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

CuSO4 Copper Sulfate Crystallization

CuSO4 Crystallization for Typically Acidic Extraction: A small body of acid-leachable copper ore or a small existing stream of copper-bearing acidic mine water is often unable to justify a plant to produce cathode copper. Electrowinning is capital intensive, and small reserves are generally considered higher risks for financing. Electrowinning is also intensive in electric power and labor, both of which are in short supply to

sx-crystallization for typically acidic extraction

small operations in remote locations. The market for cathode is a large one, and small quantities may not bring the full market price. Many operators stay with the cementation process for these reasons, paying high prices for iron and getting low prices for cement copper, despite the feasibility and attractiveness of SX on a small scale.

Production of copper sulfate as an end product is an alternative. SX strip liquor is a good feed to crystallization, which may be accomplished in simple vats. Figure 3 and Table III describe this possibility. The flowsheet basis is 24 tons per day of copper sulfate pentahydrate. The SX stripping solution and strip liquor are appropriate for LIX 64N, or a somewhat stronger (more acidic) extractant if required.

By | 2017-06-20T09:12:12+00:00 June 18th, 2017|Categories: Electrometallurgy|Comments Off on CuSO4 Copper Sulfate Crystallization

Waste Mine Tailings Characterisation 

Any critical evaluation of the potential for contamination of groundwater by leachates from mining wastes must include consideration of the waste quantities and locations, the physical and chemical characteristics of the waste, and the waste disposal practices. The primary types of solid wastes generated by mining activities include overburden and waste rock from surface mining, waste rock from underground mining, bulk tailings from the milling of metal ores and non-metal minerals, and refuse from coal preparation-plant processes.

In the United States, more than 65 commodities, including coal, metal ores, and non-metal minerals, are presently mined.

In the remainder of this section, the amounts of wastes generated during the past 20 years are quantified on a regional and mineralogical that is, commodity) basis. Then, the character of these wastes is presented to describe the amounts of acid-forming or toxic-product-forming components they contain, finally, the waste disposal practices commonly employed in the mining industry are reviewed, with emphasis on the extent to which these practices favor or inhibit the formation of an acid or toxic leachate.

Quantities of Wastes Generated

Bases for Estimates

Waste-quantity estimates presented in this report were either taken directly from or estimated on the basis of data and information published in the Bureau

By | 2017-06-16T15:24:04+00:00 June 16th, 2017|Categories: Environment & Tailings|Comments Off on Waste Mine Tailings Characterisation 

Mine Tailings Disposal Methods

As discussed previously, the primary types of solid wastes generated by the mining industry are overburden and waste rock from surface mining, waste rock from underground mining, bulk tailings from metal-ore and non-metal mineral beneficiation and milling processes and refuse from coal preparation-plant processes. The methods commonly employed for disposal of these wastes in each of the industry segments (that is, coal mining and metal-ore and non-metal mineral mining) are described below.

Mining Coal Tailings Disposal

As has been pointed out earlier in this section, immense quantities of wastes are produced by coal mining activities. Many of the regulations governing these wastes have only recently been enacted, and the Surface Mining Control and Reclamation Act of 1977 (PL 9587) will be a major factor influencing coal mining waste management in the future. The discussion of coal mining waste disposal practices which follows is organized by waste type, since the practices commonly employed are a function of this factor.


Overburden from surface coal mines consist of soils, gravels, shales, coaly shales, and other unconsolidated material and, occasionally, some bedrock which overlies the coal seam. Surface mining is conducted by two basic methods: contour strip mining and area mining. Contour strip mines are used in

By | 2017-06-16T15:11:23+00:00 June 16th, 2017|Categories: Environment & Tailings|Comments Off on Mine Tailings Disposal Methods

Shredded Automobile Scrap Recycling

The Bureau of Mines is involved in research directed toward the utilization of municipal solid waste. One of the primary objectives is the recycling of the magnetic fraction of municipal solid waste (raw refuse). This is consistent with one of the Bureau’s goals, which is to minimize the requirements for mineral commodities by maximizing metals recovery from secondary domestic resources.

