Microbially induced flotation and flocculation of pyrite and sphalerite

Cells of Paenibacillus polymyxa and their metabolite products were successfully utilized to achieve selective separation of sphalerite from pyrite, through microbially induced flocculation and flotation. Adsorption studies and electrokinetic investigations were carried out to understand the changes in the surface chemistry of bacterial cells and the minerals after mutual interaction. Possible mechanisms in microbially induced flotation and flocculation are outlined.     

Microbially induced separation of quartz from hematite using sulfate reducing bacteria

Cells and metabolic products of Desulfovibrio desulfuricans were successfully used to separate quartz from hematite through environmentally benign microbially induced flotation. Bacterial metabolic products such as extracellular proteins and polysaccharides were isolated from both unadapted and mineral-adapted bacterial metabolite and their basic characteristics were studied in order to get insight into the changes brought about on bioreagents during adaptation. Interaction between bacterial cells and metabolites with minerals like hematite and quartz brought about significant surface-chemical changes on both the minerals. Quartz was rendered more hydrophobic, while hematite became more hydrophilic after biotreatment. The predominance of bacterial polysaccharides on interacted hematite and of proteins on quartz was responsible for the above surface-chemical changes, as attested through adsorption studies. Surface-chemical changes were also observed on bacterial cells after adaptation to the above minerals. Selective separation of quartz from hematite was achieved through interaction with quartz-adapted bacterial cells and metabolite. Mineral-specific proteins secreted by quartz-adapted cells were responsible for conferment of hydrophobicity on quartz resulting in enhanced separation from hematite through flotation.     

Surface chemical studies on selective separation of pyrite and galena in the presence of bacterial cells and metabolic products of Paenibacillus polymyxa

Selective separation of pyrite and galena from mixture of the two minerals was achieved through interaction with cells and metabolic products from a culture of Paenibacillus polymyxa. Adsorption of cells and metabolic products onto minerals and electrokinetic studies of minerals after interaction with cells and metabolic products were carried out to examine the resulting surface modification on the mineral surfaces. Flocculation and flotation techniques were successfully applied in the selective separation of minerals after bacterial interaction. The effect of varying conditions for production of extracellular polysaccharides and protein provided an insight into the possible mechanism involved in microbially induced flocculation and flotation of pyrite and galena.     

Determination of the critical surface tension of wetting of minerals treated with surfactants by shear flocculation approach

This paper contributes the shear flocculation method as a new approach to determine the critical surface tension of wetting of minerals treated with surfactants. This newly developed approach is based on the decrease of the shear flocculation of the mineral suspension, with decreasing of the surface tension of the liquids used. The solution surface tension value at which shear flocculation does not occur can be defined as the critical surface tension of wetting (gamma c) of the mineral. By using the shear flocculation method, the critical surface tensions of wetting (gamma c) for calcite and barite minerals, treated with surfactants, were obtained as 30.9 and 35.0 mN/m, respectively. These values are in good agreement with data reported previously on the same minerals obtained by the contact angle measurement and flotation methods. The chemical agents used for the treatment of calcite and barite particles were sodium oleate and sodium dodecyl sulfate, respectively.     

Thermal and Structural Study of Low Grade Graphite Ore From Shivaganga,India — Its Implications in Beneficiation Process

In this paper an attempt has been made to characterize the low grade calcareous graphite ore from Shivaganga region, India. By judicious combination of structural, thermal and chemical analytical techniques, the liberation size of graphite as well as estimation of minerals are determined to establish a feasible beneficiation process. This data show a good correlation. The ore consists of graphite, calcite and quartz as major minerals. The d-values and decomposition of calcite are found maximum at two size fractions i.e., +500 and below 90 microns. The TG and chemical analysis data on quantitative minerals estimation confirms that calcite significantly liberates below 90 micron size fraction and accounts for 60% calcite and 10% graphite minerals distribution. The DTA data show that calcite decomposes between 700–850°C and graphite starts combustion at 850°C. In view of this, to achieve calcite free graphite the ore needs to be calcined below 850°C and ground to 80% passing 75 micron size prior to flotation.This revised version was published online in November 2005 with corrections to the Cover Date.     

