Dissolution of South African Eucalyptus sawdust wood in [Emim][OAc]/Co-solvent mixtures

Abstract

The paper presents a method of obtaining wood cellulose by dissolution of eucalyptus sawdust in a mixture of ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [Emim][OAc] together with co-solvents; dimethylformamide (DMF) and dimethylsulphoxide (DMSO), as a potential alternative to traditional non-ecological processes involving the use of volatile organic solvents or harsh chemicals. The results showed that a fraction of the wood sawdust dissolved in the mixture of [Emim][OAc] and co-solvents, and cellulose precipitated from the mixture after addition of a water /acetone mixture. The yields for the cellulose precipitates were 32.5, 17.8 % and 7.2 % for the [Emim][OAc]/DMF mixture, [Emim][OAc]/DMSO and neat [Emim][OAc], respectively. Analysis of the cellulose precipitates by FTIR spectroscopy confirmed the presence of the dominant amorphous cellulose II anomer in the regenerated cellulose. The changes in the crystalline structure of the regenerated cellulose was confirmed by comparing the XRD analytical data of the untreated sawdust wood with that of the of the regenerated cellulose samples: and it was found that the cellulose structure transformed from crystalline to amorphous after dissolution and regeneration. Scanning electron microscopy indicated that the surface morphology of the regenerated cellulose samples exhibited a structure that was rather loose, disordered and curly: this was probably due to removal of lignin and decrease in cellulose crystallinity.