Water separation revolutionized by ultrathin carbon nanomembranes

Project Information

ITS-THIN

Grant agreement ID: 899528

DOI

10.3030/899528

Project closed

EC signature date 26 May 2020

Start date 1 August 2020

End date 31 December 2023

Funded under

• EXCELLENT SCIENCE - Future and Emerging Technologies (FET)

Total cost

€ 2 999 212,50

EU contribution

€ 2 999 212,50

Coordinated by

UNIVERSITAET BIELEFELD
Germany

Periodic Reporting for period 2 - ITS-THIN (Water separation revolutionized by ultrathin carbon nanomembranes)

Reporting period: 2021-08-01 to 2023-12-31

Summary of the context and overall objectives of the project

ITS-THIN achieved important steps in the development of novel ultrathin membranes for the use in water filtration applications. It embodies the vision of a disruptive technology: Ultrathin Carbon Nanomembranes (CNMs) of ~1 nm thickness enabling an unprecedented efficient water separation technology inspired by the highly efficient biological filtration processes found in nature. The CNM sub-nm functional pores enable efficient removal of small molecules and ions from water streams.
Due to the extremely high areal pore number density (1 sub-nm pore per square nanometer) constituting up to 40% of the membrane, CNMs enable a hitherto non-attainable separation efficiency compared to existing membrane technology. CNMs are mechanically stable and can withstand harsh environments. In laboratory scale experiments, CNMs showed an extraordinarily high rejection of organic molecules, anions and cations, with a concomitant high-water flux [1-2].
ITS-THIN developed a CNM-composite membrane with a nanometer-thin CNM as active layer. In this composite membrane, the CNM is freestanding over micrometer-sized pores in the support. The corresponding production process was scaled in a roll-to-roll process to yield 25 mm wide ribbons with a length of 1 up to 100 m, which could be welded into tubular membranes. These were fitted into first modules with membrane areas of above 50 cm2. Therewith, the active membrane area is increased by a factor of about 10 million in comparison to previously characterized micron-sized CNMs [1-2]. However, the occurrence of defects in the ultrathin CNMs of large sizes diminishes the rejection properties substantially. In the last stage of the project, an approach to heal defects in CNMs was identified and implemented in the production of CNMs with membrane sizes of up to 3 cm2. Therewith, a promising high ion rejection in osmotic tests was achieved. These late results are not described in the ITS-THIN deliverable reports but they are in the process of being published in the journal “ACS Applied Materials & Interfaces” under the title “Defect-Healed Carbon Nanomembranes for Enhanced Salt Separation: Scalable Synthesis and Performance”. Note that the results in all ITS-THIN deliverable reports were obtained without this defect healing approach. The obvious next step of applying this method to CNM-composites of larger sizes it planned but it was not implemented within the ITS-THIN project.

[1] Y. Yang et al., ACS Nano 12, 4695 (2018).
[2] Y. Yang et al., Adv. Mater. 32, 1907850 (2020).

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A substantial part of the works performed aimed at the fundamental understanding of the exceptional properties of CNM membranes. This involved two complementary aspects. First, a theoretical and computational modelling of the transport properties of water and ions across CNM nanopores was performed and allowed to identify the key aspects underlying the resulting properties of CNMs. This approach led to a second step of fundamental understanding, pointing to the advanced properties of CNM as Thin Film Composite (TFC) membranes (= CNM-composites), in the form of non-linear (diode-like) water transport across the CNMs.
A number of different types of CNMs were considered as possible active layers in CNM-composites for hydraulic pressure-driven and osmosis-driven separations. Complementary transport measurements were performed by applying pressure differences, concentration gradients as well as electric fields.
We have developed a concept for CNM-composite membranes based on a CNM as an active layer supported by a track-etched polyethylene terephthalate (PET) film with open pores.
A benchtop roll-to-roll process for 25 mm wide ribbons was built to demonstrate scalable production methods. The ribbons have been welded to form tubular membranes with a diameter of approx. 8 mm. However, it was not yet possible to produce well-performing membranes with the laboratory-scale roll-to-roll setup in contrast to earlier hand-made membranes in the laboratory. The focus has been rather on the principal demonstration of production methods and to identify challenges in their scale-up.
Mechanical characterization of transferred CNMs on supports and of CNM-composite membranes displayed exceptional mechanical behavior with constant and non-degraded long-term operation, making them suitable for real-life applications.
The focus initially was on coupon testing of CNM-composites in FO experiments, utilizing different salts as draw solutions. The stability and durability of CNM-composites under various environmental conditions were assessed and recommendations for improving the stability and longevity of CNM-composites were provided. Anti-biofouling experiments were performed with synthetic bacteria solution as feed solution in a forward osmosis membrane cell. UV photocatalysis to remove biofouling from commercial FO membrane surfaces was also applied.
ITS-THIN Partner BlueTec made modules with tubular membranes by welding 25 mm wide ribbons and potting them into modules using epoxy resin.
The aim was to demonstrate how CNM-based separation is superior to existing UPW and CC technologies. The production and testing of CNM-composite membrane ribbons have provided invaluable insights into the intricacies of optimizing tubular membrane module manufacturing.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The world runs on water. By 2050, the world population will reach more than 8 billion people, who will need 60% more food and 55% more water [1]. These numbers demonstrate that water management is one of mankind’s biggest global challenges. Hence, all water related innovation in ITS-THIN may spread outreach into other branches of water treatment. Although the ITS-THIN water filtration platform is intended to improve water polishing for the generation of ultrapure water and high-purity FO-driven cold concentration applications for the food & beverage as well as pharma industry, it can be later adapted to other uses e.g for industrial water purification processes, the treatment of wastewater and brackish water or the recovery of valuable resources from waste water streams (“zero liquid discharge”). This is in alignment with the UN sustainable development goals [2] SDG6 “Ensure availability and sustainable management of water and sanitation for all” and SDG 12 “Ensure sustainable consumption and production patterns” and the second priority objective of the 7th Environment Action Programme (EAP) of the EU “to turn the Union into a resource-efficient, green and competitive low-carbon economy” [3]. The energy-efficient water separation developments created by ITS-THIN directly support the EAP’s vision: “In 2050, we live well, within the planet’s ecological limits. Our prosperity and healthy environment stem from an innovative, circular economy where nothing is wasted and where natural resources are managed sustainably, and biodiversity is protected, valued and restored in ways that enhance our society’s resilience. Our low-carbon growth has long been decoupled from resource use, setting the pace for a safe and sustainable global society.” [3]

[1] The United Nations world water development report 2015: water for a sustainable world, 122p, ISBN:978-92-3-100071-3, 978-92-3-100099-7 (ePub).
[2] United Nations “Transforming our World: The 2030 Agenda for Sustainable Development” A/RES/70/1 (2015).
[3] Official Journal of the European Union L 354, 371 - 200 (28.12.2013).

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