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By R. Conor, O&apos

Wastewater treatment systems, both industrial and municipal, produce large quantities of sludge which require disposal. Sludge disposal poses significant environmental liabilities, logistical problems, and economic burdens. Minergy Corporation has developed and implemented several new technologies for the recycling of such high volume wastes as sludge, ash, and foundry sand. These technologies perform mineral recovery from the waste material, converting them into construction material and industrial feed stocks which are inert, marketable products. With a continuously operating processing system installed at the waste source, these technologies reduce handling, eliminate downstream liabilities, and reduce disposal costs.

Jan 1, 1999

By Bin Xu, Qian Li, Qiang Zou, Yongbin Yang, Long Hu, Tao Jiang, Xuefei Rao

The recovery of palladium from the chloridizing leaching solution of spent Pd/Al2O3 catalyst was studied mainly by sulfide precipitation tests and chemical composition analysis. The effects of key parameters including sodium sulfide concentration, pH, addition rate, temperature, and stirring speed on palladium precipitation efficiency are systematically investigated and optimized.

Mar 1, 2017

By Michael R. Grubbs

The Bureau of Mines is currently developing methods for reclaiming the metal and mineral values contained in unburned urban refuse. One important phase of this research deals with recovering Mastic from shredded refuse using in electrodynamic separation process. The results of this study have indicated that mixed plastic concentrates analyzing 99.4 percent plastic can be consistently recovered from the light material fraction of shredded refuse, leaving a mixed paper traction analyzing 99.9 percent paper. Recovery of the plastic exceeds 99 percent.

Jan 1, 1972

By L. Paulino, C. E. Zangiacomi, J. Yamamoto

"This paper presents the learning from Alcoa Po9os de Caldas Smelter in Brazil, after several energy restrictions resulting from the failures of three rectifier units at its power switchyard. Starting on December 27th, fuses and diodes failed in three rectifier units of Potline #1, causing a long and dangerous power interruption. Even after current was reestablished, amperage was only 70% of the line target leading to a bath freezing process that lasted for around 48 hours. The process engineering team played with several potroom parameters as pot resistance, bath and metal levels, alumina feeding and bath chemistry in an attempt to minimize impact on the potline metal output and energy consumption. As it will be illustrated, the first battle was to keep the pots running on a ""survival"" approach. After that, several changes took place on the procedures used to run at reduced current which were considered rather successful. Finally, some recommendations will be given to foresee and prevent transformers and rectifiers from undesirable failures."

Jan 1, 2006

Provide a means of recovering precious metal values from finely ground tailing materials. Approach Determine the procedures needed for agglomerating the finely ground material for subsequent heap-leach cyanidation of the precious-metal-bearing tailings. Applying Agglomeration/Heap-Leaching to Fine Tailings Agglomeration technology was developed by the Bureau of Mines to provide cost-effective recovery of precious metal values though better heap leaching of clayey or low-grade ores. While many precious metal producers have adopted this technology to reclaim precious metals from crushed ores and wastes, other operations have experienced problems in using the heap leaching technique effectively on piles of fine tailings. In contrast to the coarser ore and waste material, most tailings piles contain more than 50 percent minus 200 mesh materials with no coarse material. Fine particles and clays present in the pile can impede 8 uniform flow of the leaching solution through the heap, thus preventing efficient and cost-effective precious metals recovery.

