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Separation performance of a Floatex Density Separator (FDS) has been studied both experimentally and theoretically. Experimental results reveal that at a lower bed pressure the FDS acts like a classifier. Higher bed pressure is required to attain the concentration effect as proper development of suspension density occurs under these conditions. It is seen that the size or density alone is not able to describe the partition fully. The terminal settling velocity, which includes both the size as well as the density of the particle can be a useful descriptor of separation in a FDS. While a narrowly distributed feed offers better performance of a FDS, a wide size distribution of feed results in large scatter in the terminal settling velocity distribution and renders the separation difficult. The closely sized feed enhances the density effect in concentration. A higher teeter water flow rate also helps in carrying larger-lighter particles to the overflow by increasing the cut off terminal settling velocity as it increases the net upward force. A detailed description of separation performance in a Floatex Density Separator has also been established from theoretical considerations. Separation performance of the separator is described using a simple slip velocity model. The model has been validated com-paring the predicted FDS performance results with those experimentally measured under widely different operating conditions.

Jan 1, 2014

By D. B. Mazzinghy, D. C. Rocha, H. B. Miller

"The use of ball mills for fine grinding is an inefficient process and has contributed to the increasing popularity of vertical stirred grinding mills in the minerals industry. Over the last decade, the performance and energy efficiency of stirred milling technology has become a preferred alternative to ball mills for fine and regrinding operations. The difficulty encountered in fine grinding is the increased resistance to comminute small particles when compared to coarse particles. Therefore, increased energy inputs are then necessary to raise the number of stress events in a mill to contribute to the comminution of fine particles. This work discusses the effect of operating conditions on the amount of fines produced and torque readings in a screw type batch laboratory vertical stirred mill. A time-based population balance model (PBM) was used to empirically analyze the performance of a vertical mill and to calculate mill breakage parameters for the different operating conditions tested. The results indicate the possibility of applying population balance model to the vertical stirred mill to predict product size distribution with acceptable accuracy. The obtained breakage function shows that the main breakage mechanism in this vertical stirred mill is by attrition, and that the selection function changes with experimental conditions within the mill. Higher agitator velocities are also seen to promote an increase in the degree of attrition between grinding media hence particle selection and fines generation increase.INTRODUCTION Stirred milling technology has been firmly established in the last 20 years as superior to ball mills for fine and regrinding operations due to its superior energy efficiency (Jankovic, et al., 2006). Stirred mills are now commonly used in many sectors of the mining industry, though they have been used in other industries for many years (Stehr & Schwedes, 1983). This technology has proven to be more energy efficient with greater opportunities for future optimization in both fine and coarse grinding."

Jan 1, 2018

By Rodney J. Hundermark, Sharif Jahanshahi, Shouyi Sun

"The major platinum producers in South Africa make use of electric furnaces for the melting of PGM bearing nickel - copper concentrates. To gain better understanding of the furnace operation, research was conducted at CSIRO Minerals in Melbourne, Australia. One aspect of the research project was the investigation of the factors affecting the electrical conductivity of melter type slags.Electrical conduction in slags can occur through two mechanisms: ionic and electronic. There is good understanding of the ionic mechanism. In slags containing high levels of iron, the dominant mechanism is electronic. There is limited understanding of the electronic mechanism and one of the aims of the research was to investigate this mechanism further.Experimental work was carried out on Al2O3.CaO.FeOx.MgO.SiO2 slags similar in composition to the melter slags. Conductivity increased significantly with iron oxide content. Above 20wt% FeOx, electronic conduction was significant and the conductivity varied with the oxidation state of the slag. As the iron oxide content was increased further, the electronic mechanism became more dominant. The conductivity reached a maximum at around pO2 = 10-7 to 10-4 atm., although this value was dependent on the total iron oxide content and basicity of the slag."

