1-Butyl-2,3-dimethylimidazolium hexafluorophosphate as a green solvent for the extraction of endosulfan from aqueous solution using supported liquid membrane

• Endosulfan was separated from aqueous phase using supported liquid membrane.
• 1-Butyl-2,3-dimethylimidazolium hexafluorophosphate was used as the membrane phase.
• 72% of endosulfan permeation was obtained using 0.1 M NaOH as stripping agent.
• The rate of permeation decreased with increase in pH from 2 to 10.
• The stability and performance of the SILM was studied via SEM and EDX analysis.

In this study, selective separation of α-endosulfan (ES) was carried out via supported liquid membrane (SLM) using the ionic liquid 1-butyl-2,3-dimethylimidazolium hexafluorophosphate [C4DMIM][PF6] as the membrane phase. The SLM was prepared using hydrophilic polyvinylidene fluoride (PVDF) support immobilized in the IL [C4DMIM][PF6] and henceforth known as supported ionic liquid membrane (SILM). Range of permeabilities were observed by varying different operating parameters such as initial feed concentration, pH, stirring speed and membrane flux. Effect of feed concentration was studied by varying the ES concentration between 10 and 50 mg L−1. A maximum of 72% (at feed pH = 6.5) of endosulfan permeation was observed using 0.1 M NaOH as stripping agent after 30 h of experimental run. The rate of permeation decreases with increase in pH from 2 to 10 (87–55%). Control experiments were also carried out with blank membranes (without IL). Different stripping agents such as 0.1 M NaOH, 0.1 M KOH and 0.1 M NH4OH were successfully used and their performance was reported. The transport mechanism involving SILMs has also been elucidated. Characterization of SILM using SEM, EDX and FTIR was also carried out in detail. The operational stability of the SILM was tested continuously for an experimental run of 30 h.