The development of a stable and high-performance MXene membrane for the treatment of drinking water is reported in a recent study published in the Journal of Membrane Science.
Study: Preparation and evaluation of a high performance Ti3C2Tx-MXene membrane for drinking water treatment. Image Credit: Alina Kruk/Shutterstock.com
MXenes: An Important Family of Nanomaterials
MXenes are used in the design of rechargeable batteries, sodium-ion fuel cells, and superconductors due to their high conductance and remarkable electrochemical efficiency. In applications related to the environment, MXenes can be employed as catalysts or co-catalysts for photo electrocatalytic water separation and electrocatalytic carbon dioxide reduction, as well as the removal of contaminants from water, such as toxic metal ions, coloring agents, and nuclear waste.
To date, titanium carbide (Ti3C2Tx) is the most researched group of MXenes, having been developed as a membrane substance for water filtration and detoxification. According to recent research, the two-dimensional membrane created by layering MXene nanofibers has uniform and controlled transmission channels, numerous high specific surface areas, and hydrophilic qualities, which can improve water transmission and efficiently screen contaminants in the water.
Global Problem of Water Shortage and Pollution
The worldwide usage of water supplies is growing at a rate of around 1% annually, and this trend is expected to continue as water requirement rises and the effects of climate change deepen. Owing to rising water contamination and water scarcity, drinking water supplies have had to be derived from diverse reservoirs, which are typically contaminated by various pollutants.
The membrane filtration technique has emerged as a viable industrial option in the area of water purification due to its low cost, excellent performance, and ease of use. However, these membranes still face significant challenges and hurdles, such as inadequate contaminant rejection, poor mechanical qualities, high power consumption, and the limited chemical stability of certain polymeric membranes. As a result, MXenes nanosheets provide an appealing alternative to standard membranes for water treatment applications.
Limitations of Previous Studies
Previous research has shown that corrosion of multi-layer or single-layer Ti3C2Tx-MXene converts it to undesirable titanium oxide (TiO2) in both moist air and water. A pure MXene film, like graphene oxide (GO), is susceptible to swelling in the hot and humid environment, which has a significant impact on its ability to retain contaminants. Thus, it is critical to investigate MXene's water durability since water absorption is unavoidable in many actual application settings, whether in the manufacturing or application stages.
As a result, a strategy for protecting the MXene mixture against degradation should be developed to assure its long-term use in an aquatic environment. High stability (including stable interlayer distance and barrier morphology) is required for the membrane to be employed effectively in the practical filtration system and for long-term operation.
Important Findings of the Study
In this study, the researchers described a new approach for making an aluminum ion cross-linked MXene-ascorbic acid membrane that stabilizes MXene interlayer separation, prevents swelling, and improves MXene corrosion protection. The connection mechanism between aluminum ions, ascorbic acid, and the MXene sheet was investigated, along with the linkage between membrane structure and membrane efficiency, treatment effectiveness (pollutant persistence), and membrane long-term durability.
The absorption of ascorbic acid on MXene considerably reduced its degradation, extending not only the storage period but also the life span of the MXene coating. In comparison to the unprocessed MXene substrate, intercalated titanium and aluminum membrane (MVCAl) functioned well in the 30-day stability study after crosslinking with aluminum ions.
Furthermore, the MVCAl had a remarkable dye rejection rate of 99.25 percent, with just 7.94 percent retention. During forward filtration, the MVCAl membrane efficiently blocked sodium chloride and magnesium chloride transmembrane transfer. In one hour, the penetration of sodium chloride was almost 0.065%. Additionally, MVCAl barely swelled in water, indicating that it possessed a significant anti-swelling function.
In this work, the researchers used ascorbic acid and aluminum ion binding to produce and evaluate an MXene membrane with high swelling resilience and substrate refusal. The simple and uncomplicated technique described in this work for manufacturing MXene sheets is expected to pave the way for future practical uses of MXene-based membranes in saltwater distillation and other water purification industries.
Liu, X. et al. (2022). Preparation and evaluation of a high-performance Ti3C2Tx-MXene membrane for drinking water treatment. Journal of Membrane Science. Available at: https://www.sciencedirect.com/science/article/pii/S0376738822002162?via%3Dihub