Gemini trisiloxane surfactant: Synthesis and flotation of aluminosilicate minerals

In this paper, an amino-trisiloxane Gemini cationic surfactant, butane-1,4-bis(dimethyl-(3-(3-aminopropyl trisiloxane-3-yl)-propyl)-ammonium bromide) (BBAB) was prepared, and its flotation potential was assessed on kaolinite, pyrophyllite and illite minerals. The flotation results showed that changes to the pulp pH did not significantly influence BBAB’s collecting power in floating three aluminosilicate minerals. In addition, BBAB was a stronger collector than the conventional monomeric surfactant dedecyl trimethylammonium bromide (DTAB) or dodecylamine (DDA). The results of FTIR spectra, zeta potential measurements and density functional theory (DFT) calculations indicated that the interaction of BBAB with the three aluminosilicates was mainly through electrostatic attraction. BBAB’s unique properties, such as high positive grouping Mulliken charge of –CH₂N⁺(CH₃)₂(CH₂)₄(CH₃)₂N⁺CH₂–, and “parachute” shape structure of [(CH₃)₃SiO]₂SiCH₃, resulted in superior collecting powers for the aluminosilicate minerals.     

某含碳铜钨锡多金属矿选矿试验研究

针对Cu品位0.91%、WO_3品位0.25%、Sn品位为0.21%的某含碳铜钨锡多金属矿,采用优先浮铜工艺流程,通过闭路试验获得了产率为3.22%,Cu品位为25.11%、Cu回收率为89.16%的铜精矿;浮铜尾矿采用浮选脱硫-重选-强磁分离工艺流程回收锡、钨矿物,获得了WO_3品位为46.05%、Sn含量为3.80%、WO_3回收率为42.46%的黑钨精矿和Sn品位为58.03%、WO_3含量为6.25%、Sn回收率为42.07%的非磁精矿。与现场生产指标相比,铜精矿Cu品位提高了8.11个百分点;WO_3综合回收率提高了5.49个百分点,Sn回收率提高了4.07个百分点。     

Effects of sodium tripolyphosphate and sodium carbonate on the selective flocculation of diasporic-bauxite in the presence of calcium and magnesium ions

In this study, sedimentation tests for individual minerals and artificially mixed minerals and bauxite ores were carried out to understand the effects of sodium tripolyphosphate (STPP) on the selective flocculation of diasporic-bauxite in the presence of Ca²⁺ and Mg²⁺ ions. It was found that STPP can mitigate the detrimental effects of Ca²⁺ and Mg²⁺ ions on the dispersion of diaspore and kaolinite. When separating bauxite from the mixtures of minerals and in the presence of Ca²⁺ ions, STPP can serve as better dispersant than sodium carbonate. By jointly using STPP as a dispersant and PAAS as a flocculant, a flocculation concentrate with the mass ratio of Al₂O₃/SiO₂ (Al/Si) of 7.14 and Al₂O₃ recovery of 89.97% was produced from the feed (Al₂O₃/SiO₂ = 5.64) in the presence of Ca²⁺ ions. In contrast, with using sodium carbonate as the dispersant and PAAS as the flocculant, selectivity of the flocculation separation of diasporic-bauxite was deteriorated. These experimental data were satisfactorily interpreted by some chemical reactions occurring in the pulp, which were deduced from measured zeta potentials of the reaction resultant products and residual Ca²⁺ concentrations of the pulp.     

