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By Ayumu Tokumaru, Shuji Owada, Gangfeng Liu

"Several million spent catalytic converters are disposed annually worldwideandeach containing about 0.5-1g ofplatinum and 1-2g of all the platinum group metals (PGMs), then,it is fairly significant to recover PGMs from the spent automobile catalyst. The PGMs’ recovery is a proven technology, including pyro-and hydrometallurgicalmethods, and the highestrecovery can achieve approx. 98 wt.% by acid-leaching method, but theserecyclingtechnology seems to be too highlyenergy-consuming. SincePGMs aredistributed only in coat layer in spent catalyst, it is of great significance to enrich the coat layerwith some physical methods as a pretreatment.In this paper, according to the double-deck structureof the catalyst andthe different properties of the two main compositions, alumina-ceria phase of coat layer and cordieritephase of substrate, the concentration of the coat layer was investigated by combiningthree kinds of physical separation technologies, heating-quenching, crushing and surface grinding. In the first stage, thermal stresscouldgeneratebetween the two phasesby thermal expansion difference,to producefracturesin the thinnest part of coat layerand micro-cracksin coat layerand at the interface of coat layerand cordierite substrate. The second stage of crushing, by jaw and roll crushers, could break dominantly the coat layer and the third stage of surface grinding, carried out by attritor, promoted further separation and concentration of coat layer fromthe substrate.We also improved the attritor grinding by adding a new lift-arm to the cell for achieving better mobility of sample particles in the selective surface grinding."

Jan 1, 2014

By Lutz Rolf, Halit Z. Kuyumcu, Salas Cazón. Milton A.

Aim of experimental investigations was the mathematical description of the abrasion process running with a single particle stress. This is on the one hand the basis for the physical interpretation of the process, on the other hand the base for the simulation of abrasion processes carried out in technical scale. With this investigation for the first time the influence of the particle shape changing with increasing abrasion progress was quantitatively described. This influence affects itself particularly strongly on break-fresh particles up to an abrasion degree of approximately 10 to 20%. This is for the description of technical processes the most interesting area.

Jan 1, 2003

By Yuki Tsunazawa, Shuji Owada, Kazuki Tahara, Shinobu Ogino, Chiharu Tokoro

"Printed circuit boards (PCBs) are an important constituent of waste electric and electronic equipment (WEEE), and contain many electronic components with valuable, hazardous or both materials. Recycling of PCBs is an important subject not only from the treatment of waste but also from the recovery of valuable materials. Demand for rare earth metals is expected to accelerate because of their growing use in next generation high technologies. Since some of these metals are concentrated in a specific electronic component, for example, Ta in capacitors, a special and selective grinding such as parts detachment from the board is effective for the recycling of a part of rare metals. However, direct computer simulation method to investigate a comminution/detachment process of PCBs has not yet been established. In this study, our objective was revealing the mechanism of breakage phenomena in comminution / detachment process of PCBs using computer simulation. A special and selective grinding using an agitation mill promoted the removal of components from a PCB by detachment and was an effective method for the recovery of rare metals. Simulant PCBs on which some capacitors were solder-mounted were used for the comminution test using drum type mill with agitator. To describe this mechanism of the parts detachment process, a computer simulation using discrete element method (DEM) was conducted. Although only an indirect simulation using the spherical particle model was possible for part detachment and board breakage, the particle-based rigid body model could directly represent the behaviour of PCBs. Simulation results successfully corresponded to comminution experimental results."

