10.0 Introduction

The extraction of valuable metals or minerals from ores, the processing of concentrates resulting from beneficiation of these ores by pyrometallurgical and /or hydrometallurgical 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...