MECHANISM AND KINETIC CONTROL OF THE OXYPRECIPITATION OF SULFURIC LIQUORS FROM STEEL PICKLING

Steel pickling liquors are one of the main environmental problems of s teel making. Currently, there are several processes for the treatment of sulphuric liquors, although most recover only acid and haematite (a lpha-Fe2O3). We propose an oxyprecipitation process for this recovery, allowing several kinds of iron oxide or oxyhydroxide to be obtained. The aim of this paper is to determine the kinetic control and reaction mechanism. The influence of different variables is evaluated and two experimental ranges for the synthesis of goethite (alpha-FeOOH) and ma gnetite (Fe3O4) are defined. A systematic study is carried out in thes e experimental intervals, and the results are analysed in order to det ermine the reaction order and the type of kinetic control. Finally, fr om these data, morphological and crystallinity studies and new experim ents, the reaction mechanism is proposed. (C) 1997 Elsevier Science S. A.