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In hydrometallurgical and mineral processing operations, slurries are often prepared at very small grind sizes and high solids concentrations. The presence of yield stress or flow limits results in flow anomalies as the slurry tends to stagnate close to vessel bottom, walls, and at any internal surface. The preparation of high-concentration slurries preferably in low shear rate ranges consuming less power is an integral part of high-concentration slurry transportation systems. Therefore, during mixing of such concentrated slurries, the selection of appropriate agitation equipment for preparation of a homogeneous suspension requires a thorough investigation. The rheological behavior of ground manganese nodule samples in solids concentration range of 55–65% by weight using both distilled water and sea water as mediums have been evaluated and the discrepancy in yield stress and plastic viscosity values affected by solids concentration and medium has been discussed and presented in the paper. The performance characteristics of a helical ribbon mixer influenced by fluid rheology, medium, and agitator rotational speed were evaluated. The appropriateness of the agitator for preparation of high-concentration manganese nodule slurry was further substantiated by comparing the experimental power consumption data with the theoretical power consumption values computed using Bakker and Gates correlations. [ABSTRACT FROM AUTHOR]

Mine backfilling with power plant ash is gaining increasing attention from the power and mining industries for its bulk disposal. In the USA and other countries, mine backfilling with ash is considered as a viable option for stability improvement, subsidence control, and mine site rehabilitation. This paper presents the results of rheological studies conducted on fly ash and mixtures of fly ash and bottom ash samples collected from NTPC Talcher, Odisha. The complex hydro-mixture slurry indicated non-Newtonian pseudo-plastic behavior in the mass concentration range of 60–67.5%. A non-Newtonian power law head loss model was used to evaluate the head loss of ash slurry in pipelines having nominal bores in the range of 100–300 mm. The results indicated that the addition of bottom ash to fly ash slurry at a given solids concentration has a beneficial effect in reducing the pumping power requirement. A design chart for the fly ash mixture slurry has been formulated indicating the variation in backfilling rate with relative head requirements for a given length of pipeline for a range of pipe sizes and transport velocities. This is expected to provide relevant pipe flow and operational conditions for bulk disposal of fly ash for mine backfilling purpose. [ABSTRACT FROM AUTHOR]

The present study encompasses the first ever attempt of the usage of cow dung as a reductant in the reduction roasting of an Indian iron ore slime containing 56.2% Fe. The resultant reduced mass generated a concentrate of ~ 64% Fe with a weight recovery ~ 66% after being subjected to low intensity magnetic separation (LIMS). The optimum conditions of roasting as determined by the Taguchi statistical design were found to be temperature: 700 °C, time: 45 min and reductant to feed ratio: 0.25:1. Under similar conditions, the conventional reductant charcoal (fixed carbon: 93.5%, volatile matter: 1.2%) could result in a product of ~ 66% Fe at ~ 35% weight recovery proving cow dung (fixed carbon: 8.66%, volatile matter: 41.27%) to be a better reductant. The cow dung cake and some of the reduced products were subjected to integrated instrumental techniques such as X-ray Diffraction (XRD), Scanning Electron Microscope attached with an Energy Dispersive Spectroscopy (SEM-EDS) and Electron Probe Micro-Analysis (EPMA), which revealed the formation of new phases such as hercynite, corundum, iron aluminium silicate along with magnetite and wustite, at different levels of operating parameters, thereby explaining the role of different reduction variables. [ABSTRACT FROM AUTHOR]

Since the sulfur specific cleavage is vital for the organic sulfur removal from fossil fuel, we explored potential bacterial strains of MTCC (Microbial Type Culture Collection) to desulfurize the Dibenzothiophene (DBT) through C-S bond cleavage (4-S pathway). MTCC strains Rhodococcus rhodochrous (3552), Arthrobacter sulfureus (3332), Gordonia rubropertincta (289), and Rhodococcus erythropolis (3951) capable of growing in 0.5 mM DBT were examined for their desulfurization ability. The presence of dsz genes as well as the metabolites was screened by polymerase chain reaction (PCR) and HPLC, respectively. All these strains showed > 99% DBT desulfurization with 10 days of incubation in minimal salt medium. From the HPLC analysis it was further revealed that these MTCC strains show differences in the end metabolites and desulfurize DBT differently following a variation in the regular 4-S pathway. These findings are also well corroborating with their respective organization of dszABC operons and their relative abundance. The above MTCC strains are capable of desulfurizing DBT efficiently and hence can be explored for biodesulfurization of petrochemicals and coal with an eco-friendly and energy economical process. [ABSTRACT FROM AUTHOR]

