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By Takahiro Furuzono

Saganoseki Smelter and Refinery of Pan Pacific Copper Co., Ltd. started treating copper anode slimes using a unique hydrometallurgical process in chloride media in 1997. The process comprises the following stages, decopperizing, wet chlorination, solvent extraction for gold, silver chloride reduction, and separate reduction stages that treat the gold extraction raffinate with sulfur dioxide gas. Precious metals and rare metals in the copper anode slimes are dissolved in an aqueous solution of hydrochloric acid by oxidative leaching, which is termed wet chlorination. Gold is efficiently extracted from the chlorination liquor by dibutyl carbitol in the solvent extraction stage. Gold is reduced by oxalic acid from goldloaded dibutyl carbitol and recovered as gold powder. The gold powder is cast directly into granules or ingots of more than 99.99% purity without electrorefining. Selenium is recovered as a selenium residue by reduction with sulfur dioxide gas and refined through vacuum distillation. The plant was designed to process 132 tonnes of copper anode slimes per month and has a current capacity of 206 tonnes per month due to several enhancements. Compared with the conventional process, the hydrometallurgical process described here provides some advantages, in particular, a higher product quality, shorter gold-retention time, and reduction in environmental load.

By S. Shrivastava

A structure based model has been developed for the prediction of viscosities of K20-B20, melts. These melts exhibit an anomalous behavior of viscosity with continuous variation in B203 content. A maximum and a minimum are observed at low temperatures, which disappear on raising the temperature above the softening range. The addition of K20 to the borate melts causes two opposing phenomena: (1) depolymerization effects and the related breakdown of network structure resulting in the formation of singly bonded oxygens, which weakens the structure and hence causes a decreases in viscosity, and (2) the formation of four coordinated borons (BO4 tetrahedra) which strengthen the structure leading to an increase in the viscosity. The structural changes taking place in these melts on varying the temperature and the alkali content have been reviewed and are incorporated in developing this model. The predicted values are in excellent agreement with the experimental values over the whole temperature and composition range.

Jan 1, 1992

By Kuniaki Murase, Tetsuji Hirato, Koji Nitta, Yasuhiro Awakura

"The redox behavior of copper species in an ""ammonium imide"" room temperature molten salt was examined in order to clarify the applicability of the salt to the electroplating media of various metals. Trimethyl-n-hexylammonium bis(trifluoromethanesulfonyl)- amide (TMHA-Tf2N), having an electrochemical window of 5.6 V (50 °C), and corresponding copper(II) salt were synthesized. In TMHA-Tf2N media monovalent copper ion, Cu(I), was stable and Cu metal was oxidized, or corroded, in the presence of Cu(II) species. Cathodic electrodeposition of copper metal and anodic dissolution of it were, thus, one-electron reaction and their current efficiencies were almost 100%.IntroductionElectrodeposition of metals from aqueous solutions is an important soft process for manufacturing thin-film materials, surface finishing, and extractive metallurgy. However, the electrodeposition of base metals, such as zinc, chromium, and nickel, from aqueous media inevitably accompanies hydrogen evolution, which lowers the cathodic current efficiency of metal deposition. Since the electrodeposition of aluminium, titanium, and rare earths from aqueous media is actually impossible due to their largely negative redox potentials, nonaqueous media such as aprotic organic solvent and high-temperature molten salts have been employed for the electrodeposition of these metals. Room temperature molten salts (RTMS),1, 2) or room temperature ionic liquids, have also been developed as a promising electrolytes for the electrodeposition of base metals. In this field, chloroaluminates of alkylpyridinium or alkylimidazolium cation have been well investigated for aluminium3) or alluminium-alloy4-5) electroplating media. On the other hand, in order to avoid high hygroscopicity arising from the use of aluminium chloride, attempts have been made to combine the alkylimidazolium cations with fluorine-containing hydrophobic anions, e.g. BF4-,6) CF3SO3- (TfO-),7) (CF3SO2)2N- (Tf2N-),8) and H(HF)n-ions,9) and investigated for electrodeposition media.'°) Recently, a new series of RTMS consisting of tetraalkylammonium cations and Tf2N- anion, sometimes abbreviated as TFSI- anion, was found independently by MacFarlane et al.11, 12) and Matsumoto et al. 13) This type of RTMS, which is commonly named ""ammoniumimide"" salt, has a wide electrochemical window of ca. 5 V and, thus, the RTMS seems to be suited for practical application as a solvent for the electrodeposition process. In this paper, we report the electrochemical behavior of copper species in an ammoniumimide RTMS, trimethyl-n-hexylammonium bis(trifluoromethanesulfonyl)amide (TMHA-Tf2N)."

