Interactive effects of the type of milling media and copper sulphate addition on the flotation performance of sulphide minerals from Merensky ore Part I: Pulp chemistry

It is well known that the chemical environment determines the success of the flotation process, however its characterisation and control is difficult to achieve. This paper, as two parts, Part I and Part II, evaluates the use of various measurements and their interpretation to gain an understanding of the influence of varying parameters such as the type of milling media and copper sulphate addition on the flotation performance of sulphide minerals from a platinum group mineral (PGM) bearing Merensky ore. It shows the complexity of interpretation and the importance of analysing flotation performance holistically. Part I focuses on the pulp chemistry and mineral potential measurements have been used to show the differences in the response of the various mineral electrodes to different conditions. The final flotation recoveries of the sulphide minerals in the ore followed the same trend as the decrease in mineral potential due to collector addition viz. chalcopyrite > pentlandite > pyrrhotite. Type of milling media and copper sulphate addition slightly affected the mineral electrode potential and flotation recovery of chalcopyrite. Addition of copper sulphate increased the recovery of pentlandite and particularly pyrrhotite due to activation by copper (II) ions. The copper activation mechanism was likely to be in the form of initial adsorption of copper hydroxide followed by reduction to Cu⁺ at the surface. However, the changes in flotation performance of the different minerals in the ore could not be completely described by the electrochemical changes, demonstrating the limitations of these measurements. Part II addresses the effect of froth stability as demonstrated by the variations in the mass and water recovery data resulting from the different milling conditions and addition of copper sulphate which emphasised the importance of considering the froth phase in the evaluation of flotation data.     

Optimisation of operating variables of fine coal flotation using a combination of modified flotation parameters and statistical techniques

Optimisation of flotation parameters using rate models is not a new concept. The kinetic model based on time recovery data, which uses the extra dimension of rate, has been in vogue since time immemorial for scaling up of lab data. Often, interpretation on the performance of a flotation circuit, based only on R_∞ (the ultimate recovery) and k_s (the first-order rate constant of the component) may lead to wrong conclusions. In such cases, a modified flotation rate constant k_mod defined as the product of R_∞ and k_s, i.e., k_mod=R_∞k_s and selectivity index (SI), defined as the ratio of the modified rate constant of valuables to the modified rate constant of gangue, can be used. An attempt has been made in this paper to optimize the batch laboratory froth flotation parameters of fine coal using the above two concepts, i.e., k_mod and SI and statistical techniques.A flotation bank containing four Outukumpu cells was optimized using the results obtained from the lab study. The airflow number and the froth number were used as a basis for scale up. To gauge the performance of the froth flotation circuit, an efficiency parameter called the coefficient of separation or the CS was used. The yield from the flotation circuit improved, the froth ash reduced and the rejects ash went up.     

The selective flotation of enargite from other copper minerals — a single mineral study in relation to beneficiation of the Tampakan deposit in the Philippines

The floatability of enargite (3Cu₂S.As₂S₅) has been determined as a function of pulp potential to establish whether the flotation behaviour of the mineral differs sufficiently from that of other copper minerals thus offering the prospect of rejecting arsenic from the Tampakan ore by potential control during flotation.     

The effect of hydrodynamic conditions on true flotation and entrainment in flotation of a complex sulphide ore

The separation efficiency and selectivity of flotation are directly proportional to recoveries of the mineral species in the feed due to true flotation and entrainment. In this study, effects of the hydrodynamic conditions on true flotation and entrainment were investigated by using a fractional factorial experimental design. A method previously described in the literature was applied to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore. In order to apply the method, the kinetic flotation tests were conducted under various hydrodynamic conditions defined by some physical variables. Some of these tests were conducted in the presence and absence of a collector to evaluate the self-induced floatability. The selectivity index of the mineral species for entrainment was seen to be suitable evaluation of the non-selectivity and efficiency of the entrainment. Furthermore, the results of the size-by-size analysis of the froth products indicated that the presence of the self-induced hydrophobic particles in the feed is as important as the presence of very fine particles for accurate estimation of true flotation and entrainment in flotation of a complex sulphide ore. In addition, the estimated results for entrainment in flotation of the complex sulphide ore can be misleading. Therefore, a new approach would be necessary to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore.     

