Synthesis of MWCNT/MnO₂ and their application for simultaneous oxidation of arsenite and sorption of arsenate

It is well known that arsenite [As(III)] is less effectively removed than arsenate [As(V)] by most treatment technologies. Thus, pre-oxidation of As(III) to As(V) is required prior to adsorption. Here, the oxidation properties of manganese oxides with adsorption features of multiwall carbon nanotubes (MWCNTs) have been combined in a composite of MWCNT/MnO₂. The composite was characterized by Fourier transform infrared absorption spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and energy dispersive X-ray (EDX) and X-ray diffraction (XRD). In batch culture experiments, MWCNTs and the MWCNT/MnO₂ composite were examined for As(III) and As(V). The results reveal that MnO₂ in the composite plays a key role in enhancing As(III) removal and As(III) removal is not as effective as As(V) removal for MWCNTs. The retention of arsenite and arsenate is slightly pH dependent. The reported composite can be regenerated as it was confirmed by SEM and EDX analysis. The study could be considered as a model of preparation and investigation of a multifunctional material that can be used in wastewater treatment for removal of arsenic.