Jan 1, 2014

By Yu. Gurevich, M. Teremova, I. Prokopev, A. Razvjaznaya, N. Algebraistova

"The objective of this work is the scientific justification and development of efficient and environmentally-friendly method of bulk concentrate preparation for selection with application of microbiological practices. This research suggests to apply Pseudomonas Japonica bacterial culture to the bulk concentrate before the selection circuit in order to clear the surface of sulphides from the xanthate skin. It is also suggested to apply bacterial consortium Ochrobactrum ?nthropi and Pseudomonas aeruginosa JCM 5962 for desorption of diesel residual concentrations. High-efficient and environmentally friendly method of copper-molybdene and lead-zinc bulk concentrate selection was developed based on theoretical and experimental research work with application of microbiological practices. In comparison with conventional methods (steaming, sodium sulphide washing) the above suggested bio-technological method of bulk concentrate preparation before selection cycle will allow to reduce material and power expenditures, and it is also environmentally friendly. INTRODUCTION High-efficient selection of sulphide bulk concentrate is gained exclusively after collecting agent is removed from mineral surface. Therefore, the problem of bulk concentrate preparing before the selection cycle is acute, since the further technological parameters of the subsequent separation depends on the effectiveness of pulp preparation. Existing traditional ways of bulk concentrate preparation. such as washing or steaming, are characterized by high energy and material costs in industrial conditions [1,2]. The microbiological treatment before separation of the bulk concentrate into different kind of concentrates appear one of perspective processes for treatment of bulk concentrates [3,4]. At the present time, the world practice of processing mineral raw materials demonstrates the wide application of technologies using microorganisms: bacterial leaching and oxidation, purification of industrial wastewater. This is due to the fact that biotechnological methods are environmentally safe, low-cost, and suitable for refining complex ores and raw materials of industrial origin."

Jan 1, 2018

By Fatemeh Saeidi, Malcolm S. Powell, Mohsen Yahyaei

In order to deal with the problems of existing comminution models a new approach towards the development of mechanistic models has been made so as to better understand the physics of milling processes and environments. Despite enormous improvement in this field a comprehensive study of rock breakage characterisation, appropriate for use in these types of models, is still scarce. This paper reviews the existing models of comminution according to ore characterisation techniques and parameters. The authors have looked into the existing testing methods and their applied mechanisms of breakage, using standard test results available at the JKMRC. The study includes classifying testing devices such as the drop weight tester, rotary breakage tester, slow compression, and piston and die based on the few major fundamental mechanisms of breakage that are experienced by rocks in the breakage process. The paper compares the range of particle size and energy utilisation, applied strain rates and loading mechanisms for the equipment. The product size distributions from the various equipment is compared for equivalent input energies, various loading rates but the same level of energy intensity, a broad range of energy including low energy utilisation and fines generation rate for equivalent specific energy input. The results clearly show that the outcomes and conclusions on competence and energy for breakage are a function of the test method that is applied. In ongoing work, it is proposed to investigate common tests that can be applied to characterising ores in a manner suited to modelling a range of comminution devices.

Jan 1, 2014

By Regis Texeira, Leopoldo Gutierrez, Vicente Hernandez, Caludia Vidal, Lina Uribe

"Molybdenum is currently the most important by-product of Chile´s copper mining industry. This mineral has gained international relevance over the years, because of its price. At mining deposits in Chile, copper and molybdenum are extracted together and then separated in a concentration process consisting of several flotation steps using sodium hydrosulfide (NaHS) as copper depressant. However, there are environmental issues related to the potential emisions of toxic hydrosulfide gas and bad odours, which affects nearby communities and suppose a risk for operators. This problem has led to the need for development of new technologies to eliminate the use of NaHS in the process of selective flotation of Cu and Mo minerals. In this work, results of flotation tests in which lignin derivatives reagents are used to obtain the selective separation of Cu and Mo minerals by flotation are presented. In this technology molybdenite is depressed by the action of lignin derivatives (lignosulfonates), while copper sulfides remain hydrophobic and float. The use of lignin derivatives in the selective flotation of copper molybdenum minerals represents a non-toxic alternative to NaHS.INTRODUCTIONSeparation of copper sulfides from molybdenite is commonly achieved through a two-stage flotation process. In the first stage the collective flotation of copper sulfides and molybdenite is promoted to generate a collective concentrate which is then treated in a second stage with sodium hydrosulfide (2.5-3.0 kg/t NaSH) to depress copper sulfides flotation without affecting the flotation of molybdenite. As a result a copper concentrate with 30-35% Cu, and a molybdenum concentrate with 50-52% Mo are generated. Although this process is widely used at industrial level, environmental issues related to the risk of H2S generation and bad odors have always been a concern. Thus there is a need in the industry for a more environmentally friendly process to separate copper sulfides and molybdenite."

