International Journal of Mineral Processing最新文献

Copper is commonly produced by hydrometallurgical processes. The production of this metal results in the formation of emissions (unwanted solids, liquids and gases). In this paper, an effluent from a Cu producer company is valorized by means of Fe and Cu recovery.

In the current process, an effluent from the secondary solvent extraction (secondary raffinate) was sent to neutralization plant to be discharged. In this paper a modification of the process is proposed. The secondary raffinate was contacted with TP207 resin for Fe^3 + and Cu recovery. Metals were eluted from the resins using another real effluent (primary raffinate, effluent from the primary solvent extraction) from the same plant.

Experiments for the uptake and elution were carried out in batch and in columns. The effect of pH, resin dosing, and temperature onto metals retention are analyzed. Retention efficiencies (loading capacities) were 50.1% (8.1 mg·g^− 1) for Cu and 54.8% (23.2 mg·g^− 1) for Fe^3 + under the optimal operational conditions (pH = 0.45 and T = 65 °C). These values were confirmed in column tests. It is possible to recover Fe^3 + and Cu from the secondary raffinate, leaving most of Fe^2 + and other elements in solution. The experimental affinities that TP207 showed are: Cu > Fe^3 + > Fe^2 + > Zn.

The elution of Fe and Cu was quantitatively achieved with concentrated H₂SO₄ solution. When acidified primary raffinate was used as eluting solution, an enriched solution containing 14.3 g Cu·L^− 1, 20.3 g Fe^2 +·L^− 1, and 18.6 de g Fe^3 +·L^− 1 was obtained. This enriched primary raffinate can be reintroduced in the process as leaching solution.

So, after the modification of the process, using secondary raffinate as loading solution and acidified primary raffinate as eluting solution, the ion-exchange stage could substitute the external FeSO₄ addition. In addition, 30–80 kg Cu·h^− 1 are reintroduced in the process.

In this paper we report on X-ray studies on amorphization of pseudowollastonite following 30 min mechanical activation using a centrifugal planetary mill AGO-2 in atmospheric air. In addition, milling resulted in chemical reaction which led to the formation of calcium carbonate and silica. In general, the chemical composition of the sample corresponded to the formula CaSi_0.997C_0.014O_3.02. Theoretically calculated scattering intensity for a model of mechanical mixture corresponded to the following ratio: 0.75 scattering intensity of the cluster consisting of four unit cells of pseudowollastonite disordered in a molecular dynamic experiment; 0.25 scattering intensity of the cluster consisting of one unit cell of CaCO₃; 0.25 scattering intensity of the cluster consisting of one unit cell of α-SiO_2. The R-factor for scattering intensity I(s) was 5.5%. The curve of s-weighted interference function H(s) calculated for the model coincided with the experimental curve. Characteristics of tetrahedra arrangement in the initial pseudowollastonite cluster and in the same cluster after molecular dynamic were calculated by the method based on the searching for a coordination polyhedra in the clusters and the constructing of graphs.

Biological reduction of soluble selenate to insoluble elemental selenium enables the removal and recovery of selenium from aqueous streams. Economic, efficient biological selenium recovery depends on properties of selenium particles such as size, density, stability, hydrophilic character and attachment to the biomass. In batch and fed-batch reactors using anaerobic sludge, the influence of pH (6-9) and temperature (20–50 °C) on the morphology, structure and stability of the biologically produced selenium particles were studied using SEM, XRD, and light microscopy. At a high pH or a high temperature these experiments resulted in grey crystalline hexagonal acicular selenium particles, while at a low pH combined with a low temperature red amorphous nanospheres were dominant. Particle stability tests were carried out by changing the temperature or pH after the particles had formed. Red amorphous selenium spheres (produced at pH = 7 and 30 °C) transformed gradually towards the grey hexagonal structure at 50 °C over a period of three weeks, whereas the transformation was less or not detected under other process conditions (according XRD). We show here that biological selenium particle crystallinity, shape and color can be controlled by temperature and pH. However, the choice for the temperature and pH in the bioreactor should not limit the biomass' reduction capacity of selenate. The production of crystalline particles is an important first step to grow larger selenium particles in the future in order to reduce costs for selenium recovery in bioreactors.

