Four different structurally modified sulphoxides in ionic liquid were chosen for the development of efficient method for the extraction of thorium from aqueous acidic waste solutions. Novel piperidinium ionic liquid based solvent systems were found to be more efficient than the conventional imidazolium based systems. The extraction of thorium was predominated by ‘cation exchange’ mechanism via Th(NO3)·3SO3+ species. The trend in extraction efficiency followed APSO>BMSO>DHSO>DISO. The phenyl substituted sulphoxides showed higher affinity for thorium due to a combination of steric as well as electronic factors. All the extraction processes were thermodynamically spontaneous without participation of NTf2− ion in the extracted thorium complex. 0.05M oxalic acid was found to be suitable for almost quantitative stripping of thorium from loaded organic phase. APSO in ionic liquid was found to be radiolytically stable among the other four sulphoxides in ionic liquid. Display omitted •Sulphoxides in piperidinium based ionic liquid: highly efficient system for the extraction of thorium•Cation exchange via Th(NO3). 3SO3+ species•Phenyl substituted sulphoxides have more extraction efficiency: Steric and Resonance factors•APSO highly radio resistant and thorium selective•Oxalic acid effective strippant