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By B. W. Zhao

Quantitative analysis of minerals composing in ore is primary in process mineralogy, a veracious quantification and analysis is very crucial to optimize or design a beneficiation process, especially for a low grade and complicated ore. This paper will discuss a SEM-EDS based quantitative analysis developed in JKtech Australia through an example from Jinchuan lean ore. For a low grade, com-plex intergrowths and texture lean ore, chemical phase analysis of value minerals and identification by optical microscope are very essential, unite the SEM-EDS based quantitative analysis, we can understand exactly the lean ore, explain and quantify the process performance.

Jan 1, 2014

By Y. Q. He

The dynamic behaviors of the air bubbles in the dense gas-solid fluidized bed have a significant effect on the performance of dry coal separation. The combined method of experimental measurement and numerical simulation were conducted to conduct the research of the mean diameters and rising velocities of the bubbles in the fluidized bed. The calculation models of mean diameter and rising velocity of the single bubble were proposed. The results indicate that the models of the mean diameter raised by Rowe (1976) and the rising velocity raised in this work could be used to predict the bubble dynamic parameters in gas-solid fluidized bed. With the Geldart B type of magnetite powder as the medium solids and while the gas velocity of 1.5Umf=U=2.2Umf, the mean bubble diameter along the bed height is 36mm<Db<45mm, and the mean rising velocity of the single bubble is distributed in 40~65cm/s. The results of experimental measurement, numerical simulation and model predication provide well agreements finally. Based on the uniform fluctuations of air bubbles diameters and their rising velocities, the separation experiments of 50~6mm dry coal using the mixture of 0.3~0.15mm magnetite powder and <1mm fine coal as medium solids were carried out. The results show that the probable error, E is 0.06, which indicates a good separation performance by using the gas-solid fluidized bed. Keywords: dense gas-solid fluidized bed, bubble dynamic behaviors, numerical simulation, separation performance

Sep 1, 2012

By O. Martinsson

The Kiruna area is an important mining province in northern Sweden, which is dominated by Fe- and Cu-Au deposits. Economically most important for the region, are the apatite iron ores with an annual production of c. 43 M ton of crude Fe-ore and a total production of more than 2000 M ton of ore the last 100 years. The apatite iron ores in the Kiruna area are dominated by either Magnetite or Haematite and contain varying amounts of apatite giving them a content of Fe and P, which varies between 30-70 % and 0.05-5 %, respectively. A typical geochemical feature of the ores is the strong enrichment of REE that is caused by a high content of REE in apatite and the occurrence of Allanite and Monazite containing 22.4 and 69.8 wt% REO, respectively. At Kiirunavaara, the content of REE in apatite varies between 0.07 to 1.57 wt% REO with a dominance for the light rare earths. The variation in REE-content of apatite depending on textural and paragenetic aspects is not known but apatite grains may display a strong LREE-depletion due to hydrothermal alteration. Monazite occurs as rod-shaped or tabular inclusions in apatite and is suggested, to have formed in response to hydrothermal alteration of apatite after the emplacement of the ore. Inclusions are mainly found in the central part of apatite grains occurring in veins and schliren, while they are rare in apatite occurring disseminated in the ore. Monazite also occurs as larger grains outside apatite and together with Allanite is found in texturally and paragenetically different settings within the ore. These occurrences of REE-minerals may largely be a product of LREE mobilized by alteration of apatite after the emplacement of the ore. However, REE-minerals including Allanite and Monazite might also have formed directly from late magmatic fluids. Keywords: apatite, monazite, allanite, ree, kiirunavaara, iron ore of kiruna type, mineral chemistry

