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By S. Q. Zhu

A newly developed coal flotation collector ZFC and its flotation characteristics for five different coals were introduced in this paper. ZFC is an emulsion composed of 27% diesel oil, 70% water and 3% surfactants. The main surfactant is synthesized with oil which is environmental favorable and reproducible. Compared flotation experiments show that, at the same dosage, ZFC give 2%~5% recovery promotion than typical collector with only a slightly ash content increment, but saving 70% diesel oil. Zeta-potential and Wetting heat measurement indicate that the surfactant helps the interactions between oil and coal particles, the industrial application tests in several coal preparation plants demonstrate that ZFC is suitable both in technical and economical aspects.

Jan 1, 2014

By R. B. Shu

A moderate thermophilic microorganisms, has been isolated (45?) from a typical sulphide mine in the region of Mo Jiang located in the southwest of China. The culture has been used to extract copper from chalcopyrite concentrates obtained from De Xing copper mine. The majority of experiments were carried out in 300mL Erlenmeyer flasks containing 150mL volumes of mineral suspension. Effects of some variable parameters such as solids concentration, pH and the concentrations of inorganic nutrients on the bioleaching of chalcopyrite obtained from De Xing copper mine were investigated. For a given concentrate the most important factor affecting the fractional copper extraction was the size of the mineral particles. The overall rate of leaching was found to be limited by the area of mineral surface. The attack started in cracks and genetic defects and finally reached the whole chalcopyrite surface. As a consequence of this, the ore showed strongly cracks. The additive of ferrous sulfate increases the bacteria activity, but did not improve chalcopyrite bioleaching. The results indicate that the nature and relative proportions of the various minerals present have been shown to be important factors.

Jan 1, 2014

By M. M. Yahyaei

The Sarcheshmeh new concentration plant uses a 32 ft×16 ft constant speed (10.5 RPM) SAG mill with two 5500 hp motors which could rotate in two directions. The mill liners are chrome-molybdenum steel casting type with a Brinnell hardness between 325 and 375 with the lifter face angle of 14° and lifter height of 152 mm. The shell liner consists of 120 (two 60 rows) pieces with a High-High configuration in a rail design. A specially designed liner wear profile measuring device enabled fast and accurate measurements inside the mill during the mill shut-down periods. The measurements indicated that the liner wear profile along the liner length is non-uniform and the highest wear occurs between 1.25m and 2.75m of the mill length. The average weight of liners at the time of removal was 47% of the original weight indicating a significant metal loss. The modification of liner shape was undertaken with the aim of having a uniform profile at the liner removal time. The proposed liner unlike the pervious type did not have a uniform shape with a lifter height of 187mm at the section where the wear rate was high. It was believed that this new profile could arrive at a uniform profile at the liner change out time. A study was also directed to the possible change of charge motion due to the liner profile modification. The dynamic behaviour of charge was investigated through the analysis of forces acting on a single ball using mill characteristics such as mill diameter, rotational speed, lifter height and release angle. The simulation of charge motion with this method and Milltraj TM software indicated that the impact position of charge will change only one degree due to the maximum increase of 35 mm in the lifter height. This assured that the installation of the modified liner would not have any adverse effect on the mill because of ball impacting the mill shell. It was predicated that the amount of scrap metal will reduce to 30% from the current value of 47% beside 1500 h increase in the liner life time.

Jan 1, 2014

By R. S. Wang, S. Z. Zhou, L. Wan, K. W. Zeng, Z. J. Sun, W. G. Wu, Z. B. Qian, X. R. Zhang, Z. K. Hu, Y. Yu

