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In this study the extractive capability of Mextral 5640H was investigated for extraction of copper from a heap leach liquor. In this regard, the influence of parameters such as pH (0.2–2.8), extractant concentration in kerosene diluent (2.5%–10% v/v), temperature (25–70 °C), contact time (0–300 s), stirring speed (100–1200 rpm), phase ratio (O/A) (0.6–1.8) and Cu initial concentration (0.5–2 g/L) in the leach liquor were examined and optimized. The findings demonstrated that the Mextral 5640H extractant had a very high efficiency and selectivity in copper extraction from the leachate. 98.17% Cu, with less than 0.5% of Fe and Mn, were extracted at pH 1.6, 10% (v/v) Mextral 5640H concentration, ambient temperature (25 °C), 400 rpm stirring speed, 2 min contact time and an O/A phase ratio of 1:1. Under equilibrium conditions it was found that one mol of Cu is extracted by 7 mol of Mextral 5640H. Additionally, analysis using a McCabe–Thiele diagram suggests a two-stage extraction to reach the maximum extraction of copper (99.5%) from the leachate at operational condition using industrial mixer-settlers. Furthermore, a thermodynamic study was conducted, and the measured values of ΔH = 15.13 kJ/mol, ΔG = −6.95 kJ/mol and ΔS = 74.10 J/mol/K indicate an endothermic, spontaneous nature and high affinity of copper extraction.

In this study, the reject fraction of the jaw crusher, located in the first part of the crushing circuit, is used as a considerable stock in copper tank-leaching plant. High market value of copper and ease of practice were the motivating forces on studying the leaching kinetics under controlled conditions. In this regard, first, the influencing parameters such as the acid concentration, solid-to-liquid ratio, agitation speed, particle size, and temperature were assessed on the leaching fraction of copper. The findings showed that the leaching rate is nearly independent of the agitation rate at the high values of 300 rpm. The recovery of copper strongly promoted from 2 to 90% by increasing sulfuric acid concentration from 0.3 to 1.8 M. The increase in the solid-to-liquid ratio and temperature were found to be beneficial as well. Additionally, it was found that above 71% copper could be leached from the reject samples in the size range of 0–2 mm by 0.9 M sulfuric acid after 30 min contact time at 25 °C temperature. In the second stage, the leaching kinetics was studied by shrinking core models to gain a better description of the dissolution process of copper from crushing circuit reject. The results indicated that the dissolution rate could be controlled by both chemical reaction and diffusion process. However, diffusion process was the dominant mechanism in the system investigated. Ultimately, a mixed kinetic model with an activation energy of 11.72 kJ/mol was proposed as the leaching rate-controlling step.

The present study aims at assessing the potential application of CuPRO MEX-3302 in copper extraction from a heap leaching liquor. The role of influential significant parameters, including the leach...

This research investigated the treatment process of an Iranian zinc plant residue for recycling lead utilizing brine leaching and cementation with aluminum powder. Response surface modeling was employed for this purpose and accordingly, two quadratic mathematical models with R2 of 0.9058 and 0.9463 were identified for relationship between process parameters. The ANOVA and 3D response surface graphs exhibited that the leaching and cementation processes were significantly depended on the interactive effects between influential parameters. The interaction effects of liquid/solid ratio with NaCl concentration, temperature and stirring rate, and quadratic effect of NaCl concentration had the largest impact on the recovery. It was also distinguished that the most impressive parameters on the cementation performance were the linear effect of Al:Pb molar ratio, cementation time and temperature, and the quadratic impact of agitation rate. Additionally, numerical optimization was carried out by desirability function approach and the maximum leaching recovery of lead (77.14%) was achieved at 400 g/L NaCl concentration, 10 mL/g liquid/solid ratio, 300 rpm stirring speed, 50 °C temperature, and 60-min leaching time. Also, the highest cementation efficiency (74.97%) was determined after 75 min at 1.5 Al:Pb molar (stoichiometry) ratio, ~ 420 rpm agitation rate, and 50 °C temperature. Furthermore, thermodynamic conclusions implied an endothermic nature and good affinity of lead toward each two processes.