Sep 1, 2012

By Lina Chica, Arturo Barrientos, O. Bustamante

Hydrocyclone is a device commonly used in mineral processing industry. Underflow control plays a fundamental role in hydrocyclone operation. This affirmation supports the fact that hydrocyclone underflow has effect in some aspects of separation performance like capacity, split ratio, cut size and bypass. Hydrocyclone operation state is associated to underflow characteristics: air core formation and discharge shape. Many studies attempt to understand size separation phenomenon and the discharge influence but none of them has taken an energy point of view. This work presents the results of a mechanical energy dissipation for hydrocyclone operation from a mechanical energy balance. The experimental results related to Newtonian suspensions show that underflow energy dissipation does not control the operation because this magnitude is small compared to interior energy dissipation. However, discharge energy dissipation provides enough information to describe underflow conditions and its influence in separation conditions. In the modelling non dimensional parameters have been considered for hydrodynamic description and for geometrical and operation hydrocyclone characteristics. Energy dissipation from the continua media approximation results into a relevant concept to understand the hydrocyclone performance and improve industrial installations.

Jan 1, 2014

By M. L. Cao

In this study, a montmorillonite organo-intercalation compound (MOIC) was synthesized by using a Na-modified bentonite (NaB) as a matrix and hexadecyltrimethylammonium (HDTMA) bromide as an intercalating reagent under microwave irradiation. The synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), organic carbon content measurement, and adsorption density determination. The results show that, at 10% suspension concentration and 10 minutes irradiation in a 130-W microwave oven, the basal spacing d(001) of the synthesized MOIC increases to 2.209 nm from the original 1.218 nm of NaB. The MOIC has much higher adsorptive densities to nitrobenzene and aniline from aqueous solution than the NaB. The adsorption isotherm of nitrobenzene on the MOIC is linear, and the adsorption is mainly the result of nitrobenzene?s preferred partition in MOIC over aqueous solution due to MOIC?s hydrophobicity. The adsorption isotherm of aniline on MOIC follows the Freundlich equation and the increased adsorption is not only the result of aniline?s preferred partition in MOIC over aqueous solution but also that of the MOIC?s surface adsorptions.

Jan 1, 2014

By W. D. Guo, Y. M. Zhu, B. B. Luo

The main chemical constituents of waste cooking oil are higher fatty acid glycerides, which can be used to produce anionic fatty acids for most non-sulfide flotation. However, using the mixed fatty acids (MFA) produced by waste cooking oil as collectors directly, the flotation effect is usually not satisfactory, especially at lower temperature or room temperature. There are very rare systematic studies about the reason for poor flotation performance of waste cooking oil. This study aims to investigate the flotation and adsorption characteristic of different types of fatty acids in waste cooking oil to find out what kind of fatty acids results in the poor flotation performance. This will provide technical supports and theoretical guidance for the waste cooking oil application in the field of mineral processing. In this study, MFA were produced from the waste cooking oil, and then separated into saturated fatty acids (SFA) as well as unsaturated fatty acids (UFA), which possessing different flotation properties. The properties of the MFA, SFA and UFA were analyzed by iodine value, melting point measurement, Fourier transform infrared (FT-IR) spectroscopy and quartz micro-flotation tests. The results showed that UFA was composed of fatty acids containing group—(CH=CH—CH2)n—, having an iodine value of up to 162.90, a melting point as low as -17.3 ? and stronger low-temperature floatability. In contrast, the SFA was made up with saturated fatty acids and a few oleic acids, with an iodine value of 48.97 and a melting point of 38.8 ?. SFA had shown poor collectability and required a flotation temperature higher than 35 ?. The results of zeta potential measurements, solution chemistry calculation and FT-IR spectra revealed that both UFA and SFA can be adsorbed on the quartz surface activated by CaCl2 via the chemical and hydrogen bonding. The reason MFA having a poor flotation performance is the SFA has an extremely high melting point which affecting the dissolution of the dispersion.