Jan 1, 2000

By J. Chen Kuriyama

One method to store hydrogen effectively involves the use of metal complexes such as the alkali-element aluminum hydrides. The hydriding/dehydriding properties of these materials depend on how to prepare them with different structures and microstructures. The present work focused on a high-energy ball milling technique to produce Ti-doped lithium tetrahydridoaluminate (LiA1H4) and lithium hexahydroalanate (Li3AIH6) powders with nanocrystallites. The phase structures and dehydriding/rehydriding characteristics were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller measurement, thermogravimetry, and differential scanning calorimetry. The mechanism of dehydrogenation and rehydrogenation was also examined by means of X-ray photoelectron spectroscopy (XPS). The results on the relation between the reversible hydrogen storage and catalysis function of the Ti-doped complex hydride indicate that both the homogenous distribution of Ti+AI nanoclusters and the Ti¬catalyst with Ti e> Ti3+ (Ti0/Ti2+/Ti3+) defect sites play important roles in optimizing the reversible hydrogen storage.

Jan 1, 2002

By S. A. Davis

In July of 1996, the Kroll process began production again at TIMET's Henderson, NV, manufacturing facility. This, after being shut down for several years due to low market demand for titanium. Faced with limited pond capacity and increasing costs for water and wastewater disposal and storage; process changes were made to recycle water used to wash Kroll titanium sponge back into the sponge leaching process. This idea was revisited from 1992-93, when three consecutive attempts to recycle water for this application were unsuccessful due to early pump failure. Since it was uncertain why previous attempts failed, a complete understanding of the existing system was first sought. This included reviewing piping and flow diagrams; taking field measurements for all the piping, valves, and fittings; analyzing the wastewater composition; and modeling the fluid dynamics and control of the system. The fluid dynamics of the system were modeled by breaking the piping network up into nodes and applying the Bernoulli equation to each segment. The fluid flowrate control valves were modeled for this purpose also and the models were used to help specify the required processing equipment and control ranges and tolerances. Once the project was completed, an operating procedure was prepared for operation, startup, and shutdown of the washer water recycle system.

Jan 1, 1999

By Jian Li, Pei Liu

In recent years FIB has become a powerful instrument to perform ion beam sectioning and site-specific TEM specimen preparation. However, there are still gaps in understanding FIB-induced artifacts. Gallium ion beam damage and specimen heating during FIB milling can produce unwanted artifacts during FIB work.Calculations ofmaximumspecimentemperature increaseshavemostlybeen based on the assumption that ion beam implantation into substrate of infinite size. This deviates from finite specimen volume in FIB TEM specimen preparation that impedes specimen heat dissipation. In this paper, the authors will demonstrate a few commonly observed FIB artifacts, and discuss the concerns of specimen temperature rise during FIB milling process.