In the present work, the leaching behavior of copper from an oxide/sulfide ore was assessed in two work phases including process optimization and kinetics modeling. In the first phase, the individual and synergistic impacts of the influential parameters such as sulfuric acid concentration, liquid/solid ratio, pulp mixing rate, temperature, and contact time were investigated on the dissolution rate of copper using response surface modeling. The findings demonstrated that the linear effects of dissolution time and temperature and the quadratic impact of acid concentration had the largest influence on the recovery and the linear impact of stirring speed had the least degree of importance. Process optimization was also performed utilizing the desirability function approach and more than 88.17% copper was recovered at the optimum conditions: ~ 17% acid concentration, ~ 11.3 mL/g liquid/solid ratio, ~ 390 rpm stirring speed, 50 °C temperature, and 60 min leaching time. In the second phase, the leaching kinetics was examined by heterogeneous shrinking core models and it was realized that diffusion through product layer was the dissolution rate controlling step with the activation energy of 28.92 kJ/mol and frequency factor of 6.155 min−1. Ultimately, a mathematical kinetics model was developed and suggested to understand the leaching process. a 3D response surface graphs displaying the synergistic effects between “temperature and liquid/solid ratio” and “stirring speed and leaching time” on the leaching recovery of copper; b the optimum conditions of influential factors; c plot of diffusion through product layer versus leaching time for temperature effect.

This research investigates the extraction behavior of copper and zinc from the sulfate leachate of a porcelain stone tailings sample with Chemorex CP-150 and D2EHPA in detail. The findings demonstrated that Chemorex had greater ability and selectivity in the extraction of copper, while D2EHPA was better in the extraction of zinc. 97.88% copper and 78.2% zinc were extracted, respectively, with Chemorex and D2EHPA within 10 min contact time at an 1:1 aqueous/organic ratio, 10% (v/v) extractant concentration, and ambient temperature. The appropriate solution pH levels for Chemorex and D2EHPA were found to be 2.5 and 2, respectively. Also, a McCabe–Thiele diagram was drawn and one single-step extraction for copper and a two-stage process for zinc were needed to achieve the highest extraction efficiency. Additionally, the mechanism study indicated the association of ~ 1.5 and 1 mol of Chemorex CP-150 and D2EHPA for the extraction of one mole of Cu and Zn from the leach solution. Moreover, thermodynamic parameters, including ΔH, ΔG and ΔS were found to be 65.29 kJ/mol, 9.83 kJ/mol, and 186.14 J/mol K for copper and − 18.71 kJ/mol, 17.80 kJ/mol, and − 122.53 J/mol K for zinc, respectively, indicating that the extraction process was endothermic for copper and exothermic for zinc. The effect of contact time, pH, and extractants concentration on the extraction efficiency of Cu and Zn by Chemorex CP-150 and D2EHPA and also the number moles required for extractants

Mechanochemical sulfidization of a mixed sulfide/oxide copper ore by co-grinding with sulfur and additives including Mg(NO3)2 and Fe(NO3)3 salts and iron, aluminum and magnesium powders was investigated for the first time. Also, the influence of sulfidization during the wet-milling process was examined on the separation efficiency and recovery of copper in detail. The results demonstrated that co-grinding with sulfur solely had the best flotation performance at the value of 0.5 wt.% and it was attributed to the possible existence of S O bonding on copper oxides surfaces. In addition, adding magnesium nitrate salt, magnesium powder, iron nitrate salt and aluminum powder as additive associated with 0.5 wt% sulfur into ball milling caused the flotation improvement at the amounts of 0.2 wt%, 0.2 wt%, 0.5 wt% and 0.5 wt%, respectively. Also, the effect of grinding time and sulfidization pH with 0.5 wt% sulfur solely was determined and pHs of 7.5 to 8.5 gave the best results. The highest recovery (75.76%) and separation efficiency (63.44%) were achieved at pH of 7.5 and 8.5, respectively.

The present work introduces a new sorbent, so-called PANI/MIL100(Fe), for removing Pb (II) and Cr (VI) from wastewater. The successful preparation of PANI/MIL100(Fe) was verified via Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) characterizations. This adsorptive material showed a microporous structure with surface area magnitudes of up to 261.29 m2/g, a total pore volume of 0.2124 cm3/g, and a pore size distribution of around 1.2 nm. The maximum adsorption capacities of PANI/MIL100(Fe) for Cr (VI) (pH = 2) and Pb (II) (pH = 6) were obtained as 72.37 and 81.76 mg/g, respectively. The isotherm modeling assessments illustrated that the sorption of Pb (II) and Cr (VI) was consistent with the Sips model (R2 > 0.99), while the adsorption kinetics were suited to a pseudo-second-order model (R2 > 0.95). Thermodynamic studies of both metal ions demonstrated the spontaneous and endothermic nature of the process. The reusability of the PANI/MIL100(Fe) indicated promising adsorption properties for Pb (II) and Cr (VI) up to three cycles. Moreover, the XRD and FT-IR spectroscopy results after adsorption/desorption showed excellent stability of the adsorbent and physisorption mechanism, wherein electrons were exchanged between the PANI/MIL-100(Fe) and Pb (II) and Cr (VI). Finally, the findings suggested that PANI/MIL100(Fe) can be considered an efficient and environmentally friendly adsorbent to remove Pb (II) and Cr (VI) from wastewater.

