Enhanced conversion mechanism of Al-goethite in gibbsitic bauxite under reductive Bayer digestion process

还原拜尔法溶出三水铝石矿中铝针铁矿的强化转化机理

The conversion mechanism of Al-goethite under the action of different additives(lime or reductant for typical or reductive Bayer digestion)was investigated by thermodynamic calculation,XRD,and SEM-EDS.The results show that the formation of Fe-substituted hydrocalumite is crucial to converting Al-goethite to hematite during Bayer digestion by adding lime.However,the conversion proceeds more easily under the action of reductant due to the rapid formation of magnetite.Additionally,Bayer liquor composition significantly affects the product composition and also the conversion rate of Al-goethite.Compared to typical Bayer digestion with Al-goethite containing gibbsitic bauxite as raw material,the red mud yield of reductive Bayer digestion decreases from 39.02%to 31.19%,and the grade of TFe in red mud increases from 41.66%to 53.80%.

通过热力学计算、XRD与SEM-EDS研究不同添加剂(石灰/还原剂分别对应典型/还原拜耳法溶出)作用下铝针铁矿的转化机理。结果表明,形成含铁水铝钙石相是石灰促进这一转化的主要机制;而在还原剂作用下,由于磁铁矿的生成,铝针铁矿的转化更易发生。此外,拜耳溶液成分显著影响针铁矿转化过程产物组成和转化速率。与以含铝针铁矿的三水铝石为原料的典型拜耳法溶出相比,还原拜耳溶出赤泥的产出率由39.02%降低至31.19%,总铁含量(TFe)由41.66%提高至53.80%。