In this investigation, cupola trials were made using combinations of refuse scrap with shredded automobile scrap under basic and acid slag practices. Furnace operating information and the behavior of alloying and tramp elements was obtained. The research showed that it is possible to utilize up to 60 percent refuse scrap in the cupola under basic practice and 30 percent under acid practice. Aluminum in refuse scrap, present in bimetallic cans, increased the recoveries of silicon and manganese charged to the cupola. Increased use of refuse scrap provided iron of lower sulfur. The alumina resulting from oxidation increased the slag volume. The aluminum and tin contents of the iron increased with increasing levels of refuse scrap in the charge. Lead was not a problem with respect to contamination of the iron, in basic practice, operation of the cupola was satisfactory since

By | 2017-06-16T12:05:30+00:00 June 15th, 2017|Categories: Magnetic|Tags: |Comments Off on Shredded Automobile Scrap Recycling

Hydrothermal Boehmite Precipitation

The currently proposed method for the recovery of alumina from nonbauxitic materials involves acid leaching (Figure 1). Primary emphasis is on kaolin clays. To date, leaching by nitric acid, hydrochloric acid, and sulfurous acid has been considered, and it appears that leaching with hydrochloric acid (25-27%) is the most practical process. The first step in the overall process (Figure 1) is to decompose the hydrated aluminum silicate ore to meta kaolin (silica and acid-soluble alumina) by calcination at 700° to 800°C. This calcined materials is then leached with HCl to extract aluminum as dissolved Al3+. The undissolved solids are separated from the process stream, and the solution is purified of iron by organic solvent extraction. The aluminum content of the fluid is then precipitated as AlCl3·6H2O by evaporation or by sparging the solution with HCl gas. Then the aluminum chloride hexahydrate is decomposed into alumina and HCl by calcining at high temperature. This process releases HCl, which is then recirculated for leaching of fresh ore and for crystallization.

The thermal decomposition of aluminum chloride hexahydrate is energy intensive. Hence, an alternative process in which aluminum hydroxide or oxides are precipitated from the aluminum chloride solution, if realizable, would be a technically

By | 2017-06-15T14:23:11+00:00 June 15th, 2017|Categories: Pyrometallurgy|Tags: |Comments Off on Hydrothermal Boehmite Precipitation

Copper Nickel Flotation

The Bureau of Mines investigated the flotation responses of two copper nickel ore samples from the Duluth Complex with the objective of recovering bulk sulfide concentrates. One of the ores studied was taken from a test pit; the other was taken from a test shaft. The samples were quite similar except that the pit sample analyzed 0.35 pct Cu and 0.11 pct Ni and the shaft sample analyzed 0.69 pct Cu and 0.14 pct Ni. Flotation responses were studied in both laboratory and pilot plant tests.

Pilot plant flotation responses were similar for both samples resulting in grades of 12.2 pct Cu and 2.5 pct Ni for the pit sample and 12.2 pct Cu and 2.1 pct Ni for the shaft sample. Weight recoveries were 2.5 pct for the pit sample and 5.2 pct for the shaft sample. Copper and nickel recoveries for the pit sample were 87 and 62 pct, respectively, and 92 and 73 pct for the shaft sample. Both concentrates contained small but significant values of cobalt and precious metals. Cobalt recoveries were low—less than 40 pct for both concentrates. Precious metals contents of the concentrates were 1.59 oz/ton for the pit sample and 0.99 oz/ton for the

By | 2017-06-15T14:15:49+00:00 June 15th, 2017|Categories: Flotation, Laboratory Procedures|Tags: |Comments Off on Copper Nickel Flotation

Clay Flocculant

Under its mission to effect pollution abatement, the Bureau of Mines began intensified research seeking means for economically disposing of the large amounts of Florida phosphatic clay wastes and reclaiming the mined land. The clays, which are discharged from the processing plants at about 3 to 5 pct solids , have colloidal characteristics and are difficult and slow to dewater by natural settling. The quantity of water retained and stored with them is so great that impoundment in above ground, dammed storage areas is required. Boyle has estimated that one processing plant produced 4 million tons of phosphatic clay wastes per year, and Vasan has estimated that about 2 billion tons of clay wastes are stored behind impoundment dams. The stored suspensions represent a serious potential danger for pollution to the land and aquatic environments of the area because of possible dam failure.

The Bureau of Mines is developing a method for dewatering the suspensions of clay wastes using polythylene oxide (PEO) as a flocculant. Polyethylene oxide can act as a bridge between colloidal particles causing agglomeration that results in rapid separation of clays from water. Once the water is released from the agglomerates, it is removed immediately by mechanical means.

