Water is an increasingly scarce resource, with natural reserves depleting rapidly. The United Nations Environment Program (UNEP) has identified around 2.4 billion people as living in areas identified as water-stressed, where more than 25 percent of renewable freshwater resources are utilized to meet local demands.
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Regions particularly affected include Southern and Central Asia, as well as North Africa, where the situation is critical. Even countries with advanced infrastructure, such as the United States, are experiencing record-low water levels.1
In response to this global challenge, governments are adopting drastic measures to secure safe and clean water for domestic and industrial purposes. Advances in water purification technologies, particularly through the development of new materials for water purification systems, are proving to be a pivotal solution. These innovations enhance cleaning efficiency and effectively remove harmful bacteria and chemicals.2
These next-generation materials are shaping the future of the water purification industry and are essential for human survival in the future.
Advanced Materials in Water Purification
Experts have shown a growing interest in seamless covalent networks consisting of 2D graphitic carbon (G) sheets and 1D carbon nanofibers (CF) with hierarchical porosity. These structures are useful for various engineering applications, particularly in water purification systems.3
These networks result from modifying natural precursors to develop modern, environmentally friendly, and sustainable filtration structures.
A recent breakthrough demonstrated the scalable fabrication of seamlessly interconnected, ultralightweight G and CF hierarchical aerogels from egg-white proteins without external templates.4
The five mm-thick G-CF aerogels were tested by placing them over a funnel's mouth and filtering seawater from the New Jersey shore at 0.5ml/min using gravity. After 50 filtration cycles through the G-CF aerogel, the filtered seawater was analyzed using inductively coupled plasma mass spectrometry (ICP-MS).
During the first cycle of seawater purification, approximately 13.1 % of Mg2+, 13.6 % of K+, and 17.9 % of Ca2+ ions were removed from the seawater. The ratio of salt ions decreased with each purification cycle.
By the end of 50 purification cycles, approximately 92 % of the ions were removed from the seawater. The salt adsorption capacity of the G-CF aerogels was determined to be around 32.6 g/g, which is higher than the average capacity reported previously.
The G-CF aerogel removed approximately 90 % of microplastics and other harmful substances from the water in the first cycle, achieving a 99.995 % removal rate of nano-plastic contaminants by the final cycle. The innovative method demonstrates a scalable and environmentally friendly approach based on the self-assembly of protein structures.
The chemical interconnection between graphitic carbon and CF structures significantly enhances the structural stability of the G-CF aerogels. This stability is crucial for maintaining consistent desalination and purification performance in modern filtration systems.
Among novel materials, nanostructured sorbents possess a high capacity for treating polluted water and can be customized to target specific pollutants.5 Recent advancements in polymer nanocomposites (PNC) have improved their effectiveness and expanded their use in water purification processes.
Simple and more affordable water filtration methods are gaining traction. These methods utilize recyclable, bio-based natural polymers such as chitosan, cellulose, and carbohydrate polymers, which are enhanced with nanoparticles, making them highly cost-effective and efficient.6
Other biobased materials, such as porous resins, polyaniline, alginate, nanofibers, and cellulose nanofillers (CNFs), are also extensively utilized in water purification processes. Their application helps eliminate harmful substances from water, ensuring its safety for human consumption.
Polymeric adsorptive membranes are widely recognized as effective solutions for pollution remediation and have numerous applications in wastewater treatment plants and household water purification.
These membranes can remove diverse classes of persistent and emerging chemical pollutants from wastewater, which may be resistant to conventional treatment methods.7 These applications demonstrate the efficiency of novel polymer materials and nanocomposites in enhancing water purification systems.
Breakthroughs in Solar-Driven Water Purification
Solar-driven water purification is increasingly recognized as an efficient and sustainable method for treating water by harnessing clean solar energy. Enhancing the efficiency of solar evaporation is a key objective for practical implementation.
