Researchers have developed a new highly efficient membrane inspired by mussels. Image: University of Bath.
Researchers have developed a new highly efficient membrane inspired by mussels. Image: University of Bath.

Researchers have developed a new kind of membrane that can separate chemicals within wastewater so effectively they can be reused, presenting a new opportunity for industries to improve their sustainability while extracting valuable by-products and chemicals from wastewater.

Created for use in wastewater treatment, the thin-film composite nanoporous membrane (TFC NPM) exhibits an unprecedented capability to separate salts and other chemical components from water, and could lead to more sustainable treatment and management of water in a range of industries.

In a paper in Nature Water, the researchers detail the membrane’s performance and explain how its unique properties, aspects of which are inspired by mussels, could pave the way for more sustainable management of water within industries such as pharmaceuticals, oil and gas, textiles and food processing.

They say the membrane could replace current equivalents used in electrodialysis, a process for treating water by transporting ions through membranes from one solution to another under an electrical current. Existing membranes are expensive and achieve separation efficiencies of 90–95%. The researchers say their TFC NPM can improve on this significantly, achieving efficiencies of more than 99% while using less energy at a lower cost.

Ming Xie, a lecturer in chemical engineering at the University of Bath in the UK and one of the paper’s authors, says the membrane could lead to a shift in thinking around wastewater treatment. “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. This coating is made up of the polymers polyethyleneimine (PEI) and polydopamine (PDA), a compound that 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 (or separate) chemicals individually.

Electrodialysis is a technology that has shown its versatility in several applications: in this case, management of highly saline waste streams. In the electrodialysis process, an electrical potential is used to drive the positive and negative ions making up dissolved salts through separate semipermeable synthetic membranes.

During tests, the researchers used four antibiotics – ceftriaxone sodium, cefotaxime sodium, carbenicillin disodium and ampicillin sodium – to demonstrate the PDA/PEI-coated membrane’s electro-driven filtration performance. The membrane showed an unprecedentedly high recovery efficiency in removing the antibiotics from saltwater solutions – with greater than 99.3% desalination efficiency and greater than 99.1% recovery of the antibiotics. If incorporated in industrial wastewater treatment, the membrane has the capability to carry out electrodialytic fractionation (separation) of various organic/salt mixed solutions more effectively than existing processes.

“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,” said co-author Dong Han Seo from the Korea Institute of Energy Technology.

“This simple-yet-effective coating provides long-term stability and guarantees low energy consumption regardless of the wastewater conditions,” said co-author Jiuyang Lin from the Chinese Academy of Sciences. “This is a breakthrough finding – electrodialysis for wastewater treatment involving clever design of membrane, simulation and analysis.”

This story is adapted from material from the University of Bath, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.