Mar 1, 2017

By Jacques Magnaudet, Julie Cranga, Didier Huin, Pascal Gardin

"With the aim of controlling steel grade in steelmaking reactors, IRSID and IMFT are developing a numerical description of the evolution of bubbles in the vicinity of a liquid steel/ slag interface. The objective is to identify the main parameters affecting the hydrodynamics of the various phases. The goals of the present paper are:• To describe the numerical technique developed to predict the multi phase flow including bubbles, liquid metal and slag layer.• To analyze the influence of the absolute pressure on the bursting of bubbles in a RH degasser. Validation is given by comparison with results available in the literature. The major point concerns the distinct behaviors observed whether the pressure is low or high.• To study the influence of the properties of the slag layer (thickness, viscosity and interfacial tension) on the entrainment of liquid metal in the wake of the bubble and on the nature of the projections from the bath surface.IntroductionMost of secondary steelmaking processes use gas stirring for homogenization, removal of nonmetallic inclusions or decarburization under reduced pressure. The bursting of gas bubbles at the metal or slag layer surface produces a beneficial ejection of metal droplets in the low pressure atmosphere, provided that there is no violent projection, which may have detrimental effects on the process.Our objective is to develop a numerical tool to study the phenomena occurring in the vicinity of the bath surface, in particular bubble bursting under reduced pressure and entrainment of metal in the slag layer. In this paper we report the first conclusions of our study. In the first section we describe the numerical model used to describe the three-phase flow and the expansion of the gas bubbles under the effect of the ferrostatic pressure. The second section is devoted to the study of pressure effects on bubble rise and bursting. The third section reports some computational results about the rise of a gas bubble through the interface between the two liquids."

Jan 1, 2001

By Yoshihiko Maeda

It is said that the 21st century will be an era of the remedy of the global environment. In order to reserve natural resources for the future and to avoid the dispersion of heavy metals after usage and to avoid pollution problems, it is extremely important to recycle heavy metals as much as possible by reasonable recovery procedures. The nonferrous metal industry is expected to play a important role in the recycling of heavy metals that are originally their products. From the depressed metal price experienced in Japan in 1980'h due to the sudden change in current exchange rate between US dollar and Japanese yen, one of major nonferrous metal company, Dowa Mining, has diversified its business area not only to the so-called down stream, but also to the environmental business including metal recycling, industrial waste treatment and soil remediation by utilizing technologis and facilities once used or still used for mining and smelting of copper, zinc, lead and precious metals. In this paper some of these applications will be presented.

Jan 1, 2003

By Thomas M. Harris

Cation exchange is not sufficiently selective to be used for the removal of heavy metal ions from a general industrial wastewater. However, if the metals can be converted to polyvalent anions through complexation, they may be removed both selectively and efficiently by anion exchange. This approach, referred to as chelation-assisted anion exchange (CAAE), has been examined using industrial wastewater samples contaminated with Ni2+ and Cr3+. For this particular application, the Ni2+ is complexed with 8-hydroxyquinoline-5-sulfonic acid, and the Cr3+ with sulfosalicylic acid. Removal efficiencies and adsorption isotherms for both the complexants and the complexes were determined in batch-mode tests.

Jan 1, 1994

By Shengping Li, Wei Lv, Gangqiang Fan, Xuewei Lv, Yingyi Zhang

The electrical conductivity of high titania slag, as being an important fundamental physical property utilized in the theoretical understanding of mass transfer phenomena and requirement of practical electric smelting processes, were measured by AC Impedance Spectroscopy using four-electrode method for ternary TiO2–FeO–Ti2O3 slag system based on 85 type of titania slag in Panzhihua in this work. The experiment results show that the slags have a high magnitude of the order of 80–180 s/cm−1 in the whole experimental temperature range from 1523 to 2013 K. The Ti2O3 exhibits very strong effect on increasing the electrical conductivity of high-titania slag since the specific values averagely increase by 55 s/cm−1 with corresponding Ti2O3 content range from 10 to 16 wt%. the X-ray diffraction gram and phases calculated by FactSage are presented and interpreted to discuss the impact of phase change on the electrical conductivity.

