Iron-Based Technique Shows Promise in Selenium Water Treatment

A research team at Washington University in St. Louis has developed an approach for removing selenium from water using a method called iron electrocoagulation.

The process could help meet the US Environmental Protection Agency’s limits on selenium concentrations in water discharged from industrial or agricultural sites.

Selenium is an essential trace element for many organisms, but it poses health and ecological risks when concentrations are too high or too low. It is highly water soluble, making its removal from aqueous systems particularly difficult.

The group focused on iron electrocoagulation, a method that introduces electric current to iron electrodes to produce iron-containing solids. These solids can adsorb selenium or promote its transformation into less soluble forms.

Iron corrosion method drives selenium binding

In one study, researchers used a flow-through electrocoagulation reactor designed with WaterTectonics, a company specializing in water treatment systems.

When a current is applied, the iron corrodes more rapidly than under natural conditions, forming reactive particles such as green rust. These particles are capable of binding selenium species and removing them from the water. Graduate student Xicheng He conducted the study in the university's Aquatic Chemistry Laboratory.

The experiment showed that over 98% of selenium was removed after just 11 seconds of water contact time, followed by 1 hour of settling. The selenium remained tightly bound in the residual solids, which were determined to be nonhazardous.

Water chemistry and reactor conditions influence effectiveness

A complementary study evaluated the performance of iron electrocoagulation under various water chemistry and electrochemical conditions. Graduate student Yihang Yuan tested 15 different combinations in a batch reactor system, adjusting parameters such as pH and dissolved oxygen.

These tests allowed the team to isolate specific variables that affect selenium removal and to construct a reaction-based model to predict performance under diverse environmental conditions.

Both studies were supported by the National Association for Water Innovation, funded by the US Department of Energy.

Future work expands to other contaminants

The research team plans to extend this work to include other contaminants and types of water samples. While the reactor design was not developed in-house, the group demonstrated that it can be applied to a wider range of treatment scenarios than originally intended.

Reference: He X, Flynn ED, Catalano JG, Giammar DE. Selenium(VI) removal by continuous flow-through iron electrocoagulation: effects of operating conditions and stability of selenium in residual solids. Environ Sci Technol. 2025. doi: 10.1021/acs.est.4c12305

This content includes text that has been generated with the assistance of AI. Technology Networks’ AI policy can be found here.