This research was aimed to investigate the leaching behavior of zinc and copper from a porcelain stone tailings sample using RSM-CCD modeling. The synergetic and individual effects of five main factors including liquid/solid ratio, sulfuric acid concentration, agitation speed, leaching time, and temperature were examined on the recoveries of zinc and copper. For this purpose, two 2F1 models with R2 values of 0.9341 and 0.8693 were developed for the relationship between the leaching efficiencies of copper and zinc and effective terms, respectively. The results indicated that the leaching process was significantly influenced by the interactive effects between factors. The leaching recoveries increased by increasing all factors in the range studied. However, the recoveries were nearly independent of the agitation rate, indicating surface chemical reaction as the leaching kinetics controlling step. It was also found that the linear effect of temperature, the interaction effect of leaching time with liquid/solid ratio, and the interactive effect between sulfuric acid concentration and agitation rate had the greatest impact on the leaching rate of copper. Additionally, the linear effect of temperature and the interactive effect of temperature with agitation speed and liquid/solid ratio were distinguished to be the most effective factors on the recoveries of zinc. Moreover, the optimization was performed using desirability function approach, and the highest recoveries of copper (73.95%) and zinc (81.02%) were obtained at an acid concentration of 10%, 300 rpm agitation rate, 10 mL/g liquid/solid ratio, 35 °C temperature, and 75 min leaching time.

This study was aimed to increase the floatability of oxide copper from a complex copper sample. For this purpose, sulphidisation processes such as slug and controlled potential sulphidisati...

In this study, we investigates the application of three powerful kernel-based supervised learning algorithms to develop a global model of the wear rate of grinding media based on the input factors such as pH, solid percentage, throughout, charge weight of balls, rotation speed of mill and grinding time. It is found that there is a trade-off between the training and testing error when a single kernel function is used and therefore these methods cannot provide the generalization capability. However, this problem is solved utilizing the multiple kernel learning frameworks for support vector machine in which the kernel function was expressed as a combination of basis kernel functions. It is distinguished that compared to the single kernel and ANN-based techniques, the use of multiple kernel support vector machines benefit from a higher degree of correctness and generalization ability for prediction of wear rate of grinding media. Meanwhile, the findings indicate that in this state, the values of R2 are achieved 0.99417 and 0.993 for training and testing datasets, respectively.

In this research work, manganese ferrite nanoparticles (MnFe2O4) were synthesized by three different methods including the co-precipitation, sol-gel, and hydrothermal route. Structure, size, morpho...

Zinc is one of the most important metal required in metallurgical and chemical industries. As the high-grade resources diminished, the treatment of processing plants tailings can be considered as a metal significant source. Leaching is regarded as the first step of the hydrometallurgical methods and ferric sulphate/sulphuric acid leaching has been found to be as a highly effective technique for treating low-grade ores and tailings. Thus, this research was performed to describe the behavior of important factors affecting the leaching of zinc from a tailing sample obtained from lead-zinc flotation circuit in ferric sulphate and sulfuric acid media. It was found that 0.5 mol L−1 ferric sulphate is enough to dissolve both oxidized and sulphidic minerals. Response surface modeling was employed for parametric optimization (viz. stirring speed, sulphuric acid concentration, acid-to-ferric sulphate ratio and temperature). The findings showed the parametric degree of influence on zinc leaching was in order as: temperature > quadratic effect of stirring > quadratic effect of liquid/solid ratio > acid/ferric sulphate ratio > quadratic effect of sulphuric concentration. The optimum conditions established from model were found to be a stirring speed of about 320 rpm, 1.14 mol L−1 sulphuric acid concentration, 2.49 acid/ferric sulphate ratio, 10.10 ml/g liquid/solid ratio and 80 °C temperature. Under these conditions, the highest recovery of zinc was achieved of approximately 94.3%.

