How to Convert Sea Water into Fresh Water

As the world’s population grows and climate change brings more wildfires and drought, clean water is becoming an increasingly precious resource.

According to the UN report in 2019, nearly half of the world's population (about 3.6 billion) live in areas potentially short of water for at least one month each year. If proper measures are not taken, this number will rise to 4.8 to 5.7 billion by 2050. To solve the shortage of water resources, there is a seemingly very simple method- converting sea water into fresh water. The challenge is to do it on a large scale using low cost, sustainable methods.

Researchers at the University of Colorado at Boulder and the University of Maryland believe wood could be the answer. They used wood to make an ultra-thin filter membrane to desalinate and purify water. According to a report on this research by Science Advances, this 0.5 mm membrane may become a sustainable alternative to the petroleum-derived plastic membranes widely used in desalination plants.

Traditional Desalination Methods

In fact, some water-scarce areas have successfully obtained clean, drinkable fresh water from seawater. In regions such as the Middle East and California, desalination plants are already supplying water for residents. Most rely on the reverse osmosis process, in which seawater is forced into porous membranes and filtered to remove salt and impurities. However, this method not only consumes huge energy, but also consumes expensive plastic filter membranes, which are also very prone to clogging, leading to greater costs.

At that moment, membrane distillation technology , a seawater desalination technology that has not yet been commercialized , has attracted attention due to its energy-saving and environmentally-friendly characteristics and has entered people's field of vision. The so-called "membrane distillation" is the use of solar energy to evaporate seawater, and the water vapor is filtered through a hydrophobic membrane, and then condensed to become clean fresh water. However, the hydrophobic membrane used in this treatment is made of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP) and other high polymers based on the petroleum industry. On the one hand, these materials are not suitable for efficient heat preservation, on the other hand, they are difficult to degrade and easily cause environmental problems. Therefore, limited by cost and energy consumption, this technology cannot be widely used.