Cellulose gels produced in room temperature ionic liquids by ionizing radiation

Direct grafting of cellulose nanocrystals with poly(ionic liquids) via Gamma-ray irradiation and their utilization for adsorptive removal of CR

In this work, a simple but effective method based on Gamma-ray initiated polymerization was reported for the first time through direct irradiation of CNCs and ionic liquid monomer to obtain poly (ionic liquids) functionalized CNCs (IL@CNCs). The adsorptive removal of Congo red (CR) from aqueous solution by IL@CNCs was also examined and the influence of contact time, pH values, initial concentrations and temperature on adsorption behavior was investigated in detail. Under the same adsorption conditions, the adsorption capacity was increased from 59.72 mg/g (CNCs) to 195.83 mg/g (IL@CNCs). The results of the adsorption isotherm and adsorption kinetics showed that the experimental data were more suitable to be described by the Freundlich isotherm adsorption model and the pseudo-second-order model. The adsorption process of CR on the surface of the adsorbent was endothermic and spontaneous. When the aqueous solution was acidic, it was more conducive to the adsorption of CR. At 100% breakthrough, the value of adsorption capacity is 199.95 mg/g and the value of partition coefficient is 9.64. Moreover, the adsorption capacity is expected to be further improved through adjustment of polymerization parameters and this method can also be used for preparation other poly (ionic liquids) modified composites.

Cellulose ionogels, a perspective of the last decade: A review

Cellulose ionogels have been extensively studied due to the variability of their properties and applications. The capability of trapping an ionic liquid in a biodegradable solid matrix without losing its properties makes this type of material a promising substitute for fossil fuel-derived materials. The possibility to formulate ionogels chemically or physically, to choose between different ionic liquids, cellulose types, and the possibility to add a wide range of additives, make these ionogels an adaptable material that can be modified for each target application in many fields such as medicine, energy storage, electrochemistry, etc. The aim of this review is to show its versatility and to provide a summary picture of the advances in the field of cellulose ionogels formulation (chemical or physical methods), as well as their potential applications, so this review will serve as a stimulus for research on these materials in the future.

Ultra-sonication assisted cross-linking of cellulose polymers

Cross-linked cellulose-epichlorohydrin polymers were synthesized by a conventional heating with stirring (C-EP heating) and a parallel process using ultra-sonication (C-EP sonication) in the presence of aqueous ammonia. Structural characterization of modified cellulose was carried out using FTIR/¹³C solid state NMR spectroscopy and thermal methods (DSC and TGA). Evidence of products with variable textural properties and morphology was supported by nitrogen gas adsorption, solvent swelling, and microscopy (SEM, TEM) results. C-EP sonication possess greater cross-linker content judging by the loss of the cellulose fibril structure which was facilitated by acoustic cavitation effects due to ultra-sonication. Equilibrium sorption studies in aqueous solution with 2-naphthoxy acetic acid (NAA) revealed that C-EP heating had slightly greater sorption capacity than C-EP sonication at alkaline pH. By contrast, C-EP sonication had greater uptake of NAA at acidic pH. Kinetic uptake studies at pH 3 is described by the pseudo-second order model, where the surface sites of C-EP heating became saturated within ca. 75 min; whereas, ca. 350 min occurred for C-EP sonication. This study demonstrates that the yield of sonication assisted cross-linking of cellulose is greater with improved adsorption properties. The study also reveals the utility of sonication assisted synthesis for the valorization and utilization of cellulose modified materials.

Radiation-induced solidification of ionic liquid under extreme electric field

An extreme electric field on the order of 10(10) V m(-1) was applied to the free surface of an ionic liquid to cause electric-field-induced evaporation of molecular ions from the liquid. The point of ion emission was observed in situ using a TEM. The resulting electrospray emission process was observed to create nanoscale high-aspect-ratio dendritic features that were aligned with the direction of the electric field. Upon removal of the stressing field the features were seen to remain, indicating that the ionic liquid residue was solidified or gelled. Similar electrospray experiments performed in a field-emission scanning electron microscope revealed that the features are created when the high-energy electron beam damages the molecular structure of the ionic liquid. While the electric field does not play a direct role in the fluid modification, the electric stress was critical in detecting the liquid property change. It is only because the electric stress mechanically elongated the fluid during the electrospray process and these obviously non-liquid structures persisted when the field was removed that the damage was evident. This evidence of ionic liquid radiation damage may have significant bearing on electrospray devices where it is possible to produce high-energy secondary electrons through surface impacts of emitted ions downstream of the emitter. Any such impacts that are in close proximity could see reflected secondary electrons impact the emitter causing gelling of the ionic liquid.