A Comparative Study on Heavy Metal Removal from CCA-Treated Wood Waste by Yarrowia lipolytica: Effects of Metal Stress.

Bioremediation is an effective way to remove heavy metals from pollutants. This study investigated the effects of Yarrowia lipolytica (Y. lipolytica) on the bioremediation of chromated copper arsenate (CCA)-treated wood wastes. Copper ions stressed the yeast strains to improve their bioremediation efficiency. A comparison of changes in morphology, chemical composition, and metal content of CCA wood before and after bioremediation was conducted. The amount of arsenic (As), chromium (Cr), and copper (Cu) was quantified by microwave plasma atomic emission spectrometer. The results showed that yeast strains remained on the surface of CCA-treated wood after bioremediation. The morphologies of the strains changed from net to spherical because of the Cu2+ stress. Fourier-transform infrared spectroscopy showed that carboxylic acid groups of wood were released after removing heavy metals. A large amount of oxalic acid was observed when the optical density (OD600nm) was 0.05 on the 21st day. Meanwhile, the highest removal rate of Cu, As, and Cr was 82.8%, 68.3%, and 43.1%, respectively. Furthermore, the Cu removal from CCA-treated wood increased by about 20% after Cu2+ stress. This study showed that it is feasible to remove heavy metals from CCA-treated wood by Y. lipolytica without destroying the wood structure, especially by copper-induced Y. lipolytica.

Synthesis and Characterization of Wood Rigid Polyurethane Composites.

Incorporating biodegradable reinforcement, such as wood particles, into rigid polyurethane foams (RPUFs) is among the alternatives to reduce their environmental impact. This study aims to assess the effect of different wood particles as reinforcement in RPUFs. Reinforced rigid polyurethane foams are synthesized with milled wood particles of various forms and sizes and commercial polyol and isocyanate. The effect of fiber treatments and mechanical stirring on foams' properties is also studied. Additional tests on polyisocyanurate foams (PIR) were undertaken to assess the effect of reinforcement on their properties. Mechanical properties are measured to investigate the impact of wood particle reinforcement on the foam. Confocal microscopy and Fourier-transform infrared spectroscopy (FTIR) showed the interaction between the wood fibers and the matrix. Despite the adhesion observed for some fibers, most of the cell walls of RPUFs were punctured by the rigid wood fibers, which explained the decrease in the compressive strength of the composites for manually mixed foams. Mechanical stirring proved to be an efficient method to enhance the reinforcement power of untreated fibers. RPUF foams' properties showed similar changes when untreated wood flour was introduced to the formula, increasing compressive strength significantly.

Copper-Doped Carbon Nanodots with Superior Photocatalysis, Directly Obtained from Chromium-Copper-Arsenic-Treated Wood Waste.

An ecofriendly approach was developed for preparing copper-doped carbon dots (CDs) with superior photocatalysis using chromium-copper-arsenic (CCA)-treated wood waste as a precursor. Original wood (W-CDs), CCA-treated wood (C-CDs), and bioremediation CCA wood (Y-CDs) were used as the precursors. The chemical composition and structural, morphological, and optical properties, as well as the photocatalytic ability of the synthesized CDs varied with wood type. The C-CDs and W-CDs had similar characteristics: quasispherical in shape and with a diameter of 2 to 4.5 nm. However, the Y-CDs particles were irregular and stacked together, with a size of 1.5-3 nm. The presence of nitrogen prevented the formation of an aromatic structure for those CDs fabricated from bioremediation CCA wood. The three synthesized CDs showed a broad absorption peak at 260 nm and a weak absorption peak at 320 nm. Proof of the model study for the fabrication of luminescent CDs from CCA wood waste for bioimaging was provided. The degradation rate of CD photocatalytic MB was 97.8% for 30 min. Copper doping gives the CDs electron acceptor properties, improving their photocatalytic efficiency. This study provides novel ways to prepare nanomaterials from decommissioned wood as a nontoxic and low-cost alternative to fluorescent dots.

Production, characterization, and potential of activated biochar as adsorbent for phenolic compounds from leachates in a lumber industry site.

There is growing interest in low-cost, efficient materials for the removal of organic contaminants in municipal and industrial effluents. In this study, the efficiency of biochar and activated biochar, as promising adsorbents for phenol removal, was investigated at high (up to 1500 mg L-1) and low concentrations (0.54 mg L-1) in synthetic and real effluents (from wood-residue deposits in Québec), respectively. The performance of both materials was then evaluated in batch adsorption experiments, which were conducted using a low solid/liquid ratio (0.1 g:100 mL) at different phenol concentrations (C0 = 5-1500 mg L-1), and at 20 °C. Activated biochars presented higher phenol adsorption capacity compared to biochars due to their improved textural properties, higher micropore volume, and proportion of oxygenated carbonyl groups connected to their surface. The sorption equilibrium was reached within less than 4 h for all of materials, while the Langmuir model best described their sorption process. The maximum sorption capacity of activated biochars for phenol was found to be twofold relative to biochars (303 vs. 159 mg g-1). Results also showed that activated biochars were more effective than biochars in removing low phenol concentrations in real effluents. In addition, 95% of phenol removal was attained within 96 h (although 85% was removed after 4 h), thus reaching below the maximum authorized concentration allowed by Québec's discharge criteria (0.05 mg L-1). These results show that activated biochars made from wood residues are promising potential adsorbent materials for the efficient treatment of phenol in synthetic and real effluents.

Composition, antimicrobial and antioxidant activities of seven essential oils from the North American boreal forest.

Essential oils (EOs) were steam-extracted from the needles and twigs of balsam fir, black spruce, white spruce, tamarack, jack pine and eastern white cedar that remained after logging in eastern Canada. These EOs, similarly to that from Labrador tea and other commercial EOs from Chinese cinnamon, clove and lemon eucalyptus, exhibited many common constituent compounds (mainly α-pinene, ß-pinene, limonene and bornyl acetate) making up 91% of each oil based on gas chromatography-mass spectrometry analysis. All of these oils exhibited antibacterial properties, especially when examined in closed tube assay compared to the traditional 96-well microliter format. These antimicrobial activities (minimum inhibitory concentration ≥ 0.2% w/v), comparable to those of exotic EOs, were shown against common pathogenic bacteria and fungi. The antioxidant potential of the boreal samples was determined by the 1,1-diphenyl-2-picrylhydrazyl radical scavenging (concentration providing 50% inhibition ≥ 7 mg/ml) and reducing power methods. Finally, this investigation revealed some boreal EOs to be potential antimicrobial and antioxidant agents that would notably benefit products in the personal hygiene and care industry.