Engineering Biopolymer-based Ultrafast Permeable Aerogel Membrane Decorated with Task-specific Fe-Al Nanocomposites for Robust Water Purification

The present work demonstrates an innovative strategy for robust water purification using an engineered aerogel membrane fabricated from biopolymers and task-specific Fe–Al-based nanocomposites. The as-prepared ethylenediaminetetraacetate dianhydride cross-linked chitosan- and agarose (7:3 weight ratio)-based aerogel membrane decorated with α-FeOOH- and γ-AlOOH-based nanocomposites was characterized using various analytical tools, which suggested formation of a highly stable network interconnected through covalent and electrostatic interactions. The optimized bionanocomposite-based aerogel (BNC-AG-0.1) membrane showed macroporous and partial unidirectional short-range channels with an ultralow density of 0.021 g·m–2, a high swelling ratio of 1974%, and a remarkable pure water flux of 19,228 L·m–2·h–1 (>6-fold higher flux compared to the reported aerogel membranes). The aerogel membranes were successfully utilized for purification of diverse pollutants such as dyes, emerging pollutants (EPs), arsenate, and fluoride in a continuous flow method under gravitational force. The BNC-AG-0.1 membrane exhibits high rejection (95–98.6%) for both cationic and anionic dyes with a flux rate of 1150–1375 L·m–2·h–1 and a rejection of 89–92% for EPs with a flux rate of 1098–1165 L·m–2·h–1. Moreover, the BNC-AG-0.1 membrane showed a qmax of 102.45 mg·g–1 (at pH 6.5) for As­(V) with >93% rejection at a flow rate of 1000 L·m–2·h–1. Furthermore, the aerogel membrane showed an excellent removal efficiency (92%) of arsenic up to the 10th cycle and hence demonstrated as a potential adsorption-based membrane for arsenic-free potable water. On the other hand, the BNC-AG-0.1 membrane showed a qmax of 81.56 mg·g–1 (at pH 6.5) for F– removal with >99% rejection at a flow rate of 250 L·m–2·h–1. When applied for real-water purification, approximately 4734 L of safe drinking water (the F– concentration is less than the WHO permissible limit) per square meter of the aerogel membrane can be obtained with a flux rate of 250 L·m–2·h–1. Overall, the prepared aerogel membrane showed robust removal of a variety of contaminants with ultrafast water permeation and established excellent recyclability.