Equilibrium and kinetics of extraction of butyric acid (BA) into solvent impregnated resins (SIRs) have been studied. Microporous Amber lite XAD-1180N was impregnated with a new ammonium ionic liquid (IL) trialkylmethylammonium-bis(2,4,4-trimethylpentyl)phosphinate or with its solution in dodecane. No difference in BA extraction equilibrium between the free organic phases and the same phase impregnated in SIRs has been observed. This shows that the polymer matrix of the resin has no significant impact on extraction properties of impregnated IL SIR impregnated with IL solution in dodecane exhibit faster extraction kinetics with lower saturation times compared to SIR with pure IL what can be attributed to lower viscosity of the solvent with diluent. The kinetics of extraction into used SIRs with a mean particle diameter of about 660 mu m was fast and 95% of their equilibrium saturation was achieved in less than 350 s which is one order of magnitude faster than achieved in adsorption into resins. The value of the effective diffusion coefficient in extraction is larger than in stripping, suggesting that kinetics of the stripping is influenced by the slower decomposition of the complex of BA with IL (C) 2011 Elsevier Ltd. All rights reserved.