Wood dimensional stability enhancement by multivalent metal-cation-induced lignocellulosic microfibrils crosslinking.

Wood is a hygroscopic material that responds to the moisture changes of the surrounding environment through swelling and shrinkage, making it dimensionally unstable. Here, we introduce a facile metal-ion-modification (MIM) approach to enhance the dimensional stability of wood. The MIM process involved swelling the wood samples with aqueous metal ion solutions and drying. The high valent metal cations, such as Fe3+, Al3+, and Zr4+, interacted with the hydrophilic groups (e.g., OH, COOH) present in the wood fibers, limiting their access to water and moisture, thereby enhancing the wood's hydrophobicity and dimensional stability. Evaluation of three wood species, southern yellow pine, poplar, and red oak, revealed water contact angles of 120-130° after MIM, indicative of enhanced surface hydrophobicity. Fe3+ treatment decreased southern yellow pine's swelling ratio from 6 % to 4 %. Fe3+-treated wood exhibited tangential anti-swelling efficiencies ranging from 39.83 % to 57.14 % and radial anti-swelling efficiencies from 34.74 % to 48.33 %, varying across wood species. The enhancement of wood dimensional stability can be attributed to the formation of irreversible coordination bonds between metal cations and lignocellulosic microfibrils in the wood cell wall. These bonds prevent the microfibrils from slipping in response to moisture absorption and desorption.

Fast Pyrolysis Bio-Oil-Based Epoxy as an Adhesive in Oriented Strand Board Production.

The objectives of this study were to utilize bio-oil-based epoxy resin in oriented strand board (OSB) production and investigate the effect of bio-oil substitution in epoxy resin as an adhesive for OSB production. Bio-oil was produced by the fast pyrolysis (FP) process using southern yellow pine (Pinus spp.). Bio-oil-based epoxy resin was synthesized by the modification of epoxy resin with FP bio-oil at various substitution levels. Acetone extraction using a Soxhlet process indicated a superior cured reaction of bio-oil and epoxy resin at 20% bio-oil substitution. FTIR spectra corroborated the Soxhlet extraction with the removal of the epoxide peak signature within the cross-linked polymer. Images from the scanning electron microscopy suggested bulk phase homogeneity. OSB panels were tested according to ASTM D1037-12. The modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, and water resistance (thickness swell and water absorption) properties of the OSB panels were feasible at bio-oil substitution up to 30% in the epoxy resin system.

Effects of Loblolly Pine Biochar and Wood Vinegar on Poultry Litter Nutrients and Microbial Abundance.

Biochar, wood vinegar, and poultry litter are waste streams that can be utilized as soil amendments and fertilizers. However, poultry litter releases several pollutants through nutrient leaching and carries heavy microbial loads, including potential human pathogens. Improving nutrient retention and reducing microbial load in poultry litter may help protect environmental and human health and improve its value as a soil amendment. The objectives of this study were to determine how blending varying proportions of loblolly pine (Pinus taeda L.) biochar, wood vinegar, and poultry litter affected nutrient profiles and microbial abundance over time. Biochar inclusion rates were 0%, 5%, 10%, and 20%, and wood vinegar was applied at 2% w/w. Samples were taken at Day 0, 57, and 112 to measure nitrogen, phosphorus, potassium, pH, total fungi, and total bacteria. Nutrient levels generally decreased with increasing biochar level; however, biochar inclusion rates of 10% and 20% retained nitrogen and phosphorus and exhibited improved physical properties. Overall, adding wood vinegar decreased nutrient concentrations and showed a biocidal effect for bacteria and fungi. Bacteria and fungi showed different relationships with biochar inclusion rates, with fungi preferring higher biochar inclusion rates and bacteria flourishing at lower biochar inclusion rates.

Surface Properties of Organic Kerogen in Continental and Marine Shale.

The adhesion energy of kerogen in continental and marine shale was innovatively discovered using the colloid probe technique with atomic-force microscopy (AFM). AFM results indicated that the adhesion force of kerogen was higher than the inorganic material in both the continental and marine shale samples. The chemical elements in the two kinds of samples were measured by energy-dispersive X-ray analysis with scanning electron microscopy (SEM). The chemical compositions of kerogen involved C═C bonding, C═O bonding, pyridine nitrogen, and pyrrole nitrogen, whereas the primary constituent involving inorganic matter was Si-O bonding. These results were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The high percentages of C═C and C═O bonding in kerogen are attributed to the large dipole on the kerogen surface which allowed kerogen to contain liquid and gaseous hydrocarbons.

Tough Reversible Adhesion Properties of a Dry Self-Cleaning Biomimetic Surface.