Effect of oxidation potential and zinc sulphate on the separation of chalcopyrite from pyrite

The effects of oxidation potential (Eh) and zinc sulphate on the separation of chalcopyrite from pyrite were investigated at pH 9.0. The flotation recovery of these minerals is Eh dependent with maximum separation obtained at 275 mV SHE. Zinc sulphate addition improved this mineral separation at an Eh value of 275 mV by selectively depressing pyrite flotation. A different result was obtained at lower Eh values where zinc sulphate addition improved chalcopyrite flotation but had no or little effect on pyrite flotation. These opposite effects of zinc sulphate on mineral flotation were reconciled by examining the surface species of these minerals. The selective depression of pyrite flotation by zinc sulphate was also confirmed in the flotation of two copper ores.     

Mineral processing and extraction of rare earth elements from the Wadi Khamal Nelsonite Ore, Northwestern Saudi Arabia

A technological sample (50 kg) from Wadi Khamal Nelsonite ore was subjected to magnetic and flotation concentration techniques. Excellent recovery percentages of 72.95% and 71.22% were achieved by the dry/wet magnetic and flotation concentration techniques, respectively. The weight of the apatite concentrate reached a reasonable percentage of approximately 23.5% with an overall 40.23% P₂O₅ total content. Analytical data of the apatite concentrate after digestion in concentrated sulfuric acid revealed that the total content of the rare earth elements (REE) constitutes about 0.2% of the total apatite content. The REE content (0.2%) was partitioned between phosphoric acid liquor (65%) and gypsum precipitate (36%). The extraction of the REEs from the phosphoric acid liquor using oxalic acid and sodium carbonate–bicarbonate mixture (1:10?w/w) yielded the RE oxide cake which constitute about 1.2% (w/w). The produced rare earth oxide cake contains traces of various metal oxides, e.g., SrO, Na₂O, etc. in addition to rare earth oxides. Attempts to determine quantitatively the constituents of the cake will be considered in future work.     

Removal of lead minerals from copper industrial flotation concentrates by xanthate flotation in the presence of dextrin

Potato starch and dextrins resulting from thermolysis of potato starch in the absence of reagents and presence of -amino acids are promising depressants for separation of lead and copper minerals present in the Polish industrial copper concentrates. The polysaccharides were used for differential xanthate flotation of the final industrial concentrates produced by flotation with sulfhydryl collectors in the absence of depressants. The polysaccharides depressed galena and provided froth concentrate rich in chalcocite and other copper minerals as well as cell product containing lead minerals. The best results of separation were obtained in the presence of plain dextrin prepared by a thermal degradation of potato starch. The industrial concentrate containing 18.5% Cu and 5.5% Pb was divided into a froth product containing 38.1% Cu with 77% recovery of copper and a cell product assaying 7.3% Pb with 83% recovery of lead. It was accomplished using 2500 g/t of dextrin, 50g/t of potassium ethyl xanthate, and 50 g/t of frother (α-terpineol). The pH of flotation was 8.0–8.2.     

Sulphur isotopic fractionation between sulphate and sulphide in hydrothermal ore deposits: disequilibrium vs equilibrium processes

Correlative fractionation relationships of sulphur isotope data for coexisting sulphate and sulphide pairs from hydrothermal ore deposits on δ³⁸S versus Δ³⁴S diagrams are deciphered theoretically. Taking into account dissolved H₂S and SO₄^2- in hydrothermal fluids during precipitation of both sulphate and sulphide minerals, a 4-species closed system is suggested for describing the conservation of mass among all sulphur-bearing species on the δ-Δ diagrams. The covariation in the δ³⁴S values of both sulphate and sulphide is ascribed to isotopic exchange between oxidized and reduced sulphur species during mineral precipitation. The isotopic exchange could be a thermodynamic process due to simple cooling of high temperature fluids, which results in an equilibrium fractionation, or a kinetic process due to mixing of two sulphur reservoirs, which leads to a disequilibrium fractionation. The δ³⁴S value of total sulphur in a hydrothermal system could change due to the precipitation of minerals, or due to the escape of H₂S and/or SO₄^2-. Sulphur isotope data for anhydrite and pyrite pairs from the Luohe porphyrite iron deposit in the Yangtze River Valley is used to illustrate the mixing responsible for the disequilibrium fractionation.     

