A review on deep eutectic solvents: Physiochemical properties and its application as an absorbent for sulfur dioxide

Solvent plays an important role as a green chemistry. The solvents must meet certain criteria such as biodegradable, recyclability, low cost, availability and non-toxic to be qualified as a green medium. To date, solvents which are labelled as green medium are very limited. The new family of ionic fluids, called deep eutectic solvents (DESs) are now rapidly developing in terms of green research. A DES is a fluid that typically consists of two or three components that are secure and cost-friendly, able to associate frequently by itself through interactions of the hydrogen bond, creating a eutectic mixture with a melting point lower than that of each component. The DESs tend to be liquid at temperatures below 373.15 K. Most of the DESs exhibits similar physico-chemical properties to the traditionally used ionic liquids, adding in the advantage that it is much cheaper and environmentally friendlier. Thus, DESs are increasingly involved in many research areas, this is because of the advantage that it carries compared to ionic liquids itself especially in sulfur dioxide gas separation process. The main aim of this review is to determine and summarize the recent research and the major contributions of DESs especially in sulfur dioxide extraction and absorption.