"In view of the present situation that the traditional environment friendly depressants for galena aren’t very effective in the separation of mixed concentrate including copper sulfide and lead sulfide, this research describes a new environment friendly depressant PD-1 and investigates its effects and mechanism in the separation of chalcopyrite and galena. This study is carried out through flotation tests, analysis of infrared spectra and absorption measurements. It is shown that when O-isopropyl-N-ethyl thionocarbamate (Z200) is used as collector, chalcopyrite and galena can be separated in the presence of PD-1 under appropriate conditions. Therefore, it can be concluded that PD-1 has an excellent depression ability and great selectivity for galena. Meanwhile, analysis of infrared spectra demonstrates that PD-1 can strongly absorb on the galena surface by chemical interaction with Pb2+, while it hardly absorbs on the chalcopyrite surface. In addition, the results of absorption measurements reveal that competitive adsorption occurs on the galena surface between PD-1 and Z200, PD-1 can block the absorption of Z200 on the galena surface. However, PD-1 has a little effect on the absorption of Z200 on the chalcopyrite surface under above conditions. What’s more, the hydrophilic groups of PD-1 molecules can make galena effectively depressed. The results of mechanism analysis are in accordance with those of flotation tests.INTRODUCTION In the processing of copper-lead sulfide ores, the process, copper increase and lead reduction (Zhang et al., 2017) after reagents removal of rough concentrate produced by mixed flotation of chalcopyrite and galena, is usually adopted. However, as a result of tight symbiosis and the similar flotability of chalcopyrite and galena, the separation is difficult (Hu and Feng, 2006). There are 3 kinds of depressants for galena in the separation of chalcopyrite and galena concentrate,including dichromate, sulfite and combined depressants of organic or inorganic reagents (Wei, 2012). As dichromate would cause serious environmental pollution, it is gradually banned to be used in industry (Xu et al., 2017; Lin et al., 2017). what’s more, due to the need of acidic slurry, using sulfite is not conductive to the maintenance of equipment and stable production(Wang, 1999). As for the combined depressants, they also have disadvantages of complex pharmaceutical system and no ideal separation effect (Wei and Sun, 2008). Therefore, the development of new safe and effective depressants for galena is a research focus for researchers in the minerals processing (Chen, 2000). In this paper, a new type of organic depressant PD-1 is applied to the copper-lead separation process of ""copper increase and lead reduction"" using Z200 as the collector. In addition, the performances and mechanism of its depression to galena are studied emphatically."

Jan 1, 2018

By A. Tolentino, J. Bravo, M. A. Corona-Arroyo, C. Quintero, R. Zarate, A. Lynch, L. Carillo

"This paper presents the performance of the flotation circuit of Minera Fresnillo PLC, Mexico. A plant survey was carried out on the lead banks and a size-by-size assay on the samples was conducted. The results indicate that the plant is treating fine particles in the flotation circuit. At least 30% of the particles in the feed are finer than 8 microns and that high amounts of Pb, Au, Ag and insolubles are in this particle size. It was also found that higher percentage of insolubles in the -8 micron particles are recovered in the final concentrate rather than being rejected in the tails. The presence of high amounts of insolubles in the concentrate is an issue of the company. The result of the plant survey provided valuable information for effective reduction of the insolubles in the concentrate and for plant optimization. The work conducted is part of the training of the students involved in a mine placement in the Alban Lynch Student Venture. INTRODUCTION Minera Fresnillo is one of the operating mines and the main contributor to the silver production of Fresnillo PLC group, the world’s leading producer of silver from ore. It is located in the mining district of Zacatecaz, Mexico, approximately 650 kilometers from Mexico City. The major minerals that make up the ore are galena, sphalerite, tetrahedrite, pyrargyrite, proustite, polybasite, pyrite and pyrrhotite. Minera Fresnillo has a capacity to treat 8300 tonnes of ore per day. The plant consists of semi-autogenous mill - ball mill – hydrocyclone circuit for primary grinding followed by silver-lead flotation then zinc flotation circuits. This paper reports the plant audit conducted in the silver-lead flotation circuit (Figure 1) of Minera Fresnillo. The circuit includes rougher, scavenger and two stages of cleaning. The tails from the scavenger goes to the zinc flotation circuit while the second cleaner yields the final silver-lead concentrate. The feed to the circuit has a particle size of 90% finer than 75 microns and generates a concentrate with grade of about 35% Pb, 5700 g/ton Ag, 16 g/ton Au and recoveries of 90% Pb, 90% Ag, 64% Au, respectively. Although the plant achieves their target concentrate grade and recovery, the concentrate also contains significant amount of insoluble materials which is about 18%. These insoluble materials consist of gangue minerals. The plant audit was conducted primarily to determine the possibility of further reducing the amount of insoluble materials present in the silver-lead concentrate."

