Elsevier

Waste Management Series

Volume 7, 2006, Pages 375-457
Waste Management Series

Chapter 10 - Resource Recovery from Process Wastes

https://doi.org/10.1016/S0713-2743(06)80095-4Get rights and content

Introduction

The extraction of valuable metals or minerals from ores, the processing of concentrates resulting from beneficiation of these ores by pyrometallurgical and /or hydrometallurgieal means and the commercial use of the extracted metals or minerals results in a wide variety of by-products. Some of these by-products contain residual metals or minerals of commercial value and may be reprocessed for the recovery of these additional and often different metals or minerals. Thus historically gold tailings produced in gravity plants may be reprocessed by cyanidation to recover fine residual gold values, tin may be recovered from zinc tailings, vanadium from tar sand tailings, uranium from gold tailings, pyrrhotite from nickel tailings, magnesium from asbestos tailings, as examples. Similarly metal values may be recovered from aqueous effluents by liming spent plating solutions or by hydrogen sulphide precipitation from acid mine drainage and occluded metals or minerals recovered from smelter or foundry slags. Finally a wide range of by-products, in the form of dusts, grindings, turnings, chips, spills, splatters and sprues result from the fabrication of metals

Many efforts are under way to minimize or reduce the volume of tailings generated and make the process more efficient. Some examples were described in Chapter 9. They have met with some success, but they will not solve the problem of the huge volume of accumulated tailings, effluent and sludge all of which are potential environmental hazards.

Treatment and disposal of mineral process tailings and metallurgical effluents and environmental standards to be met are described in a number of monographs and reviews. (Ritcey, 1992; Chalkley et al., 1989; Aplin and Argall, 1973). That subject will not come in the scope of this chapter. The principal focus will be on recycling and resource recovery from tailings. It should, however, be noted (as will be explained in the chapter) that recycling of resources from the accumulated wastes has positive environmental impact, for minimizing health hazards due to toxic elements as well as for sustainable development. Therefore, both for economic as well as environmental reasons, resource recovery from process wastes is attracting serious attention in recent years.

Such resource recovery is important from two perspectives. First there is the value of the product recovered. It may be less than me cost of extracting the same metals and minerals from primary ores since the mining and milling costs have already been paid. Second is the resultant upgrading of the bulk material which may permit its use where previously concern with potential metal or mineral solubility or radioactive properties may have inhibited such application. The use of this bulk material is addressed in Chapter 9 although to the extent that the bulk material such as mill tailings contains a substantial proportion of minerals such as calcite, dolomite, quartz, felspar, chlorite, pyrite, or magnetite that are liberated such tailings are also a potential candidate for resource recovery. One example is the sludge generated in Canadian nickel mineral processing industry. It contains up to 6 percent nickel on dry basis in addition to iron and magnesium. The accumulated sludge could be a secondary source of nickel. Technically feasible and economically viable methods of recovery are greatly desired.

A second example is that of acid rock drainage (ARD), also referred to as acid mine drainage (AMD). It is generated by the oxidation of pyrite, which is the principal waste sulfide mineral occurring in sulfide mineral process tailings. The oxidation of pyrite produces sulfuric acid, which leaches into solution other metals occurring in the tailings. Many ARD systems are known to contain copper and zinc in significant concentrations, as much as 30 g/L zinc, and other metals like manganese and magnesium in lower concentrations.

This chapter discusses and provides examples of present or potential recovery of resources from the by-products of mining and processing of ores and concentrates, extraction, refining and fabrication of metals, plus the utilization of industrial minerals.

The chapter will describe some case studies of resource recovery from process wastes generated in different forms in diverse areas of mineral and metallurgical industry. They include mineral process tailings, metallurgical effluents, slimes and sludges produced in the tailing treatment processes, and solid wastes. Two sections are also devoted to survey the recycling of resources from exhaust batteries and spent catalysts. In addition to resource recovery, some of the wastes have been converted to useful byproducts, which will also be discussed.

Section snippets

Mineral Process Tailings

Almost all mineral processing operations, except those few, where the raw material (ore) to be processed is of high grade, generate huge quantities of tailings, which include those minerals, which are not usually of economical value in the operation. Such ‘waste minerals’ include silica, calcite and dolomite, silicate minerals and in the case of sulfide ores pyrite (FeS2) and pyrrhotite (FeS). The common practice has been one of storing them in tailing ponds and recycling most of the water. The

Metallurgical Effluents and Residues

Metal processing industry is the second principal source of ‘waste’. This occurs in the form of effluents and residues, which are a source of environmental hazard as they often contain toxic metals and cannot be disposed off without appropriate treatment Any liquid discharged into the environment must meet environmental regulations, which specify upper limit of each metal in the discharge liquid. Appropriate treatment techniques are required both to meet environmental regulations as well as to

Recovery of Metal Concentrates from Waste Sludges

The sludge produced by lime treatment of industrial effluents often contains many impurities associated with the cupric hydroxide. Several treatment steps are required to obtain the desired purity copper hydroxide concentrate. In a process described by Jandova and coworkers (2000), the sludge is first leached in dilute sulfuric acid at pH 0.9–1.0. This dissolves the cupric hydroxide along with several other metal oxides. The acid leach residues are separated by a solid liquid separation step.

Solid Wastes

Some of the metallurgical operations do not use water. The material is processed as dry solids in granular or powder form. The ‘waste’ generated in such operations occur are treated by techniques used for processing dry material.

Resource Recovery from Discarded Batteries

Besides lead batteries, which are a principal secondary source of lead, described in Chapter 5, there are a large variety of domestic batteries, in a range of composition. Various metals, including cobalt, nickel, cadmium, lithium are principal metallic components in batteries used in domestic appliances and industrial equipment. Discarded batteries, which would otherwise be a serious environmental liability, both by the solid waste generated as well as by the toxicity of the metals contained

Resource Recovery from Spent Petroleum Catalysts

Petroleum refining industry generates spent catalysts as a waste product, which contains several metals. A typical composition represents Al (15–25%), Mo (3–10%), Ni (0.2–3.0%), V (4–8%), Co (up to 3%) besides Si (1–5%), S (5–10%) and oil (10–20%) (Cmojevich et al., 1990). The resource recovery scheme is based on a two stage leach, one for a selective solubilization of molybdenum and vanadium, and the other for selective solubilization of aluminum. It converts the spent catalyst components into

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