Poly(vinyl alcohol)/quaternized lignin composite absorbent: Synthesis, characterization and application for nitrate adsorption

Cationization of Eucalyptus Kraft LignoBoost Lignin: Preparation, Properties, and Potential Applications

Current changes toward a more biobased economy have recently created tremendous renewed interest in using lignin as a valuable source for chemicals and materials. Here, we present a facile cationization approach aiming to impart kraft lignin water-solubility, with similar good features as lignosulfonates. Eucalyptus globulus kraft lignin obtained from a paper mill black liquor by applying the LignoBoost process was used as the substrate. Its reaction with 3-chloro-2-hydroxypropyl-trimethylammonium chloride (CHPTAC) in an aqueous alkaline medium was studied to assess the impact of different reaction conditions (temperature, time, educt concentration, molar CHPTAC-to-lignin ratio) on the degree of cationization. It has been shown that at pH 13, 10 wt % lignin content, 70 °C, and 3 h reaction time, a CHPTAC-to-lignin minimum molar ratio of 1.3 is required to obtain fully water-soluble products. Elemental analysis (4.2% N), size-exclusion chromatography (M_w 2180 Da), and quantitative ¹³C NMR spectroscopy of the product obtained at this limit reactant concentration suggest introduction of 1.2 quaternary ammonium groups per C9 unit and substitution of 75% of the initially available phenolic OH groups. The possible contribution of benzylic hydroxyls to the introduction of quaternary ammonium moieties through a quinone methide mechanism has been proposed. Since both molecular characteristics and degree of substitution, and hence solubility or count of surface charge, of colloidal particles can be adjusted within a wide range, cationic kraft lignins are promising materials for a wide range of applications, as exemplarily demonstrated for flocculation of anionic dyes.

Facile preparation of biomass lignin-based hydroxyethyl cellulose super-absorbent hydrogel for dye pollutant removal

The severe preparation process, poor swelling properties and mechanical properties of traditional cellulose and polyvinyl alcohol (PVA) composite hydrogels heavily limited their practical applications. To solve these issues, we use long-chain hydroxyethyl celluloses (HECs) as framework backbones, short-chain PVAs as branched chains, lignin molecules as extended crosslinkers and epichlorohydrin molecules as crosslinkers to prepare the lignin-based hydroxyethyl cellulose-PVA (LCP) super-absorbent hydrogels in the alkaline aqueous solution under mild reaction conditions, demonstrating high swelling ratio of up to 1220 g/g. The LCP hydrogels could take up large amounts of positively charged dyes rhodamine 6G, crystal violet and methylene blue with uptakes of 153, 184 and 196 mg/g, respectively. The LCP super-absorbent hydrogels also present excellent water retention, biodegradability and excellent swelling properties, which are very promising for applications in the fields of commercial diapers, soil water retention and seed cultivation in agriculture, and dye pollutant removal.

Trimethylamine (fishy odor) adsorption by biomaterials: effect of fatty acids, alkanes, and aromatic compounds in waxes

Thirteen plant leaf materials were selected to be applied as dried biomaterial adsorbents for polar gaseous trimethylamine (TMA) adsorption. Biomaterial adsorbents were efficient in adsorbing gaseous TMA up to 100% of total TMA (100 ppm) within 24 h. Sansevieria trifasciata is the most effective plant leaf material while Plerocarpus indicus was the least effective in TMA adsorption. Activated carbon (AC) was found to be lower potential adsorbent to adsorb TMA when compared to biomaterial adsorbents. As adsorption data, the Langmuir isotherm supported that the gaseous TMA adsorbed monolayer on the adsorbent surface and was followed pseudo-second order kinetic model. Wax extracted from plant leaf could also adsorb gaseous TMA up to 69% of total TMA within 24 h. Another 27-63% of TMA was adsorbed by cellulose and lignin that naturally occur in high amounts in plant leaf. Subsequently, the composition appearing in biomaterial wax showed a large quantity of short-chain fatty acids (≤C18) especially octadecanoic acid (C18), and short-chain alkanes (C12-C18) as well as total aromatic components dominated in the wax, which affected TMA adsorption. Hence, it has been demonstrated that plant biomaterial is a superior biosorbent for TMA removal.

High shear homogenization of lignin to nanolignin and thermal stability of nanolignin-polyvinyl alcohol blends

A new method to prepare nanolignin using a simple high shear homogenizer is presented. The kraft lignin particles with a broad distribution ranging from large micron- to nano-sized particles were completely homogenized to nanolignin particles with sizes less than 100 nm after 4 h of mechanical shearing. The (13) C nuclear magnetic resonance (NMR) and (31) P NMR analysis showed that there were no major changes in the chemical composition between the starting kraft lignin particles and the nanolignin obtained after 4 h of mechanical treatment. The nanolignin particles did not show any change in molecular weight distribution and polydispersity compared to the original lignin particles. The nanolignin particles when used with polyvinyl alcohol (PVA) increased the thermal stability of nanolignin/PVA blends more effectively compared to the original lignin/PVA blends.