New approache to phosphate ore beneficiation coupling chemistry and hydrodynamic of flotation process

Igneous deposits represent the major phosphate ore reserves in South Africa, Brazil and Russia. The Kola province in Russia, where phosphorus is recovered, consists of carbonatites, alkaline silicate and ultramafic rocks. The Kovdor baddeleyite-apatite-magnetite deposit is one of the most studied and exploited deposits in carbonatite-bearing complexes of the Kola province. A large proportion of various associated silicate gangue present in the phosphate igneous ores in addition to the manifested diversity of phosphate minerals, provides challenges to the flotation processes, which is also often complicated by the presence of the calcareous (calcite, dolomite) and naturally-floatable clays minerals. This work presents new reagent blends and flow sheets tested on different ore and tailings samples with various mineral composition, P2O5 grades and size distribution. The experimental researches were performed at laboratory and pilot scale on the three low grade and low contrast ore samples from Kovdor deposit (The Kola Peninsula, North Russia) with P2O5 content of 3.9-13.7%. In addition, a sample of fine fraction of old tailings (D90 below 40 µm, 9% of P2O5, 14.4% CO2, CaO/P2O5=2.9) was also tested. A detailed mineralogical study using advanced XRD, electron microscopy and spectroscopy (IR and Raman) techniques reveled that the phosphate minerals in samples were presented by fluorapatite with francolite and crandallite of weathered zones. Other minerals include calcite, dolomite, magnetite, forsterite, micas (vermiculite, biotite, phlogopite, clinochlore) and silicates (microcline, cordierite, clinochrysotile). Despite of similarity of physico-chemical properties of Ca-minerals and auto-activation phenomena occurred in such complex system, the obtaining of a high quality commercial phosphate concentrate was complicated by the presence of 18 Mg-containing minerals. The work presents the development of optimized blends of fatty acid based reagents with nonionic additives according to the specific mineral and textural properties of each sample in both direct and reverse flotation modes. The use of a mixture of fatty acid and nonionic reagent as an alternative for nonylphenol ethoxylates during the flotation of old tailings considerably increased the apatite concentrate grade (27-20 %) with P2O5 recovery of 40-64 %. Coupling new reagent suites and intensive flotation approach can transform the fine fraction of old tailings to a secondary source of phosphate. The concentrate grade increased by 4-6 % P2O5 and the recovery level of 40-46 % from a deslimed at 7 µm feed was achieved after rougher and one cleaner stage in a pilot-scale column, while the concentrate grade increased to 32-36% P2O5 with a higher recovery level at 58-61 % using the blend of collectors and an intensive flotation machine. The work performed allows to conclude that all samples tested can be regarded as future resources for additional phosphorus recovery. The approach developed was tested on the sedimentary ore samples and may be adapted to other low-grade igneous and sedimentary phosphate ores

Investigation of the Mechanism of Apatite/Carbonates Separation in Acidic Flotation Process Using In Situ Raman Spectroscopy

The separation of phosphate from carbonate gangue using flotation is extremely complex due to the similarities in surface properties. The acidic flotation process of carbonates at pH 4.5-5.0 followed by a direct phosphate flotation uses phosphoric acid as depressor of apatite during carbonate flotation. The mechanism of apatite depression is rather hypothetical because of lack of data on the surface speciation in such a complex mineral suspension. A real-time method for in situ control of surface compounds on the minerals (carbonated hydroxylapatite and calcite) using a submerged Raman analyzer probe is proposed in this work to collect the data on the nature and kinetics of phase formed. The carbonated hydroxyfluorapatite (C-HFAp) and calcite reactivity in phosphoric acid at concentrations between 0 and 1 M) during 15 minutes was studied. The Raman spectra collected in situ and ex situ showed the peak at 1085 cm-1 of calcium carbonate at 10-3 and 10-1 M on the surface of hydroxyfluorapatite that disappears at high acid concentration. Kinetics studies performed at 4.6 (±0.1) pH range during 15 minutes showed calcium carbonate formation after 2 minutes of conditioning and that disappears after three minutes (Figure 1). The infrared spectra of C-HFAp in presence of phosphoric acid showed at 10-3 and 10-1 M new peak at 713 cm-1 that belongs to calcium carbonate vibrations which seems to be due to C-HFAp surface conversion as observed on XRD patterns. Please click Additional Files below to see the full abstract

