Mesoporous nanomaterials based on manganese with different interlayer alkali cations: An efficient approach for the removal of Pb(II) and Cd(II) from aqueous medium

Abstract

The unique properties of nanomaterials provide a promising solution for environmental applications. Thus, three nanomaterials based on manganese birnessite-type in the form of well-structured nanowires and nanoflowers were synthesized by soft hydrothermal treatment, simple economical and without adding reagents or any other processes. Interlayer alkali cations (K+, H+ and Na+) inserted in the birnessite structure have demonstrated their effect on the structural and morphological properties of the nanomaterials and consequently on their metal ions removal efficiency. K-MnO2 nanowires with inserted K+ ions were characterized by high performance in short processing time (5 min) compared to other nanomaterials. The maximum adsorption quantities were respectively for Pb(II): K-MnO2 (300 mg/g)<Na-MnO2 (297.62 mg/g)<H-MnO2 (286.75 mg/g), and for Cd(II): K-MnO2 (228 mg/g)<Na-MnO2 (199 mg/g)<H-MnO2 (189.84 mg/g). The performance was high and stable while the nanomaterials got regenerated without losing the adsorption capacity. X-ray photoelectron spectroscopy revealed that the heavy metal ions got adsorbed onto the nanomaterials as PbO and Cd(OH)2. These results confirm the performance of non-agglomerated nanowires and nanoflowers nanomaterials based on manganese in an efficient kinetically fast metal ions removal with important stability and adsorption capacity.