This study investigates the behavior of gold adsorption from cyanide leaching solution onto activated coconut shell carbon. The experimental was designed according to CCD implemented with RSM and a quadratic model was developed for regression analysis. The effects of important parameters including pH, agitation rate, adsorbent concentration and adsorption time were studied to find the best operating conditions, and the optimized value of pH, agitation rate, activated carbon concentration and adsorption time was found to be 11, 40 rpm, 1.25 g/L and 3 h, respectively. Under these conditions, the adsorption rate was found to be about 87.11%. Also, the optimal conditions were established on industrial cyanide leaching solution and the results demonstrated that adsorption rate of gold could be obtained about 89.25%. Adsorption behavior was kinetically investigated using pseudo first-order and pseudo second-order models among which data were mostly correlated to pseudo first-order model. The further analysis of kinetics indicated that intra-particle diffusion was the rate-limiting step. Adsorbate–adsorbent interactions at 298 k was assessed by Langmuir, Freundlich, and Temkin isotherm models from which Freundlich model had the highest consistency with the experimental data.

In present study, MnFe 2 O 4 /MWCNT nanocomposite synthesized using the hydrothermal technique and has been used for removal of DR16 and Y40 dyes from aqueous solutions. The characteristics results of FTIR, XRD, FESEM and TEM indicated that the nanoadsorbent was successfully fabricated. Magnetic sensitivity results demonstrated that the nanoparticles with saturation magnetization ( M s ) value of 8.93 emu g −1 would have a fast magnetic response. The performance of adsorption was investigated in a batch reactor employing parameters expected to affect the maximum adsorption capacity ( q m ) such as pH, contact time, initial dye concentration and temperature. The highest sorption capacities of DR16 and Y40 after 300 min at 328 K were found to be 607.79 mg/g and 280 mg/g at pH of 2 and 6, respectively. The adsorption behavior over the time was assessed through pseudo-first, pseudo-second and Weber–Morris intra particle diffusion models. It was found that the pseudo-second order model gave the best agreement to the experimental data. Adsorbate-adsorbent interactions as a function of temperature was evaluated by Langmuir, Freundlich, Temkin and Sips isotherm models from which Sips isotherm had the highest consistency with the experimental data. Thermodynamic parameters including Δ G °, Δ S ° and Δ H ° were determined over the temperature range of 298–328 K. The results revealed that the adsorption reaction of DR16 onto MnFe 2 O 4 /MWCNT was spontaneous and exothermic, whilst the sorption process of Y40 was spontaneous and endothermic. In addition, activation energy values implied that the removal process of DR16 and Y40 was physical in nature.

Nanocomposite of manganese ferrite/multiwalled carbon nanotubes (MnFe 2 O 4 /MWCNTs) was synthesized in aqueous media by hydrothermal method and its application as an adsorbent for Direct Red 16 (DR16) removal was investigated. Four important process parameters i.e., initial dye concentration (30–110 mg/L), temperature (25–45 °C), adsorbent dosage (2–6 mg) and contact time (10–210 min) were modeled and optimized to obtain the best response of DR16 removal using a central composite rotatable design (CCRD) combined with response surface methodology (RSM). The modeling results indicated that the influence degree of the factors on the adsorption capacity of MnFe 2 O 4 /MWCNTs was in the order of linear effect of initial concentration > linear effect of adsorbent dosage > quadratic effect of adsorbent dosage > interaction effect between adsorbent dosage and initial concentration > interaction effect between temperature and initial concentration. Also, contact time and temperature had no significant effect on the adsorption capacity statistically. The optimum conditions were found to be initial concentration = 89.95 mg/L, adsorption dosage = 3 mg, temperature = 30 °C and contact time = 158.56 min. Three confirmatory experiments were performed to evaluate the accuracy of the optimization procedure and maximum adsorption capacity of 285.56 mg/g was achieved under the optimized conditions.

The presence of institutional investors may change the behaviors of companies. The impact of institutional investors on management decisions on financial affairs have been proven in other studies; yet, the present study aims to investigate the relationship between lack of information symmetry an concentration of proprietorship with profit management in the companies listed in Tehran Stock Exchange. The period under study included years 2004 to 2009. Rahavard Novin Computer application was utilized to collect the data; then they were calculated using Microsoft Excel. SPSS computer application was used to test research hypothesis and conduct other statistical analysis using statistical methods like descriptive statistics, correlation (correlation coefficient, coefficient of determination), regression analysis and testing its coefficients, correlation analysis and test of coefficients and significance of the difference between two correlation coefficients. A total of 109 active companies in the stock exchange were selected as the sample of the study. Results on the first hypothesis revealed that the relationship between concentration of proprietorship and lack of information symmetry. In case of the second hypothesis, it is predicted that there is a significant relationship between profit management with lack of information symmetry and concentration of proprietorship. According to research results, investors and analysts ought to pay attention to factors like proprietorship composition, the level of information symmetry along with the figures published by the companies when making short and long-term decisions.