Jan 1, 2018

By Vladko Panayotov, Marinela Panayotova

"Recently, in order to extract metals, the industry is trying to process old metallurgical slag. The material requires very fine grinding that results in enhanced slime-formation. This in turn leads to problems in the course of the flotation process and to a loss of metal. In addition, it causes difficulties in the wastewater treatment aimed at water reuse. The aggregation and separation of the fine particles and their further subjecting to mineral processing would result in more efficient use of raw materials. Closing the water cycle also would be facilitated. The paper presents results from studying sixteen flocculation reagents, commercially available for treating municipal wastewater, including products based on nanotechnology, for their ability to rend the production wastewater in suitable for reuse in the flotation. It turned out that, from all studied reagents, the cationic C-587 is suitable for the purpose. Some of reagents were studied for their ability to flocculate selectively, in presence of coke fines, rich in copper fines which are produced at grinding of a slag from lead-zinc metallurgy. Most promising reagents are chosen, based on the chemical analysis of the flocculated materials. Open-cycle rough copper flotation experiments with the flocculated fines and recycled wastewater gave encouraging results."

Jan 1, 2014

The ball level and pulp load play a key role in the operation of industrial scale ball mills. These two operating variables have a significant influence on the performance of the ball mill and any attempts to optimize these devices require manipulating either one or both of these variables. There are several models that can be employed to perform simulations to optimize the performance of industrial ball mills. However, most of these models require ball load and pulp load measurements as inputs to calibrate the model. The changes suggested by the simulator also provide operating regimes that involve moving either the ball level or pulp load and sometimes both of these variables. A ball mill model coded in JKSimMet was used in conjunction with the Sensomag to optimize the secondary ball mill at Waterval concentrator in South Africa. The results show that the perfect mixing ball mill model can be used in conjunction with the Sensomag to optimize the performance of the secondary ball mill.

Sep 1, 2012

The status of utilization of copper ore resources, and the application and development of biohydrometallury technology in the world is reviewed. Based on the characterization of Zambia?s copper resources, biohydrometallurgy technology is shown to be a practical approach to extract and utilize the enormous low grade copper resource, such as ore tailings and low grade copper ore in this country. Through the cooperation of CSU, China and MMMD, Zambia, ?CNMC-CSU Demonstration Base of Biohydrometallurgy Technology in Zambia? was launched and several biohydrometallurgy plants are being constructed. This indicates that the biohdyrometallurgy technology would be applied soon in Zambia and in the whole Africa. Biohydrometallurgy technology stands as an efficient alternative to the traditional pyrometallurgy process and it can be the key to unlock mineral resources value. Keywords: biohydrometallurgy, low grade copper ore, Zambia, Central South University

Sep 1, 2012

By Bhargav Dhavala, Sristy Raj, Ashok Kumar, Suman Krishna Sit, Adity Ganguly, D. P. Chakraborty

