Vanadium containing sludge is a by-product of vanadium pentoxide obtained by hydrometallurgical methods from vanadium slag that can be estimated as a promising technogeneous raw material for vanadium production. The phase analysis of vanadium-containing sludge by the X-ray diffraction method showed that it contains vanadium in spinel form (FeO∙V2O3). The various oxidation roasting methods for sludge treatment were studied for increasing vanadium extraction into the solution. It showed that the most effective additive is 1% CaCO3 at a roasting temperature of 1000 °C. Oxidation roasting of vanadium-containing sludge with the additive led to an increase in the acid-soluble form of V2O5 from 1.5% to 3.7% and a decrease in the content of FeO∙V2O3 from 3% to 0.4%. These results confirm the efficiency of the application of oxidation roasting to convert vanadium compounds into acid-soluble forms. The conversion mechanism of spinel to acid-soluble phases during oxidation roasting with additives was investigated by thermogravimetric analysis and thermodynamic simulation. It showed that the formation of acid-soluble calcium vanadates during oxidation roasting without additives occurs at temperatures above 800 °C while CaCO3 addition allows one to reduce this temperature to 600 °C.

No abstract

A big amount of solid wastes or dump sludges is generated after leaching vanadium (V) from a roasted mixture. As the vanadium content in these tailings is comparable to its concentration in traditional vanadium sources such as titanomagnetite ores or a vanadium converter slag, these wastes could be recycled to extract additional vanadium. Therefore, this research was aimed on studies of vanadium-containing sludges resulting from hydrometallurgical production of vanadium pentoxide to find an optimal technology for V extraction. The material composition of industrial and synthetic sludge samples was studied by X-ray fluorescence analysis (XRF), X-ray diffraction (XRD), secondary ions mass spectroscopy (SIMS), and X-ray photoelectron spectroscopy (XPS, ESCA). The paper demonstrates the presence of vanadium in sludges, not only in spinels in 3+ oxidation degree, but also in other compounds containing V4+ and V5+. It was found that vanadium substitutes a set of elements in minerals except spinel. The dependence between the content of insoluble vanadium compounds and V oxidation degree was determined.

Red mud is a hazardous waste of the alumina industry that contains high amounts of iron, aluminum, titanium and rare-earth elements (REEs). One of the promising methods for the extraction of iron from red mud is carbothermic reduction with the addition of sodium salts. This research focuses on the process of hydrochloric high-pressure acid leaching using 10 to 20% HCl of two samples of non-magnetic tailings obtained by 60 min carbothermic roasting of red mud at 1300 °C and the mixture of 84.6 wt.% of red mud and 15.4 wt.% Na2SO4 at 1150 °C, respectively, with subsequent magnetic separation of metallic iron. The influence of temperature, leaching duration, solid-to-liquid-ratio and acid concentration on the dissolution behavior of Al, Ti, Mg, Ca, Si, Fe, Na, La, Ce, Pr, Nd, Sc, Zr was studied. Based on the investigation of the obtained residues, a mechanism for passing valuable elements into the solution was proposed. It has shown that 90% Al, 91% Sc and above 80% of other REEs can be dissolved under optimal conditions; Ti can be extracted into the solution or the residue depending on the leaching temperature and acid concentration. Based on the research results, novel flowsheets for red mud treatment were developed.

No abstract