![]() | Only 14 pages are availabe for public view |
Abstract The sample under study was collected from Gabal El-Faliq which lies in the South Eastern Desert, Egypt. It was considered mainly as pegmatite mineralization. This sample was firstly subjected to physical upgrading then chemical treatment. Gabal El-Faliq area is considered as one of the promising occurrences for Zr beside the associated economic metal values e.g. REEs, Nb, Ti,….etc. The main target of the present work is the studying of the mineralogical and chemical specification of G. El-Faliq concentrate sample as well as studying the suitable processing method for this concentrate sample to recover Zr, Nb and REEs which have several economic, technological and nuclear applications. For this purpose, a technological representative concentrate sample from G. El-Faliq area was properly prepared. The chemical analysis of this concentrate sample proved the presence of 33.6%w/w ZrO2, 2% w/w Nb2O5 and 4.8% w/w RE2O3 as the elements of interest. The mineralogical analysis of this sample using XRD technique emphasized that, it consists mainly of zircon (ZrSiO4) associated with fergusonite [(Y,Er)(Nb,Ta,Ti)O4, Xenotime (Y,Er)PO4 and Samarskite (Y,Er)(Nb,Ta)2O6. Two different and subsequent leaching techniques were performed to conduct the optimum conditions that realize the highest dissolution efficiencies for all the metals of interest. KOH fusion followed by distilled H2O leaching technique was applied upon the concentrate sample for selective dissolution of Nb dissolution efficiency 97.9% away from Zr and REEs as Nb form soluble potassium niobates while Zr and REEs form insoluble hydrous oxides. The applied optimum leaching conditions were concentrate sample/KOH mass ratio of 1/2, 2.5h fusion time at 550oC fusion temperature. On the other hand, HCl acid leaching was applied upon the concentrate residue after the alkaline fusion. The optimum acidic leaching conditions were 25% HCl acid concentration, S/L ratio of 1/3 with stirring time for 0.5 h at leaching temperature of 80oC for dissolving 99.9% of Zr and 99.7% of REEs. Two different leach liquors were prepared to perform the suitable extraction technique for the recovery of the metals of interest. These leach liquors were alkaline solution for the recovery of Nb and chloride leach liquor for Zr and REEs. Firstly, prepared alkaline leach liquor was obtained by processing 200 g of the present concentrate sample and assays 1.36 g/L of Nb, 0.03 g/L of Ta, 0.25 g/L of Fe, 11.76 g/L of Si and its pH value higher than 12. Due to the high contents of SiO2 in the prepared alkaline leach liquor, it was first treated with conc. H2SO4 for adjusting the pH value of the leach liquor to pH value 10 as almost SiO2 was precipitated as SiO2 gel with small amounts of Nb (0.95%). After separation and washing the precipitate of SiO2 gel, the filtrate contains Nb and the remains of SiO2 was subjected for further acidification to hydrolyze and precipitate of Nb. Almost complete precipitation of Nb (99.8%) was attained at pH 8.5, while its purity was low and only 55.3 % with the interfering impurities of Si, Fe, K, Y. So, further purification was needed using solvent extraction aliquat 336S in xylene. The optimum conditions 5% Aliquat 336S concentration, pH 3.5, contact time 10 min and Aqueous /Organic ratio 1:1. Co-extraction of both of Nb and Fe with their maximum extraction efficiencies 97.9 and 93.8% respectively was concluded so, 0.7M H2SO4 acid concentration was first applied for the selective stripping of almost parts of Fe (90.3%) from the loaded organic solvent with minimal amount of Nb (only 8.2%) at contact time 5 min and A/O ratio 1/1. This was followed by stripping of Nb by using aqueous solution of HNO3. The maximum value of stripping of Nb (99.1%) was reached by applying the optimum conditions 0.8 M HNO3 acid concentration, 6 min contact time and A/O ratio 1:1. The strip nitrate solution rich in Nb was treated with NH4OH solution where Nb was completely precipitated at pH 7.5. After filtration and washing, the obtained Nb hydroxide cake was ignited at 650oC for 1h and identified using XRD analysis. Secondary, with respect to Zr and REEs recovery from the prepared chloride leach liquor containing 28.5 g/L of Zr, 5.4 g/L of REEs, 4.2 g/L of Si and has a pH lower than 1. Direct precipitation technique was used for the extraction of both Zr and REEs. selective precipitation of Zr with 99.9% precipitation efficiency was obtained after adjusting the pH value of the prepared alkali leach liquor via 10% Na2S to be 3 for 25 min at 80oC. The resulted zirconium sulfide which was filtered, washed and dryness was ignited at 850oC for 2h and identified using SEM-EDX analysis. The effluent solution free from Zr was subjected to REEs recovery via their precipitation as RE2(C2O4)3 by using 10% H2C2O4. Almost complete precipitation of REEs was attained at pH 1.1 and after stirring for 45 min. with precipitation efficiency reached 99.8% Finally, flow sheet for processing of G. El-Faliq concentrate pegmatite was designed for the recovery of Zr, Nb beside REEs Fig (38). |