Recycling of textiles is of importance due to the large amount of waste generated from  the increasing consumption and use worldwide. Cotton-rich pre-consumer textiles are  considered as potential raw material for production of man-made regenerated fibres, but demands purification from the blends with synthetic fibres as well as the dyes and  finishing chemicals. In this study we explore the use of different pre-treatments of pre-consumer textiles to meet specific parameters for production of fibres in the cold  NaOH(aq) or cellulose carbamate process. The pre-treatments consisted of different  bleaching sequences and were performed on both uncoloured and coloured pre-consumer textiles. For the uncoloured textile, degree of polymerisation and amount of  inorganic content was efficiently reduced making the material suitable for both the cold  NaOH(aq) and the cellulose carbamate process. In case of the coloured textile, the pre-treatments were able to remove the dye and decrease the inorganic content as well as  reduce the degree of polymerisation but only sufficiently enough for production of fibres  in the cellulose carbamate process. The work was able to prove a fibre-to-fibre concept  while further optimisation of the regeneration steps is expected to improve the  mechanical properties of the produced fibres in future studies.

The application range of man-made cellulosic fibers is limited by the absence of cost- and manufacturing-efficient strategies for anisotropic hierarchical functionalization. Overcoming these bottlenecks is therefore pivotal in the pursuit of a future bio-based economy. Here, we demonstrate that colloidal silica nanoparticles (NPs), which are cheap, biocompatible and easy to chemically modify, enable the control of the cross-sectional morphology and surface topography of ionic liquid-spun cellulose fibers. These properties are tailored by the silica NPs' surface chemistry and their entry point during the wet-spinning process (dope solution ^DSiO₂ or coagulation bath ^CSiO₂). For ^CSiO₂-modified fibers, the coagulation mitigator dimethylsulphoxide allows for controlling the surface topography and the amalgamation of the silica NPs into the fiber matrix. For dope-modified fibers, we hypothesize that cellulose chains act as seeds for directed silica NP self-assembly. This results for ^DSiO₂ in discrete micron-sized rods, homogeneously distributed throughout the fiber and for glycidoxy-surface modified ^DSiO₂@GLYEO in nano-sized surface aggregates and a cross-sectional core-shell fiber morphology. Furthermore, the dope-modified fibers display outstanding strength and toughness, which are both characteristic features of biological biocomposites.

To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70:30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48-51%). No difference in the mechanical properties of the produced CF was observed.

A part of kraft lignin (KL) can be used as a value-added product without detracting the chemical recovery and the energy balance of the kraft mill. The focus of this study is the production of light-weight carbon fibres (CFS) from KL obtained by the LignoBoost process. For this purpose, crude KL and various cellulose products from kraft pulping of hardwood (HW) and softwood (SW) were dissolved in 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) and submitted to dry-jet wet-spun to obtain precursor fibres containing 70% KL and 30% cellulose, which were thermally stabilised and further converted by thermal treatments into CF. The initial and final products were characterised with respect to, e.g. mole mass distribution, thermal properties, tensile strength and tensile modulus determination. The optimised precursor fibres are smooth and flexible with similar mechanical properties as commercial textile fibres. The best CFS made had a tensile strength of 780 MPa and a tensile modulus of 68 GPa and are thus stronger and stiffer than those produced by melt-spinning of SW-based lignins alone. The new CFS based on dry-jet wet-spun precursors still have a high potential for further improvements.

We have found that the dissolution of cellulose in the binary mixed solvent tetrabutylammonium acetate/dimethyl sulfoxide follows a previously overlooked near-stoichiometric relationship such that one dissolved acetate ion is able to dissolve an amount of cellulose corresponding to about one glucose residue. The structure and dynamics of the resulting cellulose solutions were investigated using small-angle X-ray scattering (SAXS) and nuclear magnetic resonance techniques as well as molecular dynamics simulation. This yielded a detailed picture of the dissolution mechanism in which acetate ions form hydrogen bonds to cellulose and causes a diffuse solvation sheath of bulky tetrabutylammonium counterions to form. In turn, this leads to a steric repulsion that helps to keep the cellulose chains apart. Structural similarities to previously investigated cellulose solutions in aqueous tetrabutylammonium hydroxide were revealed by SAXS measurement. To what extent this corresponds to similarities in dissolution mechanism is discussed.

Certain ionic liquids are powerful cellulose solvents, but tend to be less effective when small-molecule hydrogen bond donors are present. This is generally attributed to competition with cellulose for hydrogen bonding opportunities to the anion of the ionic liquid. We show that the solubility of cellulose in dimethyl sulfoxide solutions of tetrabutylammonium acetate is less strongly affected by water than by ethanol on a molar basis, contrary to what can be expected based on hydrogen bond stoichiometry. Molecular dynamics simulations indicate that the higher tolerance to water is due to water-cellulose interactions that improves solvation of cellulose and, thereby, marginally favors dissolution. Through Kirkwood-Buff theory we show that water, but not ethanol, improves the solvent quality of DMSO and partly compensates for the loss of acetate-cellulose hydrogen bonds.

The dissolution of cellulose in tetrabutylammonium acetate (TBAAc)/dimethyl sulfoxide (DMSO) was studied combining experimental and simulation techniques. It was found that the dissolution limit at 40 °C corresponded to a molar ratio close to one acetate per cellulose anhydroglucose units. MD simulations suggested that the acetate ions bind to cellulose by dual hydrogen bonds. This effectively turns cellulose into a polyelectrolyte, attracting the bulky tetrabutylammonium (TBA+ ) counter ions, which prevent close contact between chains in the dissolved state. This hypothesis was tested by 1 Hand 13C-NMR spectroscopy, which confirmed that acetate forms hydrogen bonds to cellulose, and by diffusion NMR spectroscopy, which demonstrated a strong dynamic correlation between bound acetate and tetrabutylammonium in near-quantitative agreement with simulation. The present results suggest that offering hydrogen bonding to the acetate ions is the main driving force for dissolving cellulose and that the TBA+ counter ions form a diffuse layer around the acetate-decorated cellulose chains.