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By I. Ngoma, Marijke Fagan, Susan Harrison, Rebecca Chiume

"Heap bioleaching is an unsaturated hydrometallurgical extraction process which is commonly applied to the recovery of copper from low grade sulfide ores as well as for preparatory treatment of gold ores. The leaching reactions occur in the liquid phase, catalysed by iron and/or sulfur oxidising micro-organisms. Contact of the mineral grains with the leaching solution is consequently essential for metal recovery. Additionally, the liquid is responsible for the transport of the liberated metal out of the heap under gravitation-driven flow. However, the highly inhomogeneous structure of the heaps coupled with low irrigation rates cause the flow to vary between being gravitationally and capillary dominated, resulting in non-uniform wetting of the ore. In this study a 132 kg agglomerated ore ‘slice’ is used to examine the effect of liquid distribution on microbial colonisation and mineral recovery in a long term bioleach (> 500 days) when irrigation from a single drip emitter source is employed. The novel setup enabled sample collection from ports positioned along the length and height of the ore bed, so that 2D maps of the degree of wetting and microbial colonisation could be generated at different times in the leach. Lateral movement of the liquid increased with bed depth; the majority of flow was below the irrigation point while the top corner of the bed that was not irrigated remained the driest region of the heap throughout the experiment duration. The lowest cell numbers were also recorded in the driest regions. Specifically, cell numbers in the top corner of the bed, 400mm from the irrigation point, remained at undetectable levels until the 283rd day measurement, in line with typical heap operation durations. This indicates that slow colonisation of the heap in the regions between irrigation points may be a significant issue in heap optimisation."

Jan 1, 2014

By Kumar Ashish, Shukla Akhilesh, Kr. Rokkam Kiran, M. Sheeba, S. Sombhatla Sundar

"Purification of zinc leachate plays a predominate role in zinc leaching refineries, to produce impurity free cathode sheets. As a part of such purification sequences, copper cementation with zinc dust is the preliminary step, since the presence of copper will preferentially deposit during zinc electro deposition and has the effect of reducing current efficiency. The cake thus produced is being accumulated as an inventory, due to invariable market and leading to space constraints & hazardous ambience. Hence, a project has been taken up for in-house generation of copper sulphate solution through ammonical leach followed by solvent extraction process and utilizing it as an active promoter for zinc sulphide flotation in Hindustan Zinc’s own captive mines. Cold purification cake majorly contains copper (30-40%) along with zinc (10-20%) and cadmium (2%). Confirmation to the above statement, photomicrographs of purification cake also confirmed the major presence of copper in metallic or oxidized form. In present work ammoniacal carbonate leaching of purification cake followed by solvent extraction using diketone based solvent has been studied under the influence of various parameters viz., temperature, agitation, pulp density, ammonia, CO2 dosages, solvent concentration, and impact of w/s zinc on leaching and solvent extraction. Leaching kinetics determined based on shrinking core model. Chemical reaction at unreacted core was found to be the rate controlling step. The estimated activation energy was found to be 24 KJ/mol. Leached copper has been extracted by solvent extraction with a ß diketone based solvent and is stripped with sulfuric acid as concentrated copper sulfate solution. The above established R&D findings are successfully implemented in the Commercial plant with a treatment capacity of two tons of cold purification cake per batch. Till now 500 MT of Purification cake has been treated, and generated 6500 MT of copper sulphate (55 g/l Cu), with final Cu recoveries between 87-90%."