Jan 1, 2003

By L. Semushkina

Next generation flotation agents of KSK series for the concentration of complex copper-lead ores and the new ferromagnetic nanosized depressor of galena are introduced in this work. The feature of the KSK flotation agents is that they exhibit both frother and collector properties. KSK-6 can successfully substitute the widely used in Kazakhstani industry reagent ?-80 at the reduced consumption of butyl xanthate by 30 %. The new ferromagnetic nanosized depressor of galena, besides a low consumption rate of 100 g/t, also makes possible to exclude sodium sulfite (3-4 kg/t) and ferrous sulfate (5-6 kg/t) from the separation process, and receive high metal grade concentrates. Keywords: complex copper-lead ore, flotation agent, concentration method, ferromagnetic nanosized depressor

Sep 1, 2012

By B. P. von der Heyden, P. Neethling, M. Tadieb, L. Babedi

The effects of trace element substitutions in sphalerite mineral structure on optimised floatation response have, as yet, not been fully constrained or fully understood. To further this important field of study, this contribution focusses specifically on mineral and surface chemistry, and electro-chemistry of Cd- and Co- substituted synthetic sphalerites using Raman spectroscopy and Zeta potential experimentation. Raman spectroscopy illustrates that the presence of these impurities results in the introduction of a new mode, the relative intensity of which can be correlated (Cd r2=0.95 and Co r2= 0.99) to the dopant concentration. Comparison to X-ray Diffraction results measuring the unit cell parameter further shows that this relative intensity (Cd r2=0.81 and Co r2= 0.99) may provide insights into the degree of lattice strain within the mineral structure. The zeta potential distribution of an un-activated Cd-sphalerite show no detrimental effect as function of Cd content. Although the iso-electric point shifted from 2.45 at 1 wt.% Cd to 2.69 at 3.68 wt.% Cd, the zeta potential remained negative at alkaline media. Conversely, cobalt at low concentration of 0.36 wt.% had a detrimental effect on the surface charge, resulting to a close to neutral zeta potential at different pH. The adsorption of Cu ions on the surface of Co-bearing sphalerite conditioned in an alkaline media slightly increases the zeta potential of Co-sphalerite. While the Cd-bearing sphalerite decrease in negative zeta potential at >1 wt.% Cd indicating a complete exchange between Cu and Zn. The results presented herein illustrate that, based on the chemical nature of the substituting metal; sphalerite will exhibit multiple response to flotation reagents. Maximum recovery of zinc can thus only be achieved through multidisciplinary study and fundamental understanding of the effects of cation substitution on mineral structure and surface chemistry, the latter necessarily affecting the floatation response.

Jan 1, 2018

By S. Banisi, A. R. Hasankhoei, A. R. Ghasemi, E. Razi, G. A. Parsapour

At the pelletizing plant of the Gol-E-Gohar mining and industrial company two parallel dry closed grinding circuits, each with the average throughput of 300 t/h, are used. Each grinding circuit consists of a burner, a dry ball mill (6.2 m×13 m) and an air separator. The ball mill consists of a 2 m-long drying and an 11 m-long grinding chambers. The iron ore concentrate is fed to the drying chamber by a feed chute. The first 1.35 m of the drying chamber consists of 56 flights in two rows to decrease the feed moisture from 5% to below 0.2% and the rest of dryer chamber consists of deflectors to pass the material to the grinding chamber. It was found that when the feed moisture content increased from 1.3% to 3.5%, the throughput decreased by 12% (35 t/h) indicating a low performance of the dryer. Monitoring the wear rate of flights for a period of 12 months showed that the first 0.8 m length of the flights length did not experience any wear. This means that about 59% of flights do not contribute in material distribution and drying. A DEM simulation of feed chute and the drying chamber demonstrated that due to the inappropriate design of feed chute most of materials do not get in touch with the first 0.8 m length of the drying chamber. To overcome this problem, various feed chute designs with different geometries were simulated by the KMPCDEM© software. With the aim of arriving at a proper material trajectory, where the total length of the flights are used, a new feed chute was selected. The simulation results indicated that if the height of the flights is increased from 1.60 to 2.26 m and the slope is increased from 45 to 48 degrees the material arrive at the first 0.48 m of drying chamber. In this manner, the unused part of the drying chamber decreases from 59% to 36% of the length. After installation of the new feed chute, during a period of three months the throughput increased by 36 t/h.

