Redesigning materials for a circular economy

Rare earth metals (REMs) are essential for modern technology applications. Without them our mobile phones, computers and electric vehicles would cease to function.

By 2035 the demand for rare earth metals is expected to grow from today’s figure of 150,000 tonnes to approximately 400,000 tonnes, creating severe pressure on global supply chains.

Current recovery methods of REMs are energy intensive (e.g. high temperatures about 1000^oC) and involve large amounts of corrosive materials. Therefore, a cleaner and simpler way of recovering REMs is urgently needed.

Institute for Frontier Materials (IFM) researchers, together with scientists at Spain’s Tecnalia research and innovation hub have developed an innovative process, using environmentally friendly chemicals, to improve REM recovery methods.

After separating the metals from their end-of-life product, the team, led by Dr Cristina Pozo Gonzalo, use the ionic liquids (salt-based systems) to recover the rare earth metals from the resulting solution using a process of electrodeposition.

This new method for recovering REMs has great potential and minimises the generation of toxic and harmful waste. They are also aiming for a method that can easily be implemented widely across the world.

Dr Pozo-Gonzalo said REMs were among the top critical raw materials identified by the European Commission, Geoscience Australia, and United States Department of Energy.

“The efficient recovery of REMs from recycled materials is becoming increasingly important, given that only about 3 to 7 per cent of REMs are currently recovered from end-products because of technological difficulties,” she said.

“Our work addresses a key knowledge gap in the REM recycling process, and is an important early step towards establishing a clean and sustainable processing route for REMs and alleviating the current pressures on these critical elements.”

The team is working on several projects, focusing on widening the methodology to apply to other valuable metals that are used in energy storage systems.

More information: Water-Facilitated Electrodeposition of Neodymium in a Phosphonium-Based Ionic Liquid. J. Phys Chem. Lett. 2019 (10) 2, 289-294.

IFM researchers have developed a way to add value to cotton gin trash and convert it into a range of potential biodegradable products, such as biodegradable plastic.

Globally, about 26 million tonnes of cotton lint is produced each year with at least 10 per cent of this discarded as waste – known as cotton gin trash (CGT), worth more than $US1million in lost material value.

CGT is a promising source of renewable biomass. When it is broken down, the resulting organic polymer can potentially be converted into a biodegradable material for a range of applications.

The IFM team, led by Dr Maryam Naebe, has developed a viable processing route to add value to CGT and convert it into a range of potential biodegradable products, such as biodegradable plastic.

The team is now looking to apply the process to other organic wastes and fibrous plant materials (such as hemp, almond hulls/shells, wheat straw, wood saw dust or wood shaving).

The opportunity

Imagine if the paint on the Sydney Harbour Bridge could repair itself whenever it was scratched. With the development of self-healing polymer coatings, such a scenario is possible. Pipelines and other infrastructure exposed to harsh environments could repair themselves after environmental damage.

IFM’s solution

IFM researchers, led by Prof Russell Varley, are working with the University of Adelaide and multinational oil and gas company, Petronas, to explore new concepts in autonomous healing of materials specifically targeted towards structures and pipelines that experience extremely harsh conditions and are difficult to repair manually.

Alpaca fleece is a luxurious fibre with excellent softness, great warmth, good lustre and strength. Unlike similar fibres such as wool, alpaca fibres come in 22 natural colours. Global production of alpaca fibre was estimated at 6000 tonnes in 2015 with the price reaching $US16 per kg.

About 20–30 per cent of fibre is lost during shearing and processing. These short and non-spinnable fibres mostly end in landfill, are fed into incinerators or used as low-grade animal feed.

Novel, renewable materials

IFM researchers, led by Dr Maryam Naebe, are investigating the use of these currently wasted fibres as a natural colorant for dyeing acrylic fibres.

Melanin is the pigment primarily responsible for the different colours of alpaca fibres. Conventional extraction of melanin from fibres uses toxic acids and alkalis. The IFM team is using a chemical-free technique to produce the pigments from waste alpaca fibres and then applying the pigments to colour polyacrylonitrile (PAN) fibres in wet spinning. This process could also be used to replace synthetic dyes for dyeing wet spun fibres.

Using our expertise on producing powders from natural fibres, Dr Naebe and her colleagues are developing a chemical free pathway to colour acrylic fibres. The waste alpaca fibres are mechanically milled into a powder, which is applied during fibre spinning to colour the acrylic fibres.

In the conventional dyeing process, acrylic fibres are treated with synthetic dyes. Other chemicals are used to accelerate the process and produce an even result. All these dyes and chemicals also produce massive amounts of waste-water into the environment.

The benefits

• Alpaca fibre producers will get returns from previously unprofitable waste and non-spinnable alpaca fibres
• The amount of water used to produce coloured acrylic fibres is reduced
• The level of chemical pollutants is greatly reduced
• Comfort properties like moisture and wicking of acrylic fibres are enhanced
• When colourant is embedded into the polymer chains during preparation of the dyeing solution, the wash and light fastness of the resultant fibres is increased.