Jan 1, 2018

By Xiaoping Xu

An albitization granite type tantalum-niobium ore from Jiangxi Province, China was taken as the research object in this paper. The main valuable minerals in this ore are tantalite-columbite and uranmicrolite, and the minerals that can be comprehensively recovered include cassiterite, sulfide minerals, topaz, zinnwaldite, and quartz-feldspar. Based on the research results of process mineralogy, the roughing process of gravity separation for coarse particles combined with flotation for fine particles is proposed. The combined cleaning process of flotation-gravity-magnetic-electric-hydrometallurgical separation is adopted for the rough concentrate of gravity separation while the combined cleaning process of gravity-flotation- hydrometallurgical separation is adopted for the rough concentrate of flotation. High intensity magnetic separation is used to separate and recover zinnwaldite and quartz-feldspar from gravity tailings. By mineral processing for the crude ore containing (TaNb)cassiterite concentrate is 0.0003% with a grade of Sn 63.22% and a recovery of Sn 47.42% while the yield of sulfide concentrate is 0.0783% with a grade of Pb 33.15% and Zn 27.09% which can be separated to get lead and zinc concentrate respectively. The yield of topaz concentrate is 0.1545% and the topaz mainly distributed in the size range of -0.4+0.074mm, which can be made into abrasive products of different particle sizes after classification. The yield of zinnwaldite concentrate is 16.91% with a grade of Liwhiteness of 75%, which is a glass-ceramic material of good quality. 2O5 0.0346%, Sn 0.04%, Pb 0.10% and Zn 0.33%, the tantalum-niobium concentrate with a yield of 0.00278%,a grade of (TaNb)2O5 53.61% and a recovery of (TaNb)2O5 44.49% is obtained. And the yield of 2O 1.34% and Rb2O 0.40%. The yield of quartz-feldspar concentrate is 30.42% with a grade of K2O+Na2O 8.98% and Fe2O3 0.11% and a natural All of tantalum, niobium, cassiterite, topaz, zinnwaldite, quartz, and feldspar are recovered effectively. Keywords: tantalum-niobium ore, gravity separation for coarse particles, flotation for fine particles, comprehensive recovery

Sep 1, 2012

By Fu Ping-Hao, Sergio Mauricio Vianna, Ewen Silvester, Emmy V. Manlapig

"Over the last 5 years, an ambitious project has been undertaken at the Julius Kruttschnitt Mineral Research Centre (JKMRC) aiming to isolate, study and, if possible, model the effect of particle size, liberation and collector adsorption density on the floatability of mineral particles. As part of this project, we have conducted highly controlled flotation test-work, combined with state-of-the-art solution and surface analytical techniques such as High Performance Liquid Chromatography (HPLC), Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS) and detailed mineralogical analysis to fully characterize the flotation behavior of a natural ore.The flotation tests were undertaken using a high-grade lead-zinc ore from BHP-Billiton’s Cannington mine (Australia) in a specially designed continuously operated laboratory scale flotation rig. Solution and adsorbed collector concentrations were measured independently during the course of the flotation tests using HPLC based ex-situ techniques. Liberation studies were performed using the JKMRC Mineral Liberation Analyser (MLA) on selected size intervals of different streams to estimate the specific surface area of galena. These results were used to calculate the collector adsorption density (collector coverage) on galena particles, with the eventual aim of developing a mathematical model describing the relationship between pulp chemistry, feed mineralogy, and floatability of galena particles."

Jan 1, 2003

By N. D. Dementieva

Based on lab and pilot-plant tests to recover gold, silver and lead of a Russian deposit, a collective and flotation concentration flow sheet with lead and sulfide concentrates was proposed. The type of the deposit is gold-sulfide-quartz-bearing. The recovery of gold, silver, and lead to a lead concentrate was 47.4%, 68.1% and 70.7%, respectively. The grade of gold and silver grade was 170 g/t and 372 g/t, respectively. The mass percent of lead, zinc and arsenic mass percent was 41.7%, 0.34% and 0.63%, respectively. The recovery of gold and silver recovery to a sulfide concentrate was 50.1% and 28.8% at the grade of gold 20.5 g/t and silver 66.2 g/t. Sulfide concentrate with arsenic mass percent ~3% was biooxidised followed by CIL and obtaining metal at the site as well as zinc concentrate from bioleaching solutions with zinc mass percent 45% at its 64% recovery. The total gold and silver recovery using a developed technology with the account of their treatment at a polymetallic plant was 92.2% and 93.7%, respectively.