Jan 1, 2018

By E. Scheepers

Within a phosphorus producing submerged arc furnace it was found that the continuous fluctuation of the furnace between a flowrate-driven state (high throughput) and a thermodynamic-driven state (low throughput) caused both techniques to have similar overall, predictive abilities and resulted in a linear, ARX-type, adaptive prediction model as the model of choice. Secondly, this pre-diction model was developed, tested and then shown to have a reasonable, 8-hour-ahead predictive accuracy (R2, coefficient of determination) of 30% (±6%) on future Pslag values. This inherent relationship exists because, at the precise moment of a Pslag prediction, the furnace already contains the metallurgical memory (input variables to the linear model) needed to ensure that some predictive possibilities will always exists - all as a result of the long residence times in the furnace. Residence time, however, is not a directly adjustable variable but rather a fully dependent variable and a function of an array of interconnected and interactive variables. In fact, this applies to virtually all input variables, reemphasising the importance of innate metallurgical memory. Thirdly, predictive control possibilities were explored by simulating the set-points of two fully independent variables used by operators to control the process: the ratio of fixed carbon-to-P2O5 and the ratio of silica gravel-to-pellets. This linear, predictive control model showed only a slight improvement with an 8-hour-ahead predictive accuracy of 35% (±7%). This highlights how ineffective current adjustments are in optimally steering the process and how difficult even incremental improvements in feed-forward and predictive control can be. Finally, it is shown that fundamental design-, sampling- and process restrictions currently associated with the process will always limit the predictive and especially control accuracy or meaningfulness of any dynamic model. These restrictions include the size of the furnace resulting in long residence times, 8-hours sampling intervals, an extremely complex and interactive process and a 16% spatial analyses variation on the Pslag values ? the very value that the model is to predict. The point is made that, given the current status quo, even the perfect dynamic prediction model can not improve on an 8-hour-ahead prediction of 30% (±6%). This barrier can only be pierced with e.g. tidier and more frequent sampling regimes and other upfront capital investments, a decision that becomes a cost accounting exercise and that can only be taken by the management structure. An investment demanding ever-increasing attention is CFD software and it?s potential to shed more light on the complex interactions within the furnace.

Jan 1, 2014

By Z. M. Wang

A large scale a polymetallic mine in north China is a refractory ore containing many useful com-ponents: W, Mo, Cu and Fe. Mineralogical investigation shows that the deposit is a quite complex one due to fine disseminated size and unevenly distribution of valuable, intergroth of sulphide and tungsten minerals, concurrence of scheelite and calcium minerals. Based on ore characteristic, a flowsheet is used by the floatation processing of sulfide minerals superior to scheelite. Bulk sulphide flotation is used in sulphides. Mo and Cu are floated in sequence after sulphides regrinded. Tungsten mineral is floated using combined depressant that is an effective depressant to gangue, and can improve the grade of rough tungsten concentrate. Compound depressant has high effective in removal of collector in gangue and sulphide, and tungsten is activated also. High quality of tungsten concentrate is obtained at satisfactory recovery. The test production obtains Mo concentrate with grade of 48.16%, recovery of 81.43%; W concentrate with grade of 66.47%, recovery of 78.19%; Cu concentrate with grade of 23.14%, recovery of 56.6%; Fe concentrate with grade of 67.33%. The valuable metals are recovered comprehensively and well techno-economic index is obtained. The mine enterprise profit is increased greatly.

Jan 1, 2014

By Ingvar Ymén, Anders Sandc, Jan Rosenkranzc, Lisa Malma, Ann-Sofi Kindstedt Danielssonb

The understanding of particle surface properties is essential for the study and evaluation of froth flotation phenomena, particularly in the investigation of various chemical or reagent effects. Dynamic Vapor Sorption (DVS) is a method used for the analysis of surface properties of powders for instance in the pharmaceutical industry. To the knowledge of the authors, it has however not been used before in applications related to mineral processing. The DVS technique involves measurement of the water uptake of a relatively small amount of sample as a function of the relative humidity (% RH) in a temperature-controlled environment. The purpose of this work was to evaluate the method and investigate how it can complement existing techniques for surface characterization in mineral processing. Four samples (feed, CuPb concentrate, Cu concentrate and Pb concentrate) from the Cu – Pb flotation process in the Garpenberg concentrator, Sweden, were analyzed by DVS and the traditional capillary absorption technique (Washburn capillary rise). This enabled comparison between the two methods and evaluation of their respective advantages and disadvantages. Both methods give the expected ranking of the hydrophobicity for CuPb concentrate, Cu concentrate and Pb concentrate, but a discrepancy was observed for the feed. Washburn gave a value for the contact angle which was in the same range as for the CuPb concentrate, whereas DVS gave a value for the moisture uptake which was much higher than for the CuPb concentrate. Thus, DVS ranks all samples correctly, but with an unexpectedly high value for the feed whereas Washburn gives good ranking for three samples out of four. Potential reasons for the discrepancies are discussed.

