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YflK 628.5:550.4
THE GEOCHEMICAL CHARACTERISTICS OF THE PHOSPHORITE FROM MANKHAN-UUL DEPOSIT, MONGOLIA
A. Minjigmaa, Ts. Zolzaya, G. Oyun-Erdene, D. Enkhtuya*, G. Amgalan, Zh.G. Bazarova**’****, B. Davaabae
Institute of Chemistry and Chemical Technology, Mongolian Academy of Science. Ulaanbaatar
University of Railway, Mongolia **Baikal Institute of Nature Management SB RAS, Russia, Ulan-Ude ***Buryat State University, Russia, Ulan-Ude
Phosphorite ofMankhan-Uul deposit consists of silica type's phosphorite. Mankhan-Uul's phosphorite dominated quartz and hydrogen carbonate phosphate minerals. Toxic elements such as a Pb, As, Ni, Cr, Cd, Co, Sr, Cu, Zn, Mn concentrations were lower than the average world phosphate and Clark of phosphate rock's concentrations. Average concentration of U was 16.35 g/ton in Mankhan-Uul deposit and it was lower than average world phosphate. First time we had determined enrichment factor (EF) of toxic elements in the phosphorite from Mankhan-Uul. The result shows that all toxic elements EF of Mankhan-Uul deposit except Cr were lower than EF of the world average phosphate.
Key words: phosphorite, toxic elements.
Mongolia is one of the countries rich in phosphate reserve and most of reserve is located in the Khuvsgul basin, Northern Mongolia. The Khuvsgul Basin consists of more than 30 deposits such as a Burenkhaan, Suul tolgoi, Jankhai, Ongilog nuur, Uran-Dush, Mankhan-Uul and most studied of them scientists is Burenkhaan deposit [1]. The Khuvsgul Phosphorite Basin was considered to be one of the largest phosphorite-bearing basin in the world, with predicted reserves of more than 4,5 million tons of high and middle quality ores [2] noted that the North Mongolian folding system is an adjacent southern part of east Sayan, Tuva and west Baikal. As for the above mentioned folding systems, Proterozoic metamorphic rock series are very important. The Mankhan-Uul deposit formed from metamorphic series of the early Riphean Darkhad types.
First scientific study of the Mankhan-Uul deposit carried out in 1984-1986 which produce technology for phosphate enrich [3]. We are studying Mankhan-Uul phosphorite deposit for redefine reserve and to identify chemical, geochemical characterization of phosphorite since 2008. Tuguldur noted that the Mankhan-Uul total phosphate (P2O5) ranged from 10 to 14% and its reserve is about 92 million ton, respectively. The Mankhan-Uul deposit silica type of phosphorite dominates. Mean chemical composition of Mankhan-Uul phosphorite were 15.7% P2O5, 69.6% SiO2, 5-15% carbonate etc. [3].
Materials and methods
Phosphorites from Mankhan-Uul deposit, Northern Mongolia were studied. The research were held twice in 2008 and 2009 for collect samples. 200 samples selected from total 1000 phosphorite samples for determine total phosphate concentration and selected samples were undergone by petrographical, chemical and mineralogical analysis. The chemical compositions of samples were determined by X-ray fluorescince (Laboratory of University of Science and Technology) and analytic chemical analysis. The analysis of mineralogical composition were determined by XR diffractometer and IC spectra (State Laboratory of Nature Science, MAS), and radioactive elements were determined by gamma spectra (Nucleur Physical research center, Mongolian National University). The petrographical analyze had done at the main geological laboratory. The study was carried out at the Mankhan-Uul deposit, Northern Mongolia. Mankhan-Uul phosphorite deposit belongs to Alag-Erdene sum, Khuvsgul province and located at a latitude 50o15’ to 50o18’ N and a longitude of 100o7’ to 100o8’E. It located in the east part of Eg river, 20 km far from Khuvsgul lake and 50 km far from Burenkhaan deposit. Mankhan-Uul deposit total area is 25 km2 and wide is 4 km. Average altitude is 1700-1800 m above the sea level.
