Treatment and recycling of goethite waste arising from the idrometallurgy of zinc

Goethite (FeOOH) is an iron-rich toxic waste that arises during the hydrometallurgical process for producing zinc metal. Due to the presence of impurities in the goethite (Zn, Pb, Ni, Cd, Cu, As, etc.) and the large amount produced yearly, the disposal of goethite waste represents a serious environmental problem which is generating social and economic difficulties for zinc companies. The experimental results, presented here, summarize part of the work carried out during the European Union programme 'Raw Materials and Recycling' (Contract MA2R-CT90-0007) aimed at recycling the goethite waste, in combination with raw materials and other industrial residues, to produce glassceramic materials. The chemical and morphological characteristics of goethite, originating from the Sardinia zinc plant, were evaluated and the possibility of recovering valuable elements was tested. In order to obtain a glass with adequate properties, the waste was mixed with sand, tuff, feldspar, limestone, dolomite, pumite and glass cullet in various proportions. Glass-ceramic materials were obtained from the molten glass batch using a controlled cooling treatment, yielding a 75% crystalline phase. In view of the use of glass ceramic as a construction material, the main physical, chemical and mechanical properties were evaluated.