Rice is the most-eaten food on the planet, and its discarded outer husk results in some 300 billion pounds of waste per year. FIU chemistry researcher Islam Ibrahim Hussein says the inedible castoffs could be the key to cleaner water.
Rice husk, an agricultural byproduct, is at the center of his research to develop a more sustainable way to remove contaminants from water. Working as part of an international team of scientists, the researchers converted the discarded rice husk into a sponge-like filter capable of capturing industrial synthetic dyes. In the first round of tests, the material captured brilliant green and malachite green dyes, two industrial dyes commonly used to evaluate water treatment technologies. The findings suggest the material could become a promising approach for removing contaminants from water while also reducing agricultural waste.
Not only was the material effective. It's also reusable. The researchers used the same material in subsequent tests and found it can be reused at least five times without any loss of effectiveness. The team also evaluated the environmental cost of making the material, something research often overlooks. When rice husk is discarded, it can create environmental challenges, especially when it is burned, releasing pollutants into the air, or improperly disposed of in large quantities. So, by using an agricultural byproduct that would otherwise go to waste, the researchers say they can reduce the overall environmental footprint of creating the filter.
"We need green methods or friendly methods that will not create another problem in the future," said Hussein.
The process to convert the rice husks begins with heating the waste in a low-oxygen environment to convert it into biochar, the sponge-like material that can trap contaminants. The researchers then combine it with magnesium and aluminum to create a composite material designed to capture pollutants more effectively.
"The biochar has a high surface area, so it can trap and capture a lot of contaminants," said Hussein.
The researchers focused on removing dyes that are used in textile manufacturing, leather processing, paper production, and aquaculture. These dyes are toxic, can persist for years in the environment, and some are suspected carcinogens. The research paper notes that the textile industry alone accounts for roughly 17–20% of industrial water pollution, and dye contamination is a major issue in Asian countries with large textile industries.
Although the material has shown promising results in laboratory testing, Hussein says more research is needed before it can be used on a larger scale. Future studies will examine whether the material can remove additional dyes, heavy metals and other contaminants found in real-world water samples.
Hussein and his collaborators hope that, with further development and scaling, the technology could one day help communities around the world access cleaner water.
"My dream is to scale up this research and make it more effective to help the community or other people who need water," said Hussein.
Research for this study was conducted in collaboration with Nazrul Haq of King Saud University in Riyadh, Saudi Arabia, and George V. Belessiotis of the National Technical University of Athens in Greece.