Jan 1, 2018

By T. Wallmach, S. B. Blancher, A. Delaporte, P. Goncalves

"Fe-Ti oxides concentrates produced from heavy mineral sand deposits are widely used for the production of titanium dioxide pigments that are critical components of white paint, plastics and paper. According to mining industry, the Fe-Ti concentrates mostly consists of three phases: ilmenite, leucoxene and rutile. However, a few mineralogical studies have shown that the variety of Fe-Ti oxides found in sand deposits is far more complex, mostly due to alteration processes. The aim of this contribution is to characterize in detail by means of Qemscan analyses the mineralogy of the three main concentrates (ilmenite, leucoxene and rutile) produced by the Grande Côte Operation (GCO) mineralurgical plant in Senegal. The ultimate goal is to characterize the different products and textures formed during the natural ilmenite alteration processes, to localize the phases carrying the main impurities (Cr and P), and finally to determine the physical properties of each mineral component to improve metal recoveries. Along alteration processes, Ti content increase. Ilmenite (FeTiO3) is progressively transformed into pseudorutile (Fe2Ti3O9) particles which could also be altered and transformed into hydroxylian pseudorutile [FeTi6O12(OH)3.3H2O] or complex blends of anatase microcrystals (TiO2). These transformations are accompanied by significant changes in particle textures. Microporosity and fractures appear and the impurity content also increases. Anatase rich microcrystal assemblages, so far described as Leucoxene, could be identified to consist of grains with higher porosities, water contents and higher intrapore impurities. These particles are the main carriers of chromium and phosphorus. The observed mineral transition textures have a significant impact on the ore dressing processes. During these transformations, the physical properties of these phases change, the magnetic susceptibility as well as densities decreases, due to the increase in porosity. The separation of particles, especially those with high porosity will help improving the GCO mineralurgical plant performance and to reduce the impurity contents in finals products."

Jan 1, 2018

By Liu Yong

A complex rare metal ore, containing various valuable elements is used in this study. The mineralogy results indicate that the mineral composition of the raw ore is complex, and there are more than thirty-eight kinds of minerals in the raw ore, and the elements, such as Nb, Ti, Fe, REO, Be etc, always form isomorphism relationship. The REO content of the raw ore is 0.45%, and the contents of other rare metals Nb, Ta, Ti and Zr are 0.33%, 0.02%, 0.93% and 2.00% respectively, and the main gangue elements are Si and Al, and their contents are 71.84% and 8.5% respectively. The beneficiation-metallurgy combination process of ?preconcentration-reduction and magnetic separation-acidification and leaching-precipitation? is used to treat the raw ore. The preconcentration of raw ore is realized through high intensity magnetic separation, and the magnetic field intensity is 1.0T, and the rough concentrate with 2.88% REO and 1.95% Nbresidue can be obtained, and the iron recovery is 92.83%, and the REO recovery is 95.87%, and the Nbresidue is treated by hydrometallurgy process of ?acidification-leaching-precipitation?, then the rare earth oxide, niobium concentrate and zircon-bearing residue can be obtained, and the REO recovery is 80.10% and the Nbresidue and the gangue obtained from the high intensity magnetic separation process is separated by gravity separation, and then the zirconium concentrate can be obtained. The indexes of the beneficiation-metallurgy combination process used to treat the complex rare metal ore are as follows. The REO content of the rare earth oxide is 92.58% and the recovery is 58.44%. The Nb2O5 and 27.42% TFe can be obtained. Iron in rough concentrates is removed after reduction and low intensity magnetic separation, then the iron powder with Fe content over 88% and nonmagnetic rare-metal 2O5 recovery is 94.77%. The rare-metal 2O5 recovery is 80.04%. The mixture of the zircon-bearing 2O5 content of niobium concentrate is 28.34% and the recovery is 54.02%. The ZrO2 content of zirconium concentrate is 28.43% and the recovery is 52.35%. The TFe of iron powder is 89.53% and the recovery is 78.13%. Keywords: rare metal ore, separation and extraction, beneficiation-metallurgy combination, comprehensive utilization

