The effect of chelating agents on the formation of manganese oxide (MnO) in the synthesis of sodium manganese oxide (Na2Mn3O7)

Abstract

This current study successfully synthesized Na2Mn3O7 in two steps. Firstly, the synthesis of MnO from NaCl and MnCl2.4H2O precursors. NaCl was mixed with citric acid as a chelating agent, while MnCl2.4H2O was mixed with two types of chelating agents (citric acid and 1% chitosan). The solutions of [NaCl-a chelating agent] and [MnCl2.4H2O-a chelating agent] were stirred for ±2 hours. The solutions were hydrothermally heated at 150°C for 6 hours and then calcined at 800°C for 1 hour in a nitrogen condition. The MnO presence was then analyzed using an XRD method. As a comparison, another sample was water leached. Then, it was examined by an XRD method. Secondly, the synthesis of Na2Mn3O7 from MnO and Na2CO3 powder was carried out through a solid method. The calcination was carried out at 800°C for ±3 hours in an oxidizing atmosphere. The XRD results showed the presence of Na2Mn3O7 in the final products of both samples. Based on these experimental results, the sample [NaCl-citric acid; MnCl2.4H2O-1%chitosan] showed higher purity than the sample [NaCl-citric acid; MnCl2.4H2O-citric acid], so that it had a higher intensity of the Na2Mn3O7 phase than the sample [NaCl-citric acid; MnCl2.4H2O-citric acid]. Besides, the Cl- ions removal after calcination greatly affected the intensity of the MnO and Na2Mn3O7 formed.