Mar 1, 2017

By Louis J. Mittoni

"It is well known that gas injection systems can exhibit a wide range of dynamical behaviours, ranging from linear periodic bubbling through to highly complex turbulent jetting. Recently, it has been observed that an important intermediate regime exists under certain system conditions, where the dynamics are complex in nature yet predictable for short time periods. This paper reviews the evidence to support the above hypothesis, and discusses the invariant quantitative measures such as density, return maps, Lyapunov exponent and dimension which may be used as pattern recognition features in a mOnitoring and control strategy.INTRODUCTIONThere has been a great deal of research on the submerged injection of gases into liquids. This interest is primarily due to the large number of applications in the pyrometallurgical and chemical engineering industries. Gases are typically injected into liquids to achieve goals such as heat and mass transfer, or physical mixing and agitation. Only recently though has the possibility of using the evolution of the gas dynamics as a probe to internal system conditions been raised [1, 2].At very low gas injection rates and small upstream chamber volumes, gas normally disperses in the form of stable bubbles of constant volume [3]. With increases in gas flow rate, the dynamics become more complex, bifurcating into double bubbling, multiple bubbling and complex coalescence behaviour. Irregularities measured in pressuretime series acquired upstream of the injection port under these complex conditions have usually been treated as bothersome noise or contamination to be filtered from the signal and ignored in the analysis. These irregularities, however, may contain physically interesting and useful information on the system from which they were produced if the system may be classified as deterministically chaotic [4]."

Jan 1, 1996

By Manis Kumar Jha, D. D. Pathak, Rekha Panda

Platinum Group Metals (PGMs) play a significant role in the manufacturing of catalysts, super alloys, electronics, space materials, biomedical equipments, jewellery, etc. due to their excellent electrical and thermal conductivity as well as chemical resistivity. The rising demand of PGMs in industrial applications and their limited natural resources have laid emphasis on the development of feasible and eco-friendly processes for the extraction of these metals from different sources to meet their future requirements. Present review reports commercial processes based on pyro-/hydro- and hybrid techniques to recover PGMs from various resources. The salient findings on different processes used for recovery of PGMs have been reviewed with respect to various methodologies and objectives.

Mar 1, 2018

By Alexey T. Kovalev, Irina A. Khabarova, Valentine A. Chanturiya, Igor Zh. Bunin, Elizaveta V. Koporulina

"The paper presents new theoretical and experimental results about mechanisms of disintegration of mineral complexes and structural transformations of the sulfide surface under high-power nanosecond electromagnetic pulses (HPEMP). The heated gas outflow from nanosecond breakdown channels of sulfide minerals under HPEMP is considered. It is shown that the gas outflow from channels can be an additional destructive factor in the processes of the electric pulse discharge disintegration of mineral complexes. It is shown that the effect of HPEMP changes chemical surface composition and, respectively, technological properties of pyrrhotite and pentlandite. Morphology and elementary composition of new micro- and nanoformations on mineral surface of pentlandite and pyrrhotite have been investigated using up-to-date methods of SEM/EDX and Scanning Probe Microscopy. Preliminary electropulse effect on mineral products before flotation allows producing optimal conditions for flotation separation of pentlandite and pyrrhotite owing to forming the new nanophases and defects on the surface of sulfides.IntroductionThe effectiveness of High-Power Nanosecond Pulses in the disintegration and liberation of fine disseminated mineral complexes and the recovery of micro- and nanoparticles of precious metals from refractory ores was demonstrated in [1, 2]. Possible mechanisms of selective disintegration were considered in [1-3]. It has been shown both theoretically and experimentally that electric breakdowns can play an important role in the nanosecond pulsed treatment of milled minerals (e.g., semiconductor sulfides and quartz with particle sizes of 100 µm to 2-3 mm) that are carriers of finely disseminated gold and other valuable components. Electric discharges in such minerals are accompanied by a destruction of integrity in the form of breakdown channels and the formation of a system of cracks around these channels [3]. The development of the domains of induced cracks around the channels is determined by the pressure of evaporated material in the breakdown channel. Upon an instantaneous energy release in a channel (nanosecond discharges), the change in its transverse size and in the gas density and pressure in the channel is determined by (i) the radial motion of the evaporation wave, (ii) the radial expansion of the channel, and (iii) the heated gas outflow from the channel. The evaporation wave moves with a speed on the same order of magnitude as the speed of sound (or greater) and travels a distance of around the initial channel radius, i.e., a much smaller distance than the breakdown channel length."

