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Considerable attention has been, and is being, given to the physics of water-films associated with bubble interactions at surfaces. In contrast, little information on the chemistry of such films has been reported. This communication reports a method using sum frequency vibrational spectroscopy (SFVS) to describe hydrogen bonding of interfacial water molecules in water films created with bubbles at hydrophilic and hydrophobic surfaces. The SFVS spectra of water films at hydrophilic silica surfaces differ significantly from the spectra of water at a hydrophobic silica surface. The SFVS spectra indicate that a very ordered water structure exists in water films at the hydrophilic silica surface during contact with a bubble and that the extent of hydrogen bonding increases with an increase in contact pressure. Such structural considerations as well as repulsive electrostatic and Van der Waals forces account for film stability for a bubble at the hydrophilic silica surface. In contrast, the SFVS spectra of water at a hydrophobic silica surface show a lack of hydrogen bonding and are characterized by a distinct absorption at about 3700 cm-1 similar to the spectrum of the air/water interface. These results suggest the presence of a water void, or water exclusion zone, at the hydrophobic surface, as supported by X-ray reflectivity measurements reported in the literature, by atomic force microscopy, and by the results from molecular dynamics simulations. Of course the water film at the hydrophobic surface is unstable with film thinning and rupture upon bubble contact. Under these circumstances it is shown that an attractive Van der Waals force between the bubble and the hydrophobic surface can be expected when the water exclusion zone is taken into consideration. As the thickness of the water exclusion zone increases to a thickness corresponding to the size of nano bubbles, the calculated attractive Van der Waals force increases. This analysis may help to explain the so-called ?short range? and ?long range? hydrophobic forces. Keywords: SFVS spectra, hydrophilic silica surface, hydrophobic silica surface

Sep 1, 2012

By S. H. Morar

Froth flotation is a physico-chemical separation process that takes place in two phases; pulp and froth phase. It is widely recognised as a complex process, due to the range of interactions present within the system. Of critical importance is the role of the froth phase within the system. The pulp kinetics governs the maximum potential recovery within a flotation cell, while the froth phase governs the selectivity via the froth?s stability. Higher froth stability improves recovery at the expense of grade, and lower froth stability improves selectivity. It is well known that the two major factors affecting froth stability are attached particles and solution chemistry. This paper looks at a flotation bank at different froth depth and frother concentrations. The air recovery to the concentrate is determined at each condition and relates the effect of the operating conditions on froth stability and transport to the amount of solids that are recovered to the froth and concentrate by true flotation. The results presented show that, for a given process objective, which in this case was a consistent mass pull profile, depending on the operating conditions, solids recovery in the pulp is affected by the air rate required to maintain the target mass pull. To a smaller extent, the changes in the pulp composition affect down-stream pulp recovery. The variation in solids recovered into the froth drives the froth stability at the start of the flotation bank, while the frother drives the froth stability at the end of the bank. The performance in between these two extreme conditions arises from an interaction of these two effects. The consequences of these interactions can give rise to counter-intuitive responses that can confound efforts to optimise the performance of the bank.

