Lignosulphonates in zinc pressure leaching: Decomposition behaviour and effect of lignosulphonates’ characteristics on leaching performance

Lignosulphonate (LS) is the most commonly used surfactant in zinc pressure leaching (ZPL). In this work, the performance of LS obtained from several producers in ZPL was comparatively studied, the differences in LS characteristics were evaluated in terms of composition, structure, surface tension, etc., and the decomposition behaviour of a typical LS in ZPL was investigated. The results indicated that the leaching performances of these LS varied and depended on the LS characteristics, purity and molecular weight in particular; the differences in the LS characteristics were distinct, and the LS surface activity was the fundamental reason for their diverse leaching performances; softwood and hardwood LS showed superior performances, and three main steps could be concluded for LS decomposition: LS→aromatic compounds (guaiacol, vanillin, vanillic acid, apocynin, etc.)→low molecular organics (short chain ketone, acids, etc.)→CO2+H2O. The results will help the selection and development of LS dedicated to ZPL, and further promote the efficiency, clean, and stability of zinc production.