The aim of this work has been to examine the effect of intensive ball milling of sphalerite in the wet and dry modes on the microstructural changes and the subsequent effect on its dissolution rate. Sample characterization showed that the BET surface area and the amorphization degree were obtained to 18.2 m2/g and 78.92% in the wet mode and 7.72 m2/g and 90.35% in the dry mode milling after 180 min, respectively. The maximum extraction of Zn obtained 23.7, 67.12 and 85% in the unmilled, wet and dry milled samples, respectively. The ratio of kinetic rate constant has been increased by 37 and 67 times, respectively. Also, the activation energy was decreased with increasing of milling time. Selectivity of sphalerite leaching versus surfa

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 metho

The number and positioning manner of the ligands present in the first shell of every cation of rare earth elements are key parameters in determining the stoichiometry of the reactions of solvent extraction from nitrate systems, especially when acidic extractants are used. In addition to determining the hydration and coordination of nitrate ligands around lanthanum and yttrium cations in an aqueous electrolyte, this paper investigated stoichiometry by combining the results of studies on molecular dynamics simulation and solvent extraction experiments. The analysis of the results of the Radial Distribution Function clearly showed the presence of one and two nitrate ligands, respectively, in the first hydration shells of lanthanum and yttrium.

In this study, precipitated calcium carbonate (PCC) has been produced using a semi-continuous carbonation process within Ca(OH)2(s)-CO2(g)-H2O system inside a bench-scale reactor. In order to understand the effect of temperature, solid percent of the milk of lime (MOL), CO2 gas injection rate, agitation rate on the conductivity, the specific surface area, microporous surface area (and subsequently agglomeration), and reaction termination time, an experimental procedure was used based on a central composite design (CCD). The conductivity and pH were applied as the parameters controlling the reaction termination time. Using the data obtained from the multiple regression analysis, the effect of the parameters on the above-mentioned responses w

The discharge of toxic elements from tailings soils in the aquatic environments occurs chiefly in the presence of indigenous bacteria. The biotic components may interact in the opposite direction, leading to the formation of a passivation layer, which can inhibit the solubility of the elements. In this work, the influence of jarosite on the bio-immobilization of toxic elements was studied by native bacteria. In batch experiments, the bio-immobilization of heavy metals by an inhibitory layer was examined in the different aquatic media using pure cultures of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A variety of analyses also investigated the mechanisms of metals bio-immobilization. Among different tests, the highest m

This study aimed to introduce a new approach to determine the mass transfer rate constant in a laboratory column flotation through an analogy to a mass transfer process. The RTD of the column at two separate bubble sizes were modeled using both conventional N-mixer and N-mixer with back-mixing flow models. The number of perfect mixers (N) and the corresponding backflow coefficients (λ) were optimized using MINLP solver in MATLAB environment where N?=?5 with λ?=?0.567 at the bubble size of 1.8?mm and N?=?8 with λ?=?0.643 at the bubble size of 0.8?mm were obtained. The bubble active surface coefficient was introduced as a new parameter to study the flotation kinetics. Thus, the mass transfer rate constant was determined for various operati

The flow patterns and turbulence characteristics of the flow fields in a mechanical flotation cell have important effects on the hydrodynamic and metallurgical responses. In this study, the effect of cell geometry (off-bottom clearance (C), cell aspect ratio (H/T) and impeller diameter (D) on the turbulence properties and flotation performance using pure quartz particles of different sizes in a lab-scale Denver flotation cell was investigated. The results showed that the change in cell geometry changed the local turbulence characteristics. The change of C (from 0.2?T to 0.1?T), D (from T/2 to T/3) and H/T (from 1.2 to 1.5) did not change the flow pattern. The lower C was recommended to improve flotation performance. The larger D (T/2) was m

The paper presents the effect of impeller speed and superficial gas velocity on bubble-particle attachment, detachment and collection efficiencies using pure quartz particles in a mechanical flotation cell. Detachment and collection efficiencies in different parts of cell were calculated by local turbulent energy dissipation rate measurements using high speed stereoscopic particle image velocimetry technique. In addition to high detachment efficiency, low attachment efficiency is also one of the reasons for low collection efficiency for coarse particles. The flotation rate constant increased with an increase in superficial gas velocity. However, the effect of superficial gas velocity on collection efficiency was negligible. This means that

The interaction of gold cyanide complex with elemental sulphur and all metastable sulphur species has been studied using Density Functional Theory (DFT). The elemental sulphur and sulphide species formed during pre-treatment of refractory gold ores or dissolution of sulphide minerals form a series of metastable species including hydrosulphide, polysulphide, thionates, sulphite and finally sulphates which are known to have a detrimental effect on gold cyanidation. Previous researchers have attributed this effect mainly to passivation of the gold surface. However, interaction of dissolved aurocyanide with sulphur species has received almost no attention. Here, DFT molecular modelling has been used for the first time to describe the interactio

In this study, the effect of various ions with different radius and charge such as aluminum, calcium, and iron on the selective ion flotation of neodymium using sodium dodecyl sulfate as a collector was investigated. Firstly, the optimum conditions of neodymium ion flotation were determined by evaluating the main factors on the process efficiency including collector dosage, air flowrate, and pH. The optimum conditions for ion flotation of neodymium are as following: collector dosage?=?21?× 10−4?M, air flow rate?=?100 mL/min, and pH?=?3 with 85.4% and 26.5% recovery for neodymium and water, respectively. Then, the effect of other ions on the ion flotation of neodymium was evaluated.

