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About David

Since 1993, when he obtained his Mining Engineering Degree from Queen’s University, David has acquired experience in operating roles including many years in post-commissioning operations troubleshooting. Mineral Processing and Metallurgy has become a core strength and passion for Mr. Michaud. Learn more at https://www.911metallurgist.com/about-us/

Acid Dissolution of Metal & Mineral Samples by Microwave

Objective

Reduce the time, complexity and expense of dissolving metal and mineral samples in solution in preparation for chemical analysis.

Approach

In earlier research, the Bureau of Mines developed a rapid and inexpensive method for the dissolution of mineral and metal samples in plastic pressure bottles heated in a boiling water bath. Using this technique, samples could be prepared for chemical analysis in less than one hour compared with several hours by traditional dissolution methods (see Technology News No. 85, December 1980 for further details). By heating in a microwave oven, sample dissolution time can be reduced to approximately 5 minutes.

microwave acid dissolution

An inexpensive microwave oven provides extremely precise and efficient heating of the sample and acid mixture. Increased temperature and pressure in the sealed bottles accelerate sample dissolution.

The Improvements

Samples are prepared as previously described by grinding them to minus 100- mesh and placing a small weighed portion of each into polycarbonate bottles. A mixture of hydrochloric, nitric, and hydrofluoric acids is added to each bottle. The bottle caps then are screwed on tightly to prevent contamination and to retain volatile gases which could be released during the dissolution

Ferric Chloride Leaching

Primary lead is commercially produced from lead sulfide concentrates by a smelting process consisting of sintering, blast furnace reduction, and refining. The pyrometallurgical method is low cost and requires relatively little energy, but generates gaseous sulfur dioxide and particulate lead, which must be controlled to prevent air pollution. Because of the difficulties in meeting regulations for lead exposure, there is considerable interest in developing an alternative to the sintering-reduction-refining process.

As a part of its effort to develop improved technology for recovering metals from domestic ores while minimizing un-desirable environmental impacts and workplace health hazards, the Bureau of Mines has investigated a leaching-electrolysis method for the production of lead. The method consists of leaching galena concentrate with ferric chloride-sodium chloride solution,

ferric-chloride-leaching-equation

cooling the solution to crystallize PbCl2, electrolyzing the lead chloride in a molten-salt bath to produce lead metal and chlorine

ferric-chloride-leaching-equation-2

and using the chlorine to regenerate ferric chloride in the leaching solution,

2FeCl2 + Cl2 → 2FeCl2.

Ferric chloride leaching of galena was investigated by Christiansen in 1923, later by Agracheva and recently by Cottam, Baker, Milner , and Demarthe. Molten-salt electrolysis of lead chloride was reported by

Low Solubility Mineral Flotation

The objective of this study is to evaluate methods to improve the selectivity in flotation of the slightly soluble minerals, typified by calcite, fluorlte and scheelite. The separation of minerals within this class has long been one of the most difficult tasks facing the mineral processing engineer.

The slightly soluble mineral class, as defined herein, have solubility product constants, of very approximately, ksp 10 -10. Typical examples of minerals in the slightly soluble class include the following:

selective-flotation-soluble-minerals

These may be concentrated from ores for their metal content or for use as an industrial mineral, but, just as importantly, they also commonly occur as accessory minerals in ore deposits. Either their recovery (i.e., flotation of trace amounts of malachite from a copper ore containing primarily sulfides) or their rejection (i.e., rejection of calcite during scheelite flotation from a skarn type of ore deposit) will affect the grade, recovery and profitability of an ore deposit.

Only a few separations of the slightly soluble minerals are made commercially (e.g., fluorite-calcite, bastnasite-barite, fluorite-barite). Usually, separation of minerals of this class meets with indifferent results; yet the minerals often occur together.