Sep 1, 2012

By M. Kargar Razi

According to the unique properties and many applications of nano gold powder, it was prepared from an acid leaching tail solution. The low value residual gold ions were existed in acid leaching tail solution in Mouteh gold mine in Iran with fellow heavy metals as pollutants (FeP2+P, Cu P2+P, and ZnP2+P). Preparation of nano gold particles is achieved by two steps. First, by addition of ammonia as separation step and second using suitable reagents for precipitation/extraction step. Conditions control includes pH, residence time, temperature, agitation, and molar ratio of reducing agents to reagents. The optimum results show that nano gold powder was prepared by temperature of 250 °C, urea to gold molar ratio of 3:1, and reduction time of 20 min. Also, heat treatment improves dispersion of nano sized gold particles. The properties of gold nano powders were evaluated by SEM, A.A, and UV- Vis spectroscopy methods. The size of prepared particles were about 80nm to 90nm.

Jan 1, 2014

By Rebecca Hope, Derick Moolman, Frikkie Malan

"Despite the lip service that has been paid to pro-active plant maintenance processes over recent years, a significant portion of maintenance in industry is still reactive. The business driving force to prevent expensive production opportunity costs arising from “break-down maintenance” is obvious. Various benefits can be derived from successfully deploying remote equipment diagnosis technology and associated business processes.From an end-client’s viewpoint these include the ability to predict and take actions to prevent equipment breakdowns, increasing the lifetime of equipment by responding to appropriate operating instructions and therefore improving the return on capital expenditure. Better planning and scheduling of maintenance priorities and resources with performance measures like an Equipment Health Index are also possible. The knowledge that a qualified supplier engineer is constantly in touch with the operating conditions of their equipment, albeit remotely, is more than a comfort, and can be translated into quantifiable cost savings and improved supplier service levels.This paper analyses the reasons for the inadequate level of pro-active plant maintenance practice in industry today, and presents a number of important criteria in selecting appropriate solutions to this problem. A case study of a specific real-time, remote equipment management application is presented."

Jan 1, 2003

By S. Swaroopa

Copper-chromium mixed oxides are widely used as catalyst for organic chemicals industry, NOx and CO oxidation, solid propellant etc. In the present investigation, one such spent Cu-Cr catalyst has been tested for recovering copper and chromium values through hydrometallurgical route. The spent catalyst used in this study contains about 42% Cu and 36% Cr. Phase analysis through XRD indicates that major phases are copper chromium oxide (CuCrO2) and copper chromate (CuCr2O4) while minor phase is copper oxide (Cu64O). SEM images show that high energy ball milling changes surface morphology significantly ? more regular shaped grains in unmilled samples changed to fine agglomerates. Surface area also changes significantly due to milling. Preliminary leaching experiments with NH3 and H2SO4 media using unmilled samples indicate that both the media are suitable for selective extraction of copper. About 55% copper recovery is achieved in 2 h using 1.2 M NH3 + 0.2M (NH4)2SO4 solution at 100°C. Increasing NH3 concentration or temperature does not improve the recovery significantly. Under the above conditions chromium, dissolution is insignificant (max. 2.24%). XRD analysis of the residue indicates that copper chromate fraction (CuCr2O4), which is a spinel structure, remains mostly intact. In sulphuric acid media at ambient temperature, 47% copper recovery is achieved with 7.5% (v/v) H2SO4 and maximum of 57% with the increase in acid concentration to 20%. However, 67% recovery is achieved by increasing the leaching temperature to 150°C. High energy ball milled samples show improved leaching efficiency. Under the leaching conditions of 7% H2SO4 (v/v), 2% pulp density, 80°C an unmilled sample yields 47% Cu recovery whereas 3h and 5h milled samples yield 65% and 90% Cu recovery respectively in 2h leaching time. Influence of temperature is also more pronounced in milled sample leaching in comparison to unmilled sample. Water leaching of alkali (NaOH) roasted milled sample carried out at 750°C for 2 h with 100% NaOH (w/w) resulted in 80% Cr recovery as compared to 37% Cr recovery using unmilled sample under the same conditions. Keywords: spent catalyst, copper, chromium, leaching, mechanical activation, roasting