Influence of Calcium Sources on Microbially Induced Calcium Carbonate Precipitation by Bacillus sp. CR2

Stimulation of microbially induced calcium carbonate precipitation (MICCP) is likely to be influenced by calcium sources. In order to study such influences, we performed MICCP using Bacillus sp. CR2 in nutrient broth containing urea, supplemented with different calcium sources (calcium chloride, calcium oxide, calcium acetate and calcium nitrate). The experiment lasted 7 days, during which bacterial growth, urease activity, calcite production and pH were measured. Our results showed that calcium chloride is the better calcium source for MICCP process, since it provides higher urease activity and more calcite production. The influences of calcium sources on MICCP were further studied using Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. These analyses confirmed that the precipitate formed was CaCO₃ and composed of predominantly calcite crystals with a little amount of aragonite and vaterite crystals. The maximum yield of calcite precipitation was achievable with calcium chloride followed by calcium nitrate as a calcium source. The results of present study may be applicable to media preparation during efficient MICCP process.     

Study of the reaction mechanism and composition analysis of multiple-component mixed minerals DTA/T/EGD/GC on-line coupled simultaneous technique

An established DTA/T/EGD/GC on-line coupled simultaneous technique and relevant equipment were applied to identify the micro impurity minerals—pyrite and siderite in two kinds of dolomite in air and N₂. The proportional five-component mixed minerals (siderite, kaolinite, dolomite, calcite and quartz) and the proportional six-component mixed minerals (pyrite and the above five minerals) were detected in N₂ and in air/CO₂ (1∶1) separately by applying DTA/EGD/GC and DTA/GC. The experimental results provide the basis for demonstration of the reaction mechanism of thermal decomposition of various gas—solid-phase minerals in N₂ and air/CO₂. The compositions of six-component mixed minerals can be distinguished individually from the DTA/GC curves; reliable results are obtained.     

Effect of Fermentation Conditions on the Flocculation of Recombinant Saccharomyces cerevisiae Capable of Co-fermenting Glucose and Xylose

Flocculation is a desirable property in industrial yeasts and is particularly important in the fuel ethanol industry because it provides a simple and cost-free way to separate yeast cells from fermentation products. In the present study, the effect of pH and lignocellulose-derived sugars on yeast flocculation was investigated using a flocculent Saccharomyces cerevisiae, MA-R4, which has been recombinantly engineered to simultaneously co-ferment glucose and xylose to ethanol with high productivity. The flocculation level of MA-R4 dramatically decreased at pH values below 3.0 during co-fermentation of glucose and xylose. Sedimentation and microscopic observation revealed that flocculation was induced in MA-R4 when it fermented glucose, a glucose/xylose mixture, or mannose, whereas attempts to ferment xylose, galactose, and arabinose led to the loss of flocculation. MA-R4 fermented xylose and galactose more slowly than glucose and mannose. Therefore, the various flocculation behaviors shown by MA-R4 should be useful in the control of ethanol fermentation processes.     

Selective separation of arsenopyrite from pyrite by biomodulation in the presence of Acidithiobacillus ferrooxidans

Effective methods for selective separation using flotation or flocculation of arsenopyrite from pyrite by biomodulation using Acidithiobacillus ferrooxidans are presented here. Adhesion of the bacterium to the surface of arsenopyrite was very slow compared to that to pyrite, resulting in a difference in surface modification of the minerals subsequent to interaction with cells. The cells were able to effectively depress pyrite flotation in presence of collectors like potassium isopropyl xanthate and potassium amyl xanthate. On the other hand the flotability of arsenopyrite after conditioning with the cells was not significantly affected. The activation of pyrite by copper sulfate was reduced when the minerals were conditioned together, resulting in better selectivity. Selective separation could also be achieved by flocculation of biomodulated samples.     

Development of principles of selection of reagents for flotation of antimony and bismuth minerals

3D models of clusters of antimony and bismuth sulfides were constructed. For these models, the charges of individual atoms and the electron populations of s-Pop, p-Pop, and d-Pop orbitals were determined. Collector activity evaluation prediction (CAEP) was made for a number of proposed reagents attached to atoms of clusters of minerals. CAEP characterizes the activity of a collector: the lower CAEP, the more preferable the interaction of the collector and the more efficient the flotation reagent. For flotation of antimony and bismuth minerals, a number of promising collectors were recommended.     

