Gallium-aluminum coagulant is a chemical widely used to clean bodies of water off bacteria, viruses, and all kinds of contaminants. Researchers at Sandia National Lab have discovered that by substituting the gallium atom in the compound, the new chemical performs at a much higher effective rate.
The water-treatment reagent, known as a coagulant, is made by substituting an atom of gallium in the center of an aluminum oxide cluster — itself a commonly used coagulant in water purification, says Nyman.
The substitution isn’t performed atom by atom using nanoscopic tweezers but rather uses a simple chemical process of dissolving aluminum salts in water, gallium salts into a sodium hydroxide solution and then slowly adding the sodium hydroxide solution to the aluminum solution while heating.
“The substitution of a single gallium atom in that compound makes a big difference,” said Nyman. “It greatly improves the stability and effectiveness of the reagent. We’ve done side-by-side tests with a variety of commercially available products. For almost every case, ours performs best under a wide range of conditions.”
Wide-ranging conditions are inevitable, she said, when dealing with a natural water source such as a river. “You get seasonal and even daily fluctuations in pH, temperature, turbidity and water chemistry. And a river in central New Mexico has very different conditions than say, a river in Ohio.”
The Sandia coagulant attracts and binds contaminants so well because it maintains its electrostatic charge more reliably than conventional coagulants made without gallium, itself a harmless addition.
The new material also resists converting to larger, less-reactive aggregates before it is used. This means it maintains a longer shelf life, avoiding the problem faced by related commercially available products that aggregate over time.
Press release: Purer water made possible by Sandia advance…
Image: This bar graph shows the efficacy of removing wild-type bacteriophage from Rio Grande water using the all-aluminum coagulant (yellow), the gallium-aluminum coagulant (pink) and a germanium-aluminum coagulant (green). While the gallium-aluminum coagulant is most effective, the germanium-aluminum coagulant is less effective than the all-aluminum coagulant. The gallium makes the active ingredient for binding contaminants more stable and effective, while the germanium, introduced as another variable, was found to make the active ingredient less stable and less effective.
Abstract in Environmental Science & Technology: Enhanced Water Purification: A Single Atom Makes a Difference…