Jan 1, 2018

By Reza M. Rahman, Seher Ata, Graeme J. Jameson

"This paper presents the results of a through investigation into the froth recovery measurements in a controlled plant environment using a device that allows direct collection of dropback particles from the froth phase. Test work was performed at the Northparkes concentrator (NSW, Australia), using a feed taken from the head of the cleaner scavenger bank. The feed slurry had a relatively higher copper grade varying from 5.2% to 6.8%. Experiments were performed to investigate the effect of important flotation parameters such as air flowrate on the froth recovery. The size of the particles in the relevant streams was also analysed to acquire in-depth knowledge about the froth dropback mechanism. The results suggested that the froth recovery could be as low as 70%, although it was relatively easy to achieve the values in the range 75% to 85% by the correct choice of operating variables. It was found that the air flowrate has a positive impact on both collection (pulp) and froth zone recoveries. However, the effect was more prominent in the froth zone. It appeared that the froth recovery is a strong function of particle size."

Jan 1, 2014

By Graeme J. Jameson

In conventional flotation machines, the recovery is strongly related to particle size. As particle size increases, the recovery also increases, reaching a maximum in the range 20 to 120µm. Beyond this range however, the recovery declines quite quickly. The reason for the decline in recovery observed with coarse particles can be traced to the effect of turbulence. Bubbles trapped in turbulent eddies rotate rapidly, and when the centrifugal force on a particle exceeds the retaining forces due to surface tension, the particle detaches. Since the centrifugal force varies as the cube of the diameter of the particle, and the attachment force varies simply as the diameter, being proportional to the length of the contact line, it is clear that detachment forces will predominate as the particle size increases. The corollary is that the recovery of coarse particles can be improved if the level of the turbulence in the cell can be reduced to a minimum. In this paper, a new type of flotation machine will be described, in which the particles to be floated are suspended in a fluidized bed. An up flow of fluidizing water is provided, by recycling liquid from the top of the cell. The recycle stream is aerated in a high-energy device that disperses the air into fine bubbles that capture the fines and ultrafines. Results are presented for several minerals and coarse coal. Keyword: fluidized bed flotation

Sep 1, 2012

By Charlene Gokhale

Geopolymerisation has emerged during the last few years as an industrial and ecological approach to construction and waste management. By utilizing waste materials and their reactive properties, it is now possible to create geopolymers systems that not only mechanically durable enough to be used as construction materials but are also potential stable immobilisation systems for toxic waste. Previous studies by Van Jaarsveld et al. (1997) and Van Jaarsveld et al. (1998) have reported on the numerous applications of geopolymers in the immobilisation of toxic metals. Research into the possible utilisation of geopolymers as an encapsulation media for organic waste has however been rare. This paper therefore provides an insight into the possible utilisation of geopolymers as a binder for hazardous organic materials.

Jan 1, 2003

By J. Jávor

The response of the air/water interfaces to deformation in presence of surfactants is affected by the adsorption/desorption rate, re-orientation and exchange rate of surfactant. These surface properties can be observed using equilibrium and dynamic surface tension and surface elasticity measurements. However, the effect of these parameters on bubble size in dynamic conditions has not been studied due to the difficulty in capturing freshly formed bubbles in dynamic conditions. The paper presents a new experimental set-up designed and built at the Aalto University, called Shear Force Observation Chamber(SOC). The setupallows the monitoring and analysisof freshly formed air/liquid interfaces in dynamic conditions and facilitates the study of the effect of dynamic surface tension and surface elasticityon freshly formed air bubblesin presence of surfactants. The method helps to establish correlation between bubble size and dynamic interfacial properties and bubble-bubble interaction in turbulent flow. Dowfroth 200, Nasfroth 240 and Dowfroth 250 commercial flotation frothers were tested in this study. The results show a marked difference between results obtained in dynamic conditions compared to the static conditions. The results are presented and the reasons and implication to flotation modelling are discussed in the paper. Keywords: shear force observation chamber, flotation frothers, flotation bubbles, critical coalescence concentration

