Physico-chemical characterization of aqueous solutions of superbase ionic liquids with cellulose dissolution capability

Superbase-based ionic liquids 7-methyl-1,5,7-triazabicyclo[4.4.0]dec‑5-enium acetate, [mTBDH][OA c ], and 5-methyl-1,5,7-triaza-bicyclo[4.3.0]non-6-enium acetate, [mTBNH][OA c ], are good candidates to produce high performance cellulose fibres while presenting much easy spinnability and good recyclability, than the state-of-the-art ionic liquids. Nevertheless, the recovery of the IL from the aqueous spinning bath and its purification, which are both an economical and environmental necessity, are important aspects that are still not solved. Aiming to gather knowledge to recover and recycle superbase-ILs, the main goal of this work is the physicochemical characterization of the binary systems water + [mTBDH][OA c ] or [mTBNH][OA c ]. Measurements performed include solid-liquid equilibria, vapor-liquid equilibria, water activity, Kamlet−Taft solvatochromic parameters, densities, and viscosities. An experimental screening on possible hydrophobic extractants for the recuperation of the ionic liquids from aqueous solution was performed. Using butanol, an extraction efficiency of 37% for [mTBDH][OAc] was achieved. Better extraction efficiencies were achieved with chlorinated solvents, however, they seem to react with the ILs anion. Synopsis. The physicochemical characterization of mixtures of ILs and water is herein demonstrated to highlight the challenges in recovering hydrophilic ILs from aqueous solutions.