Results and discussion
1. Petrography-mineralogical study
Phosphorite samples of Mankhan-Uul deposit were analyzed in the Central Geological Laboratory for petrographical and mineral composition analysis. By petrography-mineralogical analysis will be identified mineral structure, configuration and composition of the rock [4]. Mankhan-Uul petrographical description shown in the table 1 and on the pic. 2.
It is clear that (table 1 and 2) in the rock composition dominate phosphate (45-50%), quartz (30-35%) and apatite (10-15%). The petrographical descriptions and thin section photos had done in two phosphorite samples of Mankhan-Uul deposit shown in pic. 2.
Microscopic description: The rock consists of phosphate bearing granules and inside free area developed part of cement for connect other parts. The phosphate matter formed ground and ovel, the rock was shared into different granuls with size from 0.2 to 1.1 mm (pic. 2). Those granuls are usually coincides black color because of concentrated by the collomorph without inside structure and small part of phosphate. Quartz is widely distributed in the rock. The apatite’s granules size were from 0.02 to 0.08 mm. Phosphate agregates are semi-isotrop, color is yellow brown, consists of fine grained and fine dispersed granuls.
Table 1
Petrographical complete description
Sample name Mankhan-Uul deposit
Microscopic description Phosphorite
Structure Breccia
Texture Massive (block)
Grain size 0.2-1.1 ii
Mineral composition of rock
Main grains Next main Secondary Minor %
Quartz 30-35 % Phosphate 45-50 % Apatite - 10-15% ore minerals - rare
Pic. 2. Microscopic photo of phosphorite. Mankhan-Uul deposit
2. Chemical composition of phosphorite Mankhan-Uul deposit
We had chosen 10 phosphorite samples from total 200 samples for determine chemical composition. Main chemical composition of phosphorite shown in table 3.
Table 3.
Mankhan-Uul phosphorite chemical composition (%)
Sample P2O5 CaO MgO S1O2 Fe2O3 AI2O3 CO2 T1O2 F LOI* S
01-15 16.75 20.44 2.2 57.2 0.56 0.44 0.50 0.015 0.80 0.53 98.90
02-09 12.25 13.44 1.4 70.0 0.37 0.32 0.80 0.012 0.72 0.83 99.31
03-10 6.00 8.40 3.60 73.10 3.20 0.95 4.00 0.007 0.31 4.12 99.57
04-12 9.75 11.20 1.00 74.80 1.80 0.56 0.22 0.010 0.52 0.25 99.86
05-06 9.75 10.80 3.4 70.85 2.80 0.80 0.15 0.009 0.41 0.18 98.96
05-13 17.50 21.28 2.20 56.20 0.64 0.75 0.34 0.017 0.87 0.37 99.80
06-16 9.75 10.50 0.80 72.20 3.6 1.37 0.27 0.010 0.43 0.28 98.94
07-18 7.75 8.80 0.20 79.30 1.80 0.90 0.35 0.008 0.31 0.37 99.42
08-09 9.75 11.70 0.80 72.70 2.20 0.85 0.82 0.010 0.37 0.90 99.20
09-28 3.50 56.00 12.50 48.6 7.40 1.80 11.8 0.004 0.15 12.0 98.01
* Loss of Ignition
Table 3 shows that concentration of carbonate negatively correlated with silicate concentration in the phosphorite. Amgalan noted that Mankhan-Uul deposit consists of silicate type of phosphorite. Also our study identified that Mankhan-Uul deposit phosphorite consists of silicate type. The result shows that when iron and aluminum bearing mineral concentration increases in the phosphorite then concentration of silicate decreased due to rock type and mineral composition in the phosphorite. It is clear that the concentration of phosphate (P2O5) positively correlated with the carbonate’s concentration and negatively correlated with silicate concentration (table 2). Concentrations of P2O5 and CaO were positively correlated in the phosphorite, whereas P2O5 and MgO were negatively correlated [1]. It is due to the depence on F’s concentration in the phosphorite.
