Characterization of the effluents condensated by volatile organic compounds during heat-treated rubberwood process

Heat treatment was an eco-friendly modification technology for rubberwood, without the addition of chemical reagents into the wood and wood performance has been improved remarkably. Many effluents are generated from heat-treated rubberwood process, which were rarely researched. The effluents contain relatively high content of volatile organic compounds, which may seriously threaten the environment and human health. In this study, effluents condensated during different heat-treated stages (125 ℃, 145 ℃, 175 ℃, 185 ℃, 215 ℃) and frequently used industrial heat treatment production technology (185 ℃/3 h, 215 ℃/3 h) were characterized by gas chromatography–mass spectrometry (GC–MS). The effluents were classified as aldehydes, phenols, esters, ketones, acids, alcohols, alkanes, anhydride, aromatics and compounds released the most during all heat-treated stages were aldehydes. With the temperature increased, the relative amounts of aldehydes decreased, while the ketones, esters and aromatics increased under acidic constituents (pH ranged from 4.17 to 2.47) and high moisture condition. The vanillin and coniferyl aldehyde accounted for much higher proportion in the aldehydes. The mass loss of rubberwood was larger under 215 ℃/3 h (16.61%), correspondingly the effluents had more kinds of compounds at 215 ℃. These results would provide guidance for research of effluent disposal and transform biomass residues into valuable things.