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Improvement of chalcopyrite atmospheric leaching using controlled slurry potential and additive treatments

Jafari M., Karimi G., Ahmadi R.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

1228--1240

EN

In this study, the synergistic effects of the oxidation-reduction potential (ORP) of leaching slurry and additives (pyrite, sodium chloride and silica) on chalcopyrite atmospheric leaching were investigated. According to the best results of leaching experiments, in the optimum ORP range of 410-430 mV, galvanic (pyrite mass ratio of 4:1), chemical (1.5 mol/dm3 sodium chloride concentration), galvanochemical (pyrite mass ratio of 4:1 and 1.5 mol/dm3 sodium chloride concentration) and mechanical (30 g/dm3 silica concentration) treatments provided 29.8, 46.4, 48.6 and 6.7% increase in the copper recovery, respectively. In galvanic treatments, effective surface corrosion of chalcopyrite was the reason for enhanced chalcopyrite dissolution. In chemical and galvanochemical treatments, considerable surface porosity of chalcopyrite was responsible for accelerated leaching. Also, in mechanical treatments, removing the remained passive layer from the chalcopyrite surface improved leaching. SEM results showed extensive porosity in the chalcopyrite surface in the presence of pyrite and sodium chloride and even more porosity in the presence of their combination. SEM results also showed obviously clean surface of chalcopyrite in the presence of silica. The comparison of ORP-assisted and non-ORP-assisted experiments showed that there were 8, 5.2, 3.9 and 0.5% more copper recoveries in galvanic, chemical, galvanochemical and mechanical treatments with ORP assistance, respectively. The reason was the fewer chalcopyrite surface passivation, which caused the additives to perform better.

2

Determination of bubble size distribution in a laboratory mechanical flotation cell by a laser diffraction technique

Mazahernasab R., Ahmadi R.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 2

690--702

EN

In this study, a laser diffraction technique (LDT) was used to measure size distribution of bubbles generated in a two-phase system in a laboratory mechanical flotation cell. In LDT, a laser light beam passed through the bubbles inside the measurement cell and the scattered light was recorded by detectors. In order to show the effectiveness of LDT, an image analysis technique (IAT) was applied in parallel to measure the size of bubbles. To determine the bubble size by IAT, around 200 images were taken in each test. In addition, the important operating parameters of the mechanical flotation cell affecting the bubble size distribution, including the impeller speed, aeration rate and frother concentration, were investigated. The response parameter in this study was Db(50) which represent the size of bubble at which there is 50% of the distribution. The results of this study showed that the LDT and IAT techniques were in a good agreement when Db(50) was in the range of -800+400 μm and there was a discrepancy for Db(50) in the range of -400+100 μm. Furthermore, Db(50) decreased from 727 to 284 μm when impeller speed increased from 700 to 1200 rpm. Additionally, an increase in the aeration rate from 1 dm3/min to 2.5 dm3/min led to a rise in Db(50) from 418 to 456 μm. Finally, increasing the frother concentration from 10 to 60 ppm reduced the Db(50) from 704 to 387 μm.

3

Kinetics of oxygen adsorption on ZnS nanoparticles synthesized by precipitation process

Ahmadi R., Sadrnezhad S. K., Zangeneh R. N., Oghabian M. A.

Materials Science Poland

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2016

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Vol. 34, No. 2

260--265

EN

ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD), ultraviolet (UV) visible absorption and photoluminescence (PL) spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate oxygen adsorption capacity was suggested as a means of PL emission intensity control.

4

An investigation on the optimum conditions of synthesizing a magnetite based ferrofluid as MRI contrast agent using Taguchi method

Ahmadi R., Hosseini H. R. M.

Materials Science Poland

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2013

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Vol. 31, No. 2

253--258

EN

In this study, some stabilized magnetite based ferrofluids were synthesized using Dextran as a stabilizing agent. In order to achieve optimum experimental conditions for synthesizing ferrofluids as MRI contrast agents, the Taguchi method was used. This approach was employed to design and minimize the number of required experiments. By using the Taguchi orthogonal (L16) array, four parameters including solution temperature and alkalinity, reaction temperature and stirring rate were selected at four predetermined levels for 16 experiments. Synthesizing processes established based on this set of experimental conditions were carried out and the obtained ferrofluids were characterized using PCS, VSM, TEM and FT-IR techniques. The obtained results were used and analyzed through the Qualitek-4 software and the proposed optimum experimental conditions were used for synthesizing the desired sample. Finally, this sample was used as a potential MRI contrast agent for imaging lymph nodes.

5

Synthesizing cysteine-coated magnetite nanoparticles as MRI contrast agent: Effect of pH and cysteine addition on particles size distribution

Ahmadi R., Ranjbarnodeh E., Gu N.

Materials Science Poland

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2012

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Vol. 30, No. 4

382--389

EN

Cysteine capped magnetite nanoparticles (10 to 20 nm) were synthesized via coprecipitation method under ultrasonic irradiation. The influence of pH value of the solution and cysteine addition on the size distribution and hydrodynamic size of nanoparticles were studied via TEM and PCS methods, respectively. The crystal structure and magnetic properties of the nanoparticles were characterized by XRD and VSM techniques, respectively. Coating density was calculated using TGA and TEM results. Cytotoxicity assessment performed by incubation of L929 cells, confirmed that ferrofiuids are biocompatible. MRI studies conducted on rats demonstrated suitability of synthesized nanoparticles as contrast agents, especially for imaging of the lymph nodes.