Extraction and recovery of phenolic compounds from aqueous solution by thermo-separating magnetic ionic liquid aqueous two-phase system

Abstract

• Thermo-separating magnetic ionic liquids are discovered for the first time. • The first thermo-separating magnetic ionic liquid aqueous two-phase system is successfully developed. • This system is successfully applied to remove phenols from aqueous solution. • MIL and phenolic compound are simultaneously recovered simply by heating. • MIL can be recycled for at least 6 times with satisfactory performances. In this report, thermo-separating magnetic ionic liquids (MILs) were discovered for the first time. Two Polypropylene glycol 600 (PPG 600 ) based thermo-separating MILs were synthesized, characterized and successfully applied to construct the first reported thermo-separating magnetic ionic liquid aqueous two-phase system (MILATPS). This novelly proposed thermo-separating MILATPS combined the advantages of rapid extraction, volatile organic solvent free, magnetic separation and thermo-recovery of MIL in an extraction process. Phase behaviors and extraction-recovery processes of phenol, o -cresol and m -cresol were systematically studied. Several influencing factors on phenolic compound extraction efficiencies were detailedly investigated and optimized. Under optimal conditions, both two synthesized thermo-separating MILs revealed good performances with extraction efficiencies higher than 90%. Scale-up studies were also satisfactory. Additionally, both high purities of MILs and phenolic compounds could be ideally recovered simply by heating and the recoveries of phenolic compounds were higher than 95% for all systems. Furthermore, the two MILs could be recycled for at least 6 times with steadily high extraction efficiencies. This novelly proposed thermo-separating MILATPS is simple and green method which is showing great potential in an extraction-recovery process and the industrial treatment of phenolic wastewater.