Mineral carbonation of PGM mine tailings for CO2 storage in South Africa: A case study

The ultra-fine milled tailings generated during the processing of PGM ores in South Africa have a theoretical potential to sequester significant amounts of CO₂ (∼14 Mt per annum) through mineral carbonation. Mg-bearing orthopyroxene is the major sequestrable mineral in these tailings, which also contains significant quantities of Ca-bearing plagioclase, as well as minor quantities of clinopyroxene, olivine, serpentine and hornblende. In this study, the feasibility of using PGM tailings to sequester CO₂ has been investigated empirically using the two-step, pH swing method. The rates and extents of cation (Ca, Mg and Fe) extraction and subsequent carbonation were determined and compared. Both organic (oxalic and EDTA) and HCl solutions were utilised in the cation extraction step, which was conducted at time periods up to 8 h and at a temperature of 70 °C. The extents of cation dissolution were relatively low under all experimental conditions investigated, particularly for the case of Mg (between 3.3% and 5.0% extraction). A comparison of the extents of leaching with the mineralogical composition of the tailings indicated that the extracted Mg originated primarily from clinopyroxene, with the orthopyroxene remaining relatively inert under the experimental conditions. Subsequent carbonation of the acid leach solution after pH adjustment with NaOH resulted in the rapid formation of a number of carbonate minerals, including gaylussite (Na₂Ca(CO₃)₂·5(H₂O)), magnesite (MgCO₃), hydromagnesite (Mg₅(CO₃)₄(OH)₂·4H₂O), dolomite (CaMg(CO₃)₂), ankerite (Ca(Fe,Mg)(CO₃)₂), and siderite (FeCO₃). On the basis of these findings, further studies will be focused on developing a better understanding of the factors affecting the dissolution of Mg-bearing orthopyroxene minerals, and on exploring alternative leach reagents and conditions, with a view to developing a more effective process for the accelerated carbonation of PGM tailings.     

The influence of pyrite pre-oxidation on gold recovery by cyanidation

The influence of pyrite pre-oxidation in alkaline solutions on gold recovery by cyanidation from Twin Creek refractory gold ore in which pyrite was identified as the major sulfide mineral has been investigated with the aid of electrochemical measurements, leaching experiments, and direct analysis of reaction products for selected residues. It was found that gold recovery by cyanidation in bottle roll experiments mainly depended on the extent of pyrite pre-oxidation. The rate of pyrite oxidation in alkaline solutions measured by electrochemical measurements, including chronoamperometry and linear sweep voltammetry, increased with an increase in pH, potential, and temperature. All alkaline reagents used for the electrochemical measurements, NaOH, NH₄OH, Na₂CO₃ and Ca(OH)₂, showed a similar effect on pyrite oxidation kinetics. However, the results of alkaline pre-oxidation for pyrite of the Twin Creek refractory gold ore suggested that NaOH and Na₂CO₃/Ca(OH)₂ were superior to Ca(OH)₂. Without pre-oxidation, cyanide leachable gold was found to be only 20% which could be increased to 70% under appropriate pre-oxidation conditions. At the same time, cyanide consumption decreased from 2.5 kg/t ore to 1.5 kg/t ore.Selected residues after pre-oxidation and cyanidation were examined by X-ray diffraction. Backscattered electron images of pyrite particles in these residues were taken. The reaction products at the surface of pyrite particles were found to be iron-, silicon-, and calcium-bearing compounds with variable amounts of sulfur as determined by X-ray energy dispersion analysis. Additionally, some mineral fines, such as aluminum and/or potassium-bearing minerals, were found to be present at the partially oxidized pyrite surface.     

Phosphate coating on pyrite to prevent acid mine drainage

Abstract

Acid mine drainage (AMD) is a serious environmental problem that preoccupies the Canadian Mineral Industry. Considerable amounts of money are spent every year in an effort to prevent or reduce the acid mine drainage phenomenon. AMD occurs when sulfide minerals (ex. pyrite) contained in rock are exposed to air and water and subsequently oxidize to produce low pH water. This acid effluent has the potential to mobilize any heavy metals contained in the rock. Coating the sulfide minerals with iron phosphate is a new promising technology to reduce AMD.Pyrite is treated with a solution containing H₂O₂, KH₂PO₄ and sodium acetate (NaAc). H₂O₂ oxidizes a small part of pyrite producing ferric iron (Fe³⁺) anions. These cations subsequently react with the PO₄ ^3? anions to produce FePO₄ that precipitates on the pyrite surface producing a passive coating. This iron phosphate coating can protect the grains of pyrite from oxidation. This paper presents a series of experiments that confirm that iron phosphate coating can considerably reduce AMD.     

