Photo: Niklas Björling
"We are developing some new concepts for nanomembrane that enables a circularity or upcycling of natural resources,” says Aji Mathew. Photo: Niklas Björling

What looks like a round white piece of paper is in fact a nanocellulose membrane, which has been shown to have unique properties for purifying the waste water of the mining industry. The membrane is one of the bio-based nanomaterials that Professor Aji Mathew and her research team at the Department of Materials and Environment Chemistry at Stockholm University have designed and built from scratch.

“We have had very good results in testing the filter material for water from mining industry in Sweden and mirror industry from Southern Europe,” says Aji Mathew.

Separation of effluent water from mining

The effluent water from the mining industry contains metals, such as copper and silver. With nanocellulose, it is possible to separate a higher proportion of metals from the water than today. Another benefit is that the separated metals as well as the filter material can be recycled and recovered,” says Aji Mathew.

“We are currently developing some new concepts for nanomembrane  that enables a circularity or upcycling of natural resources, and thus meets currently increasing demands for environmental sustainability.”

The nanomembrane, which was originally developed within an earlier EU project, is now being further improved at Stockholm University, e.g. with the support of The Wallenberg Foundations (WWSC) and within the research program Mistra TerraClean.

Focus on bio-based functional nanomaterials

Aji Mathew has been working on nanocellulose for nearly two decades. Since 2015, she has lead a research group at Stockholm University focusing on bio-based functional nanomaterials, i.e. materials tailor-made to fulfil a specific mechanical, chemical or biological function.

“We start by producing nanocellulose from bio-based raw materials. From these nano-sized building blocks we are able to build functional materials to be used in various areas, such as water purification, catalysis and biomedical applications,” says Aji Mathew.

The great interest in nanocellulose, both within academia and industry, is linked to the material's porous physical structure. Although invisible to the naked eye, nanocellulose based materials is perforated by an incredible number of small cavities – some just a few nanometers in diameter, i.e. a few millionths of a millimeter. The size and position of these cavities can be modified during manufacture, which opens up possibilities for Aji Mathew and others to gradually improve the properties of the material.

Regenerating damaged body parts

Biomedicine is a particular area of interest for Aji Mathew. In the future, she hopes nanocellulose will assist in regenerating damaged body parts.

“The porous structure resembles bone or cartilage. In one of our projects we try to modify the mechanical properties  and pore structure of nanocellulose based materials to mimic body tissue as much as possible.”

By starting with a composite – consisting of nanocellulose and a bio-based polymer – the researchers build a scaffold. Here, the 3D printer has become an increasingly important tool.

“In recent years, we have used a 3D printer to improve the production of the underlying structure. The printer has helped us create a nanocellulose based composite material with the exact properties we want.”

Minimizing environmental impact

New functional materials based on nanocellulose can help minimize environmental impact. In addition, the material is degradable and renewable – Aji Mathew’s research group usually uses residual products from forestry and the food industry. In the long term, Aji Matthew concludes, her research at Stockholm University will contribute to increased sustainability in society.

“Our goal is to produce materials with unique functions that are also bio-based and environmentally sustainable.”

Text: Henrik Lundström