Jan 1, 2018

By B. McFadzean, P. E. Ngoepe, P. P. Mkhonto, J. Taguta

The adsorption of heterocyclic collectors such 2-mercaptobenzothiazole (MBT), 2-mercaptobenzoxazole (MBO), 2-mercaptobenzimidazole (MBI) and their derivatives on pyrite form a basis in understanding the flotation reactivity that may be applicable in a wide range of sulphide minerals. This study uses a computational and experimental approach to determine the heat of adsorption of MBT, MBO, MBI and modified MBT collectors onto pyrite surfaces. Computational calculations found that the adsorption energies were in the order: MBO > MBI > MBT. The heterocyclic collectors were adsorbed in their thiolate form on the surface. In the case of the pyrite (100) surface, the MBT adsorbed through the exocyclic sulphur atom, while MBO and MBI adsorbed through the exocyclic sulphur and N atoms onto the 5-coordinated Fe atom. The (111) surface was found to be more reactive and different adsorption mechanisms were predicted, where the MBT exocyclic sulphur atom bridged on the 5- coordinated Fe and surface 2-coordinated sulphur atoms, while the N atom adsorbed on the 5-coordinated Fe atom. In the case of MBO and MBI, dissociation of the exocyclic sulphur atom from the collector occurred with subsequent interaction with the surface 5-cordinated Fe and 2-coordinated S atoms. This resulted in the collector carbon atom adsorbing on the surface 2-coordinated S atom, while the N atom adsorbed on the 5-coordinated Fe atom. The adsorption of the modified MBT was found to be more exothermic than the MBT, which showed that introduction of a –CS2 group on the exocyclic sulphur atom improved the affinity of MBT on the surface, and was thus a better flotation collector. The computational results were supported by experimental enthalpy of adsorption measurements and microflotation tests. The chemistry of the heterocyclic thioamides is complicated by the fact that they can exist in a number of tautomeric and ionic forms at different pH’s. This is discussed in relation to the flotation and calorimetric data.

Jan 1, 2018

By S. Castro, L. Uribe

Seawater can be considered as a particular process water with a high concentration of NaCl (about 0.5- 0.6 mole/L) and high concentration of hydrolyzing metal cations (mainly, Mg2+ and Ca2+ ions). Micro-flotation tests, induction time measurements, and zeta potential measurements have been used to investigate the effect of these ions on the natural floatability of molybdenite. The results demonstrate that molybdenite is strongly depressed in the alkaline pH range over which hydrolysis products of Mg2+ and Ca2+ ions are formed. At pH 10, colloidal magnesium hydroxide seems to be responsible for molybdenite depression in seawater and in Mg2+ solutions. This is also supported by the measurements of the effect of Mg2+ ions on the zeta potential of molybdenite. The mechanism of depression of molybdenite with Ca2+ ions is different, and depression takes place in the pH range were Ca(OH)+ complexes are formed, below the pH of precipitation of calcium hydroxide. Adsorption of the cationic hydroxy species and/or hetero-coagulation of the positive charged colloidal hydroxide on the negative charged molybdenite particles seem to be the main mechanisms involved.

Jan 1, 2014

By Kevin Davey, Liza Forbes, Leanne Smith

Given the global scarcity and value of potable water, interest in the use of water of lower quality in mineral processing has grown significantly in recent years. Previous laboratory batch flotation tests conducted at CSIRO have shown that chalcopyrite floats strongly without collector in distilled water and that the collectorless flotability of chalcopyrite is unaffected by the use of brackish water, sea water or hypersaline water. In contrast, bornite is moderately flotable without collector in distilled water but all three lower-quality waters have a detrimental effect on the recovery of bornite. The depressant effect is so strong that the little recovery achieved in these waters was only slightly above what might have been expected from entrainment alone. This work has now been extended to another important copper sulfide mineral, chalcocite. In contrast to chalcopyrite and bornite, chalcocite does not exhibit collectorless flotability so the chalcocite tests in this study were performed in the presence of a standard collector (potassium ethyl xanthate). The results reveal that chalcocite is flotable with xanthate in distilled water but the lower-quality waters have a detrimental effect on the recovery of chalcocite. This effect is partly reversed by increase collector additions. Further tests were completed in order to investigate the effect of the different ions present in the saline waters on chalcocite flotation. Possible reasons for the observed differences are discussed in terms of the pulp chemistry of the system.