Sep 1, 2012

By M. Kinnunen

Handling of municipal solid waste (MSW) and control of its potential resources is becoming increasingly important in modern society. The OECD (Organization for Economic Co-operation and Development) average on municipal waste produced in 2003 was that of around 570 kg per inhabitant. In European Union countries around half amount is of MSW landfilled. In Finland still 88% of MSW was landfilled in 2004. Since incineration reduces MSW volume significantly while producing heat energy, it has become one of the most common waste handling techniques. The shortcoming of incineration is however, that incinerated MSW is often not pre-sorted and it produces slags and ashes as side streams from which recovery of metals is difficult. This paper looks into possibilities of scrap metal recovery for recycling from municipal solid waste incineration (MSWI) bottom ash. In order to do that, a flow sheet of physical separation methods was developed and tested with Finnish rotary furnace MSWI bottom ash. In addition, an empirical model for estimation of the recoveries of scrap metals with physical separation methods for treatment of MSWI bottom ash was developed. According to the results of this study, for 1 Mt of incinerated MSW with 30% mass reduction, a minimum resource potential of 100 kt for magnetic metal scrap of roughly 24 % grade and about 19 kt of non-magnetic metal scrap of roughly 65 % grade. In other words, 57 kg magnetic scrap and 12 kg non-magnetic scrap per inhabitant at the mentioned grades, respectively. Although wide variations of parameters affect the MSWI bottom ash quality, it can be said that a considerable amount of metals is drained into MSWI bottom ash. Results of this study show that from MSWI bottom ash significant material streams metal scrap can be reintroduced into the resource cycle which would otherwise be lost.

Jan 1, 2014

In looking to the future of mineral processing the focus is typically on improved processing units. Basically it is a search for an elusive wonder machine that could revolutionise the economy of mining: the sorter that strips 50% of the ore with only a few % loss of value; the comminution device that uses 5% of the energy while producing fully liberated particles; or the recovery device capable of producing a 99% recovery at 99% grade. These aspirations are propounded against a reality backdrop of sorters rusting in back yards, mill throughputs below design and varying by 30%, cyclones flaring and cut-sizes fluctuating, mediocre recoveries and soaring processing costs. This disconnect between aspiration and reality appears, to these authors at least, to be a mighty chasm. Moreover, it remains one over which we are expected to magically leap rather than methodically bridge. Indeed one may be forgiven for thinking that should such a wonder machine come along, taking advantage of it would be highly improbable. Questions would inevitably emerge on how to feed the correct material, how to cope with the wide variability of feeds, how to control such advanced equipment and how to handle the new product from such a machine. It is likely these questions might lie unanswered, or more regrettably, unasked. It is generally accepted that as an industry we are exceedingly unlikely to teleport from the current status quo to an entirely new reality in a single flash. It is our thesis that the probability of these magical machines materialising is remote, and even if they miraculously appeared, we simply wouldn?t know what to do with them. Rather, it is our contention, that a step change will only arise through a staircase rather than from a single giant leap. We should focus on building those steps and linking them together into a firm structure ? a workable mineral processing circuit. This paper addresses the alternative of a coherent set of modest but significant improvements, integrated to produce the step change we desire: essentially, a reduction of processing energy to below 40%, which we believe is achievable without recourse to any mystical machines. A key underlying capability to designing these dramatically improved processes, is the weaving of independent process models into a coherent circuit simulation, in order to design the new generation of mineral processing circuits. Keywords: step change, circuit design, circuit simulation, energy reduction

