rare earth elements

Sineqan mine, 25 km away from Delijan city (Markazi province), has shown important evidences of iron oxide ores containing copper, gold and rare earth elements (REE) in the early stages of exploration. In the present study, a low-grade sample of the mine from the albite zone containing 0.69% of copper and 223, 186 and 55 g/t of cerium, lanthanum and neodymium was processed and compared with the results of elements correlation in geochemical samples. Cerium, neodymium and lanthanum showed the highest correlation with each other and with the thorium. The correlation coefficient of light REEs with phosphorus was negative. The results of ammonium sulfate leaching showed that the occurrence of REE in the sample is not as adsorption on clay minerals and the study of the correlation coefficient of REE with aluminum and sodium in geochemical samples also confirmed this result. The results of leaching with H2SO4 showed that selective leaching of copper is possible. The low efficiency of leaching with H2SO4, HCl and HNO3 and the higher efficiency of 96% for leaching with cerium and lanthanum under acidic baking conditions showed that a significant part of REEs is in the form of refractory minerals. The concentration ratio of REEs in the magnetic concentrate was close to iron. According to the correlation analysis of elements in geochemical samples, the correlation of calcium with REE was in the range of -0.2to-0.3. In the flotation test, although the grade of calcium increased 3.5 times in the flotation concentrate, this was not the case for REEs. The results of this research can be used in similar cases in the early stages of exploration and processing feasibility studies.

Rare earth elements are generally separated from the leaching solution by concentration as a by-product of the processing plants. Among the main problems of their separation and extraction is the low level of them in the leaching stage. This study aimed to recover available rare earth elements from leaching solution of the non-magnetic sample of the Gazestan iron ore. The solution under investigation contained low concentrations of the rare elements cerium, lanthanum, neodymium, and yttrium, along with significant impurities including ferric ions, calcium, and phosphorus. Therefore, the removal of impurities, especially iron, were investigated. In this regard, it was tried to precipitate rare earth elements as fractional. The two main methods examined, 1) fractional precipitation of rare elements, iron and phosphate, and 2) precipitation of rare elements and calcium while increasing the solution temperature and remaining iron in the solution. Finally, the results of the two methods showed that rare earth elements were concentrated effectively. The REEs concentrated around two to three times higher than their initial level in the concentration step. After that, the adsorption experiments were performed on a batch scale by the Dowex50 WX4 cationic resin. Some experiments were also considered to investigate the effect of temperature enhancement on the adsorption of REEs on resin from the concentrated solution. As the temperature increased, the adsorption of the REEs from the solution increased significantly. In this case, the removal of iron was around 98%. The maximum adsorption of cerium, lanthanum, neodymium, and yttrium on the resin was, 99.11%, 98.67%, 99.0%, and 97.27%, respectively.

The Esfordi phosphate concentrate with total assay of REE equal to 1.2 percent is one of the richest source of rare earth elements in Iran. It contains Ce(5608 ppm), La(1959ppm) and Nd(2227ppm). In this research, the effect of mechanical activation on the leaching of rare earth elements by nitric acid from Esfordi phosphate concentrate was investigated. For the investigation of mechanical activation effect on leaching of REE, a planetary ball mill was used with steel balls of diameter about 20 mm, ball to powder ratio of 15 and 2 and with a retention time of 90 minuts in dry situation and air atmosphere. Because of high and low leachability of fluorapatite and REE minerals by nitric acid, respectively, tow stage leaching methode was used. The first leaching stage residue, that contained about 99 % of REEs in initial phosphate concentrate, was activated mechanically at ball to powder ratio of 12 and then leached. Results showed that the mechanical activation had important influence on leaching of REE by nitric acid from phosphate concentrate and improved the leaching of Ce, La and Nd from about 1% (without mechanical activation) to 35.79, 42.61 and 30.34% , respectively. The amorphization degree increased to 1.2 and 57% after 90 min intensive milling with ball to powder ratio of 2 and 15 to 1, respectively. Also, the crystallite size and microstrain of Fluorapatite differed from 225 nm and 0.08 % for initial sample to 225 nm and 0.09 % and 81.8 nm and 0.63 % for mechanically activated samples with ball to powder ratio of 2 and 15 to 1 respectively.

Summary : Principal Component Analysis (PCA) and Catchment Basin Analysis (CBA) methods have important role in investigation of stream sediment geochemical data and can have special contribution in prospecting programs and other exploration steps. In this study, the data of 843 stream sediment samples from Khoy 1:100,000 geological sheet area in West Azerbaijan, were investigated using PCA and CBA methods. At first, dimension of variables such as REEs as well as Cu, Pb, Zn, Cr, Au and Ag was decreased using principal component analysis (PCA) and the main principal components were selected for further investigation and finally the correlation of each parameter with achieved factors were given. Then, the background values were calculated and local anomalies were separated using catchment basin analysis on the basis of real area and upstream geological units of catchment. In addition, it is demonstrated that catchment basin analysis is able to better discriminate local anomalies. Consequently two mentioned methods obviously can validate each other.Briefly, in this research, the rare earth and other strategic elements in stream sediments samples of the Khoy 1:100,000 geological sheet area, have been investigated. The background values were calculated and local anomalies were separated using catchment basin analysis on the basis of real area and upstream geological units of catchment. Threshold level method was used for separation of anomalies from background. Also, by principal component analysis (PCA) method, the main factors were delineated. Results obtained from PCA method, were estimated using ordinary kriging and finally these two methods were compared. Consequently two mentioned methods obviously can validate each other.

Aggregation of elements in stream sediments depends on the stream network, area and topography slope of catchment and upstream lithological units. Investigation of these sediments using catchment basin analysis and principal component analysis methods, obviously introduces elements dispersion and prevents demonstrating unreal anomalies. The PCA method is useful in identification of complicated structure, indexing and reduction of data dimension. Because of existence of vast alluvial plains, alluvial fans, coasts and vast basins in Iran, geochemical data analysis by CBA method can lead us to explore the valuable mineral resources to reach sustainable development. The above mention methods will cause to find probable mineralization regions.
Methodology and Approaches : In this study, for investigation of stream sediments geochemical anomalies, different steps such as data processing, separation of basins, calculation of local anomaly using CBA and PCA methods have been used for REEs and some other trace elements. In CBA method, the basins were separated by ArcGIS software and Archydro tools extension and then, real area of geological units for all catchments were calculated. Finally, using real area and application of upstream lithologies in given equations, the background values were calculated and local anomalies were separated. In PCA method, the main component of each elements were delineated, using ordinary kriging, values of each main factors have been estimated in unsampled regions.
Results and Results and geochemical maps obtained by BCA and PCA methods demonstrate that catchment basin analysis is able to better discriminate local anomalies and these anomalies have been correlated with the ordinary kriging maps obtained from principal component analysis and these two mentioned methods, obviously can validate each other.