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Mining of complex sulphide ore started in the 13th century in the Garpenberg area and Boliden Mineral AB bought the operation in 1957. The ore is rich in silver and zinc, but contains also copper, lead and gold in payable amounts. Fully autogenous grinding was introduced in 1989 and the flotation results have gradually been improved using common basic methods. This paper gives a step-by-step description of how the improvements were made and the dead-ends that also were investigated. The flowsheet today is a by-the-book solution with good liberation as the basic guideline for getting good results.

Two new geochemical reference materials, copper ore JCu-1 and zinc ore JZn-1 have been prepared by the Geological Survey of Japan (GSJ) for the determination of major and minor elements and isotopic compositions. JCu-1 is a sample of Cu-bearing sulfide ore typical of the Kamaishi mine in Iwate Prefecture, Japan, and is composed mainly of hedenbergite, chalcopyrite, quartz and calcite. Pyrrhotite, magnetite and actinolitic amphibole were also commonly found. The Zn-rich ore, JZn-1 is a crude ore from the Kamioka Pb-Zn mine in Gifu Prefecture, Japan. The sample consists of hedenbergite, quartz, calcite, sphalerite and epidote as main crystalline phase. Homogeneity test results showed that all studied constituents including ore elements such as Cu, Pb and Zn can be considered to be homogeneously distributed. Provisional collaborative analyses were carried out in ten laboratories, and the data were evaluated using a robust statistical method using z-scores. Recommended values for a number of major elements including TiO2, Al2O3, MnO, MgO, CaO, Na2O, K2O, Fe (total), Zn, Cu and Pb were established. In addition, information values for eighteen major, minor and trace elements are presented to support future collaborative analyses. Deux nouveaux materiaux geochimiques de reference, un minerai de cuivre JCu- 1 et un minerai de zinc JZn- 1 ont ete prepares par le service Geologique du Japon (GSJ) pour la determination d'elements majeurs, mineurs et de compositions isotopiques. JCu-1 est un echantillon de sulfure typique riche en cuivre, provenant de la mine de Kamaishi (Prefecture de Iwate, Japon) et est compose principalement d'hedenbergite, de chalcopyrite, de quartz et de calcite. On peut trouver aussi de la Pyrrhotite, de la magnetite et de l'amphibole actinolitique. Le minerai de zinc, JZn-1 est un minerai brut de la mine a Pb-Zn de Kamioka (prefecture de Gifu, Japon). Les mineraux principaux de cet echantillon sont l'hedenbergite, le quartz, la calcite, la sphalerite et l'epidote. Les tests d'homogeneite montrent que tous les constituants etudies, meme les elements tels que Cu, Pb, Zn peuvent etre consideres comme etant distribues de facon homogene. Les premiers resultats ont ete obtenus dans un programme de cooperation impliquant dix laboratoires et les donnees ont eteevaluees en utilisant des methodes statistiques robustes basees sur les z-scores. Des valeurs recommandees pour un certain nombre d'elements majeurs dont TiO2, Al2O3, MnO, MgO, CaO, Na2O, K2O, Fe (total), Zn, Cu et Pb ont ainsi eteetablies. De plus, des valeurs indicatives sont donnees pour dix huit autres elements majeurs, mineurs et en trace, afin de servir de base a d'autres analyses faites en cooperation entre laboratoires.

The chalcopyrite bioleaching mechanism was studied to determine its direct or indirect nature. At the same time, a study of possible causes that diminish the dissolution rate and inhibit the attack of this sulphide mineral was carried out. An electrochemical study of the mineral was also performed, which included the elimination or dissolution of possible diffusion barriers formed on the mineral surface. Results of these studies showed that the oxidation state of the dissolved iron (Fe3+) was fundamental to chalcopyrite bioleaching because Fe3+ controlled the relative rate of the oxidation reactions. In addition, the attack of chalcopyrite was controlled by elemental sulphur and intermediate, nonstoichiometric, copper sulphides forming on the chalcopyrite surface, which are less reactive than the original sulphide. Intermediate sulphides caused an important barrier effect at low temperature (35 °C). At higher temperature (68 °C), these intermediate sulphides do not constitute a diffusion barrier due to their dissolution. Microbial attachment to the pyritic phase of the copper ore was related to the dissolution rate of the mineral due to the liberation of Fe2+ after the attack of the pyrite by contact bioleaching. It was concluded that the bioleaching of chalcopyrite concentrate is a cooperative effort involving the simultaneous contact bioleaching of the pyritic phase of the mineral, possibly by an indirect mechanism via thiosulphate, and the indirect bioleaching of chalcopyrite, probably by a mechanism by way of polysulphide and elemental sulphur.

The thermal behavior of mechanochemically activated sphalerite during aging was investigated by calorimetry. The results indicate that mechanochemically activated sphalerite releases the stored energy which may origin from a series of complex transformations. The amount of energy released increases with the grinding time but remains almost constant after grinding for 1 h. It is independent of the grinding atmosphere and is related to the ball-mill medium. The XRD results illustrate a difference of the microstructure between activated and non-activated sphalerite. The microstructure of the activated sphalerite remains the same when it is heated in a calorimeter for the measurement of the heat released. The particle size analyses show that the particle size of the activated sphalerite increases when it is heated in the calorimeter. Therefore, it can be concluded that the released energy is probably caused by the decrease of the specific surface energy.

Indium is an important by-product of zinc metal processing operations. Indium and other metal values are recovered during the production of primary commodities such as zinc by means of complex procedures, many of which are proprietary to each producer. One zinc recovery method consists of the Waelz process followed by leaching and purification prior to electrolytic recovery of zinc as cathodes and subsequent containment of the indium fraction in residues. Related processes for recovery of lead and tin from smelters and refineries also provide indium and other compounds. Indium may be associated with other valuable elements such as vanadium, thallium, gallium and germanium, and cadmium. Typical sulphide-bearing host minerals consist of Sphalerite, Galena, and Chalcopyrite. The igneous intrusions in sedimentary formations may include other base metals such as copper, cobalt, and noble metals consisting of gold, silver, and platinum group metals. The review serves to assimilate the major highlights of this somewhat rare metal which has both strategic importance and is well suited to electronic applications. On a global basis, the writers are aware of 30 producers dedicated to the commercial production of indium metal. Countries such as Belgium, Canada, China, France, Japan, Russia, and the USA are the largest producers of indium while about ten other countries contribute smaller quantities for worldwide consumption. The supply and demand of pure indium products during the past 40 years has been erratic and subject to wide fluctuations in delivered price. The paper describes the sources and established industrial processes for recovery of indium originating from sulphidic materials and process reverts.

