Modified multi-walled carbon nanotubes as effective Pt(IV) ions adsorbent with respect to analytical application
Joanna Dobrzyńska, Agnieszka Mróz, Rafał Olchowski, Emil Zięba, Ryszard Dobrowolski
Abstract
Multiwalled carbon nanotubes were oxidized with 14.5 mol L−1 nitric acid and modified with (3-aminopropyl)triethoxysilane (APTES), N-[3-(trimethoxysilyl)propyl]ethylenediamine (TMPED) and N-[3-(trimethoxysilyl)propyl]diethylenetriamine (TMPDET). The obtained materials were widely characterized, tested as Pt(IV) ions adsorbents and used for enrichment of Pt(IV) ions from digested geological samples before Pt(IV) determination by high-resolution continuum source atomic absorption spectrometry. The oxidation of MWCNTs and their following modification with amine functional groups led to the significant changes of their porosity parameters, introduction of oxygen- or nitrogen-rich functional groups on the carbonaceous surface as well as the increase of structural defects in the graphene layers. The amine-modified CNTs effectively and quickly adsorbed Pt(IV) ions in a relatively wide pH range. In the case of CNTs-TMPED and CNTs-TMPDET adsorption equilibrium was achieved within 1 h, while in the case of CNTs-APTES 6 h were required. The maximum static adsorption capacity towards Pt(IV) ions was estimated to 79 mg g−1, 200 mg g−1 and 260 mg g−1 for CNTs-APTES, CNTs-TMPED, CNTs-TMPDET, respectively. CNTs-TMPDET was selected for the enrichment of platinum. The proposed analytical procedure was characterized by the enrichment factor of 375 and limit of detection equal to 1.32 ng g−1.