Effect of heat treatment on the physico-chemical properties and catalytic activity of manganese nodules leached residue towards decomposition of hydrogen peroxide

Abstract

The effect of calcination temperature on the physico-chemical characterization of manganese nodule leached residue (MNLR) and water-washed manganese nodule leached residue (WMNLR) has been investigated on the basis of chemical analysis, XRD, TG-DTA, FTIR, surface hydroxyl groups, surface oxygen, reducing and oxidizing sites, surface area. XRD and IR confirm the presence of amorphous iron oxyhydroxides, δ-MnO 2, which are converted to α-Fe 2O 3 and γ-Mn 2O 3 phases above 400 °C of calcination, respectively. A solid solution of Fe 2O 3 and Mn 2O 3 is formed above 700 °C. The surface area, surface hydroxyl group, surface oxygen, reducing and oxidizing sites increase with the increase in calcination temperature up to 400 °C and then decrease with further rise in calcination temperature up to 700 °C. The catalytic activity of the sample towards H 2O 2 decomposition shows the similar trend as surface properties. A suitable Mn 3+ Mn 4+ couple favours H 2O 2 decomposition reaction. The activity has been correlated with various physico-chemical properties.