A team of international researchers, including Dr Rich Crane from the Camborne School of Mines, University of Exeter, have developed a new method to extract metals, such as copper, from their parent ore body.

The research team have provided a proof of concept for the application of an electric field to control the movement of an acid within a low permeability copper-bearing ore deposit to selectively dissolve and recover the metal in situ.

This is in contrast to the conventional approach for the mining of such deposits where the material must be physically excavated, which requires removal of both overburden and any impurities within the ore (known as gangue material).

The researchers believe the new technique has the potential to transform the mining industry, because it has the capability to dissolve metals from a wide range of ore deposits that were previously considered inaccessible.

Furthermore, due to the non-invasive nature of the extraction, the research team are hopeful that the study will help usher in a more sustainable future for the industry.

This is urgently required now in order to provide the plethora of metals required to deliver green technology, such as renewable energy infrastructure and electrified vehicles, whilst limiting any potential environmental damage associated with the mining of such vitally important metals.

The study was recently published in Science Advances.

Dr Rich Crane from the Camborne School of Mines, University of Exeter, and co-author of the study, said: “This new approach, analogous to “key-hole surgery,” has the potential to provide a more sustainable future for the mining industry, by enabling the recovery of metals, such as copper, which are urgently needed for our global transition to a new Green Economy, whilst avoiding unwanted environmental disturbance and energy consumption.”

The central principle behind most modern mining techniques has not fundamentally changed since their original conception, which marked the beginning of the Bronze Age: metals are recovered from the subsurface via physical excavation, i.e., the construction of tunnels to gain access to the deposits, or by creating “open cast” mines.

This technique demands large volumes of surface soil, overburden and gangue material to also be excavated, which can contain millions of tonnes of material — and can also lead to habitat destruction.

In this new publication, experts from the University of Western Australia, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), the Technical University of Denmark and the University of Exeter, have demonstrated that a targeted electric field can be used to dissolve and then recover copper in situ from the ore — avoiding any requirement to physically excavate the material.

This new technology comprises the construction (drilling) of electrodes directly into an ore body. An electric current is then applied which can result in the transport of electrically charged metal ions, such as copper, through the rock via a process called electromigration.

The research team have now provided a Proof of Concept for this new technology at laboratory scale, which has also been verified using computer modelling. They are confident that the idea will work beyond the laboratory-scale.

Story Source:

Materials provided by University of Exeter. Note: Content may be edited for style and length.

The lifespan of the respiratory droplet dictates how likely a surface is to spread a virus. While 99.9% of the droplet’s liquid content evaporates within a few minutes, a residual thin film that allows the virus to survive can be left behind.

This raises the question: Is it possible to design surfaces to reduce the survival time of viruses, including the coronavirus that causes COVID-19? In Physics of Fluids, from AIP Publishing, IIT Bombay researchers present their work exploring how the evaporation rate of residual thin films can be accelerated by tuning surfaces’ wettability and creating geometric microtextures on them.

An optimally designed surface will make a viral load decay rapidly, rendering it less likely to contribute to the spread of viruses.

“In terms of physics, the solid-liquid interfacial energy is enhanced by a combination of our proposed surface engineering and augmenting the disjoining pressure within the residual thin film, which will speed drying of the thin film,” said Sanghamitro Chatterjee, lead author and a postdoctoral fellow in the mechanical engineering department.

The researchers were surprised to discover that the combination of a surface’s wettability and its physical texture determine its antiviral properties.

“Continuously tailoring any one of these parameters wouldn’t achieve the best results,” said Amit Agrawal, a co-author. “The most conductive antiviral effect lies within an optimized range of both wettability and texture.”

While previous studies reported antibacterial effects by designing superhydrophobic (repels water) surfaces, their work indicates antiviral surface design can be achieved by surface hydrophilicity (attracts water).

“Our present work demonstrates that designing anti-COVID-19 surfaces is possible,” said Janini Murallidharan, a co-author. “We also propose a design methodology and provide parameters needed to engineer surfaces with the shortest virus survival times.”