Jan 1, 2014

By Lei Wang, Qi Zheng, Xiao-kui Che

"The wastewater emitted by gold chemical industry contained vast of different heavy metal ion, such as Zn, Cu and Ni etc. Among them Zn is the main ion in the waste water which causes the serious environment pollution. A method of preparing a kind of resin which is used for the removal of Zn by magnetic adsorbent was developed and was applied in practice. This adsorbent is a chitosan made of a kind of Fe3O4-chitosan modified by epichlorohydrin. The adsorption capacity of the absorbent and it was concluded that under the laboratory conditions, the maximum adsorbing capacity of this adsorbent could be 287.58 mg/g. The absorbent was also applied in the wastewater emitted by a gold industry in Shandong province. Its performance was tested and the result showed that the concentration of Zn ion in the wastewater was reduced from 0.58 mg/L to 0.0174 mg/L. What is more, the adsorption rate could be more than 97% when the dosage was 100L/m3 after adsorbing for 1h. KEYWORDS Selective, preparation, laboratory experiments, industry experiment, comparation INTRODUCTION Currently, most gold chemistry use cyanide to leach gold ore. Many different metals participate to this reaction besides the gold ion in this processing, so that the composition of the water is very complex. The waste water emitted by gold chemistry industry contains large amount of heavy metals. Definitely, if it was discharged without any treatment, the water would threaten the environment. The recuperation of any ion in the water would mitigate the pollution. Ion exchange resin, which is an effective material to do the water treatment with low cost, became widely applicated in this field [Yu-jiao Wang,2013]. Different kinds of resin were developed and the influence factors such as pH, adsorption properties and selectivity for different ions were investigated [CA Cruz et al,2018; PawanKumar et al.2016; Y Zhang, et al,2010; and ShengingSun, Aiqin Wang, 2006;]. The waste water mentioned in this article has a high Zn concentration, so a magic resin for Zn adsorption selectively we designed was used to manage this water. And the recovery of Zn could not only contribute to pollution abatement but also a best way to settle a dispute to the short of Zn resource. So the article mainly describes the preparation and the application of a kind of magnetic adsorbent used for the removal of Zn both in laboratory and industry. The aim of this article is to compare the effect of this resin in industry and laboratory?"

Jan 1, 2018

By H. L. Liu

With the exploitation of mineral resources, valuable minerals are more and more finer and poorer. Priority reclaiming liberation grind particle under rough grinding, will help to pervert loss of melts, raise dewatering efficiency of concentrate, reduce consumption of reagent. And it is propitious to reduce energy consumption and raise the utilization rate of resources. With the feature of coarse particle?s desorption and deposition, CLF flotation machine has special pulp circulating way, which is not only apply to treat coarse particle but also normal size particle. The paper advanced the history, the design principle, the structure feature and the application of CLF flotation machine.

Jan 1, 2014

By R. Roufail

In this paper, the effect of different operating parameters of high speed stirred mill on the particle breakage mode is addressed. Morphological features of broken particles is investigated and related to the types of forces generated in the mill using Discrete Element Method (DEM). The stress intensities generated in the mill are varied by changing the agitator speed. The investigated agitator speeds were 1000, 1500, and 2000 revolution per minute (rpm). The minerals considered in this study are hard minerals (quartz) and soft, sulphide minerals (galena). The morphological features examined are roughness, roundness and elongation, which shed light on the mode of breakage during the grinding process. Particles that are rough, less round and elongated would imply that they broke via fracture, along their grain boundaries. On the other hand, the smooth, less elongated particles would mean breakage occurred across the grain, which is abrasion mod. DEM study complemented the understanding of particle breakage mechanism via tracking the types of forces applied on the particles. Normal forces imply compressive loading, which is presumed to impose fracture breakage along the grain boundaries, whereas tangential forces imply abrasion loading. Stirred mill grinding has been regarded as an attrition/abrasion process, whereas, this study showed that about 60% of total particles that are morphologically analyzed for both minerals were rough particles. Such an observation indicates that the fine product, which contain a significant amount of progeny from the coarse fractions are consistently broken via fracture. The morphology results agreed with the DEM findings, which indicated that the agitator speed, mineral type, and residence time would dictate the type and mode of particle breakage. Keywords: DEM, high speed stirred mill

Sep 1, 2012

By M. Vulkov

The paper is focused on the optimal selection of grinding medium for a drum mill. The decision-making is based on the fuzzy multiple attribute approach. One way to optimize the grinding process in a tumbling mill is associated with the development and testing a new shape of grinding body. Family of new grinding bodies ? spheroidal tetrahedrons (tetraballpebs) has been manufactured. Two types of spheroidal tetrahedrons and a classical ball (sphere) with one and the same weight are compared. A fuzzy entropy method to calculate the weight of the attributes is suggested. A grinding body which is the best approximation to the fuzzy formulated technological conditions is selected. Keywords: grinding, spheroidal tetrahedrons (tetraballpebs), balls, fuzzy sets