Usually, if phosphate concentration ranges from 28.7% to 39.5% in the phosphorite then concentration of the F ranges from 1.86% to 3.12% [1]. In our study, F ranges from 0.15% to 0.87% in the Mankhan-Uul deposit phosphorite and phosphate concentration ranges from 9.75% to 17.5%. Therefore by Amgalan’s phosphorite classification the Mankhan-Uul phosphorite belongs to the poor phosphorite. Concentrations of Mg, Ca and F from Mankhan-Uul’s phosphorite were lower than that of the other deposits such as a Burenkhaan, Aldarkhaan, Tsakhir-Uul etc. [1]. Usually, carbonate type of phosphate such as an apatite and fluorapatite had high amount of fluorine and carbonate.
3. IC spectra and XRD analysis of phosphorite from Mankhan-Uul deposit
Infra red spectra of the phosphate ore (pic. 3) indicates that the bands 573, 609, 870, 960, 1044 and 1625 cm-1 refer to phosphate radical which constitute the spectrum of the main component of the which is an good agreement with the published IR spectra of apatite. In our study, phosphate radicals indicated in the bands from 576 to 603 and 1043, 1078 cm-1. Carbonate radicals observed in the bands 1400 cm-1 in the Mankhan-Uul deposit phosphorite. The bands at 1429 and 1450 cm-1 is carbonate radical which indicate the presence of carbonate minerals as gangue minerals. Bands 3600 and 1600 cm-1 are vibrational bands of the hydroxyl group. Frequencies at 1093 and 462 cm-1 refers to Si-O streching band which is attributed to quartz mineral.
Pic. 3, 4. XRD pattern of phosphorite and FTIR spectra of phosphorite
Pic. 4 shows the XRD pattern of phosphorite from the X-ray analysis identified that Mankhan-Uul deposit phosphorite consists of quartz, calcite, dolomite and apatite, tricalcium phosphate (Q-SiO2; Ap-Cas(PO4)3F; C- CaCO3; D- CaMg(CO3^; T- Ca3(PO^; Fp-Ca*H2(PO4)6-H2O-NaHCO3H20). Main minerals were quartz and hydrogen carbonate phosphate in the phosphate rock. The quartz mineral represent the main component, which is chracterized by diffraction lines 26.5, 20.9 and 50.1 Â. The reflection of hydrogen carbonate phosphate appearing at 2a = 25.9, 32, 33.1 and 34.2 Â. It is clear that Mankhan-Uul deposit consists of silica type of phosphorite.
4. Toxic elements
The phosphorite is main resourse of the fertilizer. Therefore, it’s important to determine concentrations of toxic elements in the phosphorite to give their ecological evaluation. Toxic elements concentration have determined in 20 selected phosphorite samples from Mankhan-Uul deposit. Average concentration of each toxic elements concentration had put in table 3. We compared Mankhan-Uul phosphate toxic elements concentration with the average world phosphate [5] and clark of the phosphate rock [6] to give ecological evaluation.
The Mankhan-Uul phosphorite toxic elements concentrations were lower than the average world phosphate and Clark of phosphate rock’s concentrations (table 3). Especially Ni, Cd, Zn’s concentrations were in very small amounts in the Mankhan-Uul phosphorite. Concentration of Cr was similarly with Clark of the phosphate rock. The results shows that Mankhan-Uul phosphorite is ecologically non toxic for raw material of any fertilizer industry.
Table 3.
Toxic elements concentration in the Mankhan-Uul phosphorite (g/tn)
Deposit Pb As Ni Cr Cd Co Sr Cu Zn Mn
Mankhan-Uul 8.3 10 5.65 110 0.65 5.7 36 24 16 130
AWP* 50 23 53 125 18 - - 75 195 -
CPR** 12 13 37 109 11,0 - - 23 204 -
--------3!--------------------------------------------3ÖS----------------------------------------
AWP - Average World Phosphate [5], CPR - Clark of the Phosphate rock [6].
Table 4.
Concentcentration of radio-active element of phosphate from Mankhan-Uul deposit
Deposit Radio active elements U, (g/ton) Th, (g/ton) Ê40, EK/kg
Mankhan-Uul 16.35 0.68 0.65
AWP* 120 - 377
CPR** 20 - -
--------3!--------------------------------------------3ÖS----------------------------------------
AWP - Average World Phosphate [5], CPR -Clark of the Phosphate rock [6].