Jan 1, 2014

By V. P. Yakushkin, B. S. Ksenofontov

"Multistage model designed and used for more detailed description of floatation process. The study develops a new model of flotation kinetics description. It defines flotation as process that consists of several stages: air bubbles and particles are separate, air bubbles and particles form a raising aggregate, aggregate raises to froth layer. This description significantly differs from commonly used model, which is much simplified. The multistage model gives an in-depth description and considers different aspects of flotation. Experimental approval of the new model resulted in its accuracy.The model is to be used for description of all flotation processes’ kinetics of wastewater treatment. It helps in accurate designing of flotation treatment plants and may be used for further research of flotation process. Columnar flotation installation was designed by using multistage model. This installation consists of new tubular aerators with special ejectors, froth pressing system as well as unit of thin-layering lighting to catch microflotocomplex “particle – bubble”. Usage of tubular aerators allowed to aerate the overall volume of pulp. Due to use of special ejectors with longer mixing camera we state higher volume of small-sized floto-active bubbles. Use of multistage model allowed to optimize and get higher technological results of potash salts enrichment. Tests were conducted on centrifuges-floatation installation system. Meanwhile, froth concentrate contained mainly thin hydrophobic particles sized circa 0,1 mm. As a result we set that during floatation cleaning process of froth concentrate 95-98% of chloride potassium (KCI) is derived from foam.The final product satisfies production quality. Columnar floatation installation productivity was 17 – 21 m3/m2h, which is a high technological result. Columnar floatation installation is one of the best examples of concentrating equipment using nearly all technological indices."

Jan 1, 2018

By Ibrahim Alp, Ersin Yazici, Oktay Celep, Haci Deveci

Low extractions (<80%) in cyanide leaching impose the application of physical and chemical pre-treatment methods (e.g., ultra-fine grinding, roasting, alkaline leaching) prior to cyanide leaching to achieve acceptable recoveries. The effectiveness of the selected pre-treatment method is linked intimately with inherent mineralogical properties of ore. In this study, a refractory silver ore assaying 145 g/t Ag was subjected to various pretreatment tests in an attempt to eliminate its refractoriness. Direct cyanidation of the ground ore (d80: 65 µm) produced a low silver extraction of only 29.5% over 24 h indicating its high refractoriness. Previous studies have shown that silver occurs mainly as Sb/As containing sulfide minerals such as pyrargyrite (Ag3SbS3), tetrahedrite (Cu12Sb4S13) and proustite (Ag3AsS3), which do not respond well to cyanide leaching. Also, silver-containing minerals are closely associated with and/or encapsulated in other mineral phases that can restrict the contact of cyanide with silver. Therefore, alkaline leaching (using 3 M of Na2S, NaOH or KOH solution) and ultra-fine grinding as pre-treatment methods were tested to improve the extraction of silver. All the alkaline leaching tests were carried out for 3 h at800C. Neither NaOH nor KOH leaching produced the desired effect on the extraction of silver (i.e., ~30%). Even, a sharp decrease in the extraction of silver (i.e., 10%) was observed in Na2S leaching. On the other hand, ultra-fine grinding (UFG) (d80: 3 µm) substantially improved the extraction of silver in cyanide leaching (95% Ag at 24 h after UFG). It can be inferred from these findings that the refractoriness of the ore is essentially physical in character (i.e. the encapsulation of silver presumably in non-sulphide minerals such as barite and quartz).