Experimental studies on phase equilibria and liquidus in the multicomponent system PbO-ZnO-CaO-SiO2-FeO-Fe2O3 in air have been conducted over the temperature range between 1323 K (1050 °C) and 1623 K (1350 °C) to characterize the phase relations of the complex slag systems encountered in lead and zinc blast furnace sinters. The liquidus in two pseudoternary sections ZnO-“Fe2O3”-(PbO + CaO + SiO2) with the CaO/SiO2 weight ratio of 0.933 and PbO/(CaO + SiO2) weight ratios of 2.0 and 3.2 have been constructed.

Willemite (zinc silicate) is the main zinc mineral in some carbonate-hosted ore deposits (e.g., Franklin, New Jersey; Vazante, Brazil; Beltana, South Australia; Kabwe, Zambia). Recent interest in these unconventional zinc deposits has increased because of high zinc grades that exceed 40 wt percent, relatively low environmental impact of ore processing owing to the lack of acid-generating sulfides in the waste, and advances in ore processing technologies. In the past, most metallogenic studies proposed formation of willemite deposits by supergene or hypogene alteration of preexisting sulfide deposits. However, recent data on the Vazante, Beltana, and Kabwe deposits indicate willemite crystallization at temperatures in excess of 150°C, raising the possibility of primary precipitation from hydrothermal fluids. We use numerical geochemical modeling to examine the formation of willemite under hydrothermal conditions. Activity-activity diagrams reveal that, in the presence of dissolved sulfur and quartz, willemite instead of sphalerite will precipitate under oxidizing (e.g., hematite-stable, sulfate-predominant) and alkaline (pH higher than K feldspar-muscovite-quartz) conditions. Willemite also becomes more stable, relative to sphalerite, at high temperature, and willemite can coexist with magnetite at 300°C. The stabilities and solubilities of sphalerite, willemite, smithsonite, hydrozincite, and zincite were calculated for wide ranges of temperature (25°–300°C), chloride concentration, dissolved sulfur and carbon concentrations, pH, quartz saturation, and oxidation potential. Plots of the solubility of the different minerals as a function of two variables (e.g., temperature and redox state; pH and redox state) allow us to predict the effects of changing chemical conditions, which in turn permits an estimate of the efficiency of particular precipitation processes. Cooling is an effective process for precipitating sphalerite but not willemite, whereas pH increase (e.g., by acidic fluids reacting with carbonates) is effective for precipitating willemite but not sphalerite. Dynamic geochemical models that simulate physicochemical processes are used to understand the formation of the Beltana willemite deposit in the Adelaide geosyncline of South Australia. This small, high grade deposit (850,000 t at 36% Zn) is hosted in dolomite of the Cambrian Ajax Limestone, next to a tectonic contact with the diapiric, halite-bearing clastic sediments of the Callanna Group. The orebody is associated with hematite alteration and is characterized by the total absence of sulfides; willemite is the only zinc ore mineral, and the arsenate hedyphane (Ca 2 Pb 3 [AsO 4 ] 3 Cl) is the main lead mineral. The model results show that willemite will precipitate in response to water-rock interaction and fluid mixing processes at temperatures above 120°C. The presence of arsenate in the hydrothermal fluid is likely to have been important at Beltana; in arsenate-absent models sulfate is reduced to sulfide by the precipitation of ferrous iron as hematite, resulting in the precipitation of sphalerite and galena. In contrast, in models including arsenate the reduction of sulfate to sulfide is inhibited and willemite is predicted to precipitate.

The Padaeng deposit near Mae Sod in western Thailand was the first supergene nonsulfide zinc deposit in the world to be developed as a large modern mining operation. The mine and associated zinc smelter, operated by Padaeng Industry Public Company Ltd. since 1984, went into production with reserves of 4.59 Mt at a grade of 28.9 percent zinc with a 10 percent zinc cutoff. Current resources are 5.14 Mt at a grade of 12.0 percent zinc with a 3 percent zinc cutoff. The Padaeng deposit is hosted by a mixed carbonate-clastic sequence of Middle Jurassic age. The deposit occurs in the hanging wall of the Padaeng fault, a major northwest-trending structure that was active through Cretaceous and Tertiary tectonism and uplift. Nonsulfide zinc ore comprises dominant hemimorphite with minor smithsonite and hydrozincite. Strata-bound ore zones occur within a northwest-dipping, deeply weathered, dolomitic sandstone; steeply dipping and irregular karstic zones in underlying massive, silty dolomite are controlled by north-trending fracture zones. Sulfide zinc-lead mineralization of Mississippi Valley type occured extensively in the vicinity of the Padaeng mine, most notably the small resources at Pha De and Hua Lon. Mineral deposits are typically sphalerite rich with minor galena and pyrite, forming small-scale open-space fillings, veins, and replacements within hydrothermal dolomite. Mineralization is dominantly strata bound within a horizon of intense hydrothermal dolomitization that forms the stratigraphic hanging wall to the nonsulfide ore zones at Padaeng. The only significant sulfide at the Padaeng mine is within this unit. Only trace sulfide occurs peripheral to, or down dip of, strata-bound or steeply dipping, nonsulfide orebodies. Sulfide mineralization is believed to have accompanied Cretaceous uplift and deformation, related to the onset of oblique subduction beneath the western margin of the Shan-Thai terrane. The nonsulfide deposit is believed to have formed when a substantial body of sulfide ore was uplifted on the margin of the Mae Sod Tertiary intermontane basin, commencing in the middle to late Miocene. Zinc-bearing acidic supergene fluids, generated by oxidation of the precursor sulfide body, reacted with carbonate in the underlying stratigraphic section to precipitate hemimorphite and smithsonite. Fluids were channeled by permeable dolomitic sandstones and by steep fracture and fault zones. Acidic fluids promoted deep weathering and karst formation, allowing mineralization to extend down dip in sandstone units for at least 150 m and vertically for a similar distance in steep structural zones. Transport of zinc out of the precursor sulfide body was facilitated by a falling water table, owing to uplift of the Padaeng fault block and a change from wet tropical to monsoonal or semiarid climatic conditions. There is no evidence for significant in situ replacement of sulfide deposits, and the leached remnants of the precursor sulfide body have been removed by erosion. The supergene process of dissolution and reprecipitation of zinc in the host rocks increased zinc grades and separation of zinc from lead, producing an economically attractive deposit. Successful exploration for this type of deposit requires a good understanding of the controls on primary sulfide mineralization and a good knowledge of local neotectonism, uplift history, hydrogeology, climatic evolution, and weathering history.

