Hydrothermal treatment of mixed preservative-treated wood waste.

AbstractThis paper describes the hydrothermal treatment (HT) treatment of a mixture of samples treated with three wood preservatives. During HT treatment, creosote-derived hydrocarbon (HC) residues were recovered in the decommissioned treated wood and the wood mass itself was transformed with 95% yield into a mixture of HCs, including substituted benzenes, phenolics and light polyaromatic HCs (PAHs). The metals from the CCA-treated wood were partially recovered (up to 48–88%) either in an acidified AQ phase or as a coating on the internal walls of the reactor. Some arsenic was probably transformed to arsine gas, which could be trapped and recovered under basic conditions. Pentachlorophenol was dechlorinated and removed to below detection limits. The HT process also resulted in the generation of industrially useful mixed HCs with substantial reduction in substrate mass. Thus, the preservative-treated wood as a hazardous waste was transformed into a complimentary mixture of liquid products. Creosote and CCA were recovered, and penta was degraded. It is important to note that this work was performed in large reactors, which were heated with hot air in a muffle furnace. Hence, the incubation time was long. Our current work with small reactors heated instantaneously in tin baths to 400°C has confirmed that HT reactions occur in the order of seconds to minutes. Future publications will address kinetic and mechanistic aspects of these reactions. [ABSTRACT FROM AUTHOR]