In this study the adsorption and separation

In this study, the adsorption and BMI-1 inhibitor of [RhCl5(H2O)]2− and [IrCl6]2− was investigated by using synthesized quaternary diammonium-functionalized silica-based microparticles. Both batch adsorption and column separation experiments were performed. The effect of varying chain length between the diammonium centres was investigated with respect to the iridium loading capacity.
Experimental
Results and discussion
Conclusions Separation of rhodium(III) and iridium(IV) chlorido species in 6 M HCl was achieved by quaternary diammonium centres hosted on silica. In the column studies, [RhCl5(H2O)]2− was un-absorbed while [IrCl6]2− was retained on the materials suggesting specificity for [IrCl6]2−. This was explained on the basis of charge density effects. The functional chemistries hosted on silica were clearly confirmed by spectral and elemental analysis. The SEM images of the microparticles showed well defined amorphous material. BET measurements showed a decrease in the surface area of the silica with the functionalization, and it was observed that the smaller the diamine used in the functionalization the smaller the surface area due to ease of penetration into the pores of the microparticles. The surface area difference did not play a role with regards the loading capacity of the materials but the effect of the cations loaded onto the silica was the driving force. The loading capacities of the functional silica materials increased with the increase of the length of the methylene spacers between the two diammonium centres and this was explained by charge density effects. The anomaly of Si-QUAT DDMDA was rationalized based on the low level of functionalization. Equilibrium data suggested that multi-layer adsorption is possible. Kinetic data suggested that the mechanism of metal complexes uptake was dominated by pseudo first-order kinetic mechanism. It was also established that adsorption occurred by a chemical process between the metal complex anions and cations on the silica rather than physical adsorption.
Acknowledgements We would like to thank the Electron Microscopy Unit at Rhodes University and the DST/Mintek-NIC (Rhodes University) for the access to the SEM and the service provided for XPS analysis, respectively. We are grateful to the NRF-CPRR for funding. Avela Majavu is grateful to the NRF/RISA (SA) for the scholarship. We also thank the NMMU Research Themes Grant for funding. We also thank Dr Adeniyi Ogunlaja for editing the manuscript.