Thermal decontamination of railway sleepers for recycling. Removal of creosote oil

Because of the high content of PAHs (polyphenolic aromatic hydrocarbons) in wooden railway sleepers, legislative regulations require the thermal combustion of the sleepers after removal from the track bed or permit an altemate usage only in a limited frame. Decontamination experiments were performed by means of temperature and reduced pressure in technical scale, aiming on the removal of the PAHs from used railway sleepers in order to provide alternative ways for recycling of the wood tissue. Both railway sleepers as well as uniform laboratory samples were treated, and subsequently investigated by liquid extraction and liquid injection gas chromatography-mass spectrometry (GC-MS). The decontamination treatment at a temperature of 220°C removes up to 75% of PAHs, main active substances of the creosote oils. For complete PAHs removal, process parameters need to be further improved.