Mechanism of adsorption of sodium dodecylsulfonate on celestite and calcite

The surface properties of celestite (SrSO₄) and calcite (CaC0₃) in aqueous solutions of the anionic collector sodium dodecylsulfonate (NaDDS0₃) have been investigated making use of zeta potential, adsorption, infrared spectroscopy and microflotation techniques. A range of pH (3 to 11) and surfactant concentration (10⁻⁶ to 10⁻³ M) were tested. The experiments were performed at a constant temperature (25°C) and using regulated suspensions. The zeta potential studies showed that the isoelectric point (IEP) of celestite and calcite took place at pH 3 and 8, respectively. In the presence of dodecylsulfonate ion the IEP of both minerals shifted to lower pH values. The adsorption isotherms obtained for both minerals showed marginal adsorption up to certain surfactant concentration and precipitation of the salt (strontium or calcium dodecylsulfonate) onto the mineral surface beyond such a concentration. The microflotation studies showed that celestite was activated even at pH values where its surface was negatively charged. Compared to celestite, the activation of calcite was lower. It is suggested that the dodecylsulfonate ion adsorbed on the surface of celestite and calcite by a chemisorption mechanism giving rise, under certain circumstances, to the formation of the corresponding salt at the mineral-water interface.     

Biodestruction and deferritization of quartz sands by Bacillus species

Quartz sand containing mineral impurities was subjected to bioleaching with Bacillus spp. strains and subsequent elutriation. Bioleaching of the sample removed visible Fe-bearing minerals that coated quartz grains. During the bioleaching, elements were dissolved from silicate minerals. Poorly crystalline Fe-oxides that sealed siderite nodules were released from intergranular spaces and formed a fine-grained (<0.1 mm) fraction. Voltammetry of the fine-grained fraction indicated reductive dissolution of Fe³⁺. However, chemical analysis showed a slight increase in Fe₂O₃ content and a decrease in the FeO content following three months bioleaching in the Bacillus culture. X-ray diffraction analyses showed the loss of Fe-bearing minerals and mica following the bioleaching and the elutriation of the fine-grained fraction. Transmission electron microscopy and energy-dispersive analysis of X-rays showed nucleation of fine-grained Fe,Al-silicates on bacterial surface after three months of bioleaching.     

全球大宗矿产资源贸易格局演变及其影响因素初探

中国经济发展已经步入工业化中后期,经济发展增速趋缓,对矿产资源需求也开始逐渐步入峰值区,但中国仍需要消费大量的矿产资源完成本国工业化。随着国内生态文明建设的推进,国内矿产资源的供应将一定程度的受到影响,为此,对国际贸易的依赖将会逐渐增加。本文以铁、铜、铝、铅、锌、锰为例,基于复杂网络模型,对1997-2016年全球大宗矿产资源贸易格局演变进行分析,并对其影响因素进行初步探讨。通过分析得出：不同贸易矿产品之间的显著影响因素是不同的,需进行针对性分析；出口集中度的增加,会使得大宗矿产资源的贸易繁荣程度受到不同程度的抑制；中国国际地位上升,对于大宗矿产的国际贸易存在一定的相关性,但并不能主导大宗矿产国际贸易流向。研究成果可为我国走出去,参与全球资源配置,制定相关战略提供参考。     