Sep 1, 2012

By P. S. Rao

In 1951, Tata Steel became the pioneer in Asia by setting up its first ever washery in West Bokaro Colliery. The first beneficiation plant used to produce clean coal of 19% ash with chance cone. Feed size of chance washers were -75 mm to +6 mm. The fine coal (-6 mm) were used directly. With change in technology,in 1986,chance cones were replaced by DM cyclones and coal was washed in two circuits. In the coarse circuit -13 mm to +0.5 mm coal was washed in two stages while the fine coal of -0.5 mm was treated in froth floatation cell. With further improvement in the process the higher ash raw coal was feed to produce clean coal of 13% ash. In 1998, DSM cyclones were replaced by scrolled Evolute design cyclone which has Ep of 0.020 to 0.025 ranges resulting in increase efficiency of separation. With the increase in demand of clean coal, lower seam proportion has increased in raw coal production. The washability studies of individual seams indicated large difference in the seam characteristics in terms of washability and specific gravity cut points of the individual seams. So washing all seams together had resulted in frequent change in the character of coal and warrants frequent changes in the operating parameters of the plant in which the separating efficiency comes down and ultimately resulted in yield loss initially. With increase in knowledge and experience in coal washing the solution to this problem was achieved by adopting, seam-wise washing which is enabling process engineers by keeping set point for longer periods there by to enhance the separation efficiency. Keywords: coal processing, froth floatation, steam washing

Sep 1, 2012

Low-grade ore bodies, increase in rock competency, finely disseminated valuable minerals in the ore bodies, ore variability and water scarcity are among the technical challenges faced by the mining industry. These challenges have increased the business risk, capital investment and operating cost of the mining projects. Since the last 20 years, many large-scale concentrators have been built to cope with the above-mentioned challenges. Comminution, especially the fine grinding is an energy-intensive process. For example, the ball mill has a limitation in the fine grinding regime where the energy consumption increases exponentially when the product size is below 45 µm. The industry has been seeking for solutions that have a minimum risk and total cost of ownership. The stirred milling technology such as the TowerMill is well accepted by the industry as it has demonstrated the attributes required for fine grinding. TowerMill is a matured technology that has been adopted since the 80s for regrinding duty. Recently, this technology was installed in secondary and tertiary grinding duty to prepare a finer feed to rougher flotation. Four units of TowerMills were installed in a magnetite concentrator in Western Australia in tertiary grinding duty. Recently, Nippon Eirich has conducted process performance evaluation on the TowerMill circuit. The outcome of the exercise had indicated that the circuit is consuming 3.4 kWh/t to reduce from 55 µm to 35 µm with a narrow product size distribution. The effect of operating variables such as the specific energy, grinding media size, mill content % solids and mill feed configuration on the grinding efficiency were evaluated at the plant scale. Furthermore, the scale-up methodology was validated. The scope of this paper includes the performances of TowerMill and the validation of scale-up methodology.

Jan 1, 2018

By I Brum

Brazil and Colombia have large reserves of coal, those reserves in Brazil are located predominantly in the south and Colombia the main reserves are located in the north. Despite the relative ease of exploitation, these resources have been underestimated as a source of energy. Currently, these countries are developing projects and partnerships aiming to qualify this mineral resource, adding quality to the final product of the processing plants. In this scenario the processing of Brazilian and Colombian coal in flotation columns appears as a promising alternative, having been successful in mineral systems containing fine particles This paper aims to study the overall process of column flotation for a specific Brazilian coal and a specific Colombian coal. The material used in this study consists of fine coal from Brazil (Copelmi) and Colombia (Cerrejon). The objective is to recover carbonaceous matter and reduce the ash and contaminants grade. The two coals were floated using a negative bias in a 5 cm diameter conventional flotation column of 5 m high. Flotation parameter investigated included air velocity in the range 0.6 to 1.5 cm/s. For all runs, a constant negative bias of -0.25 cm/s and a pulp concentration of 8% w/w were used. For Cerrejón coal, 300 g/ton of frother and 907 g/ton of collector was used, whereas for Copelmi coal, 600 g/ton of frother and 1815 g/ton of collector was employed. The frother was a commercial Aerofroth 65 (AF65), whereas the collector was Kerosene. For the Colombian coal, in general, yield, organic recovery, ash recovery and water recovery decreased with the increasing air rate. However, for Brazilian coal the air rate had no significant effect. For Colombian coal, the highest yield (60% w/w) and organic recovery (69% w/w) were obtained at the lowest air rate (0,6 cm/s). Keywords: negative bias, column flotation, coal

