Evaluation of Scabiosa ochroleuca L. vitality after introduction on post-flotation wastes

The aim of this study was to evaluate the Scabiosa ochroleuca suitability for growth on heavy metals contaminated substrate obtained as a result of Zn–Pb ores exploitation and their processing. Three variants of cultivation were tested in vegetative hall conditions: post-flotation wastes (control), wastes enriched with either mineral fertilisation or with sewage sludge. The possibility of future direct use of the studied species on post-flotation settling pond was determined on the basis of biometric measurements and analysis efficiency of photosynthetic apparatus, that is, pigments content and chlorophyll a fluorescence. The results showed that untreated wastes negatively influenced on plants morphological and physiological status. On the contrary, the application of sewage sludge improved growth and development of cream scabious. Thus, not only the selection of proper plant material, tolerant to toxic levels of heavy metals and other hostile conditions, but also the waste treatment are crucial when metalliferous areas are to be reclaimed.

Column Bioleaching of Refractory Gold Ores

Refractory sulfide ores are ubiquitous resources of gold around the world. It was demonstrated that biooxidation pretreatment of refractory whole ores could be conducted in heaps. The effectiveness of column biooxidation of off-balance gold ores from Bakyrchik and Bolshevik deposits (northeast Kazakhstan) containing pyrite and arsenopyrite was examined in the laboratory. Bakyrchick ore contained 1.5% of pyrite, 3% of arsenopyrite and 4.5 g/t of gold. Bolshevik ore contained 1% of pyrite, 1% of arsenopyrite and 10.7 g/t of gold. The recovery rates of gold from the Bakyrchik and Bolshevik ores by direct cyanidation were 4.5% and 8.2%, respectively. Representative samples of each ore were processed in air-lift percolators. A bioleaching experiment was performed in duplicate. The enrichment culture was obtained from the pyrite flotation wastes and used as an inoculum. Bioleaching was conducted for 60 days at ambient temperature (20-25°C). The recovery rates of gold from the bioleaching residues of Bakyrchik and Bolshevik ores by cyanidation were 21.0% and 48.5%, respectively. The results obtained in the present work may be used to estimate perspectives of heap bio-oxidation for the recovery of gold from these sulfide ores.