Geckos have one of the world's most efficient reversible adhesion systems. Even walking in dusty conditions, geckos can dislodge up to 80% of contaminants and recover their adhesion capability after walking as few as four steps. Thus far, artificial dry self-cleaning materials inspired by the geckos' hierarchical fibrillar structure have been only able to remove 55% of collected large particle contaminants with 30 steps. Challenges, including low mechanical strength, low stiffness, and short fatigue time keep these materials from being used in practical applications. This study involves the novel fabrication of dry self-cleaning surfaces with a high mechanical performance and an outstanding dry self-cleaning property. Imposing a load-drag-pull process similar to a gecko's foot adhesion process, our biomimetic surfaces could dislodge up to 59% of microparticles (∼8 µm) with as few as five steps. Furthermore, the surface had an excellent screening ability at low temperatures regardless of the surface roughness similarity. The surfaces were also proven to be scratch resistant. The biomimetic surfaces exhibit enhanced dry self-cleaning and mechanical properties and could be promising in applications such as reusable adhesives, biochips, aerospace satellite waste collection, and screening equipment.

Sulfur resistance of Ce-Mn/TiO2 catalysts for low-temperature NH3-SCR.

Ce-Mn/TiO2 catalyst prepared using a simple impregnation method demonstrated a better low-temperature selective catalytic reduction of NO with NH3 (NH3-SCR) activity in comparison with the sol-gel method. The Ce-Mn/TiO2 catalyst loading with 20% Ce had the best low-temperature activity and achieved a NO conversion rate higher than 90% at 140-260°C with a 99.7% NO conversion rate at 180°C. The Ce-Mn/TiO2 catalyst only had a 6% NO conversion rate decrease after 100 ppm of SO2 was added to the stream. When SO2 was removed from the stream, the catalyst was able to recover completely. The crystal structure, morphology, textural properties and valence state of the metals involving the novel catalysts were investigated using X-ray diffraction, N2 adsorption and desorption analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive spectroscopy, respectively. The decrease of NH3-SCR performance in the presence of 100 ppm SO2 was due to the decrease of the surface area, change of the pore structure, the decrease of Ce4+ and Mn4+ concentration and the formation of the sulfur phase chemicals which blocked the active sites and changed the valence status of the elements.

Photoluminescence mechanism and applications of Zn-doped carbon dots.

Heteroatom-doped carbon dots (CDs) with excellent optical characteristics and negligible toxicity have emerged in many applications including bioimaging, biosensing, photocatalysis, and photothermal therapy. The metal-doping of CDs using various heteroatoms results in an enhancement of the photophysics but also imparts them with multifunctionality. However, unlike nonmetal doping, typical metal doping results in low fluorescence quantum yields (QYs), and an unclear photoluminescence mechanism. In this contribution, we detail results concerning zinc doped CDs (Zn-CDs) with QYs of up to 35%. The zinc ion charges serve as a surface passivating agent and prevent the aggregation of graphene π-π stacking, leading to an increase in the QY of the Zn-CDs. Structural and chemical investigations using spectroscopic and first principle simulations further revealed the effects of zinc doping on the CDs. The robust Zn-CDs were used for the ultra-trace detection of Hg2+ with a detection limit of 0.1 µM, and a quench mechanism was proposed. The unique optical properties of the Zn-CDs have promise for use in applications such as in vivo sensing and future phototherapy applications.

Multicolor carbon nanodots from food waste and their heavy metal ion detection application.

Multicolor carbon dots (C-dots) have excellent performance characteristics, high photoluminescence efficiency, ease of fabrication and low toxicity. C-dots have been used in a wide variety of fields including bioimaging, biomedicine, photocatalysis and environmental monitoring. The mass production of multicolor CDs using low-cost, facile methods is an important issue for future industrial applications. In this article, we reported a simple and highly effective way to prepare the multicolor C-dots and use them to detect heavy metal iron ions. Hydrochar acquired from food waste processed with hydrothermal carbonization (HTC) was used as the carbonaceous material for this process. Four colors of C-dots were obtained and included blue, green, yellow and red. These multicolor C-dots could be used as fluorescence probes with unique selectivity to detect the Fe3+ ion. The luminescence response ranged from 1 to 50 µM with a correlation coefficient of 0.9968. This discovery not only shows the high value-added products which can be obtained from food waste but can also lead to new developments in carbonaceous materials which can be used as "green resources".

Formation and Regeneration of Shape-Selective ZSM-35 Catalysts for n-Butene Skeletal Isomerization to Isobutene.