Jan 1, 2014

By E. Guerrini, M. Maccagni, J. Nielsen

"The solution for the treatment of the EAFD has not yet been fully achieved. Some of this dust has still not found an appropriate final destination. Large consortium treatment plants are quite expensive both in terms of investment and operating cost. Meanwhile, the tolling expenses for steel production companies are becoming very important, causing them to look for alternatives. Some steel plants are looking to close their production loop by internal treatment of their dust. Some years ago, Engitec began studying the coupling of the EZINEX® Process, an ammonium chloride electrolysis to recover the zinc contained in the EAFD, with the INDUTEC® Process, a pyro process based on an induction furnace that can convert EAFD into a C.Z.O. similar to the Waelz oxide. The combination of these two processes provides an alternative to the existing treatment options and is particularly interesting for relatively small capacities. In this paper, we would like to give the latest update about these two processes and their possible integration INTRODUCTION Zinc is contained in numerous wastes and secondary raw materials that can be thought of as high zinc concentrate mines. This is a very interesting source of Zn that is typically easily exploitable. Unfortunately, only a portion of these materials are currently processed to recover the metal value, while stabilized or unstabilized landfilling is often the final destination. Pyrometallurgical processes are mainly used to convert the zinc into crude zinc oxide (CZO). The various processes are very similar and characterized by the fact that the zinc bearing materials are usually submitted to a thermal treatment [1] in which the zinc is reduced, vaporized and re-oxidized producing CZO. This material not only contains zinc oxide, but also relatively high concentrations of heavy metals. Many potential CZO sources, such as electric arc furnace dust (EAF), galvanizing ashes, brass foundry and converters fumes also contain chlorides, fluorides and alkali metals that will transfer to the CZO. The classic example is the Waelz oxide [2]. This CZO is an intermediate product that must be transformed into zinc salts or zinc metal. Until now, the conversion to zinc metal is done through two main processes: the sulphate leaching and electrowinning system and the Imperial Smelting Process (ISP). ISP is facing a crisis for technical and economic reasons that has led to the closing of most of the existing plants. In any case, before being fed to one of these two processes, the CZO must be treated to eliminate or reduce some of the contained impurities. In particular, the halides are most harmful to these processes."

Jan 1, 2018

By E. Guerrini, M. Maccagni, J. Nielsen

"The solution for the treatment of the EAFD has not yet been fully achieved. Some of this dust has still not found an appropriate final destination. Large consortium treatment plants are quite expensive both in terms of investment and operating cost. Meanwhile, the tolling expenses for steel production companies are becoming very important, causing them to look for alternatives. Some steel plants are looking to close their production loop by internal treatment of their dust. Some years ago, Engitec began studying the coupling of the EZINEX® Process, an ammonium chloride electrolysis to recover the zinc contained in the EAFD, with the INDUTEC® Process, a pyro process based on an induction furnace that can convert EAFD into a C.Z.O. similar to the Waelz oxide. The combination of these two processes provides an alternative to the existing treatment options and is particularly interesting for relatively small capacities. In this paper, we would like to give the latest update about these two processes and their possible integration INTRODUCTION Zinc is contained in numerous wastes and secondary raw materials that can be thought of as high zinc concentrate mines. This is a very interesting source of Zn that is typically easily exploitable. Unfortunately, only a portion of these materials are currently processed to recover the metal value, while stabilized or unstabilized landfilling is often the final destination. Pyrometallurgical processes are mainly used to convert the zinc into crude zinc oxide (CZO). The various processes are very similar and characterized by the fact that the zinc bearing materials are usually submitted to a thermal treatment [1] in which the zinc is reduced, vaporized and re-oxidized producing CZO. This material not only contains zinc oxide, but also relatively high concentrations of heavy metals. Many potential CZO sources, such as electric arc furnace dust (EAF), galvanizing ashes, brass foundry and converters fumes also contain chlorides, fluorides and alkali metals that will transfer to the CZO. The classic example is the Waelz oxide [2]. This CZO is an intermediate product that must be transformed into zinc salts or zinc metal. Until now, the conversion to zinc metal is done through two main processes: the sulphate leaching and electrowinning system and the Imperial Smelting Process (ISP). ISP is facing a crisis for technical and economic reasons that has led to the closing of most of the existing plants. In any case, before being fed to one of these two processes, the CZO must be treated to eliminate or reduce some of the contained impurities. In particular, the halides are most harmful to these processes."