An important domestic resource beneficiation problem is the selective flotation

Vanadium & Uranium Extraction

Addition of vanadium to iron and steel gives improved product properties such as increased strength, improved machinability, reduced distortion, simpler heat treatment, better weldability, increased wear resistance, better control and uniformity of hardness penetration and gradient, smoother and better finishes, and reduced flaking or spalling of carburized surfaces. Consequently, vanadium-steel alloys are used in the manufacture of products such as tool steels, structural members, mining equipment, airframes, and heads and cylinder linings of large diesel engines.

The United States had a vanadium net import reliance of 28 pct of apparent consumption during 1980. Of the total import supply, 58 pct is obtained from South Africa, 16 pct from Chile, 7 pct from Canada, and the remaining 19 pct from other nations. Because of its importance in manufacturing steel alloys and because of partial dependence on imports for adequate supplies, vanadium is listed as a strategic and critical mineral.

Domestic production of vanadium oxide during 1980 was estimated at 5,506 short tons. Over half of this material was produced from carnotite resources in the Colorado Plateau area. Typical flowsheets for this recovery have been reported by Merritt. The remaining vanadium oxide was produced from the Union Carbide vanadium mine at Wilson Springs, Ark.,

What is the Effects of Impurities in Electrolytes on Electrowinning of Lead from Lead Chloride

Lead is one of the oldest metals known to man and has been used for hundreds of years. The method for producing lead from galena has changed very little. A lead concentrate is mixed with fluxing agents, roasted to remove sulfur, and heated to about 1,000° C with carbon to obtain an impure metallic product, which is refined. The smelting process is a low-cost operation but results in SO2 and lead emissions.

The Bureau of Mines under a cost-sharing program with St. Joe Minerals Corp., ASARCO, COMINCO, Ltd., and AMAX has investigated an alternative method for producing lead. The method consists of leaching galena concentrate with a ferric chloride-sodium chloride solution to make lead chloride. The lead chloride is electrolyzed in a molten-salt bath to produce lead metal and chlorine. The chlorine is used to regenerate ferric chloride in the leaching solution. The reactions involved are:

electrowinning-of-lead-equation

The low melting point (327° C), of lead, its high electrochemical equivalent, and the availability of stable low- melting electrolytes make the development of a molten-salt electrolytic process possible. Lead chloride is a favorable starting material because it is not hygroscopic and has good electrical conductivity when molten.

Electrolytic Method for Recycling Scrap Batteries

Objective

To devise an economical, environmentally acceptable method for recycling scrap lead-acid batteries.

Approach

A combination electrorefining-electrowinning method for recycling lead metal and sludge from scrap batteries was devised which produces a 99.99 + percent pure lead product and eliminates the lead and sulfur oxide emissions that are the normal by products of high-temperature smelting processes.

How the Method Works

Lead metal grids and lugs are separated from the battery sludge by washing and screening, and are melted and cast into anodes for electrorefining by the Betts process. The electrolyte used is fluo-silicic acid, a large volume waste product generated during the production of phosphate fertilizer. During the electrorefining process, impurities in the anode are trapped and held in an adherent slime blanket on the surface as the anode dissolves while pure metallic lead is deposited on a lead cathode.

The major problem in the past has been to recover the lead from the battery sludge which consists of approximately 60 percent lead sulfate, 21 percent lead, and 19 percent lead dioxide. In the flow sheet developed by the Bureau

scrap batteries flow chart

of Mines, the sludge is treated in a two-step leaching

Effect of Potassium Ethylxanthate Degradation

The efficiency of many mineral separation processes, particularly froth flotation, often depends on the type of process water employed. New water suitable for processing is limited in the Western United States; consequently, process waste water is recycled whenever possible. Recycled water from sulfide mineral flotation contains residual flotation reagents, such as xanthate collectors, and chemicals produced by degradation of these reagents. The presence of these degradation products in recycled water interferes with mineral recovery.

A portion of Bureau of Mines research programs on environmental technology involves process waste control. Therefore, an investigation was performed to determine effects of degradation products on sulfide mineral flotation separation and whether the degradation products should be removed from recycled water.

