Modified multi-walled carbon nanotubes as effective Pt(IV) ions adsorbent with respect to analytical application

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.