Adsorption of platinum ion from "aged" aqueous solution: application and comparative study between purified MWCNTs and triphenylphosphine MWCNTs.

This study entails adsorption attempt of platinum ion from "aged" aqueous solution with purified multiwalled carbon nanotubes and tryphenylphosphine-linked multiwalled carbon nanotubes (1) and (2) (Tpp-MWCNTs (1) and Tpp-MWCNTs (2)). The aims were to produce and use purified MWCNTs, Tpp-MWCNTs (1) and (2) and compare their adsorption capacity. These adsorbents were characterised with SEM, FTIR, XPS, BET and zeta potential. Tpp-MWCNTs (1) and (2) differ by their atomic percentage content of phosphorus which is 0.7 and 2.6%, respectively. A commercial stock solution (1000 mg/L) of platinum was used for the batch adsorption experiments. The data revealed that the adsorption was dependent on the following parameters: pH, contact time and initial concentration. The adsorbents attained higher adsorption capacity at pH 2 with an initial concentration of 7.9 mg/L, adsorbent dose of 0.8 g/L, contact time of 60 min at room temperature (RT), whereas 48.25, 40.06 and 41.31 mg/g were adsorbed from 20 mg/L by purified MWCNTs, Tpp-MWCNTs (1) and (2), respectively. The results are quite interesting and show that purified MWCNTs are better than Tpp-MWCNTs under the experimental conditions. The data was best described by the Langmuir model and the adsorption process occurs on the surface monolayer of the adsorbents. The isotherm studies confirmed that the adsorption of platinum ion is favourable. The findings indicate that the practical adsorption of platinum ion using the adsorbents investigated is useful.