Sep 1, 2012

By A. De1

Because of the extremely low utilization of strain energy in the breakage of solid particles, the energy efficiency prevalent in comminution technology is extremely poor. Schoenert considered that single-particle comminution under slow compression is the most energy-efficient mode of comminution and that energy efficiency should be compared to that. The usual method for grinding minerals and cement has been the ball mill, in which the hit-and-miss aspect of loose-bed comminution severely reduces energy efficiency. The fine grinding of minerals is a particularly energy-intensive process. Schoenert showed that the energy consumed in the comminution of particles in confined beds is second only to that of single-particle comminution under slow compression and developed the method of conducting particle-bed comminution continuously in a high-pressure roll mill. Since its first industrial installation in 1985, the high-pressure roll mill has established itself as the comminution device of choice for significantly improving the productivity and energy efficiency of size reduction from coarse size feeds down to products finer than 20 microns. The first of several hundred installations were in cement plants. The preliminary design and optimization of the industrial operation of high-pressure grinding roll (HPGR) systems, owing to the continuous nature of the device, cannot be efficiently done through laboratory experiments and needs to be achieved through proper system modeling. While the energetics of size reduction in high-pressure grinding rolls has been modeled very well, no model exists for the macroscopic variables in HPGR comminution. In high-pressure roll mill grinding, size reduction results from confined particle-bed comminution under compressive stresses such that the daughter particles produced are highly fractured, stressed, or otherwise weakened. This paper attempts to relate the comminution / compaction behavior for confined particle-bed under compression in a piston-die press with the macroscopic variables in HPGR comminution. A model describing the pressure-densification relationship is presented and used to accurately simulate the macroscopic variables in high-pressure grinding rolls, utilizing experimental data for particle-bed comminution with the piston-die press. The accuracy of the predictive simulations strongly suggests that, starting with a few batch-mode laboratory-scale experiments, it should be possible not only to identify the optimal operating conditions for existing operations but also to successfully design new industrial high- pressure grinding roll systems.

Sep 1, 2012

By Y. Q. Qui

In the bauxite flotation process for desilication, the middling treatment mode is the important factor to raise the flotation recovery of the preparation concentrate. The middling treatment mode mainly depends on A/S and the size composition. However, similar ratio of A/S should not be the single factor of re-dressing, size composition plays an important role also. Re-dressing the middling mixed with the tailings of concentrated to the rough ground for desilication and the concentrate of scavenged to the fine ground for desilication to raise the recovery of 5.83%, when compared two flow sheet schemes.

Jan 1, 2014

By H. R. Zhang

In this paper two optional production processes are presented for reasonable utilization of primary sylvinite in Qinghai province, China. The two kinds of products as chlorine-free potash fertilizers; potassium sulphate or potassium magnesium sulphate can be obtained. In the course of potassium sulphate production, using primary sylvinite from Qinghai salt lake as raw material with impurities such as sodium chloride and insoluble in primary sylvinite, it must be prepared by flotation before being converted into potassium sulphate. This final product has found wide use in tobacco industry in China. However, in some cases Chinese farmers would rather buy the fertilizer of potassium magnesium sulphate than high quality of potassium sulphate. With flotation process which is a little different from above mentioned, the potassium magnesium sulphate fertilizer may be produced by washing one of the flotation concentrate presented as picromerite, while another concentrate containing potassium chloride is treated as by-product.

Jan 1, 2014

By G. C. Li

Gold extraction using iodide leaching from refractory carbonaceous gold ores was studied. Thermodynamic analysis of iodide leaching chemistry had been carried out. Eh-pH diagram of Au-I2-I--H2O leaching system showed that the coordinating active forms from iodides were I3- and I-, while the major coordinate compound formed during iodide leaching was AuI-. For leaching parameters optimization, technological parameters such as I2 concentration, I2 :I- ratio, oxidation assisting agents, liquid/solid ratio, and leaching duration were studied. The leaching results showed that the average Au leaching rate reached 91% and 92% for oxidized ore and roasted primary ore respectively. Leaching process proceeded in weekly acidic or neutral slurry at ambient temperature; the leaching duration was 4 hours. After that gold was extracted from the pregnant liquor by activated carbon adsorption ? desorption ? electrowinning process. Gold recovery was over 93% in the adsorption process, while the gold recovery in electrowinning process was about 95%, provided that the initial gold concentration is 40mg/L or larger. For iodine regeneration it is enough to add hydrogen peroxide in excess into the filtrate after gold electrowinning, all the iodides existing in the solution in any forms would be precipitated in the form of elemental iodine.

