Thermal decomposition behavior of boron-bearing iron concentrate under nitrogen atmosphere: Kinetics, mineral phase transformation and microstructure evolution

Pyrometallurgical separation is an effective method for processing boron-containing iron concentrate, but the thermal behavior of boron-bearing minerals during roasting remains unclear. The thermal characteristics of boron-containing iron concentrate in a nitrogen atmosphere were systematically studied using synchronous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and other analytical methods. The results show that the thermal treatment process can be divided into four stages, with the most significant weight loss occurring between 446.05 °C and 643.42 °C. During this stage, szaibelyite and serpentine undergo dehydration decomposition reactions, forming suanite and olivine. As the decomposition temperature increases, cracks appear throughout the particles of suanite and olivine, while magnetite and ludwigite remain stable, with no changes in their phase or microstructure. Additionally, the thermal treatment kinetics analysis shows that the most probable reaction mechanism for the thermal treatment of boron-containing iron concentrate follows the random nucleation and subsequent growth model (A₁), with the integral form G(α) = −ln(1-α). The apparent activation energy of the reaction is 151.09 kJ/mol, and the pre-exponential factor is 1.23 × 10¹² min⁻¹. These findings provide an important theoretical basis for further understanding the thermal treatment behavior of boron-containing iron concentrate and offer valuable insights for its application in high-temperature treatments.