SUPERCRITICAL CO_2 IS A TOOL FOR NATURAL MATERIAL TREATMENTS

摘要

The Supercritical Fluids and Membranes Laboratory studies the Supercritical Carbon dioxide (SC CO_2) potential for both organic and/or inorganic compound extraction and permeation. First of all, the laboratory has developed a method for extracting inorganic and organic compounds, from wood (timbers, electric poles... recycling) using SC CO_2. The extracted inorganic compounds are CCA (compounds of chromium, copper and arsenic) whose extraction is rendered possible by adding a surfactant ; organic compounds extraction of PAH (Polycyclic Aromatic Hydrocarbons) has been also performed. The laboratory has developed, a new hazard-free process for cork treatment and cleaning, using SCCO_2. This process allows to extract all the undesirable organic compounds (polychloroanisols are responsable of 'cork taint'), maintaining all the chemical and physical properties of the cork for wine sealing bottles. SCCO_2 is both efficient to remove contamination in the range from 1 to 10 mg/g in wood treatment and in the lower range from 1 to 10 ng/g in cork treatment. Secondly, SCCO_2 has been used for permeation on collapsed archaeological waterlogged wood. The collapses have been considered as irreversible damage, with volume loss, distortions and cracks. Several works have been done with polyethylene glycol (PEG) permeation and we have used PEG with SCCO_2 to decrease the viscosity. It is possible to recover a part of the initial volume by mechanical effect produced by fast compression/decompression. The laboratory has also developed an original process for leather tanning with chromium salt permeation by SCCO_2. The supercritical fluid shows a high density to transport chromium to leather contact. The affinity of the chromium salts is higher for leather than CO_2: this induces a successful permeation and aqueous waste-less. SCCO_2 processes demonstrate today a versatility and a sustainable potential for natural product treatments.