"Tatasteel’s West Bokaro washery#3 is designed to deslime raw coal at 0.5mm; the oversize (+0.5mm) is beneficiated in dense media cyclones (DMC) while the undersize (-0.5mm) is beneficiated in froth flotation (FF) cells. Nearly, 80% of the raw coal feed reports to the DMC circuit consisting of four parallel streams. Presently, the performance of DMCs at washery#3 is interpreted by: (a) comparing the actual plant yield w.r.t the lab predicted yield and (b) misplacement of clean coal to middllings.However, the comparison between actual & lab predicted yield is fallacious given the fact that the lab predicts yield of the borehole sample while the feed received at the plant has different characteristics altogether due to the dilution during mining. To mitigate the said limitations, a quick diagnosis tool using the past data has been developed that will give a prediction of performance of different coal seams in the DMCs, inputs being feed ash to DMCs and stream wise feed specific gravity (coal & magnetite combined).The tool also will help in identifying the root cause on real time basis thereby helping the operator to take necessary corrective actions. The operator can intimate the mining personnel in cases of shale reporting to the feed as a result of dilution during mining. In events of higher standard deviations between the parallel streams w.r.t feed specific gravity, the operator can adjust the parameters accordingly to minimize the yield loss. INTRODUCTION West Bokaro came into existence in 1948, as an independent coal company, managed by M/S Anderson Wright. Tata Steel acquired the Company in 1956 to meet its requirement of metallurgical grade coal for Iron making. Subsequently, in 1976, it was made a division of Tata Steel. In 1974, when coal mines were nationalized, West Bokaro was exempted as it produced coal only for captive consumption of the Steel Works. The first washery of India was set up in West Bokaro. The business objective of the West Bokaro division is to produce clean coal at optimum cost for captive use in the steel plant of Tata Steel at Jamshedpur. The strategy is to reduce ash with minimum loss of yield so that quality of coal improves and yet the cost is beneficial vis-a vis imported coal. The primary product is the metallurgical grade coal for coke ovens, which converts coal into coke for use in the Blast Furnaces."

Jan 1, 2018

By G. M. Savov

Copper recovery via Solvent Extraction (SX) process is a well-known technique, which is practiced commercially for approximately 40 years. The main advantages of the SX process are: an absence of using high temperatures (not more than 50oC), complete recycling of barren solutions, very high selectivity at removal and purification of metals, metal conversion to a form, suitable for easy subsequent recovery. Despite the wide acceptance of Solvent Extraction, it does have some shortcomings, namely SX employs large quantities of volatile organic substances. This leads to huge plant ?footprint? of SX circuits. The SX is very sensitive to low temperatures and quantity of total suspended solids in feed solutions and this causes bad phase disengagement times and therefore poor process performance. And most important ? low grade solutions (with copper concentrations below 1 gram per litre) are very unattractive for treatment via Solvent Extraction process, because capital costs for SX plants are not a direct function of copper tenor in the feed. The combined process with Ion Exchange (IX) and Solvent Extraction ? further called IX/SX by IONTECH Engineering was developed. This combination eliminates SX negative characteristics shown above. The key findings of the IX/SX process are; (1) recovery of copper from pregnant leach solutions with metal concentrations, varying on a broad range; (2) can be operate effectively with very low-graded copper pregnant leach solutions; (3) the construction of large ponds for pre-filtration of the pregnant leach solutions is not necessary; (4) working with turbid solutions and solutions containing large quantities of suspended solids; (5) winter operation without troubles; (6) strongly reduces organic losses; (7) technological approach lead to plant sizes reducing. This paper reviews the main stages of the combined IX/SX process, the applications for metal recovery and introduces projects where the process is applied. Key findings of the process are also presented. A comprehensive technical comparison between processes has been carried out. This paper also evaluates the advantages of using combined IX/SX technology as a purification and separation step in copper production process, with the aim of further increasing the overall copper recovery and to ensure that a suitable copper concentration in the advanced electrolyte is achieved. The implementation of a Ion Exchange (IX) process in the classic Solvent Extraction-Electrowinning process(SX/EW) is found to be beneficial for processing of pregnant leach solutions both from spent and new copper heaps and dumps, acid mine drainage and other industrial streams without any preconditioning as well as in terms of achieving improved recoveries and copper cathode quality.

Sep 1, 2012

By J. J. Liu

In the Bayer process, control of alumina trihydrate particle size, oxalate stability and morphology and foaming is crucial for improving the yield and quality of alumina trihydrate. One way to economically achieve such control is to employ specifically developed chemical additives, termed, crystal growth modifiers (CGM?s). In this paper, the mechanism of action and practical application of CGM?s in the Bayer process are summarized. The application of CGM additives allows for both enhanced agglomeration and secondary nucleation control, and hence coarsening of the particles. Current research efforts have utilized the information gained from mechanistic studies to enhance the performance of CGM products. It was demonstrated in both laboratory tests and industrial operations that the newly developed CGM formulations have a range of properties with enhanced performance, compared to the current commercial products.

