Rapid decolourization of Methyl Orange by Fenton-like mesoporous Fe₂O₃–SiO₂ catalyst has been reported. The effect of various parameters such as initial pH, initial H₂O₂ concentration, Fe content in ...the catalyst and initial dye concentration on decolourization process were studied. The results show that 20mg of mesoporous Fe₂O₃/SiO₂ composite (with Si/Fe=10) was sufficient to decolourize 0.6mg/ml of Methyl Orange in presence of 2ml of H₂O₂ at an initial pH of 2.93 within 20min. The pH range for effective decolourization (≥90%) was found to be 1–3. Leaching tests indicated that the activity of the catalyst was almost unaffected up to three consecutive cycles although ≤0.2ppm of Fe ion was leached into treated water in each run.
The technology for beneficiation of banded iron ores containing low iron value is a challenging task due to increasing demand of quality iron ore in India. A flotation process has been developed to ...treat one such ore, namely banded hematite quartzite （BHQ） containing 41.8wt% Fe and 41.5wt% SiO2,by using oleic acid, methyl isobutyl carbinol （MIBC）, and sodium silicate as the collector, frother, and dispersant, respectively. The relative effects of these variables have been evaluated in half-normal plots and Pareto charts using central composite rotatable design. A quadratic response model has been developed for both Fe grade and recovery and optimized within the experimental range. The optimum reagent dosages are found to be as follows： collector concentration of 243.58 g/t, dispersant concentration of 195.67 g/t, pH 8.69, and conditioning time of 4.8 min to achieve the maximum Fe grade of 64.25% with 67.33% recovery. The predictions of the model with regard to iron grade and recovery are in good agreement with the experimental results.
•Soluble, corn, rice and potato starch have depressing action on hematite.•Soluble starch is a better depressant compared to other starches.•FTIR, adsorption, zeta potential studies supported ...starch–hematite interaction.•Reverse flotation studies indicated ∼65% Fe with 85% recovery.
Four different starches, namely soluble starch, corn starch, potato starch and rice starch with different characteristics have been studied as depressants for hematite in cationic flotation using dodecylamine as the collector. Surface charge measurement and Fourier transform infrared spectroscopy (FTIR) have been used to understand the starch–hematite interaction. The lowering of surface charge and change of peaks at 750–1500cm−1 region indicate the presence of hydrogen bonding and chemical interaction between hematite and starches. The results of flotation studies with pure minerals of hematite and quartz and a low grade iron ore at different conditions suggest that all the starches are good depressants for hematite. Maximum adsorption for all the four starches with hematite occurs at the pH value 5–9. However soluble starch is found to be the better depressant at slightly alkaline pH. The flotation of natural occurring banded iron ore using different starches has indicated that it is possible to achieve an iron grade of 63–65% Fe with 85–88% recovery.
The depletion of high-grade iron ores has necessitated the beneficiation of low-grade iron ores. Flotation is considered the most efficient operation to upgrade the iron content of fine-grained ores ...that do not respond to gravity or size classification units. Out of several reagents used in iron ore reverse flotation, depressants play a crucial role in selectively making the iron oxides hydrophilic and prohibiting them from reporting to the gangue-rich froth phase. Starch is widely used as the depressant in iron ore flotation. The present paper attempts to highlight different facets of starch as an iron ore depressant. It reviews the important research papers that discuss the origin and chemistry of starch, starch-iron oxide interaction mechanism, and the application of different types of starches and their alternatives in iron ore flotation.
•Quaternary ammonium based IL’s attempted as collectors for quartz flotation.•Effect of alkyl chain length assessed through XPS and molecular modelling.•IL–quartz interaction governed by van der ...Waals and electrostatic forces.•IL with 6 carbon in alkyl chains gives the maximum coverage and floatability.•IL’s are found to be better than conventional quartz collectors.
Application of quaternary ammonium based ionic liquids (IL’s) as flotation collectors of quartz has been investigated. Effect of number of carbon atoms in the four identical alkyl chains of the IL’s has been studied. The adsorption behaviour of the IL’s on the quartz surface is ascertained through FTIR, XPS and molecular modelling. The FTIR peak at 2900cm−1 indicates the adsorption of the IL’s onto the quartz surface, which is further substantiated by the appearance of the N (1S) peak in the X-ray photoelectron spectra (XPS). Curve splitting data of C (1S) suggests the maximum adsorption for the IL tetrahexylammonium iodide (THEX). Flotation results of pure quartz using ionic liquids are found to be better compared to the conventional collectors such as dodecylamine (DDA) or cetyltrimethylammonium bromide (CTAB). It is possible to float 92–100% quartz by using a THEX concentration of 4.8 × 10−5M. IL collectors are further applied in the flotation of a low grade banded hematite quartzite (BHQ) iron ore with ∼38% Fe. It is possible to achieve an iron concentrate of 63.6% Fe at 63.2% recovery by using THEX as the collector. Molecular simulations using the COMPASS forcefield explains the IL–quartz adsorption mechanism comprising of both electrostatic and van der Waals forces. Floatability of quartz has been correlated with the surface coverage and adsorption energy calculations. The IL’s used here are found to be better quartz collectors than the conventional ones as they show better collecting efficiency in lower dosages. Flotation using these IL’s does not require frothers which is an added advantage compared to the conventional collectors.
•Plane wave periodic DFT study of oleate-iron oxide interaction.•Magnetite-oleate complex is more stable than hematite and goethite.•Flotation recovery of magnetite is more compared to the other two ...oxides.