Jan 1, 2018

The traditional technological flow sheets for processing of ferrous quartzite (magnetite ores) al-low production of the iron concentrates with Fe content of 65%~68 % and recovery level about 55 %. The losses of iron with the tails of wet magnetic separation are related to hematite and quartz-magnetite particles, which are not extracted under low magnetic field employed. This work presents the results of the application of reverse cationic flotation for production of hematite concentrates with weak silica content from the tailings of wet magnetic separation of mag-netite. Fine particle size, complex mineralogy and presence of locked particles determine the impos-sibility of direct production of hematite concentrate by flotation or magnetic separation. The gravity concentration allows obtaining of iron concentrate from the well-prepared feed (size fraction -53+20 µm) but with very low recovery. Thus, hematite concentrates with weak silica content and satisfactory iron recovery were obtained by reverse cationic flotation, when it was fed with iron pre-concentrate produced by high gradient magnetic separation. The best flotation results were obtained by the use of formulations based on amines of different molecular structure that modulate the structure of adsorption layer, and favour a shifting of hydro-philic-hydrophobic balance on the surface of silicates with adsorbed starch and their preferential transfer into the froth product.

Jan 1, 2014

By T. Saastamoinen, N. Heino

"The Olserum deposit located in Sweden hosts an indicated mineral resource of 4.5 million tonnes over 0.6 % TREO, exhibiting a relatively high proportion of HREE. Beneficiation of a composite drill core sample was studied in the flowsheet of magnetic separation of magnetite followed by REE minerals flotation. Primary testwork was performed to select an effective REE mineral collector and then the parameters of grinding size, collector and depressant dosages, slurry pH and density, conditioning time and temperature, and flotation time were tested for optimization of REE flotation. The studies of process mineralogy showed that the REE-bearing minerals monazite, xenotime and apatite were successfully enriched from the concentrations of 0.6%, 0.31% and 2.6% in the feed to those of 17.0%, 8.9% and 65.0% in the concentrate with the recoveries of 79.0%, 81.3% and 71.0%, respectively. INTRODUCTION The Olserum deposit located in Sweden comprises lower grade placer material with higher grade apatite-magnetite veins and hosts an indicated mineral resource of 4.5 million tonnes at 0.6% TREO, with 34% of that being HREO (EURARE, 2017). The mineralization was studied by Andersson et al. (2018). At early stage, high-temperature REE is characterized by abundant monazite-(Ce) and xenotime-(Y) coexisting with fluorapatite and subordinate amounts of (Y,REE,U,Fe)-(Nb,Ta) oxides. During a subsequent stage, allanite-(Ce) and ferriallanite-(Ce) formed locally, partly resulting from the breakdown of primary monazite-(Ce). Alteration of allanite-(Ce) or ferriallanite-(Ce) to bastnäsite-(Ce) and minor synchysite-(Ce) at lower temperatures represents the latest stage of REE mineral formation. The mineralogy and beneficiation were firstly studied by GTK Mintec in the EURARE project for a composite drill core sample. The Olserum is considerably smaller than the Norra Kärr deposit. However, REE are hosted by xenotime and monazite, both of which have well established processing pathways, and meanwhile, the Olserum has a high contribution of the high value critical REE (dysprosium (Dy), yttrium (Y), neodymium (Nd) and terbium (Tb)), which provide a unique advantage for its exploration (Tasman Metals Ltd., 2013). In this paper, flotation of the REE minerals in the Olserum ore was studied."