Concentrations of phosphate radio-active elements were lower than the average world phosphate and Clark of phosphate rock’s concentrations (table 4). In the Mankhan-Uul deposit uranium average concentration was 16.35 g/ton. Concentration of uranium in the phosphate rock depends on phosphate type, concentration of the F and P2O5 [4]. The uranium concentration ranges from 0.0001 to 0.0027% in Mongolian phosphate deposits. The concentrations were in the Burenkhaan - 0.0027%, in Alagiin Davaa, Tsakhir-Uul - 0.0001% and in Mankhan-Uul - 0.0001% [7]. It is clear that Mongolian phosphate rock average uranium concentration was lower than the world average uranium concentration (0.005%).
We calculated enrichment factor of the phosphate from Mankhan-Uul deposit which gives its ecological evaluation. All rocks, sediment, and soils are normalized to same background based on a known criterion (e.g. Al concentrations) [8]. Concentration of the Al in the crust is very stable. The Enrichment factor method was used to investigate the statistical similarities between Mankhan-Uul and worldwide deposits. The enrichment factor (EF) was calculated using of following equation;
EF = (CX/CN) Study / (CX/CN)Crustal (1)
(CX)Study - concentration of element in studied samples. (CX)Study - concentration of Al in the studied samples. (CX) CrUstal- concentration of element in crustal rocks. (CN)Study- concentration of Al in the average crustal rocks [5].
Enrichment factor results of the studied deposit compared with other deposits
CU Pb Ni Zn Cr Cd U
AWP 1 1 1 1 1 1 1
MP 0.4 0.19 0.68 1.85 2.5 0.22 0.94
USP 0.79 0.62 1.78 2.7 2.25 1.52 0.88
JP 0.53 0.024 0.73 0.69 0.64 0.44 1.58
MUP 0.74 0.36 0.24 0.18 1.9 0.077 0.3
AWP - World Average Phosphate; MP - Morocco phosphate; USP - USA phosphate; JP ■ - Jordan Phosphate; MUP -
Mankhan-Uul Phosphate;
3
Cu Pb Ni Zn Cr Cd U
Pic. 5. EF relative ratio of Average World Phosphate with different deposits
Each toxic element of EF shown by table 5 and pic. 5. We had used equation 1 to calculate each toxic element of EF of the Mankhan-Uul deposit. The result shows that all toxic elements EF of Mankhan-Uul deposit except Cr were lower than EF of the world average phosphate. The present study indicates that Mankhan-Uul phosphate has a higher enrichment of Cr than the average world phosphates (AWP) and whereas lower enrichments of Zn, Cd, Pb, U were found in Mankhan-Uul deposit. All toxic elements of Morocco and Mankhan-Uul deposits EF were quite similary except Zn and it shows its similarity in geochemical characteristics.
Conclusions
• Mankhan-Uul deposit phosphorite consists of silicate type of phosphorite. Concentration of the SiO2 ranges from 48.6 to 79.3 in the studied phosphorite samples, whereas lower concentrations of CaO and F were found in the Mankhan-Uul deposit.
• IC spectra analyze identified that apatite, carbonate, hydroxyl group and quartz radicals in the phosphorite from Mankhan-Uul deposit. In Mankhan-Uul phosphorite quartz and hydrogen carbonate phosphate minerals are dominated.
• Toxic elements of the Mankhan-Uul phosphorite such as a Pb, As, Ni, Cr, Cd, Co, Sr, Cu, Zn, Mn concentrations were lower than the average world phosphate and Clark of phosphate rock concentrations. Average concentration of U was 16.35 g/ton in Mankhan-Uul deposit and it was lower than average world phosphate.
• First time we had determined enrichment factor (EF) of toxic elements in the phosphorite from Mankhan-Uul. The result shows that all toxic elements EF of Mankhan-Uul deposit except Cr were lower than EF of the world average phosphate.
• The result shows that Mankhan-Uul phosphorite is ecologically non toxic for raw material of any fertilizer industry.
REFERENCES
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2. Kaljuvee T., Kuusik R. and Veiderma M. // Intern. jour. of Mineral Processing. - 1995. - V.43. - P. 113.