Sep 1, 2012

By Harri J. Lehto, Marja I. Oja

Empirical models used for predicting the performance of screens on the basis of capacity, cut size, water split and grade efficiency curves were evaluated. This paper reports experimental results obtained with single-deck Derrick screens. The performance of the screen was tested with limestone in a separate screen set-up, in a pilot plant and in industrial scale test runs. The results of pilot plant experiments showed that the measured water split was higher than the measured bypass. This is an indication to that water flow does not entrain the same proportion of all fine particles present in the feed which is advantageous for screening. The experimental design for the industrial test runs was made on the basis of the pilot plant tests. Suitability of the existing models has been checked and accuracy compared. The tests showed that best grade efficiency model was the Rosin-Rammler model. An empirical model for the evaluation of the model parameters as a function of pulp density of the feed and the load of the screen is suggested.

Jan 1, 2003

By Megan Becker, Cyril O’Connor, Jenny Wiese, Gaynor Yorath

The effect of particle shape on true flotation has been widely reported. The present paper presents results obtained in investigating the effect of particle shape on the entrainment of particles during the flotation process. Different hydrophilic minerals with particles of varying aspect ratios were used and their shape determined using rheological tests and QEMSCAN. Their entrainment properties showed a close relationship to their shape with the recovery due to entrainment increasing as the aspect ratio of the particles increased. The effect of surface charge, by changing pH, and size of particles showed that the effect of shape was sustained at different pHs and particle sizes. Proposals are made to explain these observations in terms of the known relationships between drag coefficients and terminal velocities and shape. Since it has been previously reported that different milling procedures can affect particle shape, these results indicate that it is possible that such different procedures may result in increased entrainment of hydrophilic minerals.

Jan 1, 2014

By U. A. Peuker, T. Mütze, F. Shayo, A. Wikedzi

"Buzwagi Gold Mine (BGM) is operated by Acacia Mining and located in the Lake Victoria Goldfields of central Tanzania. The mine treats a sulphide copper-gold ore to produce gold in form of doré bars and a concentrate containing gold, copper and silver. The BGM comminution circuit includes a primary crushing stage with a gyratory crusher and two grinding circuits using a Semi-Autogenous Grinding (SAG) mill and a ball mill. Currently, the grinding circuits are inefficient in achieving the aspired product fineness of xP,80 = 125 µm even at low to normal throughputs (450-600 t/h). An optimization study of the circuit performance was conducted to improve product fineness through circuit surveys, experimental lab work and simulations. The analysis of survey data revealed inefficient grinding operation characterized by ball mill product (xP,80 > 400 µm) coarser than designed and higher hydrocyclone cut sizes (xT > 200 µm), too. In MODSIM several options were simulated such as reduction of vortex finder and apex diameters, reduction of SAG screen aperture, and modification of cyclone feed density. An improvement of product fineness could be achieved by simulation of the cumulative changes but it was also concluded that the current equipment cannot achieve the target. Further simulations showed that a second ball mill might help to achieve the desired fineness as well as an increase of grinding throughput by up to 26 %. INTRODUCTION Simulation of comminution, particularly grinding and classification, has received great attention for many years, due to the fact that the unit operation is by far the most important both in terms of energy consumption as well as overall plant performance (King, 2001; Wills et al., 2006). The use of simulation is advantageous due to low cost as well as its ability to consider many variables simultaneously. Moreover, there are some benefits for optimizing grinding operations by simulation like decreased unit operating costs, increased capacity, and improved performance of downstream processes due to improved feed size distribution. This paper presents an optimization study for the grinding efficiency at Buzwagi Gold Mine. This was achieved through three full scale circuit surveys, lab work and simulations with MODSIM."