Sep 1, 2012

By Z. Naziemiec

Since several years in Poland a huge demands on mineral aggregates occur, for the reason of intensive development of housing and road industry, as well as industrial building. Limitations in re-sources of broken aggregates in Central and Northern parts of Poland cause, that both the non-waste production of aggregates with high quality and the production of alternative aggregates from recycling gain greater importance, nowadays. It entails increase in demands for crushing devices, which are easy and reliable in operating as well as inexpensive and enabling to obtain a good quality products. Jaw crusher, regarded as the most spread in Polish industry, meet these requirements, however, their crucial disadvantage is a large content of irregular grains in crushing products. Numerous investigations show, that the shape of grains is a significant feature of aggregates, which influences on durability and quality of produced concretes. The advantage of jaw crushers is their easy operation, low price as well as low amount of dusts (wastes) generated in comminution products in comparison to other types of crushers (i.e. hammer crushers).

Jan 1, 2014

By Z. C. Shen

As core part of flotation column, aerator has been always priority research. A new type of porous aerator made of stainless sintered microcellular material is designed , which diameter is between 20µm to 40µm. High bubble surface area flux is obtained at low air pressure 20kPa by this type of aerator in water. In order to extend its applied range ,experiments were carried out in alkali slurry (pH=12) , resulting with porous aerator clogged after working 20 days . Sampling the cross-section of aerator detected by microscope and X-ray diffraction ,the reason clogging was found. Then plugging aerator was reactivated after putting it in acidic liquor treated by ultrasonic for about ten minutes. On-line aerator maintenance can be done in no down time , and it can be repetitive-used after recovered ,so reduced capital costs.

Jan 1, 2014

By P. Fecko

The objective of the paper was application of bacterial leaching on two brown coal samples from locality Mine Druzba, seams Antonin and Josef (Sokolov brown coal basin, Czech republic). Based on the results of bacterial leaching and petrologic analyses of the given samples, it is possible to say that application of bacterial leaching gived good results. Applying bacterial leaching it is possible to remove from 34% to 47% of total sulphur and from 45% to 64% of pyritic sulphur from the coal.

Jan 1, 2014

By H. C. E. Regidor, M. G. Mena, H. D. Mendoza

Cyanidation leaching has always been the most widely used method of extraction of gold in the world. Its low cost and high selectivity has made it the prevalent choice for mining companies, and even for the small scale miners. The use of cyanidation in small scale mining has been an issue for the longest time, mainly due to the operation’s lack of safety measures, health care or environmental protection regulations. In pursuit of more environmentally friendly methods of extraction of gold, several alternative extraction processes have been explored, one of which is chlorination. The chlorination process is advantageous when recovering refractory gold locked in sulfides, as it simultaneously oxidizes the surrounding sulfides as well as dissolve any gold exposed to the lixiviant. This research was conducted to study and develop a safer alternative way of extraction of gold from small scale mining operations, without compromising the recovery of gold. In this study, a variation of the chlorination process has been employed for a refractory flotation concentrate wherein the majority of the gold is locked in sulfides. Hypochlorite-bearing reagents were used as the leaching reagents, and the method developed was a 2-stage leaching process in differing pH conditions. The solution pH and Eh was monitored all throughout the runs, and aliquot samples were taken at time intervals for analysis. SEM-EDS imaging was used to determine the mode of oxidation of the chlorination process, and the image obtained showed that the oxidized layer followed the shape of the particle, suggesting a diffusion controlled process. XRD analysis of the sample before and halfway through leaching further confirmed the oxidation of the sulfides. The amount of gold dissolved in the aqueous solution and in the solid residue were used as the basis for the determination of the recovery of gold. An average gold recovery of up to 84.38% was obtained using the developed method in just 7 hours of leaching. This method was then employed for a pilot-plant scale test and a gold recovery of 79.2% was obtained.

