Efficient SO2 absorption by renewable choline chloride-glycerol deep eutectic solvents

The utilization of cheap and renewable materials is an important topic in green chemistry. In this work we studied the absorption of SO2 by choline chloride (ChCl)-glycerol deep eutectic solvents (DESs) at various temperatures and SO2 partial pressures, and the molar ratios of ChCl and glycerol ranged from 1 : 4 to 1 : 1. It was demonstrated that the solubility of SO2 in the DESs increased as the ChCl concentration in the DESs increased. The SO2 absorption capacity of the DESs with a ChCl-glycerol molar ratio of 1 : 1 could be as high as 0.678 g SO2 per g DES at 20 degrees C and 1 atm. Moreover, the absorbed SO2 could be easily released, and their excellent properties of high absorption capacity and rapid absorption/desorption rates remained during the five consecutive absorption/desorption cycles. The Henry's constants of SO2 in the DESs were calculated based on the solubility data.