Carbothermal reduction of red mud for iron extraction and sodium removal

In this work, the technology of carbothermic reduction was used to extract iron and remove sodium from red mud. The effect of various parameters like reduction time, temperature, and basicity on melting separation and de-alkalization was studied. At the optimum reduction temperature of 1,450 degrees C, the basicity of 1.5, and reduction time of 12 min, the metallization rate and sodium removal reach 96.63 and 90.62%, respectively. Melting and separating conditions gradually improve with the temperature increasing from 1,350 to 1,450 degrees C. At high basicity (R = 2), the condition of melting and separation is poor due to a large amount of Ca2Al2SiO7 produced, which has a high melting point. Subsequently, in order to explore the aggregation state of iron ions under different basicities, the microstructure of pellets was observed by scanning electron microscopy. It was found that when the basicity is 1.5, the aggregation degree of iron particles significantly increases. X-ray diffraction (XRD) analyses of the reduced pellets indicated that at different basicities, the final phase composition of reduced pellets is mainly Ca2Al2SiO7, which is the basic material for preparing cement materials and glass ceramics. Thus, the carbothermic-reduction method is a sustainable process for dealing with the Bayer bauxite residue.

Automated summary

This work investigated the extraction of iron and removal of sodium from red mud using the technology of carbothermic reduction. The effects of various parameters on melting separation and de-alkalization were studied. Optimal conditions for metallization rate and sodium removal were achieved at a reduction temperature of 1,450 degrees C, basicity of 1.5, and reduction time of 12 min. The microstructure of the pellets revealed increased aggregation of iron particles at a basicity of 1.5. X-ray diffraction analysis indicated that the final phase composition of the reduced pellets is mainly Ca2Al2SiO7, which has applications in cement materials and glass ceramics.