By | 2017-06-13T13:28:10+00:00 June 13th, 2017|Categories: Environment & Tailings, Reagents & Chemicals|Tags: |Comments Off on Clay Flocculant

Cyanide Destruction in Gold Heap Leach

In the past 25 years there has been a wide expansion of the use of cyanide heap leaching by the mining industry. This process allows profitable recovery of gold and silver from low-grade ore. Heap leach pads are constructed on slight drainage grades and lined with an impervious clay and/or geotextile. Ore is stacked and leached in successive lifts or benches on the pad. Sprinkler systems set within and on the surface of the lift to be leached deliver a high pH sodium cyanide solution that, in its percolation through the ore, forms stable complexes with gold, silver, cobalt, iron, copper, nickel, zinc, and cadmium. This pregnant solution is collected as it drains from the pad for precious metal recovery.

After leaching, the heap still contains interstitial and adsorbed cyanide species, including free cyanide and metal-complexed cyanides. The metallo-cyanides are present as weak acid dissociable (WAD) complexes of cadmium, copper, nickel, and zinc, and extremely stable iron and cobalt cyanide complexes (Smith and Mudder 1991). These cyanides have the potential to degrade surface and ground water resources.

The Montana Water Quality Act directs the Montana Department of Health and Environmental Sciences (MDHES) to maintain standards for pollutants. The standards are referenced by

By | 2017-06-13T07:44:19+00:00 June 13th, 2017|Categories: Environment & Tailings, Hydrometallurgy|Comments Off on Cyanide Destruction in Gold Heap Leach

Heap Leaching Agglomeration

We investigated a particle agglomeration technique for improving the flow of leaching solution through heaps of clayey or crushed, low-grade gold-silver ores, wastes, and tailings. This technology has been adopted on a broad scale by the precious-metals-processing industry. This report presents information on five commercial operations that have benefited from agglomeration technology and that represent a cross section of current heap leaching practice. The technology is cost effective because of decreased leach times and improved precious metal recoveries.

Exploration identified numerous low-grade precious metal deposits, mine waste materials, and tailings piles throughout the Western United States. The increase in precious metal prices during this period generated interest in processing these low-grade feed materials by low-cost heap leaching technology. Heap leaching with cyanide was applied to many of the materials; however, many conventional operations were unsuccessful because excessive amounts of clay in the feed or fines generated during crushing prevented a uniform flow of cyanide solution through the heaps.

As part of its research program to improve the recovery of gold and silver from low-grade domestic resources, the Bureau of Mines investigated agglomeration pretreatment to overcome the percolation problems associated with heap leaching. Agglomeration of the clays and fines before heap building permitted

By | 2017-06-13T07:34:59+00:00 June 13th, 2017|Categories: Hydrometallurgy|Tags: |Comments Off on Heap Leaching Agglomeration

Ferrochromium Alloys Manufacturing

As part of its effort to reduce the need for strategic minerals through conservation and to reduce the capital and energy requirements of mineral processing, the Bureau of Mines has investigated a method for preparing ferrochromium alloys containing less than 2 percent carbon. This method will conserve chromium and should reduce the capital and energy requirements for chromite reduction.

Reduced products containing less than 2 wt-pct C and as low as 0.01 wt-pct C were obtained by reacting pellets of chromite and carbonaceous reductant mixtures at pressures of 0.1 to 1 torr and temperatures of 1,230° to 1,320° C. The extent of reduction increased with increased temperature and decreased pressure; however, operating conditions were limited due to the onset of significant chromium vaporization at higher temperatures and lower pressures. Foundry coke, anthracite, and carbon black were found to be superior to graphite as reductants. The reduction of chromite to metallics was found to proceed via the carbide intermediates (Fe,Cr)7C3 and (Fe,Cr)23C6. No evidence of carbide intermediates Fe3C or Cr3C2 was found. Buttons of ferrochrome alloys were made by melting a mixture of reduced products with CaO and SiO2 at 1,700° C for 20 minutes in an induction furnace.

Stainless steel is important

By | 2017-06-12T13:33:27+00:00 June 12th, 2017|Categories: Smelting - Melting - Refining|Tags: |Comments Off on Ferrochromium Alloys Manufacturing