Optical sorting is increasingly playing an important role in mineral processing. Therefore, a better understanding of this method is required concerning general properties and mineral sorting applications. To date, optical sorting has been widely studied in terms of industrial applications and performance evaluation particularly in mineral processing. Nevertheless, process optimization requires better understanding of qualitative and quantitative figures based on real life sorting applications.

In this study, the relationship between feed rate and separation efficiency of a gravity type and visible light responsive sensor mounted optical sorter (VIS sorter) was investigated. In addition to the feed rate, the effect of particle size on separation performance was also discussed. Laboratory studies included a selection of material, sample preparation, and optical sorting tests with magnesite, quartz, lignite, hematite, copper and gold ore samples. Experimental studies performed with different size fractions at varying feed rates were followed by evaluation of results with ROC (receiver operating characteristics) graphs. Recovery, grade, and capacity indicators are important to define the efficiency of the optical sorting. Alternatively, ROCs highlight missing particles and false alarm rates, which are used to characterize set points and detectability of the equipment/operation. In the tests performed with quartz and magnesite samples, % weights of valuable (white) and non–valuable (colored) particles in products were directly used to express the performance of optical sorting with ROC. Additionally, % Fe content, % dry ash content, % copper recovery and % gold recovery figures were used to define the ROC parameters for hematite, lignite, copper and gold ore samples.

Results showed that the performance of the VIS type optical sorter mainly depends on correctly sorted amounts of valuable and non–valuable particles. Alongside with the evaluation of change in sorting performances in accordance with feed rate, ore type, and particle size; pre-concentration of copper and gold ores, concentration of hematite from alkaline waste, dry cleaning of lignite and market quality magnesite and quartz sorting applications with VIS type optical sorter were also discussed.

Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) and diagnostic leaching (DL) are the two main methods to evaluate the gold refractoriness nature. Limited availability of QEMSCAN or its cost sometimes can be the drive to use DL method, or vice versa.

We present the results of a comparative study that investigates and compares the origin of the refractoriness of two different gold samples with QEMSCAN and DL. As a baseline, the gold recovery values of samples 1 and 2 via the standard cyanidation process over a leaching period of 24 h were 74% and 54%, respectively. Based on the DL tests, the refractoriness of samples 1 and 2 was mostly related to the fine dissemination and association of the electrum (Au-Ag alloy) and gold telluride with the sulfide minerals, particularly pyrite. The QEMSCAN analysis provided more details about the gold deportment in the two samples. The QEMSCAN results showed that the gold in the two samples was mostly present as electrum and gold-telluride. In sample 1, about 89% of the gold occurred in the form of electrum with a 63% Au and 36% Ag composition. The main gold form in sample 2 was gold-telluride (81%). Energy dispersive X-ray spectroscopy (EDS) results demonstrated that the gold telluride phase was in the form of calaverite (AuTe₂) in both samples. The QEMSCAN results suggested that 77% of gold in sample 1 and 88% of gold in sample 2 were liberated or locked in the sulfide minerals, and the balance was the solid solution gold. Based on the QEMSCAN study, the total liberated gold and the gold locked in the sulfide minerals are expected to be amenable to cyanide leaching after a complete sulfide oxidation process, i.e. pretreatment. DL tests, however, suggested that 91% of the gold in sample 1 and 87% of the gold in sample 2 were leachable after the oxidation of sulfides in the two samples.

Lastly, the two samples were pretreated by (1) roasting, and (2) atmospheric oxidation to oxidize sulfide minerals and render the samples more amenable to cyanide leaching. The gold recoveries of the roasting calcines by cyanidation were 93% and 76% for samples 1 and 2, respectively. The cyanidation of the atmospheric oxidation residues provided a greater gold recovery for both sample 1 (96%) and sample 2 (85%). Gold recovery for sample 1 was underestimated by QEMSCAN, however the gold recovery values were estimated well by DL.

