Waste tailings

The relative area of mine solid waste tails (per 100,000 M3 of rock mass) is 0.7-0.8 of the total area. On average, the disturbed areas of uranium ore exploration site are partitioned as follows 32.3% of disturbed land is occupied by dumps, 27.2%, by pits, 20.3%, by industrial areas, 13.3%, by tails, and about 10%, by other types of land disturbance. 

Fig. 3. The beneficiation of taconite ore on Ihe iron range requires large volumes of water in concenlrating by magnetic separation. To eliminate massive waste-disposal problems, huge thickeners, such as the 300-foot (91,5-meter) diameter caisson unit shown here, are used. This system will handle over 70 million gallons (265 million liters) per day or 50,000 gallons (189,250 liters) per minute of liquid and 250 tons per day of suspended solids. Clarifying the waste tailing stream permits reclamation of water on a large scale for plant reuse...

Although the details are beyond the scope of this book, health problems can be caused by solids and liquids suspended in water (for example, in waste-tailings streams) or in air (for example, in stack-emission plumes). Specific potential hazards have been associated with a diverse spectrum of colloidal materials, including synthetic chemicals, coals, minerals, metals, pharmaceuticals, plastics, and wood pulp. Limits for human exposure for many particulate, hazardous materials are published [504,505],... 

In many surface-separation processes, there will occur three distinct phases or process streams a product stream (either oil or water), a waste (tailings) stream, and an interface or rag layer emulsion stream, which may contain emulsified oil and/ or water. The interface emulsion can be the most troublesome, in terms of process operation, and the most complex and intractable, in terms of treatment. Mikula shows (Figure 1 in Ref. [66]) a photomicrograph of a quite stable interface emulsion (rag-layer emulsion) in which one can clearly observe the simultaneous occurrences of both O/W and W/O emulsions in different regions of the same sample. 

A primary human health concern associated with mine wastes, tailings, and smelting byproducts produced during the extraction of metals from metallic mineral deposits has been the incidental ingestion exposure, and resulting heavy metal uptake, especially for small children who play on waste piles, tailings, slag heaps, or... 

Mine wastes, tailings, and smelter slag and emissions can contain complex mixtures of minerals that are typically a predictable function of the geologic characteristics of the deposit type being mined, coupled with the ambient climate/ environmental characteristics and the mining or mineral processing method used. See Chapter 9.05 and Plumlee (1999) for a detailed discussion. 

Soils that have been contaminated by mine wastes, tailings, smelter slags, or smelter particulates can contain a complex mixture of minerals present in the soils prior to contamination minerals contributed by the contaminants minerals formed by soil weathering, biological reactions, and chemical reactions with infiltrating waters and soil moisture windblown dust, and other anthropogenic materials (Ruby et al, 1999). For example, reactions of lead oxide with soil moisture in alkaline soils can precipitate lead carbonate, whereas reactions in acidic soils can precipitate lead sulfate. 

Hence, mine wastes, tailings, and smelting byproducts can contain a wide variety of minerals, including minerals that are bioreactive (such as acid-generating sulfides and evaporative sulfate salts), minerals that contain potentially bioaccessible heavy metals and metalloids (lead, cadmium, arsenic, mercury, zinc, copper, nickel, uranium, molybdenum, antimony, etc.), and minerals that are biodurable (such as quartz and, in some deposit types, asbestiform silicates). 

Usually base and precious metal sulfide deposits also have important amounts of pyrite. The pyrite in hydrothermal ore deposits is most often coarse grained and relatively unreactive. Mining and milling the rock to fine particle sizes for the purpose of metal extraction, vastly increases pyrite surface area and exposes the pyrite in waste-tailings piles to oxidation and weathering. Serious AMD releases can result. 

High aluminum (and silica) concentrations in acid streams and in sulfidic-waste tailings and coal-storage piles derive from the weathering of aluminosilicate minerals. Kaolinite clay, for example, is common in the underclays beneath Pennsylvania coal beds (Gang and Langmuir 1974). Above... 

Desulfurization is an alternative process for managing large-scale sulfide wastes/ tailings. This process can separate sulfide minerals into a low-volume stream, leaving mainly waste with low sulfur content that will be non-acid-generating. The attractiveness of desulfurization is that it is simple and economic. 

In the absence of cost-effective sortation/reclamation technologies, pyrolytic processes are potentially applicable to commingled streams containing mostly hydrocarbon polymers. Therefore, in principle, pyrolytic processes may be applicable to Municipal Solid Waste tailings , automotive shredder residue fluff, and perhaps mixed textiles. However, the limitations imposed by PVC contamination and other impurities will significantly limit the applicability of a specific process or require an additional pretreatment step. 

Theoretically, optimum block length is a compromise between two types of considerations [6, 9, 10]. (1) Short molecules should migrate more easily and completely to the interface, and should saturate the interface efficiently without long wasteful tails, and thus contribute more efficiently to decreasing interfacial... 

Pb/Zn mining <500mgkg CdS (with ZnS) rock waste, tailings, soils... 

Mining of Cr <50% PbCr04, FeCr204 rock waste, tailings... 

Mining Pb, Zn etc. <15% <5000 mg kg" PbS, PbS04, PbCOj rock waste, tailings soils... 

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