Abstract

The compromise of permeability and selectivity is a central paradigm in gills by which the gill filaments perform rapid intake of oxygen (O2) and rejection of carbon dioxide (CO2) in a benign physiological environment. Such an efficient separation in nature is a key dogma in designing biomimetic separation systems, yet the fundamental challenge of the permeability–selectivity trade-off still remains a nascence. In this study, we report a gill-inspired diffusion dialysis membrane for acid recovery from heavy metal wastewater with a high permeation efficiency of acid ions (H+) and robust rejection of cadmium ions (Cd2+) plus stable performances against repeated separations. This membrane was fabricated by vacuum filtration of a nanocomposite regime featuring natural protein nanoparticles attached to the rod-shaped attapulgites. The stacking of such anisotropic building blocks endowed the membranes with capacious channels for H+ transport, while the electropositivity of proteins enabled robust rejection of Cd2+. The enhanced separation performance of this membrane mimicked the art of gills with gill arches, enlarging the specific area of gill filaments arresting O2 but expelling CO2. As a result, the membrane exhibited a high H+ dialysis coefficient (0.049 m·h–1) and H+/Cd2+ selectivity (SH/Cd = 23.3) with excellent long-term operational stability and general applicability (SH/Cu = 26.3, SH/Pb = 18.1, SH/Ca = 23.3, and SH/Mg = 18.6) suitable for practical applications.