某铅锌矿综合回收工艺技术

为了实现西藏某铅锌复杂难选矿石的铅、锌和硫的高效分离,采用优先浮选工艺流程对矿样的有用组分进行条件实验,以矿磨细度-74 μm 80％,采用乙硫氮+丁铵黑药为捕收剂,适量石灰+硫化钠硫酸锌为活化剂,浮选时间在4.5 min后,取得了满意的铅产品作业回收率;对铅的浮选尾矿以石灰作为(磁)黄铁矿的抑制剂及pH值调整剂,硫酸铜为活化剂,丁黄药为捕收剂,浮选达到了较高的锌产品回收率;硫粗选实验采用硫酸作为活化剂,丁黄药作为捕收剂获得了满意的硫产品回收率.该实验可获得铅精矿Pb回收率90.09％;锌精矿Zn回收率80.58％;硫精矿S回收率47.49％.从最终精矿产品可以看出,采用铅中矿顺序返回-锌全浮选-锌精矿磁选工艺可获得较好的铅、锌、硫等精矿指标.     

Stability of Coatings on Sulfide Minerals in Acidic and Low-Temperature Environments

The effectiveness of silicate- and phosphate-based surface coating agents (Na₂SiO₃, CaSiO₃, and KH₂PO₄) in inhibiting the oxidation of sulfide minerals in acidic and low temperature conditions was studied. Rock samples were coated using two oxidation methods: H₂O₂ was mixed with the coating agents in one, whereas in the second, H₂O₂ was applied to the rock surface prior to the coating agent. The second approach was ineffective, but with Method 1, the pH (5) was above the pH (3.6) of the uncoated control sample. Oxidation, calculated after 14 weeks, had been suppressed by up to 96 and 65%, as indicated by the release of Fe²⁺ and SO₄ ^2?, respectively. All three coating agents (at concentrations of 0.1 and 0.3 M) suppressed the release of Fe²⁺ (<3 mg L^??1). Na₂SiO₃ inhibited Fe²⁺ and SO₄ ^2? release by 94 and 65%, respectively. Surface protection (or oxidation inhibition) efficiencies of KH₂PO₄ (in terms of Fe²⁺ release) were 67, 94, and 96% with 0.05, 0.1, and 0.3 M, respectively. The Na₂SiO₃ and CaSiO₃ coatings, irrespective of their concentrations, reduced iron oxidation by 94 and 84%, respectively. Fourier transform infrared spectroscopy analysis of the Na₂SiO₃ treated samples showed the presence of iron silicate coatings. Based on this work, coating of rock samples with silicate or phosphate can reduce the oxidation rate of sulfide minerals in acidic and low temperature conditions.     

胺类捕收剂在铁精矿脱硅反浮选中的作用机制

从理论上分析了铁精矿和硅质矿物的表面电性与矿浆pH的关系,以及胺类捕收剂在矿浆中的水解行为。在此基础上,通过试验研究了胺类捕收剂在铁精矿脱硅反浮选过程中的作用机制。结果表明：强碱性条件下,胺类捕收剂主要以RNH₂形式存在,不能有效地与硅质矿物作用,达不到降硅的目的;酸性过强时,矿浆中胺阳离子（RNH⁺₃）浓度过高,胺阳离子之间通过氢键相互作用,减少甚至失去与矿物颗粒的吸附作用,同样不能取得好的分选效果。因此,铁精矿反浮选脱硅时,应根据矿石性质控制pH值,使矿浆中保持适当的胺阳离子浓度。铁精矿|脱硅     

Electrochemical interactions of industrially important platinum-containing minerals

Pt–Te₂ and Pt–Bi–Te are two important platinum-carrying minerals typically found in altered platinum reserves. Mineralogical studies indicate the Pt–Pd–Bi–Te class to react poorly on the flotation stimuli and indications are that these minerals are slow floaters. This paper investigates the fundamental interactions of potassium ethyl xanthate with these minerals by employing electrochemically controlled contact angle measurements, FT-IR spectroscopy and voltammetry. The electrochemical investigations revealed that Pt–Te₂ is more noble than Pt–Bi–Te at potentials lower than 300 mV (SHE) in sodium tetraborate buffer solution and the reduction peak observed during the return sweep of Pt–Bi–Te is mainly associated with the reduction of bismuth oxidation products. Both the minerals show increased anodic currents when polarised at 0.3 V (SHE) in a 0.05 M Na₂B₄O₇ solution containing 1 × 10⁻³ M potassium ethyl xanthate. According to the results of the rest potential measurements, formation of dixanthogen should be thermodynamically favourable and the very high rest potentials are attributed to the catalytic effect of platinum on the oxygen reduction reaction. The formation of dixanthogen on both the minerals was confirmed by ex situ FT-IR spectroscopy. Contact angle measurements revealed the surface of Pt–Bi–Te to be hydrophobic in nature whereas small contact angles were realized on Pt–Te₂. Surface roughness of the mineral could be responsible for these small contact angles.     

