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Amid the global call for decarbonization efforts, uranium and lithium are two important metal resources critical for securing a sustainable energy future. Extraction of uranium and lithium from seawater has gained broad interest in recent years due to the thousand-fold higher quantity available as compared to land-based reserves, but the challenge lies in the ability to extract them at ultralow concentrations. Over the past two decades, the rise of nanotechnology has brought together an abundance of adsorptive materials that are poised to incentivize technologies capable of achieving high extraction performances. The objective of this review is to consolidate recent advances in uranium and lithium extraction from the standpoint of adsorptive materials and technologies for application in seawater. First, adsorptive materials for uranium extraction are reviewed, before we discuss the technology platforms into which they can be deployed (e.g., membrane-based adsorption). Second, a comprehensive review of lithium extraction technologies is presented by examining the materials and platforms capable of achieving high extraction performances. Since the scope of this review is geared towards application in seawater and desalination brines (in particular, seawater reverse osmosis (SWRO) brine), we highlight the main challenges to date – selectivity required against competing ions and long-term stability against marine biofouling. Then, we put together an outlook, featuring our perspectives on next-generation materials and techno-economic analysis. Since the properties of desalination brines are unique from those of seawater, we also distinguish the traits of next-generation materials to be used for SWRO brines to provide insights for advancing new tailored materials and technologies for application in the latter. Overall, this review sums up state-of-the-art technologies for uranium and lithium extraction, putting into perspective various technology platforms to realize high extraction performances that can address our future demands for uranium and lithium at the water-energy nexus. [ABSTRACT FROM AUTHOR]

High‐precision separation with increased water permeability is critical for efficient membrane‐based water treatment processes. To achieve high selectivity toward different targeted species while allowing rapid water transportation, the structure of the membrane polyamide selective layer requires delicate regulation. Herein, an effective approach to systematically expand the pore size of polyamide layers by incorporating ammonium ion‐modified carbon dots (CDs) into the polyamide network is developed. The ammonium ions with different alkyl chain lengths attached to the CDs create nanochannels of different sizes in the network to lower the energy barrier for water transportation while maintaining high selectivity to targeted species. When the alkyl chain length of the ammonium ions reaches eight carbon atoms (i.e., C8 ions), the amphiphilic C8‐CDs induce the formation of the ridged nanostructure on the membrane surface and hence the increased membrane filtration area. The resultant thin‐film nanocomposite (TFN) membrane, denoted as the TFN‐C8‐CDs membrane, demonstrates a higher Na2SO4 rejection of 98.9% and NaCl/Na2SO4 selectivity of 83.1 than the pristine polyamide membrane, together with a tripled pure water permeability of 29.0 L m−2 h−1 bar−1. Herein, a viable approach for ingeniously designing the nanochannels and surface nanostructure of polyamide membranes for more efficient filtration processes is provided. [ABSTRACT FROM AUTHOR]

Featured Application: This article presents a discussion on the gains from enhancing salt rejection from a broad perspective, which includes the specific energy consumption and some insights into a technical direction to improve salt rejection of TFC-RO membranes. Since the specific energy consumption (SEC) required for reverse osmosis (RO) desalination has been steeply reduced over the past few decades, there is an increasing demand for high-selectivity membranes. However, it is still hard to find research papers empirically dealing with increasing the salt rejection of RO membranes and addressing the SEC change possibly occurring while increasing salt rejection. Herein, we examined the feasibility of the process and material approaches to increase the salt rejection of RO membranes from the perspective of the SEC and weighed up a better approach to increase salt rejection between the two approaches. A process approach was confirmed to have some inherent limitations in terms of the trade-off between water permeability and salt rejection. Furthermore, a process approach is inappropriate to alter the intrinsic salt permeability of RO membranes, such that it should be far from a fundamental improvement in the selectivity of RO membranes. Thus, we could conclude that a material approach is necessary to make a fundamental improvement in the selectivity of RO membranes. This paper also provides discussion on the specific demands for RO membranes featuring superior mechanical properties and excellent water/salt permselectivity to minimize membrane compaction while maximizing the selectivity. [ABSTRACT FROM AUTHOR]

Various pollutants of different sizes are directly (e.g., water-borne diseases) and indirectly (e.g., accumulation via trophic transfer) threatening our water health and safety. To cope with this matter, multifaceted approaches are required for advanced wastewater treatment more efficiently. Wastewater treatment using mixed matrix membranes (MMMs) could provide an excellent alternative since it could play two roles in pollutant removal by covering adsorption and size exclusion of water contaminants simultaneously. This paper provides an overview of the research progresses and trends on the emerging materials used to prepare MMMs for pollutant removal from water in the recent five years. The transition of the research trend was investigated, and the most preferred materials to prepare MMMs were weighed up based on the research trend. Various application examples where each emerging material was used have been introduced along with specific mechanisms underlying how the better performance was realized. Lastly, the perspective section addresses how to further improve the removal efficiency of pollutants in an aqueous phase, where we could find a niche to spot new materials to develop environmentally friendly MMMs, and where we could further apply MMMs. [ABSTRACT FROM AUTHOR]