Finding value in acid mine drainage, mine tailings and waste rocks

Dr Carlito Tabelin hopes novel techniques will reduce the negative environmental impacts of mine wastes, including acid mine drainage, tailings and waste rocks, and attach value to these problematic waste streams.

The research journey that brought Dr Carlito Tabelin to the door of the School of Minerals and Energy Resources Engineering is a fascinating one. Having joined the School in February 2019, he is now on a mission to take one of the biggest problems facing the mining industry – waste disposal – and turn it on its head.Dr Carlito Tabelin

“Among the many environmental challenges faced by the mining and mineral processing industries, acid mine drainage, which refers to the outflow of acidic water from metal or coal mines, is the most serious. It is particularly worrying in NSW where it is having a detrimental impact on streams, wetlands and groundwater supplies,” he says.

According to Tabelin, acid mine drainage often contains valuable metals such as copper, zinc, cobalt and nickel, which, if he can figure out how to efficiently recover them, could not only result in a less toxic environment, but could add considerably more value to the mining operation.

Originally from the Philippines, Tabelin says prior to moving to Australia he was based on the northern island of Hokkaido in Japan. “I did my Master and PhD in Environmental Engineering at Hokkaido University and stayed on to do postdoctoral research. During this time, our lab was involved in a fascinating project to expand the bullet trainline from the mainland of Honshu to Hokkaido,” he explains.

“In the process of digging the tunnels, they were unearthing rocks with unacceptable levels of arsenic, selenium and other toxic elements which were not going to meet Japan’s strict environmental compliance regulations.” 

Tabelin and his colleagues found that the high concentrations were because the basement sedimentary rock had been formed during the Cretaceous period when the area was an ancient ocean. He continued this exploration during his PhD, finding similar issues with the igneous rocks. Then, for his postdoctoral research, he started to focus on remediation.

“It was important to work out how to mitigate the problem because excavated rock is important for building tunnel embankments. We developed a method to recycle the excavated rock which is now being used in Japan, although safety monitoring is still underway,” he continues.

From here, Tabelin moved into mineral processing, resources recycling and investigating some of the toxic waste problems related to mining, such as acid mine drainage. He says there are only two conventional approaches to managing acid mine drainage in current use, and both are unsustainable.

Because of the breadth of mining activities, , the interest of mining companies and the climatic conditions, Australia has huge potential when it comes to the development of sustainable mine waste management systems and strategies.

Dr Carlito Tabelin, Lecturer, Mine Waste Management Engineering, UNSW School of Minerals and Energy Resources Engineering

“One way is to neutralise the acid by adding limestone, but this is not ideal because the problem persists for several millennia, and the treatment method is costly,” he explains.

“Another approach tries to prevent the formation of acid mine drainage. There are several ways to do this, but all have limited success, especially in areas where there is a lot of rain.”

Tabelin says his research at UNSW will draw on all his experience to date in order to develop advanced techniques to mitigate the problem in a two-pronged approach.

“Firstly, I’m interested in looking at ways to preferentially coat pyrite with an unreactive material to prevent the formation of acid mine drainage in the first place. The biggest challenge here is how to target pyrite in mine tailings and waste rocks that contain more than 90% of silicate minerals. This is like finding a needle in a haystack and our approach is to take advantage of the unique way pyrite is dissolved when in contact with water and oxygen. This is a novel idea and needs a lot of further development, but I do believe it’s possible,” he says.

“The other angle I’m taking is to view the heavy metals in the waste as extractable resources.  Copper, zinc, cobalt and nickel are valuable, if we can recover these heavy metals from the waste, then we are adding value to its treatment,” he says.

He explains that one way to recover the metals might be to develop electrochemical-based techniques, for example using bimetallic particles that can act as mini electrolytic cells to recover the dissolved metals by reductive precipitation.

“Because of the breadth of mining activities, the interest of mining companies and the climatic conditions, Australia has huge potential when it comes to the development of sustainable mine waste management systems and strategies,” Tabelin continues.

“I have preliminary experiments and published papers that show the potential of both these methods and I’m now looking for funding and industry partnerships to continue it further.”

More information
If you’d like more information, please contact Carlito Tabelin: c.tabelin@unsw.edu.au

Written by: Penny Jones

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