Engineering a Biopolymer-Based Ultrafast Permeable Aerogel Membrane Decorated with Task-Specific Fe–Al Nanocomposites for Robust Water Purification
Manohara Halanur Mruthunjayappa, Vibha Sharma, D. Kalpana, S.K. Nataraj, Dibyendu Mondal
Abstract
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.