Catalytic role of sodium carbonate in reduction of ferromanganese spinel

Abstract

This present study investigated the catalytic effect of Na2CO3 on the reduction of ferromanganese spinel (MnFe2O4) using biochar as reducing agent. The reduction of the MnFe2O4-biochar composite briquettes at 1050 °C for 30 min showed that the iron metallization degree of the reduced briquettes increased from 61.1% to 84.2%, with significant decrease of initial reduction temperature due to the addition of 5 wt% Na2CO3. There also existed higher CO and CO2 concentrations in the off-gas in the presence of Na2CO3. According to the first-principles calculations, these differences were attributed to the reaction between Na2CO3 and carbon which produced oxygen vacancies on the Na2CO3 surface. These vacancies were then filled by the oxygen atoms of CO2, forming CO which was desorbed from the surface of Na2CO3 before it participated in the reduction. By creating oxygen vacancies through its reaction with carbon, Na2CO3 played a catalytic role in the reduction process.