Jan 1, 2011

By Desmond Cook, Cynthia P. Dogan, Dale Govier, Gary Korth, James C. Rawers

"The microstructural and mechanical properties of iron powders processed in an attrition mill are highly dependent upon the processing environment. Extended high-energy ball milling in argon resulted in nanocrystalline bcc-Fe microstructure, while processing in nitrogen or alloying with carbon resulted in both nanocrystalline bcc-Fe and bct-Fe microstructures. In this U.S. Bureau of Mines study, both X-ray diffraction and Mössbauer analysis were used to show that the infused carbon and nitrogen concentrations were predominantly on the grain boundaries. Explosive consolidation resulted in a fully dense product with microstructure similar to the microstructure of the mechanically processed powder. Hardness values of the compacts correlated highly with grain size, independent of the processing conditions.IntroductionNanocrystalline materials have been theorized and shown to have unique properties that make them interesting for material scientists and promising for material engineering applications. Several conferences have been devoted solely to the techniques of preparing nanostructured materials have been held(l,2,3.). To date, most techniques used to generate nanocrystalline materials produce only a few grams of particles(1). High-energy ball-milling, however, is an efficient and effective technique that can produce substantial quantities of nanocrystalline materials with homogenous chemical composition that cannot be produced by conventional processing techniques(3).Applications and material evaluations of nanocrystalline materials require several grams of solid samples. Because nanocrystalline microstructures' are thermodynamically unstable, producing consolidated macro structures of nanocrystalline material has proved to be very difficult(2,3). In particular, retention of the nanocrystalline microstructure during consolidation of nanocrystalline particles has proven to be a problem. In contrast to many consolidation techniques that require elevated temperatures, explosive compaction uses a shock wave for consolidation( 4,5)."

Jan 1, 1994

Acid mine drainage containing heavy metal ions is a large environmental problem facing the mining and mineral processing industry. The femte coprecipitation is a novel technique for removing heavy metal ions from waste water, recently applied to acid mine drainage. The fenite precipitation is usually performed at high temperature and therefore if applied in conventional manner, it becomes uneconomical to treat large quantities of acid mine drainage. In this paper the ferrite precipitation at ambient temperature-is &died. The possible mechanism of ferrite formation is discussed Experimental results from Noranda Tailing and Berkeley Pit water treated by this process are presented.

Jan 1, 1994

By Heng Yi

The salt lake brines that lithium is extracted from have high chloride levels making the brine very corrosive to stainless steel extraction column internals. This is a significant problem in column scale-up to industrial production. Two types of corrosion-resistant ceramic internals, the hybrid ceramic internal and ceramic plate, were designed and tested under pilot conditions for future industrial application in this field. The hydrodynamic results (Yi et al. Ind Eng Chem Res 56 (4):999–1007 (2016), [1]) show that holdup of hybrid ceramic internal is higher than that of ceramic plate by around 50%, while Sauter mean diameter when using the hybrid ceramic internal is smaller than when using the ceramic plate by around 30%. This results in a larger mass transfer area, hence better mass transfer efficiency for the hybrid ceramic internal. Axial dispersion and mass transfer parameters are also examined (Yi et al. Ind Eng Chem Res 56(11):2049–3058 (2017), [2]). The results show that the column with hybrid ceramic internals has 50% lower axial dispersion coefficient and 50% higher mass transfer coefficient, leading to higher mass transfer efficiency. The transfer unit height of the column using hybrid ceramic internals can be as low as 0.2 m, showing very good efficiency. This is promising for near-future applications. Two-phase computational fluid dynamics (CFD) models have been developed for the two columns with ANSYS FLUENT commercial software. CFD successfully predicts the higher holdup and lower axial dispersion coefficients for the hybrid sieve plate pulsed column as measured in the experiments, and the cause for the difference in performance has been explained with information from CFD.

