Weathering Characteristics of Wood Plastic Composites Reinforced with Extracted or Delignified Wood Flour.

This study investigated weathering performance of an HDPE wood plastic composite reinforced with extracted or delignified wood flour (WF). The wood flour was pre-extracted with three different solvents, toluene/ethanol (TE), acetone/water (AW), and hot water (HW), or sodium chlorite/acetic acid. The spectral properties of the composites before and after artificial weathering under accelerated conditions were characterized by Fourier transform infrared (FTIR) spectroscopy, the surface color parameters were analyzed using colorimetry, and the mechanical properties were determined by a flexural test. Weathering of WPC resulted in a surface lightening and a decrease in wood index (wood/HDPE) and flexural strength. WPCs that were reinforced with delignified wood flour showed higher ΔL* and ΔE* values, together with lower MOE and MOR retention ratios upon weathering when compared to those with non-extracted control and extracted WF.

Influence of drying method on the surface energy of cellulose nanofibrils determined by inverse gas chromatography.

Research and development of the renewable nanomaterial cellulose nanofibrils (CNFs) has received considerable attention. The effect of drying on the surface energy of CNFs was investigated. Samples of nanofibrillated cellulose (NFC) and cellulose nanocrystals (CNC) were each subjected to four separate drying methods: air-drying, freeze-drying, spray-drying, and supercritical-drying. The surface morphology of the dried CNFs was examined using a scanning electron microscope. The surface energy of the dried CNFs was determined using inverse gas chromatography at infinite dilution and column temperatures: 30, 40, 50, 55, and 60 °C. Surface energy measurements of supercritical-dried NFCs were performed also at column temperatures: 70, 75, and 80 °C. Different drying methods produced CNFs with different morphologies which in turn significantly influenced their surface energy. Supercritical-drying resulted in NFCs having a dispersion component of surface energy of 98.3±5.8 mJ/m(2) at 30 °C. The dispersion component of surface energy of freeze-dried NFCs (44.3±0.4 mJ/m(2) at 30 °C) and CNCs (46.5±0.9 mJ/m(2) at 30 °C) were the lowest among all the CNFs. The pre-freezing treatment during the freeze-drying process is hypothesized to have a major impact on the dispersion component of surface energy of the CNFs. The acid and base parameters of all the dried CNFs were amphoteric (acidic and basic) although predominantly basic in nature.

Adsorption mechanism of cadmium on juniper bark and wood.

In this study the capacity of sorbents prepared from juniper wood (JW) and bark (JB) to adsorb cadmium (Cd) from aqueous solutions at different pH values was compared. Adsorption behavior was characterized through adsorption kinetics, adsorption isotherms, and adsorption edge experiments. Results from kinetics and isotherm experiments showed that JB (76.3-91.6 micromol Cdg(-1) substrate) had 3-4 times higher adsorption capacity for Cd than JW (24.8-28.3 micromol Cdg(-1)). In addition to higher capacity, JB exhibited a higher strength of adsorption (45.3 versus 9.1 Lmmol(-1)) and faster uptake kinetics (0.0119 versus 0.0083 g micromol(-1)min(-1)) compared to JW. For both these adsorbents, increasing Cd adsorption with increasing solution pH in the range of 2-6 suggests that surface carboxyl groups (RCOOH) might be involved in interaction with Cd. Diffuse reflectance infrared Fourier transform (DRIFT) spectra showed that the surface concentration of carboxyl groups was higher on JB compared to JW. The ratio of Ca released to Cd adsorbed was 1.04 and 0.78 for JB and JW, respectively, indicating that Ca-Cd ion-exchange was the primary mechanism involved. The higher Ca content in JB (15 times more) and the surface RCOOH concentration (2.5 times more) can be attributed to the observed differences in Cd adsorption behavior between the two lignocellulosic adsorbents.

Orthophosphate sorption onto lanthanum-treated lignocellulosic sorbents.

Inorganic/organic hybrid adsorbents for removing orthophosphate from water were prepared by lanthanum (La) treatment of bark fiber, a lignocellulosic material obtained from juniper (Juniperus monosperma). The La was anchored to the juniper bark (JB) fiber by ion exchange with Ca in the bark and was responsible for removing orthophosphate. Two La concentrations (0.01 and 0.1 M) were used that resulted in loadings of 0.198 (La/JB01) and 0.302 (La/JB02) mmol of La g(-1) of fiber, respectively. At circumneutral pH conditions, La exhibited a strong affinity for bark, but significant La desorption occurred under acidic conditions (pH < 4.5). For La/JB02, 86% of the initial La loading was released at pH 2.5, and only 0.1% at pH 7.3. Initial La loading in the bark fiber significantly influenced its orthophosphate sorption capacity, which was determined for La/JB01 and La/JB02, respectively, to be 0.188 and 0.233 mmol of P g(-1) (sorption envelopes) and 0.211 and 0.351 mmol of P g(-1) (sorption isotherms when surface site saturation occurred). The P-to-La molar ratio on the bark surface was extremely high (0.12-1.77for La/JB01 and 0.13-2.58 for La/JB02), implying that orthophosphate removal occurred by other mechanisms in addition to surface complexation. From the orthophosphate surface loading levels and the shape of the sorption isotherms, it appears that adsorption occurred at low sorbate-to-sorbent (P-to-La-treated JB) ratios and transitioned to surface precipitation at higher ratios. When surface precipitation occurred, orthophosphate uptake continued to increase with increasing initial P levels. Results from X-ray diffraction and infrared spectrometric analyses are also suggestive of the occurrence of surface precipitation during the interaction of orthophosphate with La-treated lignocellulosic materials.

Solution chemistry effects on orthophosphate adsorption by cationized solid wood residues.

Adsorption of orthophosphate anions in aqueous solution by cationized milled solid wood residues was characterized as a function of sorbate-to-sorbent ratio (approximately equal to 0.001-2.58 mmol of P/g substrate), pH (3-9), ionic strength, I (no I control; 0.001 and 0.01 M NaCl), reaction time (4 min to 24 h), and in the presence of other competing anions (0.08-50 mM SO4(2-); 0.08-250 mM NO3-). Sorption isotherms revealed the presence of two kinds of adsorption sites corresponding to high and low binding affinities for orthophosphate anions. Consequently, a two-site Langmuir equation was needed to adequately describe the data over a range of solution conditions. In addition to higher sorption capacity, cationized bark possessed a higher binding energy for orthophosphate anions compared to cationized wood. The sorption capacity and binding energy for bark were 0.47 mmol of P g(-1) and 295.7 L mmol(-1), respectively, and for wood, the corresponding values were 0.27 mmol g(-1) and 61.4 L mmol(-1). Both the sorption capacity and binding energy decreased with increasing I, due to competition from Cl- ions for the available anion-exchange sites. The surface charge characteristics of cationized bark (pHzpc = 7.9) acted in concert with orthophosphate speciation to create a pH-dependent sorption behavior. Orthophosphate uptake was quite rapid and attained equilibrium levels after 3 h. Both SO4(2-) and NO3- influenced percent removal but required high relative competing anion to H2PO4- molar ratios, i.e., 2.5-3 for SO4(2-) and 25 for NO3-, to cause appreciable reduction. These results support our hypothesis that adsorption of orthophosphate anions on cationized bark involves ion exchange and other specific Lewis acid-base interactions.