Synthesis, structural characterization and Cu(ii) adsorption behavior of manganite (γ-MnOOH) nanorods

Abstract

New alternatives for the removal of transition metal ions that present an environmental risk are required. The chemical adsorption of these ions on surfaces with chemisorbent properties represents a promising area of research. In this work, manganite (γ-MnOOH) nanorods were synthesized, with a surface area of 20.22 m² g⁻¹, pore size of 32.18 nm and pore volume of 0.1627 cm³ g⁻¹. After chemical and structural characterization of the manganite sample, it was evaluated as an adsorbent of Cu(II) from aqueous solution. The equilibrium adsorption data were well fitted by the Langmuir isotherm, and the results indicated that the maximum adsorption capacity of Cu(II) was 11.926 mg g⁻¹. Cu(II) ion adsorption on the manganite surface is a spontaneous and exothermic process (ΔG°< 0 and ΔH°< 0). The negative value of ΔS° suggests the stability of the adsorption process without structural change at the manganite–aqueous solution interface. A scheme for chemisorption of Cu(II) ions on the hydroxylated surface of manganite is proposed.