Jan 1, 2018

By A. Ghadyani

This investigation was undertaken to assess the possibility of ash and sulfur removal by microbial action of high sulfur-content coal. Thiobacillus ferrooxidans and Thiobacillus thiooxidans have been used for biodesulfurization of coal. Feed samples were provided from Tabas coal mine located in Yazd province, Iran. The sample contained 28.80% ash and 2.30% sulfur. Flotation tests were implemented to optimize the effective parameters in these cells which were constant during bio-flotation tests. According to the results, obtained from various tests using Taguchi orthogonal array design (L27), the values of optimized parameters were pH at 7, 1000 g/t gas oil as a collector, 10% solid content, 15 min conditioning time, 100 g/t MIBC as a frother and 800 rev/min rotor speed. Bio-flotation tests are carried out by means of laboratory double discharge cell and mesophilic bacteria as depressant reagent using above mentioned optimized parameters. The bio-flotation experiments were conducted based on a Taguchi orthogonal array design (L9) with four variables (bacteria type, bacteria count, rotor speed of mixer and bio-conditioning time). The collected data was analyzed by using DX7.0, Minitab14.0 and WinRobust1.02 softwares for evaluation the effect of each parameter on the optimization criteria. Considering the highest combustible recovery and the lowest ash and sulfur content, the value of optimized bacteria type, bacteria count, rotor speed of mixer and bio-conditioning time were Thiobacillus ferrooxidans, 5×107 cells/g(coal), 100 rev/min and 20 min respectively. Under this condition, ash and sulfur content and combustible recovery were predicted 12.39%, 2.08% and 82.03% respectively.

Sep 1, 2012

By J. S. S. Allwin Ebinesar

The bioremediation of zinc was carried out using Pseudomonas alcaligenes, a Gram negative heterotroph. The parameters such as pH, bacterial cell number, initial metal concentration, and interaction time on the biosorption of zinc were studied. The maximum zinc uptake was found to be about 95% at pH 5 and biomass loading of 2.7x1010cells/mL. The biosorption isotherm for zinc exhibited Langmuirian behavior and the Gibbs free energy of biosorption was determined to be -31.2 kJ/mol, indicative of coordination of zinc with the functional groups on the bacterial surface. The adsorption kinetics followed a pseudo-second order equation. FTIR and EDAX studies confirmed the interaction of zinc with the biomass. The mechanisms of metal-microbe interactions are discussed.

Sep 1, 2012

By A. V. Bogdanovich

In diamond ores processing, final waste tailings size, rejected to dump, is one of the most important parameters. On one side, it is necessary to minimize losses of diamonds, whose size exceeds 1 mm, on the other side ? to provide for the plant high throughput and sufficiently low capital and energy costs, which is in greater part connected with disintegration process. Extensive laboratory, pilot-scale and commercial-scale dressability studies of different types of diamond ores have been performed at JSC ?Mekhanobr Engineering? in recent years. With that, special consideration was given to determination of the required ores? disintegration size that would provide for a high recovery of diamonds. In diamond ores processing, in order to exclude breaking of large diamonds, stage disintegration is used with regrinding of light fractions and heavy fraction X-ray fluorescent separation tailings. On account of rather weak bonds of diamonds with enclosing minerals, in crushing and grinding of diamond ores, selective disintegration takes place, with aggregates? breakup along plane surfaces of least bonding, which facilitates liberation of diamonds and their transition to free state. Heavy components losses with different sizes of final dump tailings were studied in processing of large samples. It was established, that in order to almost completely exclude losses of heavy components over 1 mm size, light fractions had to be ground to 2.5-3 mm size, while X-ray fluorescent separation heavy tailings of -15+3 mm size do not contain diamonds larger 1 mm in aggregates, and their regrinding does not increase total recovery of diamonds. On the basis of the conducted studies, relationships regarding heavy components and diamonds losses with respect to diamond ores final disintegration size were obtained, providing for more rational organization of the ores disintegration and processing flow sheet. Keywords: diamond, waste tailings size, disintegration process, recovery of diamonds

