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By Wenjie Zhu

Chromite ore processing residue (COPR) is a hazardous waste containing high concentration of chromium. We describe here a pioneer trial of detoxification of COPR in column reactor with an indigenous chromate reducing bacterium Leucobacter sp. Ch1, which showed high chromate reducing ability at high pH. Under the optimum conditions, at 30°C and pH 10.0, pH of leachate decreased from 10.3 to 8.3, and Cr(VI) concentration in solution decreased to zero mg L-1, and 76.4% of Cr(VI) was removed from COPR samples. The leaching toxicity of detoxified residue was 1.1 mg L-1 that was lower than national standard of China.

Jan 1, 2008

The high pressure acid leach process (HPAL) is being commercially used in four plants around the world to treat limonitic laterites. The two major operating costs of the HPAL process are the sulphuric acid and the energy required to heat the pulp to the desired temperature (>240°C). As an alternative to acid injection and steam heating, the in-situ generation of sulphuric acid and heat, produced during the high temperature pressure oxidation of sulphur-bearing materials blended with laterites, has been investigated at the laboratory scale. Various sources of sulphur have been examined, in particular, elemental sulphur, pyrrhotite and a Cu-Ni low-grade bulk concentrate. Under the proper blend ratios, all sulphur sources tested generated sufficient acid to result in equivalent nickel and cobalt dissolutions. A significant improvement to the process economics can result from the addition of sulphur sources containing valuable by-products, such as nickellcobalt andlor precious metals (gold and PGMs). This is especially true in the latter case, when the HPAL can be operated under Platsol conditions (i.e. with the addition of 5-10g/L of chloride), to dissolve the base metals and precious metals simultaneously in the autoclave. Various examples of the application of this concept are presented, together with a brief discussion of its implication on the autoclave design and the downstream processes to recover the values from the leach solutions. Keywords: limonite, co-treatment, acid consumption, sulphur, sulphur compounds, pressure acid leach (HPAL, PAL), Platsol process

Jan 1, 2004

By Paul Van Negan

During the last decade, MHO has continued to diversify the feed. of its Hoboken smelter. The range of feed materials including larger proportions of precious metals has been extended and the production of minor metals has been developed. These diversifications have required further improvements at the smelter. Attention has been particularly focussed on an increase of productivity, compliance with emission standards and achievement of the highest recoveries of valuable elements. The assaying and sampling facilities have been considerably expanded and the different processing steps of the smelter are now also systematically controlled and managed by simulation models. The charge preparation at the sinter plant, returns handling, sinter conditioning and corresponding ventilation systems have been completely renewed. The annual smelting requirement is now achieved with two blast furnaces instead of three. This is the result of rebuilding and enlarging one of the furnaces and, of a completely new concept of the charge proportioning and charging systems, together with oxygen enrichment and blast air preheat. Ventilation capacity has also been drastically increased. A 7 MVA electric furnace for cleaning the slag from both blast furnaces. contributes to improving the overall metal recovery.

Jan 1, 1990

By Katsunori Yamaguchi

A new technique for the removal of tramp-elements from steel scrap has been required from the viewpoint of saving energy and protection of environment. In order to obtain fundamental information on the removal of copper, tin and zinc from molten iron, the extraction method by using of phase separation in the liquid Fe-Pb-C system was investigated at 1453K A mixture of iron, lead and carbon melted in a carbon crucible separates into two phases of lead and iron containing carbon. The compositions on the miscibility gap in' the Fe-Pb-C system are 95A%Fe-4.5%C-0.l %Pb and 99.9%Pb-0.1 %Fe. The distribution ratios of copper, tin and zinc between the lead and the iron phases, Lx=[masso/uX in molten Pb]/(masso/uX in molten Fe), are 2.2, 2.2 and lA, respectively. Seventy percent of copper and tin from iron scrap can be eliminated with comparable lead addition. Gold, silver and palladium are enriched in the lead rich phase, on the contrary platinum and rhodium are more distributed to the iron rich phase than to the lead phase.

