A Review of Bismuth(III)-Based Materials for Remediation of Contaminated Sites

Bismuth(III)-based materials are uniquely suited for in situ subsurface remedy applications, as they offer many beneficial properties, including high affinity for multiple contaminants, low human and environmental toxicity, low cost, and synthetic availability. This review summarizes the current research trends in targeted development of bismuth materials potentially useful for subsurface remedy applications, with an emphasis on recent advances in understanding of relevant structure–property relationships. While various bismuth mineral phases can provide frameworks for contaminant sequestration, layered crystalline arrangements are particularly promising because of their electronic and spatial flexibility and their ability to accommodate a wide range of negatively charged species. This translates into a high uptake capacity for several recalcitrant colocated contaminants found at legacy nuclear processing sites, including technetium-99, iodine-129, hexavalent chromium (chromate), and uranium, and offers the potential for both in situ and ex situ remediation applications. Layered bismuth minerals are found in nature, and knowledge of their structure informs the targeted design and cost-effective synthesis of the structurally preorganized materials from readily available bismuth sources for remedial applications in soil and groundwater. This comprehensive review highlights the structure, synthesis, and environmental chemistry of Bi-based materials, including the interaction between Bi-based materials and key environmental contaminants, to explore their potential use for remediation. Bismuth oxyhydroxides, containing clusters of [Bi6O4(OH)4]6+ and [Bi6O5(OH)3]5+ surrounded by easily exchangeable anions such as nitrate, are versatile and show the greatest potential for environmental remediation applications. Because of their flexible structural arrangement, they have been shown to sequester electronically and sterically different anionic species, including chromate, pertechnetate, iodate, and uranyl carbonate, even when they are present as comingled contaminants in groundwater and pore water containing other competing anions (e.g., nitrate and carbonate) and in contact with subsurface sediments.