压力场下纯硅锌矿高温酸转化研究

Acid Conversion of Pure Willemite under High Pressure

传统湿法冶金在处理高硅氧化锌矿时,矿物中硅的溶出容易形成胶状硅,从而增加了矿浆分离的难度,而压力场下高硅锌矿中的酸溶硅可有效转化为易于过滤沉降的二氧化硅沉淀物,从而避免了常规酸浸工艺中硅胶带来的矿浆过滤性能差的问题。本实验采用晶体结构良好且纯度高的纯硅锌矿样进行压力场下的高温酸转化实验研究,考察了各单因素的影响,酸度和粒度的优化有利于改善纯硅锌矿的加压酸浸反应,提高锌的浸出率,提高温度有利于改善矿浆的过滤性能,液固比偏低严重影响锌的浸出率,偏高严重影响矿浆的过滤性能。高温酸性环境中纯硅锌矿的溶解反应非常迅速,在釜内压力1.2 MPa,液固比20∶1,温度393 K,硫酸浓度0.38 mol·L^(-1),平均粒径55μm,搅拌转速600r·min-1,浸出时间16 min的条件下,矿物中锌的浸出率达90%以上,同时通过X射线衍射(XRD)、X射线光电子能谱(XPS)以及扫描电子显微镜-能量散射光谱(SEM-EDS)检测手段,验证了渣相中的硅形成了晶型方英石沉淀,在矿物表面形成了不溶性外壳,从而阻碍了反应的进一步进行,实现了矿物中有价金属的选择性浸出并使硅以沉淀形式截留于浸出渣中。

In the treatment of high silicon zinc oxide ore during traditional hydrometallurgy, mineral dissolution of silicon is easy to form colloidal silicon, which increases the difficulty of separation of pulp; but under pressure, acid soluble silica of silicate zinc ore can be effectively converted into silica precipitation which can separate from liquid phase easily, avoiding the pulp filtering problem of silica gel in the conventional acid leaching process. Pure willemite sample of good crystal structure and high purity was used to proceed a series of experiment researches on acid conversion of pure willemite under pressure and the affecting factors were investigated. It was found that acidity and particle size of optimization could improve the leaching rate of zinc, the increase of temperature was beneficial to the filtration performance of pulp, the low liquid-solid ratio had serious effect on the leaching rate of zinc and the high liquid-solid ratio affected the filtration performance of pulp seriously. The experiment results showed that the acidolysis reaction of pure willemite under high temperature was very rapid. Under the condition of oxygen pressure of 1.2 MPa, liquid-solid ratio of 20： 1, reacting temperature of 393 K, sulfuric acid concentration of 0.38 mol·L^-1 , average particle size of 55 μm, agitation speed of 600 r·min^-1, leaching time of 16 min, the leaching rate of zinc was above 90%. Simultaneously, it was verified that the slag phase formed crystal christobalite pre- cipitation and the insoluble mineral surface shell hindered the further reaction of mineral by the means of X-ray diffraction （XRD） , X- ray photoelectron spectroscopy （XPS） and scanning electron microscope-energy dispersive spectrometer （SEM-EDS）. In this way, the valuable metal was leached selectively and silica was kept in slag phase in the form of christobalite precipitation.