From contaminant to commodity: a critical review of selenium usage, treatment, and recovery

Selenium, the essential toxin, is an indispensable nutrient for many organisms but quickly becomes a significant environmental concern at slightly higher concentrations, particularly in aquatic environments. Water treatment technologies have been developed over decades for industrial Se removal, but invariably result in Se-laden residuals. These Se-laden residuals represent a significant environmental liability and require careful management, which in turn represents a real, but often overlooked, operating cost. Conversely, Se sees commercial use across many industries and may be considered a vulnerable element in that its economic importance far outweighs its global supply chain stability. Thus, the recovery of Se from non-conventional sources, including solid (electronic waste) and water-based sources (mine tailings, leachates, flue gas desulphurization water, agricultural waste) is desirable. Industrial wastewater represents a unique opportunity to pair wastewater treatment techniques with resource recovery towards circular economy principles. This review highlights conventional and emerging uses of Se, along with an overview of its current supply, and potential sources. Next, a summary of existing and emerging wastewater treatment technologies for Se removal from industrial wastewater streams is provided. Finally, this review also includes progress and developments towards Se recovery from the same industrial wastewater streams, with a focus on integrating Se wastewater treatment and Se recovery towards a circular economy.

Graphical abstract