BACKGROUNDIon exchange has been reported as a feasible process for naphthenic acid (NA) separation from distillate fractions of acidic crude oil. In this work a cross-linked polymer functionalised with amino groups was designed for NA separation from organic solvents and the derived nanoparticles (PP) were used in the preparation of magnetic composite particles (MCP). Particles were characterised for size, zeta potential and amino group concentration; equilibrium and kinetic results were obtained over a wide range of conditions. RESULTSLoading capacity of MCP was higher than that of PP. Both particles extracted 80-92% NA; extraction using MCP reached equilibrium in less than 10min whereas PP required hours. MCP loading capacity was an order of magnitude higher than that of commercial particles and equilibration time more than one order of magnitude lower. Kinetics of extraction, particle loading and the mechanism of extraction are discussed in terms of particle characteristics. Recovery of NA from MCP reached 98% and particles could be reused. CONCLUSIONSMCP extracted more than 90% NA in a few minutes and their loading capacity was an order of magnitude higher than that of commercial particles. (c) 2014 Society of Chemical Industry.