The adsorption behaviour of heavy metallic ions such as Co (II), Pb (II) and Zn (II) on an Al-Si-O mineral system mostly comprising of pyrophyllite and diaspore was explored via experimentation and first principle calculations. The characterization studies involving X-ray Diffraction (XRD), Electron Probe Micro-Analysis (EPMA), Scanning Electron Microscope attached with Energy Dispersive Spectroscopy (SEM-EDS) in addition to the quantitative mineralogical analysis under reflected light microscope revealed the presence of pyrophyllite {Al 2 Si 4 O 10 (OH) 2 } as the major mineral followed by the phases like diaspore {α-AlO(OH}, corundum (Al 2 O 3 ), kaolinite {Al 2 Si 2 O 5 (OH) 4 } and muscovite {KAl 2 (AlSi 3 O 10 )(F,OH) 2 } in the decreasing order of abundance. The adsorption data fitted well to the Langmuir isotherm with Co (II) having the maximum monolayer capacity of 9.23 mg/g while the pseudo second order model could explain the sorption behaviour for all the metallic ions. The adsorption capacities of the metallic salts followed the order Co (II) > Pb (II) > Zn (II). Density Functional Theory (DFT) based calculations validated the experimental trend of adsorption capacities indicating that Co atom is able to coordinate on the constituent mineral surfaces in a much stronger manner compared to the other two metal atoms. While corundum (0 0 1) plane was found to the best adsorbing plane among all the mineral planes considered over here, the interaction of the metal atoms on the edge surface of pyrophyllite (0 1 0) was stronger compared to that on its basal plane (0 0 1). [ABSTRACT FROM AUTHOR]

Indian low grade iron ores mostly contain quartz, gibbsite, and clay as the major impurities. Depending upon the ore characteristics, in many instances froth flotation has to be used to recover the hematite and other iron oxides from the ground ores. In this context, the difference in silica and alumina content in low grade iron ores is brought to bear on the prospects of iron ore flotation. For this purpose, pure minerals like hematite, quartz, gibbsite, and clay have been used to prepare synthetic mixtures and analyzed to determine the difference in floatability. The results are compared against natural iron ores with variations in silica and alumina content. The flotation results with oleic acid and dodecylamine show better recovery of iron values in the hematite–quartz mixture as well as in the naturally occurring high silica ore compared to the hematite–clay mixture and the high alumina ore respectively. Similarly results on a variety of iron ores show that high silica content as quartz in the ore causes less hindrance in the flotation of iron ore, whereas the presence of silica as clay inhibits the flotation response of iron ore. The scanning electron microscopic (SEM) studies indicate that clay particles cover the surface of hematite, making it less selective for interaction with the collector. The surface potential studies of clay and quartz suggest that charge reversal takes place for quartz treated with dodecylamine (DDA), but for the DDA adsorption on clay, negative potential values are noted beyond a pH of 4.6. [ABSTRACT FROM AUTHOR]

The surface behavior of the natural ruby stones before and after heat treatment with metal oxide additives like: zinc oxide (ZnO) and lead oxide (PbO) have been studied. The surface appearance of the ruby stones processed with the metal oxides changed whereas the bulk densities of the stones remained within the range of 3.9–4.0 g/cm 3 . The cracks healing and pores filling by the metal oxides on the surface of the ruby have been examined using scanning electron microscopy. The chemical compositions based on the XPS survey scans are in good agreement with the expected composition. The phase and crystallinity of the ruby stones original and heat-treated were obtained from their X-ray diffraction patterns. The change in peak separation between R 1 and R 2 – peaks in photoluminescence spectra and the contrary binding energy shift of the Al 2p peaks in the X-ray photoelectron spectra have been explicated. Moreover, in this work we describe the change in surface chemical and physical characteristics of the ruby stone before and after heat treatment. [ABSTRACT FROM AUTHOR]

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 C 14 for primary amines and C 16 for its ether and ester derivatives. Presence of both ether and ester group in the alkyl chain facilitates its interaction strength. Adsorption strength of C 12 amine containing both ether and ester amine is almost equivalent to that of C 16 ester amine. [ABSTRACT FROM AUTHOR]

Highlights: [•] Iron reducing bacteria reduced goethite to hematite in chromite overburden. [•] An adapted consortium showed efficient bio-reduction in chromite overburden (COB). [•] Phase changes lead to exposure of metals embedded in the goethite matrix. [•] Leaching of treated COB yielded enhanced nickel and cobalt recovery with 8M H2SO4. [Copyright &y& Elsevier]

Abstract: Acidithiobacillus ferrooxidans biofilm grown on uranium ore substrate was analyzed by a micro-Raman spectrometer and an atomic force microscope (AFM). The bacterium employed for this study, A. ferrooxidans BM1, was isolated from a uranium mine (Jaduguda, India). Micro-Raman analysis revealed the different constituents of molecular fragments present in microbial cells and in secreted extracellular polymeric substances (EPSs). AFM images clearly revealed bacterial cells surrounded by EPS. From Raman spectral data, the composition of EPS from A. ferrooxidans BM1 appeared to be similar to that of EPS secreted in a different Pseudomonas bacterium. [Copyright &y& Elsevier]