A revolutionary new purification system uses metal-organic frameworks to break down pollutants on a molecular level. The system packs a double benefit by producing hydrogen that can be captured and used in other energy solutions.
The research could provide yet another clean solution to giving clean water to the 1 billion people around the world who don't have access to it.
A team from Ecole Polytechnique Fédérale de Lausanne's Institute of Chemical Sciences and Engineering developed the photocatalytic process. They tapped into what they called "some of the most useful and versatile materials today," metal-organic frameworks (or MOFs).
MOFs are "a class of materials demonstrating structural versatility, high porosity, fascinating optical and electronic properties, all of which makes them promising candidates for a variety of applications, including gas capture and separation, sensors, and photocatalysis," the researchers explained in a statement.
Splitting water to remove pollutants
The system the international researchers developed used two types of photocatalysis. The first photocatalysis was called "organic pollutant degradation." In short, the MOFs broke down any pollutants that could be found in water.
The team tested just how good the MOF system was at removing pollutants by seeing how the system degraded the toxic rhodamine B dye. Rhodamine b has been used in the past to simulate organic pollutants in a laboratory setting.
The MOF proved highly successful in breaking down the rhodamine B in a single process.
"This noble-metal free photocatalytic system brings the field of photocatalysis a step closer to practical 'solar-driven' applications and showcases the great potential of MOFs in this field," said researcher Kyriakos Stylianou.
The second benefit and photocatalysis system involved hydrogen production from splitting the water. The reaction divided the water into its base elements: hydrogen and oxygen. However, the researchers at EPFL wanted to use the hydrogen produced in fuel cells.
Hydrogen fuel cells (most commonly seen as Proton Exchange Membrane cells) use hydrogen and oxygen for fuel. Unlike other engines like internal combustion engines, coal-burning solutions, and nuclear power, hydrogen fuel cells don't produce harmful by-products. It only produces water, electricity, and heat.
The researchers performed the tests on the water purifications in a particular order. First, they showed that the MOF-based system could generate hydrogen and that secondly, it degraded rhodamine B at the same time.
MOFs for the ultimate water purification solution
This isn't the EPFL's only MOF-based water purification solution. In March, a separate team of chemists from the institution used MOFs to pull water vapor and other gases from the air. By leveraging that technology, the researchers were then able to remove heavy metals from water on a molecular scale.
They developed a MOF/polymer composite using cheap and environmentally-friendly materials. The final composite removed high amounts of metals like lead and mercury from real-world water samples. The EPFL team reported in March that the MOFs could remove 1.6 times its own weight in mercury alone.
Both MOF solutions could prove powerful allies for scientists desperately trying to find clean water solutions in remote locations or in places like Flint, Michigan with high water pollution.