The results of oxidative leaching kinetics of sphalerite concentrate in ammonia solution are presented. The effect of oxygen partial pressure (0.5–10 atm), ammonia concentration (1.54–5.35 M), pH (10.4–11.2), leaching temperature (90–130 °C), particle size (−90+75 to −53+45 μm), and agitation speed on the leaching rate were determined. For the generation of kinetic data, 1% of slurry density was used. Leaching rate was nearly independent of agitation and pH in the studied range. From the comparison of experimental reaction rate constant with calculated mass transfer coefficients, it was established that chemical reaction rate is the slowest process. Shrinking core model for surface reaction fitted the experimental data as well. Reaction order with respect to P O 2 and [NH 3 ] were 0.2 and 0.6, and the activation energy was determined to be 44.3 kJ/mol.

The para-goethite (PG) iron removal process is one of the several precipitation processes that is utilised today to remove iron from zinc-rich processing solutions. In this paper, the para-goethite process is reviewed and compared with results obtained from a study of similar Zincor Process. The distribution of iron in the Zincor iron residue was found to be as follows: approximately 50% as a combination of schwertmannite and ferrihydrite, 20% as jarosites, 25% as franklinite and trace amounts of pyrite as well as 5% of an unknown phase. This study confirmed that goethite is not present in Zincor's iron residue and that iron is mainly removed in the form of poorly crystalline, intermediate iron phases such as schwertmannite and ferrihydrite. The presence of these intermediate phases in zinc plant iron residues is proposed to be mainly a function of the specific pH profile employed during iron removal and the coprecipitation of silica. Based on these findings, it can be concluded that the Zincor Process in its current form is distinctly different to that historically considered to be the similar patented para-goethite iron removal process, as practiced at the Porto Vesme and the Pasminco Hobart hydrometallurgical zinc plants.

A zinc silicate ore was treated with sulfuric acid in a water-starved system in the presence of microwave irradiation. Phase changes occurring during the reaction process were examined by X-ray powder diffraction analysis, and the effect of microwave irradiation time and water amount used on the extraction of zinc, silica and iron was investigated. It is demonstrated that the hemimorphite present in the ore is predominantly changed to ZnSO 4 ·6H 2 O for samples without microwave irradiation and ZnSO 4 ·H 2 O for those with microwave irradiation, respectively. Silica and iron are changed to quartz and Fe(OH) 3 . An increase in microwave irradiation time can slightly increase the extraction of zinc and decrease the dissolution of iron. The increase of water amount used can increase the extraction of zinc and considerably decrease the dissolution of silica. Under optimum conditions, the extraction percentage of zinc is 99.08% and the dissolution of silica and iron is as low as 0.30% and 0.10%.

A new spectrophotometric method for the microdetermination of zinc is proposed. The method is based on complexation reaction of zinc(II) with the chromogenic agent 2,3-dichloro-6-(2-hydroxynaphthylazo)quinoxaline in the presence of cetyltrimethylammonium bromide (CTAB) and nonyl phenoxy polyetho-xyethanol (OP) in slightly basic medium containing 20% (v/v) ethanol. Under certain experimental conditions, Beer's law is obeyed over the range 0.02–0.80 µg ml−1 of Zn2+ with molar absorptivity of 1.06 × 105 l mol−1 cm−1 and Sandell sensitivity of 0.62 ng cm−2. The limits of detection and quantification as well as the regression equation are also calculated. The relative standard deviation for ten determinations for sample containing 0.5 µg ml−1 was found to be 1.15%. As compared with other methods, our method is highly sensitive and selective because of the complex has high, and sharp absorption band at 616 nm. In addition, the present method is simple and rapid, no heating, no extraction or standing is...

The QPPR approach has been used to model cupferrons as mineral collectors. Separation efficiencies (Es) of these chelating agents have been correlated with property parameters namely, log P , log K oc , substituent-constant † , Mullikan and ESP derived charges using multiple regression analysis. Es of substituted-cupferrons in the flotation of a uranium ore could be predicted within experimental error either by log P or log K oc and an electronic parameter. However, when a halo , methoxy or phenyl substituent was in para to the chelating group, experimental Es was greater than the predicted values. Inclusion of a Boolean type indicative parameter improved significantly the predictability power. This approach has been extended to 2-aminothiophenols that were used to float a zinc ore and the correlations were found to be reasonably good.

GSJ has issued many geochemical reference materials, which have been analyzed by many researchers. According to the organization change of GSJ, National Institute of Advanced Industrial Science and Technology, the GSJ geochemical reference materials were charged from April 1, 2001. Therefore, the certified values have to be decided before the distribution of reference materials by collaborative analysis. In this study, collaborative analyses were carried out on the two latest GSJ geochemical reference materials JCu-1 (Copper ore) and JZn-1 (Zinc ore) in 10 laboratories. The analytical data were obtained on 9 components (TiO2, Al2O3, MnO, MgO, CaO, Na2O, K2O, T-Fe, Zn), and Cu (JCu-1) and Pb (JZn-1). ICP-AES and AAS (Na, K) were mainly used. The analytical results agreed comparatively well. In a statistical analysis, the reference values were mainly decided using the robust method. ISO typically recommends that data be submitted from no fewer than 15 laboratories for deciding the certified values; the reference values were considered to be the preliminary certified values.