By Lucas Lopes da Costa, Sergio Neves Monteiro, Rômulo Leite Loiola

"Composites with DGEBA/TETA epoxy matrix reinforced with thinner and continuous bamboo fibers stripped from culms were mechanically characterized by tensile tests. Specimens with up to 30% in volume fraction of aligned fibers were tensile ruptured at room temperature. The results showed a steady increase in both the ultimate strength and the elastic modulus of the composites with the amount of incorporated bamboo fibers. The fractographic analysis by scanning electron microscopy showed evidence of moderate adhesion between the bamboo fiber and the epoxy matrix. This fiber/matrix adhesion by interaction mechanism apparently justifies the improved tensile properties of the composites.IntroductionIn recent years polymer composites reinforced with natural fibers, mainly those lignocellulosic obtained from plants, have been subject to extensive research works [1-5]. Environmental, economical, societal and technical advantages of these composites are motivating their substitution for similar polymer composites reinforced with synthetic fibers. In particular, R & D efforts have been conducted aiming to replace glass fibers composites that are comparatively more abrasive to equipments, non-recyclable, more expensive, heavier and toxic [6]. Among the many lignocellulosic fiber composites being investigated, those fabricated with bamboo stripped fibers, i.e., fibers longitudinally cut from the culm, still need information to support possible industrial applications. Several works, however, have been dedicated to bamboo stripped fibers as possible reinforcement of polymer composites [7-17]. These works reported mechanical properties that could markedly vary with the type of polymer matrix, the fiber disposition (if continuous, aligned, short-cut, mat interlayered, etc) and the test condition."

Jan 1, 2011

By Lucas Barbosa de Souza Martins, Felipe Perissé Duarte Lopes, Nathalia Carneiro Garcia Rosa, Lucas Lopes da Costa, Sergio Neves Monteiro, Rubén Jesus Sanchez Rodriguez

"The fibers extracted from the stem of the banana plant are relatively stronger and have been used as reinforcement of polymer matrix composites. In addition to quasi-static mechanical properties, there is a need to characterize the dynamic behavior of banana fiber composites subjected to thermal and mechanical constraints. In this work, the temperature variation of the dynamicmechanical parameters of polyester composites incorporated with up 30% in volume of banana fibers were investigated by DMA tests. The storage and loss moduli as well as the tangent delta were measured from 20 to 200°C in a TA Instrument operated with the flexural mode at 1 Hz. The results showed that the incorporation of banana fibers tends to increase the viscoelastic stiffness of the polyester matrix. It was also observed changes in the T g and the structure dumping capacity of the composites with increasing fraction of banana fibers.IntroductionNatural fibers with high amount of cellulose, also known as lignocellulosic fibers, have been used from primeval times by our civilization. In the last century, synthetic fibers such as nylon, carbon, aramid and glass fibers gained interest owing to superior strength and precise dimensional control. Natural fibers were then replaced by synthetics in many fields such as textiles and appliances. In the past decades, however, environmental issues drawn, once again, the attention to lignocellulosic fibers as possible substitute for intensive energy-consuming and long term polluting synthetics, specially the glass fiber [1]. In particular, research works have disclosed the potential advantages associated with the use of lignocellulosic fibers as the reinforcing phase in polymer composites [2-7]. Among the advantages it is worth mentioning the renewability, recyclability, biodegradability and the fact that natural fibers are neutral with respect to C02 emissions responsible for global warming. Moreover, as compared to synthetics, lignocellulosic fibers present lower density and cost as well as reduced wear caused to the processing equipment. On the other hand, in terms of composite reinforcement, hydrophilic lignocellulosic fibers present drawbacks such as weak adhesion to hydrophobic polymeric matrices in addition to dimensional limitations and non-uniform properties."

