Three quaternary diammonium-functionalized polyvinylbenzyl chloride nanofibers were prepared using hexamethylenediamine (HMDA) quaternized with methyl, ethyl and benzyl groups to produce F-QUAT HMDA-methyl, F-QUAT HMDA-ethyl and F-QUAT HMDA-benzyl, respectively. The synthesized nanofibers were characterized by means of FTIR, XPS, SEM, BET surface area, thermogravimetric analysis and elemental analysis. The materials were used to investigate the adsorption and separation of [RhCl5(H2O)](2-) and [IrCl6](2-). Adsorption isothermal batch studies were conducted on both metal ion complexes ([RhCl5(H2O)](2-) and [IrCl6](2-)) using single metal aqueous solutions. The Langmuir isotherm confirmed monolayer adsorption for the uptake of both [RhCl5(H2O)](2-) and [IrCl6](2-) using F-QUAT HMDA-ethyl, F-QUAT HMDA-methyl and F-QUAT HMDA-benzyl. The adsorption process of these materials obeyed the pseudo second-order kinetics, suggesting that chemisorption was be the rate determining step. Column studies were conducted for a binary mixture of the metal ions chlorido species, and the iridium loading capacities of 15.2(0.8) mg/g, 9.7(0.7) mg/g and 42.9(0.7) mg/g were obtained for F-QUAT HMDA-methyl, F-QUAT HMDA-ethyl and F-QUAT HMDA-benzyl, respectively. This order was interpreted on the basis of inductive effects of the three quaternizing groups. The results provided important insight into the effect of derivatizing the cationic center on the loading capacity for [IrCl6](2-). This study presents truly iridium-specific sorption materials which can be applied to solutions of low grade ores or secondary raw materials of PGMs. (C) 2015 Elsevier Ltd. All rights reserved.