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

Bismuth(III)-based materials are uniquely suited for in situsubsurface remedy applications, as they offer many beneficial properties,including high affinity for multiple contaminants, low human andenvironmental toxicity, low cost, and synthetic availability. This reviewsummarizes the current research trends in targeted development of bismuthmaterials potentially useful for subsurface remedy applications, with anemphasis on recent advances in understanding of relevant structure-property relationships. While various bismuth mineral phases can provideframeworks for contaminant sequestration, layered crystalline arrangementsare particularly promising because of their electronic and spatialflexibilityand their ability to accommodate a wide range of negatively charged species.This translates into a high uptake capacity for several recalcitrant colocatedcontaminants found at legacy nuclear processing sites, including technetium-99, iodine-129, hexavalent chromium (chromate), and uranium, and offersthe potential for both in situ and ex situ remediation applications. Layered bismuth minerals are found in nature, and knowledge oftheir structure informs the targeted design and cost-effective synthesis of the structurally preorganized materials from readilyavailable 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 keyenvironmental 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 greatestpotential for environmental remediation applications. Because of theirflexible structural arrangement, they have been shown tosequester electronically and sterically different anionic species, including chromate, pertechnetate, iodate, and uranyl carbonate, evenwhen they are present as comingled contaminants in groundwater and pore water containing other competing anions (e.g., nitrateand carbonate) and in contact with subsurface sediments.