Work

Effect of calcium carbonate on the thermodynamics and kinetics of lead sulfide carbothermic reduction

Year: 2026

Type: article

Abstract: The effect of calcium carbonate on the thermodynamics and apparent kinetics of lead sulfide (PbS) carbothermic reduction was investigated in the PbS–Na 2 CO 3 –C and PbS–Na 2 CO 3 –CaCO 3 –C systems at 800–1100 °C. Thermodynamic analysis included Gibbs free energy calculations and multiphase equilibrium modeling, while kinetic behavior was evaluated through time-resolved gas analysis and TG–DTG–DSC measurements. Equilibrium calculations revealed predominant Na 2 S formation in the CaCO 3 -free system and CaS formation in the CaCO 3 -containing system. At 800 °C, the calculated equilibrium amount of metallic lead increased from 804.29 to 999.83 mol upon CaCO 3 addition, based on 1000 mol of initial PbS. Sodium carbonate remained largely unconsumed in the CaCO 3 -containing system. Experimental results demonstrated a pronounced temperature-dependent effect of CaCO 3 . At 800 °C, the apparent reaction extent (α app ) was 70.6% with CaCO 3 and 74.9% without it. At 900, 1000, and 1100 °C, α app reached 96.4%, 97.9%, and 99.5%, respectively, in the CaCO 3 -containing system, accompanied by higher apparent reaction rates. The corresponding apparent activation energies were 32.0 and 52.9 kJ·mol − 1 , indicating stronger temperature sensitivity with CaCO 3 addition. These findings demonstrate that CaCO 3 modifies sulfur distribution and the apparent kinetic behavior of PbS-containing systems.

Source: Scientific Reports

DOI: 10.1038/s41598-026-79393-2