CSIRO Minerals has developed a particle size analyser based on ultrasonic attenuation and velocity spectrometry combined with gamma-ray transmission. The analyser now incorporates a gamma-ray transmission gauge utilising an ultra-low activity radioisotope source that is exempt from licensing regulations. The particle size analyser is applicable to the measurement of 0.1– 1000 μm diameter particles directly in highly concentrated slurries without dilution. The technique has been optimised for use in mineral processing slurries such as those found in grinding circuits. These slurries often have high solids loadings, broad particle size distributions and multiple components of the solid phase. The technique is particularly useful for applications where excess fines may be present. The analyser has been extensively tested on a range of industrial slurries and has been demonstrated in a number of laboratory and plant trials on iron ore, silver/lead/zinc ore and titanium dioxide pigment slurries. CSIRO is currently developing particle size analysis systems for permanent installation in two mineral plants in late 2001 or early 2002.

Extraction of low grade zinc ore found in Gumau- Toro town was carried out using gravity and froth flotation methods. Analysis of the chemical composition reveals that the crude ore contains 20.20% Zinc and other related minerals such as 66.72% SiO2, 2.36%.Pb, 16.62%Fe, 0.001%Ag, these are impurities that hindered the grade of zinc in this ore from appreciating. Fractional and grain sieve size results revealed that the liberation size of the ore is at -355+250μm assaying 32.41%Zn. At this liberation sieve size, the low grade zinc ore was subjected to four different beneficiation methods using five kilograms (5kg) each as charge into Wilfley shaking Table, Humphrey spiral concentrator, Air floating Machine and one kilogram (1kg) for froth flotation. Resulting products (concentrate and tailing) from these processes were analyzed using instrumentation method. Percentage recovery of each applied process was calculated. This was used to ascertain that the use of froth flotation that gives 74.32%Zn at a recovery of 84.62% stands out the best method for zinc extraction towards value addition to the low grade crude zinc ore. ©JASEM Key words : Extraction, Upgrading, Gravity, Froth flotation, Mineral, Fractional analysis.

A Gram-stain-negative, non-motile bacterial strain designated 1NM-4T was isolated from an abandoned lead–zinc ore mine site in Mei County, Meizhou, Guangdong Province, southern China. The isolate was light yellow, strictly aerobic, oxidase-negative and catalase-positive. Phylogenetic analyses based on 16S rRNA, rpoB and gyrB gene sequences, together with DNA–DNA hybridization values less than 70 %, revealed that strain 1NM-4T belongs to the genus Acinetobacter and may represent a novel species. The major respiratory quinone was ubiquinone 9 (Q-9) and the major cellular fatty acids consisted of C18 : 1ω9c, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C16 : 0 and C12 : 0. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid and two unidentified phospholipids. The genomic DNA G+C content of strain 1NM-4T was 47.17±0.02 mol%. Based on phenotypic, phylogenetic and chemotaxonomic characteristics, strain 1NM-4T should be assigned to a novel species of the genus Acinetobacter , for which the name Acinetobacter guangdongensis sp. nov. is proposed. The type strain is 1NM-4T ( = GIMCC 1.656T = CCTCC AB 2014199T = KCTC 42012T).

One of the most important issues in searching for metallic ores is to discriminate between different types and textures of mineralisations. One of the methods capable of deriving such information is the spectral induced polarisation (SIP). With advances in the time domain IP receivers it is possible to get SIP data with no more additional costs. Therefore using Cole-Cole impedance model for the subsurface it is possible to calculate the apparent Cole-Cole parameters by a curve matching technique in a least squares sense. In the current study, SIP measurements have been obtained using six chargeability slices of the transient decay curve after a 2 seconds square wave current on time at the Irankuh lead and zinc ore deposit complex. It is shown that the SIP measurements will give additional valuable textural and structural information which can be of great help in determining and delineating ore blocks for a systematic exploration program. It was found that the increase in time constant is associated with the ore zones with continuous and greater grain size of IP sources. The average frequency exponent for the vein type ores was found to be about three times larger than that of the disseminated ore zones. Also from the true chrageabilities obtained from SIP analysis, the location of the vein type ores was delineated with a higher resolution. Finally due to its cost efficiency and faster field operation it is suggested to collect SIP data for exploration targets where the textural information can play a very important role in dividing ore to the blocks with similar characteristics.

A complex copper/lead—zinc ore from the Raura plant (Peru) that contains secondary copper minerals was studied with respect to improving copper/lead separation from the copper/lead bulk concentrate. As with most Peruvian plants that treat copper/lead—zinc ores, the Raura plant uses a dichromate separation method, which is ineffective due to the presence of secondary copper minerals. The use of alternative copper/lead separation techniques, such as SO2—starch or heat methods, are restricted due to the high altitude of the plant, which is at over 4300 m elevation. During this study, a new copper/lead separation method was developed and introduced into the plant with significant improvement to the metallurgical results. The new depressant is based on dichromate complexed with carboxy methylcellulose (CMC) and sodium phosphate (Na2HPO4). Apart from an improvement in the plant metallurgy, the level of chromium-6 (Cr+6) in the effluent was reduced ten-fold. This paper summarizes the development testwork in the laboratory and presents the results obtained in the plant using the new depressant.

Zinc concentrates often have a limit on the silica content to avoid problems in the subsequent metal extraction process. The mechanism(s) of silica contamination is, therefore, a concern. This investigation focuses on one possibility: formation of sphalerite–silica aggregates. To study the interaction between sphalerite and silica, a combination of zeta-potential and settling measurements (including color gradation in the suspension) was used in the presence and absence of calcium ions. In the absence of Ca 2+ , the following was observed: at about pH 2 and 8.5, sphalerite homoaggregated and some silica was dispersed; from about pH 3 to 7, the system heteroaggregated; and above pH 9.5, the suspension was dispersed. This behavior did not correlate with settling results on the minerals alone. In the presence of Ca 2+ , from about pH 2 to 7, the sphalerite homoaggregated and the silica was dispersed while above pH 7, heteroaggregation was observed. This behavior did correlate with that of the minerals alone. The zeta-potential results provided only a partial interpretation. An attractive force between sphalerite particles appears to exist at moderately alkaline pH.

