Extraction of Lanthanides and Antimony from Industrial Residues
Research output: Thesis › Doctoral Thesis
Increasing demand for raw materials, uncertainties in the supply chain due to market policy issues or ecopolitical decisions of producing countries and insufficient diversification in supply of consuming countries led to supply bottle-necks and a highly volatile market situation of technological metals, including rare earths, antimony and cobalt, which the focus is on in this thesis. Although secondary production or recycling is not able to meet an increasing demand, it provides an opportunity for basic supply and independence from primary markets. Furthermore, the content of valuable metals in such materials is often considerably larger than the ore grade which enables the saving of energy in winning. Despite these developments recycling is often limited because of lack of cost fficient and easy manageable processes. The thesis´ focus is therefore on the development and evaluation of process routes and technologies to enable an efficient recovery of technological metals e.g. the recycling of spent polishing material from the glass industry. Besides, the focus was set on the processing of novel process scrap containing antimony, cobalt and rare earths. Moreover, a method for the recovery of RE from waste luminescent material was investigated. Beside limited technological approaches for recycling, these materials suffer from a high grade of dissipation, making secondary production uneconomic at the moment. Nonetheless, since the situation may change in the future, the investigations contribute to a greater range of recycling opportunities. Two methods based on sulfuric and hydrochloric acid for the secondary production of a mixed cerium lanthanum oxide from waste abrasive materials were investigated. Sulfuric acid digestion was found to have the advantage of higher extraction rates, especially for lanthanum. Therefore, the reaction temperature has to be maintained between 150 and 200 °C. Oxalate precipitation was found to be suitable to obtain products of high purity, hence for the reuse in the production of polishing agents. Alternative precipitation methods such as double sulfate precipitation and subsequent transformation to RE carbonates also led to good results regarding yields and product quality. Vacuum distillation and subsequent hydrometallurgical treatment of the distillation residue fit for the secondary production of marketable antimony. Furthermore, leaching of the residue enabled the selective dissolution of cobalt and rare earths, while non-volatilized antimony remains in the residue andundergoes oxidation during acid treatment. Pressure leaching of waste luminescent material is the last field of investigation presented in this thesis. It is shown that dissolution of Y and Eu in hydrochloric acid solution is possible to a high extent according to research found in literature, but using different leaching agents. Furthermore, the extraction of gadolinium, terbium, cerium and lanthanum was investigated simultaneously, whereas the dissolution strongly depended on the chemical stability of the phosphor compound but exceeded leaching rates achieved at atmospheric pressure many times.
|Translated title of the contribution||Extraktion von Lanthaniden und Antimon aus Industriellen Rückständen|
|Publication status||Published - 2014|