A novel method for accelerating the evaporation of seawater more efficiently than freshwater has been lauded as a groundbreaking innovation in desalination technology. This advance could bring critical relief to billions of people across the globe, particularly as freshwater scarcity intensifies due to climate change and population growth.
Today, up to 36% of the global population—roughly 2.88 billion people—suffers from severe freshwater shortages for at least four months annually. Projections suggest that by 2050, this figure could climb to 75% of the world’s population, creating a dire situation that threatens human survival and global stability. In this context, seawater desalination has emerged as one of the most viable solutions to address the looming water crisis. However, current desalination technologies are energy-intensive and contribute significantly to greenhouse gas emissions, raising concerns about their environmental sustainability.
Researchers at the University of South Australia (UniSA) have been exploring interfacial solar-powered evaporation, a promising alternative that harnesses solar energy to desalinate water with minimal energy input. This method has shown potential as an energy-efficient and sustainable solution. However, a persistent challenge has been the slower evaporation rate of seawater compared to freshwater, primarily due to the inhibitory effects of salt ions on evaporation processes.
In an innovative collaboration with Chinese researchers, Professor Haolan Xu from UniSA has spearheaded a project to overcome this obstacle. Their research, recently published in the journal Advanced Materials, introduces a cost-effective strategy that enhances seawater evaporation rates significantly, marking a major milestone in desalination science.
The research team developed a floating photothermal hydrogel evaporator by integrating affordable clay minerals with carbon nanotubes and sodium alginate. The minerals included halloysite nanotubes, bentonite, zeolite, and montmorillonite. This combination proved to be transformative, enabling seawater evaporation rates that were 18.8% higher than those of pure water. This achievement represents a significant leap, as previous studies had consistently reported seawater evaporation rates to be approximately 8% lower than those of pure water.
At the core of this breakthrough is the exploitation of an ion exchange process at the air-water interface. According to Professor Xu, the minerals selectively attract and concentrate magnesium and calcium ions from seawater at the evaporation surface. This interaction enhances the evaporation rate without requiring external energy inputs, making the process both efficient and economical. The natural occurrence of this ion exchange during solar evaporation adds to its practicality, as it can be seamlessly integrated into existing desalination technologies.
The implications of this development are substantial. Globally, there are around 17,000 operational desalination plants. Even marginal improvements in desalination efficiency can translate into the recovery of tens of millions of tons of clean water, addressing water shortages in regions where freshwater resources are critically limited. This new hydrogel evaporator, designed for durability, maintained its performance even after months of continuous immersion in seawater, demonstrating its suitability for long-term applications.
Looking ahead, the researchers aim to refine this technology further by exploring additional strategies to accelerate seawater evaporation beyond the levels currently achieved. Their ultimate goal is to implement these advancements in practical desalination systems, thereby expanding global access to clean water.
This innovation comes at a crucial time when global water resources are under immense pressure. By offering a low-cost, energy-efficient solution to desalination, this technology could play a pivotal role in mitigating the impacts of water scarcity and ensuring a sustainable future for billions of people worldwide.
Source: University of South Australia