Pressure fluctuations and the formation of the PGE-rich Merensky and chromitite reefs, Bushveld Complex

The Merensky Reef and the underlying Upper Group 2 chromitite layer, in the Critical Zone of the Bushveld Complex, host much of the world’s platinum-group element (PGE) mineralization. The genesis is still debated. A number of features of the Merensky Reef are not consistent with the hypotheses involving mixing of magmas. Uniform mixing between two magmas over an area of 150 by 300 km and a thickness of 3–30 km seems implausible. The Merensky Reef occurs at the interval where Main Zone magma is added, but the relative proportions of the PGE in the Merensky Reef are comparable to those of the Critical Zone magma. Mineral and isotopic evidence in certain profiles through the Merensky Unit suggest either mixing of minerals, not magmas, and in one case, the lack of any chemical evidence for the presence of the second magma. The absence of cumulus sulphides immediately above the Merensky Reef is not predicted by this model. An alternative model is proposed here that depends upon pressure changes, not chemical processes, to produce the mineralization in chromite-rich and sulphide-rich reefs. Magma was added at these levels, but did not mix. This addition caused a temporary increase in the pressure in the extant Critical Zone magma. Immiscible sulphide liquid and/or chromite formed. Sinking sulphide liquid and/or chromite scavenged PGE (as clusters, nanoparticles or platinum-group minerals) from the magma and accumulated at the floor. Rupturing of the roof resulted in a pressure decrease and a return to sulphur-undersaturation of the magma.     

Collectorless flotation of chalcopyrite and sphalerite ores by using sodium sulfide

The flotation of chalcopyrite and sphalerite from copper and copper-zinc ores has been achieved without using thiol-type collectors. Typically, a sulfide ore sample is first treated with sodium sulfide either during grinding or during the preflotation conditioning period, and then the chalcopyrite is floated with frother alone. With a copper-zinc ore, sphalerite is subsequently floated from the chalcopyrite tailings by activating it with copper sulphate. Results of the collectorless flotation tests are comparable to those obtained by using thiol collectors. The mechanisms of selective collectorless flotation are discussed on the basis of differences in the solubilities of sulfide minerals.     

河南省禹州方山矿区高钾铝土矿的地质特征

禹州方山铝土矿是河南省已知铝土矿勘查区中含钾量最高的一个矿区。方山高钾铝土矿赋存于石炭系上统本溪组中,硬质黏土是构成高钾铝土矿的主体,高钾铝土矿层最厚79.47m,最薄1.98m,平均18.78m;主要含铝矿物为一水硬铝石,高钾铝土矿的化学成分与铝土矿基本相同,全矿区w(K2O)的平均值为3.75%,最高10.16%,最低0.04%。矿区很少有云母等含钾矿物的存在,高钾铝土矿中的K2O不完全来源于含钾矿物,也非矿区内仅存交换吸附阳离子能力最低的高岭石所致,况且方山铝土矿周边的寒武系张夏组水泥灰岩中w(K2O)<2%,在方山地段含铝岩系中能形成w(K2O)超过10%的地层实属罕见,方山铝土矿中K2O的来源尚需进一步研究。     

Surface chemical mechanisms of inadvertent recovery of chromite in UG2 ore flotation: Residual layer identification using statistical ToF-SIMS analysis

In the UG2 ore (Bushveld Complex, South Africa) flotation, normally more than 3% of the gangue minerals, principally chromite with talc and pyroxene, report to the concentrate diluting the PGM recovery and contributing to subsequent processing costs. Previous studies have identified residual talc-like layers on orthopyroxene surfaces in Merensky ore flotation contributing to inadvertent flotation of relatively large particles (20–150 µm) of this mineral. Chromite (75–150 µm) from flotation of UG2 ore has been similarly examined. Statistical comparison of ToF-SIMS analysis of particles from concentrate and tails reveals no significant difference in Cu, Pb, Ni and collector (IBX and DTP) signals between these streams but surface exposure of Mg and Si is favoured in the concentrate. The flotation rate of coarse chromite correlates with the exposures of magnesium and silicon in patches on the chromite surface; higher exposures give earlier flotation. Conversely, there is a negative correlation with signals corresponding to the chromite surface, i.e. Cr, Fe, Al. Flotation of chromite without collector has confirmed this statistical discrimination. Hydrophobic talc-like residual layers, similar to those found on orthopyroxene surfaces, probably from partial alteration, explain this flotation mechanism.     

