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International audience; Eucalyptus Kraft lignin was blended in various proportions with two different types of polyethylene (PE) (low-density polyethylene and post-consumer recycled [PCR]), with or without compatibilizer (PE-glycidyl methacrylate [GMA] or PE-2-hydroxyethyl methyl acrylate copolymers). Materials prepared by injection molding or extrusion casting were characterized for their thermal, antioxidant, antibacterial and mechanical properties. In addition, the photopermeability was assessed, as this property is specifically relevant to mulching applications. The use of compatibilizers enhanced the antioxidant properties which reached more than 3 h oxidation induction time when lignin was present at 20 wt% and beyond. Good antibacterial properties were obtained on Gram-positive bacteria when using PE-GMA as compatibilizer. The photopermeability of the materials was also reduced, reaching a transmittance lower than 5% throughout the whole measurement range (200-800 nm) in PCR. However, higher lignin contents led to a more brittle material and the overall processability of the material became more difficult, features that were not improved by compatibilizers. These materials are promising candidates for mulching film application, especially with PCR which still lacks high-volume market applications.

A study was conducted to investigate the potential of purified lignin and hemicellulose as prebiotics in diets for Atlantic salmon, Salmo salar L., postsmolt in seawater (30 ppt) at 14.9 ± 1.2°C. T...

The spent pulping liquor (SPL) obtained from straw processed by soda (alkaline) pulping contains dissolved non-sulfonated lignin. The lignin can be separated from SPL using acid or cationic flocculants which are potentially hazardous to the environment. In this study, the performance of the biobased protein flocculant hemoglobin (HEM) with and without added calcium chloride was compared with that of a high charge density synthetic cationic flocculant, poly (diallyldimethylammonium chlorides) (pDADMAC). Turbidity measurements gave overly broad concentration ranges for optimal lignin removal which may be related to the mechanism of flocculation which requires several major steps: Conversion of dissolved lignin to particulate lignin, formation of particulate lignin flocs, and subsequent sedimentation of these flocs. An optimal flocculant concentration or concentration range was estimated using the three methods: average Zeta potential corresponding to the lowest turbidity range; a novel method using the maximum percent pellet mass calculated using the dried masses of the pellet and supernatant after centrifugation; measurement of supernatant lignin using spectroscopy. HEM light absorption interfered with spectroscopic lignin determination, and a method for correcting the measurements was devised. This study shows that HEM is an effective flocculant for nonsulfonated lignin in SPL. The HEM-lignin complex is a potential high protein component of animal feed.

BACKGROUND The kaolin flocculant activities of bovine blood (BB) and hemoglobin (HEM) at different salt and pH values were determined. Lower limit concentration (LLC), window of application (WA), and degrees of clarification (DC) values for BB and HEM were determined and compared with those of the synthetic polymeric flocculants poly(diallydimethylammonium chloride) (PDADMAC), cationic polyacrylamide (PAM), and anionic PAM. BB flocculation of lignin, a bioproduct of biomass conversion to bioethanol, was demonstrated. RESULTS Flocculation of kaolin by BB and HEM increased at acidic pH and in the presence of NaCl. LLC values of HEM and BB were similar to LLC values of cationic and anionic PAM. LLC values of HEM and BB were 18–20-fold higher than that of PDDMAC. WA values of BB and HEM were similar to those of PDADMAC, cationic PAM, and anionic PAM. For lignin flocculation, the ratio of LLC for BB/PDADMAC was 20–38, but the ratio of WA for BB/PDADMAC was > 3.6. For kaolin and lignin flocculation, DC values were similar for all flocculants. CONCLUSIONS The renewable flocculants BB and HEM rapidly settle kaolin and lignin suspensions; BB and HEM could be used in the process to separate lignin from other biomass components. Published 2014. This article is a U.S. Government work and is in the public domain in the USA

In industrial process, acidification causes non-sulfonated lignin insolubility. The flocculants poly(diallyldimethylammonium chloride) (pDADMAC) and bovine blood (BB) also caused lignin insolubility while cationic polyacrylamide, chitosan, and soy protein PF 974 were ineffective. Turbidity determined optimal flocculant, but turbidity magnitude with BB was greater than expected. pDADMAC caused negative lignin Zeta potential to became positive, but BB-lignin Zeta potential was always negative. Insoluble lignin did not gravity sediment, and flocculant-lignin mixtures were centrifuged. Pellet and supernatant dry mass and corrected spectroscopic results were in good agreement for optimal pDADMAC and BB. Spectroscopy showed 87-92% loss of supernatant lignin. Nitrogen analysis showed BB concentrated in the pellet until the pellet became saturated with BB. Subtracting ash and BB mass from pellet and supernatant mass confirmed optimal BB. Low levels of alum caused increased lignin flocculation at lower levels of pDADMAC and BB, but alum did not affect optimal flocculant.

