Desulfurization kinetics and mineral phase evolution of bauxite water slurry (BWS) electrolysis

• The desulfurization ratio in NaCl solution was higher than that in NaOH.
• The carphosiderite was found in bauxite after electrolysis in NaCl.
• Sulfur removal increase and then decrease with current density in NaOH.
• Desulfurization ratio decreased with increasing of pH value of electrolyte.

The desulfurization kinetics and mineral phase evolution from bauxite water slurry (BWS) electrolysis were examined. The results showed that the desulfurization ratio in NaCl system increased with current density, and reached up to 96% at 0.22 A/cm2. In contrast, the desulfurization ratio in NaOH system increased firstly, and then decreased with current density, which was relative to the lifetime of oxidizing media from electrolysis. It was noted that pH value of electrolyte had some crucial effects on oxidant species and surface of FeS2, and thus the desulfurization ratio increased with the decrease in pH value of electrolyte. According to desulfurization kinetics, electrolysis desulfurization in NaCl solution was controlled by internal diffusion, and the apparent activation energy was 18.68 kJ/mol. However, electrolysis desulfurization process in NaOH solution was controlled by interface chemical reaction, and the apparent activation energy was 25.77 kJ/mol.