Mineral processing and metal finishing industries produce large amounts of effluents containing a host of heavy metals - cadmium, lead, nickel and chromium - with cadmium as a heavy hazard, since, even in mild concentrations, it may give rise to serious environmental problems. Effluents from electroplating industries and from zinc ore hydrometallurgical processing may contain this metal in the range of 15 to 100 ppm. Cadmium harm to all living systems is aggravated by its strong cumulative effect, because of the long number of years required for its elimination. The electrolytic waste treatment has shown advantages over the classical chemical precipitations by alkalis or carbonates, because it does not produce bulky sludges, which require land for its accumulation, and which may have a retarded pollution effect, due to the redissolution by rain; a great advantage comes from the possibility of the metal recovery in a commercially pure form. In this paper, a laboratory scale electrolytic flow-by cell with a reticulated vitreous carbon (RVC) cathode, developed in our laboratory, is described, which permitted the purification of aqueous solutions containing cadmium ion on the usual order of concentration of metallurgical industries effluents; with this cell, operating in a mass transport regime, it has been possible to decrease cadmium concentration of solutions of 2 liters volume from 200 to 0.1 ppm, with current efficiencies up to 40%, in a matter of 85 minutes.

Mississippi Valley type (MVT) sphalerite is a zinc ore mineral (zinc sulfide) found in many sedimentary basins around the world. Its texture is described as a polycrystalline aggregate which results from the precipitation of metal-rich brines in a carbonate host rock. Typically, it exhibits a spatial pattern characterized by an alternation of colored bands with a length scale on the order of 0.1 mm. In our samples, the color of the bands correlates with the local iron composition. In order to understand the origin of banded patterns in MVT sphalerite, we propose here an extension of the competitive growth mechanism often used to model periodic precipitation patterns. In our model, precipitation from interacting brines, growth and dissolution of crystallite radius, and ripening are taken into account. As in all postnucleation models, the nucleation process is neglected. It is shown that our model may indeed generate patterns that are qualitatively compatible with the observed ones. This constitutes an example of self-organization in a geochemical system.

The results of a leaching kinetics study of low-grade zinc silicate ore with sulfuric acid are presented. Effect of ore particle size, reaction temperature, and acid concentration on zinc dissolution rate were determined. The results obtained show that leaching of about 94% of zinc is achieved using −200+270 mesh ore particle size at a reaction temperature of 70°C for 180 min reaction time with 10% sulfuric acid concentration. The solid:liquid ratio was maintained constant at 1:20 g/ml. Leaching kinetics indicate that diffusion through the product layer is the rate controlling process during the reaction. The activation energy was determined to be about 3.2 kcal/mol, which is characteristic for a diffusion-controlled process.

Jarosite waste, originating from the zinc industry using hydrometallurgical processing routes, is considered hazardous. Metals such as zinc, cadmium and copper are present in an environmentally mobile form, thus the jarosite waste is usually stored in lined ponds. Autoclaving of this material with a cellulose type waste material, such as sewage sludge, with the addition of a neutralizing agent will transform most of the metals into oxides, which are immobile under neutral conditions. Jarosite waste and its treated product were tested in standard column tests, as prescribed by Dutch legislation if the material is to be used as construction material. In three weeks time an amount of simulated rainwater, equal to ten times the weight of the solid, was percolated through the samples. The moisture content of jarosite waste is about 40 wt%, reflecting the leach liquor from the zinc refining process; its solutes are easily leached out. This leach liquor initially contained high concentrations of Zn, Cu and Cd, but when a liquid/solid ratio of two (L/S=2) was reached, most of these metals were removed from the jarosite waste. Co-treatment of jarosite with sewage sludge yields a product which is far more acceptable. Even so, the leached amounts of zinc and cadmium do not match the Dutch criteria for second-grade construction material. Counter current washing of the residue improves its properties as a construction material, although the best environmental option for the solid residue is further (thermal) treatment (Rage et al., 1996).

Synthetic and pure zinc solution produced from laboratory leached oxidised zinc ores, under controlled temperature and pH were subjected to continuous elctrowinning operations until the least possible zinc concentration was reached. Conventional DC electrolysis technique, PC and PCR procedures were examined. The effect of organic additives and some of the impurity foreign cations were also investigated. Current efficiencies of more than 95% were obtained from acid sulphate solutions electrolysed at 45 mA cm −2 and 25°C for DC and PC techniques. Electrowinning of zinc from relatively concentrated solutions (160 g dm −3 ) could be achieved, successively, with acceptable current efficiencies down to a concentration of 40 g dm −3 . Copper additives were found to decrease the current efficiency and worsen the quality of the cathode deposits. Manganese and silica were found to have limited effects on both current efficiency and morphology of the deposit. Iron was found to have a deleterious effect on both the current efficiency and the deposit features. Organic additives, gelatine and thiourea, have good leveling effects on the cathode deposits. Gelatine was found to improve the current efficiency especially in the presence of a mixture of foreign cations.

In Spain, several kinds of zinc-containing waste materials are available for zinc recovery. Zn residue leaching studies were carried out using a central composition design of experiments to show the application of statistical analysis to the results obtained. Ammonium carbonate (3M)–ammonia solutions were used for leaching. Zn recovery yields are >95% for this kind of waste material. A regression equation for the dissolution of zinc was developed as a function of temperature, pH and solids concentration. All the parameters were varied at two levels for designing experiments and two base levels and six outer levels experiments were carried out to estimate error and consider second order relationships among the variables.

In this research, the role of zinc ferrite in the hydrometallurgical recovery of zinc in both primary zinc production and zinc-containing waste treatment processes is discussed. In the present work, experiments were performed on the caustic leaching of pure zinc ferrite. The effects of leaching time, caustic concentration and temperature were investigated in the deceleratory period. Atomic Absorption Spectroscopy (AAS) and X-Ray Diffraction (XRD) analyses were employed to analyze both the leach solutions and the residues. It was found that the percentage of decomposed zinc ferrite increased linearly with increasing leaching time. Although the decomposition rate increased with the caustic concentration, it was limited by the high viscosity of the concentrated leach solutions. The maximum percentage of decomposed zinc ferrite was only about 9% under the experimental conditions. Based on the experimental results, it was postulated that the dissolution rate of zinc ferrite in the deceleratory period, was controlled by the diffusion of zinc ions in the imperfect zinc ferrite lattice. The dissolution reaction could be represented as follows: ZnFe 2 O 4 +2[OH − ]=ZnO 2 2− +Fe 2 O 3 +H 2 O