Jan 1, 2018

By T. Kumaresan

The Bayer process used for refining bauxite to smelting grade Alumina serves as the linchpin of the Aluminum production industry worldwide. Even though the process is well established, the presence of impurities in the liquor affects the quality of product and imposes a major economic cost on the industry. This review article focuses on the issues pertaining to Gibbsitic (Al2O3.3H2O) precipitation circuit. The comprehensive review provides a basic understanding of the aluminum trihydrate precipitation and agglomeration phenomena. Crystal growth rate and agglomeration play a significant role in determining the output PSD of agglomerates. Hence, the effect of certain thermodynamic and hydrodynamic parameters along with the impact of impurities (oxalates, aldols, acids etc.) and additives on hydrate growth has been reviewed.

Sep 1, 2012

By S. J. Neethling

"This paper examines the impact of several key variables on the performance of flotation cells. The study makes use of a simulator for the froth phase of the flotation vessel, as the main purpose of this study is to separate the impact of different variables from one another. In experiments it is very difficult to separate the effect of variables from one another as a change in a singe input parameter, such as air rate, invariably also affects many of the other key variables, such as bubble size and bubble bursting rates.In order to achieve this a base case simulation that is typical of many of the rougher cells found in sulphide flotation circuits was carried out. Four key variables, air rate, incoming bubble size, surface bubble size and the fraction of the bubbles flowing out of the cell unburst, were varied in order to obtain the system.s response.The most significant results were obtained when the bubble size was varied. An increase in the incoming bubble size has the effect of reducing the pulp zone recovery, but increases the froth zone recovery. If it were possible to vary the incoming bubble size without influencing the overflowing bubble size, the impact of the change would be unclear because of these two competing effects. The effect of a change in the overflowing bubble size has an opposite effect on the froth recovery, with larger bubbles resulting in lower froth recoveries.A final interesting result is that all the effects examined affect the process to a similar degree, which implies that none of these variables can be disregarded, either in industry or in further research."

Jan 1, 2003

By Z. S. Abisheva

Rare and rare earth metals use quite often is an indicator of national economy development. The world structure of the rare-earth metals manufacturing countries in 2015 was presented as follows: China – 94.2%, India – 2.0%, Russia – 1.8%, the USA – 1.2%, Brazil – 0.5%, Malaysia – 0.3%. In Russia, large reserves of rare-earth metals, which reach nearly 28 million tons, are revealed. Kazakhstan, possessing a raw materials source of rare-earth metals, has all prerequisites for development of branch. Rare metals are manufactured in Kazakhstan incidentally by non-ferrous metals production. The production of indium, thallium, cadmium, selenium, tellurium, bismuth is made at the Ust-Kamenogorsk lead plant; tantalum, beryllium, niobium and molybdenum – at the enterprises of “National Atomic Company Kazatomprom” JSC. Production of a titanium, magnesium and vanadium is adjusted on “Ust-Kamenogorsk Titanium-magnesium Plant” JSC. Capacities for beryllic production yield are available on “Ulba Metallurgical Plant” JSC. The main producer of perrhenic production and osmium-187 is "Zhezkazganredmet" RSE. The single producer of gallium in Kazakhstan is “Aluminium of Kazakhstan” JSC; the capacity of enterprise is 25 t a year. In Kazakhstan innovative technologies for rare and rare earths mineral raw materials processing are created. The technology has been developed and a vacuum distillation apparatus has been created to purify crude selenium, which makes it possible to obtain a metal with a main component content of 99.9-99.99%. Technologies for processing of technogenic wastes and byproducts of the copper industry are developed. Implementation of technologies allow to obtain ammonium perrhenate, perrhenic acid, osmium isotope -187, tribasic lead sulphate, silver-concentrate. The technology of complex processing of black shales of Balasauskandyk deposit with the production of gold, vanadium, rare earth elements, uranium and ferrosilicon has been proposed. The processing was carried out using methods of autoclave leaching, sorption, extraction, precipitation. A highly profitable sorption technology for recovery of rhenium from solutions of underground leaching of uranium ores containing 0.2-0.4 mg/L of Re has been created. The organization of ammonium perrhenate production from solutions of uranium ore will significantly increase the volume of its production in Kazakhstan.