Sep 1, 2012

By Y. M. Zhao

Reutilization of waste printed circuit boards (PCB) can not only prevent potential environmental pollution, but also achieve recycling of secondary resources. Study on recycling of discarded PCB belongs to the front edge of environmental pollution prevention and resource recycling. In order to effectively crushing waste PCB, and solve the problem of secondary pollution of fugitive odor and dust during the crushing process, a wet impacting crusher was adopted to achieve comminution liberation of PCB in water medium. 96.79% of the crushed yield was distributed in ?2mm, and metal took 97.18% in this grade of production. Size distribution of PCB particles was characterized double peaks at the sizes of ?1+0.5mm and ?0.074mm. A double Rosin-Rammler function, is called DRR function, is put forward to describe the size distribution of PCB particles. The DRR function of cumulative weight percentage oversize of PCB was non-liner fitted by self-defining DRR function of the Origin 7.0. The evaluation indexes of the fitting results are the correlation coefficients R2 of 0.9994 and residual E of 0.18671, those show that DRR function is perfectly accurate. Based on the research the mechanical separation and material properties of PCB, a wet process of reclaiming metals from PCB using a new style separator ? tapered diameter separation bed (TDSB) in water medium was designed, and the related separation mechanism was studied. The fluid field of the tapered diameter separation equipment was simulated by the Ansys Flotran software, the variation laws of the velocity in each position in the fluid field as well as the equation of axial distribution sectional max velocity were analysed according to the simulation result, the stress change and motion trajectory of the pellet in the certain fluid field were analysed. The results show that the expanding tubular structure of the varied diameter separation bed indicates gradually decreasing velocity of water flow along the axis, assuming a certain angle in the bed, as a result of the gravity?s influence, and there was corresponding change to the distribution of the flow velocity, thus the whole formed a special fluid field where velocity variations exist in different positions. When the material passed through the fluid field along with the water flow, as a result of the difference to the particle density, the granularity and the shape, there would appear the difference to the motion trajectory as well as the movement distance under the action of the fluid: The lower density materials discharge along with water flow, but the higher density materials would be kept in bottom of the bed and discharge through material mouth. Therefore, light and heavy products were separated effectively according to the density. Using tapered diameter separation bed to process the ?1mm size crushed material of waste printed circuit boards, with the discharge of water 5.5m3/h, feed-rate of the material 250g/min and with an obliquity 35°, product with 93.92% in integration efficiency and 93.73% in recovery ratio of the metal were obtained by the primary separation. Compared with other mechanical methods, the range of particle size was broaden using the TDSB to recovery metals from PCB, and lower limit size of separation almost approach to 0. An innovative process of ?wet impact crushing+ classifying+ tapered diameter separation? recycling metals from waste PCB was developed.

Jan 1, 2014

By F. C. Araújo, T. Tavares, J. Leite

"This work presents the small-scale mining cluster of kaolin in Rio Grande do Norte (RN) and Paraiba (PB), both Brazilian states, including the following information: number of companies, process flowcharts, production numbers, mineralogical (XRD) and chemical (XRF) composition, granulometric distribution (screen and laser granulometer) and image analysis (SEM). Some social indicators in the region of the RN and PB States are presented in association with these data. The number of companies and their flowsheet were obtained through in situ visits and sample collection for technological characterization. The comparative study of the different flowsheets for kaolin production in the world was done using the databases and presenting the state of the art of kaolin processing. The results indicated that the mean feed typically contains 35-39% kaolin with quartz, muscovite and kaolinite as main mineralogical components and SiO2 (65.83%), Al2O3 (21.19%), K2O (3.9%), and Fe2O3 (0,63%) as main chemical constituents. The products of mineral processing are twofold, one between 74 µm and 37 µm, and the other smaller than 37 µm. The wastes of operation had major quantities of kaolin. The average Human Development Index (HDI) of the cluster region is approximately of 0.61, which shows an association between mineral processing plant and social indicators. The kaolin recovery, however, is between 30-55% for the three most common types of flowsheets that are currently used in the small kaolin mining cluster, indicating a need for technological improvement to achieve regional development. These data could be used incrementally to adapt the process plant currently used in the small-scale mining cluster of kaolin."

Jan 1, 2014