The purpose of this paper is to examine the impact of internal and external factors on the ratio of outstanding claims in those banks which are accepted in Tehran Stock Exchange. For this purpose, we used the data obtained from 8 banks and credit institution active in the Tehran Stock Exchange and using data regression panel. The present survey was examined over the period 2011 till 2015. The study includes three external variables (inflation, GDP and interest rates) and two internal variables (rate of return on assets and the size of the bank). The results of the hypothesis study showed that the rate of inflation, GDP and asset returns had significant negative effect on the ratio of outstanding claims. The results also showed a positive significant impact of the interest rates on outstanding claims, but there was no evidence to prove a significant impact of the banks size on outstanding claims.

In present research, MIL-100(Fe) was efficiently synthesized by hydrothermal strategy applying HF as mineralizing agent and its ability was examined for lead(II) and chromium(VI) adsorption from an aqueous environment. Structural, chemical and morphological properties of the synthesized MOF were specified by different experimental techniques including XRD, FTIR, SEM, EDS and adsorption isotherms of N2 at 77 ​K (BET). D-spacing was measured with Debye–Scherrer’s formula as 7.98 ​A. Also, the analyses confirmed relatively high BET surface area (1843.9 ​m2 ​g−1) and an octahedral-shaped structure for MIL-100(Fe) synthesized. Additionally, the adsorption behavior of lead(II) and chromium(VI) onto the MIL-100(Fe) was investigated using kinetics, equilibrium and thermodynamic parameters. Equilibrium analysis exhibited that the maximum uptake capacity for lead(II) was 23.46 ​mg ​g−1 based on sips model and for chromium(VI) was 30.45 ​mg ​g−1 ​by Langmuir isotherm. The sorption kinetics of lead(II) followed the pseudo 1st order model, while for chromium(VI) followed both pseudo 1st order and pseudo 2nd order models. Thermodynamic conclusions indicated a non-spontaneous nature for the sorption of each two metals and an exothermic reaction for lead(II) and endothermic nature for chromium(VI). Meanwhile, chemical ion-exchange and physisorption were distinguished as dominant adsorption mechanisms for lead(II) and chromium(VI), respectively.

The dominant challenge of current copper beneficiation plants is the low recoverability of oxide copper-bearing minerals associated with sulfide type ones. Furthermore, applying commonly used conventional methodologies does not allow the interactional effects of critical parameters in the flotation processes to be investigated, which is mostly overlooked in the literature. To tackle this issue, the present paper aimed at characterizing the behavior of five key effective factors and their interactions in a sulfidized copper ore. In this context, dosage of collector (sodium di-ethydithiophosphate, 60&ndash, 100 g/t), depressant (sodium silicate, 80&ndash, 120 g/t) and frother (methyl isobutyl carbinol (MIBC), 6&ndash, 10 g/t), pulp pH (7&ndash, 11) and agitation rate (900&ndash, 1300 rpm) were examined and statistically analyzed using response surface methodology. Flotation experiments were conducted in a Denver type agitated flotation cell at the rougher stage. The experimental results showed that increasing the pH (from 8 to 10) at low agitation rate (1000 rpm) enhanced the recovery from 80.36% to 85.22%, while at high agitation rate (1200 rpm), a slight declination occurred in the recovery. Meanwhile, increasing the collector dosage at a lower frother value (7 g/t), caused a reduction of about 4.44% in copper recovery owing to the interactions between factors, whereas at a higher frother level (9 g/t), the recovery was almost unchanged. The optimization process was also performed using the goal function approach, and maximum copper recovery of 92.75% was obtained using ~70 g/t collector, 110 g/t depressant, 7 g/t frother, pulp pH of 10 and 1000 rpm agitation rate.