The researchers discovered that surfaces with taller and closely packed pillars, with a contact angle of around 60 degrees, show the strongest antiviral effect or shortest drying time.

This work paves the way for fabricating antiviral surfaces that will be useful in designing hospital equipment, medical or pathology equipment, as well as frequently touched surfaces, like door handles, smartphone screens, or surfaces within areas prone to outbreaks.

“In the future, our model can readily be extended to respiratory diseases like influenza A, which spread through fomite transmission,” said Rajneesh Bhardwaj, a co-author. “Since we analyzed antiviral effects by a generic model independent of the specific geometry of texture, it’s possible to fabricate any geometric structures based on different fabrication techniques — focused ion beams or chemical etching — to achieve the same outcome.”

Story Source:

Materials provided by American Institute of Physics. Note: Content may be edited for style and length.

Monitoring from 1998-2019 shows loggerhead and green turtle nest numbers increased dramatically, though hawksbill turtle nest numbers remain low.

In the first counts in 1998-99, just 39 sea turtle nests were found in total on the three islands. By 2019, the figure was 675.

Captive breeding of green turtles and inactivity of a traditional turtle fishery due to tightening of restrictions in 2008 contributed to this — but populations remain far below historical levels and still face threats including illegal hunting.

The study was carried out by the Cayman Islands Department of Environment and the University of Exeter.

“Our findings demonstrate a remarkable recovery for sea turtle populations that were once thought to be locally extinct,” said Dr Janice Blumenthal, of the Cayman Islands Department of Environment.

“A combination of factors is thought to have led to this conservation success story.

“It is likely that a captive breeding operation by the Cayman Turtle Farm (now the Cayman Turtle Centre) drove the increase in Grand Cayman’s green turtle population in the early years of monitoring.

“For loggerhead turtles, the most important factor was the restrictions placed on the legal turtle fishery in 2008.”

Dr Jane Hardwick, also of the Cayman Islands Department of Environment, added: “For both species, the recovery was assisted by protection efforts by the Cayman Islands Department of Environment on nesting beaches, including patrols by conservation officers to reduce illegal hunting.

“However, our study finds that illegal take is an ongoing threat, with a minimum of 24 turtles taken from 2015-19, many of which were nesting females.

“Artificial lighting on nesting beaches, which can direct hatchlings away from the sea, increased over the period of our study.

“Additionally, as highly migratory endangered species, sea turtles are influenced by threats and conservation efforts outside of the Cayman Islands, showing a need for international co-operation in sea turtle management.”

Historically, the Cayman Islands had among the world’s largest sea turtle nesting populations, with turtles numbering in the millions. By the early 1800s, the populations had collapsed due to human overexploitation.

The new study shows that, despite reaching critically low levels, nesting populations of green and loggerhead turtles have recovered significantly.

Hawksbill turtle nest numbers have not increased in tandem with loggerhead and green turtles — with a maximum of 13 hawksbill nests recorded in a single monitoring season.

Information on turtle nests is being used by the Cayman Islands authorities to target management efforts.

This includes “turtle-friendly lighting” initiatives, and a greater level of habitat protection for key areas has been proposed under the National Conservation Law of the Cayman Islands.

Professor Brendan Godley, of the University of Exeter, said: “I was fortunate to have been involved in establishing the turtle monitoring programme with the Department of Environment in the Cayman Islands back in 1998 and it is fantastic to see how protection and awareness has resulted in an increase in nesting turtles.

“The wonderful team and leadership of the Department of Environment have been instrumental in driving the monitoring and conservation.”

Department of Environment Director Gina Ebanks-Petrie said: “We are extremely grateful to the many volunteers, interns, property owners, businesses, organisations and members of the public who have assisted with sea turtle conservation efforts over the past two decades.

“Sea turtles are a national symbol of the Cayman Islands and our community has come together to demonstrate our commitment to their protection. This research gives us essential information for strategically targeted management efforts to secure future survival of these populations.”