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The effect of hydrothermal conditions on enzymatic hydrolysis lignin (EHL) degradation in water-isopropyl alcohol co-solvent and optimal conditions were investigated. The yields and reactivity toward formaldehyde of degraded enzymatic hydrolysis lignin (DEL) were determined. The optimal conditions of temperature, time, and ratio of solids to liquids were 250 °C, 60 min, and 1:10 (w/v), respectively. The EHL and DEL were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), ¹H nuclear magnetic resonance (¹H NMR), thermal gravity (TG), and differential scanning calorimetry (DSC) analyses. The results revealed that the molecular weight and polydispersity of DEL were lower than that of EHL. Although the fundamental structure of lignin before and after hydrothermal degradation was retained, the ether (ß-O-4, α-O-4, etc.) content decreased, while that of hydroxyl (phenolic and aliphatic) increased. The DTGmax and Tg values shifted from 334 and 117 °C to 304 and 105 °C, respectively. [ABSTRACT FROM AUTHOR]

The physicochemical properties of alkali lignin are crucial to its potential applications and recyclability, as it is one of the most important natural polymer materials. In this study, the solubility parameter (δ) of alkali lignin was determined using Hansen solubility parameters (HSP) theory and inverse gas chromatography (IGC). The δ of alkali lignin was determined by the IGC technique. Solute retention volumes (Vg0) of 6 solutes were determined using alkali lignin as the stationary phase. From 50 to 110 ºC, the δ of alkali lignin varied from 24.47 to 24.15 MPa1/2. Hansen solubility spheres were plotted using the data from the literature for the interactions of alkali lignin with 36 solutes to determine the three dimensional solubility parameter of alkali lignin at 25 to 100 ºC. These determined δ values were consistent with those calculated experimentally via IGC. Acetone was a moderate solvent for the alkali lignin. [ABSTRACT FROM AUTHOR]

For the controlled release of pesticides, a novel composite porous hydrogel (LBPAA) was prepared based on lignin and polyacrylic acid for use as the support frame of a pore structure for water delivery. The LBPAA was analyzed to determine its water-swelling and slow release properties. The controlled release properties of LBPAA were evaluated through experiments in relation to the cumulative release of pesticides, with particular emphasis on environmental effects and release models. The porous LBPAA hydrogel showed improved properties compared to polyacrylic acid, and could therefore be considered an efficient material for application in controlled release systems in agriculture. [ABSTRACT FROM AUTHOR]

This study investigates methods for improving the heat resistance of polyvinyl alcohol/alkali lignin foam material (PLFM). Tetraethoxysilane (TEOS) was used as a precursor to prepare PLCFM by a sol-gel method. The PLCFM, prepared with different levels of TEOS, was characterized by Fourier Transform Infrared spectrometry (FTIR), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). The results indicated that the addition of silica notably improved the heat resistance properties and the initial decomposition temperature of the foam and exhibited good biocompatibility with the polyvinyl alcohol (PVOH) and alkali lignin. The melting temperature of the PLCFM also increased significantly. It reached 268 °C when the silica content was 10%, which was 110 °C higher than that of PLFM. The mechanical properties were also improved to 27.42 MPa. [ABSTRACT FROM AUTHOR]

Kraft lignin was used to prepare kraft lignin-N-isopropyl acrylamide hydrogel (KNIAH). The results indicated that using a 1:2 mass ratio of KL-to-N-isopropyl acrylamide (NIPAM), 48 h reaction time, and 1.5 mL of crosslinking agent yielded KNIAH with the maximum swelling degree (209.3%). The crosslinking reaction was verified by C-N shifting at 1272 cm-1 and increased C=O bonding at 1720 cm-1. KNIAH with a smooth and uniform surface was created. DSC demonstrated that free water combined with KNIAH at 200 °C, after which KNIAH began exothermic decomposition. TGA shows that KNIAH with good performance of heat resistance and degradation. Absorption was maximized at 20 °C; low temperature and neutral solution was conducive to water absorption. Decolorization increased with decreasing concentration and pH value. [ABSTRACT FROM AUTHOR]

