In the face of rising energy demands for high-salinity wastewater treatment, the abundant salt content presents a novel opportunity for salinity gradient energy harvesting, which can drive metal recovery processes. A “waste-controls-waste” strategy was developed by exploiting the salinity gradient to drive chromium reduction, achieving synergistic energy recovery and heavy metal removal. Based on this, an asymmetric nanochannel was designed to couple high-salinity and Cr-containing wastewater, enabling a green, self-powered treatment process. A cation-selective heterogeneous membrane was fabricated via a facile vacuum filtration method, wherein one-dimensional aramid nanofibers (ANFs) were intercalated between two-dimensional graphene oxide (GO) sheets to form an ordered lamellar structure. The structure was subsequently assembled onto an anodized aluminum oxide (AAO) substrate. The ANF-GO/AAO membrane, with a “line-plane” hybrid architecture, exhibited high cation selectivity and pronounced ion rectification due to its bipolar charge configuration. By mixing high-salinity wastewater and Cr-laden wastewater through the ANF-GO/AAO membrane, substantially high-power density of up to 39.22 W m⁻² was achieved, along with an energy conversion efficiency of 25.60% under extreme salinity gradients. Nernst-Planck simulations revealed that ion selectivity and energy conversion in the heterogeneous membranes are dictated by their asymmetric architecture and the negatively charged selective layer. The harvested electrical energy directly drove the electrochemical reduction of Cr (VI), achieving a removal amount of 18.77 mol cm⁻² under acidic conditions. A “waste-controls-waste” strategy harnesses salinity gradients to drive Cr(VI) reduction, achieving simultaneous energy recovery and heavy metal removal. An asymmetric nanochannel couples high-salinity and Cr-laden wastewater, enabling a green, self-powered treatment system.

Drinking water distribution system (DWDS) necessitates sustainable, durable, and nonpolluting materials for enhanced water quality of the end-users. Stainless steel (SS) is gaining momentum in DWDS, particularly in end-point distribution facilities such as secondary water storage tanks, pumps, and household water pipes due to its high chemical stability and robust mechanical strength. However, SS’s susceptibility to corrosion in given defect areas is of great concern, and there is a lack of fundamental insight on SS corrosion from an interdisciplinary perspective of materials science and environmental science. Herein, the SS corrosion in the DWDS environment is critically assessed, encompassing the basic science of SS corrosion occurrence, its cascading influence on water quality, and anticorrosion strategies. Electrochemical corrosion mechanisms of SS corrosion are specifically differentiated, particularly those initiated at given SS defects, including welding points, grain boundaries, and areas with tensile stress. It is shown that SS corrosion influences water quality by destroying the Cr-rich passive film and releasing Cr, Fe, and other heavy metals from the corrosion scale. The critical factors influencing SS corrosion are subsequently identified, namely, SS elemental composition, SS manufacturing process (e.g., heat-affected zone, stress concentration), and water condition in DWDS (e.g., chlorine, oxygen, sulfate, hydraulic shock, pH). Corresponding strategies are elucidated to facilitate the anticorrosion resistance of SS and improve the water quality, including SS alloying enhancement, SS dispersion strengthening, SS surface treatment/modification, and tuning water condition in DWDS. Overall, this review highlights the importance of controlling SS corrosion, which could provide guidance on the rational design and utilization of SS in DWDS to enhance the ultimate water quality of the end-users and the overall resilience of the DWDS.