Recovery of mixture of hydroxyethylammonium carboxylate protic ionic liquids from sugarcane pretreatment liquor using activated carbon in a fixed bed column

Abstract

Integrated strategies using fixed bed columns can facilitate the recovery of protic ionic liquids (PILs) used in the pretreatment of lignocellulosic biomass. In this study, we investigated the adsorption of 2-hydroxyethylammonium acetate [Mea][Ac] and 2-hydroxyethylammonium hexanoate [Mea][Hex] on activated carbon in a fixed bed column for recovering the PILs mixture present in the liquor of the pretreatment. Breakthrough curves were determined experimentally. Breakthrough time (tb), exhaustion time (te), difference between tb and te, adsorption efficiency (ϕads), column efficiency (ϕcol) and qe equilibrium capacity were evaluated as a function of simultaneous variations in superficial velocity (vs) and temperature (T) using a central composite rotatable design. The optimum conditions for PIL purification were vs = 1.66 cm/min (Q = 1.3 mL/min) and T = 20 °C. After selection of optimum operating conditions, PILs separation was evaluated in a model solution and sugarcane pretreatment liquor, with similar intervals for recover of PILs. This is the first study to develop a successful proof of concept of mixture PILs [Mea][Ac]/[Mea][Hex] recovery from sugarcane straw pretreatment liquor in a fixed-bed column of activated carbon. The results indicate that the method has great potential for industrial application.