A new book on the treatment of platinum group element pollution offers innovative ways of thinking about treating and recovering these critical raw materials. Piet Lens explains.
Platinum, palladium, rhodium, iridium, osmium and ruthenium – collectively known as the PGEs – shine in jewellery, safeguard human health in biomedical implants, and drive chemical catalysis in applications from car exhaust cleaning to fuel production. Their resilience, rarity and catalytic performance make them irreplaceable in modern industry.
But there’s a downside. These six elements are critical raw materials. Supply chains are fragile, prices are volatile, and environmental risks are mounting. The push for a greener economy brings PGEs into sharper focus: we need them for clean technologies, but the mining and refining that secure them are energy intensive, polluting, and geopolitically fraught. The way forward lies not only in recycling and recovery, but also in rethinking our use of PGEs: how much do we really need; where do we get them from; and how do we use them responsibly?
From rocks to roadways
PGEs occur in magmatic intrusions, placer deposits, as well as in by-products of nickel and copper mining. Today, South Africa, Russia, Zimbabwe, Canada and the USA dominate their production. Their natural durability, high melting points and resistance to corrosion make PGEs indispensable. Platinum and palladium, for instance, are key in catalytic converters that scrub harmful emissions from car exhausts. Iridium, ruthenium and osmium, though less abundant, find their way into catalysts, electronics and aerospace alloys.
Through wear, or at the end of life of devices, PGEs are released into the environment – e.g. into the air through exhaust, into soils via waste dumping and landfilling, and into water through hospital effluents or industrial discharges. So, PGEs accumulate in ecosystems and slip into the food chain. Some are known to trigger allergic reactions, respiratory distress or even DNA damage in humans.
Detecting the invisible
Analysing PGEs is no trivial task. They are often present in trace amounts and at levels as low as parts per trillion. Modern analytical chemistry has risen to the challenge with powerful tools such as inductively coupled plasma mass spectrometry (ICP-MS) and neutron activation analysis, which can detect ultra-low PGE concentrations. Still, accurate measurement requires meticulous preparation. Samples must be pretreated – digested, purified and separated – to isolate PGEs from more common metals. Their unusual chemistry helps. In acidic conditions, PGEs form strong anionic complexes, allowing selective separation. Isotopic spiking techniques further sharpen accuracy, enabling researchers to quantify PGEs and even track their environmental transformations.
From circular promise to sufficiency
For decades, industry has followed a linear model: mine, use, dispose. But urban waste today often contains more PGEs than many primary ores. So, old catalytic converters, spent electronic components and industrial effluents can be the ores of ‘urban mines’. This has spurred interest in a circular economy for PGEs, one in which they are kept in play for as long as possible.
The framework often revolves around the ‘6 Rs’:
‘Reduce’ usage and emissions at the source.
‘Reclaim’/ ‘Remove’ pollutants before they disperse.
‘Reuse’ reclaimed materials directly.
‘Recycle’ PGEs from products at end of life.
‘Recover’ metals from complex waste streams.
‘Rethink’ how society uses PGEs.
The last R, Rethink, points towards circularity not being enough. A parallel idea, sufficiency, reminds us that sustainability is not only about keeping resources circulating – it’s about using less in the first place. Sufficiency asks: ‘Does the world truly need platinum jewellery and, if so, how much?’; ‘Should private cars monopolise precious PGEs or should public transport take precedence?’; ‘Can substitute materials reduce demand without compromising function?’
Framed this way, the challenge of PGEs is not just technical, but also ethical – balancing global consumption against ecological limits and intergenerational equity.
Recovery technologies: from fire to biology
Recovering PGEs from waste is both a scientific quest and a business opportunity. The arsenal of recovery techniques is diverse:
Hydrometallurgy uses aqueous chemistry – leaching, solvent extraction, ion exchange, adsorption – to selectively dissolve and separate PGEs.
Pyrometallurgy harnesses high heat to concentrate and convert ores and residues into PGE-rich products.
Electrometallurgy employs electricity to extract or refine PGEs, often producing high purity outputs.
Biorecovery taps into the ingenuity of microbes and plants. Many bacteria and fungi can bind, accumulate, or reduce PGEs from solutions. Plants that hyperaccumulate metals may be harvested by phytomining, yielding both metals and bioenergy from the biomass.
Each pathway has trade-offs. Hydrometallurgy offers high selectivity and excels at complex wastes, but generates corrosive waste and struggles with chemical residues. Pyrometallurgy is robust and a proven technology, but energy demanding and carbon intensive. Biorecovery is environmentally friendly, but still nascent at scale. The future may lie in hybrid systems – pairing pyro with microbes, chemistry with biology – to maximise efficiency and minimise environmental impact.
From waste to high-tech materials
So, what if recovered PGEs weren’t just recycled into the same old uses, but transformed into advanced new materials? This is already possible. PGEs, when engineered into nanoparticles, exhibit extraordinary optical, electrical and catalytic properties. Their high surface-to-volume ratio means less material is needed for the same effect – a win for economics and the environment.
Nanoparticle applications stretch from cancer therapies to clean energy technologies. Conventional methods to make them – flame pyrolysis, vapour deposition, mechanical milling – are energy intensive. But microbes, again, are stepping in. Certain bacteria can biosynthesise platinum and palladium nanoparticles under mild, green conditions. So, waste streams could become feedstocks for next-generation materials, closing the loop not just in recycling, but also in innovation.
Challenges ahead
Despite major progress, hurdles remain in the supply and recovery of PGEs:
Economic volatility: PGE prices swing wildly, complicating investments in recovery infrastructure.
Technological complexity: separating PGEs from mixed-metal wastes remains costly and
labour-intensive.
Energy and carbon footprints: some recovery methods may undercut sustainability goals.
Health and safety: toxic intermediates like osmium tetroxide or ruthenium tetroxide demand careful handling.
Equity: the Global North consumes far more PGEs than the Global South, yet mining burdens often fall on Southern nations.
The path forward requires innovation and visionary policies – incentives for recycling, standards for waste handling, and equitable frameworks for resource sharing.
A shared responsibility
The story of PGEs mirrors that of our broader resource challenges. A sustainable future for PGEs rests on three pillars:
Science and technology – refining detection, improving recovery and innovating new uses.
Circularity – designing systems that keep PGEs in circulation.
Sufficiency – rethinking ‘enough’ in a resource-constrained world.
If we succeed, PGEs will be a shining example of how society can balance necessity, ingenuity, and responsibility.
Edited by Piet Lens and Mohanakrishnan Logan, Environmental Technologies to Treat Platinum Group Element Pollution: Principles and Engineering is a timely and essential read for those who care about the future of water, resources and sustainability. Platinum Group Elements (PGEs) are not only critical raw materials driving industries, from automotive to electronics and healthcare, but are also emerging pollutants with serious environmental and health implications. This book offers the first comprehensive resource that spans the full journey of PGEs: their biogeochemistry, detection at trace levels and state-of-the-art recovery technologies. It highlights real-world applications, recovery from wastewater, e-waste and spent catalysts, and even synthesis of high-value PGE nanoparticles from secondary sources. More than just a technical manual, the book advances a paradigm shift by blending the circular economy with the principles of sufficiency, urging a drive to balance technological progress with responsible consumption. Authored by leading experts in their field, the book is a must-have reference for academics, industry professionals and policymakers, and aims to shape how we think about the use and reuse of PGEs in a sustainable future.
Available as an Open Access ebook
eISBN: 9781789065084
ISBN: 9781789065077
See: www.iwaponline.com
The author:
Piet Lens is Professor of Environmental Biotechnology at IHE Delft, Netherlands