This can be achieved by designing innovative photo-thermal materials that optimize heat localization and water transport pathways, reducing the energy required for water vaporization and making the process more energy-efficient and cost-effective.8
Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are extensively used for water treatment technologies due to their high surface area, porosity, and customizable structure and functionality.9
An example includes MOF-801 [Zr6O4(OH)4(fumarate)6 system], which has been utilized in a device to capture water from the atmosphere. This device can harvest approximately 2.8 liters of water per kilogram of MOF each day under natural sunlight. It can then purify the water for domestic use.
The thoughtful design of photocatalytic reactors is crucial for efficient photocatalytic water purification. These reactors hold a significant role in the photocatalytic water treatment sector. Selecting an appropriate reactor design and material can accelerate the rate of wastewater treatment and efficiently conserve energy.10
The utilization of BiFeO3-MOF complex materials in novel ternary separable visible light photocatalysts has demonstrated promising results. These materials enhance the separation and migration rate of photo-induced charges and thereby improve photocatalytic efficiency.
Researchers have also engineered a palladium-vanadium-based photocatalytic reactor for wastewater purification. This reactor outperforms flat plate reactors by 132 % in terms of speed and energy efficiency for the photocatalytic degradation of phenol. The reactors’ outstanding performance is largely attributed to its highly exposed catalyst surface area.
These advancements suggest a bright future for photocatalytic water treatment, with the potential for further exploration and optimization of reactor models for enhanced performance.11
Challenges and Future Innovations
Despite rapid progress in water purification technologies, challenges such as high development costs, scalability issues, and the complex integration of modern materials into existing infrastructure remain significant hurdles.
However, the application of modern technologies, such as Machine Learning (ML) algorithms, is accelerating the development of optimized materials for water purification.
Governments worldwide are investing in advanced technologies, such as reverse osmosis and the development of eco-friendly materials, ensuring that water purification continues to advance rapidly.
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References and Further Reading
[1] UNEP. (2024). As shortages mount, countries hunt for novel sources of water. [Online] UNEP. Available at: https://www.unep.org/news-and-stories/story/shortages-mount-countries-hunt-novel-sources-water (Accessed on 13 April 2024)
[2] Razgaitis, R. (2023). Growth Trends In The Water Purification Industry. [Online] Forbes. Available at: https://www.forbes.com/sites/forbesbusinesscouncil/2023/11/15/growth-trends-in-the-water-purification-industry/?sh=277932607a1c
(Accessed on 13 April 2024)
[3] Owuor, P., et al. (2021). Roadblocks faced by graphene in replacing graphite in large-scale applications. Oxford Open Materials Science. doi.org/10.1093/oxfmat/itab004
[4] Ozden, S., et al. (2022). Egg protein-derived ultralightweight hybrid monolithic aerogel for water purification. Materials Today. doi.org/10.1016/j.mattod.2022.08.001
[5] Singh, V. (2022). Green nanotechnology for environmental remediation. In Sustainable nanotechnology for environmental remediation. Micro and Nano Technologies. doi.org/10.1016/B978-0-12-824547-7.00017-5
[6] Potara, M., et al. (2018). Polymer-coated plasmonic nanoparticles for environmental remediation: synthesis, functionalization, and properties. New polymer nanocomposites for environmental remediation. doi.org/10.1016/B978-0-12-811033-1.00015-9
[7] Adeola, A., et al. (2022). Advanced Polymeric Nanocomposites for Water Treatment Applications: A Holistic Perspective. Polymers. doi.org/10.3390/polym14122462
[8] Cao, S., et al. (2023). Emerging materials for interfacial solar‐driven water purification. Angewandte Chemie International Edition. doi.org/10.1002/anie.202214391
[9] Xia, Z., et al. (2021). Covalent organic frameworks for water treatment. Advanced Materials Interfaces. doi.org/10.1002/admi.202001507
[10] Sacco, O., et al. (2020). Main parameters influencing the design of photocatalytic reactors for wastewater treatment: A mini-review. Journal of Chemical Technology & Biotechnology. doi.org/10.1002/jctb.6488
[11] Ren, G., et al. (2021). Recent Advances of Photocatalytic Application in Water Treatment: A Review. Nanomaterials. doi.org/10.3390/nano11071804
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