Jan 1, 2014

By C. R. Mambote

Vanadium is an important metal that is used mainly in ferrous and non-ferrous alloys due to the high tensile strength, hardness, fatigue resistance and corrosion resistance. Vanadium consumption in the steel industry represents about 85% of the vanadium-bearing products produced worldwide. The primary sources of the metal are patronite, roscoelite, and mottramite. Vanadium has also been produced as a by-product of the uranium production program which uses carnotite ores as a source of uranium. Vanadiferous magnetite iron ores are used for producing vanadium as well. In addition, it is known that vanadium can be recovered from the ashes of crude oil and petroleum coke. The process for treating boiler residues, fly ash and petroleum coke is similar to the process used to treat spent catalysts and ores. However, some of these materials may contain high carbon that must be removed at specific stage of the operation. Several processes are available for obtaining vanadium from fly ash, such as roasting vanadium bearing materials in the presence of sodium salt. The salt roasted calcine is subsequently leached with an alkaline or acidic solution. To obtain a cal-cine from which the vanadium can subsequently be recovered, the carbon in the source materials has to be eliminated prior to the roasting process. Other processes use the conventional hydrometallurgical route, in which fly ash is leached with sulphuric acid to obtain an impure vanadium pentoxide. The impure vanadium pentoxide is then treated with a sodium carbonate solution under atmospheric conditions to subsequently precipitate vanadium as ammonium metavanadate. Actually, the salt roasting process is the only process used commercially. In the present study, the progress in the technology of vanadium extraction from secondary materials is reviewed. The perspectives and the challenges for new process development are discussed.

Jan 1, 2014

By Jonas Addai-Mensah

Despite the fact that nickel (Ni) laterites accounts for about 60 % of the world?s nickel mineralization, commercial processing of complex, low grade Ni laterite ores by conventional beneficiation (e.g. magnetic, electrostatic and flotation separation) still presents intractable challenges, particularly in heap leaching. Invariably, low grade laterite ores require aggressive hydrometallurgical techniques (e.g., highly acidic lixiviant leaching at ambient or elevated temperatures) for Ni and cobalt (Co) extraction. As a precursor to heap leaching, agglomeration of the multi-mineral phase feed particles into robust and porous granules of 4-10 m permeable bed, is essential. In the present work, several basic and applied studies of the agglomeration behavior of real Ni laterite ores and selected oxides and clay minerals (hematite, quartz smectite and kaolinite) which constitute the predominant host gangue phases of typical laterite ores are performed. Isothermal, batch agglomeration tests involving sulphuric acid solution as a binder were carried out to produce coarse, narrow-sized (5 ? 40 mm) granules which were well characterized. The influential role of feed ore characteristics (e.g., mineralogy/chemistry and primary particle size distribution) and binder composition (30 vs. 44% w/w H2SO4) and dosage (15-25 wt.%) in agglomeration behavior and granule properties were examined through several characterization techniques including granule size, compressive strength, bed percolation and re-wetting stability and 3-dimensional micro-structure analyses. Links between feed mineralogy/chemistry and size, binder formulation, agglomeration behavior, curing conditions and final granule properties and structural characteristics are established. The implications of the findings to Ni laterite plant agglomeration for enhanced heap leaching are discussed. Keywords: nickel laterite, complex low-grade ores, agglomeration, heap leaching, micro-structure

Sep 1, 2012

By Ana C. C. Pacheco, Maurício L. Torem

"The aim of this work was the study of the effect of the type (Fe3+, Al3+ and Fe3+ and Al3+ mixture) and of the coprecipitant concentration on As5+ removal by ACF. Removal of As5+ using Sodium Dodecylsulfate (SDS) as a collector was studied by Adsorbing Colloid Flotation (ACF) at laboratory scale. The morphology of the precipitate retained in the foam was analyzed by Scanning Electron Microscopy (SEM/EDS).By comparing the coprecipitant type and concentration studies it could be concluded that As5+ removal in the presence of Fe3+ (160 mg.L-1) alone, or a Fe3+ (80 mg.L-1) and Al3+ (40 mg.L-1) mixture, is equivalently effective (99,9%) and greater than in the presence of Al3+ (80 mg.L-1) alone (97,7%).Through SEM/EDS analyses, it was possible to observe that both morphology and composition of the precipitate produced in the solution and retained in the foam depend on the physico-chemical conditions of the system, that is, on the species present in the solution."