Jan 1, 2018

By Rhulani F. Maluleke, Francis W. Petersen, John H. Marsh, Johann de T. Steyl, Allan Nesbitt

"Pressure leaching of chalcopyrite and nickeliferrous pyrrotite at temperatures between 105 and 200 ºC has been proposed as a potentially viable route for the extraction of mineral elements from sulphide concentrates. In general, these concentrates contain iron, and the economic success of the processes is partially dependent on the choice of the environmentally acceptable iron-removal technique. One of the most widely used methods for the removal of iron from sulphate liquors is precipitation as hematite, goethite, or jarosite. The nature of the iron precipitate formed dictates downstream dewatering and residue treatment and disposal options. However, a better understanding of iron precipitation under the defined process conditions would consequently be of benefit in process design and optimisation.This study investigated the precipitation of iron in the autoclave at temperatures between 105 and 200 ºC. The effects of temperature, acid concentration, iron concentration, and the presence of other metal cations on the nature and composition of the precipitates were determined."

Jan 1, 2003

By P. Pourghahramani

Several structural characteristics change during intensive milling such as chemical composition, phase transformation, crystallite size, lattice strain, lattice parameter (s) and solid reactivity etc. The creation of defects enhances the stored energy (enthalpy) in the solids and consequently causes a decrease of activation barrier for the process and/or subsequent processes. In this paper, the effects of milling on the structural changes of hematite have been investigated using dry millings. The structural changes have been characterized using a combination analysis of BET surface area measurements and X-ray diffraction (XRD) analysis. Besides, the hydrogen reduction behaviors and kinetics of mechanically activated samples and initial sample were studied using simultaneous thermal analysis (STA). The methods of Williamson-Hall and Warren-Averbach were used for analyzing of XRD patterns to resolve and extract the microstructural characteristics of hematite phases. It was concluded that the breakage and aggregation of particles take place mainly in the starting and prolonged stages of dry grinding, respectively. The BET surface area enlarged steadily over the grinding processes whatever milling methods were utilized. The characterization of structural changes revealed that the hematite milled under various conditions did not undergo any significant reaction or phase transformation during milling processes. In addition, X-ray amorphous phase con-tent increased gradually with extending the grinding intensity. The maximum X-ray amorphous phase exceeds about 81% after 9 hours of milling in both tumbling mill and vibratory mill. The Williamson-Hall plots revealed the anisotropic character of line broadening for deformed hematite and changes in the trend of microstructural characteristics as a function of milling time. It was found that the surface weighted crystallite size decreases and lattice strain increases over the grinding periods. The minimum surface weighted crystallites were calculated about 17.3 nm, 12.2 nm for the products of tumbling and vibratory mills respectively. The maximum lattice strain,, in the grinding with tumbling and vibratory mills was calculated about 4.44×10-3 and 3.95×10-3respectively. 21/210nmLe=<> The non-isothermal kinetic analysis of the products revealed that Fe 2O3 reduced to Fe in a two-step process via Fe3O4. Intensive grinding resulted in improved resolution of overlapping reduction events. It was also established that the mechanical activation had a positive effect on the first step of reduction. The prereduction step in the activated samples initiated and completed at lower temperatures than that in non-activated samples. The activation energy of reduction decreased at the first step of reaction with increasing the grinding intensity. Intensive milling increased slightly the average activation energy of the second step of reduction due to the present of finely agglomerated particles and intensive sintering of the particles in higher temperature ranges.

Jan 1, 2014

By R. Marandi

Biosorption of heavy metals can be an effective process for the removal of heavy metal ions from aqueous solutions. In this study, the adsorption properties of nonliving (boiling in NaOH) biomass of phanerochaete chrysosporium. For Pb (II) and Zn (II) were investigated by using batch adsorption techniques. The effects of initial metal ion concentration, initial pH, biosorbent concentration, stirring speed, effect of temperature and contact time on biosorption efficiency were studied. Experimental results indicated that the uptake capacity and adsorption yield of one metal ion were reduced by the presence of the other metal ion. In the experiments the optimum pH value was found out 6.0. The experimental adsorption data were fitted to the Langmuir and Frundlich adsorption models. The highest metals uptake was calculated for Zn (II) and Pb (II) were 57 and 87 respectively. desorption of heavy metal ions was performed by 50 mM HNO3 solution. The results indicated that the biomass of p.chrysosporium is a suitable biosorbent for removing heavy metals ion from aqueous solution.

Jan 1, 2014