Selectivity index (SI) and modified flotation rate constants of copper and iron were evaluated to rougher flotation circuit of the Sarcheshmeh copper ore by a series of batch flotation tests. Kinetics model of Agar was fitted to experimental data. The results indicated that first-order kinetics model of Agar presented the time–cumulative recovery curves of flotation tests quite well for Cu and Fe. Also, the results showed that the selectivity between Cu and Fe enhanced with increasing the pH, solid content, and dosage collector. In addition, performance of collectors showed that the best selectivity between Cu and Fe was in the order of combination of Z11 and MBTs > flomin C4132 > combination of MBTs and flomin C4132 > combination of Z11, MBTs, and flomin C4132 in flotation of copper. It was also found that better results for flotation kinetics were obtained at pH 11.5, solid percentage 28, and dosage collector 40 g/t (15 g/t sodium isopropyl xanthate and 25 g/t mercaptobenzothiazole [MBT]). SI va...

This study is aimed at determining the optimum mixing ratio and solvent group to extract REEs from nitric leach solution, and the efficiency was tested using three different kinds of extractants, which were prepared to mix three different solvents of Cyanex272, D2EHPA, and HQ. In order to select the best mixture system, different volumes (ml) of solvent extractions were used under optimum conditions (.05 M concentration and pH of 2). The result indicated that the mixture system of Cyanex272 (8 ml) and D2EHPA (2 ml) had the highest separation factor and enrichment ratio in the separation of rare earth element, especially dysprosium. The degree of performance of mixture systems in separation of the rare earth elements indicated that the best extraction systems were in the order of Cyanex272 (8 ml) and D2EHPA (2 ml) > HQ (2 ml) and D2EHPA (8 ml) > Cyanex272 (8 ml) and HQ (2 ml).

The leaching behavior of an Iranian copper oxide ore in sulphuric acid was investigated in detail to evaluate the influence of various factors, to optimize the dissolution conditions and to determine the kinetics of the leaching. The results indicated that the increase in the leaching time and temperature enhanced the leaching rate of copper. The leaching rate increased up to a certain value with increasing the agitation rate, acid concentration and liquid/solid ratio and with further increment reduced. Agitaion rate had the most influence on the dissolution of copper. The 3D response surface graphs confirmed the interactive effects of sulphuric acid concentration, agitation speed, and liquid/solid ratio with temperature. About 91% copper content was leached at~13% sulphuric acid concentration, stirring rate of 600 rpm, liquid/solid ratio of 10 mL/g and 50 °C after 80 min leaching. The dissolution kinetics was examined according to heterogeneous models. The shrinking core model assuming rate control by diffusion through the product layer was found appropriate to describe the dissolution of copper in sulphuric acid solution. The activation energy was obtained to be 26.699 kJ/mol and equation representing the leaching kinetics of copper based on diffusion-controlled model was found to be 1-3(1-x)2/3+2(1-x) = 161.97×exp(-26.699×103/8.314×T)×t.

This study was aimed to examine the influence of collector dosage, pH, solid content and water type of flotation pulp on copper recovery. The results indicated that recovery was strongly affected by these factors and their influence on the best composition of copper grade and recovery was in the order of water type>solid percentage>collector dosage>pulp pH. As the value of collector dosage, pH and solid content increased to a certain value, the copper recovery was enhanced to a peak and thereafter decreased. This may be due to the balance between reagent concentrations with pH and solid percentage. Copper recovery significantly increased with changing the water type from tap water to distilled water. The best combination of grade and recovery obtained was 7.26% and 81.09% in flotation tests with tap water.

Response surface plots showing the effect of two variables on recovery of copper (other two variables are held at center level): (a) pH and solid content and (b) pH and ratio Z11 to mercaptobenzothiazole when tap water was used in flotation tests.The performance of rougher flotation of the Sarcheshmeh copper ore was studied by a series of batch flotation tests. The D-optimal experimental design was employed to evaluate the effects of the main parameters including pH, solid content, water type, and ratio of Z11 collector to mercaptobenzothiazole on the recovery of copper into the concentrate. A response surface model was also fitted to results for the recovery of copper, which showed that the linear effects of solid percentage and ratio of collectors, the quadratic effect of pH, the interaction effect of solid concentration and pH, and the quadratic effect of water type and ratio of collectors were statistically significant. Using Design Expert software, it was shown that within the range of parameters inv...

The purpose of this study was to investigate the influence of grinding pulp pH and solid content on the performance of rougher flotation of Sarcheshmeh copper sulphide ore by a series of batch flotation tests. The results indicated that pH and solid percentage had extremely significant effect on recovery and grade of copper. Copper recovery of rougher cells strongly increased with increasing the pH and solid content, while as expected copper grade of rougher flotation reduced. In addition, the results demonstrated that maximum separation efficiencies are obtained in solid percentage, 55 and pH, 8, respectively. Finally, regression equations were proposed for correlation between recovery and grad of Cu with pH and solid content of grinding slurry.