Skeletal isomerization of n-butene to isobutene was performed over formed ZSM-35 zeolites in a lab-scale, fixed-bed reactor. The formation conditions to produce isobutene with zeolites were varied to determine the most advantageous binding agent (pseudo-boehmite) amount and steam dealumination conditions. The optimal binding agent amount was 20 wt %. Steam dealumination stabilized the catalysts and enhanced the catalytic performance because of the stable Si/Al framework and suitable acidity. The optimized process conditions involved a reaction temperature of 410 °C, a weight hourly space velocity of 5 h-1, and an n-butene concentration in feedstock of 50%. After being on-stream for 296 h, the catalysts were stable and were able to be regenerated with a comparable catalytic performance. An isobutene yield of 33-43 wt % was achieved, and the selectivity of isobutene was higher than 90% after the reaction was carried out for longer than 15 h. Carbon deposition modified the pore structure to enhance the selectivity of isobutene because of the selective shape effect. This study shows promising results for future industrialization of the skeletal isomerization of n-butene to isobutene in the presence of optimized ZSM-35 catalysts.

Effects of Surface Functionalization of Lignin on Synthesis and Properties of Rigid Bio-Based Polyurethanes Foams.

We report the preparation of lignin-based rigid polyurethane (RPU) foams from surface functionalized kraft lignin via a simple and environmentally benign process. Lignin was functionalized with polyisocyanate at 80 °C for 1 h, the resulting lignin-polyisocyanate prepolymer was confirmed by increased viscosity and Fourier-transform infrared spectroscopy (FTIR). The RPU foams containing up to 30% surface functionalized lignin as a substitute for petroleum-based polyols exhibited comparable thermal and mechanical properties to conventional RPU foams. The lignin-based RPU foams prepared from surface functionalization outperformed RPU foams without the surface functionalization, showing up to 47% and 45% higher specific compressive strength and modulus, respectively, with a 40% lignin substitution ratio. Thermal insulation and temperature-stability of the two types of the foams were comparable. The results indicate that the surface functionalization of lignin increases reactivity and homogeneity of the lignin as a building block in RPU foams. The life cycle assessment for the lignin-based RPU foams shows that the surface functionalization process would have overall lesser environmental impacts when compared with the traditional manufacturing of RPU foams with synthetic polyols. These findings suggest the potential use of surface functionalized lignin as a sustainable core material replacement for synthetic polyols in building materials.

Insight into the phase evolution of a NiMgAl catalyst from the reduction stage to the post-reaction stage during the dry reforming of methane.

Herein, phase evolution of a NiMgAl oxide catalyst at the reduction stage was qualitatively analysed and quantitatively determined by employing the continuous changes in its XRD intensity and TPR information. The stable crystallite size of both the active metal and spinel support was responsible for the long stability of the NiMgAl catalyst without carbon deposition during the DRM reaction.

Catalytic removal of oxygen from biomass-derived syngas.

Selective oxygen (O2) removal from wood-derived syngas was investigated over three types of ceria-modified alumina supported metal catalysts (i.e., Pt, Pd, and Cu). Complete O2 removal was observed with the Pt and Pd catalysts at a lower temperature than with the Cu catalyst. Gas hourly space velocity (GHSV) was another critical parameter affecting O2 removal, substantially reducing O2 conversion by all three catalysts at 4000 h(-1) or above. The Cu catalyst appeared to be most sensitive to GHSV. Among three catalysts, the Pd catalyst had the best performance on O2 removal. In addition to reaction conditions, CO2 and water vapor in the syngas also influenced O2 removal, both of which had adverse effects on O2 conversion. Stability tests indicated that both Pt and Pd catalysts were quite stable over a 300 h testing period while the Cu catalyst was deactivated after 50h and regenerated by elevating reaction temperature.

Catalytic conversion wood syngas to synthetic aviation turbine fuels over a multifunctional catalyst.

A continuous process involving gasification, syngas cleaning, and Fischer-Tropsch (FT) synthesis was developed to efficiently produce synthetic aviation turbine fuels (SATFs). Oak-tree wood chips were first gasified to syngas over a commercial pilot plant downdraft gasifier. The raw wood syngas contains about 47% N(2), 21% CO, 18% H(2), 12% CO(2,) 2% CH(4) and trace amounts of impurities. A purification reaction system was designed to remove the impurities in the syngas such as moisture, oxygen, sulfur, ammonia, and tar. The purified syngas meets the requirements for catalytic conversion to liquid fuels. A multi-functional catalyst was developed and tested for the catalytic conversion of wood syngas to SATFs. It was demonstrated that liquid fuels similar to commercial aviation turbine fuels (Jet A) was successfully synthesized from bio-syngas.