Metallic zinc production from sulfide zinc ore is comprised by the stages of ore concentration, roasting, leaching, liquor purification, electrolysis and melting. During the leaching stage with sulfuric acid, other metals present in the ore in addition to zinc are also leached. The sulfuric liquor obtained in the leaching step is purified through impurities cementation. This step produces a residue with a high content of zinc, cadmium and copper, in addition to lead, cobalt and nickel. This paper describes the study of selective dissolution of zinc and cadmium present in the residue, followed by the segregation of those metals by cementation. The actual sulfuric solution, depleted from the electrolysis stage of metallic zinc production, was used as leaching agent. Once the leaching process variables were optimized, a liquor containing 141 g/L Zn, 53 g/L Cd, 0.002 g/L Cu, 0.01 g/L Co and 0.003 g/L Ni was obtained from a residue containing 30 wt.% Zn, 26 wt.% Cd, 7 wt.% Cu, 0.35 wt.% Co and 0.32 wt.% Ni. The residue mass reduction exceeded 80 wt.%. Cementation studies investigated the influence of temperature, reaction time, zinc concentration in feeding solution, pH of feeding solution and metallic zinc excess. After that such variables were optimized, more than 99.9% of cadmium present in liquor was recovered in the form of metallic cadmium with 97 wt.% purity. A filtrate (ZnSO4 solution) containing 150 g/L Zn and 0.005 g/L Cd capable of feeding the electrolysis zinc stage was also obtained.

The zinc-recovery results obtained in leaching tests run on a complex sulphide ore of Caribbean origin have been statistically processed. The raw material contained 6.95% Zn, 2.41% Pb and traces (0.05%) of Cu. The study was conducted by means of consecutive factorial plans which permitted determination of the manner in which the leaching was influenced by the following factors: (1) oxidizing agent (Fe 2 (SO 4 ) 3 ) concentration; (2) temperature; (3) ore particle size characteristics; and (4) solid/liquid ratio. A regression equation was calculated by the results obtained from the tests; this permitted the derivation of a response surface which provides zinc recovery levels in relation to the levels of the factors adopted in the experiments. It is important to understand the parameters which exert most influence on zinc recoveries during leaching, especially when the presence of finely distributed polluting agents in the useful phase, pyrite in this case, prevents zinc enrichment by the usual physical means.

Deeply buried Mississippi Valley-type deposits that have been or are currently being mined in North America were initially discovered by drilling. Conventional geochemical methods are ineffective for detecting these `blind' deposits when they occur deep within sequences of stable-platform carbonates and shales. The `enzyme' leach is a selective analytical technique for determining trace elements associated with amorphous Mn oxide coatings in soils. In many areas of the world, the enzyme leach method is useful for detecting low-level geochemical anomalies in soils, which are associated with blind mineral deposits. Enzyme leach analysis of soils, collected at the Elmwood Mine, Tennessee, revealed high-contrast anomalies over ore bodies 370 m below the surface. In areas where the soils are in chemical equilibrium, `combination' anomalies occur over Zn ore bodies. These are characterized by asymmetrical halogen halos which occur around a halogen `central low'. Commodity metals (Zn and Pb) and trace elements associated with the ore (Cd, Ba, and Mn) form apical anomalies, which occur over the ore bodies and within the halogen halo. Under most circumstances, agricultural practices do not affect enzyme leach results. However, agricultural activity in central Tennessee appears to have altered the proportion of amorphous Mn oxides in the soils in some locations. Where the MnO2-form equilibrium of the soil has been disturbed, enzyme leach data are erratic. In the one instance where this was encountered, ratioing the data to Mn reveals anomalies which bracket the blind ore bodies.

The process of roasting marmatite and marmatite concentrate was investigated experimentally. Results obtained by DTA under non-isothermal conditions were used for determining kinetic parameters for the oxidation process in the system Zn–Fe–S by using Kissinger and Ozawa methods. The activation energy for the marmatite concentrate oxidation process is 187 and 194 kJ/mol, according to the Kissinger and Ozawa methods, respectively. In the case of the pure mineral marmatite, the corresponding values for activation energy are 69 and 86 kJ/mol. Mineralogical characterization was done by X-ray analysis, which enabled determination of the phases that were present during the oxidation process.

The IBES (Indirect Bioleaching with Effects Separation) process has been developed for the bioleaching of CuZn sulphide concentrate, Zn concentrate, and as a pretreatment for refractory gold ores. In this work the influence of copper ion on the application of this process to a Zn sulphide concentrate was studied. A negative effect of Cu 2+ ions on the rate of zinc dissolution was observed Kinetic curves of ferric leaching have been combined with the residence time distribution for n CSTRs (Continuous Stirred Tank Reactors) in series, in order to predict the mean residence time and the number of reactors required in the ferric sulphate leaching of this Zn concentrate for different copper concentrations. Results indicate that some modifications on the IBES process flowsheet are needed.

In the leaching kinetics of roasted zinc concentrate in NaOH solution, during the early stage of the leaching process, the rate-determining step is diffusion through the zinc ferrite, while in the later stage, it is surface reaction on the zinc oxide. In the shrinking core model, diffusion through a solid layer can be the rate-determining step even in the early stage of the leaching process, not only in later stage. The solid layer changed from zinc ferrite to the porous iron oxide as leaching proceeded, and this substance then thickened progressively due to the selective dissolution of zinc ferrite.

The behaviour of fine particles in the flotation separation of minerals has become of rapidly increasing importance as new, fine grained deposits are exploited. Fine particles float poorly and less-selectively under normal flotation conditions. The behaviour of fine ( 100μm) increased dramatically. In the presence of coarse particles at low pH, a high percentage of fine particles were recovered indicating a fine-coarse particle aggregation (“piggy-backing”) mechanism occuring during conditioning with Cu(II) alone.