Jan 1, 1986

By G. Mei

"This study explores froth flotation and selective flocculation methods to recycle waste phosphors containing several rare earth elements, namely, yttrium (Y), europium (Eu), cerium (Ce) and terbium (Tb). The effects of the presence or absence of collector and of flocculant and their dosages, as well as the pH, were investigated. Reverse flotation resulted in concentrates with grade of 27.03 percent and recovery rate of 71.36 percent, while flocculation resulted in concentrates with grade of 31.43 percent and recovery rate of 91.28 percent. The flotation and flocculation behaviors were further analyzed by X-ray diffraction analysis, zeta potential measurements, particle size distribution and other methods. The successful separation of rare earth minerals by flotation was attributed to the selective adsorption of the collector onto quartz, making it particularly recoverable by reverse flotation so as to be separated from the valuable materials. The analysis of the particle aggregation process indicated that its better flocculation performance was due to the selective adsorption of flocculants onto the unwanted materials, enlarging the flocculant sizes by forming aggregations and facilitating the separation of rare earth minerals from waste materials based on different settling rates. IntroductionBecause waste phosphors pose the problems of heavy environmental burden and high risk to human health (Hu and Cheng, 2012) as a result of containing heavy metals such as mercury and manganese (He et al., 2006; Lucas and Emery, 2006), they have received added attention as urban mining resources for extracting rare earth elements (REEs) like yttrium (Y), europium (Eu), cerium (Ce) and terbium (Tb).At present, chemical processes such as acid leaching, alkali fusion, roasting and extraction are the primary methods for recovering REEs from waste phosphors (De Michelis et al., 2011; Li et al., 2012; Li, 2010). With these strategies, phosphors can be effectively decomposed and their REEs extracted. After the removal of impurities, the REEs can be efficiently precipitated by adding an H2C2O4 solution (Porob et al., 2012). Although relatively high recovery rates are achieved, those processes entail high energy consumption and can cause severe environmental pollution."

Jan 1, 2017

By Q Xin, X Shengming, C RuÆan, Z Zhigeng a

The optimum defluorinating conditions for Sichuan bastnasite crude ore were determined by orthogonal experiments. Over 95 per cent fluorine in the crude ore was stripped by roasting 30 minutes of the crude ore with Na2CO3/ore =0.25 at 650oC. The stripped fluorine crude ore was further treated by NH4 Cl to recover rare earth. Above 95 per cent rare earth can be leached by water after the stripped fluorine crude ore mixed NH4Cl(NH4Cl/ore =1:1) roasted 1 h at 325oC. At the same time, the rare earth leaching solution contains little Fe, Si and Al. Therefore it is propitious to further purify the solution and recover rare earth.

Jan 1, 2000

By N. C. Nissen, J. A. Thomas, A. Illis, K. N. Subramanian

Successful miniplant and laboratory testwork has indicated that high purity selenium can be produced from copper refinery slimes. The recovery technique fits into existing unit operations, and the selenium recovery in the new process was close to 99%. This recovery virtually eliminated any selenium being processed through the smelting stage. In addition, miniplant tests conducted at Inco Metals Co.'s J. Roy Gordon Research Laboratory in Mississauga, Ontario, have demonstrated the reliability of the process with respect to extractions, product quality, filtration characteristics, and effluent disposal. Inco's copper refinery at Copper Cliff, Ontario, produces about 500 t/d of copper with the anode slimes fall typically averaging 0.5% of the throughput. Investigations relating to the treatment of slimes within Inco's R&D have been conducted on several occasions since 1959, when the available alternatives such as acid or alkaline pressure leaching, aqueous or high temperature chlorination, roasting, smelting, etc., were considered. Interest in slimes processing was revived recently to meet increasingly stringent environmental standards and to replace equipment of a relatively old plant.

Jan 11, 1978

By Roshan B. Bhappu

Selenium is found most frequently as an accessory mineral in the ores of lead, copper, and nickel, and is recoverable as a byproduct in the treatment of many of the ores of these metals. The geographic distribution of the selenium industry closely follows that of electrolytic copper, with the United States and Canada producing approximately 75% of the total output of the non-communist world. This situation is problem number one for selenium-its dependence upon the electrolytic refining of copper- for this byproduct source is not sufficiently flexible to permit a normal supply-demand balance. Furthermore, selenium has become a strategic material in short supply. Thus, new sources are being sought by both government and private interests. Although considerable attention has been given to this effort during the last few years, hardly any research has been published concerning the recovery of small amounts of selenium present in low-grade deposits. In such ores the metal occurs as native selenium or as selenides of iron, copper, silver, lead, and bismuth. In recent years, some native selenium (in both the gray and red form) and selenides, especially iron selenide (ferroselite), reportedly have been found in the sandstones of the Morrison formation near Grants. New Mexico. Similar occurrences have been reported in the Hagan coal basin, in Sandoval County, New Mexico. Samples from New Mexico ores have contained from a trace amount to as high as 0.425% Se. Some of the samples from uranium mines in the Grants area represent mixed ore and mill feed fur uranium reduction plants. In such cases, the selenium usually is reported as an impurity and is lost in the tailings. At present, no attempt is made to recover this waste metal.