Sep 1, 2012

By C. Tokoro

Co-precipitation of dilute toxic anions with ferrihydrite is an important removal mechanism in wastewater treatment system. Although, numerous qualitative studies have been published on removal characteristic from wastewater of dilute anions by co-precipitation treatment, detail mechanism or quantitative characteristic is not well understood. This paper discussed the co-precipitation mechanism of As(V) and Cr(VI) with ferrihydrite by comparative experiments between co-precipitation and simple adsorption. In this study, co-precipitation experiments and simple adsorption ones were distinguished closely. In the former, precipitation of hydroxides and adsorption of anions develop simultaneously, but in the latter, anions adsorb onto prepared hydroxides. Although high affinity anions for hydroxides (e.g. As(V) for ferrihydrite) showed quantitative difference of removal ratio between co-precipitation experiments and simple adsorption ones, low affinity anions (e.g. Cr(VI) for ferrihydrite) showed quantitative agreement in spite of deferent forms of ferrihydrites between them, that is, amorphous ferrihydrite was formed in co-precipitation experiments, but goethite was formed in simple adsorption ones. In order to discuss the mechanism of co-precipitation phenomena, three experimental studies have been carried out: (i) adsorption isotherm measurement in the co-precipitation experiments of As(V) or Cr(VI) with ferrihydrite, (ii) zeta potential measurement of co-precipitated or simple ad-sorbed ferrihydrite with As(V) or Cr(VI), and (iii) XRD analysis of co-precipitated As(V) for ferrihydrite. All experimental results suggested the main mechanism in co-precipitation phenomena of As(V) was not only a surface complexation (simple adsorption) but also a surface precipitation.

Jan 1, 2014

By L. Muhr, Y. -T. Tang, M. -O. Simonnot, B. Laubie, R. -L. Qui, Z. Chour

"Agromining aims at recovering metals from different secondary resources with hyperaccumulating plants. These natural plants can selectively concentrate metals at very high level and can be transformed to produce commercial compounds. The classical strategy to recover metals from hyperaccumulator plants is based on hydrometallurgy. It consists of: i) burning the plant to obtain ash, which is a very rich bio-ore without organic matter, ii) transferring the target element(s) into aqueous solution by acid leaching and iii) purifying the leach liquor to obtain the target element(s) in the desired form. This method has enabled us to obtain nickel salts, nickel oxide, zinc and cadmium from different plants. However, it is not possible to apply this approach to recover rare earth elements (REEs) from the fern D. dichotoma, growing on mine tailings in South China. Actually, this plant is very rich in silicon: plant burning gives an amorphous ash, very stable despite severe leaching conditions. Therefore, the strategy has been changed and processes are currently developed to extract REEs by direct leaching of the biomass, without burning the plant. Several conditions (i.e. leaching solutions) have been investigated, showing that a good extraction yield was obtained with HNO3 0.5 N (around 84%). This yield was increased to 99% by adding a complexing resin into the leaching solution. After two-steps of elution, results have shown that is possible to recover 75% of the REEs at 81% purity.INTRODUCTION The demand of rare earth elements (REEs) (including 15 lanthanides, yttrium and scandium) has been growing sharply over the past years, because of their industrial applications. REEs are essential elements for emerging technologies, and are used for example in permanent magnets, lamp phosphors or rechargeable batteries. China is the main producer, and the market supply became tense in 2010 when this country decided to limit exports of these elements. Exploitable mineral resources, as well as REE separation capacity are concentrated in a few countries (e.g. USA, Australia, Malaysia, France), which increases the supply risk. Therefore, these elements are considered as critical raw materials (CRM) for many countries and especially for EU (Fortier and Gambogi, 2017)."

