Engineering a Biopolymer-Based Ultrafast Permeable Aerogel Membrane Decorated with Task-Specific Fe–Al Nanocomposites for Robust Water Purification

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Abstract
The present work demonstrates an innovative strategy for robust water purification using an engi-neered aerogel membrane fabricated from biopolymers and task-specific Fe-Al based nanocomposites. The as prepared EDTAD cross-linked chitosan and agarose (7:3 weight ratio) based aerogel membrane decorated with α-FeOOH and γ-AlOOH based nanocomposites were characterised using various analyt-ical tools which suggested formation of a highly stable network interconnected through covalent and electrostatic interactions. The optimized bionanocomposite–based aerogel membrane (BNC-AG-0.1) showed macro-porous and partial unidirectional short range channels with ultra-low density of 0.021 g.m-2, 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, arsenate and fluoride in a con-tinuous flow method under gravitational force. BNC-AG-0.1 membrane exhibits high rejection (95-98.6%) for both cationic and anionic dyes with the flux rate of 1150-1375 L.m-2.h-1 and 89-92% rejection for emerging pollutants with the flux rate of 1098-1165 L.m-2.h-1. Moreover, BNC-AG-0.1 membrane showed 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 upto 10th cycle, hence, demonstrated as a potential adsorption-based membrane for arsenic-free potable water. On the other hand, BNC-AG-0.1 membrane showed 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 (F- concentration less than WHO permissible limit) per m2 of aerogel membrane can be obtained with flux rate of 250 L.m-2.h-1. Overall, the prepared aerogel membrane showed robust removal of variety of contaminants with ultrafast water permeation and established excellent recyclability.
Funding Information
  • Anusandhan National Research Foundation (EEQ/2017/000417)
  • Nano Mission Council, Department of Science and Technology (DST/TMD/HFC/2K18/124G, SR/NM/NT-1073/2016)
  • Community of Madrid (2017-T1/AMB5610)

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