Norway spruce wood was mechanically pulverized to varying degrees. The solubility of the wood samples, in a range of common ionic and molecular solvents, was quantified using a novel 31 P NMR technique. The results show that intact wood is not soluble under mild treatment conditions, in cellulose-dissolving or swelling solvents.

We investigated the toxicological effect of seven novel cholinium, guanidinium, and tetramethylguanidinium carboxylate ionic liquids (ILs) from an ecotoxicological point of view. The emphasis was on the potential structure-toxicity dependency of these surface-active ILs in aqueous environment. The median effective concentrations (EC50) were defined for each IL using Vibrio (Aliivibrio) fischeri marine bacteria. Dipalmitoylphosphatidylcholine (DPPC) liposomes were used as biomimetic lipid membranes to study the interactions between the surface-active ILs and the liposomes. The interactions were investigated by following the change in the DPPC phase transition behaviour using differential scanning calorimetry (DSC). Critical micelle concentrations for the ILs were determined to clarify the analysis of the toxicity and the interaction results. Increasing anion alkyl chain length increased the toxicity, whereas branching of the chain decreased the toxicity of the ILs. The toxicity of the ILs in this study was mainly determined by the surface-active anions, while cations induced a minor impact on the toxicity. In the DSC experiments the same trend was observed for all the studied anions, whereas the cations seemed to induce more variable impact on the phase transition behaviour. Toxicity measurements combined with liposome interaction studies can provide a valuable tool for assessing the mechanism of toxicity.

For ionic liquid processes to be adopted by industry there are two main challenges. First is the enormous capital and running costs when using expensive ionic liquids, compared to molecular solvents. In addition, if ionic liquids are disposed of there is great potential for environmental damage. These factors can be mitigated, by recycling ionic liquids in any process or product life cycle, as far as possible. This chapter reviews the topic of ionic liquid recycling, covering the main methods of recycling in the academic and patent literature. These include the classical methods of recycling compounds such as distillation, phase separation, extraction and crystallization. Adsorption and membrane methods are also covered. The various mechanisms of distillation will be covered, including distillation of ion pairs or dissociation of ionic liquids into volatile neutral species, which vaporize and recondense. The topic of aqueous biphasic systems is also covered, under the general method of phase separation. It is shown how even water miscible ionic liquids can be separated with the use of kosmotropic salts, commonly described in the Hofmeister series. Throughout this discussion the applicability to recycling of ionic liquids on an industrial scale is also considered.