Jan 1, 2003

By Yuan Lu, Yiming Rong, Richard D. Sisson Jr

With the development of quench technology, there is a trend of using gas quench to replace liquid quench for less distortion and residual stress. The fundamental difference between the liquid and gas quench is the heat transfer coefficient, not only the values but also the shape of the curve as a function of temperature. The equivalent heat transfer coefficient for the liquid and gas quench is analyzed by simulations and experiments. Even it may result in the same hardness in the liquid and gas quench, the steel microstructure may be different because of the different cooling processes, and therefore other steel properties, such as toughness, may be different. The cooling process, microstructures and properties such as hardness and toughness should be examined when designing the liquid or gas quench processes.

Jan 1, 2015

By A. S. Block-Bolten

Two innovations in nickel-arsenic separation have been studied on a laboratory scale. The first requires only a nitric acid atmospheric leach without preliminary roasting and leads to favorable final conditions for precipitation of arsenic as highly stable FeAsO4, The second is an NaOH-H2O2 pressure leach which is an alternative to the known NaOH-O2 pressure leach. Either method offers the possibility of rapid and efficient separation of nickel from arsenic and is applicable, for example to the high grade niccolite deposits in the Great Slave Lake area of northern Canada.

Jan 1, 1982

By N. Menad

. Electronic wastes are heterogeneous mixture, with mainly copper, aluminium and steel attached to or mixed with various types of plastics and ceramics. In general, small amounts of precious metals are incorporated in this mixture. Today, these components constitute an environmentally problematic fraction in disposal. Their physico-chemical characteristics have been investigated through chemical, x-ray diffraction, infrared spectroscopy, scanning electron microscopy and thermal analysis.

Jan 1, 2000

By Shoukun Wei, Cong Wang, Lin Cheng, Zhiyu Qiao, Jingkui Liang, Weidong Zhuang

"The subsolidus phase relations in the Sm2O3-CeO2-CuO ternary system sintered at 1000°C in air have been investigated by X-ray powder diffraction. The system can be divided into two ternary phase regions and three binary phase regions. Solid solution Sm2-xCexCuO4-y is the only ternary phase in the system. The maximum solid solubility was confirmed to be x = 0.2. The crystal structure, oxygen content and superconductivity of the solid solution Sm2-xCexCuO4-y have been investigated.I. INTRODUCTIONAfter the first discovery of the superconducting ceramic system La-Ba -Cu-O[l] with Tc = 30 to 40K, other families of cuprate-based ceramics have been synthesized with higher critical temperature. These oxides include the R-Ba-Cu-O (R: rare earth) systems (Tc=90K or so)[2,3], the Pb-Sr-(R,Ca)-Cu-O systems (T c = 50 to 100K), the Bi-Sr-Ca-Cu-O systems (Tc=80 to 105K)[4], the T1-Ba-Ca-Cu-O systems (Tc=85 to 125K)[5], the Hg-Ba-Ca-Cu-O systems (Tc=90 to 150K)[6,7], and some others. The improvement of Tc is very rapid. The measurement of the Hall and Seebeck coefficients shows that they all are p-type superconductors. In 1989, Tokura et al.[8] discovered the superconductors R2_XCexCU04_y(R = Nd, Pr, Sm) with Tc=20 to 24K (onset) and found that the charge carrier is electron in contrast to their hole doped counterparts. This discovery increases the fundamental understanding of the cuprate-based superconductors by comparing their characteristics and mechanisms to those of the p-type superconductors.One of the outstanding features of these n-type superconductors is the difficulty in obtaining samples in good charactors, such as the difficulty in obtaining zero resistivity state in single crystal or bulk samples; the semi-conductivity of bulk samples in ordinary state (opposite to the superconducting state) and a reducing reaction involved before the superconductivity has been found[9]. Therefore, it is necessary to optimize the sample preparation of the n-type superconductors. All the n-type superconductors have been found· considerable solid solubility. The compositional variations play a governing role in the carrier doping of the superconducting phases. Also, it is vital to the ceramic processing of superconductors to identify the compatible phases in the phase diagram. Finally, there is always the possibility of finding additional compounds, both superconducting and non-superconducting, in an unexplored system."

