Room-temperature ionic liquids as candidate materials for produced water desalination: Experiments and molecular dynamic analysis

Abstract

Room-temperature ionic liquids (RTILs) have been promoted as “green” chemicals that can be used as alternatives to conventional volatile organic solvents. In addition to low volatilities, hydrophobicity for organic liquids and hydrophilicity for ions in RTILs lead to a wide spectrum of applications. ILs have recently been considered as alternative solvents to carboxylic acids and amines used for solvent extraction desalination (SED). RTILs are used in pairs of cations and anions that can significantly influence SED potentials. This study aimed to find an optimal combination of cationic and anionic RTIL as a desalination solvent through theoretical, experimental, and computational approaches. SED potentials in terms of water absorption and salt rejection were investigated for ten pairs of RTILs using different combinations of imidazolium and phosphonium cations with various anions. SED potentials were highly dependent on the anion type, with Tf2N showing the most promising SED potential. Imidazolium based RTILs exhibited better SED performances than phosphonium based RTILs in experiments. [BMIM][Tf2N] was recommended as a candidate SED-IL material, showing a water absorption and salt rejection of 1.73 % and 93.7 %, respectively. Molecular dynamics (MDs) simulation was implemented in parallel in order to examine and analyze intermolecular interactions that led to particular experimental observations.