Deep eutectic solvents as absorbents for VOC and VOC mixtures in static and dynamic processes

Abstract

Volatile organic compounds (VOCs) are primary air pollutants emitted directly from industries with adverse health effects and environmental impacts. Absorption is an attractive method to treat industrial exhaust loaded with VOCs, but most actual absorbents are often toxic and non-biodegradable. This work aims to evaluate deep eutectic solvents (DESs) as absorbents for VOCs using static and dynamic processes. The determination of vapour-liquid partition coefficient was performed for nine VOCs, from different chemical families, in eight hydrophilic and hydrophobic DESs, at different temperatures. The influence of VOC mixtures on DESs absorption capacities was determined for two different mixtures. DESs showed high absorption capacities for a variety of VOCs, without saturation even at high VOC concentration. The absorption capacities of DESs were also evaluated using a dynamic set-up which simulated an industrial absorption column. This set-up allows the modulation of the VOC flow rate, water content and column temperature. Both static and dynamic results are in good agreement. The DES based on tetrabutylammonium bromide and decanoic acid displayed high absorption capacities and versatility for the different tested VOCs, with a maximum enhancement of absorption reaching 60000-folds for 1-decene at 303 K, compared to water. The regeneration of the absorbent was carried out by several absorption/desorption cycles or after water removal, without loss of absorption capacity. The overall results show that DESs have characteristics that allow them to be considered as promising solvents for VOCs absorption.