IFM researchers are developing novel methods to upcycle metal alloys and thus address the major issue of waste in the industry.

Titanium has a low density and is well known for its high strength to weight ratio. An estimated 75% of titanium (Ti) metal is used in aerospace

applications, with the remaining 25% used in armour, chemical processing, marine hardware, medical implants, power generation, sporting goods and other applications.

Titanium components account for up to 15% of the total weight of modern aircraft. However, up to 90% of the original titanium (158,000 tons) for aerospace applications is left over as waste chips (swarf) during the entire manufacturing process.

World titanium production in 2017 was 223,000 metric tons. Assuming an average market purchase price of $11.20 per kilogram, the value of wasted titanium from aerospace applications alone is about $165 million. But only a fraction of this scrap metal is recycled. (In 2017, 50,000 tons of scrap metal was recycled by the titanium industry, 11.000 tons by the steel industry, 1.1000 tons by the superalloy industry, and 1,000 by other industries globally).

Existing industry problem

The increasing application of titanium alloys in the aerospace industry leads to huge losses of metals in the form of swarf. In some instances, as much as 50-90% of the part’s weight ends up as swarf. Some investigations have revealed that the machining industry converts about 10% of all the metal produced into machining chips. Most recently, it has been found that in biomedical applications, a typical Ti alloy knee implant component machined from a bar stock results in as much as 80% of material wasted in the form of swarf. Traditional recycling methods for titanium swarf involves the process of re-melting and re-casting, which requires high energy consumption and protective environments. Moreover, swarf is contaminated with coolants and lubricants, or mixed with foreign substances, and the cost of recycling this waste is prohibitive, therefore there exists an opportunity for the development of an innovative process to convert the swarf to bulk titanium or titanium powder for additive manufacturing.

Our research solution

Traditionally, recycling of Ti swarf has been a very expensive process. Hence, developing innovative processes to recycle Ti alloy swarf or even better, to upcycle Ti alloys, i.e. produce the bulk material with better mechanical properties compared to initial Ti alloy, is becoming increasingly important.

IFM researchers led by A/Prof Rimma Lapovok and Dr Ilana Timokhina are investigating the use of titanium swarf as a potential precursor to manufacture bulk ultrafine grains or multicomponent materials with high density and strength.

They are using a novel approach of swarf compaction by severe shear deformation under high hydrostatic pressure to upcycle the waste titanium into high-value materials. The mechanical properties of the compacted swarf are even better than properties of similar processed alloy.

In a second approach, they are also developing a method for using titanium swarf to produce high quality powder (small size, good size distribution, low level of contamination and spherical shape) for additive manufacturing of parts for aerospace and biomedical applications.

Thousands of tonnes of textile waste that would normally go to landfill each year could soon be given new life in cement footpaths, driveways and roads.

A collaboration between IFM researchers, Geelong’s GT Recycling and textile company Godfrey Hirst has resulted in the development of technology for recycling polymer textiles. The fibres, made from recycled carpet, can be used as reinforcing in footpaths, gravel and road surfaces.

Adding less than four per cent of polymer fibres to cement paths resulted in fewer cracks, less rain damage, greater flexibility and improved durability.

The high price of raw materials is a challenge for lithium-ion battery production.

In a novel approach to address this issue, IFM researchers Dr Md Mokhlesur Rahman and Dr Tao Tao, led by Prof Ying (Ian) Chen are using low cost, environmentally friendly waste materials to produce lithium-ion batteries.

In their device, lithiated ilmenite (ilmenite is collected from beach sands) is used as a cathode and silicon recycled from waste solar panels as the battery anode. The development of an energy storage device from waste materials represents a sustainable and environmentally friendly energy expansion.

Denim jeans could be transformed into artificial cartilage for joint reconstruction thanks to advanced textile recycling methods pioneered by IFM researchers.

Dr Nolene Byrne and PhD student Beini Zeng have discovered how to dissolve denim and manipulate the remains into an aerogel – a low density material with a range of uses including cartilage bioscaffolding, water filtration and use as a separator in advanced battery technology. Dr Byrne believes the sticky nature of the denim cellulose solution is likely responsible for the unique aerogel structure that resulted, something ideally suited for use as synthetic cartilage.

An IFM team, led by Professor Xungai Wang, won the H&M Foundation’s 2017 Global Change Award, for their idea to recycle denim by turning used denim into ultrafine particles and then coating or printing the colour particles onto un-dyed new denim.

On average, the life cycle of a pair of denim jeans produces more than 30 kg of CO₂ and uses around 3500 litres of water. “If even a small percentage of jeans are dyed using our new technique, the amount of water saved would have a significant impact on the environment,” said Professor Xungai Wang.

Since receiving the €150,000 award, the team has further developed the technology to create new ‘denim dyed denim’ jeans using the pigment from old, recycled jeans.