Jan 8, 1962

By A. D. Zunkel

Increasing amounts of electric arc furnace dust (EAFD) are being generated worldwide as more steel is produced from electric furnace melting of galvanized steel scrap. In most countries, the management of this material is a costly technical, economic, and legal problem for minimill steelmakers. Many technologies and processes are being developed and implemented worldwide to manage this material to recover contained zinc, lead, and iron values and render it nonhazardous. These processes are pyrometallurgical, hydrometallurgical, or hybrid in nature. Some produce zinc oxide, some zinc metal, some lead metal, and some lead cement. Some are successful, some have failed, many are dormant. or abandoned, and others continue to be developed and emerge. This paper updates the current status of 20-30 processes in various stages of commercial application and development used worldwide to manage EAFD and recover its nonferrous, particularly zinc and lead, and ferrous values.

Jan 1, 2000

By D. E. Karvelas

Argonne National Laboratory is conducting research to develop a cost-effective and environmentally acceptable process for the separation of high-value plastics from discarded household appliances. The process under development has separated individual high purity (greater than 99.5%) acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS) from corruningled plastics generated by appliance-shredding and metal-recovery operations. The process consists of size-reduction steps for the commingled plastics, followed by a series of gravity- separation techniques to separate plastic materials of different densities. Individual plastics of similar densities, such as ABS and HIPS, are further separated by using a chemical solution. By controlling the surface tension, the density, and the temperature of the chemical solution, we are able to selectively float/separate plastics that have different surface energies. This separation technique has proven to be highly effective in recovering high-purity plastics materials from discarded household appliances. A conceptual design of a continuous process to recover high-value plastics from discarded appliances is also discussed. In addition to plastics separation research, Argonne National Laboratory is conducting research to develop cost-effective techniques for improving the mechanical properties of plastics recovered from appliances.

Jan 1, 1996

By A. Pawelczyk, D. Hreniak, E. Zych, W. Strek, K. Grabas, A. Ostrowski

"Nowadays recycling became an important rare earth elements (REE) source, which allows to reduce their demand for extraction from natural deposits. At present, the used fluorescent lamps and old type TV or computer monitors kinescopes are selectively collected and undergo processing in the system of recycling. It has been estimated, that utilization of such waste would be sufficient to cover the REE demand for the next 5-8 years. In the developed process, the luminophores were separated from the electronic and electronic waste materials, and processed by hydrometallurgical methods to obtain concentrated REE in form of oxides. INTRODUCTIONInternational Union of Pure and Applied Chemistry (IUPAC) defines the rare earths as a set of seventeen chemical elements, specifically the fifteen lanthanides plus scandium and yttrium. They are considered the most important indicators of the developed technologies and techniques. Rare earths are used, amongst others, for the production of magnetic and superconducting materials, ceramics, lighting, catalytic converters, advanced electronics and alloys. The demand for RE continually increases, similarly to many other primary raw materials. Globalization, the growing demand for limited resources of raw materials, the policy of the countries controlling the raw material market and the economic crisis became a spur for new programs of socio-economic development of the European Union (EU), with particular regard to EU safety for commodities in intermediary as well as long-term horizons (COM 2008), COM 2011).EU countries import most of metallic and chemical raw materials important for their economy. In 2008 a detailed program named Raw Material Initiative was announced. The increase in demand for most raw materials having special importance for the development of technology, and access to of raw materials security of supply affect the future economies of the UE member states and other developed countries."