Comparative studies of oleate interaction with hematite, magnetite and goethite using density functional calculations are presented. The approach is illustrated by carrying out geometric optimization of oleate on the stable and most exposed planes of hematite, magnetite, and goethite. Interaction energies for oleate-mineral surface have been determined, based on which, magnetite is found to be forming the most stable complex with oleate. Trend as obtained from the quantum chemical calculations has been validated by contact angle measurements and flotation studies on hematite, magnetite and goethite with sodium oleate at different pH and collector concentrations.
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•TOMAS, an ionic liquid is used in quartz flotation for the first time.•Flotation recovery of quartz with TOMAS is better than that with DDA.•Consumption of TOMAS is much lesser than ...DDA.•Adsorption of TOMAS on quartz confirmed by zeta potential, FTIR and XPS.•Molecular modeling supports stronger adsorption of TOMAS with quartz.
Tricaprylmethyl ammonium salicylate (TOMAS), an ionic liquid has been employed as a collector for the flotation of quartz. The sign reversal of zeta potential of quartz from negative to positive values and increase in contact angle from 80 to 700 by the addition of TOMAS have substantiated the interaction of TOMAS with the quartz surface. The change in morphology as indicated in SEM and two peaks at 2933 and 2857cm−1 owing to the vibrations of CH2 and CH3 as seen in FTIR spectra support the adsorption of the reagent on quartz. The N(1s) peak as observed in the XPS spectra of the quartz treated with TOMAS, and the curve fitting data of C(1s) corroborate the reagent-mineral interaction. A comparative study of adsorption of DDA and TOMAS using classical molecular mechanics also suggests stronger adsorption of the latter on the hydroxylated quartz surface. Flotation studies of quartz at natural pH indicate ∼100% quartz recovery at a TOMAS concentration of 8*10−5M. Flotation of the natural occurring BHQ iron ore containing 38.7% Fe and 43.8% SiO2 concludes that a TOMAS concentration of 3.71*10−5M is sufficient to achieve 67.3% Fe with 66.6% iron recovery. TOMAS stands out as a better quartz collector, when compared with DDA.
Ionic liquids (ILs) are finding applications in various domains of physical sciences these days. They are used in organometallic syntheses, catalysis, electrochemistry, fuel, solar cells, lubricants, ...enzyme, separation technologies, nanomaterials, tissue preservation etc. However, the application of ILs in the area of mineral processing is minimal. Considering the potential use of ILs in metal extraction and many chemical reactions, these compounds may play an essential role in the selective recovery of mineral values from the ores having multiple mineral phases. In this paper, the application of some selected ILs in the mineral flotation studies has been reviewed. The interaction of ILs with the desired mineral phases has been described vide the evidence from zeta potential, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy (XPS), Fourier Transform Infra-Red (FTIR) spectroscopy, Raman spectra as well as molecular modeling studies. The results of the studies carried out on low-grade iron ores have indicated that ILs under investigation can be compared with the conventional iron ore collectors such as dodecylamine.
•Imidazolium, ammonium & pyridinium ILs as flotation collectors of quartz.•Flotation with quartz, quartz-hematite mixture and BHQ ore.•FTIR and XPS studies to establish the adsorption ...mechanism.•Better flotation results in the case of ammonium and pyridinium collectors.
The application of imidazolium, ammonium, and pyridinium based ionic liquids (ILs) as the flotation collectors of quartz has been investigated. The flotation studies have been carried out for pure quartz, quartz-hematite synthetic mixture and a low grade banded hematite quartzite (BHQ) ore while the trend of floatabilities has been explained in terms of the structural differences of the ILs. The flotation of pure quartz using the ammonium and pyridinium based IL collectors has exhibited an excellent performance; where about 100% quartz could be floated at a collector concentration of 5∗10−5M. The results are found better compared to the imidazolium ILs and conventional quartz collectors like dodecylamine (DDA) and cetyl trimethyl ammonium bromide (CTAB). The ammonium and pyridinium based collectors also show better iron grade and recovery compared to the imidazolium collectors during the reverse flotation of the synthetic hematite-quartz mixture and BHQ ore. Using these collectors, an iron ore concentrate of ∼62% Fe at ∼75% recovery could be obtained from the BHQ ore containing ∼38% Fe. In the Fourier Transform Infra Red spectroscopy (FTIR), the peak intensity at 2900cm−1 due to the presence of alkyl groups signifies the extent of adsorption of the collectors on quartz. The N/Si ratio and CC peak area as determined by the X-ray photoelectron spectroscopy (XPS) results show the relative adsorption of the IL collectors. The pyridinium based IL collector show better adsorption strength compared to all others ILs under study. The better flotation results in the case of the ammonium and pyridinium collector are attributed to the presence of higher alkyl chain length inducing better hydrophobicity.
•DFT calculations to establish the mechanism of quartz–amine interaction.•Ester and ether amines are stronger quartz collectors than primary amines.•Increase in chain length enhances the interaction ...but up to a limit.•Position of functional groups in the alkyl chain influences the interaction.
This study illustrates a density functional theory (DFT) based approach to design the amine collectors with regards to their interaction with the quartz surface. Mechanism of interaction of primary aliphatic amines and their ether and ester derivatives with the quartz surface has been established. Hydrogen bond geometries and adsorption energies as calculated using DFT reveal that ester amines are stronger surfactants compared to the ether amines and primary alkyl amines. Simulation studies carried out for the different amines with number of carbon atoms varying from 10 to 18 suggest that increasing the number of carbon atoms in the alkyl chain enhances the interaction, but not beyond C14 for primary amines and C16 for its ether and ester derivatives. Presence of both ether and ester group in the alkyl chain facilitates its interaction strength. Adsorption strength of C12 amine containing both ether and ester amine is almost equivalent to that of C16 ester amine.