Geology, Textural Study, Ore Genesis and Processing of the Tabuaço Tungsten Deposit (Northern Portugal)

The Tabuaço tungsten deposit (Northern Portugal) is hosted in the Cambrian Douro Group metasediments, at the northern margin of the Beira-Tabuaço granitic complex. The hosting schisto-calcareous Lower Cambrian Bateiras Formation underwent a contact metamorphism induced by the intrusion of the granitic complex. The skarnification led to the crystallisation of scheelite (CaWO4). Two different skarn facies are encountered: ‘Lower Skarn’ and ‘Main Skarn’ both corresponding to the exoskarn. The ‘Main Skarn’ is mainly composed of vesuvianite (Ca10Mg2Al4(SiO4)5(Si2O7)2(OH)4), feldspars and fluorite. Zoisite, grossular, fluorapatite and scheelite are also present, as well as malayaite and cassiterite. Scheelite is disseminated and often occurs in association with fluorite, albite and vesuvianite. The ‘Lower Skarn’ level contains predominantly diopsidic pyroxene, quartz, zoisite, grossular and feldspars. Scheelite appears both laminated and disseminated, in association with fluorite and vesuvianite in minor proportions. The ‘Main Skarn’ is located in the Garnet, Pyroxene zone, while the ‘Lower Skarn’ corresponds to the Pyroxene, Garnet zone. Pyroxene has a global hedenbergite Hd40 composition. A major phase of albitisation destabilised fluorite, scheelite, vesuvianite, garnet and pyroxene. A late stage of chloritisation is associated with the exhumation. The processing of the Tabuaço ore has been adapted to the Ca-bearing rich paragenesis and to the scheelite mean size

Separation of lepidolite from hard-rock pegmatite ore via dry processing and flotation

ABSTRACT: A mineralogical study of Goncalo lithium-bearing mica-rich pegmatite ore (Portugal) indicated that lepidolite occurs in coarse-grained textures, which allows an appreciable liberation of gangue minerals (quartz, k-feldspar, and albite) from lepidolite. However, the intergrowth of these gangue minerals results in uncomplicated liberation (i.e., inclusions). Taking advantage of this coarse gangue liberation, optical ore sorting through image analysis was attempted in order to predict the grades of different-sized fractions using a random comminution algorithm. The ore-sorting process allowed the production of a marketable Li pre-concentrate product for metallurgy. Moreover, this method also highlighted the possible valuation of the reject as low-Li-content quartz-feldspar mixtures for the ceramic industry (reduction in the temperature of porosity closing). Furthermore, a scaled approach of grinding and sieving allowed the formation of a lepidolite-rich fraction (>210 mu m), which was processed using an electrostatic separator by varying key process parameters. The lepidolite and muscovite were separated to obtain a Li pre-concentrate assaying 3.5 % Li2O from a feed grade containing 1.8 % Li2O. Nevertheless, according to the zeta-potential measurements, the flotation test performed with the finer-sized fraction (-210 + 63 mu m) showed that lepidolite flotation was optimised between pH 3 and 5. In this pH range, concentrates from the rougher stage assayed 4.2-4.5 % Li2O, corresponding to 87-95 % Li recovery. At pH > 5, the selectivity decreases, and SiO2 analysis suggests the flotation of quartz and other silicates rather than lepidolite. Feldspar/quartz flotation was also tested using lepidolite flotation rejects to promote the separation of feldspars from quartz and obtain products for ceramic applications.info:eu-repo/semantics/publishedVersio

Modern youth's value orientations and activity in a cross-cultural context

Addressing the issue of youth's personal and professional development, taking into account their value orientations and psychological characteristics of their activity, seems to be relevant to the modern world's challenges. Cultural dimensions are believed to be the very factors that can contribute to a better understanding of the interplay between personal and environmental aspects when analysing the problem of high quality human resource development. The paper presents a cross-cultural study on cultural values characterising socio-economic and cultural settings of two countries and university students' basic values and parameters of their personal potential in the context of their activity. 307 university students from Tomsk (Russia) and 295 university students from Karaganda (Kazakhstan) participated in the study. The research tools involved a number of questionnaires aimed at exploring cultural dimensions, subjective evaluation of realisation of basic values in the urban environment and parameters of personal potential as factors of one's psychological system of activity. The study results revealed a number of statistically significant differences among the study participants. First, there was a difference in some cultural values, namely individualism, uncertainty avoidance and long-term orientation. Second, university students from Kazakhstan higher evaluated their urban environment in the context of possibility to realise their basic values. Third, the study participants from Kazakhstan showed higher scores in such parameters of their psychological system of activity as purposefulness, satisfaction with life, need for autonomy as well as the achievement and affiliation scales. Russian university students had higher scores in reflection which is a significant factor of one's self-determination. The results obtained are discussed in the context of modern youth's personal and professional development in a specific socio-economic and cultural environment