Jan 1, 2018

By James Y. Oldshue

"Very seldom is it possible when contacting a gas with a slurry to measure the dissolved gas concentration in the slurry, and even where possible, equilibrium data with a suitable Henry.s law constant are seldom available.In general, by assuming a reasonable value for the dissolved gas concentration in the slurry and a corresponding equilibrium gas partial pressure P*, KGa values can be calculated for the pilot plant and then scaled up. Then, with the same P* value at various reaction conditions, a mixer can be designed which is quite satisfactory, having a reasonable design factor for full-scale performance."

Jan 1, 2003

By Carlos Pereira, Fábio de São José, Francielle Nogueira

Votorantim Metals Corporation is one of the leader companies in the extraction of zinc in Brazil. One of its mines, located in the city of Vazante - MG, was composed by zinc silicate ores, but recent studies have indicated a change in mineralization type with arise of zinc sulphide’s ore bodies with disseminations of galena (PbS) and silver. The liberation size between sphalerite and galena in this ore occurs in very fine granulometry (approximately 18µm), fact that has negatively influenced into the flotation process. Aiming to reduce this problem, studies about the use of dispersing in the flotation process have started. Thus, this study investigated the action of different reagents dispersing on the stability of the suspensions. The tests were carried out with samples of mineral galena and sphalerite using four types of dispersing within two different dosages and two pH. The reagents tested were sodium hexametaphosphate, sodium silicate, carboxymethiylcellulose, and sodium polyacrylate. The results of the dispersion tests were analysed in relation to dispersion index. The tests with hexametaphosphate showed high dispersion for both galena and sphalerite. The sodium polyacrylate and arboxymethiylcellulose showed a high dispersion index for galena and a low index for sphalerite implying that reagent can be used in the concentration process of galena.

Jan 1, 2014

By Anuttam Patra, Romain Bordes, Andreas Fredriksson, Tommy Karlkvist, Krister Holmberg, Kota Hanumantha Rao

Almost all of the flotation reagents used today were discovered by continued application of empirical methods and/or trial and error experimentation. Moreover, with the metal-ion specific approach used so far, it is difficult to separate the minerals containing the same constituent metal ion. A critical assessment of molecular recognition processes involved in biomineralization suggested the possibility of using reagents which are surface specific. The concept that the molecules consisting of two or more functional groups having appropriate spacing between those so as to achieve structural/stereochemical compatibility during interaction with the mineral surface exhibit structure-specificity is thought to be extended to the design of specific collectors in flotation processes. In the present study, for the first time, a rational design of surface active molecules, and thereby the recognition of crystal faces (of minerals) by these molecules through structural and stereochemical matching is being utilized successfully to selectively float various minerals. For this purpose, carboxylate-based collectors (for mineral specific flotation of calcium minerals) as well as xanthate-based collectors (for mineral specific flotation of sulphide minerals) with a fixed alkyl chain length but having two functional groups with varying geometrical distances (separated by a spacer of one, two and three carbon atoms) between them have been synthesized. In this article, we have discussed the design, synthesis, purification of these novel mineral specific collectors as well as their important solution parameters in relation to flotation processes.