Cationic flotation of quartz from an artificial mixture with hematite using hexylamine

The cationic flotation of quartz was carried out from an artificial mixture (1:1 by weight) of fine grained ( − 10 μm) quartz and hematite, using hexylamine acetate (HAA) and dodecylamine acetate (DAA) as collectors. Selective flotation of quartz was possible in the pH range 9–10 using HAA. The adsorption densities of DAA and HAA on quartz and hematite were measured at pH 9.8 and the relationship between the flotation behavior of both minerals and the surface coverage of collectors was established. Complete flotation of quartz and hematite required a surface coverage (θ) of DAA of about 100% at pH 9.8, while complete flotation of quartz took place at θ ⋍ 10% with HAA. The flotation behavior with DAA was explained by considering the adsorption of undissociated free amine. Zeta potential measurements were incorporated to interpret the difference in the adsorption behavior of both collectors on quartz and hematite.     

Performance of bio-mortar under elevated temperatures

The microbially induced calcite precipitation was used to bind sand grains, yielding consolidated material known as bio-mortar. An aerobic, urease-active and nonpathogenic Sporosarcina pasteurii microorganism was used for the induction of calcite precipitation. Three different temperatures (250, 500 and 750 °C) were applied to examine the firing resistivity of bio-mortar. The results showed that the organic fiber of died bacterial cells completely dissociates at 500 °C, causing a moderate compressive strength reduction and mass loss increment in bio-mortar. The exposure of bio-mortar to 750 °C leads to a significant compressive strength regression, due to the thermal decomposition of CaCO₃ as confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and differential thermal analysis (TG and DTA) as well as scanning electron microscopy.

     

煤中矿物质对灰熔融和燃烧特性的影响

采用化学分步萃取、XRD和SEM-EDS、煤灰灰成分分析等测试方法对五彩湾煤中矿物质的赋存形态进行了研究,并对逐级萃取前后煤样的燃烧特性和灰熔融特性进行了分析和比较.结果表明,五彩湾煤中原始矿物质主要有方解石、硫酸钙、高岭石、石英、黄铁矿等;煤中钠含量很高,主要以水合离子的形态溶于煤的内水中;有机形态的钠、镁和钙提高了煤的燃烧特性;五彩湾煤的煤灰熔融性主要受铁钙物质的量比(F₂O₃/CaO)影响,灰熔融特性温度随铁钙物质的量比(F₂O₃/CaO)的增大而降低.     

Adsorption mechanism of mixed cationic/anionic collectors in feldspar-quartz flotation system

The adsorption mechanism of mixed cationic alkyl diamine and anionic sulfonate/oleate collectors at acidic pH values was investigated on microcline and quartz minerals through Hallimond flotation, electrokinetic and diffuse reflectance FTIR studies. In the presence of anionic collectors, neither of the minerals responded to flotation but the diamine flotation of the minerals was observed to be pH and concentration dependent. The presence of sulfonate enhanced the diamine flotation of the minerals by its co-adsorption. The difference in surface charge between the minerals at pH 2 was found to be the basis for preferential feldspar flotation from quartz in mixed diamine/sulfonate collectors. The infrared spectra revealed no adsorption of sulfonate collector when used alone but displayed its co-adsorption as diamine-sulfonate complex when used with diamine. The presence of sulfonate increased the diamine adsorption due to a decrease in the electrostatic head-head repulsion between the adjacent surface ammonium ions and thereby increasing the lateral tail-tail hydrophobic bonds. The mole ratio of diamine/sulfonate was found to be an important factor in the orientation of alkyl chains and thus the flotation response of minerals. The increase in sulfonate concentration beyond diamine concentration leads to the formation of soluble 1:2 diamine-sulfonate complex or precipitate and the adsorption of these species decreased the flotation since the alkyl chains are in chaotical orientation with a conceivable number of head groups directing towards the solution phase.     

Adsorption of N-tallow 1,3-propanediamine-dioleate collector on albite and quartz minerals, and selective flotation of albite from greek stefania feldspar ore

