Sources, Forms, Extractability of Metals in Non-Ore Deposit Sources

Science Center Objects

This project explored potential recovery and environmental consequences of metals in mining and mineral processing wastes as a function of ore deposit geology, and in debris from demolished or burned buildings. 

sampling mine drainage

USGS scientist sampling at a historical mine waste pile with associated drainage.

(Public domain.)

Science Issue and Relevance

Many metals that in the past had a limited to modest industrial or technological application are now critical for emerging high-technology or green-technology applications. Increasing demand for these critical metals, coupled with their geologically rare economic enrichments in the earth's crust, has raised concern about their availability. Recovery of these metals from waste materials is increasingly of societal interest, as it may help reduce dependence on foreign sources for the metals, defray costs of waste remediation, reduce the content of metal toxicants in wastes, and diminish needs for mining that specifically targets the metals.

Previous work on the Metal and Mineral Commodities in the Built and Waste Stream Environments—Uses, Characteristics, and Environmental/Health Implications project examined the types, concentrations, and environmental and toxicological characteristics of metal and minerals in a wide range of building materials and other materials found in buildings such as concrete blocks, brick, rebar, concrete, pipes, plastics, electronics, and pressure treated lumber. Results revealed a number of unusual occurrences of metals and minerals.

Methodology to Address Issue

This project explored potential recovery and environmental consequences of metals in mining and mineral processing wastes as a function of ore deposit geology, and in debris from demolished or burned buildings. Our general objectives were to 1) characterize metals in bulk materials; 2) examine the leachability of metals from these materials; 3) examine deportment of metals during smelting or refining, and 4) tie metals in these materials to the life cycle of mineral commodities from extraction, through manufacturing, consumer use, reuse, recycling, and disposition.

  • Metals and Minerals in Debris from the Built Environment - Our primary objectives were to 1) understand the forms, concentrations, and environmental implications of metals in materials that are recycled or sent to landfills when buildings are demolished or have burned, 2) screen previously collected samples by portable X-ray fluorescence, from which selected samples were be sampled for further analysis, and 3) burn site materials were analyzed and compared to lumber of varying age.

  • Sources, Forms, and Extractability of Mining and Mineral Wastes - Our objectives were to 1) obtain additional mining waste samples from a variety of mineral deposits types, 2) conduct bulk chemical and mineralogical characterization of the waste samples, and 3) subject waste samples to leaching tests to determine extractability of elements of interest.

  • Sources, Forms, and Extractability of Metals from Smelter Wastes - We examined deportment of metals during smelting or refining. Our objectives were to 1) conduct bulk chemical and mineral characterization of modern smelter slag, 2) identify amounts and modes of occurrence of residual elements in slag for potential recovery, and 3) quantify deportment of various metals during processing steps of concentrating metals from ore in order to optimize recovery.

microscopic gold and lead particles

Microscopic gold and lead particles surrounded by organic and phosphorus-rich material in a municipal biosolids sample (combined surface topography and atomic weight images).

(Credit: Heather Lowers, USGS. Public domain.)

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