Two types of laboratory cells have been constructed to electrowin zinc from sulfate electrolytes: one cell was cylindrical while the other had a rectangular (flat) geometry. Cells were operated on industrial or synthetic electrolytes to electrodeposit zinc onto a spouted bed of zinc particles in the range of 0.75 to 1.45 mm. Current efficiencies and cell voltages have been measured during the course of batch experiments, enabling the calculation of the energy consumption per kilogram of zinc deposited. Electrolyte samples have been analyzed. Current densities (current per unit of cell cross-sectional area) were in the range of 1380 to 6200 A/m2. Most catholytes were initially neutral and contained on the order of 150 g/L of zinc. Final acid contents were in the range of 39 to 114 g/L of sulfuric acid. The performance of the cells (particularly with respect to current efficiency) was superior to prior work on fluidized bed electrowinning from similar electrolytes. The flat cell was superior to the cylindrical cell and showed energy consumptions of less than 3 kWh/kg zinc at current densities up to 3500 A/m2 when used to take the zinc content from 150 to 100 g/L zinc. Current efficiencies in this application ranged from 91 to 92 pct.

The optimum condition for alkaline leaching of roasted zinc concentrate has been studied. The increase in baffle number increased the leaching rate and there existed an optimum pulp density for the highest leaching rate. It was essential to secure complete suspension of particles with a minimum power consumption in designing a leaching reactor. It was required to decrease the vortex depth over complete suspension to increase the leaching rate. The agitation speed for complete suspension (Ns) decreased as the agitator diameter (D) increased, but the dependence of Ns on D increased as the clearance ratio increased.

The study was carried out in 31 workers co-exposed to cadmium, lead and zinc fumes and dusts in a zinc ore refinery. Urinary cadmium, lead, zinc, β2-M levels and NAG activities were determined to evaluate the possible dose-effect relationship between these parameters. A correlation was found between urinary cadmium, lead and zinc concentrations, and urinary β2-M levels and NAG activities of the exposed group. A statistically significant increase was also observed for urinary NAG activity in exposed workers who had urinary cadmium concentrations2 μg g(-1) creatinine. However, in the same exposed group, the increment of β2-M was not statistically significant. In conclusion, the present study thus confirms the earlier observations and may suggest the notion that the urinary NAG seems to be a more sensitive indicator than urinary β2-M level in early stages of renal injury of moderately cadmium co-exposure with lead and zinc even at urinary cadmium concentration as low as 2 μg g(-1) creatinine. When the earlier studies on the irreversibility of cadmium-induced tubular dysfunction and the present results were taken into consideration, the present health-based biological limit proposed by the WHO (5 μg g(-1) creatinine) seems to be high for the occupational exposure to cadmium.

Electroflotation studies on sphalerite fine particles, conducted under careful pH control using buffer electrolytes, reveal that for either H2 or 02 electrolytic gases there exists an optimum pH range at which electroflotation is most effective. This can be explained by the observed dependence of electrolytic gas bubble size on the pH of the electrolyte.

Two different methods for treating an acid wastewater from lead‐zinc processing industry are compared. The results obtained show that chemical treatment (neutralization, alkalization and precipitation by means of NaOH addition) is a better method than electrochemical treatment with Fe electrodes for the heavy metal ions’ diminution, in the case when the initial heavy metal concentrations are relatively law.

Kinetic studies on the flotation of a fine-grained complex lead-zinc ore showed that sphalerite exhibits considerable floatability during the later stages of galena flotation, causing a loss of zinc to lead concentrate. The lead concentrates obtained toward the end of the second lead rougher flotation were examined by X-ray photoelectron spectroscopy (XPS). The results showed that the lead-to-zinc atomic ratios on the surface are significantly higher than in the bulk, suggesting that the flotation of sphalerite is caused by the activation of the mineral by the lead ions present in the flotation pulp. Further evidence of the activation mechanism was given by examining the surfaces of the monominerallic sphalerite specimens that had been immersed in the flotation pulp and other solutions containing lead ions, XPS analysis of the specimens showed significant amounts of lead on the surface. When the specimen was contacted by ore pulp (or simulated plant water) and then with a xanthate solution, the Fourier Transform Infrared (FTIR) spectrum of the specimen showed the presence of lead xanthate and dixanthogen. The proposed activation mechanism is discussed in view of the thermodynamic data available in the literature.

A mineralogical study was carried out on the neutral leach residue and weak acid leach residue generated from Gordonsville zinc concentrate at the Clarksville Electrolytic Zinc Plant of Savage Zinc Inc. The intent was to characterize the mineral forms and associations of germanium. The Gordonsville zinc concentrate consists mostly of sphalerite which has a solid solution Ge content of ~400 ppm; the sphalerite is the dominant, if not only, Ge carrier in the concentrate. The neutral leach residue consists principally of iron gel-silica gel, ZnO, and basic zinc sulfate, (Zn,Cu)4(SO4)(OH)6·4H2O, together with minor amounts of ZnFe2O4, sphalerite, Zn2SiO4, Zn-Fe-Pb silicate, and PbSO4, as well as traces of quartz, silicates, Pb-K jarosite solid solution, Fe2O3, and FeO·OH. The major Ge carrier is the iron gel-silica gel phase, but modest amounts of Ge are present in the ZnO, ZnFe2O4, sphalerite, and Zn-Fe-Pb silicate phases. The weak acid leach residue consists mostly of iron gel-silica gel, ZnFe2O4, PbSO4, Pb-K jarosite, Zn-Fe-Pb silicate, and quartz. The major Ge carrier is the iron gel-silica gel phase which contains up to 1.7 pct Ge and accounts for ~70 pct of the total Ge content of this residue. The remaining Ge is carried by the Zn-Fe-Pb silicate, ZnFe2O4, and some of the rare Mn-Pb-Fe oxide phases.

In the hydrometallurgical production of zinc through the conventional ‘roast- leach-electro win’ process, zinc ferrite is formed together with zinc oxide during roasting of zinc sulphide concentrate. This ferrite is not leached under normal conditions and separates out as residue. Zinc from this residue is recovered in high-temperature acid leaching, which yields a zinc sulphate solution containing high levels of iron. This imposes process constraints, because of high iron level, on recycling the solution to the neutral leaching stage. Investigations into the control of iron levels in residue leach solution by optimizing acidity with zinc hydroxide-gypsum cake are presented in this paper. The plant implementation of this work is also illustrated.

Results from pilot-column flotation tests on a lead-zinc ore show that it is possible to control the redox potential of the column pulp by varying the oxygen activity of the flotation gas fed to the spargers. As a result, the process changes so that the fine zinc minerals are more actively floating in an oxidising environment, at the same time xanthate and frother consumptions increase. The placement of electrodes in the column does change the redox potential readings but only as a result of a change in the oxygen concentration of the pulp. However, the values from a Glassy-Carbon (GC) electrode are consistently lower than those from a Pt foil electrode at the same location. Actual positions of operating points as measured by GCelectrodes fall within the theoretical area for precipitation of lead xanthate.

