Surface functionalization of cellulose nanocrystals with polymeric ionic liquids during phase transfer

Synthesis of Cellulose-Poly(Acrylic Acid) Using Sugarcane Bagasse Extracted Cellulose Fibres for the Removal of Heavy Metal Ions

In this study, sugarcane bagasse (SCB) was treated with sodium hydroxide and bleached to separate the non-cellulose components to obtain cellulose (CE) fibres. Cross-linked cellulose-poly(sodium acrylic acid) hydrogel (CE-PAANa) was successfully synthesised via simple free-radical graft-polymerisation to remove heavy metal ions. The structure and morphology of the hydrogel display an open interconnected porous structure on the surface of the hydrogel. Various factors influencing batch adsorption capacity, including pH, contact time, and solution concentration, were investigated. The results showed that the adsorption kinetics were in good agreement with the pseudo-second-order kinetic model and that the adsorption isotherms followed the Langmuir model. The maximum adsorption capacities calculated by the Langmuir model are 106.3, 333.3, and 163.9 mg/g for Cu(II), Pb(II), and Cd(II), respectively. Furthermore, X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometry (EDS) results demonstrated that cationic exchange and electrostatic interaction were the main heavy metal ions adsorption mechanisms. These results demonstrate that CE-PAANa graft copolymer sorbents from cellulose-rich SCB can potentially be used for the removal of heavy metal ions.

Controlled Delivery and Photopatterning of Mechanical Properties in Polysaccharide Hydrogels Using Vanadium Coordination and Photochemistry

Incorporation of the transition metal ion V(V) into hydrogels has been used to impart photoresponsive behavior, which was used to tune materials properties during light irradiation. The photoreaction in QHE-cellulose/agarose hydrogels coordinated with vanadium was evidenced by a clear color change of yellow to blue through a green intermediate. This color change was attributed to the reduction of V(V) to V(IV) as described in our previous work. A concomitant oxidative breakdown of the polysaccharide chain was noticeable upon the reduction of V(V) with a decrease in stiffness (G') of the hydrogel material. This reduction of the metal ion and breakdown of polysaccharide chain induced irreversible changes in the microstructure of the hydrogel, enabling the controlled delivery of V(IV) and/or encapsulated cargo. Scanning electron microscopy studies showed an increase in pore sizes and guest cavity formation during irradiation. In addition to the significant drop in mechanical properties like storage and loss modulus in the gel materials, a viscosity drop in the polymer solution was observed through irradiation, indicating breakdown of the polysaccharide chain. A photomask can be used to create discrete patterns on these materials upon irradiation.

Lignocellulosic Biomass-Derived Nanocellulose Crystals as Fillers in Membranes for Water and Wastewater Treatment: A Review

The improvement of membrane applications for wastewater treatment has been a focal point of research in recent times, with a wide variety of efforts being made to enhance the performance, integrity and environmental friendliness of the existing membrane materials. Cellulose nanocrystals (CNCs) are sustainable nanomaterials derived from microorganisms and plants with promising potential in wastewater treatment. Cellulose nanomaterials offer a satisfactory alternative to other environmentally harmful nanomaterials. However, only a few review articles on this important field are available in the open literature, especially in membrane applications for wastewater treatment. This review briefly highlights the circular economy of waste lignocellulosic biomass and the isolation of CNCs from waste lignocellulosic biomass for membrane applications. The surface chemical functionalization technique for the preparation of CNC-based materials with the desired functional groups and properties is outlined. Recent uses of CNC-based materials in membrane applications for wastewater treatment are presented. In addition, the assessment of the environmental impacts of CNCs, cellulose extraction, the production techniques of cellulose products, cellulose product utilization, and their end-of-life disposal are briefly discussed. Furthermore, the challenges and prospects for the development of CNC from waste biomass for application in wastewater treatment are discussed extensively. Finally, this review unraveled some important perceptions on the prospects of CNC-based materials, especially in membrane applications for the treatment of wastewater.

A self-curing konjac glucomannan/CaCO3 coating for corrosion protection of AA5052 aluminum alloy in NaCl solution

A composite coating containing konjac glucomannan (KGM) and CaCO₃ was fabricated on AA5052 alloy through a self-curing process, and its surface morphology and component were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The effect of Ca(OH)₂ content on the protective property of the composite coating for aluminum alloy in 3.5 wt% NaCl solution was evaluated by electrochemical impedance spectroscopy measurements. Moreover, the inhibitory performance of the coating on the pitting corrosion of metal was examined by potentiodynamic polarization curves and atomic force microscopy (AFM). The images of scanning electron microscope show the composite coating with a thickness of 50 μm has well-defined branch-shaped structure. The FT-IR spectra confirm the successful fabrication of the polymer coating through the formation of CaCO₃. The results of electrochemical impedance spectroscopy suggest that the resistance of the aluminum alloy sample coated with such protective layer is improved by six orders of magnitude, compared with the bare metal. After 60 d of immersion, the polarization curve data and AFM analysis show the pitting corrosion occurring on AA5052 surface is prevented due to the barrier property of coating.

Conductive core-sheath calcium alginate/graphene composite fibers with polymeric ionic liquids as an intermediate

In this study, polymeric ionic liquid (PIL) was synthesized and used in the wet spinning of calcium alginate (CaAlg) fiber. PIL was used as an intermediate to coat graphene with outer layer of CaAlg fiber to obtain conductive core-sheath CaAlg/Graphene (CaAlg/G-PIL) fibers. This proposed blend enhances the properties of the fiber due to the π-π and cation-π interactions between PIL and graphene, and the electrostatic interactions between PIL and CaAlg. The composition and chemical structure of the composite fibers were characterized by infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and thermogravimetric analysis. The properties and applications of the composite fibers were characterized by tensile test and a series of electrical conductivity tests. The results show that the modification of PIL realizes non-covalent combination of CaAlg fiber with graphene, improving the electrical conductivity of the fiber.

Chemocatalytic Conversion of Cellulose into Key Platform Chemicals

Chemocatalytic transformation of lignocellulosic biomass to value-added chemicals has attracted global interest in order to build up sustainable societies. Cellulose, the first most abundant constituent of lignocellulosic biomass, has received extensive attention for its comprehensive utilization of resource, such as its catalytic conversion into high value-added chemicals and fuels (e.g., HMF, DMF, and isosorbide). However, the low reactivity of cellulose has prevented its use in chemical industry due to stable chemical structure and poor solubility in common solvents over the cellulose. Recently, homogeneous or heterogeneous catalysis for the conversion of cellulose has been expected to overcome this issue, because various types of pretreatment and homogeneous or heterogeneous catalysts can be designed and applied in a wide range of reaction conditions. In this review, we show the present situation and perspective of homogeneous or heterogeneous catalysis for the direct conversion of cellulose into useful platform chemicals.