Task 2— Metal and Mineral Commodities in Waste Streams

Metal and mineral commodities play an important role in modern society and are linked to industrial development. As a part of the life cycle of mineral- and energy-resource development, metal and mineral commodities discarded after use or generated during extraction and processing become part of waste streams—which is the traceable flow/transport of solid or liquid wastes from point of generation to final disposal. Recovery and reuse of metals from waste streams can decrease U.S. reliance on primary resources and lessen unwanted dispersion of metals in the environment, while reducing disposal costs and regulatory liabilities for generators of waste streams. Recovery of potentially valuable commodities, such as Au, Ag, Pt, and Pd, and newly emerging technologically important (critical) elements (e.g., REE, Be, Co, Ga, Ge, In, Li, Mg, Mn, Nb, Re, Se, Ag, Ta, Te, Th, W, and V), can provide new sources for these commodities and offset disposal costs of waste streams. Examples of waste streams of interest include slag, sludge, drainage and waste from mining, compost facilities, landfills, and various industrial and municipal waste streams. The Waste Streams Task coordinates with the Built Environment Task, especially in cases where the topics converge, such as for discarded infrastructure materials.

The objectives of this task are (1) to determine the elemental composition of various waste-stream materials, and (2) to investigate the metal-recovery potential of valuable and critical commodities present in diverse waste streams (including mine waters, historical mining wastes, smelter slag, biosolids, and medical and hospital wastes). This task provides a reconnaissance study of the existence and characteristics of mineral and metal commodities present in various types of waste streams. This task supports the Mineral Resources Program goal of understanding the life cycles of various mineral or metal commodities.

Approach

An initial literature review has been performed to compile existing data on metals and minerals present in various types of mining, industrial, and domestic waste streams. Samples from a variety of waste streams (including mine waters, historical mining wastes, smelter slag, and biosolids) have been acquired and are being analyzed and characterized to examine the abundance, form, texture, and speciation of metals and minerals, and to assess the presence of potentially valuable and critical commodities. Chemical and mineralogical characterization techniques include ICP-MS, INAA, EDXRF, XRD, petrographic studies, SEM/microprobe, QEMSCAN, Raman, and X-ray absorption spectroscopy (XAS). Extractions are being performed on selected samples using proxies of extractants used by the mining industry and simulated human body fluids. Collaborations with academia, industry, and various local and state jurisdictions have been established to pursue extraction of potentially valuable and critical commodities from waste streams.

The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. government.