Jan 1, 2003

By T. Sun, J. Kou, C. Sun, D. Gong

"HPGRs (high pressure grinding rollers) have demonstrated higher energy efficiency than conventional comminution equipment due to their application of particle-bed breakage mechanism. In the past decades, a large number of studies have been conducted to understand the characteristics of particle-bed breakage, however, few of them concerned the difference between single-particle and particle-bed breakage in compression comminution. This comparison is able to demonstrate possible advantages of particle-bed against single-particle in a breakage event due to the isolation of the effect of force loading mechanism. The present study investigated progeny fragment size and energy efficiency of these two breakage methods at variable energy inputs and particle sizes. The results show that at low energy inputs of around 0.25 kWh/t, the numbers of fines resulting from the two breakage methods are very similar. However, at higher energy inputs of around 1.0 or 2.0 kWh/t, particle-bed breakage generated significantly more fines. From the perspective of newly generated surface energy, particle-bed breakage is obviously more energy efficient than single-particle breakage at energy inputs between 1.0 and 2.0 kWh/t. It was also found that HPGRs demonstrate high energy utilization rate in generating new surface energy within their typical range of specific energy input. INTRODUCTION Rock comminution is an important and energy-intensive process in mining operations. Nowadays, decreasing head grade and mineral liberation size of ore deposits greatly increase the energy cost of comminution process. HPGRs have been successfully applied in the mining industry to improve the energy performance of comminution circuits. Typically, 10 to 30% of energy saving can be achieved due to the application of HPGR (Wang et al., 2013; Casteel, 2005; Günter et al., 1996)."

Jan 1, 2018

By Y. F. Guo

Laboratory scale experiments were conducted to produce titanium-rich material from Panzhihua ilmenite. The results showed preoxidation with sodium salt additive especially for Na2B4O7 signif- icantly advance the reduction of iron in Panzhihua ilmenite. Acceleration mechanism of preoxidation with Na2B4O7 has been studied here. The maximum metallization of iron 92% can be obtained under conditions of preoxidation at 850? for 30 min and subsequent reduction at 1100? for 150 min. The rusting separation technique to reduced ilmenite has been further studied, obtaining titanium-rich product with TiO2 over 82% and the recovery of TiO2 above 97%.

Jan 1, 2014

By A. Boehm

Mineral selective flash roasting (Steiner process) in oxidizing atmosphere was tested successfully for the efficient low intensity magnetic separation of siderite from ankerite and other gangue minerals within the ore of the Steirische Erzberg, Austria. The calcium, magnesium and manganese containing siderite turns selectively into a ferromagnetic oxide phase while ankerite remains paramagnetic. The expulsion of CO2 increases the volume specific surface depending on the selected temperature. Unlike pure iron oxides absorbing SO2 below 530°C, the calcined siderite (enriched in the magnetic product of the Steiner process) acts as a sorbent for SO2 between 500 and 820°C. The effect was studied by thermogravimetric analysis and particle bed tests complemented with neutron thermo diffractometry (D20/ ILL). The energy input was simulated with the help of a tube furnace. The composition of the artificial combustion gas permeating the bed was close to that measured in pilot scale tests (6 % CO2, 12 % O2, 700 vpm SO2). The evaluation of data relating the SO2 variation in the off gas monitored by electrochemical cells to the actual phase composition revealed an intermediate ferrite phase as absorber. During the rapid decomposition in oxidizing atmosphere starting at 500°C the occurring siderite alters to a (CaO, MgO, MnO)Fe2O3 ferrite as an intermediate phase accompanied with sudden SO2 absorption. SO2 disintegrates the ferrite structure forming MgSO4 and MnSO4, taking Fe2O3 as a catalyst. Ankerite (enriched in the non magnetics of the Steiner process) starts to absorb at temperatures above 1000°C forming gypsum. The findings support the SO2 controlled operation of the Steiner process by ?autodesulfurisation?. It explains aspects of the SO2 implementation reactions within off gas recycling in Austrian sinterstrands. Keywords: magnetising flash roasting, neutron thermo diffractometry, SO2 absorption, siderite, ankerite