Mineral conductivity measurements

Unlike insulating minerals, such as quartz or feldspar, the propensity of conductive minerals to heat using radiofrequency energy has not been particularly well quantified or documented in scholarly literature. A detailed knowledge of the RF properties of all minerals is required for RF energy to be effectively used in many potential applications. Electrical conductivity measurements were performed on selected sulphide minerals and magnetite between 100 kHz and 10 MHz using thin-film electrodes. However, reproducible measurements are challenging due both the high conductivity and semiconducting nature of the minerals. These measurements show variation between deposits and allude to favourable differences difference between minerals at radiofrequencies.     

承德地区某超贫钒钛磁铁矿干抛尾矿磷回收试验研究

以承德地区某钒钛磁铁矿干抛尾矿为研究对象,采用浮选方法,系统研究干抛尾矿磨矿细度、充气量、抑制剂用量、pH值、捕收剂用量、粗选时间对磷浮选效果的影响。结果表明,干抛尾矿在磨矿细度为-0.074 mm占55%条件下,以水玻璃为抑制剂、DB-1为捕收剂、经过"一次粗选、两次精选、两次扫选"的浮选闭路试验,可以获得磷精矿产率为2.35%、P_2O_5品位为38.34%,P_2O_5回收率为91.94%的浮选指标,实现了该干抛尾矿中磷的高效回收。     

Fracture toughness and surface energies of minerals: theoretical estimates for oxides, sulphides, silicates and halides

Theoretical estimates of the ideal fracture toughness and surface energies of 48 minerals have been modelled by treating them as ionic solids, using the Born model of bonding. Development of the toughness model required calculation of the crystal binding enthalpy from thermodynamic data and the use of published elastic constants for single crystals. The principal minerals studied were oxides, sulphides and silicates, plus a few halides and sulphates. The study showed grain boundary fracture is most likely in single-phase polycrystalline minerals. However, the fracture toughness for grain boundary cracking in pure minerals is not significantly lower than that for intragranular cracking. The computed critical stress intensity values for intragranular cracking, K_IC, ranged from 0.131 to 2.774 MPa m^1/2. The critical energy release rates for intragranular cracking, , ranged from 0.676 to 20.75 J m⁻². The results are discussed with relevance to mineral comminution, including energy considerations, particle impact efficiency, and lower limiting particle size.     

Surface properties of enargite in MAA depressant solutions

Enargite (Cu₃AsS₄) is a common penalty mineral in the copper mining industry. Different treatment methods have been proposed to passivate the enargite surface for effective flotation of non-arsenic copper minerals, including pulp potential control, pre-oxidation and chemical depression. Magnesium ammonium mixture (MAA) has been previously tested, showing good selectivity for arsenic rejection. It was hypothesised that MAA would make the enargite surface hydrophilic by adsorption of magnesium ammonium arsenate hexahydrate (MgNH₄AsO₄·6H₂O). Here we show that MAA does not selectively adsorb onto the enargite surface as conjectured. X-ray photoelectron spectroscopy and cyclic voltammetry show that magnesium compounds do not precipitate onto the enargite surface at pH 10, whereas magnesium hydroxide on the enargite surface is formed at pH 12. MgNH₄AsO₄·6H₂O was not observed at either pH 10 or pH 12. The effect of pre-oxidation to promote dissolution of (AsO₄)³⁻ before conditioning with MAA, which could help catalyse the formation of MgNH₄AsO₄·6H₂O, was also tested. However, the results were the same as those without pre-oxidising the sample. Our investigation shows that under alkaline conditions it is not possible to passivate the enargite surface in MAA solutions for effective flotation of non-arsenic copper minerals.     