Jan 1, 2012

By H. F. Anderson

The Palabora Mining Company Ltd. is probably best known for its production of copper since 1965. The success of the PMC mine lies in the outstanding technical and highly organized efficiencies applied to the massive mining, transportation, and treatment operations necessary to produce profitable copper. We are not however going to discuss the well-known copper operation but the extremely successful recovery and marketing of Baddeleyite by the PMC group. Let us first review the extraction process at the Heavy Minerals Plant. Non-magnetic ground ore from the copper magnetic separators is processed in the Heavy Minerals Plant for the extraction of the "heavy minerals" uranium and zirconia (Baddeleyite). Thorium is also present as a potentially recoverable mineral. The content of the minerals in the feed is probably the lowest in the world to be treated commercially. Minerals are separated from the waste ore by a gravity separation process in which the high density minerals segregate preferentially in a waterborne system.

Jan 1, 1985

The methods employed for the addition of uranium to steels and cast iron in the Physical Metallurgy Division are outlined. It has been found that the segregation of? uranium is a major problem in aluminum and/or silicon killed steels and that the cooling rate is important in al-lowing the segregate to settle to one area, which can subsequently be discarded. The unsegregated areas were found to be extremely low in total oxygen, acid insoluble aluminum (AizOg) and, in some cases, slightly lower in nitrogen. Uranium recoveries, based on analyses of the unsegregated areas, were quite constant, at about 45 per cent, regardless of the type of uranium master alloy used for the addition. No segregation of carbon, manganese, silicon, sulphur, phosphorous, chromium or copper was observed in these steels. In commercial heats, the recoveries ranged from 7 to? 29 per cent for ladle additions to oxygen converted steel. When the steel was fully deoxidized prior to the uranium addition, recoveries ranged from 49 to 66 per cent, regardless of the steelmaking process.

Jan 1, 1964

By Shaohua Ju, Feng Jiang, Chuanhua Li, Jinhui Peng, Libo Zhang

A T-junction microchannel is proposed to overcome the existing problems in conventional solvent extraction of indium from zinc hydrometallurgical process. Experiments were performed to separate In3+, Fe3+ and Zn2+ from sulfate solutions using Di-(2-ethylhexyl)phosphoric acid (D2EHPA) as the extractant. The effect of parameters such as pH, microchannel size and contact time on the extraction behavior of In3+, Fe3+ and Zn2+ was investigated. At contact time of 2.52 s and initial solution pH of 0.48, the extraction efficiency of In3+, Fe3+ and Zn2+ was 99.13%, 8.31% and 2.45%, respectively and separation factor of In3+/Fe3+ and In3+/Zn2+ were almost 1229.54 and 4864.98, respectively. Then, the loaded organic phase was stripped in T-junction microchannel. At contact time of 33.6 s, 99.64% of stripping efficiency of In3+ and stripping equilibrium were reached, while concentration of Fe3+ and Zn2+ was lower than 0.01 g/L with good separation of In3+ from Fe3+ and Zn2+.

Jan 1, 2016

By S. E. Maddigan

MANY experimental and theoretical investigations have been made on the processes involved in annealing and recrystallization of metals. Most of these, however, have treated the time element as constant and heat-treatments used have been for relatively short times. Aside from the early work by Carpenter and Elam,1 the few that have investigated the effect of time on the processes have usually done so for fairly short time periods. During recent years the growing interest in long-time creep properties of metals and alloys under stress has made increasingly important a better knowledge of the recrystallization during prolonged heating. The recrystallization temperature of 70-30 brass given by Clark and White2 in 1932 was somewhat above 400°F. (204°C.) but under 500° (260°C.), whereas in our laboratory recrystallization has been observed in creep specimens at 204°C, the lowest temperature of Clark and White's range. Since the creep properties are quite different above and below the recrystallization temperature, erroneous conclusions can readily be drawn by the application of short-time recrystallization data to creep problems. It was thus considered of both practical and theoretical value to make long-time annealing studies near the minimum recrystallization temperature. In this way useful additions could be made to data on recrystallization temperatures and, since the reactions in this range are relatively slow, additional insight could be obtained into the factors involved in annealing. Several comprehensive reviews of recrystallization processes have been written,3-5 therefore only a brief review of the generally accepted facts will be given here.

