Graduating COEMinerals PhD candidate Yuxuan Luo, and his work to improve mineral processing, has been profiled by the University of Melbourne:

Improving water recovery in mineral extraction through a PhD

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Improving water recovery in mineral extraction through a PhD

Life as a graduate researcher: Yuxuan Luo

Yuxuan Luo is improving mineral processing waste dewatering through a PhD in chemical engineering at the University of Melbourne. An industry advisor and working with a national research centre have helped him apply an industry perspective. After graduating, he’ll be looking for roles as a product engineer.

From smartphones to solar panels, all our technologies rely on minerals extracted from ores.

Researchers at the University of Melbourne are working on making the mineral extraction process and waste storage more sustainable.

“Mineral dewatering is a process to recover water used during mineral separation,” says University of Melbourne PhD in Engineering candidate Yuxuan Luo.

Tailings – the waste materials resulting from mineral separation – often have a high water content. Tailings are commonly stored in tailings dams. The moisture content of the waste makes tailings storage very challenging.

“In 2019 in Brazil there was a tailings dam collapse and all the tailings rushed down to the village. A lot of people died,” Yuxuan says.

Dewatering helps make tailings less liquid. This makes the tailings more geotechnically stable and less challenging to store. Dewatering also improves the sustainability of mineral extraction, because the recovered water can feed back into the mineral recovery process.

Pelleting flocculation saves time and money in mineral dewatering

“Today, there are more tailings for each tonne of mineral produced than there used to be. Over the years, as ores become depleted, the grade – the amount of mineral contained in the ore – is reducing,” Yuxuan says.

Mineral extraction waste is often a mixture of solids, water and chemicals. Smaller particles are more difficult to separate from these suspensions, requiring more time and chemicals compared to larger particles.

Ores also now have more clay content, which affects dewatering. All of this can make mineral processing less efficient and more expensive today than in the past.

Yuxuan’s research focuses on improving current dewatering methods that turn the waste into solid pellets.

His PhD research took place over three stages:

1. Measuring the effects of clay in mineral dewatering and building a model to predict it
2. Demonstrating how an oil can increase the robustness of aggregates in a mineral suspension to make them suitable for creating solid pellets
3. Developing a novel device that can produce centimetre-sized pellets from micron-sized solids in liquid suspensions.

This process reduces dewatering time and the amount of chemicals – flocculants – needed.

“We can also use this new device to produce more precise materials for other downstream dewatering processes,” Yuxuan says.

​“We proved that, by pelletising the waste, we improve the dewaterability of the suspension – in some cases by orders of magnitude”: Yuxuan Luo

Building researcher and industry networks through a PhD

Yuxuan is a member of the Australian Research Council Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals (COEMinerals).

The centre recently supported PhD researchers to visit the Fosterville gold mine and Rio Tinto’s Bundoora research centre. The visits helped Yuxuan and his cohort better understand on-site processes and the scale of the problems they’re trying to solve.

“We always talk about how the resources industry deals with huge throughputs and enormous machinery. But you can’t imagine how big the device they use is until you’re actually there to see it,” Yuxuan says.

Rio Tinto’s Dr Mark Coghill is an honorary researcher in Yuxuan’s research group. Dr Coghill helps Yuxuan consider his research from an industry perspective.

Yuxuan has also connected with other University of Melbourne researchers through shared infrastructure.

“We get the chance to learn about research in other departments,” he says.

A PhD can be an opportunity to build friendships

Yuxuan has also connected with other domestic and international researchers through his PhD. His supervisor, Associate Professor Anthony Stickland, organised his research group to visit Europe for an international conference. The group spent a week in the UK, visiting the University of Cambridge and the University of Leeds.

“And the week after, we went to Germany for an international conference.”

The group spent a week in Cologne.

“We were lucky enough that the week we spent in Cologne was during the carnival of the year. In the morning we were at a conference wearing suits with ties. After conference we dressed up and we went to the carnivals,” Yuxuan says.

Graduate researchers in Yuxuan’s group help each other out when needed.

We can get easy access to the instruments in other departments or other schools. For example, I used to go to Bio21 to use their microscopes.Yuxuan Luo

Sometimes I need other people to help me. When there’s another graduate researcher free, they will come and help me for an hour or two, and in return I will also help them in their work, and maybe buy them a bubble tea or something to say thank you.Yuxuan Luo

The research group keeps track of group members’ birthdays and often have an affordable lunch together at Graduate House.

Graduate House is a membership association and residential college for postgraduate students, graduate researchers and international researchers.

“Most of the people living at Graduate House are overseas researchers. We can meet people from different fields, different countries or different cultures,” Yuxuan says.

An applied research PhD can create industry opportunities

Yuxuan’s three-and-a-half-year PhD scholarship ended in 2024. To close the gap between finishing his experiments and submitting his thesis, his supervisor, Associate Professor Stickland, continues paying Yuxuan a salary thanks to Yuxuan’s ongoing role with COEMinerals.

After Yuxuan submits his thesis, he plans to look for a job in industry. Having entered Australia from Singapore as an international student, he chose Melbourne as the city to complete his bachelors, masters and PhD because of its chemical and pharmaceutical industries.

“The reason that I chose the University of Melbourne is because it’s a top university in the world,” he says.

His research experience in chemical engineering ignited a passion for applied chemistry.

“I’m really enjoying making a product using the knowledge that I have. Next, I’d love to upskill or work as a product engineer.”