Rejection of arsenic minerals in sulfide flotation — A literature review

Arsenic is one of the most dangerous inorganic pollutants and thus a penalty element in many base metal concentrates. Arsenic removal in sulphide flotation has been studied extensively with various approaches, including pre-oxidation of flotation pulp, E_h control during flotation and the use of selective depressants/collectors. Pre-oxidation of flotation pulp using oxidizing agents or aeration conditioning represents a simple approach in arsenic removal and was found effective in many cases. Selective flotation of arsenic minerals through E_h control has made significant advances in recent years with promising results achieved. In addition, various depressants and collectors have also been studied in arsenic removal. In this communication, the various approaches used in selective flotation of arsenic minerals are reviewed with emphasis on the development in recent years.     

Geochemistry of deep formation waters in the Canning Basin,Western Australia,and their relationship to Zn‐Pb mineralization

The Canning Basin contains several Mississippi Valley‐type Zn‐Pb sulphide prospects and deposits in Devonian carbonate reef complexes on the northern edge of the Fitzroy Trough, and in Ordovician and Silurian marine sequences on the northern margin of the Willara Sub‐basin. This study uses the ionic composition and 5D, δ¹⁸O, δ³⁴S, ⁸⁷Sr/⁸⁶Sr isotopic data on present‐day deep formation waters to determine their origin and possible relationship to the Zn‐Pb mineralizing palaeofluids.

The present‐day Canning Basin formation waters have salinity ranging from typically less than 5000 mg/L up to 250 000 mg/L locally. The brines are mixtures of highly saline water, formed by seawater which evaporated beyond halite saturation (bittern water), with meteoric water ranging in salinity from low (<5000 mg/L) to hypersaline water (up to about 50 000 mg/L) formed by re‐solution of halite and calcium sulphate minerals. The original marine chemical composition of the bittern‐dominated brines was changed to that of a Na‐Ca‐Cl water by addition of Ca and removal of Mg and SO₄, initially by bacterial sulphate reduction and later by dolomitization of carbonate. Other reactions with terrigenous components of the sediment have provided additional Ca and Sr, including a small proportion of ⁸⁷Sr‐rich material. The δ³⁴S values of the bittern‐containing waters are within the range over which marine sulphate has fluctuated from the Ordovician to the Holocene, although one of the hypersaline waters has a value of +6.8%, indicating SO₄ of non‐marine origin. The pH of the bittern‐containing waters is low (about 5) and they contain significant concentrations of dissolved Fe (up to 120 mg/L).

The Canning Basin bitterns appear similar in origin and chemical composition to highly saline marine brines in the Mississippi Salt Dome Basin, USA, which are known to be either metal or sulphide‐rich depending on the organic content of the host rock. In the Canning Basin, mixing of the bittern water with the various types of meteoric water has resulted in decreases in salinity, Na, Ca, Mg, K, Sr, Li and Fe, and increases in HCO₃, SO₄ and pH.

Mixing of the bitterns with other types of metalliferous fluids and/or with sulphate‐containing hypersaline meteoric waters formed from the same marine evaporite sequence should produce ore‐precipitating fluids which are relatively hot and saline, and the resulting ore deposit should be of high grade and contain abundant sulphate minerals. In the southern Canning Basin, this type of mixing and the corresponding style of ore deposit is evident in the evaporite‐associated areas of Zn‐Pb mineralization near the Admiral Bay Fault. If the bitterns mix with low salinity HCO₃‐waters in near‐surface environments, then the ore‐precipitating fluids should have relatively low salinities and carbonate minerals would precipitate during later stages of mixing. In the Lennard Shelf, the present‐day formation waters, the style of the Zn‐Pb deposits, and range of salinity and temperature of the ore‐forming palaeofluids are consistent with this type of mixing.     