Jan 1, 2014

By K. Sasaki, H. Miki, Y. Muta, T. Hirajima, G. P. W. Suyantara

"Selective flotation of chalcopyrite and molybdenite is continuing problem since its selectivity is not perfect and current NaHS process needs closed system flotation plant because of hydrogen sulfide emission on acidic condition. Some alternative additives investigated as chalcopyrite became hydrophilic and molybdenite kept hydrophobic. XPS analysis indicated chalcopyrite became hydrophilic since iron and copper sulphate, hydroxide was covered on the surface whereas molybdenite kept hydrophobic since only molybdenite can be seen. Flotation experiments of chalcopyrite and molybdenite mixture sample indicated excellent separation that 95% of molybdenite can be recovered as froth and 93% of chalcopyrite can be recovered as sink. Flotation experiments with real bulk flotation concentration indicated similar separation result compared with current NaHS additive system. Possible mechanisms and detailed phenomenon were investigated based on the surface analysis and thermodynamic calculation etc. this alternative additive is easy to handle compared with NaHS since it does not emit effluent gas and commercially preferable.INTRODUCTIONMany copper mine often associates molybdenite (MoS2) as trace mineral. It is important to separate molybdenite and copper mineral efficiently since molybdenite is valuable mineral and also contamination of molybdenite into copper concentrate decrease concentrate value. Conventional separation of copper sulfide and molybdenite has been achieved with sulfide bulk flotation followed by selective molybdenite flotation with NaHS addition since NaHS works as a depressant for copper sulfide (Bulatovic, 2010; Ansari and Pawlik, 2007b). However, this current process shows imperfect molybdenite recovery (Liu et al., 2012, Zanin et al., 2009) and depressant such as NaHS needs to be used under specific flotation plant since it might be environmental contaminant (Ansari and Pawlik, 2007a). there are still unknown on the effect of depressant NaHS, but one of the theory is NaHS reductant effect. It is worth to investigate the effect of other reductant as depressant on chalcopyrite. On this research, typical reductant, Na2SO3 are added to utilize for selective flotation of chalcopyrite and molybdenite."

Jan 1, 2018

By David I. Verrelli, Boris Albijanic

"Froth flotation is an exceedingly complex physicochemical process. The convenience of distilling much of the complexity of the bubble-particle interactions into a single parameter has led to the continuing popularity of the classical ‘induction time’ to quantify the threshold for bubble-particle attachment to occur. Despite this popularity and the simplicity of the concept, there is no single universal method of evaluating the induction period. In this paper, we begin with a critical review of the available techniques for estimating the induction period. These are: back-calculation from experimental (micro) flotation tests; pushing a particle toward a stationary bubble (or vice versa) using an atomic force microscope (AFM); pushing a bubble toward a stationary bed of particles in the ‘Induction Timer’; pushing a bubble toward a stationary solid surface using the ‘integrated thin film drainage apparatus’ (ITFDA); and dropping particles onto a submerged stationary bubble using the ‘Milli-Timer’ device. Each one of these methods has advantages and disadvantages, and the best choice depends on the application. In the experimental section, we present quantitative comparison of the induction periods estimated using two different techniques, namely the Induction Timer and the Milli-Timer. The same particles were tested in each device, under the same conditions. It was found that by tuning the operation of the particle pick-up device, similar estimates of induction period could be obtained to the estimates made by direct observation with the Milli-Timer. In the former device a bubble is driven toward a particle bed at a controlled rate, whereas in the latter a particle’s motion is governed by the hydrodynamics. The potential to match these presents an intriguing prospect for better understanding the bubble-particle interaction, and the possibility to ‘calibrate’ the simpler Induction Timer against direct observations."

Jan 1, 2014

By C. Stollberg

The recovery of valuable materials from electronic waste is of growing importance for the re-source management not only in the industrialized nations. Being a significant step in an innovative automated process for recycling of metals and plastics from used electric and electronic equipment, the results of the work introduced below, prove the applicability of microbial leaching of metals from printed circuit boards (PCBs) at industrial scale. Within the first project step, which started in March 2005, experiments in shaking flasks with a mixed culture of chemolitotrophic bacteria (mainly Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans) were carried out to study the solubilization of non-ferrous metals present in the electronic waste. It was found that the best results were achieved by means of a two-stage process in which leaching of these metals was carried out by acidified ferric sulphate solutions generated as a result of the prior bacterial oxidation of ferrous ions to the ferric state. Special reactor systems for bacterial generation of such solutions and for the subsequent leaching of non-ferrous metals from the waste were developed, constructed and tested under laboratory and pilot scale conditions. The optimum technological parameters such as concentration of iron ions, pH-value, temperature and presence of nutrients were established for both reactor systems. Parameters such as particle size, pulp density and flow rate of the suspensions being leached were established for the leaching process carried out under continuous-flow conditions. The complex flow sheet reflects a highly efficient technology on the basis of metal recovery, environmental effect and economical acceptance. The process was successfully implemented into an industrial demonstration unit.

