New Method for Water Purification

In a study published in Nature Communications, scientists from Heidelberg University (Germany), Kyoto University, and Osaka University (Japan) from the HeKKSaGOn Alliance used a protein found in plants as inspiration to develop a novel method of removing dangerous heavy-metal ions from water.

Clean drinking water is an essential requirement for health and well-being. However, as the world’s population expands, attaining this for all communities becomes increasingly difficult.

Although existing water-purification technologies are efficient for vast quantities of water, they are not selective to heavy metal ions. This means they also remove harmless ions, making these treatments less effective.

Phytochelatin, a highly conserved protein in plants, does not have this issue. Phytochelatin selectively binds to heavy metal ions and transports them to the cellular compartment, where they cannot cause harm.

The researchers sought to discover how phytochelatin does this. They examined the basic building blocks of phytochelatin to identify how it selects and binds to certain ions, in this instance, cadmium.

We identified two groups—carboxylate and thiolate—and synthesized a polymer containing these groups.

Masaki Nakahata, Study Lead Author and Assistant Professor, Osaka University

The researchers concentrated the polymer into a tiny volume by binding it to cellulose membranes and silica beads. After passing contaminated water through the polymer, the researchers were able to remove cadmium ions from the sample with excellent efficiency and reach a safe drinking level in just one hour.

It was demonstrated that the polymer structure’s ability to include both carboxylate and thiolate groups was essential to its success. Restricting it to an incredibly small volume and establishing a flow-through system significantly increased the polymer’s loading capacity.

The system had high specificity for cadmium ions compared to metal ions necessary for health, such as magnesium and calcium. This polymer can also have a high affinity for mercury ions, implying that it could be useful in eliminating other heavy metals.

It is no surprise to us that plants gained such a highly sophisticated machinery during the evolution because biology doesn’t make nonsense. However, we were excited to see that our plant-inspired polymer manages to even surpass what plant proteins can do.

Motomu Tanaka, Study Senior Author and Scientist, Kyoto University

Tanaka was also a scientist at Heidelberg University.

The study team’s success in synthesizing a polymer inspired by a plant protein to absorb cadmium ions is encouraging since the polymer is selective to harmful heavy metal ions and operates via a flow-through mechanism. These characteristics will likely boost water treatment efficiency, which is good news for clean water.

Journal Reference:

Nakahata, M., et al. (2024) Hyperconfined bio-inspired Polymers in Integrative Flow-Through Systems for Highly Selective Removal of Heavy Metal Ions. Nature Communications. doi:10.1038/s41467-024-49869-8