The adsorption behavior of tallow 1,3-propanediamine-dioleate (Duomeen TDO) collector on albite and quartz minerals is assessed through Hallimond flotation, zeta potential, and diffuse reflectance FTIR investigations, together with the species distribution of the collector. The collector performance on albite separation from a natural feldspar material is evaluated in bench scale flotation tests. The Hallimond flotation responses of the minerals as a function of pH and collector concentration indicate that albite can be selectively floated from quartz at pH 2 where the doubly positively charged collector species adsorb on albite but not on quartz. However, the zeta potential and infrared spectra reveal that the adsorption behavior of the collector is similar on both minerals. The discrepancy in the flotation and adsorption results is attributed to the coarse and fine particle size fractions, and the shorter and longer equilibration periods employed in these studies respectively. The comparable adsorption on fine particles of albite and quartz at pH 2 is explained by the interaction of ammonium ions on silanol groups by hydrogen bonding as well as electrostatic interactions. The changes in zeta potentials are in good agreement with the formation of ionic species and free molecular forms of the collector. The IR spectra show the coexistence of neutral oleic acid together with charged amine species at low pH values in accordance with the species distribution diagram. Selective flotation of albite is accomplished from a natural feldspar material with tallow diamine-dioleate collector at pH 2 using sulfuric acid, only when the feed is deslimed prior to the bench scale flotation tests. An albite recovery exceeding 85% is achieved from a feed material containing about 50% albite.     

1,2,3-苯三氧基三乙酸的浮选抑制性能

抑制剂;1;2;3-苯三氧基三乙酸的浮选抑制性能     

The effect of pretreatment of calcite dispersions with anionic sodium polyacrylate on their flocculation behavior induced by cationic starch

The flocculation performance of cationic starches on calcite pretreated with anionic sodium polyacrylate (NaPA) was investigated by measuring the mean particle size and the dynamic mobility of the calcite dispersions. Cationic starches of different molecular weight and degree of substitution were used. By varying the amount of anionic sodium polyacrylate, which has a strong affinity to the calcium carbonate surface, one is able to anionically modify the particles and reverse the charge character of the originally cationic calcium carbonate. By such modification of the charge character of the calcium carbonate dispersion, it is possible to approach the mechanisms of flocculation caused by cationic macromolecules like starch. The importance of different mechanisms of flocculation, such as bridging, charge neutralization, and flocculation induced by polyelectrolyte complexes (PEC), was further investigated in this work. It was found that when the NaPA is completely absorbed at the calcite surfaces the mechanism of the flocculation induced by the starch is mainly bridging flocculation. Excess NaPA in the calcium carbonate dispersion will result in polyelectrolyte complexes formed between the non-absorbed NaPA and the oppositely charged starch polymers. These complexes will in most cases strongly enhance the flocculation due to mainly charge neutralization. Depending on the ratio of non-absorbed NaPA and the starch in the aqueous phase, the calcite dispersion is either re-stabilized or more strongly flocculated due to the formed polyelectrolyte complexes. Both the mobility and the particle size measurements support the mechanisms described. It was further demonstrated that the molecular weight and degree of substitution of the starches might be adjusted to control the flocculation behavior.     

Temperature and pressure effects on zeta potential values of reservoir minerals

An experimental study of the effect of temperature and pressure on zeta potential of typical reservoir minerals, including quartz, kaolinite, and calcite, is presented. Experiments included the design and construction of an electrophoretic cell for zeta potential measurements at variable pressure and temperature. Electrolyte concentration was varied in the range from 0.0001 to 0.1 M in the pH range from 2 to 9. For all the minerals it is found that the zeta potential decreases with temperature at a rate characteristic of each mineral; values are around -2.3 mV/degrees C for quartz, -0.96 mV/degrees C for kaolinite, and -2.1 mV/degrees C for calcite for pressure values less than 45 psi. The effect of pressure is found to depend on the mineral nature and pH of the electrolytic solution. In the case of quartz, a systematic increase in the value of the zeta potential with pressure is observed, whereas a decreasing trend is measured for the kaolinite. In the case of calcite, a decreasing trend is observed for pressures up to 45 psi, whereas the experimental data suggest an increasing trend for higher pressure values.     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

Particle size distribution of mineral phases and metals in dusts collected at different workplaces

Summary Airborne dusts were collected by a two-stage sampler on an electrically activated filter at different working places. Inhalable size (particles are less than 5 m) and course fractions were separated by a cyclone. The particle size distribution of three minerals (quartz, calcite, albite) and four metals (Pb, Cd, Cr, Co) was determined. Infrared spectroscopic and AAS methods were applied. The quartz concentrated in the course fractions while the calcite in the inhalable ones. No direct relation to the size fractions was found for albite. The toxic metals were extremely enriched in the fine fractions, in some cases 5–12 times more than in the course fractions. Since only the fine particles might be deposited in the deepest parts of the lung the importance of elimination of pollution sources should be taken into account.