| 1. |
- Nazari, S., et al.
(författare)
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Flotation of coarse particles by hydrodynamic cavitation generated in the presence of conventional reagents
- 2019
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Ingår i: Separation and Purification Technology. - : Elsevier. - 1383-5866 .- 1873-3794. ; 220, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic cavitation (HC) (typically used to generate submicron bubbles) are frequently examined to improve froth flotation efficiency of ultrafine particles (−38 µm); however, the study of their effects on flotation parameters during the process of coarse particles (+100 µm) was not significantly explored. The main aim of this investigation is to discover the impacts of HC on effective flotation variables and flotation recovery of coarse particles (FRCP). Various surfactants (frothers: Methyl isobutyl carbinol (MIBC) and pine oil (PO), and dodecyl amine (DDA)) were used for the HC conditions. For comparison purposes, two series of flotation experiments in the absence and presence of HC were conducted by using coarse pure quartz particles (−425 + 106 µm). Variable importance measurements (VIMs) of random forest were applied to compare and assess impacts of flotation parameters (particle size, flotation conventional bubble (CB) size, impeller speed, and air flow rate) on FRCP in the absence and presence of HC. Outputs of VIMs indicated that the negative effect of particle size on FRCP was decreased and the capability of CB for floating coarse particles was improved in the presence of HC. Moreover, VIM results showed that in the presence of HC, the highest FRCP can be achieved when turbulent is lower. Generally, variations in the airflow rate had negligible impacts on FRCP. Flotation experiments suggested that HC in the presence of the collector can overcome the absence of frothers in a flotation system. These results can be used for enhancement of selective separation via froth flotation.
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| 2. |
- Jafari, M., et al.
(författare)
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Examining the effects of typical reagents for sulfide flotation on bio-oxidation activity of ferrous iron oxidizing microorganisms
- 2017
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Ingår i: Solid State Phenomena. - : Trans Tech Publications. - 1012-0394 .- 1662-9779. ; 262 SSP, s. 84-87
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Tidskriftsartikel (refereegranskat)abstract
- Mineral separation by froth flotation is widely used around the world for the beneficiation of sulfide ores. Flotation products (typically concentrate) are subjected to metallurgical processes for metal extractions. Bioleaching as a metallurgical procedure indicated many advantages over other traditional techniques (pyro- and hydro-metallurgy). However, organic flotation reagent residuals on the surface of minerals are effective on biological activities of microorganisms. In this work, to extensively study these effects, typical sulfide flotation collectors (Sodium ethyl-xanthate, Potassium isopropyl-xanthate, Potassium isobutyl-xanthate, Potassium amyl-xanthate, and Dithiophosphate (Aero)), and frothers (pine oil (PO) and methyl isobutyl Carbinol (MIBC)) were used in the presence of various bacteria (Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans) to investigate their effects on bio-oxidation. The results of this investigation can be used to better understand the mechanisms of bio-activities when reagent residues are on the surface of flotation products and they will feed to the bioleaching process.
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| 3. |
- Nazari, S., et al.
(författare)
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Study relationships between flotation variables and recovery of coarse particles in the absence and presence of nanobubble
- 2018
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Ingår i: Colloids and Surfaces A. - : Elsevier. - 0927-7757 .- 1873-4359. ; 559, s. 284-288
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Tidskriftsartikel (refereegranskat)abstract
- Recent investigations indicated that using nanobubbles (NBs) in flotation separation of fine particles (<25 μm) has several advantages; however, a detail study on performances of various flotation parameters (such as hydrodynamic variables and particle properties) and their impacts on recovery of coarse particles (>100 μm) in the presence of NBs have not been fully understood. This work was explored how NBs can change impacts of Reynolds number, conventional flotation bubbles (CBs), air flow rate and particle sizes on flotation recovery of coarse particles (−425 + 106 μm). Several flotation experiments were carried out by using pure quartz in the presence and absence of NBs. Kendall’s tau (τ) as an accurate statistical method was introduced and applied through the provided dataset from the experiments to assess the impacts of NBs. In the absence of NBs; τ assessments demonstrated that there are negative correlations between particle size, air flow rate, Reynold number and recovery (τ ∼ −0.81, −0.18 and −0.12, respectively), and a positive relationship between CBs and recovery (τ ∼ 0.08). In general, results indicated that recovery of coarse particles was increased by ∼14% (on average) in the presence of NBs; however, the magnitude of relationships was not changed (just correlations between Reynolds and CBs vs. recovery were changed: τ ∼ −0.17 and 0.13, respectively). Assessing the simultaneous impacts of Re and CBs on recovery showed that in the presence of NBs; the highest recovery (on average) may receive in lower Re values and higher CB sizes in comparison with in the absence of NBs. Taking all these interactions into consideration, it can be concluded that increasing the rate of bubble-particle attachment and decreasing the impact of Re can be the main reasons for the enhancement of coarse particle recovery in the presence of NBs.