Jan 1, 2014

By L. Y. Wang

In order to produce the iron and steel products with high quality and decrease the output of steel tailings, the quality of molten iron is a critical factor for iron and steel companies, especially the content of sulfidic in molten iron. Hot metal pre-treatment, an important and effective method to desulphur, is widely used in steel production. Millions of tons of slag from desulphurization and slag skimming are produced each year in China, and many more times this amount is stored in slag dams because of the lack of effective means to deal with it. In order to achieve the goal of sustain-able development, recycling these slag becomes necessary. The main objective of this paper is to study the composition characteristics of slag that from desulphurization and slag skimming. The sample was obtained from Anshan Iron and Steel Group Corporation, processed by hot metal pre-treatment. In this study, the chemical components and the mineral compositions of sample were tested. The results of chemical components and iron chemistry phase analysis showed that the iron and sulphide content in this sample were high, and the iron products existed mainly in the form of magnetite, metallic iron, ferrosilite. X-ray diffraction (XRD) and scanning electron microscope (SEM) results indicated that the sample included metallic iron, ferrate, wustite, metasilicate, aluminate, aluminosilicate, white lime and soon. Grading magnetic separation test work showed that magnetic separation was an effective method to recovery iron products and decrease the sulphide content in concentrate, and the tailing could be used as the raw material or padding in cement production.

Jan 1, 2014

By Robin J. Batterham

The Bologna Process started in 1999 with a declaration signed by ministers from most European countries. As of 2012, the Bologna Process now has 47 participating countries (EHEA 2012). Overall, the Bologna process has demonstrably changed higher education in many countries to allow for considerably more flexibility in course offerings. Keywords: bologna model, education

Sep 1, 2012

By H. R. Manouchehri

Sustainable development requires the optimal use of natural resources and recycling of the wastes. In fact recycling is the final productive use of obsoletes. ELVs, obsolete appliances and industrial wastes have become important resources for production of iron and steels, non-ferrous metals, and composites. Within shredding plants, these obsoletes are firstly shredded to the pieces and then processed to recycle different materials, especially ferrous and non-ferrous metals for metallurgy. Traditional and new developed mineral processing technologies are nowadays used for recycling different materials from waste effluents. Shredding and separating plants are currently recycle the wastes by make use of different technologies to mainly produce raw material for metallurgical application. However, other non-ferrous components are also treated for energy conservation and protecting environment. Currently, recovery in shredding and recycling plants maximises to 75% and about 25% of the feed is land-filled. However, recycling rate must be increased in due to the economical, environ-mental and social concerns. A comprehensive study for recycling, with especial focus on ferrous metal recovery, was sup-ported by Swedish Environmental Agency (MISTRA) to look at possibilities to increase the recycling rate and to reduce the amount of disposal. Part of this study was dedicated to study the shred-ding plant facilities and to look for possibilities to improve the quality and quantity of the shredding product streams. The aims were to improve the quality of ferrous scrap (apparent density > 0.9 and Cu<0.25%) for iron and steel production as well as having better quality for non-ferrous metals through the recycling schema, and finally to treat the shredder residue (SR) to recover metals and plastics to reduce the disposals. This paper summarises the results of sampling and conducting separation tests for improving the recovery of the ferrous and non-ferrous metals. The results indicated to be possible to obtain high quality ferrous scrap at recovery of 88%. However, the total recovery for metal scrap has reached 93%. Furthermore, test results on fine, P< 8mm, shredding residue (SR) showed promising prospect in recovery of metals and protecting environment by physical separation, i.e. electrical separation technique.

