French and Swiss scientists have used computer simulations to shed light on how organic waste matter can be used to eliminate toxic metals from drinking water.
Pollutant levels in freshwater environments have been steadily increasing in recent years. The leaking of pesticides, chemicals, pharmaceuticals as well as domestic waste into the groundwater supply is a matter of concern, especially in developing countries where safe drinking water has become an invaluable resource. In these regions, water reservoirs are often contaminated by heavy metals such as lead, cadmium or mercury. Their impact on human health is often severely detrimental- lead, for instance, can accrue in bones, teeth and brain tissue and cause chronic poisoning which may lead to a deterioration of the nervous system.
Yet, according to 2017 World Water Development report, only 20% of global wastewater is properly treated before being discharged into natural water bodies.
With populations set to explode, water purification technologies are more important than ever. In the past, prohibitive costs have rendered these innovations, ranging from membrane filtration and activated carbon absorption to electrocoagulation less than feasible for governments looking to implement clean water solutions.
Wanda Andreoni, professor emeritus of physics at the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, plans to change that state of affairs.
Over the last two decades, the physicist has been experimenting with a cheap, low-tech alternative to conventional water purification technologies. By employing biowaste such as fruit peels, coffee grounds or used tea bags, he hopes to remove metal toxins from freshwater.
“There is overwhelming evidence that natural waste materials can efficiently capture heavy metals from water. Nevertheless, related research efforts have been modest,” he said.
A 2018 study conducted in India proved that spent coffee grounds could eliminate lead from contaminated water with a success rate of 90% while a 2020 study in Turkey showed that brewed tea waste could be used to eliminate four different types of heavy metals from a water sample.
Professor Andreoni and her colleagues performed molecular simulations, making use of PRACE supercomputing resources, to shed light on how organic waste matter manages to capture toxins from contaminated water. The team chose to study the molecular structure of hemicellulose, which is comprised of several different sugar chains. Results indicated that that the free energy barriers for hemicellulose to adsorb lead ions from water are negligible. This means that the polysaccharide can easily absorb lead ions from water and makes for an efficient agent to remove heavy metals from water.
The simulations also identified the chemical groups responsible for the efficient heavy metal binding in hemicellulose, which are the sugars’ carboxylate groups (R-COO-) and, to a little lesser extent, their hydroxy groups (R-OH)
Future investigations of the subject matter must entail a mix of lab experiments and computer simulations, according to Professor Andreoni, the goal being to develop new bio-inspired materials and processes that help ensure a clean water supply in developing countries.
“Our conviction that this can be a successful strategy lies in the fact that such collaborative efforts have been successfully applied in a similarly challenging field: drug discovery.”