Jan 1, 2018

By Rasool Hejazi

The feed to Chadurmalu iron ore concentrator plant is a mixture of magnetite and haematite iron ore with a Fe/FeO ratio of about 8. The feed to plant, after grinding via wet SAG mill, is pre-separated by wet low intensity magnetic separator. Magnetic product is conducted to magnetite processing circuit for producing magnetite concentrate, and nonmagnetic product is directed to haematite processing circuit. Due to surface oxidization of magnetite particles and a decrease in magnetic attraction properties, significant amount of these particles are misled to tailing which results in decreasing the efficiency of haematite processing circuit. This problem can be remedied by using magnetic drum separator with more magnetic intensity and/or gradient. In this paper, the replacement of LIMS separators with wet medium intensity magnetic separators with a field intensity of 3800 gauss on drum surface (MIMS) have been suggested and considered as the most suitable solution to prevent the loss of magnetite particles. The results of carried out investigations with replacement of drum separators in industrial scale, showed that utilizing MIMS in magnetite processing circuit resulted in increasing final concentrate weight recovery on average by 2.59%, without any adverse effect on the concentrate quality; decreasing the magnetite content in the feed to high gradient magnetic separator (HGMS) by about 3.5%; decreasing the feed to floatation part by about 7% and consequently decreasing consumption of chemical reagents; increasing Fe/FeO ratio of the feed to plant. Keywords: iron ore, medium intensity magnetic separator, haematite, Chadurmalu

Sep 1, 2012

By Ray Everson, Henry Kasaini

"We carried out adsorption experiments in chloride media to study the adsorption characteristics of Pd (II) anions on the surface of activated carbon. Throughout the experiments, we used commercial activated carbon pellets (0.8 Norit). The adsorption process was interpreted by using the ionisation and adsorption model. This implies that palladium anions were adsorbed physically on a protonated surface of activated carbon either as anionic complex species (PdCl4 -2) or aqua chloro-complex species [PdCl3(H2O)-] in acidic media. Furthermore, we established that adsorption of Pd (II) species was reversible at high chloride [Cl-1] concentration. The maximum adsorption capacity (Qsat) of Pd (II) anions averaged 27 mg/g. The Toth adsorption isotherms fairly predicted the equilibrium adsorption of Pd (II) species and the associated surface coverage.The effect of temperature and acid strength of the feed solution on the adsorption of Pd (II) ions were quantified. The adsorption kinetics was limited by external mass transfer since the effect of pore diffusion on the overall rate constant was negligibly small. A pseudo first-order kinetics model was used to describe the adsorption kinetics."

Jan 1, 2003

By l. Bokányi

The Tóth adsorption isotherm-model was derived and has been widely used for the inhomogeneous solid surfaces. The three-parameter isotherm incorporates the effect of the interaction between the adsorbed substances as well. All classic isotherms can be clearly derived from this one. Bio sorption is the sequestering of dissolved components, i.e. metals from aqueous environment by living or dead biomass. The mechanism of the bio sorption is rather complex and predominantly refers to the affinity of the chemical functional groups: acetoamido groups of chitin, structural polysaccharides, amino and phosphate groups in nucleic acids, amino, amido sulfhydryl and carboxyl groups in proteins, hydroxyls in polysaccharides, sulphates, etc. towards the soluted substances, i.e. heavy metal ions. The physisorption, as well as the micro precipitation also play a role in the bio sorption mechanism. The description of such a complex process can be done by a model reflecting this complexity. According to our experimental results obtained using algae and immobilised algae for the sorption of heavy metal cations, the most appropriate model for such a description is the Tóth-isotherm, the parameters of which can be interpreted. Flotation process is also a very complex one, the overall result of which depends on the partial results of many micro processes and parameters. The particle interaction which very often takes place in the flotation systems makes the phenomenon even more complex. The flotation kinetic model with particle interaction was already introduced by author in 1994 and further developed in 2000. In this paper based on the experimental results obtained with metallic particles in case of recycling flotation the applicability of the Tóth-equation as an alternative flotation kinetic model for the systems with particle interaction is proved. The applicability of Tóth-model in mineral processing demonstrates again its universal character and the great talent of the late József Tóth, great Hungarian chemist. Keywords : Toth isotherm, biosorption, Langmuir, Freundlich

