A Hundredfold More Powerful Nanofilter for Water Sanitation

According to the latest UNICEF report, 663 million people do not have access to adequate water supplies. This situation puts the lives of millions of children at risk. Access to drinking water has proven problematic even in countries with modern infrastructure, as witnessed by the contaminated water scandal in Flint, Michigan. In fact, the Flint River water was not treated properly, which caused pipe corrosion and the release of lead into drinking water. In 2015, residents learned that they had consumed lead-contaminated water, a pollutant that could cause serious illness. Following these revelations, the city’s residents spent a thousand days without access to drinking water. In this regard, researchers from RMIT University in Melbourne and the University of New South Wales in Sydney have created a new water sanitation technology that is fast, reusable and efficient.

Creating a Nanomaterial

The technology consists of a new sustainable, low-cost, environmentally friendly nanofilter, capable of filtering heavy metals and oils from water. It acts at the atomic scale and is one hundred times faster than current solutions. According to researcher Ali Zavabeti of RMIT University, the filter can also eliminate other pollutants. In fact, previous research has already shown that this technology effectively absorbs contaminants such as mercury, sulphates and phosphates.

To make the filter, the team designed and tested a new chemical manufacturing process. The process can be used in the development of other types of metal oxide-based compounds and also in catalysis, electronic, optic and other applications. The depollutant is designed from nanostructures that form on liquid metal. Usually, this type of material is made at very high temperatures, takes a long time and is obtained from toxic metals. The chemical process implemented by the team avoids all these problems. In addition, the material obtained is reusable.

Manufacturing Technique

The researchers created an alloy from liquid gallium and aluminum. When this alloy is brought into contact with water (liquid or vapour), aluminum oxide nanoparticles form on the surface. This operation requires the use of ultrasound. As this video explains, the process is used to activate a chemical reaction by acting on the molecular structure of a material.

Nanofibers, forming extremely thin and hydrophilic layers, appear after 5 minutes of immersion. They are 100,000 times thinner than a human hair and their surfaces are de facto porous. This atomic structure allows water to pass through while aluminum oxide compounds absorb the contaminants. The experiments conducted by the team showed the nanofilter’s effectiveness in absorbing lead and oil.

The study, entitled “Green Synthesis of Low-Dimensional Aluminum Oxide Hydroxide and Oxide Using Liquid Metal Reaction Media: Ultrahigh Flux Membranes,” was published in Advanced Functional Materials on September 21, 2018. It was co-authored by Ali Zavabeti, Bao Yue Zhang, Isabela A. de Castro, Jian Zhen, Benjamin J. Carey, Mohiuddin MD, RobiS. Datta, Chenglong Xu, Adrian P. Mouritz, Christopher F. McConville, Anthony P. O’Mullane, Torben Daeneke, and Kourosh Kalantar-Zadeh.

The research was funded by the Australian Research Council Center for Future Low-Energy Electronics Technologies (FLEET).