Biologische Abbaubarkeit von ionischen Flüssigkeiten - Testverfahren und strukturelles Design

Adsorption of ionic liquids onto an activated carbon: kinetic modeling studies

In this study, the uptake of hydrophobic bromide-based ionic liquids (ILs) (imidazolium, pyrrolidinium, and pyridinium) from aqueous solutions onto granulated and fabric-based microporous activated carbons (ACs). Surface characterization study shows that both ACs have basic pHpzc, like 8.7 for granulated AC and 8.0 for fabric AC. Granulated AC have ten times higher phenolic groups 0.2 meq g^-1 compared to fabric AC which is 0.03 meq g^-1. The kinetics of adsorption was remarkably slower for ILs on granulated/fabric AC than milled one. We also studied the effect of AC size on the rate of adsorption in the operating conditions. In order to improve the adsorption kinetics of ILs with ACs, different phenomenological and empirical kinetic models like as pseudo-first order, Boyd model, pseudo-second-order diffusion model and Elovich were applied on the kinetic experimental data. The analysis of kinetic specified that the adsorption mechanism of ILs onto ACs is controlled mainly by the mass transfer through the pores of ACs. So, the selection of appropriate adsorbent particle size of AC plays a main role for the development of viable IL adsorption. Graphical abstract ᅟ.

Composition and structural effects on the adsorption of ionic liquids onto activated carbon

The applications and variety of ionic liquids (ILs) have increased during the last few years, and their use at a large scale will require their removal/recovery from wastewater streams. Adsorption on activated carbons (ACs) has been recently proposed for this aim and this work presents a systematic analysis of the influence of the IL chemical structures (cation side chain, head group, anion type and the presence of functional groups) on their adsorption onto commercial AC from water solution. Here, the adsorption of 21 new ILs, which include imidazolium-, pyridinium-, pyrrolidinium-, piperidinium-, phosphonium- and ammonium-based cations and different hydrophobic and hydrophilic anions, has been experimentally measured. This contribution allows an expansion of the range of IL compounds studied in previous works, and permits a better understanding of the influence of the IL structures through the adsorption on AC. In addition, the COSMO-RS method was used to analyze the measured adsorption isotherms, allowing the understanding of the role of the cationic and anionic structures in the adsorption process, in terms of the different interactions between the IL compound and AC surface/water solvent. The results of this work provide new insights for the development of adsorption as an effective operation to remove/recover ILs with very different chemical nature from water solution.

Ionic liquids--promising but challenging solvents for homogeneous derivatization of cellulose

In the past decade, ionic liquids (ILs) have received enormous interest as solvents for cellulose. They have been studied intensively for fractionation and biorefining of lignocellulosic biomass, for dissolution of the polysaccharide, for preparation of cellulosic fibers, and in particular as reaction media for the homogeneous preparation of highly engineered polysaccharide derivatives. ILs show great potential for application on a commercial scale regarding recyclability, high dissolution power, and their broad structural diversity. However, a critical analysis reveals that these promising features are combined with serious drawbacks that need to be addressed in order to utilize ILs for the efficient synthesis of cellulose derivatives. This review presents a comprehensive overview about chemical modification of cellulose in ILs. Difficulties encountered thereby are discussed critically and current as well as future developments in this field of polysaccharide research are outlined.