An international team led by the University of Bath have produced a new mussel-inspired membrane that allows for the very efficient separation of wastewater components for future reuse. The thin-film nanoporous membrane displays an unprecedented capability to separate salts and other chemical components within wastewater, and could assist a range of industries – such as pharmaceuticals, oil and gas, textiles and food processing – in improving their sustainability while at the same time extracting valuable by-products and chemicals from wastewater.
To help drive net-zero carbon emission, existing wastewater treatment processes urgently require transition from conventional contaminant removal to resource recovery, such as energy, nutrients, biomass and other high-value by-products that are beyond water reclamation by reverse osmosis. A key challenge here is to manage the saline organic-rich waste streams produced by many industrial sectors, and to separate organic and inorganic salts using new separation technology to sustainably recover precious resources.
As reported in the journal Nature Water [Lin et al. Nat. Water (2023) DOI: 10.1038/s44221-023-00113-5], this new membrane’s performance and properties for more sustainable management of water was demonstrated. It is hoped the membrane will be a viable replacement for equivalents used in electrodialysis, the process for treating water by transporting ions through membranes from one solution to another under an electrical current.
The team were inspirated by mussels when developing the coating on the membrane’s surface, which is made from the polymer polyethyleneimine (PEI) and polydopamine (PDA), a compound that mussels excrete and use to adhere to rocks or wood in wet conditions. The stickiness of the coating means the membrane is extremely selective, letting water pass through but blocking other compounds and organic materials. The multi-stage process leads to improved filtration of the water, and a very efficient, low-energy way to separate chemicals individually.
With existing membranes being costly and only managing separation efficiencies of around 90% to 95%, when the PDA/PEI-coated membrane was tested using antibiotics to prove its electro-driven filtration performance, it exhibited excellent recovery efficiency in removing the antibiotics from saltwater solutions – more than 99.3% desalination efficiency and more than 99.1% recovery of the antibiotics while also using less energy at a lower cost. The membrane could also help in lowering carbon emissions by reducing the energy requirement of wastewater treatment.
As co-author Jiuyang Lin points out, “This simple yet effective coating provides long-term stability and guarantees low energy consumption regardless of the wastewater conditions. This is a breakthrough in finding electrodialysis for wastewater treatment involving clever design of membrane, simulation and analysis.” The researchers are now looking for help to commercialise the membrane.
“This simple yet effective coating provides long-term stability and guarantees low energy consumption regardless of the wastewater conditions.”Jiuyang Lin