Jan 1, 1996

By Adegbenjo Adewale Oladapo, Ibitoye Simeon Ademola, Ladiipo Olufemi Akinbiyi, Adegbola Adekunle Amos, Adeboje Taiwo Bode, Raji Fatai Olasunkanmi

The combined effects of the addition of Silicon (Si) as alloying element and low temperature annealing on the tensile properties of 70/30 brass with Nickel (Ni) and Iron (Fe) contaminants is investigated in this paper. Melts of cartridge brass were made to which 0, 0.5, 1, 2, 3 and 4 wt % of Si was added. These were sand cast into rods of 600 mm by 10 mm diameter and were thereafter machined into standard tensile test samples. Some of these samples were annealed in a muffle furnace at temperatures of 250, 300, 350, 400 and 450 oC respectively and the others were used as control. Subsequently, all the heat treated and non heat treated samples were subjected to tensile tests on a Hounsfield Extensometer and the load – extension plots retrieved were analyzed. Microstructural characterizations of the samples were carried out using Accu-Scope Optical Microscope. The results showed that cartridge brasses subjected to alloying and annealing treatments had improved tensile and yield strengths. However, the tensile properties were increased and maintained within acceptable limits at stress relieve annealing temperatures.

Jan 1, 2015

By M. C. Esposito

Seven pyrite samples purified from coal sources and one ore source pyrite (for comparative purposes) have been characterized by chemical and mineralogical analyses, inherent floatability, apparent specific gravity, surface area, semiconductor type, optical anisotropy, dissolution and oxidation rate. The data clearly demonstrate that pyrites from various coal sources differ not only from ore pyrite but from each other as well.

Jan 1, 1987

By Raymond F. Dalton

Despite the ready availability of numerous zinc sources, the process of solvent extraction- electrowinning (SX-EW) has as yet found little favour in the zinc industry. It is suggested that this is largely due to the previous lack of availability of suitable selective reagents having the particular features required to enable them to fit in to a solvent extraction-electrowinning based process for zinc, particularly with regard to strength and selectivity for zinc over iron. This paper describes work on the development of new selective extractants for the recovery of zinc from both sulfate and chloride aqueous solutions and suggests how they might be integrated into new zinc processes.

Jan 1, 1994

By Ricardo A. Valls

The Sechol Nickel-Cobalt Laterite Project is located in East-Central Guatemala, 140 km northeast from Guatemala City. In-situ resources in the immediate Sechol area, including those on other mining concessions contain 133 million tonnes of mineralization, grading 1.5 1% nickel. Considering the ever-increasing market for these metals, and the potential quick return on the initial investment, Jaguar Nickel Inc. is confident that by late 2006, it will be producing the first nickeltcobalt hydroxides from Guatemala. The path from now until the production stage passes through a pre-feasibility study, scheduled for completion by mid 2004, and bankable feasibility by mid 2005. Jaguar's objective, however, is not only to have a producing nickel-cobalt mine by late 2006, but also to continue with the exploration work in order to make Guatemala one of the world's leading nickel-cobalt producers. The Sechol group of deposits is conformed of several lateritic pockets, delimited by tectonic faults, and hosted by ultramafic rocks of the Sierra de Santa CW. ophiolitic belt that intruded the Maya Continental Block during the Early Tertiary age. The intrusive is mainly represented by a layered sequence of dunites, peridotites, and pyroxenites, usually strongly serpentinized. Existing data indicate that these rocks underwent fractional crystallization, and probably some degree of magma mixing and contamination previous to their main tectonic event. The most complete profiles are usually present over weathered dunites and serpentinites, while on top of the less altered pyroxenites, there is usually the formation of only a limonitic zone. The relative complexity of the ophiolitic belt explains the variety of mineral resources in the area, which include Ni-Co-Fe laterite, chromite, bauxite, magnesia, and also has the potential for gold, PGMs, and precious and semi-precious stones such as jade, nephrite, and chrysoprase. Metal recovery from the Sechol deposit will be based on an atmospheric chloride process, followed by solution purification, production of an intermediate nickellcobalt hydroxide suitable for sale, and finally acid and magnesia recovery by standard spray roasting technology. The chloride process will allow exploitation of the whole lateritic profile to produce 20,000 Mt of nickel hydroxide and 800 Mt of cobalt hydroxide per year. The exploration work completed to date has concentrated mostly on the Sechol group of deposits, representing less than 5% of the current land position of Jaguar in Guatemala. Within Sechol, the company has identified a large pocket of more than 5 Mt of laterites grading 2.1% nickel and 0.08 % cobalt as a startup pit "El Inicio". Including the work previously completed Keywords: Laterite deposits, Ophiolitic Belts, Central Guatemala, Nickel, Cobalt