The underground separation of gangue from coal is an important part of the process of reducing transportation costs and improving production efficiency. A new method is proposed in this paper to separate gangue from coal on the basis of density, calculated from volume using three-dimensional (3D) laser scanning technology. This approach is based on the laser triangulation method and weight. Taking into account the weigh-in-motion technology that is currently widely applied, the main objective of this approach is to determine the volume of the object being measured. Thus, the principles of 3D laser scanning and laser triangulation were studied in detail and a relative formula was deduced. The reasons and solutions for possible errors are also analyzed in this paper, depending on the method applied to measure volumes of gangue and coal. Physical relationships of objects to be measured, as well as laser and measuring data planes are also presented, depending on principles of 3D laser scanning. A parameter selection method is presented to determine the appropriate photoelectric recognition device to use for coal or gangue, while error due to voids between objects was measured, and transportation belts analyzed. The assumption put forward in this study is that the ratios of voids between objects, transportation belt, and the exact volume of objects all conform to a normal distribution; this was shown to be the case by both experiments and statistical theory. A mathematical model was therefore constructed that is suitable for the recognition of coal and gangue based on this theory, while algorithms of recognition threshold values and identification rate are presented.

Collophane is an important phosphate mineral, which has proven to be difficult to float from gangue. In this work, the novel application of reactive oily bubbles to enhance collophane flotation is reported. Three different types of bubbles, conventional air bubble, oily bubbles (kerosene only) and reactive oily bubbles (kerosene containing fatty acids) approaching collophane particles were studied by measurements of zeta potential, induction time and contact angle. The reactive oily bubble shows negligible effects on the zeta potential of collophane particles. A shorter induction time of reactive oily bubble was found at pH 6.0 and/or at pH 9.0 relative to the conventional air bubbles and the oily bubbles. This suggests a strong collection power of reactive oily bubble. Advancing contact angles of the reactive oily bubble on collophane increased dramatically with pH. At pH 9.0, a contact angle of 120 degrees was observed where the reactive oily bubble flotation is anticipated. Micro-flotation results demonstrate the superiority of reactive oily bubbles over air bubbles for collophane flotation. A concentrate containing 35.67% of P₂O₅ and 0.39% of MgO was obtained using reactive oily bubble flotation at pH 9.0. Micro-flotation results also show that Ca^2 + and Mg^2 + ions have a negative effect on the collophane flotation, but the effect of reactive oily bubble system is smaller than that of air bubble system.

This paper introduced dextran sulfate sodium, a medical intermediate rich in sulfate group, as a potential depressant for calcite and fluorite in scheelite flotation. The flotation behaviors of scheelite, calcite and fluorite under different pulp pH with dextran sulfate sodium acting as depressant and sodium oleate acting as collector were studied through micro-flotation tests. The results showed that when sodium oleate was used alone, the three minerals floated well and were difficult to separate. Dextran sulfate sodium exhibited a selective depressant effect on calcite and fluorite flotation when it was added before sodium oleate. Using dextran sulfate sodium as depressant could achieve the preferential flotation separation of scheelite from calcite and fluorite by control of pulp pH at 7.0. The selective depressant effect of dextran sulfate sodium on calcite and fluorite was explored through surface analyses including zeta potential measurements, contact angle measurements and FTIR studies on mineral samples treated with dextran sulfate sodium and/or sodium oleate. On the basis of the surface analyses, a selective adsorption model of dextran sulfate sodium on calcite and fluorite was proposed.

Flotation, which exploits the differences in the surface wettability of minerals to effect separation, has been crucial in rare earth elements (REE) beneficiation. Monazite, a phosphate mineral commonly containing REE (typically lanthanum, cerium, and neodymium), occurs in association with hematite and quartz gangue minerals in some low grade deposits. In this study, the physicochemical properties including contact angle, zeta potential, and floatability of monazite, hematite, and quartz were determined in the presence of oleic acid as a collector. Contact angle measurements indicated adsorption of oleic acid onto the minerals' surfaces. Zeta potential measurements were used to elucidate oleic acid adsorption mechanism onto the mineral particle surfaces. Results from zeta potential measurements indicated that depressants are required to achieve selective flotation recovery of monazite from hematite and quartz. The flotation test results confirmed poor selectivity between monazite; and hematite and quartz, respectively. However, rare earth oxides (REO) in monazite floated better than both hematite and quartz at all the oleic acid dosages investigated. The use of sodium silicate and starch as depressants enhanced the selective flotation recovery of REO from hematite and quartz mixtures.