Jan 1, 1940

By I. H. Gundiler

Sandia National Laboratories (SNL) is tasked to support The Department of Energy in the dismantlement and disposal of SNL designed weapon components. These components are sealed in a potting compound, and contain heavy metals, explosive, radioactive, and toxic materials. SNL developed a process to identify and remove the hazardous sub-components utilizing real-time radiography and abrasive water-jet cutting. The components were then crushed, granulated, screened, and separated into an aluminum and a precious-and-base-metals fraction using air-tables. Plastics were further cleaned for disposal as non-hazardous waste. New Mexico Bureau of Mines & Mineral Resources assisted SNL in investigation of size- reduction and separation technologies.

Jan 1, 1995

By J. Hanna, J. Jung, I. J. Anazia

Electrothermal production of elemental phosphorous (P4) generates substantial amounts of highly toxic phossy water and sludges. Because of their high phosphorous contents and lack of reliable processing technology, large tonnages of these hazardous wastes have accumulated from current and past operations. To date, the sludges are stored in ponds or above ground in special containment vessels at various locations around the country. Two samples of electric furnace phosphorous sludge (obtained from the Tennessee Valley Authority (TVA) in Muscle Shoals, AL and FMC Corporation in Pocatello, ID) were investigated using physical separation techniques to recover the elemental phosphorous and to render the residual material nonhazardous. The techniques tested include sizing, froth flotation and dispersed air oxidation. Flotation and sizing produced concentrates containing 69% - 90%P4, with recovery in the range of 60% - 87%. Dispersed air oxidation of the fines and tailings products was effective in the removal of an additional 10% - 15% of the P4 in the sludge.

Jan 1, 1993

By Ibezim J. Anazia

Electrothermal production of elemental phosphorous (P4) generates substantial amounts of highly toxic phossy water and sludges. Because of their high phosphorous content and lack of reliable processing technology, large tonnages of these hazardous wastes have accumulated from current and past operations. To date, the sludges are stored in ponds or above ground in special containment vessels at various locations around the country. Two samples of electric furnace phosphorous sludge obtained from the Tennessee Valley Authority (TVA) in Muscle Shoals, Alabama and FMC Corporation in Pocatello, Idaho were investigated using physical separation techniques to recover the elemental phosphorous in the sludge and to render the residual material non-hazardous. The techniques tested include sizing, froth flotation and dispersed air oxidation. Flotation and sizing produced concentrates containing 69 -90% P4 with a recovery in the range of 60 -87%. Dispersed air oxidation of the fines and tailing products was effective in removal of an additional 10 -15% of the P4 in the sludge.

Jan 1, 1991

By Takashi Sakaguchi, Akira Nakajima

Some attempts were made to recover and remove heavy metal elements, such as uranium, copper and chromium, from aqueous systems by using several phosphate compounds. The phosphorylated derivatives of polysaccharides, chitin phosphate, chitosan phosphate and cellulose phosphate, have high abilities to accumulate heavy metals, such as uranium, copper, manganese, cobalt, cadmium, zinc, nickel and chromium, compared with non-phosphorylated polysaccharides. In order to obtain basic information on the recovery and removal of uranium that may be present in industrial effluents, mine waste water and seawater, the adsorption of uranium by chitin phosphate and chitosan phosphate was investigated in details. The adsorption of uranium by chitin phosphate and chitosan phosphate was much greater than copper, cadmium, manganese, zinc, cobalt, nickel, magnesium and calcium. The adsorption of uranium was very rapid and was affected by pH of the solution, temperature. granule radius and co-existence of carbonate ion. The amounts of uranium adsorbed on the adsorbents increased linearly as the external uranium concentration increased. Uranium adsorbed on chitin phosphate easily desorbed with diluted sodium carbonate solution. On the other hand, uranyl and cobalt ions were separated from each other by using chitin phosphate. Along with these fundamental research, some attempts were made to recover uranium from seawater.

Jan 1, 1993