Jan 1, 2014

By M. R. Robben

Carbonates have gained significant economic importance for the human kind. On one hand over a hundred uses are listed for carbonates. On the other hand, carbonates host base metal deposits. Although the carbonates play a significant part in the development of those deposits, in the mineral processing they consume acid and cause selectivity problems during flotation and leaching. Carbonates also accompany other industrial minerals as waste rock. For all those cases it necessary to find a technique to separate carbonate as early as possible in the processing chain. In this paper, the applicability of near-infrared spectroscopy (NIRS) sorting for the separation of carbonates is discussed. NIRS sorting is a sensor-based sorting technique, in which particles are singularly detected by a sensor and then rejected by an amplified mechanical, hydraulic or pneumatic process. This technique can for example be implemented in the process as a pre-concentration step for coarse particle sizes up to 300 mm. NIRS sorting discriminates among materials based on the difference that exist between their spectral properties in the near-infrared (NIR). Vibrations of molecular bonds in carbonates cause characteristic spectral properties in the NIR, which makes carbonates detectable, possible to identify, distinguish and separate from other rock materials. The spectral properties can also be used to distinguish between different carbonate minerals and mixtures. If the spectral variations are large enough for detection, sorting based on NIRS is possible. Feasibility studies on sensor-based separation of carbonates in the processing of talc, borate, fluorite, marble, zinc-oxides, copper sulphide and iron ore as well as the discrimination of calcite and dolomite mixtures are conducted and indicate the high potential of NIRS sorting in the minerals industry. Keywords: carbonate separation, sensor-based sorting, near infrared spectroscopy, NIRS sorting

Sep 1, 2012

Geopolymers are novel engineering materials with the potential to play a highly significant role in the transformation of the construction materials and building products industry in the push to-wards sustainable development. These materials are formed by activation of industrial aluminosilicate waste materials such as coal ash or blast furnace slag with alkaline solutions. Some mineral waste can also be used, either as fillers or as reactive components. The use of waste-based geopolymers results in significant (up to 90%) reduction in carbon dioxide emissions when used in cement replacement applications. In addition to the formation of conventional pre-cast products, these high performance mineral binders are ideally suited to use in the conversion or encapsulation of toxic waste, including radioactive waste, due to their chemical stability and resistance to acid attack. It is the aim of this paper to review recent developments on the science underpinning this ?green? technology, and to discuss the technical and commercial drivers governing the large-scale adoption of the technology. Some of the recent fundamental breakthroughs in the study of geopolymer technology at the University of Melbourne will be presented. Despite the complexity of this reactive sol-id-gel system, progress has been made in the development of a thermochemical reaction kinetic model that has been validated using both calorimetric data and synchrotron kinetic data. Geopolymerization is potentially a disruptive technology, so that it is normal to expect strong resistance from established companies in the construction materials industry. It is increasingly necessary that waste generating industries such as mining collaborate with industries such as construction that could utilize this waste. The world?s first full scale geopolymer plant utilizing waste and re-cycled material has been commissioned recently in Melbourne, Australia, so progress on commercialization will also be presented. The authors frequently present keynote lectures on geopolymer science and technology at materials science, ceramics and construction materials conferences. However, this interdisciplinary technology that is still in its infancy, deserves more attention in the mineral processing and mining industry in view of its potential use in the mining industry, and also in view of the importance of mineral processing techniques in recent advances in geopolymers.

Jan 1, 2014