Evaporation Rate and Kinetic Mechanism of Lead Sulfide Under Vacuum

Lead sulfide (PbS) has substantial potential for applications in many fields, such as optical devices and solar cells. Although PbS can be obtained from complex lead-antimony sulfide ores by vacuum distillation, the evaporation mechanism of PbS under vacuum is still unclear. Herein, the evaporation kinetics of PbS at 973 K to 1173 K and 5 to 1000 Pa were investigated using a vacuum thermogravimetric furnace. The practical evaporation rate of PbS was obtained through linear and nonlinear fitting of the experimental data compared with the original theoretical evaporation rate and corrected for the Langmuir maximum evaporation coefficient. The evaporation coefficients and critical pressures of PbS at 973 K, 1023 K, 1073 K, 1123 K, and 1173 K were 0.5225, 0.4056, 0.2080, 0.1995, and 0.1007 as well as 12.49, 16.67, 20.83, 24.19, and 30.15 Pa, respectively. Experimental results indicate that the evaporation rate conforms to the logistic nonlinear model, and the critical pressure is positively correlated with temperature. This paper provides a kinetic data base for PbS vacuum evaporation and also provides a reference for improving the process conditions and production equipment parameters of PbS vacuum distillation. Meanwhile, it improves and develops the theory and practice of vacuum distillation for the preparation of high-purity sulfides and fills the gap of basic kinetic data of nonferrous sulfides.