Leaching kinetics of selenium from selenium–tellurium-rich materials in sodium sulfite solutions

The leaching kinetics of selenium from selenium–tellurium-rich materials in sodium sulfite solutions was studied. The morphologies of selenium–tellurium-rich materials are mainly spheroid and columnar bodies and the range of particle size of selenium–tellurium-rich materials is between 17.77 μm and 56.58 μm, which contain 41.73% selenium and 40.96% tellurium. The ranges of experimental elements are 126–315 g/L of sodium sulfite concentration, 100–400 r/min of agitation speed, 23–95 °C of reaction temperature, 7:1–14:1 of liquid–solid ratio and 17.77–56.58 μm of average particle size. The results show that the leaching rate increases with increasing the sodium sulfite concentration, agitation speed, reaction temperature or liquid–solid ratio and the leaching rate decreases with increasing the particle size. The reaction temperature has the significant effects on the selenium leaching rate which increases from 21% to 67% with increasing temperature from 23 °C to 95 °C. The experimental data agree quite well with the Avrami model for leaching, with model parameter of 0.235 and apparent activation energy of 20.847 kJ/mol.