Jan 1, 2011

By Jerry L. Smith

Industry on a whole has not been very receptive to government prodding to implement waste minimization programs. Waste minimization has the appearance of substantial benefits, however, there are underlying difficulties and suspicions that need to be addressed before industry will support pollution prevention initiatives. They can be summarized as follows: - Human behavior resists change, uncertainty, and unknowns. - New waste minimization techniques are difficult to find and research. - Calculating the true cost of present waste practices as well as new techniques being considered is difficult and time consuming. - Getting a consensus opinion of all the individuals affected on the course or technique to be employed in a pollution prevention program. New software products have addressed many of the problems associated with implementing pollution prevention programs: They contain research on a large number of pollution prevention techniques and case studies; they generally are accessed by EPA ID number, chemical name, or synonym; and some programs have the option to print a comprehensive written user-specific pollution prevention program.

Jan 1, 1994

By L. L. Tavlarides, N. V. Deorkar

"Recovery/Recycling of metal ions from industrial process waste streams is a preferred alternative to disposal by conventional techniques. This paper presents methods for preparation of inorganic chemically active adsorbents to be used in fixed bed adsorbers. Methods for immobilization of chelating agents on the inorganic supports are discussed. The prepared adsorbents are characterized to determine coverage density of functional groups, effect of pH on metal ion removal efficiency, regeneration efficiency and uptake capacity. Results from the laboratory scale and bench scale experiments are presented here.IntroductionRemoval of heavy metal ions from processing wastes in various industries is an important problem. Waste streams in electroplating, electronic, catalyst preparation and hydrometallurgical industries contain metal ions such as copper, nickel, chromium, lead, tin, cadmium, silver, gold and platinum. One major concern for the non-ferrous metal industry is secondary recovery of precious metals and cyanide from cyanide leachate from smelter residue and hydrometallurgical waste streams.Recovery methods recently considered include evaporation, electrolyte metal recovery, reverse osmosis (1), adsorption, ion exchange (2,3), membrane separation (4,5) and Solvent extraction. These processes have met with various levels of limited success. The use of liquid ion exchange molecules to selectively extract metal ions for on-site treatment of these waste streams is currently receiving substantial interest (6,7). This interest seems from an awareness of the advances made in the development of commercial extractants for metal ion separation in hydrometallurgical industries (8). However, separation by solvent extraction processes is generally considered to be economical in the range of aqueous metal ion concentrations from 0.01 to 1.0 mol/lit (9). In order to exploit the selectivity of chelating agents, the idea of immobilizing chelating agent into a solid matrix has attracted growing attention in recent years. Many supports such as inorganic oxides, organic polymers, cellulose powder and polyurethane foam can be used for immobilization of chelating agents. Over the last decade, considerable efforts have been directed toward attachment/introduction of chelating agents into a polymer matrix (10,11). Inorganic supports as compared to polymer supports provide high mechanical strength, chemical and thermal stability, and high reaction rates due to open pore structure. On the contrary, organic resins shrink and swell, thus affecting mass transfer (12). Many of the disadvantages of polymer supports can be excluded by the use of inorganic supports. Innovative use of immobilization techniques can produce inorganic chemically active adsorbents with comparable capacity, stability and reaction rates. Consequently, the objective of our program is the development of inorganic chemically active adsorbents to be used in a fixed-bed unit operation as an alternative heavy metal ion recovery process. Methods of preparation of inorganic chemically active adsorbents, (ICAAs) characterization and applications are discussed in this paper. A brief summary of the results from laboratory scale studies and bench scale studies is presented."

Jan 1, 1996