To improve the added value of the lignin products, dimethyl-acetoxy-(2- carboxymethyl ether)-lignin ammonium chloride (DALAC) amphoteric surfactant was synthesized from wheat straw alkali lignin raw material. The structure was analyzed by Fourier transform infrared spectroscopy (FT-IR), and the solubility in different pH solutions was evaluated. The effect of DALAC on adsorption performance was investigated with a solution of copper ions as simulated wastewater, while its flocculation performance was investigated with acid black ATT and methylene blue (MB) wastewater as simulate dyes. The results showed that carboxyl and quaternary amine groups were successfully grafted, and nitrogen content of DALAC was 3.66%. The adsorption isotherm of copper ions with DALAC fit the Freundlich equation. Optimum adsorption conditions for Cu2+ were dosage 0.1 g/L, pH 5.5, and adsorption time 6 h, for which the maximum adsorption capacity was 399 mg/g. The maximum removal rate of Acid black ATT (anionic dye) was 97.8% when the optimum flocculation conditions were dosage 4 g/L, pH 2, and mass concentration of dye 0.1 g/L. The maximum removal rate of methylene blue (cationic dye) was 98.7 %, when the optimum flocculation conditions were dosage 2.5 g/L, pH 9, and mass concentration of dye 0.1 g/L. DALAC will be expected to a novel adsorbent of heavy metal ion and flocculants of dyes in the future. [ABSTRACT FROM AUTHOR]

In order to improve the molecular weight and application of a lignin byproduct, the trimethyl quaternary ammonium salt of lignin-sodium alginate polyampholyte (QL-SA) was prepared with trimethyl quaternary ammonium salt of lignin (QL) and sodium alginate (SA), using the cross-linker glutaraldehyde. Its structure was analyzed by FTIR, SEM, and analysis of nitrogen and carboxylic contents. Results showed that QL and SA were grafted successfully. The nitrogen content was diminished from 4.21% to 3.69% and its carboxyl content increased from 2.66 mmol/g to 6.47 mmol/g. The product behaved as flocculant by electrostatic interactions and bridging actions. The effects of QL-SA on the flocculation performance of dyes were investigated with methylene blue and acid black ATT water as the representative dyes. The maximum decolorization rate of acid black ATT was 94.91% and methylene blue was 97.11% under the corresponding optimal conditions (5 g/L of the flocculant at pH 3, 30 °C, and 8 g/L at pH 8, 30 °C). The effect of QL-SA was found to be markedly superior to SA and QL on the whole. The QL-SA showed promise for practical applications. [ABSTRACT FROM AUTHOR]

With alkali lignin and PVA as the primary materials, glutaraldehyde as the cross-linker, and glycerin as the plasticizer, alkali lignin/PVA cross-linking reaction film was prepared by casting. The process conditions were evaluated one at a time for different variables. Mechanical properties of the composite film were tested. The performance of the reaction film was analysed by XRD, TG, SEM, and FT-IR. The results showed that when the mass ratio of alkali lignin/PVA was 1/5, glutaraldehyde content 1.67%, and glycerol content 7.1% (w/w) of the dry matter, respectively, the reaction film had satisfactory mechanical properties. Under the best conditions, the mechanical properties of the reaction film were better than that of pure PVA film. The thermal stability of the reaction film was higher than the stability of PVA film. Compared with pure PVA film, the crystallinity of the reaction film decreased a little. SEM images indicated that compatibility of alkali lignin and PVA was good. The FT-IR analysis showed that a cross-linking reaction occurred between alkali lignin and PVA(1788). But the aldol reaction between the lignin and PVA(1788) was weak. [ABSTRACT FROM AUTHOR]

Membranes were prepared from alkaline lignin and poly(vinyl alcohol) (PVA) by a film casting method, and their properties were evaluated. These blend membranes can aptly be termed as green by nature as they are totally non-toxic and eco-friendly. The optimal mass ratio was determined based on the mechanical properties of membranes. The microstructure, mechanical properties, oxygen and carbon dioxide transmission, light transmittance, and thermal stability of the membranes were investigated. The blend membrane exhibited better thermal stability and barrier performance to oxygen and carbon dioxide than a PVA membrane due to the incorporation of alkaline lignin. Both tensile strength and elongation at break were increased with increasing mass fraction of alkaline lignin up to 15%, at which point the maximum of tensile strength and elongation at break were 43.65 MPa and 211.6%, respectively. The blockage of visible light at 600 nm was 62.36%, which was an improvement of 314.90% compared with the PVA membrane (13.36%). Based on this result, we suggest that the mechanical properties of blend membrane containing 15% alkaline lignin are excellent and better than PVA membrane (40.26 MPa, 179.37%). Thus, an alkaline lignin/PVA blend membrane was judged to be potentially suitable as an eco-friendly packing material. [ABSTRACT FROM AUTHOR]