Sep 1, 2012

By Robert van Hille, Alison Lewis

The precipitation of a selection of metals from both a synthetic and an actual metal-rich effluent was investigated. The experimental aspects of this study were carried out in a two-stage process consisting of a pre-treatment clarifier and a fluidised bed (pellet) reactor. Each unit operation in the two-stage process was investigated separately. The pre-treatment clarification stage at pH ˜ 5 resulted in a 99.9% removal of iron and 97.3% removal of aluminium. The pellet reactor was used to precipitate nickel as nickel carbonate from a pure stream and a removal efficiency of 99.6% was achieved. The high local supersaturation at the reagent inlet points caused the formation of a large amount of fines, but these agglomerated onto the pellets up the length of the bed. For copper precipitated as copper sulphide from a pure stream, a maximum removal efficiency of 92% was achieved. The high local supersaturation at the reagent inlets also caused the formation of a large amount of fines, but the extremely sparingly soluble nature of copper sulphide meant that the fines were not agglomerated up the length of the bed. For removal of cobalt as cobalt carbonate from an actual stream, a stable cobalt removal of only 60% was achieved. This was found to be due to the presence of magnesium, which reduced the cobalt precipitation efficiency through the formation of the magnesium bicarbonate ion.

Jan 1, 2003

By S. J. Ma

To look into the ionic release laws of the sulphide tailings in some copper mine, the effects of the soaking period, temperature, oscillating speed, and pH of the solution on the heavy metals ionic re-lease were investigated through static soaking leaching experiments. The results show that Cu2+, Zn2+, Pb2+, Cr3+ are of different leaching behaviors with soaking period. The ionic concentration in soaking solution for four ions has a great gap. Zn2+ is more easily released out of sulfide tailings than Cu2+, Pb2+, Cr3+ , and the ion release concentrations are not proportion to their contents in the tailings. The time for each ion to reach its maximum concentration are different. The minimum concentration do not occur at the first day. Each ion concentration shows different fluctuation characteristic during soaking process. Solution pH, oscillating speed, and temperature affect the releases of Cu2+, Zn2+, Pb2+, Cr3+ out of the tailings to different extent. The effect of pH value on ion re-lease for the four ions ranks as Zn2+>Cu2+>Pb2+>Cr3+, the oscillating speed ranks as Pb2+>Zn2+>Cu2+>Cr3+, and the temperature ranks as Cr3+>Pb2+>Zn2+>Cu2+.

Jan 1, 2014

By Herman D. Mendoza

A rapid recovery/recycling process was introduced utilizing the surface-chemical properties of finely dispersed mercury and alumina (Al2O3) fibers in aqueous environment. The conventional method of amalgamation or .ball milling. involves the mixing of a substantial amount of mercury to collect free gold during the grinding stage. In effect, a portion of the mercury is transformed into minute droplets that readily float and disperse in the amalgamation effluent. The fine droplets of mercury in the dispersion readily attached onto the positively charged macroscopic alumina fibers (i.e. = pH 9.8) at conditions pH 3 to 10. When an effluent from settling procedure after an amalgamation-grinding stage is passed through a column-bed packed with alumina fibers, maximum collection of negatively charged finely dispersed mercury occurred at pH 3 to 6. The collection/attachment efficiency was 99.5%. The collected droplets of mercury, which are left in the column-bed of alumina fibers, were subsequently rinsed with alkaline solution at pH 10 to 11.5. At these conditions, both mercury and alumina fibers carry negative surface potentials and resulted in the partial detachment of mercury from the alumina fibers. The detachment efficiency was only 30-35%. The attachment/detachment mechanisms in this study were analyzed using the DLVO theory.

Jan 1, 2003