| Zinc, which is known as the modern industrial protective agent, is an indispensable strategic metal to the healthy development of national economy and is one of the current largest amounts of non-ferrous metallurgical products. The development and utilization of zinc oxide resource has paid much attention with the dipletion of zinc sulfide ores. The new flowsheet on pretreatment of low grade zinc oxide ore by hydrothermal sulphidation and further flotation of the suphidised products will obtain a better parameter. At the basis of our previous technology study, the present paper mainly focused on the theory foundation of hydrothermal sulphidation of low grade zinc oxide ore. Listed below are the main results:(1) The carbonate-hosted zinc oxide ore and silicate-hosted zinc oxide ore form Lanping of Yunnan was analyzed by modern analysis methods. The main zinc ore minerals are smithsonite and sphalerite, and gangue minerals include quartz, calcite. etc. Smithsonite, sphalerite and gangue minerals usually exist in complex relationships. Hemimorphite and zinc silicate in silicate-hosted zinc oxide ore are irregular embeding of hemimorphiteq with quarz will cause it more difficult to enrich by flotation.(2)Hydrothermal sulphidation of low grade zinc oxide ore with elemental sulfur was thermodynamically analysed. The potential-pH diagrams for sulfur water were plotted at experimental temperautre. The stablity regions S2-,H2S,and HS-moved to lower pH values with rising temperature. According to the thermodynamic analysis results smithsonite, hemimorphite, zinc silicate and zinc oxide can easily be conversed to zinc sulphide at experimental temperature.(3) The kinetics of hydrothermal sulphidation of hemimorphite and smithsonite with elemental sufur were studied respectively. Sulphidation of hemimorphite was controlled by the chemical reaction during the early stage of reaction with activation energy of50.23kJ/mol, and then was controlled by solid product layer diffusion with activation energy of11.12kJ/mol. Sulphidation product was detected by XRD and the result shows that it would be helpful for conversion of hemimorphite to zinc sulfide with an increase of temperature. Sulphidation of smithsonite was controlled by solid product layer diffusion with activation energy of14.67kJ/mol. hydrothermal sulphidation of smithsonite almost completed at200℃for120min.(4) Experiments of hydrothermal sulphidation of carbonate-hosted zinc oxide ore by technology of presulphidation-flotation were carried out. Sulphidation rate of zinc and lead were over73%and86%nder the optimized technical parameters of pulp initial pH=9, particle size57-74μm, sulfur mole raito2.0, temperature180℃.240min and stirring speed of500rpm. Sulphidation products were dressed by mixed flotation flowsheet, which gave much higher recoveries of69%lead and81%zinc. A flotation concentrate was obtained with35%Zn and19%Pb from the material which was treated by sulfidation.(5) Experiments of hydrothermal sulphidation of silicate-hosted zinc oxide ore by technologies of presulphidation-flotation were carried out. Sulphidation rate of zinc and lead were over55%and83%under the optimized technical parameters of pulp initial pH=9, particle size57-74μm, sulfur mole raito2.5, temperature180℃,240min and stirring speed of600rpm. During the sulphidation procees most of the hemimorphite was conversed to zinc sulfide, while gangue minerals such as quartz and calcite were still in their original forms, and the diffferent surface property between useful minerals and gangues would be advantage for further flotation. Sulphidation products were dressed by mixed flotation flowsheet, which gave much higher recoveries of73%lead and83%zinc. A flotation concentrate was obtained with34%Zn and15%Pb from the material which was treated by sulfidation.
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