With input from researchers at Bath University, the thin-film composite nanoporous membrane is claimed to present a new opportunity for industries to improve sustainability, while extracting valuable by-products from wastewater. The team, including academics from China, South Korea, Singapore, Australia and Belgium, have detailed their work in Nature Water.
They said the membrane could replace current equivalents used in electrodialysis, where existing membranes are expensive and can achieve separation efficiencies of 90-95 per cent. The team said the new TFC NPM takes efficiencies to over 99 per cent while using less energy.
Dr Ming Xie, lecturer in Chemical Engineering at Bath University, said: “Traditionally, many industries have regarded the wastewater they create as a trade waste that is a necessary cost of business. Technologies such as the membrane we have created can help us take steps toward lowering carbon emissions by reducing the energy requirement of wastewater treatment, while finding ways to efficiently separate the components in it such as chemicals, salts, energy, biomass and nutrients, before reusing them as high-value by-products.”
The researchers took inspiration from mussels when designing the coating on the membrane surface, which is made up of the polymer polyethyleneimine (PEI) and polydopamine (PDA), a compound which mussels excrete and use to stick to rocks or wood in wet conditions. The coating’s stickiness makes the membrane highly selective, allowing water to pass through but blocking other compounds and organic materials. This multi-stage process results in improved filtration of the water, and a highly efficient, low-energy way to fractionate chemicals individually.
Electrodialysis is a technology that has shown its adaptability to several applications, in this case, management of highly saline waste streams. In the electrodialysis process, electrical potential is used to drive the positive and negative ions of dissolved salts through separate semipermeable synthetic membrane.
During tests, the researchers used four antibiotics – ceftriaxone sodium, cefotaxime sodium, carbenicillin disodium and ampicillin sodium – to prove the PDA/PEI-coated membrane’s electro-driven filtration performance. According to the team, the membrane showed unprecedentedly high recovery efficiency in removing the antibiotics from saltwater solutions (water and NaCl sodium chloride) – with more than 99.3 per cent desalination efficiency and more than 99.1 per cent recovery of the antibiotics. If incorporated in industrial wastewater treatment, the membrane has the capability to carry out highly effective electrodialytic fractionation of various organic/NaCl mixed solutions, more effectively than standard existing processes.
Co-author, Dr Dong Han Seo from the Department of Energy Engineering, Korea Institute of Energy Technology, said: “This work demonstrates the state-of-the-art electrodialysis to address the grand challenge in the pharmaceutical industry to bio-based wastewater treatment, to enable effective recovery of the high value chemicals while obtaining reusable water in the other end using a low energy consumption.”
The authors are now looking to commercialise the membrane.
The project was supported by funding from a Royal Society International Exchange grant, a Royal Academy of Engineering Industrial Fellowship and the Erasmus Staff Mobility Fund.
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Good comment. I think these reports are different from many others , in that they were prepared outside the government and the issues, they raised, of...