The purpose of this study was to evaluate and rank the key factors affecting abrasive and corrosive wear of grinding media using fuzzy Delphi analytic hierarchy (FDAHP) method in grinding of copper sulphide minerals. There are many factors that affect the abrasive and corrosive wear of grinding media. Weight of each impact factor must be determined by using comprehensive scenario that is involved all the predicable grinding media wear issues. FDAHP applied to determine the importance degree of each factor. Significance of 27 effective main parameters is evaluated. The results indicate that composition and metallurgical properties of the grinding media, ore mineralogy, pulp viscosity, rheological properties and water chemistry throughout of grinding circuit and speed of the mill have the greatest weight in the abrasive wear. Moreover, composition and metallurgical properties of the grinding media, galvanic interaction between grinding media and mineral, ore mineralogy, water chemistry, pH, Eh and solid content had the highest degree of importance in corrosive wear, respectively. Furthermore, gas purging, Eh and discharge type of mill were the least significant factors in abrasive wear. Additionally, discharge type, diameter and speed of the mill were the least important factors in corrosive wear.

Particle-bubble sub-processes cannot be directly and physically obtained in froth flotation due to the complexity of the process as well as numerous and dynamic interactions of particles and bubbles in an extremely intensive turbulent condition. Therefore, over the last three decades, two fundamental model configurations have been used as an only solution for prediction of particle-bubble collection efficiencies (Ecoll). Additionally, the relative intensity of the main flotation parameters on flotation rate constant, particle–bubble interactions together with their interrelations is not adequately addressed in the literature. The present study attempts in two separate phases to overcome these difficulties. In the first stage, prediction and evaluation of particle-bubble sub-processes are critically discussed by categorizing them in two configurations. The analytical models (approach I) commonly applied generalized Sutherland equation ( E c G S E ), modified Dobby–Finch ( E a DF ) and modified Schulze stability ( E s SC ) models. The second approach, numerical models, utilized Yoon–Luttrell ( E c YL ), Yoon–Luttrell (intermediate) ( E a YL ) and modified Schulze stability ( E s SC ) models. In the second stage, relative intensity and interrelation of key effective hydrodynamic parameters on the probability of particle–bubble encounter (Ec) and flotation rate constant (k) are obtained and optimized by means of the response surface modeling (RSM) based on central composite design (CCD). Five key factors including particle size (1–100 µm), particle density (1.3–4.1 kg/m3), bubble size (0.05–0.10 cm) and bubble velocity (10–30 cm/s) together with turbulence dissipation rate (18–30 m2/s3) are considered in order to maximize the responses including the k and Ec. The results obtained show that the Ecoll calculated by numerical techniques (configuration (II)) is greater than that of analytical approaches (configuration (I)) due to assumptions involved in using Yoon–Luttrell collision and attachment models. It is also found that under the conditions studied, particle size and bubble velocity are the most effective factors on Ec and k, respectively. Furthermore, not only the relative significance of factors on Ec and k but also the interrelation of cell turbulence and bubble size as well as bubble velocity and turbulence are shown to be inconsistent in the literature and thus require further studies. We briefly reported the main long-standing challenges in flotation kinetic modeling and emphasized on a serious need for fulfilling lack of physical observations. Finally, the presented analyses with respect to three-zone model offer a new concept for the extension of common flotation modeling approach using analytical and numerical techniques.

The performance of rougher flotation of the Esfordi phosphate ore was studied by a series of batch flotation tests. A central composite experimental design was employed to evaluate the effects of six main parameters on the recovery of phosphate and iron into the concentrate. A response surface model was fitted to results for the recovery of P2O5, which showed that the linear effects of conditioning time and co-collector, and the quadratic effects of conditioning time and solid concentration, were statistically significant. The significant parameters for the recovery of iron were the linear effects of pH, solid concentration, collector and conditioning time, the interaction effect of solid concentration and depressant, and the quadratic effect of pH. Using Design Expert software, it was shown that within the range of parameters investigated, a P2O5 recovery of 90.4% with a Fe recovery of 6.6%, could be obtained. The optimized values of the parameters were verified on feed samples and compared with the actu...