Spodumene Flotation Mechanism

Fine and coarse fractions of spodumene were obtained from a pegmatite ore and their flotation was investigated under different conditions. In particular, the optimum pH and collector dosage were studied. It was found that the best flotation performance occurs at pH 10 using 250 mg/L of sodium oleate. It was also observed that upon the addition of CaCl2, spodumene flotation recovery increases to about 90%. In addition, poor floatability was found for spodumene when Na2CO3 was used as a pH regulator (compared to NaOH).The zeta potential data confirmed the adsorption of oleate on the spodumene surface. It was found that activation of spodumene by calcium ions makes the surface charge less negative due to the adsorption of Ca2+ on the surface. The crystallographic properties of spodumene were analyzed. The adsorption of sodium oleate was attributed to the chemisorption of oleate to the exposed Al and Si sites generated after breakage of the Al–O and Si–O bonds on the mineral surface. It was observed that the {110} planes are the most favorable for the adsorption of oleate. The {110} plane is the weakest plane, and spodumene has the highest tendency to cleave along this plane. The XRD data revealed that fine spodumene particles have more {110} planes than the coarser fraction, which may explain why the former has better floatability

The Challenge of Tungsten Skarn Processing by Froth Flotation: A Review

International audienceRecently, tungsten has drawn worldwide attention considering its high supply risk and economic importance in the modern society. Skarns represent one of the most important types of tungsten deposits in terms of reserves. They contain fine-grained scheelite (CaWO4) associated with complex gangue minerals, i.e., minerals that display similar properties, particularly surface properties, compared to scheelite. Consistently, the froth flotation of scheelite still remains, in the twenty first century, a strong scientific, industrial, and technical challenge. Various reagents suitable for scheelite flotation (collectors and depressants, mostly) are reviewed in the present work, with a strong focus on the separation of scheelite from calcium salts, namely, fluorite, apatite, and calcite, which generally represent significant amounts in tungsten skarns. Albeit some reagents allow increasing significantly the selectivity regarding a mineral, most reagents fail in providing a good global selectivity in favor of scheelite. Overall, the greenest, most efficient, and cheapest method for scheelite flotation is to use fatty acids as collectors with sodium silicate as depressant, although this solution suffers from a crucial lack of selectivity regarding the above-mentioned calcium salts. Therefore, the use of reagent combinations, commonly displaying synergistic effects, is highly recommended to achieve a selective flotation of scheelite from the calcium salts as well as from calcium silicates

Evaluation of interaction mechanism for calcite and fluorapatite with phosphoric acid using electrochemical impedance spectroscopy

Flotation separation of apatite from calcite is difficult due to their same active calcium atoms on the surface. Flotation is mainly used to separate calcite and apatite minerals from each other and this can be done by knowing the interaction mechanism for each which is our aim here. Phosphoric acid is used to separate apatite and calcite. The outcomes showed that phosphoric acid had a strong depression ability to apatite but it does not for calcite. Herein, the interaction mechanism between minerals like calcite (36–100 μm) and fluorapatite of two size fractions (36–100 μm) and (20–100 μm) with phosphoric acid on 316L stainless steel, at 25 °C, was studied. Both materials are easily available, natural product, cheap and environmentally acceptable. Each mineral works with a different mechanism and this is confirmed by changing the shape for both Nyquist and Tafel plots after adding each mineral to phosphoric acid. Electrochemical impedance spectroscopy (EIS) showed that calcite materials work with both diffusion and adsorption mechanism, however, fluorapatite interaction mechanism is controlled by adsorption. Also, the dissolution of calcite material is higher than fluorapatite as confirmed by EIS and potentiodynamic polarization techniques. Results show that either increasing in concentration of the phosphoric acid or immersion time or size of particles, decreases passivation for both materials