Jan 1, 2004

By G. L. Liu

"Deformation Banding ( DB ) in cold rolled mild steel has been experimentally established by microstructure investigation. Deformation banding model includes such deformation mode when it is applied to rolling texture simulation. The cause for the occurrence of deformation banding is the reduction of the total work for plastic deformation through a relaxation of the deformation constraints. In the first DB model, all grains are assumed to band from the first deformation step. Such an unrealistic assumption has been eliminated in the new model by the introduction of a banding criterion based on an energy minimizing approach. The prediction is closer to the measured texture by applying banding criterion and setting critical resolved shear stresses (CRSS) ratio for { 110 } and { 112 } slip modes to 0.85.IntroductionBased on the continuum theory of plastic flow and deformation mechanism of crystallographic dislocation slip, Taylor's FC ( Full Constrain ) theory [1] has been widely used in texture modeling. As the process of cold rolling of sheet materials produces a microstructure consisting of elongated or equiaxed flat grain or cell, the ""lath"" and ""pancake"" relaxed constraints ( RC ) models [2, 3] were introduced as the successful improvements over the classical FC model. It has been also recognized that crystals may split into different orientations during deformation and the term deformation banding is used to describe such deformation processes [4, 5]. Lee et al. [6, 7] pointed out that the success of the RC theory in predicting textures depends on the physical processes of deformation banding. They developed so called Deformation Banding ( DB ) model by considering DB in the longitudinal plane to be accounted for by the RC method and allowing DB in the rolling plane. DB model was applied to simulate the texture development in bee case [8], the predicted bee rolling textures are in reasonable agreement with the measured textures. In the first DB model, however, all grains are assumed to band right upon the first deformation step. A banding criterion was formulated [7] which states that DB will occur if the work used in DB model is less than that in RC model. Such criterion has been incorporated into the original DB model for texture simulation and is referred to as DBC ( Deformation Banding Criterion ) model."

Jan 1, 1998

By Ross R. Bhappu

A theoretical and experimental investigation into pyrometallurgical refining of chloride leach/electrowin copper is described. The two techniques investigated were (i) vaporization and (ii) gaseous halogenation. Experiments were carried out with a packed bed of electrowon copper crystals and a boat of melted copper crystals. Nitrogen gas and Freon 12/nitrogen mixtures were used as the carrier and reac.tive gases. Vaporization was found to be effective in removing Bi, Pb and S while halogenation was effective. in removing As, Bi, Pb, S and Sb. Silver resisted all attempts at removal. Iron was removed but less effectively than the other impurities.

Jan 1, 1985

By B. Bichel

For the last 70 years, molten blister copper has been transferred by rail in hot metal cars from the Copper Cliff Smelter to the Copper Cliff Copper Refinery (ex Ontario Refining Company) where it was processed in two (2) reverberatory anode furnaces by poling with logs, cast on four (4) wheels, and then electrorefined. This practice was modernized in 2001 with the installation of two (2) rotary anode furnaces at the. Copper Cliff Smelter which employ steam and. natural gas for reducing and which provide a significant reduction in emissions. A new casting shop with a single anode casting wheel is used to cast regular and stripper constant weight anodes which are transported by truck to the Copper Cliff Copper Refinery for anode preparation and electrorefining. This paper provides an overview of the copper circuit at the Copper Cliff Smelter and a description of the CDN$31 million capital project.

Jan 1, 2002

By Nobumasa Kemori

Six kinds of copper '90ncentrates. were treated individually in a ,pilot scale. Outokumpu flsah smelting furnace ~n order to study their ?flash smelting behavior with respect to oxygen efficiency and dust generation. The copper concentrates tested were selected from the more than twenty sources which are treated at the Sumitomo Toyo copper smelter, so as to provide a wide range of chemical composition in terms .of Cu, S,Fe, Pb + Zn + As, and Si~ content. Oxygen efficiency 'and dust generation rates obtained in 'the experiments ranged from 80% ,to 108% and 11% to 20%, respectively. Relationships between these results and experhnental conditions such as chemical and mineral composition of the copper concentrates, flux ratio, fuel consumption and so on are also discussed quantitatively in this paper.

