, the influence of basic hydrolysis on the release of organic chlorines by the simultaneous distillation–extraction procedure was investigated. The identified composition of the extractable organic chlorine (EOCl) was tetrachloroethene, trichloroethene, 1,1-dichloroethene and cis-1,2-dichloroethene. Total chlorine contents of the different samples were determined by a burning method in a steel container with excess oxygen pressure. The recovery of the samples treated with the simultaneous distillation–extraction method was definitely greater than that of the Sohxlet. The results proved that a significant part of chloroethenes was unusually strongly bound to the sludge matrix and basic hydrolysis was required to release the bound chloroethenes from the matrix almost completely. However, the operation with a too high base concentration leads to unwanted side-reactions causing analytical difficulties. It is recommended to use THF as a solvent by applying the Soxhlet extraction to obtain better recoveries.