Several papers have appeared in the literature describing the determination of antimony, where antimony(V) is extracted into the organic phase and the organic solutions directly analyzed by atomic absorption spectrometry (AAS). This paper describes a procedure where antimony from the organic solution is reductively stripped into an aqueous phase and analyzed for antimony by AAS. The advantage of the method for a routine process control laboratory is highlighted.

A mobile flotation facility, based on two 5 L minicells equipped with on-line monitoring of pH, dissolved oxygen and pulp potential, was used to study flotation of pyrite from zinc concentrate (i.e. reverse flotation) at the Trout Lake circuit of Hudson Bay Mining and Smelting Co. Ltd., Flin Flon, Manitoba. A combination of 2 levels of pH (pH 7 and 5.5 adjusted with sulphur dioxide) and temperature (60°C and 80°C controlled by steam) in conditioning and 3 levels of gas composition (air, 95% N 2 , 100% N 2 ) in flotation were tested. For all conditions compared to the use of air, 95% or 100% N 2 gave higher pyrite recovery. Taking 3% sphalerite loss to the float product as a base line, nitrogen increased pyrite recovery by about 10% (absolute) even under the least severe conditions (pH 7 and 60°C). In contrast, the flotation of chalcopyrite was retarded when using nitrogen. From monitoring of the pulp chemistry, oxygen appears to be necessary in conditioning to de-activate sphalerite but its absence in flotation favours selective pyrite recovery. The use of sulphur dioxide in conditioning may help oxygen achieve these conflicting roles: the sulphur dioxide/oxygen combination gives initially strong oxidizing conditions but finally results in consumption of the oxygen. The use of nitrogen in flotation effectively maintains the low pulp potential and dissolved oxygen levels achieved in conditioning permitting less severe conditioning to be used.

The bench scale pressure leaching of a sphalerite concentrate in the presence of different surfactants under high pulp density conditions has been studied. The surfactants were used as dispersants for liquid sulfur, which is a by-product of the elevated-temperature leaching process. The leaching times were 35 or 60 min. The surfactants used were orthophenylene diamine (OPD), lignin sulfonic acid and metaphenylene diamine (MPD). Over 99% zinc extraction was achieved in the presence of OPD for all leaching times and surfactant concentrations. Lignin sulfonic acid and MPD resulted in 86–94% and 95–98% zinc extraction, respectively. In the absence of any surfactant, the extraction was about 50% after 60 min of leaching. Iron extraction increased from 40%, in the absence of any surfactant, to about 80% in the presence of OPD and 62–70% in the presence of lignin sulfonic acid or MPD.

Liquid sulfur-zinc sulfate solution interfacial tensions and liquid sulfur-zinc sulfate solution-zinc sulfide (marmatite) contact angles were measured in the absence and presence of surface-active agents. Interfacial tensions measured varied between 54 ± 1 mN/m in the surfactant-free system and 20 ± 1 mN/m in the presence of a surfactant. The liquid sulfur-zinc sulfide mineral-zinc sulfate solution contact angle varies between 80 ± 5 deg, in the absence of any surfactant, and 148 ± 5 deg, depending on the surfactant used. The surface-active agents were used as dispersants for sulfur in bench-scale zinc pressure-leaching experiments. The observed extent of zinc extraction depends on the surfactant and varies from 40 to 96 pct.

Bacterial leaching of zinc from chat (chert) pile rock and copper from tailings pond sediment was studied in shake flask experiments. Thiobacillus ferrooxidans at 26°C leached 38% of zinc from pulverized rock in 15 days and extracted copper completely from native sediment in 24 h. Experiments omitting single medium constituents for the bacterial leaching of both zinc and copper indicated that the primary mechanism of bacterial leaching is very likely by the indirect route, in which the bacteria catalyze the ferric-ferrous redox cycle. The small particle size of the native tailings pond sediment (particles of ∼ 5 μm in size contributed almost all of the surface area) is a probable reason for the relatively short amount of time required for the copper leaching. Because of the rapidity of the extraction of copper with T. ferrooxidans, larger scale tests were carried out in a bioreactor with mechanical agitation and aeration. Complete extraction of copper was obtained in 12 h. A separate fluidization experiment showed that the tailings pond sediment could be kept suspended with a low fluid bulk velocity (0.3 cm/s). Two possible routes to scale up the bacterial leaching of copper from tailings pond sediment are discussed.

The extraction behaviour of some 3d transition metal ions, along with Cd(II) and Pb (II), from mineral acid media using Cyanex 925 as an extractant was investigated. The effect of variables such as the concentration of mineral acid, metal ion and Cyanex 925 and the nature of the diluent on extraction was investigated. Optimum conditions were developed for the separation of Fe(III) and Zn(II) from various other metal ions. A method is proposed for the recovery of iron-free zinc from zinc blende and calcine.

Emissions of mercury (Hg) to air have regional and global impacts through long range transport in the atmosphere. Primary Zn production is regarded as an important anthropogenic Hg source in China, but research on its Hg emission is limited. To gain a better understanding of Hg emissions from Zn production activities in China, field investigations at four industrial-scale Zn production plants using electrostatic process with Hg removal (HP-WR), electrostatic process without Hg removal (HP-WOR), retort Zn production (RZ), imperial smelting process (ISP), and one artisanal Zn smelting process (AZ) were carried out. In the investigation, Hg emission factors are defined as how much Hg was emitted to the atmosphere per ton Zn produced during various Zn production methods and were estimated by using mass balance method. The results showed that the estimated Hg emission factors of Zn production were 5.7+/-4.0 g Hg t(-1) Zn for HP-WR, 31+/-22 g Hg t(-1) Zn for HP-WOR, 34+/-71 g Hg t(-1) Zn for RZ, 122+/-122 g Hg t(-1) Zn g t(-1) for ISP, and 75+/-115 g Hg t(-1) Zn for AZ. Approximately 80.7-104.2 t year(-1) of Hg was emitted to atmosphere from primary Zn production during the period of 2002-2006 in China.