Jan 1, 1998

By R. J. Wesely

The paper describes the various methods which are currently being used or considered to refine gold and silver. These methods are then compared on a technical and economic basis. Conclusions are drawn on the factors which might influence the choice of process for different feed stocks and economic constraints

Jan 1, 1990

By Wayne Bell, Shivanand A. Borkar, Anish Upadhyaya, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"A refractory ore body located in Michigan’s Upper Peninsula contains high concentrations of nickel and copper chiefly occurring in the minerals pyrrhotite, chalcopyrite, and pentlandite. Refractory ore bodies are difficult to treat by conventional mineral processing methods so microwave pre-treatment of the ore is employed to increase metallic-particle/host rock liberation by making use the differential thermal expansion properties of the mineral phases that absorb microwave energy. The Curie temperature measurement of metallic-bearing particles is in agreement with the known value for pyrrhotite occurring at 325°C. A nickel-rich iron sulfide mineral is found to be in occurrence and also appears to be magnetic under BSE imaging. It is shown the ore particles heat rapidly when exposed to microwave radiation for short durations of time mainly due to the high concentration of ferromagnetic mineral phases. Rapid heating causes thermal expansion of constituent mineral phases that produce cracks within ore particles. SEM imaging shows fracture occurring along grain boundaries and throughout host rock matrix. Ball milling experiments show an increased grindability of the ore resulting in a decrease in work index values.IntroductionCrushing and grinding operations consume 50-70% amount of energy used in mineral processing operations [1]. All these processes involve high energy impact of surfaces to develop compressive stresses that produce cracks to initiate breakage of particles. Microwave pre-treatment of certain types of ore might provide an energy savings to these type grinding processes by taking advantage of the tensional forces produced by selectively heating microwave absorbing type mineral phases. The heating of ore particles produces cracking by thermal expansion of the constituent mineral phases. Conventional heating has been investigated and shown to positively aid in grinding processes but determined energy inefficient to be used commercially."

Jan 1, 2011

By Kathryn A. Mrotek

The textural growth patterns of nodules from two areas in the North Pacific and the South Pacific are characterized by mottled, columnar and compact-type zones. Amorphous material (mainly iron and manganese hydrox-ides) is a botryoidal-forming phase in the mottled and columnar zones. Crystalline material (platy crystals of birnessite and crystallites of todo-rokite) is found primarily in the mottled zones on botryoidal structures or as long-protruding structures growing onto that portion of the nodule in contact with the underlying sediments. The long-protruding mottled zones contain little or no biogenic debris, suggesting that these zones grew un-interruptedly within the underlying sediments. The coalition of spheroidal knobs comprising some of the nodules also suggests a relatively long residing time within the sediments. It appears that crystalline material (the usual host to associated valuable metals) forms in a quiet environment and as a result of direct nodule association with the underlying sediments.

Jan 1, 1982

By T. H. Jeffers

The U.S. Bureau of Mines' Salt Lake City Research Center. has developed porous polymeric beads containing immobilized non-living biological materials for extracting metal contaminants? from wastewater&. Immobilized biological materials include peat moss, algae, biological polymers, and other materials that demonstrate high .affinities for heavy metals. The beads, designated as BIO-FIX beads, have distinct advantages over traditional methods of utilizing biological materials in that they have excellent handling characteristics . and can be used in conventional processing equipment or low-maintenance systems.. Toxic metals such as copper, cadmium, zinc, lead, and mercury are several of the many heavy metals effectively removed from mine wastewater& using B'IO"FIX beads. Continuous cyclic testing indicated that the beads continued to produce treated effluents which met National Drinking Water Standards (NDIJS) after 175 loading-elution cycles, Adsorbed metals were removed from the beads using dilute ?mineral .acids. In many cases" the extracted metals were further concentrated to enable processors to reclaim the metals, thus minimizing the generation of a hazardous sludge. Tests indicated that use of the beads in a low-maintenance system was particularly effective for treating remote acid mine drainage waters? and small toxic seeps from hardrock mining districts ..

Jan 1, 1991