Much has been written lately concerning the failure of several major corporations to report their financial statuses accurately. Enron, Global Crossing, IBM and others have failed to provide accurate information to their investors and to provide full disclosure of liabilities that would influence the valuation. The present paper is focusing on creditors as a main group of accounting information users, which have been neglected, in field of information presentation. To solve this problem we introduce a new financial statement called “the commitments statement”. In the beginning, we point out financial reporting goals and users` informational needs. Then, we mention the issue, which creditors’ informational needs have not been well provided; and the reasons are explained. We continue with inspection of providing information related to solvency and recognition of financial flexibility of entities. Finally, we introduce “the commitments statement” and explain how to provide this statement. We end with the conclusion section.

This study investigates the alkaline oxidation pretreatment process of Zarshuran refractory gold ore. Taguchi method-orthogonal array design (OAD) is applied to evaluate and optimize the influence of five main factors including solution pH, aeration rate, agitation speed, temperature, and oxidation time. In order to establish relationship between the gold dissolution rate and influential factors, a linear regression model with R2 of 0.9706 is fitted to experimental data. The results indicated that in the range studied, the agitation speed does not have any significant impact on the gold recovery, while oxidation time and temperature were the most significant factors. Au recovery increased with increasing the aeration rate, pretreatment time, and temperature as well as decreasing the solution pH. Using Taguchi orthogonal array optimization technique (OAOT), the maximum gold recovery was about 96.72%. Also, the optimal conditions were 11 for solution pH, 150 ml min−1 for aeration rate, 240 rpm for agitation rate, 50 °C for temperature, and 24 h for oxidation time.

Effects of vitamin E and pyrroloquinoline quinone on peripheral nerve regeneration were studied using a rat sciatic nerve transection model. Ninety male healthy White Wistar rats were divided into three experimental groups (n = 15), randomly: Sham-operation (SHAM), transected control (TC), chitosan conduit (Chit) and three treatment groups (Vit E, PQQ and PQQ + Vit E). In SHAM group after anesthesia, left sciatic nerve was exposed through a gluteal muscle incision and after homeostasis muscle was sutured. In Chit group left sciatic nerve was exposed the same way and transected proximal to tibio-peroneal bifurcation leaving a 10-mm gap. Proximal and distal stumps were each inserted into a chitosan tube. In treatment groups the tube was implanted the same way and filled with Vit E, PQQ and PQQ + Vit E. Each group was subdivided into three subgroups of six animals each and were studied 4, 8, 12 weeks after surgery. Functional and electrophysiological studies, and gastrocnemius muscle mass measurement confirmed faster and better recovery of regenerated axons in Vit E + PQQ combination compared to Vit E or PQQ solely (P

In this study, the dissolution of lead from a low grade oxide ore in HCl, H2 SO4 , HNO3 and citric acid solutions was investigated in a batch reactor employing parameters expected to affect the dissolution rate such as stirring speed, liquid to solid (L/S) ratio, temperature and acid concentration. The maximum recovery of lead were obtained to be 85.52% after 90 min with inorganic acids at 20%, 80 °C, 500 rpm and L/S = 20 ml/g, while the maximum dissolution was determined to be 73.81% with citric acid. Also, H2 SO4 was not able to dissolve lead from low grade oxide ore. The dissolution kinetics of lead was examined according to heterogeneous models. It was found that the dissolution rate was controlled by the diffusion through the fluid film (1 − (1 − x )2/3 ) in HNO3 and citric acid solutions with the activation energies of 7.71 and 11.62 kJ/mol, respectively. Additionally, when the dissolution was performed in the presence of HCl, the surface chemical reaction in an initial stage (0–30 min) and fluid film diffusion in a second stage (after 30 min) were the rate controlling steps. The activation energies of these sequential steps were determined to be 60.94 and 28.24 kJ/mol, respectively.

This paper describes a simple and more reliable artificial neural network (ANN) method and multiple linear regression (MLR) to predict the gold recovery and to simulate the effects of pH, solid percentage, NaCN concentration, particle size and leaching time during cyanidation process. Feed-forward ANN with back-propagation learning algorithm with 5-9-1 arrangement was found capable to predict the recovery of Au from cyanide leaching solution. The results showed that simulated values obtained by the network were very close to the experimental results. The coefficient of determination value (R2) was 0.9803 for training set, and in testing stage the R2 value was 0.8213. On the contrary, the correlation coefficients were low for the results predicted by MLR method. R2 values obtained 0.5561 and 0.6705 for training and testing data, respectively. The results obtained from this paper can be considered as an easy and cost-effective method to simulate the cyanide leaching process of gold.