Lignin is the most abundant renewable aromatic material on Earth and is a logical link in the sustainable supply chain of the chemicals and materials that today we derive mostly from fossil-based benzene. In this chapter, we review lignin’s industrial sources and the recent progress in developing polymeric materials that use lignin as a macromonomer, polymer blend, functional additive, and precursor for advanced carbon materials. Several high-purity lignin production facilities were installed recently at pulp mills in three continents. Additional lignin availability is expected as second generation biofuel biorefineries realize that it makes sense to add value beyond the energy content of the lignin-rich residues that they generate. In the last decade, many lignin applications have seen significant progress, including lignin use in thermoset resins, polyurethanes, polyesters, polymer blends, elastomers, smart memory materials, antioxidants, functional packaging, electrically conductive materials for energy storage, coatings, advanced carbon materials, engineering plastics, ingredients for inks and varnishes, UV light blockers, coatings, compostable plastics, foams, rubber products, insulation, sealants, fiber composites, etc. Several of the applications highlighted here have already entered commercialization, while many others are expected to do so within the next few years. Increasing lignin use will result in environmental benefits and products with reduced carbon footprint. Application to lignin of emerging technologies may open new routes for lignin valorization in the near future.

Lignin represents a vastly under-utilized natural polymer co-generated during papermaking and biomass fractionation. Different types of lignin exist, and these differ with regard to isolation protocol and plant resource (i.e., wood type or agricultural harvesting residue). The incorporation of lignin into polymeric systems has been demonstrated, and this depends on solubility and reactivity characteristics. Several industrial utilization examples are presented for sulfur-free, water-insoluble lignins. These include materials for automotive brakes, wood panel products, biodispersants, polyurethane foams, and epoxy resins for printed circuit boards.

The reactions between aspen milled wood lignin (MWL) and 2-naphthol, resorcinol, and p-hydroxybenzoic acid were studied under simulated autohydrolysis conditions. The material after the reaction was separated into a dioxane-insoluble fraction (DI), a dioxane-soluble but ether-insoluble fraction (DSEI), and an ether-soluble fraction (ES). In the absence of additive, the lignin first depolymerized and remained solvent soluble, then repolymerized to become insoluble. With 2-naphthol as additive, the amount of DI lignin decreased proportionally to the amount of additive present. When more than 0.1 mole of 2-naphthol/C-9 unit was present, no DI lignin was formed, that is, all the lignin was soluble. Gel permeation chromatography studies indicated that the additive was acting effectively as a blocking agent, preventing lignin repolymerization. Small amounts of resorcinol acted as a repolymerizing agent since two or more fragments of lignin could readily condense with a molecule of the very active additive. As a result of this bridging effect, the amount of DI lignin increased. As the amount of resorcinol was increased, it behaved more like a blocking agent and a reduction in the amount of DI lignin was observed. The presence of a large excess of resorcinol resulted in the formation of soluble lignin only. The molecular weight distributions supported the proposed dual role of resorcinol as a bridging or blocking agent. The use of an excess of p-hydroxybenzoic acid prevented the formation of DI material and resulted in low molecular weight soluble lignin.

In a previous article the authors have described changes in molecular weight which occur when aspen milled wood lignin is subjecte to autocatalyzed hydrolysis (autohydrolysis) in the presence of three aromatic additives: 2-naphthol, resorcinol, and p-hydroxybenzoic acid. In the present work, the reactions of these additives have been studied from the viewpoint of their effect on the structure of the lignin. The use of milled wood lignin instead of aspen wood served to distinguish those reactions between the additives and the lignin, without involving the other wood components. The reaction products have been charactrized by elemental analysis and UV and IR spectroscopy. It was concluded that keto groups, generated on the lignin side-chain during autohydrolysis, condense with the additives, which become incorporated into the lignin. This occurs most probably through an aromatic eletrophilic substitution reaction. While 2-naphthol condensed primarily with the β-keto carbonyl groups, resorcinol attacked also the α-keto carbonyl groups. When p-hydroxybenzoic acid was the additive, its incorporation was accompanied by an increase in lignin carboxylic acid groups.

In order to obtain further understanding of the nature of lignin reactions during autocatalysed hydrolysis (autohydrolysis) of wood, milled wood lignin (MWL) was isolated from aspen (Populus tremuloides) and treated under autohydrolysis conditions. By this means reactions of the lignin itself could be distinguished from those taking place between lignin and the carbohydrate or other components of the wood. The material after the reaction was separated into a dioxane insoluble fraction (DI), a dioxane soluble but ether insoluble fraction (DSEI), and an ether soluble fraction (ES). Studies were carried out on the DI and DSEI fractions; no direct study was made of the small ES fraction.The formation of DI material increased linearly during the first 7.5 min at 170 °C and then levelled off. At the same time DSEI decreased and then levelled off. Gel permeation chromatography of the DSEI fraction suggested that during autohydrolysis there is an initial generation of low molecular weight fragments which recombine to form first a high molecular weight soluble fraction and from this the insoluble product. The DSEI fraction contained increased conjugated and unconjugated keto groups. Carboxylic acids were also detected; they have been attributed to the reincorporation of low molecular weight aromatic acids generated by the hydrolysis of the corresponding esters. The dioxane insoluble (DI) fraction had fewer unconjugated keto groups than the DSEI fraction, indicating that these groups participated in the condensation reactions leading to the formation of insoluble material. These probably involve position 6 of the aromatic ring.