3. Tuguldur M., Gereltuya S., Chuluunbaatar G. Technology for enrich of silica type of phosphorite from Mankhan-Uul deposit // Mongolian and Russian joined scientific project. - Ulaanbaatar, 1985.
4. Amgalan J. Agrochemistry of microelements // Munkhiin useg press. - Ulaanbaatar, 1999.
5. Rudnick R.L. and Gao S. Composition of continental crust // Treatise on Geochemistry. - Elsevier. -Netherlands. - 2004.
6. Kauwenbergh, van S.J. Cadmium and other minor elements in world resources of phosphate rocks // 4 fertilizer society. - York, UK, 1997.
7. Minjigmaa A., Zolzaya Ts., Oyun-Erdene G., Bayaraa D. The geochemical characterization of Mongolian main phosphate deposits and its ecological evaluation // Annual scientific report of National University of Pedagogy. - 2009. (in press).
8. Batarseh M., El-Hasan T. Toxic element levels in the Phosphate Deposits of Central Jordan // Soil & Sediment Contamination. - 2009. - V.18. - P. 205-215.
9. Jiries A., El-Hasan T., Al-Hiwati M. and Seiler K.P. Evaluation of the effluent water quality produced from phosphate mines in central Jordan // Mine Water Envirom. - 2004. - V.23, №3. - P. 133-137.
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YflK 65.011.1:622.012
DISSOLUTION OF URANIUM FROM PHOSPHORITE BY DIFFERENT SOLUTIONS
A. Minjigmaa, G. Oyun-Erdene, D. Enkhtuya*, G. Amgalan, Zh.G. Bazarova**^**, B. Darkhijav
Institute of Chemistry and Chemical Technology, Mongolian Academy of Science, Ulaanbaatar University of Railway, Mongolia, Ulaanbaatar **Baikal Institute of Nature Management SB RAS, Ulan-Ude Buryat State University, Ulan-Ude
The world average uranium content in phosphate rock is estimated at 50-120 g/tn. The U concentration ranges 10-27 g/tn in Mongolian phosphate deposits. The aim of this study is to improve quality of the activated phosphorus fertilizer. We decreased uranium concentration from 12g/tn till 3.9 g/tn in the milled phosphate raw by carbonate and citric acid solutions. This work demonstrated that sodium carbonate/bicarbonate uranium leaching process is selective and effective to extract 67,5% of uranium from Burenkhaan phosphate rock.
Key words: uranium, phosphate.
The phosphate is main source of fertilizer and about 95% of the world total phosphate rock production used in agriculture as fertilizers, pesticides and animal feeds. Phosphate rock used for fertilizer contain trace amounts of radioactive elements such as a uranium, K40 and thorium. The world average uranium content in phosphate rock is estimated at 50-200 ppm or 0.005-0.020%. Phosphate rock containing up to 120 ppm uranium have been used as a source of uranium fuel. Few data exists on uranium accumulation in soils and uranium plant uptake from phosphate fertilization [1]. No increase in soil and plant uranium was detected in a long term experiment with triple superphosphate fertilization [2]. However, as these authors stated, considering the mobility of U6+ (uranyl ion), it is hardly surprising that no uranium accumulation was found in soil, rather, these results imply that uranium applied with the phosphate fertilizer had leached into the ground water that drained from the fields. Increased uranium concentrations in surface and ground water and water from drainage channels after long term mineral fertilization have been reported [3-5].
Marine phosphorite deposits contain averages of 6-120 ppm, and organic phosphorite deposits up to 600 ppm [6] phosphate rock of sedimentary-type contains an appreciable amount of uranium in the range of 0.005-0.03% U3O8 in isomorphous substitution for Ca [7-8]. The phosphate rock deposits of USA, North Africa, Israel, Jordan and Morocco etc., contain an average U content of 0.01-0.02% U3O8 [9]. The uranium concentration ranges from 0.0001 to 0.0027% in Mongolian phosphate deposits. The concentrations were in the Burenkhaan - 0.0027%, in Alagiin Davaa, Tsakhir-Uul - 0.0001% and in Mankhan-Uul - 0.0001% [10]. It is clear that Mongolian phosphate rock average uranium concentration was lower than the world average
