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

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.