|Mine drainage from coal and metal mining affects thousands of stream miles and thousands of acres of impoundments in the US, and waterways in other countries are also severely affected. Few aquatic organisms survive in mine drainage due to either low pH and high metal concentrations or coating of bottom substrates by iron hydroxides. Some of these sediments can be used as a pigment raw material or for other iron needs. Utilization can help pay for remediation of abandoned mine sites and reduce the need to mine pigments from soil.|
Currently, mine drainage sediments either choke out life in affected streams and lakes or sediments from treatment facilities present a waste disposal problem. Can these sediments be utilized as a resource in order to help pay for remediation?
Kirby et al. (1999) examined the bulk composition of acid mine drainage sediments and its relationship to color. It is known that the treatment process affects the sludge composition and color. Numerous suggestions for utilizing materials from mine drainage have been made, but only recently has work has been done to determine if raw materials can be recovered. One exception carried through to the production stage is the recovery of common salts from mine drainage in Europe. Hedin Environmental has demonstrated that selected mine drainage sediment from net alkaline discharges can be utilized as a pigment on an industrial scale..
Yellow-orange-red iron hydroxides (much like rust) are a predominant component of natural and treated mine drainage sediments. Similar ferric oxides and hydroxides have historically been used and are still being used as natural red, yellow, and brown pigments. These raw materials are mined from soil horizons, disturbing the regions where the mining occurs.
These iron hydroxides are al high quality resource for the pigment industry, as the concentration of iron in the precipitates is often high compared to iron mined from soils and weathered rock. The utilization of ferric hydroxide precipitates from acid mine drainage can providing an economic incentive for private industry to remediate acid mine drainage and make a profit or help pay for remediation by collecting a currently unused resource.
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