Although bioleaching of chalcopyrite by thermophilic microorganisms enhances the rate of copper recovery, a high temperature accelerates iron precipitation as jarosite, which can bring many operational problems in the industrial processes. In this research work, the bioleaching of chalcopyrite concentrate by the thermophilic Acidianus brierleyi was studied, and the microbial growth, copper dissolution, iron oxidation, and jarosite precipitation were monitored in different initial pH (pHi) values. Bacterial growth was greatly affected by pHi. While the bacterial growth was delayed for 11 days with a pHi value of 0.8, this delay was reduced to nearly one day for a pHi value of 1.2. Two stages of copper recovery were observed during all the te

Copper oxide minerals such as malachite do not respond well to the traditional copper sulfide collectors, and require alternative flotation schemes. In many copper ore mines, significant copper oxide minerals, especially malachite, are associated with sulfide minerals. Considering that xanthates are most widely used in the flotation of sulfide minerals as well as copper sulfide minerals and, hydroxamate has shown a good selectivity for copper oxide minerals. Use of the synergistic effect of xanthate and hydroxamate can be an effective way to increase the flotation efficiency of copper oxide minerals along with sulfide minerals. In this work, we investigate the individual interactions of potassium amyl xanthate (PAX) and potassium alkyl hydr

In the current research, isothermal experiments of kinetic analysis were performed at different temperatures (800–1050 C) and particle sizes (885 to 10,763 μm) to investigate the calcination kinetics of high-purity limestone. Thermal analyses were carried out in a zirconia crucible, 1 cm in height, for different temperatures and particle sizes. The reaction rate coefficients were varied in the 2.2? 10− 5-1.62? 10− 3-m 0.6. s− 1 range. Moreover, various isothermal kinetic analysis methods were applied to assess the decomposition mechanism and the calcination function governing the process. The modified shrinking core model was found as the best representation of the high-purity limestone kinetic data. The activation energy was evalu

Copper oxide minerals such as malachite do not respond well to the traditional copper sulfide collectors, and require alternative flotation schemes. In many copper ore mines, significant copper oxide minerals, especially malachite, are associated with sulfide minerals. Considering that xanthates are most widely used in the flotation of sulfide minerals as well as copper sulfide minerals and, hydroxamate has shown a good selectivity for copper oxide minerals. Use of the synergistic effect of xanthate and hydroxamate can be an effective way to increase the flotation efficiency of copper oxide minerals along with sulfide minerals. In this work, we investigate the individual interactions of potassium amyl xanthate (PAX) and potassium alkyl hydr

Nugget effect is a common feature of many vein-style gold deposits. This style of mineralization results in complication in many exploitation stages including resource and average grade estimation, representative sample selection, ore characterization as well as processing. Accurate and reliable ore characterization is a vital stage in any mineral processing project. Ore characterization in high nugget effect gold ores is so complex due to uncertainties associated with representativity of the selected sample. The main challenge is to provide a representative sample for identification of each process mineralogy parameter such as average grade, liberation, grinding size, mineral association, floatability, etc. Here, different protocols are co

In this study, the feasibility of improving the flotation circuit performance of a phase 1 of Sungun copper plant was investigated. For this purpose, circuit performance was first monitored ., It was found that in the rougher stage the some copper exists in fractions greater than 106 and smaller than 38 microns was lost. Final concentrate analysis taken on different days showed that the copper grade decreased due to the iron content increasing. Mineralogical studies also confirmed the maximum presence of pyrite in the final concentrate. Field surveys of the flotation circuit showed that there are many technical problem in the circuit that affect on the flotation process. These drawbacks including the presence of thick tubes at the surface o

One of the challenges in the rare earth elements (REE) production industry is the difficulty of separating them from each other. Therefore, in the present study, the possibility of cerium separation from carbonate concentrate of REEs containing 22.75% Ce, 9.4% La and 8.6% Nd (total REEs of 41.51%) was investigated. Two methods were used to separate Ce from other REEs. In the first method, due to the very low solubility of Ce4+, the calcination of carbonate concentrate and conversion of cerium carbonate to cerium oxide and selective dissolution of other REEs from the calcine were investigated. In the second method, prior to the carbonate precipitation of REEs, the possibility of cerium oxidation in the sulfate solution (by using potassium pe