Jan 1, 2014

By Shugang Hu

According to XRD, DTA and SEM detections, the hydration products of blast furnace slag (BFS) based cementing material SL, SLG. were studied in different age periods. The XRD analysis of cementing material SL hydration products showed that the composition of hydration products were mainly amorphous substances, few crystalline substances. Characteristic peak of ettringite hadn?t been found in the spectral line of DTA, and it hadn?t been found in the figures of SEM, either, which was accordant with the conclusion that the cementing performance of SL mainly coming from gel of hydrated calcium silicate (CSH) and hydrated calcium aluminate. However, the main hydration products of SLG are Aft, CSH, and AFm, which are similar to Portland cement. All results suggest that BFS is a suitable base material for cementation. Keywords: blast furnace slag, backfilling cementing material, hydration products, cementing performance

Sep 1, 2012

By Venugopal Tammishetti

One of the important technological challenges facing the iron ore industry in India is to find commercially viable technologies to process alumina rich iron ore fines and slimes. The key to solving this problem lies in developing selective reagents for the separation of iron oxide minerals from associated gangue minerals like quartz, gibbsite, kaolinite and montmorillonite. We present in this paper our successful results on the dispersion-flocculation of three different natural iron ore slime samples from mines in India using the reagent combination of PVP dispersant and corn starch flocculent. All the three samples contained hematite, goethite, kaolinite and gibbsite minerals as confirmed by X-Ray Diffraction (XRD) analysis. The effect of various process parameters such as pH, dosage of reagents, settling time and pulp density was studied. We were able to produce a concentrate assaying 66.2% Fe and <2% Al with a yield of 67.4% by weight (with a recovery of 77% of iron values) using PVP (1 ppm dosage) and corn starch (20 ppm) for one of the slime sample (Sample I) assaying 58.2% iron (Fe) and 3.8% aluminium (Al). The XRD analysis of settled and dispersed fractions revealed that alumina-containing minerals like clay and gibbsite mostly remain in the dispersed phase while iron-bearing minerals tend to concentrate in the flocculated fraction. Keywords: iron ore, slime, flocculation, dispersion, beneficiation, starch, polyvinylpyrrolidone

Sep 1, 2012

By L. W. Luo

Zeolite in some regions or countries of the world have been the subjects of materials for environmental remediation involving the use of removal to heavy metal ions and some organic pollutant as a sorbent because of its capacious ions exchange and huge surface area. This article addresses the equilibrium and kinetics for manganese adsorption using zeolite modified by hexadecyl trimethyl ammonium bromide (HTMAB) as a sorbent material over a range of pH between 3.4~7.2 with eight different Mn(?) solution concentrations. PHzpc (pH of zero point charge) of the sorbent was examined according to the method proposed by Tripathy and Kanungo, and a value of 6.91 was obtained. The experimental data fit langmuir?s model for the majority of pH and Mn(?) solution concentrations tested (0.92<R2<0.97). The maximal adsorption capacity, qm ascending with pH between 3.4~7.2, rise from 15.01mg?g-1 at 3.4 to 19.46 mg?g-1 at 7.2. Besides, the constant of Freundlich Kf have the same trend with qm, increases with pH ascending. And the sorption intensity, represented by parameter 1/n in Freundlich?s model, is favorable in entire range of metal ions concentration studied. Finally, kinetics data accurately fit to pseudo-second order which indicate that there must be sorption of Mn(?) behavior occurring on inner-sphere of the sorbent.

Jan 1, 2014

By R. K. Logric

Bor flotation tailings are very interesting from two reasons: first, is having due value presently, and second represent serious pollutant into this region of Balkan. This paper is only one small part of investigation about processing of valuable minerals from tailings, and desulphurization of this biggest pollutant in the same time, by refloating. The main objective of this work is to pay attention on this problem for resolve greatest environ-mental problem of Serbia and Balkan in the nearly future. Bor is potential regional risk spot, since that failure of its tailings dams would release high amounts of toxic materials that would reach the Danube River. The basic goal of this experimental investigation was finding some possibility for flotation tailings treatment by classical froth flotation. In order was obtained material effect through copper recovery, and environmental protection by moving the rest of reprocessing into the safe place. The work present obtained results of laboratory tests in two laboratories: laboratory of mineral and recycling technology at the faculty in Bor, and laboratory of department of mineral processing of ITNMS in Belgrade.

Jan 1, 2014