Layered Double Hydroxide/Boron Nitride Nanocomposite Membranes for Efficient Separation and Photodegradation of Water-Soluble Dyes

Increasing scarcity in access to clean, safe water is being fuelled by escalating industrialisation, rapid urbanisation and biodiversity loss, and the relentless forces of climate change. Therefore, the need for development of innovative and sustainable methods of water purification is of the utmost urgency. Nanofiltration is proving to be an increasingly attractive potential solution to this global issue.^1,2<br/>Previous reports of nanofiltration membranes using boron nitride (BN) and partially oxidised BN (BNOx) have demonstrated outstanding performance, achieving retentions of up to 100% for various water-soluble dyes which can be harmful to humans and aquatic life.^3,4 However, the main drawback of these membranes is their vulnerability to membrane fouling, meaning they must be disposed of after a single use. Consequently, innovative approaches to mitigate membrane fouling are crucial to ensure the long-term sustainability of current and future nanofiltration technologies. Herein, we report the development of novel high-performance nanofiltration membranes based on a recyclable CuAl-CO₃LDH/BNOx nanocomposite. These membranes have demonstrated up to 100% retention of several water-soluble dyes (Evans blue, methyl orange, methylene blue and rhodamine B). Additionally, they exhibit excellent water flux, over 2 orders of magnitude higher than commercially available nanofiltration membranes. The incorporation of CuAl-CO₃ LDH photocatalyst within the nanocomposite membranes enables up to 91% visible-light-induced photodegradation of these dyes within 120 minutes using a household LED lamp.<br/>This introduction of photocatalytic functionality into existing nanofiltration membranes offers a low-cost, innovative route to the mitigation of membrane fouling. Significantly, this work demonstrates the first instance of Evans blue degradation by a visible-light active LDH photocatalyst. Overall, we believe this work represents a significant advancement in the field of advanced nanofiltration technology, offering superior performance and enhanced sustainability.⁵<br/><br/><br/><u>References:</u><br/>1 - M. A. Montgomery and M. Elimelech, Water and sanitation in developing countries: Including health in the equation - Millions suffer from preventable illnesses and die every year, <i>Environ. Sci. Technol.</i>, 2007, <b>41</b>, 17–24.<br/><br/>2 - H. Guo, X. Li, W. Yang, Z. Yao, Y. Mei, L. E. Peng, Z. Yang, S. Shao and C. Y. Tang, Nanofiltration for drinking water treatment: a review, <i>Front. Chem. Sci. Eng. 2021 165</i>, 2021, <b>16</b>, 681–698.<br/><br/>3 - N. García. Doménech, F. Purcell-Milton, A. S. Arjona, M.-L. C. García, M. Ward, M. B. Cabré, A. Rafferty, K. McKelvey, P. Dunne and Y. K. Gun’ko, High-Performance Boron Nitride-Based Membranes for Water Purification, <i>Nanomater. 2022, Vol. 12, Page 473</i>, 2022, <b>12</b>, 473.<br/><br/>4 - N. García Doménech, Á. Coogan, F. Purcell-Milton, M. L. Casasín García, A. Sanz Arjona, M. Brunet Cabré, A. Rafferty, K. Mckelvey, P. W. Dunne and Y. K. Gun’ko, Partially oxidised boron nitride as a 2D nanomaterial for nanofiltration applications, <i>Nanoscale Adv.</i>, 2022, <b>4</b>, 4895–4904.<br/><br/>5 - Á. Coogan, N. García Doménech, D. Mc Ginley, T. Simonian, A. Rafferty, Q. Fedix, A. Donlon, V. Nicolosi and Y. K. Gun’ko, Layered double hydroxide/boron nitride nanocomposite membranes for efficient separation and photodegradation of water-soluble dyes, <i>J. Mater. Chem. A</i>, 2023, Advance Article, DOI:10.1039/D3TA01581E.