Hydrodynamic alignment and self-assembly of cationic lignin polymers made of architecturally altered monomers

Extraction of high-purity lignin from the kraft pulping black liquor by enzyme purification process with alkaline-resistant xylanase and cellulase

In this study, the response surface methodology was first utilized to optimize the enzyme treatment conditions as reaction pH, temperature, time and enzyme dosage of 9.5, 45 °C, 94.5 min and 100 U/L. Under these parameters, the kraft pulping black liquor was treated with alkaline-resistant xylanase and cellulase, followed by acid precipitation to obtain enzyme-purified lignin (EPL). The yield, purity and physicochemical characteristics of EPL were contrasted with acid-purified lignin (APL) prepared at the same pH values. Results showed that the enzyme purification method generated lignin with lower molecular weight of 3532 g/mol, greater purity of 96.79 % and higher yield of 2.89 %. Compared with APL, EPL exhibited stronger UV absorption capacity. SEM images revealed that EPL had a rough and porous surface, whereas the surface of APL was relatively smooth. TGA analysis indicated the thermal stability of EPL (Tmax = 333.5 °C) was superior to APL (Tmax = 309.2 °C). Moreover, no significant differences were observed in the chemical functional groups and molecular structures of APL and EPL, suggesting that the addition of alkaline-resistant xylanase and cellulase didn't change the chemical structure of lignin. The favorable properties of EPL make it a promising application in the development of high-value composite materials and biodegradable plastics.

A new perspective of sediment layering scour and migration under the coupled effects of particle distribution and bio-viscosity-cavitation erosion

The scouring and migration of sediments in sewer systems are the key contributors to overflow pollution. Both physical and biological factors affect the erosion and migration of layered sediments. However, the functional characteristics of these factors and their quantification process still need to be further explored. In this study, the physical form and biological metabolism of the sediment are coupled, and the suspension mechanism under the dual action is proposed systematically and deeply. The influence coefficient of scour initiation was redefined as A^/prime, where the physical factors were particle size and mass, and the biological factors were bio-viscosity and internal cavitation. The bio-viscosity of layered sediment particles is provided by Extracellular Polymeric Substances (EPS). The slope value of |ΔD/-Δf| (ΔD: Dissipation; Δf: frequency) of surface EPS decreased from 0.489 to 0.315 when Quartz Crystal Microbalance with Dissipation (QCM-D) was used to analyse EPS viscosity, indicating that biological activities formed a dense biofilm on the sediment surface and enhanced the bond between particles. Meanwhile, by monitoring the accumulation density of sediments at different depths, it was found that the packing density of the bottom layer decreased from 1.50 to 1.45 g/cm3, which was mainly due to the internal cavitation caused by microorganism consuming organic matrix and releasing H2S and CH4. The delamination difference of EPS results in the uneven change of adhesion between different layers. This, combined with the internal erosion characteristics triggered by microbial stratified metabolism, collectively constitutes the biological effects on the sediment structure. Finally, the coupling mechanism of particle distribution and bio-viscous-cavitation erosion was formed, and the correctness of the formula was verified by repeated experiments, which proved the agreement between the theory and the practice and provided a scientific method for systematically analysing the erosion and migration law of sediment in the sewer system.

Dual lignin-derived polymeric system for peptone removal from simulated wastewater

The long-term existence of peptone can breed a large number of bacteria and cause the eutrophication of municipal wastewater. Thus, removing peptone in the wastewater is a major challenge facing the current industry. This study used cationic and anionic lignin polymers, i.e., kraft lignin-[2-(methacryloyloxy)ethyl] trimethylammonium methyl sulfate (cationic lignin polymer, CLP) and kraft lignin-acrylic acid (anionic lignin polymer, ALP), as flocculants to eliminate peptone from model wastewater in the single and dual component systems. The affinity of peptone for ALP or CLP was assessed by quartz crystal microbalance with dissipation, X-ray photoelectron spectroscopy, contact angle, and vertical scan analyzer. Results illustrated that the adsorption effect of CLP for peptone was significantly superior to that of ALP owing to the stronger vital interaction between cationic polymer and peptone molecules. Based on destabilization and sedimentation analyses, introducing CLP triggered the preliminary flocculation of peptone via bridging action, as indicated by a considerable increment in the destabilization index (from 1.1 to 10.6). Moreover, peptone adsorbed more on the CLP coated surface than on the ALP coated one (14.8 vs 5.4 mg/m2), while ALP facilitated its further adsorption in the dual polymer system. This is because CLP adsorbed a part of peptone molecules on its surface. Then, ALP entrapped the unattached peptone onto the CLP coated surface through electrostatic interaction. Compared with the single polymer system, mixing ALP and CLP subsequently into the peptone solution in the dual system generated larger size aggregates (mean diameter of 6.1 μm) and made the system destabilization (Turbiscan stability index up to 58.1), thereby yielding more flocculation and sedimentation. Finally, peptone was removed successfully from simulated wastewater with a turbidity removal efficiency of 92.5%. These findings confirmed that the dual-component system containing two lignin-derived polymers with opposite charges could be viable for treating peptone wastewater.

Light-Programmed Bistate Colloidal Actuation Based on Photothermal Active Plasmonic Substrate

Active particles have been regarded as the key models to mimic and understand the complex systems of nature. Although chemical and field-powered active particles have received wide attentions, light-programmed actuation with long-range interaction and high throughput remains elusive. Here, we utilize photothermal active plasmonic substrate made of porous anodic aluminum oxide filled with Au nanoparticles and poly( N -isopropylacrylamide) (PNIPAM) to optically oscillate silica beads with robust reversibility. The thermal gradient generated by the laser beam incurs the phase change of PNIPAM, producing gradient of surface forces and large volume changes within the complex system. The dynamic evolution of phase change and water diffusion in PNIPAM films result in bistate locomotion of silica beads, which can be programmed by modulating the laser beam. This light-programmed bistate colloidal actuation provides promising opportunity to control and mimic the natural complex systems.

Modification of Paper Surface by All-Lignin Coating Formulations

All-lignin coating formulations were prepared while combining water-soluble cationic kraft lignin (quaternized LignoBoost®, CL) and anionic lignosulphonate (LS). The electrostatic attraction between positively charged CL and negatively charged LS led to the formation of insoluble self-organized macromolecule aggregates that align to films. The structures of the formed layers were evaluated by atomic force microscopy (AFM), firstly on glass lamina using dip-coating deposition and then on handsheets and industrial uncoated paper using roll-to-roll coating in a layer-by-layer mode. Coated samples were also characterized by optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (SEM/EDS), and contact angle measurements. It was suggested that the structure of all-lignin aggregates is the result of the interaction of amphiphilic water-soluble lignin molecules leading to their specifically ordered mutual arrangement depending on the order and the mode of their application on the surface. The all-lignin coating of cellulosic fiber imparts lower air permeability and lower free surface energy to paper, mainly due to a decrease in surface polarity, thus promoting the paper's hydrophobic properties. Moderate loading of lignin coating formulations (5-6 g m-2) did not affect the mechanical strength of the paper.