Sulfide-associated mineral assemblages in the Bushveld Complex, South Africa: platinum-group element enrichment by vapor refining by chloride–carbonate fluids

The petrology of base metal sulfides and associated accessory minerals in rocks away from economically significant ore zones such as the Merensky Reef of the Bushveld Complex has previously received only scant attention, yet this information is critical in the evaluation of models for the formation of Bushveld-type platinum-group element (PGE) deposits. Trace sulfide minerals, primarily pyrite, pyrrhotite, pentlandite, and chalcopyrite are generally less than 100 microns in size, and occur as disseminated interstitial individual grains, as polyphase assemblages, and less commonly as inclusions in pyroxene, plagioclase, and olivine. Pyrite after pyrrhotite is commonly associated with low temperature greenschist alteration haloes around sulfide grains. Pyrrhotite hosted by Cr- and Ti-poor magnetite (Fe₃O₄) occurs in several samples from the Marginal to Lower Critical Zones below the platiniferous Merensky Reef. These grains occur with calcite that is in textural equilibrium with the igneous silicate minerals, occur with Cl-rich apatite, and are interpreted as resulting from high temperature sulfur loss during degassing of interstitial liquid. A quantitative model demonstrates how many of the first-order features of the Bushveld ore metal distribution could have developed by vapor refining of the crystal pile by chloride–carbonate-rich fluids during which sulfur and sulfide are continuously recycled, with sulfur moving from the interior of the crystal pile to the top during vapor degassing.     

The Hemlo gold deposit,Ontario: A geochemical and isotopic study

The Hemlo deposit, near Marathon, Ontario, is one of the largest gold deposits in North America. It is stratiform within Archean metamorphosed volcano-sedimentary rocks. The main ore zone is composed of pyritic, sericitic schist, and massive barite. This is the first report of stratiform barite in the Archean of North America, but other occurrences have since been found west of Hemlo. The mineralization is substantially enriched in Au, Mo, Sb, Hg, Tl and V and lacks carbonate. Because of metamorphism and deformation of the body its genesis is uncertain.${}^{87}\text{Sr}{}^{86}\text{Sr}$ of .7017 for barite from the deposit is similar to that of the sedimentary barite west of Hemlo and to initial ratios of contemporaneous volcanic rocks. At the base of the main ore zone, barite with δ^34S of +8 to +12%. was deposited with ~0%. pyrite. Upward, both barite and pyrite get isotopically lighter, with minimum values for pyrite, to ?17.5%, in non-baritic schist forming the upper part of the ore zone. In drill section, Au grades correlate with the isotopic composition of pyrite. This, and the association of fractionated sulphide with sulphate, suggests that Au, pyrite and barite were deposited contemporaneously. The linked, asymmetric distributions of S minerals and isotopic distributions, which are continuous from section to section, and the isotopic similarity of the Hemlo and western barites are consistent with a syngenetic depositional model.Two sources for the S minerals are considered. In the first, exogenous sulphate from a restricted basin were partially reduced in a geothermal system to form ³⁴S-depleted sulphide. In the second, the sulphate and sulphide are of magmatic-hydrothermal origin. Sulphate and fractionated sulphide are uncommon in Archean rocks, but one or both occur with unusual frequency in major Archean gold deposits. Hydrothermal fluids of moderately high , containing sulphate and permitting isotopic fractionation between oxidized and reduced S species, may have favoured the dissolution, transport and precipitation of Au.     

Effects of an ultrasonic field on the flotation selectivity of barite from a barite-fluorite-quartz ore

The influence of an ultrasonic field frequency of 22 kHz and intensity of 0.5 W/cm² has been examined on the flotation of barite, fluorite and quartz as well as on their ability to adsorb dodecyl- and cetylsulphates. The tests affected the flotation of pure minerals in a Hallimond tube as well as the flotation of a natural barite-fluorite ore. It has been found that ultrasonic pretreatment of minerals causes an increase in the flotation rate of barite and a decrease in the flotation rate of fluorite. Ultrasonic pretreatment of the natural barite-fluorite ore before its flotation is the most advantageous. In this case it is possible to obtain concentrates of barite composed of a low amount of CaF₂. This may be explained by the different effects of ultrasonic vibrations on barite and fluorite which cause some improvement of the selectivity of their flotation separation.For a full explanation of these results the effects of ultrasonic pretreatment of the minerals on their adsorption properties and surface topography have been investigated, as well as the direct influence of ultrasound on the adsorption process.     

