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73. Membrane Fouling: Does Microscale Roughness Matter?

Author

Jiang, Zhiwei, Karan, Santanu, and Livingston, Andrew G.

Abstract

The surface of thin-film composite membranes used for reverse osmosis appears to be rough, known as a peak–valley morphology, and this is believed to cause more severe fouling than would occur for a smooth surface. In this study, polyamide nanofilms were made by interfacial polymerization on a sacrificial layer or at a free aqueous/organic interface, manipulating the surface from ultrasmooth (roughness ca. 0.2 nm) to crumpled (roughness ca. 80 nm) morphology. This approach enables the fabrication of morphologically similar polyamide nanofilms on different support membranes, and the control of their initial flux. Membranes with higher initial flux are more severely fouled while their surface roughness (either smooth or rough) is held constant. Moreover, when they are provided with the same initial flux, smooth and rough membranes showed insignificant differences in flux decline upon fouling. This teaches that it is the initial flux, rather than the surface roughness, which is the dominating factor influencing membrane fouling.

Published
2020
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74. Effect of polymer molecular weight on the long-term process stability of crosslinked polybenzimidazole organic solvent nanofiltration (OSN) membranes.

Author

Oxley, Adam and Livingston, Andrew G.

Subjects
*MOLECULAR weights, *CROSSLINKED polymers, *POLYMERS, *ORGANIC solvents, *NANOFILTRATION, *COMPACTING
Abstract

The importance of polymer molecular weight on the long-term performance of polybenzimidazole (PBI) membranes in organic solvents was investigated. PBI membranes were manufactured from two different polymer molecular weights: the standard molecular weight of PBI polymer, used almost universally across literature for organic solvent stable membranes (∼27,000 g mol-1), and an untested ∼ two-fold higher molecular weight (∼60,000 g mol-1). After crosslinking, all PBI membranes were chemically and mechanically stable. However, during continuous long-term pressurised filtration in DMF, the standard molecular weight PBI membranes suffered slow permeance decline over time. This was attributed to rearrangement of the crosslinked polymer chains. Increasing the extent of crosslinking reduced the rate of membrane permeance decline but did not provide a fully process stable membrane. Using a higher molecular weight PBI, and a similar extent of crosslinking, resulted in a membrane with constant permeance and excellent process stability, even during continuous DMF filtration at 120 °C. This was attributed to the increased interchain interactions and entanglement in the high molecular weight polymer, which reduced the rate of chain rearrangement and compaction. This work demonstrates the importance of polymer molecular weight for reducing membrane compaction and providing process stability in organic solvents. [Display omitted] • Membranes were cast from a standard molecular weight (MW) PBI and a high MW PBI. • These membranes were crosslinked with dibromo-p-xylene to different crosslinking extents. • The PBI MW was critically important to the long-term membrane stability. • Only PBI with a high MW and a high crosslinking extent gave membranes stable in DMF. • The standard MW PBI with the same crosslinking extent suffered significant permeance loss. [ABSTRACT FROM AUTHOR]

Published
2024
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75. Novel MBRs for the removal of organic priority pollutants from industrial wastewaters: a review

Author

Yeo, Bibianna JL, Goh, Shuwen, Zhang, Jinsong, Livingston, Andrew G, Fane, Anthony Gordon, School of Civil and Environmental Engineering, and Nanyang Environment and Water Research Institute

Abstract

Organic pollutants which are commonly discharged by the 21 industrial groups identified by the US EPA are regulated under the toxic and priority pollutants list. Novel membrane bioreactor (MBR) systems developed in the last two decades, such as the high-retention MBRs (HR-MBRs) and extractive MBRs (EMBRs), could be applied in the retention/extraction of targeted organics from point-source industrial wastewater to meet stringent regulatory requirements. This paper combines previous reviews and studies conducted on the individual novel MBRs to discuss the potential in applying these technologies in the removal of targeted organic pollutants from industrial wastewater by providing a summary of the technologies and discussing the research gaps that currently hamper their commercialization. Future research should focus on long-term operation with real industrial wastewaters to identify membrane, operational and biodegradation limitations for further optimization. This includes advances in microbiology and the application of novel membranes to boost the biodegradation and removal capabilities of these novel MBR systems. Energy and economic analyses of the MBRs operated at the pilot/demo scale are required to compare their benefits with conventional treatment systems.

Published
2015

89. Microbial dynamics and bioreactor stability in an oil-absorber-bioscrubber system exposed to an alternating sequence of 1,2-dichloroethane and fluorobenzene

Author

Koutinas, Michalis, Baptista, Inês I.R., Meniconi, Andrea, Peeva, Ludmila G., Castro, Paula M. L., and Livingston, Andrew G

Subjects
Hydrolases, Chemical Sciences, Haloalkane dehalogenases, Natural Sciences, Enzymes
Abstract

A study was carried out to investigate the potential for an oil-absorber placed upstream to a bioscrubber configuration to act as buffer for sequentially alternating loads of 1,2-dichloroethane (DCE) and fluorobenzene (FB) in waste gas streams. A bioscrubber system (without the oil-absorber present) was inoculated with strain F11 and Xanthobacter autotrophicus strain GJ10 and was submitted to sequential alternations of the pollutant fed (DCE and FB). The re-introduction of the substrates after each cycle caused system instability. An oil-absorber, utilizing a cost effective and environmentally friendly absorbent (Sunflower Oil), was introduced prior to the bioscrubber to control the negative effects caused by the sequential switches in the feed composition between DCE and FB. The performance of the combined Oil-Absorber-Bioscubber system was stable after the substrates re-introduction following each switch in the feed. The combined Oil-Absorber-Bioscrubber system is a robust technology, offering an effective solution to the biological treatment of waste-gas streams. This is an abstract of a paper presented at the 2006 AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).

Published
2006

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