A review of literature indicated that the overall decomposition of the common collector potassium ethylxanthate, (KEX) yields ethanol and carbon disulfide. However, these are not the only products of KEX decomposition experimental evidence revealed that side reactions may occur to produce products such as potassium trithiocarbonate (KTTC). Klauditz first reported the formation of KTTC by the hydrolysis of KEX in alkaline solutions. The reaction may be represented by the general equation

6 ROCS2K + 3H2O ↔ 6 ROH + 2K2CS3 + K2CO3 + 3CS2……………………………………….(1)

where R

Dewatering Talc Slurry

Talc, a hydrated magnesium silicate, is a major constituent of soapstone, which is used in the manufacture of thermal and electrical insulators. Talc also finds applications as filler for use in the paper rubber, and textile industries, in the preparation of soap, cosmetics, lubricating and special polishing agents, as well as in the paint and ceramic industries. Domestic production of talc in 1980 was well over 1.4 million tons. In processing talc, ultrafine waste materials, which respond poorly to conventional separation and dewatering techniques, are often produced. The waste materials usually are impounded in a series of disposal ponds, but even after flowing through as many as nine ponds, the water is still too turbid for reuse or discharge into streams. The Bureau of Mines investigated a method of flocculation and dewatering that allows for disposal of the solid talc waste in land-fills and reuse of the water.

The dewatering technique was initially developed by the Bureau for treating phosphatic clay wastes produced during the mining and beneficiation of phosphate in Florida. It consists of mixing the clay wastes with a flocculant and dewatering the resulting agglomerated mass, first on a static screen to remove most of the water, and then

How to Control Acid Mine Drainage with Surfactants

Objective

Reduce or prevent acid mine drainage from coal refuse piles and surface mines by inhibiting the growth of acid- causing bacteria.

Approach

A dilute surfactant or detergent solution is applied directly to coal refuse piles or overburden using a hydroseeder or road watering truck. The surfactant treatment can be used either as a preventive measure to avoid a potential acid drainage problem or to reduce water treatment costs by controlling acid drainage at its source.

How It Works

Acid drainage is prevented or reduced by inhibiting the growth of Thiobacillus ferrooxidans, a type of bacteria which obtains most of the energy it needs to survive by oxidizing ferrous iron in water, The oxidized iron in turn attacks pyrite, which forms an acid and additional ferrous iron for the bacteria to oxidize. T. ferrooxidans is protected by an outer membrane which enables it to survive in its acid environment. Anionic surfactants, or surfactants containing negatively charged ions, can be used to destroy this membrane, thus killing the bacteria and slowing down the oxidation of acid-forming pyrite.

Of the anionic surfactants tested to date, sodium lauryl sulfate (SLS) appears to be the most effective as a bactericide. Alpha olefin sulfonate and

Concrete Crib Design

This research is a part of an ongoing effort by the Bureau of Mines to improve health and safety in coal mining as directed by the Federal Mine Safety and Health Act of 1969 and amendments of 1977. The concrete crib design and field testing project has evolved from laboratory research to a verification and demonstration phase for technology transfer to industry. Cooperative underground demonstrations are either in progress or completed in seven different coal mines and one trona mine. Demonstrations involved three different steel-fiber-reinforced concrete (SFC) support member designs. These will be referred to as designs 1, 2, and 3.

A successful installation of design 1 SFC cribs at Kaiser’s Sunnyside Mine No. 1 at Sunnyside, Utah, was made in 1976 and monitored through 1979. It was a test section in the Bureau’s single-entry longwall (LW) demonstration. The wood cribs used to support the combined gate, or dual-gate, single entry were not stiff enough to hold the tailgate portion open in a satisfactory manner after the passage of the first longwall face, but the SFC crib test section supported the entry satisfactorily. Design 1 members contained steel rebar that was eliminated in later designs. This report covers field testing of

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