Pre-concentration and residual bitumen removal from Athabasca oilsands froth treatment tailings by a Falcon centrifugal concentrator

Both froth flotation and centrifugal concentration were used to pre-concentrate the oil sands froth treatment tailings prior to the recovery of heavy minerals (titanium and zirconium minerals). Over 90% of the heavy minerals were recovered into a bulk flotation concentrate that was about 50% of the feed mass at 85 °C without any reagents. The same recoveries were obtained at 50 °C with the addition of NaOH and/or sodium oleate. However, the flotation concentrate also recovered over 90% of the residual bitumen and much of the clays/slimes. Subsequent treatment of the flotation concentrate such as dewatering and bitumen removal would be difficult due to these residual bitumen and clays. On the other hand, a SB40 centrifugal concentrator recovered over 85% of the heavy minerals but less than 30% of the residual bitumen. With improved liberation the recovery of the residual bitumen into the concentrate could be further reduced. The particle sizes of the SB40 concentrates were also larger than the flotation concentrates, making subsequent processing much easier.     

鄂东北地区沉积变质型锰矿矿物学特征和地球化学特征

扬子陆块北缘的鄂东北地区是湖北省沉积变质型锰矿集中区,发育了广水—黄陂—蕲春SEE-NWW向元古代沉积变质锰矿带,锰矿赋存于新元古界红安岩群中.本文以鹰咀山锰矿床、四方山锰矿床及孙冲锰矿床为例,分析研究其矿物学特征和地球化学特征,以便为总结该区锰矿床成矿环境及成矿物质来源提供帮助.研究表明,锰矿石矿物主要为菱锰矿、软锰...     

Pressure-oxidation autoclave as an analogue for acid–sulphate alteration in epithermal systems

Gold extraction at the Macraes gold mine in New Zealand involves concentration of pyrite and arsenopyrite, oxidation of those sulphides, then cyanidation. The ore concentrate is predominantly Otago Schist host rock (andesitic composition) with up to 15% sulphides. The oxidation step is conducted on ore concentrate slurry in an autoclave at 225°C and 3,800 kPa oxygen gas pressure with continuous feed. The slurry takes ca. 1 h to pass through the autoclave, during which time the sulphides are almost completely oxidised. Sulphide oxidation causes strong acidification of the slurry, which is maintained at pH of 1–2 by addition of CaCO₃. Scales form on walls in the autoclave, with minerals reflecting progressive oxidation and alteration of the ore through the system. The schist in the ore feed has mineralogy similar to propylitically altered andesite: quartz, albite, muscovite, chlorite, and pyrite. Muscovite undergoes almost complete dissolution, with associated precipitation of quartz and alunite (KAl₃(SO₄)₂(OH)₆). Other principal minerals deposited and discharged include anhydrite (and/or gypsum), jarosite (KFe₃(SO₄)₂(OH)₆), hematite (and/or amorphous iron oxyhydroxide), and amorphous arsenates. Dissolved ferrous iron passes right through the autoclave, and variably hydrated Fe²⁺and Fe³⁺sulphate minerals, including rozenite and szomolnokite (both FeSO₄.hydrate) and ferricopiapite (Fe₅(SO₄)₆O(OH).hydrate), are formed along the way. The autoclave chemical system resembles acid–sulphate hydrothermal activity in geothermal systems and high-sulphidation epithermal mineral deposits formed in arc environments. These natural acid–sulphate systems are pervaded by volcanic vapours in the near-surface environment, where widespread dissolution of host rocks occurs and deposition of quartz, alunite, and anhydrite is common. Some of the volume loss associated with these natural systems may be due to dissolution of soluble sulphate minerals by later-stage groundwater incursion.