By Peter Chawaga, Associate Editor, Water Online
Industrial wastewater poses unique challenges for those tasked with cleaning it before it enters source supplies. Depending on the specific industry — be it textiles, mining, or something else — impurities can be particularly difficult to remove.
But new research may have uncovered a helpful tool for these industrial treatment operations, modifying an unlikely aide into a unique solution.
Researchers from Edith Cowan University (ECU) in Western Australia have successfully manipulated the atomic structure of iron, creating a metal that can quickly and efficiently remove impurities from wastewater. They call their creation “metallic glass” and see it as particularly beneficial for removing the types of contaminants that result from textile and mining operations.
“Traditional methods to treat textile wastewater and reduce sludge in mining require expensive infrastructure and complicated chemistry,” said Dr. Laichang Zhang, an associate professor and researcher at ECU’s School of Engineering. “However, by using the metallic glasses in these industries, the wastewater sludge containing heavy metals in mining could be highly reduced and the textile pollutants (i.e., dyes) with refractory structure could be effectively degraded to harmless final products without complicated operations, which is very useful for the mining and textile [industries].”
For Zhang, the research was inspired by the fact that wastewater in these sectors poses an acute threat to the world’s already endangered potable supplies.
“The global usage of potable water, especially in the urbanized center of the industrialized field, is totally unsustainable and is at a crisis level,” he said. “The industrial processes and manufacturing operations are also responsible for exerting additional pressure on the existing water supplies. Many countries and governments have requested industrials, especially those in the chemical mining field, to control or degrade the wastewater … before discharge… Therefore, different sectors always need new technology to process wastewater.”
But transforming the atomic structure of iron to create metallic glass is no simple process. According to Zhang, scientists have been looking into this type of manipulation since the ’60s, melting and then rapidly cooling metals so that their atoms don’t have time to reorder themselves and are arranged randomly, creating solids with the same atomic structures as liquids. And the specific way that this metallic glass can remove impurities is highly-technical as well.
“The metallic glasses degrade impurities from water by a Fenton-like process using hydrogen peroxide as an oxidant,” Zhang said. “Under the atmospheric pressure and ambient temperature, the iron-based metallic glass could rapidly activate hydrogen peroxide to produce large amounts of reactive species, called hydroxyl radicals, which have a superior ability to destroy the chemical structure of pollutants, leading to formation of carbon dioxide, water, and other harmless, inorganic molecules.”
Despite the advanced chemistry it entails, the metallic glass process has some key advantages over traditional methods for removing impurities.
“Traditional wastewater treatment methods usually receive unsatisfied efficiency and secondary pollution (e.g., a large amount of sludge produced), as well as the increased cost of purifying secondary sludge,” said Zhang. “However, by using iron-based metallic glasses as the catalyst in the water remediation, the pollutants could be removed in an ultrafast efficiency of less than 15 minutes and achieved complete conversion to harmless final products. In addition, the iron-based metallic glasses are very easy to be collected and reused, where the metallic glasses could be reused at least 20 times without apparent decreasing or degradation efficiency.”
While the team at ECU has reason for optimism around this solution, they do acknowledge that it will be a challenge to bring it from the laboratory to the highly-regulated world of industrial wastewater treatment.
“The actual industrial [practice] is generally much more complicated than the experimental environment, where the wastewater consists of a mixture with complicated constituents,” Zhang said. “To realize industrial application, many efforts must be made. Based on the existing research achievements, we expect this technology could be possibly realized and applied in industry before 2025.”
By then, the solution will no doubt still be desperately needed.