Functionalized galactoglucomannan‐based hydrogels for the removal of metal cations from aqueous solutions

New types of hydrogels derived from O‐acetyl galactoglucomannan (AcGGM) hemicellulose have been synthesized and characterized. The objective of this work was to analyze the sorption capacity (S) of three types of hydrogels containing AcGGM derivatives incorporated into the carboxylic groups of the polymer chain in the AA hydrogel, sulfonic groups in the APA hydrogel, and amide groups in the acrylamide (Aam) hydrogel. These hydrogels are capable of interacting and removing ions such as cadmium [Cd(II)], copper [Cu(II)], lead [Pb(II)], nickel [Ni(II)], and zinc [Zn(II)]. The results show that AA and Aam hydrogels had a lower sorption capacity of ions compared to the APA hydrogel, which had a high sorption capacity. The maximal sorption capacity was determined by the successive enrichment method, obtaining Pb(II) amount of 48.3 mg/g of AA hydrogel, 65.8 mg/g of APA hydrogel, and 40.8 mg/g of Aam hydrogel. Hence, Pb(II) ions are greatly retained by the three hydrogels. These results are promising for the development of new materials with potential applications in metal ion removal. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44093.     

Kinetic modeling of hemicellulose hydrolysis in the presence of homogeneous and heterogeneous catalysts

Kinetic models were developed for the hydrolysis of O‐acetyl‐galactoglucomannan (GGM), a hemicellulose appearing in coniferous trees. Homogeneous and heterogeneous acid catalysts hydrolyze GGM at about 90°C to the monomeric sugars galactose, glucose, and mannose. In the presence of homogeneous catalysts, such as HCl, H₂SO₄, oxalic acid, and trifluoroacetic acid, the hydrolysis process shows a regular kinetic behavior, while a prominent autocatalytic effect was observed in the presence of heterogeneous cation‐exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the nonhydrolyzed sugar units and the increase of the rate constant (for heterogeneous catalysts) as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and special cases of them were considered in detail, by deriving analytical solutions for product distributions. The kinetic parameters, describing the autocatalytic effect were determined by nonlinear regression analysis. The kinetic model described very well the overall kinetics, as well as the product distribution in the hydrolysis of water soluble GGM by homogeneous and heterogeneous catalysts. The modelling principles developed in the work can be in principle applied to hydrolysis of similar hemicelluloses as well as starch and cellulose. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1066–1077, 2014     

Heat Treatment and Chemical Composition of Fatty Acids and Rosin Acids Mixtures: Effects on Their Thermal Properties and Morphology

Mixtures of fatty acids and rosin acids are industrially important products utilized as a raw material for several purposes. Their thermal properties, especially cold stability and crystallization behavior is also important. Several fatty acid and rosin acid mixtures both from industrial products and from commercially available fatty and rosin acids were prepared and treated for 30 min at 80 °C under an inert atmosphere. Thereafter, the mixture was cooled to the desired temperature. Determination of the cloud point, chemical analysis of liquid and solid phase, thermal analysis by differential scanning calorimetry as well as morphology analysis by scanning electron microscopy were performed. The results revealed that crystallization was more rapid when it occurred at 10 °C compared to 25 °C. The crystal sizes increased with decreasing the crystallization temperature. Furthermore, crystals were of irregular shape and agglomerated when rapid cooling of the mixture occurred. Chemical analysis revealed that liquid phase was enriched with stearic acid, whereas crystals contained large amounts of abietic, dehydroabietic and linoleic acids. The cloud point of the mixtures increased with increasing amount of stearic and rosin acids. Dehydroabietic acid addition improved the cold stability of the synthetic fatty acid–rosin acids mixture.     

Lignin and Other Aromatic Substances Released from Spruce Wood During Pressurized Hot-Water Extraction,Part 2: Structural Characterization

Extraction of ground spruce sapwood with pressurized hot water in an accelerated solvent extractor (ASE) at 170°C during 20, 60, and 100 min resulted in isolation of galactoglucomannans and aromatic substances, including lignin. The isolated lignin preparations were characterized by spectrometric (UV, FT-IR, ¹H NMR, liquid and solid-state ¹³C NMR), chromatographic (RP-HPLC, HP-SEC, GC-FID, and GC-MS), conventional pyrolysis, thermally assisted hydrolysis, and methylation techniques in tandem with GC-MS, and classical wet chemistry (methoxyl groups, total and phenolic hydroxyl groups, derivatization followed by reductive cleavage—DFRC). The content of β-O-4 bonds in isolated lignins was similar to that in MWL and their proportion decreased with extraction time. The oxidation of isolated lignins and content of total hydroxyl groups were significantly increased with extraction time. The lignin structure underwent condensation and demethylation reactions during hot-water extraction. The induction of new phenylcoumaran substructures was proposed in isolated lignins.     

Antioxidant flavonoids from knotwood of Jack pine and European aspen

Flavonoids have recently been found in large amounts in knotwood and stemwood of several tree species. Six flavonoids, two flavonoid glucosides, and one cinnamic acid derivative were isolated from Jack pine and European aspen knotwood and structurally characterised using GC-MS, HR-MS, and NMR spectroscopic analyses. Isolated compounds were further assessed on basis of their potency to inhibit lipid peroxidation and scavenge peroxyl radicals. All tested compounds possessed antioxidant properties close to that of the reference compound Trolox.     

Selective Hydrolysis of Arabinogalactan into Arabinose and Galactose Over Heterogeneous Catalysts

Abstract  

The application of solid acid catalysts for the production of monomers from hemicelluloses can be one of the key steps in developing the concept of an integrated forest biorefinery. Arabinogalactans (AG) are hemicelluloses which can be extracted on an industrial scale from larch wood species and has a great potential as a sustainable feedstock for bio-based products. Hydrolysis of AG to monomers over acidic heterogeneous catalysts (Smopex-101 and Amberlyst 15) was successfully demonstrated for the first time to selectively produce arabinose as the primary product, followed by the release of galactose without further degradation of the monomers.     

One-Step Fractionation of the Main Components of Bamboo by Formic Acid-based Organosolv Process Under Pressure

To promote the efficient utilization of lignocellulosic materials, one-step fractionation by formic acid-based organosolv process under pressure has been studied for converting lignocellulose in its main components. Lignin and hemicelluloses were selectively dissolved, while cellulose was not obviously degraded. Under optimized conditions (85% formic acid, a liquor-to-solid ratio of 7:1, and a temperature of 145°C for 45 min), this process provided a high efficient way to separate the main components of bamboo, obtaining 42.2% cellulose pulp, 31.5% lignin, 8.5% hemicellulose-rich fraction, 3.56% furfural and 3.80% acetic acid. Cellulose pulp with satisfying viscosity could easily be bleached to a high brightness of over 87% ISO with a short bleaching sequence, and had an acceptable paper strength properties. The recovered lignin fraction contained a small amount of carbohydrates and a considerable part of proteins and p-hydroxycinnamates. Additionally, the organic substances in hemicellulose-rich fraction obtained was composed of 95% carbohydrates, most of which was monosaccharides, as well as 5% lignin.     

Extractives of Turkish and Pakistani Tree Species

The composition and amount of hydrophilic and lipophilic extractives in knots and stemwood of eight Turkish and one Pakistani tree species were analysed. Lignans were the main polyphenols in most studied species and pinosylvins in the pines. The two studied juniper species contained no or only little lignans. Most species also contained juvabiones or phenolic diterpenoids. Both polyphenols and lipophilic extractives were more abundant in the knots than in the stemwood.