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Hard to soft

Scientists create surprising new material from mussel shell waste

Research

By Kelly Foss

Memorial scientists studying other uses for mussel shell waste have created a new material with surprising properties.

The increased production of shellfish worldwide to meet global needs for protein is leading to significant volumes of shells, which are rich in biorenewable calcium carbonate, being discarded.

Dr. Jennifer Murphy (PhD’19) was originally transforming the shells with acetic acid (vinegar) to make calcium acetate.

“She was looking to see if it could possibly be used as a de-icer – a local solution for treating roads in areas where there is mussel processing taking place and these shells are readily available,” said Dr. Murphy’s doctoral supervisor, Dr. Fran Kerton, Faculty of Science.

That was when Dr. Murphy noticed something very peculiar. What should have been a colourless solution, was a mess of white solid and leftover shells.

“I knew the water-soaked material had to be calcium carbonate – based on what I had put in the flask, there was nothing else chemically it could have been. However, I had no idea why it was forming with a sponge-like texture.”

Dr. Murphy presented the new finding with preliminary characterization showing it was made of calcite to Dr. Kerton. They both knew they had discovered a special material.

Published their findings

When wet, the material can be squeezed and water will run out of it, but when dry, it resembles cotton candy.

Sponge-like material made from waste mussel shells.
Photo: Submitted

The pair initially thought the calcium carbonate in the shell was dissolving and recrystallizing, but quickly learned that was not the case.

A key discovery came when they took a closer look at the morphology of the material using scanning electron microscopy.

They noticed the calcite in the sponge material had the same shape and size as calcite in blue mussel shells.

“It’s difficult to replicate inorganic materials the same way as many organisms, like mussels do,” said Dr. Murphy. “That is how we realized the prisms were coming free of the shell and recombining to make the soft calcite material.”

They also decided to connect with with Memorial’s Core Research Equipment and Instrument Training Network, specifically, Dr. Céline Schneider in the Centre for Chemical Analysis, Research and Training, to do solid state nuclear magnetic resonance analysis on the material.

The process gave them more insight into the material’s properties. Their findings were published in a paper for Matter, a Cell Press journal.

Deeper investigation

Dr. Kerton had plans to have a new student under her supervision to investigate potential uses for the material in September, but the international student was delayed getting to Memorial due to the COVID-19 pandemic.

“As scientists it is important to share our knowledge because you never know who may end up benefiting.” — Dr. Jennifer Murphy

She hopes a student who is joining her laboratory in January will also work with the new material.

“At the moment we are only able to make small amounts, a fifth of a gram, so we are going to combine it with other natural materials to see if we can get it to go a bit further,” she said.

“There are also various things we hoped it might do. If it could take water out of the air, it could be used in areas where there are shortages of fresh water, for example. Unfortunately, it didn’t do that, but it did absorb crude oil and dyes out of water, which could allow treatment of polluted waters with a natural material sourced from the oceans.”

Dr. Fran Kerton is hoping to continue investigating potential uses for the new material.
Photo: Rich Blenkinsopp

Dr. Murphy says she is always “amazed” when she thinks back to the events leading up to the calcite discovery.

“It was complete luck; I never could have anticipated that outcome,” she said. “As chemists, we try to make compounds and materials on purpose, and we are often disappointed if we fail to do so. When we get odd outcomes, it is up to us decide what we do with it. I think as scientists it is important to share our knowledge because you never know who may end up benefiting.”

Next up: Dr. Kerton wants to see if it will absorb pharmaceutical residues in water, which could be used during water treatment. She says it could also be used as a calcium supplement or a diluting agent when administering drugs. Since calcium carbonate is used in Tums to treat antacid, it’s safe for ingesting.


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