Sep 1, 2012

By Jing Zhou

2-hydroxy-3-naphthoy hydroxamic acid code name F203 is a good collector of cassiterite, 1-hydroxy-2-naphthoy hydroxamic acid code name ZJ-3. F203 and ZJ-3 are similar series of isomers. They have similar naphthye, and similar series of functional OH and ?CONHOH, but the seat of OH and ?CONHOH group are different, on the F203 is 2.3; on the ZJ-3 is 1.2, ortho position too. According to Isomeric principle ZJ-3 is a good collector of cassiterite slime too. Using ZJ-3 as collector flotation -10µm occupies 90%, grade 1.16% Sn cassiterite slime of Da Chang Chehe concentration plant, pass one coursing flotation, two cleaning and one scarenging flotation, and obtains grand 18.26% Sn, recovery 92.68% cassiterite concentrate. The result proves the Isomeric principle of flotation reagents is correct again. This principle may supply to synthetize new flotation reagents reference. Keywords: F2O3, ZJ-3, cassiterite flotation, Isomeric principle, Isomeric principle of flotation reagents

Sep 1, 2012

By Tom Liu

This paper is a fundamental study of bubble-particle collision efficiency in turbulent flows. A CFD-based microscale scheme for the prediction of turbulent bubble-particle collision efficiency in a 3D isotropic turbulent flow is developed, and in this way, turbulence effects on particle-bubble collision efficiency are taken into account for the first time. By comparing the computed results with experimental data from the literature, the CFD simulation is shown to correctly predict the bubble-particle collision efficiency in a quiescent environment. The CFD method was then applied to the investigation of bubble-particle collision efficiency in a turbulent flow, and the simulation results are shown to be qualitatively consistent with the real observations. The predicted collision efficiency can be used in a multiscale modelling scheme, which would account for all control variables in a flotation cell, such as impeller structure and tip speed, air nozzle structure and air flow rate This study indicates how microscale simulations of bubble and particle behaviours, coupled to macroscale CFD simulations of flotation cells, can provide a powerful tool predicting the flotation rate in a real flotation cell.

Jan 1, 2014

By Tasuma Suzuki

Electrokinetic/permeable reactive barrier system is a promising in situ soil and ground water remediation technique to reduce toxic NO3- into less toxic NH4+. Using granular zero-valent iron (Fe0) as a reductant, the first objective of this study was to investigate the influence of the solid-liquid ratio and aqueouspHon NO3- reduction. The results obtained from a series of batch experiments showed that NO3- reduction was enhanced by either increasing solid-liquid ratio or decreasing aqueous pH. Based on insights obtained from batch experiments, the second objective of this study was set to design the remediation conditions of the electrokinetic/Fe0permeable reactive barrier system to maximize the NO3- reduction efficiency. Experimental results showed that the effectiveness of the system strongly depended on the Fe0 percentage in the reactive barrier, the pH in the anode reservoir, and the applied voltage, which were consistent with the results obtained from batch experiments. Under optimized treatment conditions, nearly 100 % NO3-was reduced into NH4+ in the permeable reactive barrier and collected in the cathode reservoir. Insights obtained from this study provided fundamental information on roles each of remediation design parameters plays, and will be useful to optimize the remediation conditions. Keywords: electrokinetic remediation, permeable reactive barrier, zero-valent iron, nitrate

Sep 1, 2012