从某铜矿尾矿中重选回收白钨矿的试验研究

某铜矿浮选尾矿WO_3品位为0.056%,可供综合回收。该尾矿矿物组分较复杂,其中钨矿物绝大部分为白钨矿,另有微量的黑钨矿及钨华,金属硫化矿物主要为黄铁矿,微量磁黄铁矿,其他金属矿物主要为褐铁矿、磁铁矿等,非金属矿物主要为石英,其次为钙铁榴石,少量的方解石、长石、绿泥石等。白钨矿可浮性较好,可以采用浮选方法回收,但浮选药剂在回水中残留会显著影响主流程主要金属的浮选指标,而重选流程不会影响回水复用。采用浮选开路试验脱硫后,再通过螺旋溜槽分级富集-磁选除杂-摇床回收粗粒级白钨矿-异形面溜槽回收微细粒级白钨矿,全流程试验获得了产率为0.05%,WO_3品位为30.11%,WO_3回收率为26.41%的钨精矿。     

Geochemistry of Perched Water in an Abandoned Underground Mine, Butte, Montana

Abstract.  The Lexington tunnel is the last accessible underground mine working in the Butte, Montana mining district. Used as recently as 1993, the tunnel and adjacent workings have been abandoned for over 10 years. Although the Lexington tunnel is over 200 m above the regional water table, perched water is present over much of its extent. Mine water near the portal is moderately acidic (pH 4 to 5), with extremely high concentrations of metals, including Cu (up to 1000 mg/L) and Zn (up to 1400 mg/L). In the middle reaches of the tunnel, the quality of the water is much better, with near-neutral pH, high bicarbonate alkalinity, and lower concentrations of heavy metals. The low acidity and metal content is attributed to a lack of pyrite and other sulfides in this portion of the mine, as well as the presence of carbonate minerals, such as rhodochrosite (MnCO₃), in exposed veins. Sulfide minerals are more widespread further back in the tunnel, and are now oxidizing rapidly, leading to pockets of severe acid drainage (pH< 3, dissolved Zn up to 5000 mg/L). Geochemical modeling suggests that the near-neutral waters—the most voluminous type encountered in the Lexington tunnel—are close to equilibrium saturation with rhodochrosite and hydrous Zn-carbonate (ZnCO₃•H₂O). The Eh of these waters is most likely controlled by redox reactions involving dissolved Mn²⁺ and secondary, Zn-rich, hydrous Mn-oxides. In contrast, the Eh of the acidic waters appears to be controlled by reactions involving Fe²⁺ and Fe³⁺. Most of the acidic waters are saturated with K-jarosite, which forms delicate, straw-like dripstones at several localities. Decaying mine timbers could be an important renewable source of organic carbon for heterotrophic microorganisms, such as iron- and sulfate-reducing bacteria, especially deeper in the mine workings where the ground is saturated with anoxic ground water.     

Calcium ion effects in amine flotation of quartz and magnetite

The flotation of quartz and magnetite was studied as a function of pH when using N-alkyl-1, 3 diaminopropanes as collectors in the presence of Ca(II). The alkyl chains of the diamines were 8, 12 and 16 carbons in length. Two collector concentrations were used and flotation studied in the absence of additives and in the presence of CaCl₂. All the amines are relatively stronger collectors for quartz than for magnetite in both the absence and presence of CaCl₂, in the concentration studied, 0.1 mol/dm³, functions as a depressant for the minerals. Probable surface chemical phenomena giving rise to the observed experimental results are discussed.