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| 4. |
- Golshani, T., et al.
(författare)
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Modeling and process optimization for microbial desulfurization of coal by using a two-level full factorial design
- 2013
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Ingår i: International Journal of Mining Science and Technology. - : Elsevier. - 2095-2686. ; 23:2, s. 261-265
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Tidskriftsartikel (refereegranskat)abstract
- The microbial sulfur removal was investigated on high sulfur content (1.9%) coal concentrate from Tabas coal preparation plant. A mixed culture of ferrooxidans microorganisms was isolated from the tailing dam of the plant. Full factorial method was used to design laboratory test and to evaluate the effects of pH, particle size, iron sulfate concentration, pulp density, and bioleaching time on sulfur reduction. Statistical analyses of experimental data were considered and showed increases of pH and particle size had negative effects on sulfur reduction, whereas increases of pulp density and bioleaching time raised microbial desulfurization rate. According to results of designing, and regarding statistical factors, the optimum values for maximum sulfur reduction were obtained; pH (1.5), particle size (−180 μm), iron sulfate concentration (2.7 mmol/L), pulp density (10%) and bioleaching time (14 d), which leaded to 51.5% reduction from the total sulfur of sample.
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| 5. |
- Jafari, M., et al.
(författare)
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Effect of Flotation Reagents on the Activity of L. Ferrooxidans
- 2018
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Ingår i: Mineral Processing and Extractive Metallurgy Review. - : Taylor & Francis. - 0882-7508 .- 1547-7401. ; 39:1, s. 34-43
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Tidskriftsartikel (refereegranskat)abstract
- Froth flotation is the most preferred processing technique for the enrichment of low-grade sulfides. Bioleaching is an eco-friendly method for metallurgical extraction from flotation products. Flotation reagents (collectors, frothers, etc.) have various impacts on bioleaching and bacterial activities. In this investigation, the effect of a number of sulfide flotation collectors [potassium amyl-xanthate, potassium isobutyl-xanthate, sodium ethyl-xanthate, potassium isopropyl-xanthate, and Dithiophosphate (Aero3477)], and frothers (pine oil and methyl isobutyl carbinol) with different dosages is studied on Leptospirillum ferrooxidans activities. The results of various measurements indicated that these flotation chemicals can have positive or negative influences on the bacterial activities, based on their chemical compositions and/or concentrations. These results can extensively be used for the selection of flotation reagents when bioleaching is chosen as the metallurgical extraction method after flotation enrichment.
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| 6. |
- Medronho, Bruno, et al.
(författare)
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Shear-Induced Transitions between a Planar Lamellar Phase and Multilamellar Vesicles: Continuous versus Discontinuous Transformation.
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:13, s. 6480-6486
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Tidskriftsartikel (refereegranskat)abstract
- The shear-induced transitions between an oriented lamellar phase and shear-induced multilamellar vesicles (MLVs) in a nonionic surfactant system were studied by deuterium rheo-NMR spectroscopy as a function of time in start-up experiments at several temperatures and shear rates. By starting from an initial state of oriented lamellae and observing the transformation to the final steady state of MLVs and vice-versa, two different mechanisms were found, depending on the direction of the transition and the initial state. The transition is continuous when MLVs are formed, starting from the oriented lamellar phase. On the other hand, a discontinuous nucleation-and-growth process with a coexistence region is observed when transforming MLVs into an oriented lamellar phase.
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